JP3236662B2 - Spot welding equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spot welding apparatus and a spot welding method, and more particularly to a spot welding apparatus controlled by a computer.

[0002]

2. Description of the Related Art Spot welding is a type of resistance welding in which a welding portion of a member to be welded is pressed and a welding current is applied between the members to be welded at the same time, and the above welded portion is welded by Joule heat. Since the welding temperature is lower than the welding temperature and the heating is performed in a short time, the effect of heating can be stopped within a narrow range near the welded portion, and there is an advantage that deformation and residual stress of the member to be welded are small.

FIG. 5 is a view for explaining a conventional general spot welding apparatus. In the figure, reference numeral 400 denotes a welding apparatus main body, and an upper fixed arm 40 integrally formed therewith.
1 and a lower movable arm 402 attached to the main body so as to be vertically movable. Welding electrodes 1a and 1b are respectively provided at the tip portions of the arms at electrode holders 411 and 411, respectively.
Attached via 412. Above the electrode holder 411 at the tip of the fixed arm 401, the holder 4
Pneumatic cylinder 40 pressurizing welding electrode 1a via
3 are attached.

In such a spot welding apparatus 400,
An operator connects the member A to be welded to the upper and lower welding electrodes 1a and 1b.
A driving device (not shown) which is disposed between and performs a predetermined operation
The lower movable arm 402 is moved upward to hold the member A to be welded between the upper and lower welding electrodes 1a and 1b, and a welding current is applied in this state to perform spot welding. At this time, the pneumatic cylinder 403 is driven by an operation of the operator, and the pressing force of the welding electrode, that is, the pressing force of the member A to be welded by the welding electrode is appropriately controlled according to the material and thickness of the member A to be welded. I do. Thereby, good welding can be performed for each of the members A to be welded.

[0005] In addition to the conventional spot welding apparatus in which a worker performs welding work by such an operation, a member to be welded which is installed in a production line of a factory and automatically conveyed is automatically and successively provided. There is an automatic welding robot that performs welding.

FIG. 6 is a diagram for explaining such an automatic welding robot, and shows a schematic configuration of a robot hand for spot welding. In the figure, reference numeral 500 denotes a spot welding robot hand which presses and holds a member A to be welded by a pair of upper and lower welding electrodes 1a and 1b, and heats and welds the pressed portion by resistance with a welding current, and is movable with a pair of fixed arms 10; The fixed arm 10 has a fixed frame 12 supported by a robot base (not shown), and is attached to a distal end of the frame 12. 1b comprises the fixed electrode holder 11. A welding transformer 2 is installed substantially at the center on the fixed frame 12, and the movable arm 2
The drive cylinder 3 of 0 is attached.

The movable arm 20 is attached to a movable frame 22 supported by a cylinder rod 3a of the drive cylinder 3, and is attached to a tip end of the frame 22.
The electrode holder 21 has a spot welding electrode 1a fixed to the tip thereof. Here, a support pin 22a is attached to the center of the movable frame 20, and a cylinder rod 3a of the drive cylinder 3 is connected to the support pin 22a.

In addition, the fixed and movable frames 1
The movable blocks 513, 5
23 is slidably mounted so that it can slide back and forth by a pneumatic cylinder or a motor or manually.
Further, an adjust mechanism 504 for adjusting the distance between the movable frame 22 and the rear end of the fixed frame 12 is attached between the movable blocks 513 and 523.

Next, the operation will be described. FIG. 6 shows a state in which the robot hand 500 clamps the workpiece A, and spot welding is performed in this state. That is, in this state, the adjusting mechanism 504 is adjusted according to the thickness of the member A to be welded. That is, when the upper and lower welding electrodes 1a and 1b press and hold the member A to be welded, the two welding electrodes are pressed. 1a and 1b are in a vertical pressurized state,
That is, the central axes of the upper welding electrode 1a and the lower welding electrode 1b are perpendicular to the press-contact surface of the member A to be welded.

When a welding current is supplied between the welding electrodes 1a and 1b from the transformer 2 in this pressurized state, the member A to be welded is spot-welded. Thereafter, the drive cylinder 3 is driven to move the movable arm 20 upward to release the clamping of the member to be welded by the welding electrodes 1a and 1b and to move the welding electrodes 1a and 1b to the next welding position. Open the electrodes slightly.

With the gap between the opposed welding electrodes 1a and 1b being slightly open, the member A to be welded is slightly moved to adjust the welding electrodes 1a and 1b to the next welding position. After the completion of the positioning, when the movable frame 20 is moved downward by driving the cylinder 3, the upper welding electrode 1a comes into contact with the member A to be welded on the lower welding electrode 1b, and a predetermined pressing force is applied. The movement of the cylinder stops when is added. In this state, spot welding is performed by supplying a welding current from the transformer 2 to the welding electrodes 1a and 1b as described above. Thereafter, the above operation is repeated to sequentially perform spot welding.

After the spot welding is completed in this manner, the member to be welded A is discharged or inserted from between the arms 10 and 20 by welding another portion of the member to be welded A or the like. Moves the movable blocks 513 and 523 toward the center of the arm by a drive mechanism (not shown) to bring the rear end fulcrum closer to the pneumatic cylinder 3 side. When the cylinder rod 3a of the drive cylinder 3 is made to protrude in this state, the distal ends of the movable arm 20 and the fixed arm 10 are greatly opened.

In this state, the member A to be welded is repositioned so that a desired welding portion is located between the upper and lower welding electrodes 1a and 1b. Then, when the movable blocks 513 and 523 are returned to the positions on the rear end side of the frame, spot welding is enabled. At this time, if there is a change in the thickness or the shape of the member A to be welded, the adjusting mechanism 504 is adjusted so that the two welding electrodes 1a and 1b are in a vertically pressurized state. Then, spot welding is performed as described above.

In the robot hand 500 described above,
Although the structure in which the drive cylinder 3 of the movable arm 20 is arranged at the center of the arm is shown, another structure of the robot hand is a spot in which the drive cylinder of the movable arm is arranged at the rear end side of the arm as shown in FIG. There is also a robot hand 600 for welding.

Here, the same reference numerals as those in FIG. 6 denote the same parts as those of the robot hand 500, and reference numeral 604 denotes an adjuster arranged behind the transformer 2 for adjusting the height of the fulcrum of the movable arm 30. In the mechanism, the threaded rod 604a is configured to be immersible by its rotation, and the end of the threaded rod 604a supports the frame 32 of the movable arm 30 so as to be rotatable. A drive cylinder 603 is disposed between the rear ends of the fixed and movable arms 10 and 30 and rotates the movable arm 30. The drive cylinder 603 is swingable to the rear end of the fixed frame 12 by a support bracket 603b. Supported by
The tip of the push rod 603a is pivotally supported by the rear end of the movable frame 32.

In the robot hand 600 having this structure, the height position of the movable arm is adjusted by the adjusting mechanism 604 in accordance with the thickness t of the member A to be welded, and the movable arm is placed between the upper and lower welding electrodes 1a and 1b. When the welding member A is sandwiched,
The pressing force by the upper welding electrode 1a is designed to act perpendicular to the press-contact surface of the member A to be welded.

Other welding operations are performed by the robot hand 5 described above.
This is almost the same as 00, but differs from the robot hand in that the operation of greatly opening the upper and lower welding electrodes is performed by increasing the amount of retraction of the rod 603a of the drive cylinder 603.

However, in the above-described spot welding apparatuses 500 and 600, since the member A to be welded is pressurized by the pneumatic cylinders 3 and 603, the pressing force is constant. Welding current I from a power source such as
₀ to the actual welding current by performing a constant air pressure indicated by the dashed line Pc (pressure P ₁₎ in FIG. 8 (a) I
_1, that is achieved a current flowing through the pressure contact portion of the member to be welded A, in this case the actual welding current waveform atmospheric become pressure P _1-consuming in current small a region of zeros and near the I _1, of this portion The pressing force was very useless.

[0019] In other words, in the pressurization of the spot welding, when the spot welding current I is a sine wave I _1, which when is the maximum I _m (t = t _m) to pressure P
If P ₁ , good welding can be performed, and when the spot welding current I is 0, the pressing force P may be 0, and ideally, a pressurized waveform Ps as shown by a dotted line may be obtained. However, such pressurization control has a drawback that the pneumatic cylinder cannot follow the change of the welding current every half cycle due to the air resistance of the cylinder, and can only perform rough pressurization control. Was.

[0020] Therefore, as the present inventors have apparatus which is improved such points, the welding current was welded member A by pressure of I ₁ and the same waveform as pressurized, efficient without loss of power We have already developed spot welding equipment.

FIGS. 9 (a) and 9 (b) are views for explaining a spot welding apparatus having such a configuration. This apparatus has the same mechanical structure as the spot welding apparatus shown in FIG. It has a configuration. In the figure, reference numeral 700 denotes the spot welding apparatus, which is a single-phase AC power supply 701, a transformer 703 for transforming the output thereof, and an on / off switch circuit 70 inserted between the single-phase AC power supply 701 and the transformer 703.
2 and a pair of upper and lower welding electrodes 1a and 1b for pressing and holding the member A to be welded and the upper welding electrode 1a are pressed to the lower welding electrode side by the pressing force of the electromagnetic attraction force. And a spot weld 730 having an electromagnetic force generating mechanism 740. Here, the transformer 7
The primary side coil 713 is provided on the primary side of the iron core 703a of FIG.
However, on the secondary side, in addition to the first secondary coil 723a, the second
Of the secondary coil 723b is wound.

In the electromagnetic force generating mechanism 740, the exciting coil 741a is connected to the second secondary coil 723b by the electromagnet 741, the contact piece 741b of the electromagnet 741, and the fulcrum 743 by the vertical movement of the contact piece 741b. It consists of a member 742 that can be moved up and down to the center. Here, the primary side coil 713 is connected to a single-phase AC power supply 701 via the switch circuit 702. Here, the exciting coil 741a is connected to the second secondary coil 723b additionally attached to the iron core 703a of the transformer 703, but the exciting coil 741a is connected to the first secondary coil 723.
a may be connected in parallel with the welding electrodes 1a and 1b, and the electromagnet 741 may be driven by the secondary voltage of the welding transformer 703.

