JP2001239374A - Resistance welding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resistance welding machine capable of welding a bottom plate or the like to a side frame without hindrance by the turning-in part of the inside of the side frame in a sheet metal work such as a box. SOLUTION: In the resistance welding machine in which members 1, 5 to be welded are pressed and subjected to electric current between the upper and lower welding tips 22, 31, an offset part 23 deviated from the central axis is formed in a welding holder 21 holding the upper welding tip 22 and further, respective welding tips 22, 31 are rotated around these central axes.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resistance welding machine, and more particularly, to a work or a workpiece such as a box or the like whose upper opening is folded inward and trimmed, and the periphery of the opening is formed. The present invention relates to a resistance welding machine capable of smoothly and smoothly mounting a bottom plate or the like to a side frame of a box by a resistance welding without being disturbed by an inner bent portion. In the following, the present invention will be described mainly with respect to an example in which a bottom plate is attached to a side frame having an inside folded portion which is folded inward. However, the present invention can be applied to other than such an example, It is most suitable for welding workpieces with obstacles above.

[0002]

2. Description of the Related Art Generally, in metalworking, a metal plate to be welded (that is, a material to be welded) is superimposed and energized by a pair of upper and lower electrodes, and the resistance heat generated by the energization is used as a heat source for heating. A method of applying a predetermined pressure to weld a lap joint of a material to be welded is used. This method is referred to as resistance welding, especially lap resistance welding, and is the most widely used welding method together with arc welding, and is widely used as a joining means in sheet metal processing, especially in manufacturing metal boxes and the like. I have.

[0003] The heat source used in this resistance welding is resistance heat generated in a workpiece or a material itself. When resistance heat is the heat source, the temperature of the heat source is not always constant, and the temperature depends on welding factors such as welding current, physical properties of the material to be welded, contact resistance of overlapped joints, etc. It is also a drawback.

[0004] On the other hand, in spite of these disadvantages, resistance welding does not require a welding rod or flux unlike arc welding and the like, the heating portion is limited to a local area, and welding is difficult. It has the advantage of not damaging the base material itself.

[0005] Taking advantage of this advantage, resistance welding is widely used as a joining means for sheet metal processing of automobile frames, steel furniture, home electric appliances and the like. However, even if a commonly used resistance welding machine is applied to the production of metal boxes that make up the majority of sheet metal processing, welding of specially shaped boxes, such as metal boxes with inward folds, is not possible. It is extremely difficult to do.

[0006] A welding machine used for resistance welding of the lap joint is called a resistance welding machine. In the resistance welding machine, the upper and lower electrodes sandwiching the material to be welded are formed as spot-like spot electrodes, so that the current and the current are applied. A spot welder is a welder that has concentrated pressure. The spot welding machine welds the material to be welded by energizing and heating a pair of spot electrodes from above and below, and this welding forms a spot-like nugget. This is the welding machine used.

That is, a spot welding machine is generally provided with an upper electrode and a lower electrode, and a predetermined pressing force is applied to an upper electrode of these electrodes by an electrode pressing device such as a pressing cylinder. The electrode pressing device is supported by a mechanical member.

[0008] Among the spot welding machines of this structure, the stationary spot welding machine is provided with the above-mentioned components in one piece, and when welding is performed, for example, a welded portion such as a side frame or a bottom plate is welded. The material is moved to the welding machine and welded to make a metal box.

On the other hand, among metal boxes to be welded, there are large products such as steel furniture, storage boxes such as safe boxes, housings for home electric appliances, and the like, and large products are difficult to move. Therefore, for this welding, a welding machine having the following structure is used instead of the stationary spot welding machine.

In this welding machine, an upper electrode and a pressurizing portion of the electrode are integrally formed as a so-called welding gun, and a flexible cable is provided between the welding gun and a separated welding power source.
This is a welding machine connected by a bull. With this welding machine, the welding gun itself is portable and can move freely, so that the welding gun can be moved and welded without moving the material to be welded, which is suitable for welding large products.

Among the welding machines using such a welding gun, the upper electrode is constituted by a welding gun having a welding tip attached to the lower end, and the lower electrode corresponding to the upper electrode is constituted by a conductive plate such as a copper plate. A welding machine has also been proposed. With this welding machine, a large workpiece can be pressurized and energized with a welding gun on a current-carrying plate that can also be used as a work table.