Next, the operation will be described. In the spot welding apparatus having such a configuration, in the spot welding, the member A to be welded is sandwiched between the two welding electrodes, and in this state, a welding current is supplied from the transformer 703 to the welding electrodes 1a and 1b by the switch circuit 702. At this time, since the excitation coil 741a of the electromagnet 741 is connected to the second secondary coil 723b of the welding transformer 703, the pressing of the member A to be welded by the electromagnet 741 causes the welding current of the first secondary coil 723a. will be performed by pressurizing the same waveform Ps as I _1, can be carried out without loss efficiently the pressing power of the spot welding.

However, as described above, the spot welding apparatus 70 that simultaneously applies the welding current and applies the electrode pressure in synchronization with the application of the welding current.
At 0, it is good when the spot welding current I ₁ and the pressurized waveform P _S are completely synchronized, but when the two are out of synchronization, the resistance increases at zero pressure even if the current is small. The spark may generate holes in the member to be welded or the electrode. Therefore, in this apparatus, as shown in FIG. 8, a constant pressurization P _C0 (pressing force P ₀ ) by pneumatic or hydraulic pressure of the arm driving cylinder is further applied to the welding electrodes 1a and 1b.
This constant pressure P _C0, and as vibration pressure that is synchronized with the welding current I ₁ pressure P _S is superimposed is obtained, thereby eliminating the fear of damage to the workpiece to be welded and the electrode .

That is, in this spot welding apparatus 700,
The pressure of the member A to be welded is set to a constant pressure P by a pneumatic cylinder.
c (Pressing force P₀) And the above-mentioned welding
Style I ₁And the vibration pressure Ps synchronized with
Therefore, even when the vibration pressure is 0, the pressure
And the spot welding current I₁And pressure waveform P
Even if synchronization with s is lost, there is no
Therefore, sparks caused by an increase in the resistance of the contact
No holes are created in the member to be welded or the welding electrode,
There is no possibility of damage to the above-mentioned member to be welded or the welding electrode. Also,
In spot welding, it is difficult to generate heat if pressure is applied.
And welding heat I^TwoR is small where the pressure is large
However, in this apparatus 700, the welding force is applied by the welding current.
In the absence state, only the pressurization by the pneumatic cylinder is small.
As a result, heat generation in the initial stage of energization increases, and good spot welding is performed.
can get. And this makes it impossible A
1, spot welding of copper, titanium, etc. has also become possible.

FIG. 9B shows a modified example of the apparatus 700 shown in FIG. 9A. In the figure, reference numeral 800 denotes a spot welding apparatus of this modified example. In this apparatus, an iron core 803 of a welding transformer 803 is used.
a on the primary side, a first and a second primary side coil 713a,
713b is wound, and the second primary coil 713b is connected to the exciting coil 741a of the electromagnet 741, so that the electromagnet 741 is driven by the primary current of the transformer. .

[0027]

However, there are still many problems and points to be improved in the pressure control of the conventional spot welding apparatus, and the actual welding operation depends on the skill of a skilled worker. Many. First, the disadvantages and advantages of a specific configuration for realizing the pressure control of spot welding will be described in detail.

For example, as shown in FIG. 9A, an electromagnet 741 is used to generate a press-contact force of a member A to be welded by a welding electrode.
If this is driven by the secondary side output of the welding transformer 703, the circuit structure for generating the pressure contact force is simple because it is an alternating current. Although there is a good aspect that the strength of pressurization can be determined by this, there is a problem that noise is loud and a silicon steel plate is required for the iron core of the electromagnet 741. Also, as shown in FIG. 9B, an electromagnet 741 is connected to the welding transformer 8.
There is also a method of driving by the primary side input of 03, but in this case, there is a risk of electric shock, so the method shown in FIG. Further, in the method of FIG.
The electromagnetic coil 741a may be connected to the first electromagnetic coil 723a by omitting 23b.

If the electromagnet is driven by direct current, noise is reduced, but a rectifier circuit and a smoothing circuit need to be added, and the price of the apparatus increases accordingly. In some cases, the DC current for driving the electromagnet only needs to perform full-wave rectification on the secondary-side welding current and does not need to be smoothed. Although this DC current has advantages, it is preferable to use a method in which an appropriate vibration pressure is applied according to the waveform of the welding current shown in FIG.

When a spot welding apparatus having a transformer mounted on the welding arm as described above, that is, a so-called gantry, is small, for example, as shown in FIG. The electromagnetic force is 30 kg to 60 kg, and the stroke t ₁ by driving the electromagnet 741 of the movable arm 20 is 3 mm or less at the maximum.
It is about 0.1 mm.

Further, as shown in FIG.
If the movable arm 20 is pulled through the movable arm 2, the spring member 750 is deformed by the driving of the electromagnet 741 as shown by a dashed line.
The stroke t ₁ by driving the zero electromagnet 741 may be zero. When the pressing force of the electromagnet 741 is superimposed on the pressing force of the pneumatic cylinder 3, the main pressing by the pneumatic cylinder is about 50 kg to 100 kg, and the stroke of the movable arm by the driving of the pneumatic cylinder is 40 mm to 20 mm.
mm. When the main pressurization reaches about 50 kg, the electromagnet is energized and the electromagnet pressurization is superimposed. In this case, the welding ability is improved at the same welding current by about 20 to 30%.

Further, if the electromagnet 745 is disposed on the primary side of the welding transformer 2 as shown in FIG. 11, the pressure is generated by pushing up the welding arm 20. In this case, the secondary side of the welding transformer 2 is pressed. That is, no structure is arranged in the space from the welding transformer 2 to the welding electrodes 1a and 1b, and loss due to reactance in this portion is reduced. In this case, since the pressurization by the electromagnet 745 is performed by pushing up the movable arm 20, a rocking piece having a pressing member 745 c for pressing the spring member 750 at one end at a fulcrum portion 745 a ₁ of the main body 745 a as the electromagnet. 745b is swingably mounted, and the swinging piece 745c is
The other end of the electromagnet 745 is used to be attracted by the attracting piece 745e.
It is arranged on a height-adjustable base 746 above. Further, in this device, the rear end of the movable arm 20 is lowered by driving the pneumatic cylinder 3, and the pressing member 745c of the electromagnet 745 is sandwiched between the spring member 750 and the upper surface 745d of the electromagnet housing 745a. Thereby, the repulsive force of the spring member is applied to the member A to be welded as the pressure of the welding electrode.

In this case, the welding electrodes 1a and 1b sandwich the member A to be welded by driving the pneumatic cylinder 3, the rear end of the movable arm 20 descends, and the pressing member 745c and the spring member 7 are moved.
When the spring member is deformed due to contact with the
When the pressure reaches about 0 kg, the energization of the electromagnet 745 is started, and the electromagnetic pressing force may be superimposed. This increases workability by 10 to 20 percent as in the above case.

When the member A to be welded is ejected and inserted, the rear fulcrum of the movable arm 20 is moved closer to the center of the pushing force by the cylinder by sliding the movable blocks 513 and 523. In addition, the displacement speed of the welding electrode of the movable arm can be increased.

Next, there will be described a method of grasping the nugget which determines the quality of welding, that is, the quality of the spot melting portion, from the relationship between the thermal expansion of the nugget and the change in the electromagnetic pressure. When the nugget is thermally expanded, the electromagnet works more effectively, that is, the movable arm 20 is lifted, and the deflection of the spring member 750 by the electromagnet 741 further increases, thereby conversely forming the nugget. You can know.

First, the case where the welding current is alternating current will be described. In this case, the state of the nugget generation is checked by measuring the increase in the pressing force of the spring member due to the expansion of the nugget, and the nugget state for each half cycle can be known by the change in pressurization for each half cycle.

Here, as a specific method of measuring the pressing force,
When a method of detecting the change in the pressing force from the change of the welding electrode itself is adopted, in the case where the welding electrode is directly pressurized by the rod of the pneumatic cylinder 403 as in the spot welding apparatus shown in FIG. Thus, despite the fact that the heat generation expansion changes every half cycle in the nugget, this cannot be accurately grasped. In other words, due to the air resistance of the cylinder, the movable arm 402 cannot follow the expansion change every half cycle of the nugget, and can only grasp a rough nugget formation state.

On the other hand, when the electromagnetic force and the deformation repulsion force of the arm or the spring are used to press the welding electrode as in the spot welding apparatus shown in FIGS. 10 and 11, the air resistance of the pneumatic cylinder is reduced. As described above, there is no element for suppressing the displacement of the welding electrode, and the trace of the expansion of the nugget every half cycle can be accurately captured.

Further, even if a pulsating current obtained by full-wave rectification of the alternating current is used instead of the alternating current as the driving power source for the electromagnet, the movement of the nugget can be known every half cycle as in the case of the alternating current.

Next, the case where the welding current is DC will be described. In this case, there is no change in expansion of the nugget every half cycle. However, when the holder 411 of the welding electrode 1a is directly pressurized by the rod of the pneumatic cylinder 403 as shown in FIG. The air resistance of the cylinder works, and the displacement of the cylinder rod is delayed,
The actual change in the nugget expansion differs slightly from the change in the welding electrode itself.

That is, since the welding electrode 1a hardly displaces despite the expansion of the nugget, the electrode strongly presses the member A to be welded. An error occurs due to a complicated increase in pressurization in the electrode displacement determined as described above. Therefore, in order to know an accurate nugget formation state, a true increase in pressure must be calculated from the actual electrode displacement.

On the other hand, as shown in FIGS. 10 and 11, in the case where the movable arm 20 is rotated by the cylinder rod 3a with the rear end of the movable arm as a fulcrum and the center of the movable arm as a power point, FIG. Unlike the device in which the holder of the welding electrode 1a is directly pressed into contact with the rod of the pneumatic cylinder 403 as shown in FIG. Even if there is no movement of the cylinder rod, the displacement of the welding electrode due to the expansion of the nugget can be regarded as the displacement of the rear fulcrum of the movable arm 20, and the change of the pressing force can be accurately grasped.

The method of capturing the pressing force of the welding electrode by shifting the rear fulcrum of the movable arm as described above is not limited to the method of pressing the welding electrode by the electromagnet, but the method of applying the pressing force by the electromagnet as shown in FIG. Even in a type without a pressure mechanism, a change in pressure can be accurately read from a change in expansion due to a nugget type. In other words, if the structure is such that the cylinder rod and the central part of the movable arm are connected to each other, compared to a structure in which the electrode is rigidly connected directly to the cylinder, the change in the pressing force from the movement of the rear fulcrum of the movable arm with the connection point as a fulcrum. You can read. In this case, FIG.
As shown in (c), the formation of the nugget N can be accurately grasped moment by moment, and the success or failure of welding can be determined.

However, in this case, the welding electrode is pushed up by the expansion due to the formation of the nugget, but the welding electrode tends to lower due to the softening of the member A to be welded, and the softening of the nugget portion is caused by the electrode pushing action by the nugget formation. It works negatively. In other words, the electrode lowering (-) action due to the pressure increase and the electrode lowering (-) due to the softening of the base material.
Overlaps with each other to prevent the electrode rise (+) due to thermal expansion, so that the nugget expansion may not be read very accurately, and the reading error of the pressing force may be large.

In order to solve this, it is necessary to measure the pressing force directly, not the displacement of the welding electrode.
For example, by using a piezoelectric element or the like to measure the pressing force,
It is possible to know the formation of the nugget more accurately and instantly.

In the robot hand shown in FIGS. 6 and 7, since the movable arm 20 is supported with its central portion as a point of force and its rear end as a fulcrum, the rigid body design requires only the movable arm 20 and the fixed arm 10. There is no need to design the housing or the like with high rigidity, which is advantageous for small size and light weight. When the nugget formation is read by displacement of the welding electrode, the displacement of the welding electrode at the front end of the movable arm can be read as the displacement of the rear end of the movable arm according to the principle of leverage. Further, in the robot hand of FIGS. 6 and 7, a jaw that requires particularly rigidity for engaging the upper and lower welding electrodes as in the welding device 400 of FIG. Since it does not have a structure to which 402 is attached, it has a structure excellent in structural mechanics.

Further, in the apparatus 400 shown in FIG. 5, since a vibration pressurization by the pneumatic cylinder 403 is received by the apparatus main body, a strong rigid body design is required.
In the robot hand 500, the pressing force is applied directly to the electrode, and the vibration pressure by the electromagnet is not applied to the housing mechanism (chin). It just takes. Therefore, vibration can be easily absorbed by attaching a vibration absorbing material to a mounting portion of a component such as a pneumatic cylinder or an electromagnet.

In the apparatus 500 shown in FIGS. 10 and 11, the welding electrode 1a is moved by the pneumatic cylinder 3 to a position where the welding electrode 1a comes into contact with the member A to be welded, so that the electromagnet 741 effectively exerts an attractive force on the welding electrode 1a. Can be positioned at a sufficient distance. Further, the pressing force can be replaced by the elastic force of the movable arm itself instead of the spring force as in the apparatus of FIG. 10 (a). In this case, when the movable arm is bent and the electromagnet is attached, the elastic deformation force corresponding to the bending is applied between the welding electrodes as a pressing force.

Here, when the nugget is formed and the welding electrode is pushed up due to thermal expansion, this pushing force acts in the direction in which the electromagnet separates. Even in this state, if the electromagnet is stuck, the amount of the pushing force is reduced. Only the pressing force increases. When the welding current is alternating current, the forging force is applied every half cycle when the welding current is alternating, and the same effect as when forging is applied even when the nugget is sufficiently completed is obtained. The pressurization by the electromagnet 741 is different from the pressurization by the pneumatic cylinder 3 which is constant even when the welding current increases, and both the pressurization and the vibration forging pressure increase with the increase of the welding current.

For example, in the spot welding apparatus 500 shown in FIG.
When the central part of 0 (pneumatic fulcrum) rises, the movable arm 2
The rear fulcrum of 0 is pushed down in reverse, but at this time, the rear fulcrum does not exert much force. Therefore, the rear fulcrum may be provided near the pneumatic fulcrum, and the member A to be welded is arranged between the welding electrodes. In doing so, the stroke can be greatly increased. That is, the distance between the fulcrums is reduced at the same time as the movable arm is pulled up by the cam mechanism, for example. When the tip of the movable arm is sufficiently raised, the member to be welded (base material) is inserted between the electrodes. When the member to be welded A is located at the spot position,
The distance between the fulcrums is increased while the welding electrode is lowered by the pneumatic cylinder.

The upper and lower welding electrodes contact the workpiece A,
When pressure is applied to this, the rear end of the movable arm is at such a height that the stroke t ₁ (gap of the electromagnet) of the movable arm driven by the electromagnet is about 3 mm. The gap of the electromagnet differs depending on the deflection coefficient of the movable arm arm. Thereafter, the electromagnet 741 is energized.

When the welding electrode is fixed, a pressure meter for measuring the displacement of the electrode is attached, and the change in the pressing force during welding is taken as data. By performing the pressurization control based on the data, the pass rate can be increased.

The advantages of the pressure control by the electromagnet method will be described in comparison with the pneumatic method. First, in the pressurization control by the electromagnet method, when the welding voltage decreases, the pressing force can be reduced, so that the effect is more significant. On the other hand, in the pneumatic method, pressure is applied irrespective of a change in voltage. Unnecessarily large pressure is applied even when the current is zero or small, so that the heat generated by the I ² R is reduced. Due to the nature of air pressure, precise pressure control is not possible.
Conversely, when the pressurization is small, there is a state where the current is large. At this time, sparking occurs or the nugget can be removed, resulting in poor welding. Conversely, when the pressure is increased by catching the rise in the current, the current may decrease due to a shift of several cycles. At this time, welding strength is insufficient (nugget formation is insufficient). Therefore, in the electromagnetic pressurization method, what has conventionally stopped the line due to a defect can be brought to a pass range without stopping.

In the case of the air pressurization method, when the size of the nugget is caught by the electrode displacement method and the current is stopped when the nugget reaches a predetermined position, the nugget suddenly cools and a contraction phenomenon occurs. Shortage occurs. This is when you want forging pressure. However, if a mechanism for applying forging pressure is provided, the apparatus becomes complicated and expensive welding is performed. On the other hand, in the case of the electromagnetic pressurization type, when the electromagnet is driven by the primary current of the welding transformer as shown in FIG. Strong energization is performed, which allows forging pressure to be applied. This forging pressure has a movable arm as shown in FIG.
Since the rear end and the tip of the movable arm are applied to a simple and highly rigid part without applying a pressure load to the housing, the overall size is small and lightweight, and the size of the forging force depends on the product, material and shape. It is possible to change it.

The forging pressure is increased by the degree of nugget formation, that is, when it is larger than a predetermined nugget,
If the nugget is slightly smaller, it may be smaller.

When the number of members to be welded (base material) is one or more, the component is defective, or when the size of the projection is poor, the abnormality before the initial energization is dimensional in terms of the electrode position. Instead of reading, the abnormalities can be known from changes in the electrode pressing force.

In this way, the presence or absence of warpage or distortion of the article (welded member) can be known from the change in the pressing force. This slight change in the pressing force and abnormalities are caught.For example, if there is warpage or distortion, it is impossible to respond immediately with an air cylinder, but it is impossible.However, the electromagnet method can instantly increase the pressing force, impairing workability. Without having to deal with it.

Further, not only the electromagnetic force can be changed in response to the abnormal pressure, but also the welding current can be changed. In other words, in the conventional method, the line which was stopped due to a material abnormality can be passed by increasing the pressure and increasing the current. For example, when the height of the projection is large or when there is a foreign substance, the energizing time may be lengthened to increase the pressure (electromagnetic force) and reduce the current.

It is impossible to read the cause and the countermeasure at a moment, but it is impossible to read the problem. If the data adjusted for the pressing force, welding current and energizing time based on the judgment of
It is possible to respond to instantaneous setting of welding conditions with the same judgment as a skilled person.

Furthermore, the method of using the electromagnetic force and the pneumatic pressure not only has a small input power and secures the welding strength, but also has the ability to follow the pressurization and optimize the characteristics of the pressurization so as to reduce the press-contact trace of the welding electrode. Can be cleaned.

In the case of the electromagnetic pressurization method, although both the electromagnetic force and the welding current are normal output values, the base material surface is rusted, has a film, is contaminated with dust or oil, and so on. When the welding current is small and the nugget formation speed is small (the electrode displacement is small and the resistance value is large), the current of the electromagnet increases. When the power supply voltage is reduced and the current is reduced, and the nugget is small or the nugget formation speed is low, the pressure is reduced and the energization time is lengthened by the abnormality. In this manner, the formation of the nugget can be brought to a regular strength by increasing the welding current, extending the conduction time, or reducing the pause time in the case of pulsation. In addition, even when the surface condition or the contact surface of the member to be welded is abnormal, it is possible to adjust the pressing force until a predetermined nugget is formed by reading the change in the characteristic curve of the pressing force or the electrode displacement, thereby changing the heat generation. Such methods include aluminum, copper,
It is particularly effective for non-ferrous metals such as brass. That is, in the past, a poor welding or a line stop was used, but the pass rate can be drastically increased without stopping the line.