However, in a welding machine having such a welding gun and a current-carrying plate such as a copper plate, since the welding gun is not connected to the pressurizing portion of the electrode, the pressing force depends on the labor of the operator. In addition to being unable to apply high pressure, it is extremely labor intensive and is not suitable for welding that requires mass production to some extent.

For this reason, even in a welding machine having a welding gun and an energizing plate such as a copper plate, a pressurizing portion such as an air cylinder is attached to the upper end of the welding gun, and the welding gun is pressed downward by the air cylinder. A welding machine capable of welding by applying a pressing force has been proposed. However, this welding machine has a structure in which a heavy object such as an air cylinder is attached to a welding gun, and the welding gun and the air cylinder are supported by a strong support member. .
With this type of welding machine, the welding gun cannot be moved freely by manual power on the current-carrying plate, so that the workpiece is moved on the current-carrying plate and welded. Only suitable for welding.

That is, when the bottom plate is mounted on the side frame having the inner fold by the welding machine, the inner gun may have the inner fold above the weld, so that the welding gun is pressed downward by the air cylinder. Even if an attempt is made to apply a pressing force to the welded portion, the press-in welding cannot be performed because the inner folded portion is in the way.

For example, as shown in FIG. 4, a metal box 3 in which a bottom plate 2 is attached to a side frame 1 having an inner folding portion is used as a safe, a storage box, and a housing for home appliances. The upper surface of the metal box 3 is open, and an inner bent portion 4 is provided around the open portion. With this structure, pressure welding cannot be performed on the welding of the series of welds 5 immediately below the inner fold 4 because the inner fold 4 hinders the elevation of the welding gun.

More specifically, when the metal box 3 shown in FIG. 4 is welded by the welding machine 6 shown in FIG. 5, the flange 1a of the side frame 1 is connected between the lower electrode 7 and the welding gun 8. The bottom plate 2 is scissors resistance welded. An air-cylinder 9 is attached to the upper end of the welding gun 8, and at the time of welding, the welding gun must be pressed downward by the air-cylinder 9 to press each welding portion 5 in which the flange portion 1a and the bottom plate 2 are overlapped. Must.

However, inside the side frame 1, an inner folded portion 4 is provided.
Since the protrusions (see FIG. 4) protrude, the inner folded portions 4 hinder the welding of the respective welded portions 5, and the welding gun cannot be lowered to the welded portion 5 for welding. In particular,
In order to weld such a welded portion 5, welding is performed by fixing the lower electrode using a metal plate from the inside and pressing the upper electrode from the outside. However, such welding from the outside is troublesome in preparation work, and a mark is left on the pressed portion from the outside, which is not preferable.

[0018]

SUMMARY OF THE INVENTION The present invention aims at solving the above-mentioned drawbacks. Specifically, the present invention relates to a welded portion immediately below an inner folded portion, such as when manufacturing a box folded inside. We also propose a resistance welding machine that can easily weld by pressing from the inside.

[0019]

That is, a resistance welding machine according to the present invention is a resistance welding machine for performing resistance welding by pressurizing and energizing a material to be welded between an upper electrode and a lower electrode. It comprises a so-called welding gun with a welding tip attached to the lower end, and in this welding gun, a lower end of the welding holder is provided with an offset portion offset by a predetermined distance from the center axis thereof.

A rotating device is provided for rotating at least the upper electrode of the upper and lower electrodes about their respective central axes.

Further, when these rotating devices are constituted by servo motors, and when the rotating devices are attached to the upper and lower electrodes, these rotating devices are constituted as servo motors.
Both servomotors are synchronized.

A welding device having a welding tip at a lower end is supported at one end of a support arm, and a pressurizing device for applying a downward pressing force to the welding holder is attached to the other end of the support arm. The pressurizing device pushes down the welding holder to apply welding force to the welding tip to perform welding.

The configuration and operation of these means will now be described in more detail with reference to the illustrated embodiment.

FIG. 1 is an explanatory view of a part of a welding machine according to one embodiment of the present invention.

FIG. 2 is an explanatory view of an example of a welding gun in the welding machine of FIG.

FIG. 3 is an explanatory view of a welding mode by the welding machine of FIG.

FIG. 4 is an explanatory view perspectively showing a manufacturing process of an example of the metal box.

FIG. 5 is a diagram showing one principle of a conventional resistance welding machine.