In the control of the nugget formation, not only the change in the welding force by the welding electrode but also the electric resistance of the member to be welded is calculated at the same time, and the thermal expansion of the spot-welded portion (the state of the nugget formation) and It is more preferable to set the welding conditions based on the abnormality of the electric resistance. In other words, in the control of the thermal expansion of the nugget, the welding current decreases due to the abnormality of the surface film of the member to be welded, and if the formation of the nugget is delayed, not only the change in the welding force but also the change in the welding current is captured together. It is better to solve the problem, for example, by increasing the pressing force and increasing the energizing time. For example, when parts other than the joints of the parts to be welded come into contact due to warpage or distortion of parts and extra welding current flows, or when the shape of the projection is large, increase the pressure and increase the current. Is good.

In the case of simply grasping the nugget formation abnormality or the like by the pressing force, it may not be possible to judge whether the welding current should be increased or the duration thereof should be increased. If there is an error in this judgment response, welding failure will increase,
By measuring the electric resistance, it can be seen that when the electric resistance is large, the surface condition is poor and rust or dust is conceivable, so it is better to increase the pressure and lengthen the welding time.

The electric resistance may be small depending on the shape of the warp or the projection. At this time, since the formation of the nugget is usually delayed only by the natural increase in the current, it is important to increase the welding current in accordance with the decrease in the electric resistance. It is to be noted that, even if the welding current value is measured instead of measuring the magnitude of the electric resistance, it is possible to catch a change in the surface condition such as a film or dust. Phenomena such as an increase in current also occur due to warpage or abnormal processing. According to this, the magnitude of the pressurization, the current, the current supply time, the pulsation method, and the like can be changed as described above. However, since there are many causes only due to abnormal electric resistance or abnormal current value, it is difficult to make the welding current correspond perfectly, and it is necessary to observe the welding force and change in electrode displacement.

The abnormality of the electric resistance or the welding current is smaller than that of the normal one even when the product is inclined even when the welding electrode is normal. Such a decrease may be caused by the above-described defect of the base material surface. In this case, if the welding force of the member to be welded is increased as planned and the welding current is applied for a longer time, the tip of the electrode is badly shaped, the electrode trace becomes very dirty, and the welding strength is poor. When the change characteristics of the welding force of the welding electrode at this time are also observed, it can be seen that the welding force has the change characteristics (curve A ₁ ) shown in FIG. 14 (a), and other than the standard characteristics (curve S ₁ ). In the case (curves A ₁ , B ₁ , C ₁ ), as shown in FIGS. 13 (a) to 13 (c), a problem has occurred in the contact state between the welding electrode and the member A to be welded. There is.

Here, FIG. 13 (a) shows the case where the member A to be welded is not perpendicular to the axis of the welding electrode, and FIGS. 13 (b) and 13 (c).
Indicates that the member A to be welded is disposed normally,
13A and 13B show a case where the tip portions are partially reduced.
FIG. 13 (c) shows a case where the facing portions of the upper and lower electrodes are worn similarly, and FIG. 13 (b) shows a case where the worn portions of the upper and lower electrodes are different. ) Correspond to the characteristic curves A ₁ , C ₁ , and B ₁ .

Such an abnormality around the welding electrode can be immediately recognized by a person, but when the welding operation is unmanned and automated, the characteristic curves A _{1 to} C _{1 are used} as shown in FIG.
It is determined which of (a) to (c) is abnormal. However, when responding by looking at the above-mentioned waveforms, it is impossible to respond immediately, and after welding is completed, it is possible to determine which of the characteristic curves A _{1 to} C ₁ , but this alone is useful for the measure against defects. Absent. In this case, since the electric resistance (welding current) is aimed at the same time, looking at the change in the characteristic curve A ₂ -C ₂ in the electrical resistance shown in FIG. 14 (b), pressurized pressure characteristics welding current in the welding early standard In the case of (change characteristic curve S ₂ ), it is possible to determine any _one of the pressure characteristic curves A _{1 to} C ₁ and correct the horizontality of the workpiece A in real time. Here, when the pressure characteristic is curve B ₁ or C ₁ , the welding electrode needs to be replaced, and the welding electrode surface may be corrected to a normal state by installing an automatic polishing machine. Monitoring this electrical resistance or welding current value and automatically restoring the welding state to the normal state based on this is somewhat more responsive and reliable than monitoring the welding force. There is not enough time for perfect control.

The welding conditions (addition) shown in FIGS.
Pressure change characteristic curve A₁~ C₁) The displacement of the welding electrode
The change in the height position of the welding electrode on the movable arm
When viewed in terms of separation (dimensions), as shown in FIG.
Characteristic curve A of pressure force₁~ C₁Electrode shift corresponding to
Characteristic A_Three~ C_ThreeIs obtained. That is, each characteristic first
Large movement occurs and eventually equilibrates (with thermal expansion) and gradually
And it decreases with cooling (stop of power supply). this
If you capture the first major change, the change in pressure
A₁Or characteristic curve B ₁Or characteristic curve C₁Can be determined,
Stop the characteristic curve A₁In the case of
Correct the pinching state and set the characteristic curve B₁Or C₁In the case of
Replace or automatically repair the welding electrode. The characteristic curve A
₁Automatically when the welding is in an abnormal state.
May be modified. In addition, energization is stopped at point t
Therefore, when welding after correcting the above abnormal state,
The welding current is about to start, so apply a slightly stronger welding current again.
If it is poured first, sufficient welding strength can be obtained.

By constantly detecting the three factors described above, ie, the change in the pressing force, the change in the electric resistance or the welding current, and the change in the electrode, appropriate welding conditions can be automatically obtained. It is the instantaneous adjustment of the pressing force, the adjustment of the magnitude of the welding current and the length of the energization time, and the adjustment of the interval of the pulsation energization suspension when the welding current is a pulse current. As a result, the line that had been stopped as a defect until now and that was discarded as a defect almost entered the acceptable range. However, members with defects that cannot be repaired are discarded. In this way, by detecting the welding force, electrical resistance, and electrode displacement, and making full use of the three conditions of welding force, welding current, and conduction time, many products that have been rejected until now can be passed very efficiently. And can be. In addition, the characteristic waveform diagram used in the above description is different from the instantaneous value in the case of DC and the like in the case of AC or the like.
You may understand that it is as above.

Further, in addition to the three major conditions of the welding force, welding current, and conduction time, there are other factors that are essential for welding, such as electrode material, size, shape, tip shape, and dirt on the surface. To do better, this must be monitored constantly. Further, although the impedance Z of the secondary circuit of the welding transformer is Z = R + jX, of the actual resistance R, the contact resistance of each member constituting the welding current circuit is also important. Otherwise, the measurement data of the welding current will be out of order. Similarly, the presence of a magnetic substance in the welding current circuit is also a significant change factor, and confuses the data unless this point is taken into account. As described above, the contact resistance of each part and the presence of the magnetic material give important results for the measurement of the welding current and the electric resistance together with the change of the power supply voltage, and therefore need to be constantly monitored. Also, regarding the member to be welded which enters the welding current circuit, the condition, material,
Various conditions such as shape, surface condition, angle with the electrode, contact condition, etc. must be set to proper ones, or it may cause poor welding.

The above-mentioned factors affect the electric resistance, welding current, heat generation, vibration, displacement, and the like. Therefore, these effects must always be considered when measuring data. Then, it is necessary to change the correspondence of welding conditions based on the correct judgment of the data to achieve the best pass situation. Despite the fact that this requires years of experience and intuition, the number of skilled workers with such abilities is decreasing year by year. For this reason, by putting the judgments and responses of these excellent technicians into a computer, anyone can perform welding that is comparable to welding of excellent technicians.

The purpose of the present invention is to create optimized data of welding conditions with an accurate sense, such as a speared god, to accurately grasp the cause of a welding condition that does not match this, and to determine the welding conditions. In case that the fluctuation of electric resistance and welding current and the error of heat generation state (including the state of nugget formation) caused by non-optimization do not cause welding failure, that is, when welding conditions are not optimized in this way Therefore, in order to put the product in the acceptable range, it is necessary to respond by changing three factors of welding current, electrode pressing force, and energizing time.

For example, if the welding current decreases, the heat generation naturally decreases and the nugget becomes insufficient. At this time, if the pressure is reduced appropriately, the heat generation is promoted by I ² R and the required nugget strength can be maintained. It is. If the nugget is still insufficient, the energizing time may be increased. In addition, the rust of the electrode also increases the area in contact with the member to be welded, so the nugget generation is insufficient with the same initial welding current, affecting the welding strength, and accordingly gradually increasing the current appropriately.
The pressurization must also increase accordingly, but taking into account the change curve between the initial electrode replacement and the next electrode replacement time, the computer provides the computer with data on accurate judgment of technicians like God. If you put it in, unlike the conventional welding method, which has a high rate of rejection only by the reliable setting of the conditions, most of the welding defects are solved by the accurate judgment and response of the experienced welding person, and the conveyor can be stopped or stopped. It is possible to prevent waste of materials and energy due to producing defective products.

The present invention has been made based on such research on conventional welding technology, and relates to a basic technology for putting know-how of a welding technician into a computer. It is an object of the present invention to provide a spot welding device that can automatically perform welding comparable to welding performed with the know-how of a welding technician under the best welding condition that was impossible with a reliable response. .

Hereinafter, the objects of the present invention will be described. (1) The control of the press-contact force of the member A to be welded cannot be instantaneously performed by the conventional control using a pneumatic or hydraulic cylinder. An electromagnetic force with a function to follow the strength of the pressure contact force, for example, according to a current waveform of 50 °, when the current is zero, the pressurization is weak, and where the current value is the highest, the pressing force is also the highest. Pressurization and effective use of Joule heat (I ² R) to reduce the overall size and weight. (2) At the time of spot welding, the pressure by the welding electrode is perpendicular to the member A to be welded. (3) At the time of quick welding, the welding point, that is, the lifting stroke of the welding electrode is minimized in order to increase the workability of the spot welding operation, and when the member to be welded is inserted into the welding electrode feeling, the member to be welded and the welding electrode are used. The distance between the upper and lower welding electrodes is increased in order to avoid interference with the welding electrodes. (4) In order to have the immediate pressure property of the pressing operation of the electromagnet, various pressurizations can be performed by the structure which can be performed without moving the rod of the pneumatic cylinder which performs the raising / lowering operation of the welding electrode during the pressing operation. Be able to realize the characteristics. (5) The lifting speed of the welding electrode can be automatically changed. (6) The pressure by the pneumatic cylinder can be automatically changed during welding. (7) The state of nugget formation during welding can be detected. (8) It is possible to control the pressing force according to the nugget formation state. For example, when the formation of the nugget is extremely fast and large, the welding current is automatically reduced and the pressurization is increased, and in some cases, the energization time is shortened to eliminate the occurrence of voids and pinholes in the nugget. To do. Conversely, when the nugget is small and the forming speed is small, reduce the pressing force and increase the current.
The energization time is lengthened to increase the calorific value. (9) Further, it is possible to automatically control the welding current according to the nugget formation state. For example, a change in the electric resistance or the welding current is detected, and one or both of the increase / decrease control of the welding current and the conduction time control can be appropriately performed according to the change. (10) The shape of the tip of the welding electrode, the state of clamping of the member to be welded by the welding electrode, and the like are sensed, and based on the sensed information, the process of recovering the failure can be performed to some extent automatically.
For example, the recovery of a relatively simple defect such as the polishing repair of the tip of the welding electrode can be automatically performed, and the production line is automatically stopped so that a worker can be instructed to respond. As described above, an object of the present invention is to provide a spot welding apparatus capable of automatically performing the adjustment of the pressing force, the adjustment of the increase / decrease of the welding current, and the adjustment of the conduction time so that the best welding can be performed. To get.

[0076]

A spot welding apparatus according to the present invention (the first aspect of the present invention) holds a member to be welded in pressure by a pair of welding electrodes, and spot welds the pressed portion by resistance heating. In the, as a device for monitoring the welding process of the welding portion, a welding force monitoring device that monitors the welding force of the member to be welded by the welding electrode, and a current monitoring device that monitors the welding current applied to the welding electrode And a computer for controlling an actuator device for moving the welding electrode up and down and a power supply device for outputting the welding current. The computer has a material for a member to be welded, which affects a welding state. When various welding conditions, including surface, surface condition, and thickness, are specifically set, the change characteristics of the welding force for performing the best welding and Welding current, Yes equipped with a storage device for storing in each case the variation characteristics including current time, also has a central processing unit of the computer,
A characteristic reading means for reading, from a storage device, an optimum change characteristic of the press-contact force and a welding current in the case based on specific setting data of the welding condition input from the outside from a storage device; Pressing force control means for receiving the pressing force monitor signal and controlling the actuator device so that the pressing force by the welding electrode matches the best change characteristic in that case; and receiving the welding current monitor signal and detecting the welding current. And a welding current control means for controlling the power supply device so as to match the optimum change characteristic including the current supply time.

Further , the above-mentioned electrode support mechanism is provided on the apparatus main body side.
Fixed arm with fixed, fixed-side welding electrode at the tip
And the rear end as the pivot point and the central part as the pivot point.
To support the fixed arm, and
And a movable arm having a contact electrode.
And the actuator device lifts the movable arm.
Pneumatic or hydraulic cylinders or
It is a solenoid.

In addition, the tip of the movable arm is located
Electromagnet that draws the side of the
The pressure is generated by elastic deformation of the movable arm.
The formation of the spot-welded portion is based on the drive of the electromagnet.
The kinetic current is measured by the pressure and the welding electrode monitored above.
One or both changes from the above characteristic reading means
Characteristics of welding force of welding, including welding current
Control is performed so that it matches the optimum change characteristics.
It is.

[0079]

[0080]

[0081]

According to a second aspect of the present invention, in the spot welding apparatus, there is provided a spring member attached to a rear end of the movable arm, and an electromagnet for elastically deforming the spring member. A pressing mechanism that presses the rear end of the movable arm by the elastic deformation force to press the welding electrode on the front end side of the movable arm against the member to be welded, and forms the spot-welded portion by monitoring the drive current of the electromagnet by monitoring the drive current. The change in one or both of the pressing force and the welding current is controlled so as to match the optimum changing characteristics including the energizing time of the pressing force and the welding current from the characteristic reading means, respectively. .

According to a third aspect of the present invention, in the spot welding apparatus, the movable arm or the spring member is further deformed by the pneumatic pressure or the pressure of the hydraulic cylinder or the solenoid to reduce the vibration pressure contact force by the electromagnet. A constant pressure contact force is superimposed by the pneumatic or hydraulic pressure of the cylinder or the electromagnetic force of the solenoid.

[0084]

[0085]

According to the present invention (claim 4 ), in the spot welding apparatus, the primary side is connected to a normal power supply irrelevant to the welding current control, and the welding transformer outputs the welding current to the secondary side; A power supply circuit comprising a power supply circuit for controlling a secondary output of the welding transformer based on a control signal from a current control means; and a regulator capable of adjusting the voltage of the primary side of the welding transformer. A DC or AC electromagnet connected to the electromagnetic coil via
Immediately before the start of welding, the voltage applied to the primary side of the welding transformer is controlled by the regulator and input to the electromagnet, so that an appropriate pressing force is applied to the member to be welded.

According to a fifth aspect of the present invention, in the spot welding apparatus, the first electromagnet is connected to the primary side of the welding transformer via a voltage-adjustable regulator. A second electromagnetic coil connected to the secondary side of the welding transformer is used as a DC or AC electromagnet mounted on one iron core, and a voltage applied to the primary side of the welding transformer and a voltage applied to the secondary side of the welding transformer. The secondary side output is superimposed so as not to cancel the respective polarities and is input to the first and second electromagnetic coils. During the energization of the welding current, the pressurization of the member to be welded is synchronized with the welding current. The electromagnetic force generated by the coil is synthesized.

According to the present invention (claim 6 ), in the spot welding apparatus, an AC electromagnet is used as the electromagnet, and when the AC welding current becomes zero, the pressure applied by the electromagnet becomes close to zero. When the AC welding current is maximized, the pressing force by the electromagnet is maximized,
Resistance heating by the welding current is optimized from the relationship between the current flowing through the member to be welded and the contact resistance of the member to be welded.

[0089]

[0090]

[0091]

According to the present invention (claim 1),
Monitoring of the welding process in spot welding is performed by monitoring the welding force and welding current of the upper and lower spot welding electrodes, and controlling the welding force and welding current of the spot welding electrodes by a computer, that is, in the computer, When the various welding conditions, including the material, surface condition, and thickness of the member to be welded, which influence the welding condition, are specifically set, the optimum change characteristics of the welding force and the welding current for performing the best welding. The optimum change characteristics including the energization time are stored in the storage device for each case, and based on the specific setting data of the welding conditions input by the welding worker, the optimum change characteristics in that case are stored. The welding force and welding current are read from the storage device, and the change in one or both of the monitoring welding force and welding current monitored above Since the press-contact force and welding current of the above-mentioned member to be welded are controlled so as to match with these optimum change characteristics read from the storage device, the optimum welding force is controlled according to the type, thickness and surface condition of the member to be welded. Welding can be performed, and when an abnormality occurs in the process of forming the welded portion, the above-described pressing force and welding current can be corrected so that each change matches the change characteristic in a normal state.

If the computer cannot correct the abnormal formation of the welded portion only by controlling the pressing force and the welding electrode, for example, the member to be welded is inclined from a horizontal plane, and the pressure of the welding electrode is reduced. If welding is performed in a state where vertical pressure is not applied to the welding or when the tip of the welding electrode is unevenly worn, stop the line and program the operator to inform the operator, thereby increasing the product yield. Can be improved.

Further , the above-mentioned electrode support mechanism is provided on the apparatus main body side.
Fixed arm with fixed, fixed-side welding electrode at the tip
And the rear end as the pivot point and the central part as the pivot point.
To support the fixed arm, and
And a movable arm having a contact electrode.
And the actuator device lifts the movable arm.
Pneumatic or hydraulic cylinders or
Because the solenoid is used, the distance from the pressure contact point (action point) of the member to be welded by the welding electrode to the rotation fulcrum of the movable arm can be made large over the entire length of the movable arm. Even if the thickness of the welded part fluctuates from the standard thickness depending on the part, even in the axial direction of the welding electrode,
The displacement of the press-contact surface of the member to be welded from the normal direction is small, and the press-contact of the member to be welded by the welding electrode can always be performed at an angle close to the direction perpendicular to the press-contact surface of the member to be welded.

In addition, the position of the tip of the movable arm
Equipped with an electromagnet that draws the part, the welding force of the welding electrode
Is generated by the elastic deformation of the movable arm.
Therefore, the mechanism for generating the welding pressure of the welding electrode
It can be easily realized only with magnets. Also the above electromagnetic
The drive current of the stone is monitored above for the welding current and pressing force.
The change coincides with the optimum change characteristic from the characteristic reading means.
Control to form the spot welded part
Therefore, even if the thickness and material of the members to be welded are different,
In each case, the optimum pressing force and welding current
Can perform welding, and some abnormalities occur during welding.
Even if it is born, it can be repaired automatically .

[0095]

[0096]

[0097]

In the present invention (claim 2 ), a spring member is attached to the rear end of the movable arm, and an electromagnet that elastically deforms the spring member by its electromagnetic force is arranged near the spring member. Since the rear end portion of the movable arm is pressed by the elastic deformation force of the spring member to press the welding electrode on the front end side of the movable electrode against the member to be welded, the electromagnetic force is applied without rotating the movable arm. Can be generated and responsiveness and workability can be improved. In this case, since the electromagnetic vibration is applied only to the movable arm and not to the apparatus main body, the rigid design of the apparatus main body can be simplified.