First, in FIG. 1, FIG. 2 and FIG.
As in FIG. 4, reference numeral 1 denotes a side frame having an inner folding part 4,
2 is a bottom plate attached to the side frame 1, 3 is a metal box made by attaching the bottom plate 2 to the side frame 1, 4 is an inner fold, and a weld 5 to be welded is formed immediately below the inner fold 4. ,
The welded portion 5 is formed in a line shape over the entire circumference.

When manufacturing the metal box 3 having such a structure, the bottom plate 2 is superimposed on the inwardly protruding flange 1a on the lower surface of the side frame 1, and the overlapped portion is welded to the structure shown in FIG. It is sandwiched between a welding gun 20 (upper electrode) and a cylindrical base 30 (lower electrode) in the machine 10 and welded. The welding gun 20 forming the upper electrode includes a welding holder 21 and a welding tip 22. The welding tip 22 is attached to the lower end surface of the welding holder 21, and the welding tip 31 is also attached to the cylindrical base 30. , 31 and press weld the flange portion 1a and the bottom plate 2 together.

In this welding gun 20, the welding holder 2
1 is bent to form an offset portion 23, and the welding tip 22 attached to the tip of the offset portion 23 is offset from the center axis of the welding gun 20 and extends inside the side frame 1 to just below the inner folding portion 4. 22 can enter. When the welding gun 20 is configured in this manner, the welding holder 21 is rotated about its axis, and the welding tip 31 attached to the cylindrical plate 30 is correspondingly rotated, a series of welds 5 is formed over the entire circumference. Weldable.

That is, as shown in FIG.
Numeral 0 denotes a welding holder 21 and a welding tip 22, to which the welding tip 22 is detachably attached. The lower portion of the welding holder 21 is bent to form an offset portion 23. For this reason, the welding tip 22 can enter just under the inner bent part 4 by the offset distance. For this reason, when the offset portion 23 of the welding holder 21 is rotated by 90 ° for welding, the welded portion 3 can be welded over the entire circumference. In this case, if the offset amount D is too large, the welding gun 2
The reaction force at the time of pressurization of the welding tip 22 becomes large with respect to the vertical pressing force acting along the axial direction of 0,
Not preferred.

The lower end of the welding holder 21 is offset if the welding tip 22 is offset from the center axis of the welding holder 21 by the offset amount D and the welding tip 22 can be inserted into the housing 1. The object of the present invention can be achieved.

Therefore, as shown in FIG. 1, the lower end of the welding holder 21 can be bent obliquely to offset the tip, but if it is offset in this manner, the offset amount D cannot be made so large. For this purpose, an inverted conical body, an inverted truncated cone, a disk, or a columnar base (not shown) is attached to the lower end of the welding holder 21, and a welding tip 22 is attached to the periphery of the base. The offset amount D can be increased.

A drive motor 40 is provided on the upper end of the welding gun 20 as a rotating device for rotating the welding gun 20.
(See FIG. 2). On the other hand, the driving motor 5 is used as a rotating device for rotating the cylindrical base 30 corresponding to the driving motor 40.
0 (see FIG. 2). These drive motors 40, 50
As a result, the welding gun 20 and the cylindrical plate 30 are rotated in synchronization.

The driving motors 40, 5 rotating in synchronization with each other
0 can be configured in any manner as long as a predetermined amount of rotation can be given accurately, but it is preferable to configure a servo motor. That is, the servo motor can be controlled to a constant rotation speed by the servo mechanism, the rotation of the offset portion 23 can be controlled with high accuracy, and the rotation of the cylindrical base 3 corresponding thereto can also be controlled with high accuracy. Therefore, when the direction of the offset portion 23 is changed after the series of welding of the welded portions 5 is completed, the direction can be appropriately changed.

The drive motors 40 and 50 are provided with servo motors.
When the motors are constituted by motors, a synchronization mechanism (not shown) is interposed therebetween to synchronize the rotations given to the respective drive motors 40 and 50. With this configuration, the cylindrical plate 30 of the lower electrode rotates in accordance with the rotation of the welding gun 20 of the upper electrode, and as shown in FIGS. 1 and 3, the welds 5 can be smoothly welded.

In FIG. 3, the left indicates the first half of the welding, the right indicates the second half of the welding, and the direction of the arrow indicates the direction in which the offset unit 23 is directed. First, in the first half of the start of welding, welding is performed by changing the direction of the offset portion 23 by 90 ° with respect to the half of the side frame 1 as shown on the left in the drawing. Next, the side frame 1 is inverted and the other half is welded in the same manner while changing the direction of the offset portion 23.