In the present invention (claim 3 ), the movable arm or the spring member is further deformed by the pneumatic pressure or the pressing force of the hydraulic cylinder or the solenoid, and the cylinder is subjected to the vibration pressure contact force by the electromagnetic force. A constant pressure contact force due to pneumatic pressure, hydraulic pressure or solenoid electromagnetic force is superimposed, so the pressure contact force does not fall below a certain value.
Excessive heat generation due to a synchronization deviation between the welding current and the pressing force can be avoided, and damage to the welding electrode and the member to be welded can be prevented.

[0100]

[0101]

Further, in the present invention (claim 4 ), the drive current of the electromagnet is controlled by the electromagnetic coil via the regulator capable of adjusting the voltage from the primary side of the welding transformer irrespective of the control of the welding current. And the appropriate pressure is applied to the member to be welded by the electromagnet, so that the welding force can be controlled independently of the timing of applying the welding current to the member to be welded.

Further, in the present invention (claim 5 ), the electromagnet is mounted on an iron core with first and second electromagnetic coils, and the first electromagnetic coil is mounted on the primary side of the welding transformer. A second electromagnetic coil connected to a secondary side of the welding transformer, a voltage applied to a primary side of the welding transformer and a secondary side output of the welding transformer; Are superimposed so as not to cancel their respective polarities and input to the first and second electromagnetic coils,
During the application of the welding current, the pressurization of the member to be welded is performed in synchronism with the welding current and by synthesizing the electromagnetic force of the two coils, so that various pressing forces can be controlled.

In the present invention (claim 6 ), an AC electromagnet is used as the electromagnet, and when the AC welding current becomes zero, the pressing force by the electromagnet becomes close to zero, When the welding current is maximized, the pressing force by the electromagnet is maximized so that the resistance heating by the welding current is optimized from the relationship between the current flowing through the welding member and the contact resistance of the member to be welded. As a result, the Joule heat, that is, the thermal effect of I ² R becomes the best, and the maximum welding effect can be pursued with a constant welding machine input.

[0105]

[0106]

[0107]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. FIG. 1 is a view for explaining a spot welding apparatus according to a first embodiment of the present invention. In the figure, reference numeral 100 denotes a spot welding apparatus which performs the spot welding by computer control. A robot hand unit 101 for performing a spot welding operation, and a workpiece A
And a computer 130 for controlling the operation of the robot hand unit 101 and the output current of the power supply device, wherein the power supply device has a secondary output of A welding transformer connected to a welding electrode; and a power supply circuit for supplying a primary current having a desired waveform and frequency to a primary input of the welding transformer.
0.

Hereinafter, detailed configurations of the robot hand unit 101 and the computer 130 will be described. First, the robot hand unit 101 includes a pair of upper and lower welding electrodes 1a and 1b for applying a welding current to the member A to be welded,
An electrode support mechanism for supporting the welding electrodes so as to be able to approach and separate from each other, an actuator device for driving the support mechanism to clamp and open the member to be welded by the welding electrodes 1a and 1b, and a welding electrode during welding. A pressurizing mechanism 170 for pressurizing the first and second welding electrodes 1a and 1b, a gap adjusting mechanism 160 for adjusting a gap between the pair of welding electrodes 1a and 1b, And a fulcrum distance adjusting mechanism for adjusting the distance between the fulcrum and the fulcrum.

Here, the electrode support mechanism is a pair of upper and lower fixed arms 10 constituting the robot hand unit 101.
And the movable arm 20, the fixed arm 1
Reference numeral 0 denotes a fixed frame 12 supported by a robot body (not shown),
An electrode holder 11 has a spot welding electrode 1b fixed to its tip. A welding transformer 2 is installed at a substantially central portion on the fixed frame 12, and a driving cylinder 3 of the movable arm 20 is mounted on the upper part of the transformer 2 as the actuator device.

The gap adjusting mechanism 160 includes a trapezoidal upper side block member 161 which is slidably mounted between the rear end portion of the movable frame 22 and a portion near the center of the movable side frame 22. The upper block member 16 is formed by the left and right trapezoidal block members 163 and 164.
1, the lower block member 162 held opposite to the first block member, a rotating rod 165a with a screw for moving the left and right block members closer to or away from each other, and the lower rod member 162 fixed to the right block member 164. And a drive motor 165 that rotates.

Here, linear engagement projections 161b and 161c having an inverted trapezoidal cross section are formed on the surfaces of the bottom side and the inclined side of the upper block member 161 having a trapezoidal side surface shape. A linear engaging protrusion 162a having an inverted trapezoidal cross section is also formed on the surface of the inclined side portion of the block member 162.
On the surfaces of the inclined sides 63 and 164, there are formed linear fitting grooves 163a which are slidably fitted with the linear engaging projections 161a and 162a on the inclined sides of the upper and lower blocks.

The tip of the threaded turning rod 165a is rotatably connected to the left block member 163, and the thread forming portion of the rod is a screw formed on the right block member 164. The rod is screwed into a hole (not shown), and the rear end of the rod is connected to the drive motor 165.
(Not shown).

The pressurizing mechanism 170 includes a movable block 5 slidably mounted between the rear end portion of the fixed frame 12 and a central portion thereof, and a pedestal 172 mounted at the center of the block. A swing lever 173 swingably mounted on the upper surface of the mount 172;
The electromagnet 17 arranged in front of and near the arm
1 and a leaf spring member 174 attached to the lower surface of the lower block member 162 via a spacer 174a so as to be located directly above the gantry 172.

The electromagnet 171 is driven by the secondary current of the welding transformer as shown in FIG. 9A. A roller member 174 having a size to be in contact with the upper leaf spring member 174 and the upper surface of the lower frame 172 is attached to the distal end side of the swing lever 173. The lever 173 keeps a horizontal posture. On the upper surface of the electromagnet 171 is attached an attracting metal piece 171a for electromagnetically attracting the rear end of the swing lever 173.

At the rear ends of the lower block member 162 and the movable block 5, connecting rods 181a,
One end of 181b are rotatably supported, the both said connecting rod, the other end having a flange portion 181a _1, 181b ₁ has an inner diameter of the central portion is enlarged than the inner diameter of the end portions tubular member 182 Are connected by Here, the diameter of the flanges of the two connecting rods 181a and 181b is the same as the inner diameter of the center of the tubular member 182, so that the rear end of the movable arm 20 and the rear end of the fixed arm A small change in the height position is possible.

Further, a moving piece 161a movable along a sliding groove (not shown) formed in the movable frame 22 is attached to the front side of the arm of the upper block member 161. Pulling by driving the motor 140a incorporated in the movable frame 22,
The upper block member 16 is pushed back.
1 can be slidably moved. Similarly to the upper block 161, the sliding block 5 has a moving piece 5a that slides in a sliding groove (not shown) formed in the fixed frame 12 at the front side of the arm. A motor 140b interlocked with the motor 140a, which pulls or pushes it back, is incorporated in the frame main body. The movement mechanism between the fulcrums is connected to the motor 14.
0a, 140b, the upper block 161 and the movable block 5.

As a device for monitoring the state of formation of the spot-melted portion, a pressure-contact element disposed between the spring member 174 and the lower block 162 for monitoring the pressure-contact force of the member to be welded by the welding electrode. And a current measuring device (current monitoring device) 121 for monitoring a welding current to the member to be welded.

The computer 110 has a central processing unit (CPU) 110a for performing various judgments and controls, and various welding conditions which affect the welding state, including the material, surface condition, and thickness of the member to be welded. Storage device 11 for storing the change characteristics of the welding force and the welding current for performing the best welding in each case in the case of being set in a typical manner
0b and a data input device 110 for externally inputting specific data of the welding conditions to the CPU 110a.
d, and a display device 110c for displaying input data and the like.

Here, the CPU 110a performs the first control function based on the specific setting data Di1 of the welding condition input from the input device 110d, in which case the best welding pressure and the change in welding current are obtained. Upon receiving the pressure reading monitor signal Dp and the characteristic reading means Mcr for reading the characteristic data Dr from the storage device 110b, the welding electrodes 1a, 1
b) the pressing force control means Mma for controlling the pressurizing mechanism so that the pressing force by b coincides with the best change characteristic in that case; and the welding current monitor signal Dc. A welding current control unit Mps for controlling the power supply circuit 120 so as to match the change characteristic.

The CPU 110a has a second control function of input data D from the data input device 110d.
i, the signal Dh from the horizontality sensor, the current monitor signal Dc, the pressure contact monitor signal Dp, etc., and perform predetermined signal processing to store the storage data Dm in the storage device 110b and the display data Dd in the data display device 110c. Output or CP
The U110a control command signal C ₁ into the inside of the sequence control function Fsc, provided with input and output data processing unit Mio for outputting a control command signal C ₂ to the gap adjusting motor control means Mgm, as further third control function, control command signal subjected to Csf, control signal Csm outputs the fulcrum adjustment motor control means Msm of moving motor of the rear support point, receiving the control command signal C _2, a motor control means for outputting a gap adjusting motor control signal Cgm Air cylinder control means Mc for receiving the control command signal Csf and outputting a drive control signal Cc for the air cylinder.

Here, the sequence control function Fsc is
The sequence control of the robot hand is performed by the welding start command signal.

Next, the operation will be described. When using the spot welding equipment, the storage device of the computer stores the optimum welding conditions corresponding to various welding modes, such as the change characteristics of the welding force, the change characteristics of the welding current, and the transfer characteristics of the welding electrode. It is stored as information. This information is obtained by the operator from past welding work experience. For example, according to the material, thickness, surface condition, and the like of the member to be welded, the optimum welding conditions when they are specifically set uniformly. is there. In other words, such information is updated or newly added during the course of the welding operation, and is a know-how conventionally acquired only by skilled workers.

When an actual welding operation is performed, first, specific numerical values such as the material and thickness of the member to be welded are input to the computer from an input device 110d such as a keyboard. For, a numerical value coded in advance is input.