The present invention has the above-described structure.
Although any type of resistance welding machine can be used as the welding machine, a structure that can smoothly rotate the welding gun is desirable.

From this point, as shown in FIG. 2, a welding machine in which the welding gun 20 is supported at one end of the support arm 60 and a pressurizing device is attached to the other end of the support arm is preferable. In such a welding machine, since there is no load supported by the welding gun, the welding gun can be rotated by a small driving motor.

The welding machine shown in FIG. 2 comprises a welding gun 20, a supporting arm 60, a pressurizing device 70, a supporting post 80, and a transformer power supply 90. This welding machine is not provided with a pressurizing device (for example, an air cylinder) at the upper end of the welding gun 20 as is obvious from comparison with the conventional welding machine. One end of the support arm 60 is mounted, and the other end of the support arm 60 is
Are supported vertically.

Therefore, according to this resistance welding machine, the material to be welded placed on the cylindrical base 30 forming the lower electrode is transferred to the welding tip 22 of the welding gun 20 at the lower end of the welding holder 21.
When spot welding is performed by pressing, the pressing force applied by this welding is not directly applied to the welding gun 20 but is applied via the supporting arm 60 by the pressing device 70 via the supporting arm 60. .

That is, the welding tip 22 forming the upper electrode
Is attached to the lower end of the welding gun 20, and a pressing force is applied to the material to be welded by the pressurizing device 70 via the welding holder 21 of the welding gun 20, and the material to be welded is welded by the pressing force. You. Therefore, the support arc
The welding gun 20 is supported by the arm 60, and a pressurizing device 70 is attached to the supporting arm 60. In the pressurizing device 70, the rotational torque of the screw shaft is controlled by a vertically arranged ball screw mechanism 71. The thrust is converted into thrust or thrust in the axial direction of the screw shaft, and this thrust presses the welding gun 20 downward against the material to be welded.

More specifically, as described above, the conventional spot welder has a structure in which a material to be welded is sandwiched between upper and lower electrodes, and resistance welding is performed by applying a pressure between the two electrodes. ing. In particular, since a spot welding machine is a welding machine that concentrates current and pressing force by an electrode, a pressurizing device such as an air cylinder is provided at the upper end of the upper electrode, and a pressing device such as an air cylinder is applied directly to the upper electrode. In order to apply pressure, a high pressing force can be applied to the upper electrode, whereby spot welding can be achieved, and in any spot welding machine, a pressing force is applied directly from above to the welding tip forming the upper electrode in this way. It has a structure.

In the welding machine having such a structure, devices and members supported by the supporting arm include a pressurizing device such as an air cylinder in addition to a welding holder such as an upper electrode. In particular, in order to increase the amount of pressurization, a hydraulic cylinder or a gas cylinder is used as a pressurizing device instead of a mechanical means such as a spring. If the hydraulic cylinder or the gas cylinder is provided directly on the upper end of the welding holder on which the welding tip is mounted as described above, the supporting load to be supported by the tip of the supporting arm becomes extremely heavy, and inevitably the supporting The arm has a strong beam structure. Along with this, the support post also has a strong and large structure, so that the welding machine itself becomes large and heavy.

On the other hand, in the welding machine shown in FIG. 2, the support arm 60 bridges between the vertically arranged support post 80 and the welding gun 20 as described above, and this support arm is used. The welding gun 20 is supported by the arm 60. That is, the pressurizing device 70 is provided inside the support post 80 without providing a pressurizing device at the upper end of the welding gun 20, and the pressurizing device 70 presses the welding gun 20 via the supporting arm 60. Add.

Therefore, since the supporting arm 60 mainly only supports the welding gun 20, the weight can be reduced and the supporting load can be extremely small. For this reason, the support post 6
Arm 6 supported by a sliding mechanism 81 mounted on the side
0 slides up and down, and this up and down sliding is extremely light. The sliding mechanism 81 can be configured as any type as long as the sliding under such conditions can be satisfied.