Then, in the computer 110, the input / output data processing means Mio receives the input data Di from the input device 110d, performs predetermined signal processing, and performs the predetermined signal processing.
b, and outputs the characteristic read command signal Di1 to the characteristic read means Mcr. At this time, the processing means M
io outputs display data Dd to the welding data display device 110c and displays the input data on its display screen. The characteristic reading means Mcr stores in the storage device 110b optimum welding conditions corresponding to the welding mode specified by the input data from among the optimum welding conditions for each of the various welding modes, for example, the welding force change characteristic Xp, the welding force, and the like. The current change characteristic Xc is read and input to the input / output data processing means Mio, the welding current control means Mps, and the press-contact force control means Mma. As a result, the input / output data processing means Mio processes the read signal and displays its change characteristics Xc and Xp on the display device 110
Graphic display on the display screen of c.

[0125] The input data processing means Mio, of the input data Di, and outputs a control command signal C ₁ to the rear support point adjustment motor control means Msm in accordance with the thickness information of the member to be welded. Then, the motor 165 of the position adjustment mechanism 160 is driven, and the left and right block members 163 and 164 approach or separate from each other, and the distance between the upper and lower blocks 161 and 162 is adjusted. Thereby, when the member to be welded is pressed by the welding electrodes 1a and 1b, the pressure by the welding electrode is applied vertically to the member to be welded.

Thereafter, when a command to start a welding operation is given from the input device 110d to the computer 110, the sequence control function Fsc receives the welding start command signal Cs from the input / output data processing means Mio and starts executing the sequence control of the robot hand. . As a result, the robot hand automatically welds a predetermined position of the sequentially-welded member to be welded.

That is, the sequence control function Fsc includes the welding current control means Mps, the pressing force control means Mma, the air cylinder control means Mc, and the rear fulcrum adjustment motor control means Msm.
, A motor 140a, 140b for adjusting the distance between fulcrums is driven by a control signal Csm from the control means Msm, and the upper block member 16 is driven.
The movable block 1 and the movable block 5 move toward the front side of the arm, and the rear fulcrum of the movable arm 20 approaches the central turning point. At the same time, the control signal Cc from the air cylinder control means Mc
Drives the pneumatic cylinder 3 to lift the movable arm 20 upward. As a result, the end of the movable arm quickly rises, and the gap between the upper and lower welding electrodes 1a and 1b opens sufficiently in a short time. In this state, the predetermined welding portion of the member A to be welded sent by another transfer device is moved up and down. Robot hand swallows between the welding electrodes.

When the positioning of the welding electrode and the welded portion of the member to be welded is completed in this way, the pneumatic cylinder 3 and the fulcrum moving motors 140a and 140b operate in reverse, and the upper and lower welding electrodes 1a are operated. , 1b sandwich the member A to be welded, and the pressing force of the welding electrode at this time is such that the direction of the pneumatic cylinder is perpendicular to the member to be welded.

In this state, the power supply circuit 120 and the pressurizing mechanism 1
The 70 electromagnets 171 are operated by control signals Cps and Cma from the welding current control means Mps and the pressing force control means Mma of the computer 110, respectively, to perform spot welding.

Hereinafter, the welding operation will be described. In a state where the member A to be welded is held between the welding electrodes 1a and 1b,
The pressure contact force of the pneumatic cylinder 3 acts on the member A to be welded, and the member to be welded can be welded. Then, in this state, the power supply circuit 120 is driven and the welding transformer 2
When a predetermined level of alternating current is applied to the secondary side, the secondary output of the transformer is used as a welding current and the welding electrodes 1a, 1b
Supplied to At this time, the electromagnet 171 of the pressing mechanism 170
, The secondary output of the transformer 2 is also supplied,
A current having the same waveform as the welding current flows through the electromagnetic coil.
As a result, the same vibration pressure as that of the welding current waveform is applied, and the welding electrodes 1a and 1b perform welding by melting and solidification of the press-contact portions.

At this time, the primary side current of the transformer 2 is monitored by the current measuring device 121, and the pressure contact force of the member A to be welded is monitored by the piezoelectric element 150, and the current monitor signal Dc is supplied to the welding current control means Mps of the computer 110 and the input. The output data processing means Mio and the pressing force monitor signal Dp are provided to the pressing force control means Mma and the input / output data processing means Mio. The welding current control unit Mps controls the power supply circuit 120 so that the monitored change in the welding current matches the optimum change characteristic of the welding current in this case read from the storage device 110b. The pressing force control means Mma controls the coil current of the electromagnet 174 such that the monitored change in the pressing force matches the optimum change characteristic of the pressing force in this case read from the storage device 110b. At the same time, the change characteristics of the monitor current and the monitor pressing force are graphically displayed on the welding data display device 110c of the computer 110.

Therefore, when the spot melting portion (nugget) is formed on the member A to be welded, even if the change in the welding current or the welding force is deviated from the optimum welding condition due to an unexpected factor, the welding is performed while correcting the change. Will be performed.

When the welding of one place is completed in this way,
The welding current is stopped, the movable arm 20 is slightly rotated by driving the pneumatic cylinder to slightly expand the gap between the upper and lower welding electrodes, and during this time, the member A to be welded is moved by another transport mechanism, and the same as above. To perform spot welding.

When spot welding is sequentially performed in this manner to complete the processing of one member A to be welded, the movable block 5 and the upper block member 161 are moved so that the rear fulcrum of the movable arm 20 is turned to the turning power point of the intermediate portion. At the same time, the pneumatic cylinder 3 is driven to widen the gap between the upper and lower welding electrodes to discharge the processed workpiece A and insert the unprocessed workpiece A.

In this way, the automatic welding of the workpiece A sequentially conveyed is performed under complete computer control.

The spot welding apparatus equipped with such a control function by computer control has the following effects. (1) The welding process in spot welding is monitored by the piezoelectric element 150 and the current measuring device 121, and the welding force of the member A to be welded during the spot welding, the change in the welding current, and the welding current conduction time are measured in these cases. Computer controlled so as to obtain the optimum change characteristics according to the welding situation,
Optimum welding can be performed according to the type, thickness, surface condition, etc. of the member to be welded, and if an abnormality occurs in the process of forming the welded portion, the change in the welding force, the change in the welding current, The energization time can be modified so that they match those in normal operation.

(2) If the computer cannot repair the abnormal formation of the welded portion only by controlling the pressing force and the welding current, for example, the member to be welded is inclined from the horizontal plane, If welding is performed in a state where vertical pressure is not applied to the member to be welded or when the tip of the welding electrode is unevenly worn, the program must be programmed to stop the line and inform the operator. Yield can be improved.

(3) Further, the movable arm 20 having the welding electrodes 1a and 1b on the front end side is supported by using the rear end portion as a rotation fulcrum and the central portion as a rotation power point. Since the central portion is lifted or lowered by the pneumatic cylinder 3, the distance from the pressure contact point (working point) of the member A to be welded by the welding electrode to the rotation fulcrum of the movable arm is determined by the length of the movable arm. Even if the thickness of the welded part fluctuates from the standard thickness depending on the type of the member to be welded and the welding location, the normal of the welding electrode surface in the axial direction of the welding electrode The deviation from the direction is small, and the member to be welded by the welding electrode can always be pressed at an angle close to the vertical direction with respect to the pressed surface of the member to be welded. Therefore, the mechanism 160 for adjusting the electrode gap interval may not be required in some cases.

(4) Since the adjusting mechanism 160 for adjusting the height of the pivot point of the rear end of the movable arm with respect to the rear end of the fixed arm is provided, the addition of the workpiece A by the movable welding electrode 1a is performed. The pressure can always be perpendicular to the press-contact surface of the member to be welded, so that good spot welding can always be performed regardless of the thickness of the member A to be welded.

(5) Further, since the distance between the pivot point at the rear end of the movable arm 20 and the pivot point at the central portion can be changed, it is possible to change the elevating speed of the movable welding electrode. For example, when inserting a member to be welded between the upper and lower welding electrodes, for example, when the upper and lower welding electrodes are largely separated so that the welding electrode does not interfere with the member to be welded, the rotation fulcrum at the rear end of the arm is moved forward. By moving it to approach the turning power point at the center thereof, the ascending and descending speed is increased, and workability can be improved.

(6) In addition, a part of the electrode support mechanism for supporting the movable arm 20 with respect to the fixed arm, the pressing force of the welding target member by the welding electrode is applied to the contact part of the structure of the electrode support mechanism. Piezoelectric element 1 to detect as generated pressure
50, the output signal Dp of the piezoelectric element is monitored as a pressing force, so that the pressing force of the member to be welded during welding can be read in real time, and the state of formation of the welded portion can be grasped at any time. It is also possible to detect abnormalities in the welding situation.

(7) In addition, the power supply unit supplies a welding current whose secondary output is connected to the welding electrode and a primary current of a desired waveform and frequency to the primary input of the welding transformer. Since the power supply circuit 120 and the power supply circuit 120 are used, the waveform of the welding current can be made suitable for each condition depending on various conditions such as the material and thickness of the member to be welded. (8) Since the current measuring device 121 for measuring the primary current of the welding transformer 2 is provided and the measured current Dc is monitored as the welding current, it is possible to read the change of the welding current during welding in real time. Thus, the formation state of the welded portion can be grasped at any time, and an abnormality in the welding state can be detected. (9) Further, the formation of the spot welded portion is performed by the electromagnet 1
Since the drive current of 71 is controlled so that the change of the current monitor signal or the pressurization monitor signal coincides with the optimum change characteristic from the characteristic reading means Mcr, the welding target A
Even if the thickness, material, etc. are different, spot welding can be performed by the welding force of the optimum change characteristic and the welding current of the optimum change characteristic that is energized for the optimum time in each case. This can be automatically repaired even if it occurs. The electromagnet 171 has a welding transformer 2
Since a part of the secondary side output is supplied, the welding electrode can be pressurized in synchronization with the welding current, and there is an effect that the pressurization of the member to be welded can be performed effectively.