Further, a ball screw mechanism 71 is arranged vertically or substantially vertically on the support post 80. The supporting arm 60 is attached to the vertically arranged ball screw mechanism 71 via a ball nut 73 at right angles to the ball screw mechanism 71, and the screw member of the ball screw mechanism is driven by the drive motor 72. When configured to rotate, the ball screw mechanism 71
The pressurizing device 70 can be constituted by the driving motor 72.

The ball screw mechanism 71 can convert the rotational motion of the screw member into the linear motion of the ball nut, and it is widely known to use a ball screw mechanism as such a motion conversion mechanism. A ball spline mechanism is also known as such a motion conversion mechanism, and is similarly used. However, since the ball nut mechanism is not used as such a motion conversion mechanism but is used as a pressurizing mechanism, the ball nut mechanism 71 is arranged substantially vertically in a vertically long shape. With this configuration, the thrust or thrust in the axial direction of the screw member generated by the rotation of the screw member in the ball nut mechanism 71 can be used as a pressing force for pressing the welding gun 20 downward.

That is, the ball screw mechanism 71 is
This is a mechanism in which a ball nut is screwed into a screw and a ball is interposed between them. This ball screw mechanism is usually used as a mechanism for converting a rotary motion into a linear motion or converting a linear motion into a rotary motion. Further, in the ball screw mechanism, along with the change of the movement direction, the rotation of the screw member generates an axial thrust on the ball nut screwed thereto. For this reason, as described above, if the ball nut mechanism 71 is vertically elongated and arranged vertically or substantially vertically, the direction of the thrust generated by the rotation of the screw member will be in the vertical direction of the support arm 60 and the direction of the welding gun 20. Align with the downward pressure direction.

The welding tip 22 forming the upper electrode is connected to one pole of a transformer power supply 90 via a flexible cable 91 and a conductive plate 92, and the welding tip 31 forming the lower electrode is connected to a conductive plate 93. Is connected to the other pole of the transformer power supply 90.

[0052]

As described above in detail, the present invention relates to a resistance welding machine for performing resistance welding by applying a current to an object to be welded between upper and lower electrodes by pressing the upper and lower electrodes. The offset device is provided with an offset portion offset from the central axis, and a rotating device for rotating the upper and lower electrodes about the respective central axes is provided.

Therefore, when the welding tip attached to the lower end of the offset portion is rotated about the central axis,
The welding tip can enter the inside of the box-shaped workpiece,
Incidentally, a metal box as shown in FIG. 4 can be easily welded.

If this rotating device is composed of a servomotor, the rotation of the offset section can be controlled accurately.

When the upper electrode is supported at one end of the support arm and a pressurizing device is attached to the other end, the upper electrode can be rotated under a low load, and can be smoothly rotated by using the offset portion. Can be welded.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a part of a welding machine according to one embodiment of the present invention.

FIG. 2 is an explanatory view of an example of a welding gun in the welding machine of FIG.

FIG. 3 is an explanatory view of a welding mode by the welding machine of FIG. 1;

FIG. 4 is an explanatory view perspectively showing a manufacturing process of an example of a metal box.

FIG. 5 is a diagram illustrating one principle of a conventional resistance welding machine.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Side frame of material to be welded 2 Bottom plate 20 Welding gun 21 Weld holder 22 Welding tip 23 Offset part 40 Drive motor 50 Drive motor 70 Pressurizing device

Claims (6)

[Claims] 1. A resistance welding machine for performing resistance welding by pressurizing and energizing a material to be welded between an upper electrode and a lower electrode, wherein a lower end of the upper electrode is formed with an offset portion offset from a central axis thereof, and A resistance welding machine comprising a rotating device for rotating the electrode, the lower electrode, the upper electrode, and the lower electrode around respective central axes. 2. A support arm for supporting the upper electrode at one end.
2. The resistance welding machine according to claim 1, further comprising: a pressure device for pressing the upper electrode downward at the other end of the support arm. 3. The resistance welding machine according to claim 1, wherein said rotating device is a servomotor. 4. An upper electrode comprising an electrode holder and an electrode tip attached to a tip of the electrode holder, wherein a lower end portion of the electrode holder is formed with an offset portion offset from a center axis thereof. 2. The resistance welding machine according to claim 1, wherein said electrode tip is mounted. 5. The resistance welding machine according to claim 1, wherein said lower electrode is constituted by a plate-like material. 6. The resistance welding machine according to claim 1, wherein the lower electrode is made of a disk material or a cylindrical base material having a radius equal to or larger than the rotation radius of the offset portion.