(10) A spring member 174 is provided at the rear end of the movable arm.
At the same time, an electromagnet 171 that elastically deforms the spring member by the electromagnetic force is disposed near the spring member, and the elastic arm of the spring member presses the rear end of the movable arm to weld the front end thereof. The electrode 1a is connected to the workpiece A
To the movable arm 2
It can be generated without the rotation of 0, and the responsiveness and workability can be improved. In this case, since the electromagnetic vibration is applied only to the movable arm 20 and not to the apparatus main body, the rigid setting of the apparatus main body can be simplified. Further, in the apparatus of this embodiment, since the center of pressurization is a tension structure, the pneumatic cylinder can be arranged on the transformer, and the size and weight can be reduced.

(11) Further, the spring member 174 is further deformed by the pressing force of the pneumatic cylinder 3, and a constant pressing force by the pneumatic pressure of the cylinder is superimposed on the pressing force of the member A to be welded by the electromagnetic force. As a result, the pressure welding force does not become lower than a certain value, and therefore, when the pressure welding force is extremely small, it is possible to avoid excessive heat generation due to the synchronization deviation between the welding current and the pressure welding force, and to prevent the welding electrode and the welded electrode from being welded. Damage of the member can be prevented.

(12) The formation of the spot welded portion (nugget) is determined by adjusting the strength of the welding electrode and the energizing time so that the change in the current monitor signal or the pressure contact monitor signal matches the optimum change characteristic from the characteristic reading means. During welding, the formation of the welded part can be controlled to some extent, and the welding electrode and the member to be welded have some defects, for example, the welding electrode is somewhat worn or the member to be welded is Even if is slightly curved, spot welding comparable to spot welding in a normal state can be performed. When the welding current is a pulse current, the formation of the spot welding portion is determined by adjusting the pulse width and pulse interval of the welding electrode by the change of the current monitor signal and the pressure contact monitor signal. If the control is performed so as to match the change characteristics, the formation of the welded portion during welding can be controlled to some extent as described above.

Other modifications of the configuration of the spot welding device will be described. For example, if a potentiometer for detecting the displacement of the movable link portion constituting the electrode support mechanism as the displacement of the welding electrode is provided, and the pressing force of the member to be welded is calculated based on the output of the potentiometer, During welding, the displacement of the welding electrode as well as the welding force of the workpiece can be read in real time.
The formation state of the welded portion can be grasped more accurately by taking into account data based on the electrode displacement.

As shown in FIG. 7, a movable arm 20 having a welding electrode 1a at its front end is rotatably supported with respect to the fixed arm 10 with its central portion as a fulcrum and its rear end as a power point. You may do so. In this type, since the cylinder comes behind the transformer, the structure is simpler than in the case where the pneumatic cylinder 2 is arranged above the transformer, and the head is low. The whole device is larger and heavier than the one that pulls and pressurizes the central part.

Further, as shown in FIG.
Electromagnet 741 which draws a part on the tip side from the turning point
And the pressing force of the welding electrode 1a is
It may be generated by elastic deformation of 0. In this case, the mechanism for generating the pressure contact force of the welding electrode can be easily realized only by the electromagnet, and the elasticity of the arm itself is used, so that the pneumatic cylinder is used. The response of pressurization can be improved. For example, a sufficient pressurizing effect can be obtained even when the stroke of the pneumatic cylinder rod is about 0.1 mm.

Although a sound is produced when the electromagnet 171 pressurizes the AC, the AC having a normal 50 to 60 cycles or a triple frequency AC may have a simple structure. In the case of static pressurization, if the power supply of the electromagnet is set to DC which is the level of full-wave rectification, the sound is quiet, and the electromagnetic iron core may be simply formed of an iron material, so that the circuit configuration can be made relatively simple.

The load of the pressing force by the leaf spring member 171 is 1/3 to 1/3 of the total pressing force of the welding electrode of the member A to be welded.
The pressure may be set to about 1/2, and the rest may use the pressing force due to the elastic deformation of the movable arm.

Next, a spot welding apparatus according to a second embodiment of the present invention will be described. As shown in FIG. 3, this apparatus is a simplified version of the apparatus of the first embodiment, that is, the mechanism for adjusting the gap between the electrodes and the mechanism for adjusting the fulcrum are eliminated, and the pressing mechanism has a simple structure. Is the same as that of the first embodiment.

That is, reference numeral 270 denotes a pressurizing mechanism of the apparatus of this embodiment. The pressurizing mechanism 270 includes a spring cylinder 32 disposed on the fixed frame 12 via a gantry 33 and a central portion at the tip of the cylinder rod 32a. Is pivotally supported, and a swing frame 31 that raises the rear end side of the movable frame 22 at a tip end thereof, and the swing frame 3 of the fixed frame 12
1. Electromagnet 4 mounted on rear side portion via mount 40
And 1.

At the front end of the swing frame 31, a pressing roller 31b is mounted which comes into contact with and pushes up the rear lower surface of the movable frame 22, and the rear end of the electromagnet 41 An adsorbing metal piece 31a is attached to the iron core 41b for electromagnetically attracting and pulling down the rear end, and an electromagnetic coil 41a is wound around the iron core 41b.

A spring member 32b, which is elastically deformed by the downward movement of the cylinder rod 32a, is built in the spring cylinder 32, and the elastic deformation force is applied to the rear end of the swing frame 31 by the electromagnet 41. Is generated by sucking in.

An electrode holder 21a for swingably holding the upper welding electrode 1a is provided at the tip of the movable frame 22.
The electrode holder 21a has a built-in mechanism (not shown) for always supporting the welding electrode 1a in the vertical direction according to the inclination of the movable arm 20a.

In the spot welding apparatus according to the second embodiment, since the mechanism for adjusting the fulcrum and the mechanism for adjusting the gap between the electrodes in the apparatus of the first embodiment are eliminated, the operation for moving the rear fulcrum of the movable arm is performed. There is no operation for adjusting the height position of the rear end of the movable arm, and other than that, welding by computer control is performed in the same manner as in the first embodiment.

In the above-described embodiment, the welding force is generated by the electromagnet 171. However, a constant pressurization of the welding electrode is further generated by the pneumatic cylinder 3, and this is applied to the vibration pressing by the electromagnet. These pressures may be superposed and controlled by the pressing force control means Mma.
In this case, the change of the actual pressing force can be made to follow even more complicated change characteristics of the pressing force, and the pressing force can be finely controlled.

Hereinafter, other modifications of the above embodiments will be briefly described. As a first modification, for example,
In the spot welding apparatus 100 of the embodiment, in place of the power supply device, a primary side thereof is connected to a normal power source irrelevant to welding current control, and a welding transformer for outputting a welding current to a secondary side; And a power supply circuit for adjusting a secondary output of the welding transformer based on a control signal from the controller. The power supply device can adjust the voltage applied to the primary side of the welding transformer by using the electromagnet. A DC or AC electromagnet connected to the electromagnetic coil via a simple regulator, and immediately before the start of welding, the voltage applied to the primary side of the transformer is controlled by the regulator and input to the electromagnet,
Appropriate pressurization may be applied to the member to be welded. In this case, there is an effect that the welding force can be controlled independently of the timing of applying the welding current to the member to be welded.

As a second modification, for example, in the spot welding apparatus 100 of the first embodiment, the first electromagnet is connected to the primary side of the welding transformer via a voltage-adjustable regulator. A coil or a second electromagnetic coil connected to the secondary side of the welding transformer is a DC or AC electromagnet mounted on one iron core, and a voltage applied to the primary side of the transformer and a voltage of the transformer The secondary side output is superimposed so as not to cancel the respective polarities and is input to the first and second electromagnetic coils. During the energization of the welding current, the pressurization of the member to be welded is synchronized with the welding current. The electromagnetic force generated by the coil may be synthesized, and in this case, it is possible to control various pressing forces.

As a third modification, in the spot welding apparatus 100 of the first embodiment, an AC electromagnet is used as the electromagnet, and when the AC welding current becomes zero, the pressing force by the electromagnet is reduced. When the current is close to zero and the AC welding current is maximum, the pressing force by the electromagnet is maximized, and the resistance heating by the welding current causes the current flowing through the workpiece to be contacted and the contact resistance of the workpiece to be welded. The relationship may be optimal, in which case Joule heat, ie, I
²⁾ The thermal effect is the best, and there is an effect that the maximum welding effect can be pursued with a constant welding machine input.

The computer control of the above-described spot welding apparatus can be employed not only in a robot hand type spot welding apparatus but also in all spot welding machines. A general spot welding apparatus has a computer control function. This will be briefly described below as a third embodiment.

FIG. 4 shows a third embodiment of the present invention, in which a general spot welding apparatus is constructed so as to be computer-controllable, instead of a robot hand-mounted type. Here, the air cylinder 403 for pressurizing the welding electrode 1a and the welding power supply device (not shown) are driven and controlled by the computer 110 of the first embodiment, and are not shown. However, the spot welding device 403 is equipped with a pressing force monitoring device and a welding current monitoring device.

In this apparatus, the pressure contact force of the member A to be welded is controlled by the pneumatic cylinder 403. Therefore, an urging spring for urging the upper arm 401 in the pressure contact direction of the welding electrode 1a. 430 is attached to the upper surface of the arm 401 via a spacer 431, and the urging spring 43
A protruding portion 432 is provided at a portion opposing the portion 0, thereby improving the responsiveness of the pneumatic cylinder 403.

At this time, the biasing spring has a repulsive force of 0 to 100 kg with a stroke of 4 mm, a repulsive force of 100 to 300 kg with a stroke of 2.5 mm, and 300 to 300 kg with a stroke of 1.0 mm. Those capable of producing a repulsive force of 500 kg are applicable. Specifically, for example, a T-shaped welding of a thin round Al pipe uses a leaf spring having a repulsive force of 0 to 100 kg with a stroke of 3 mm, and a T-shaped welding of a thick stainless steel pipe uses 2 mm. With a rebound of 150-300 kg, and 35 for ring projection
It is preferable to use a spring of 0 to 500 kg to ensure forging pressure characteristics.

In the third embodiment having such a configuration, there is an effect by the computer control in the first and second embodiments.

Although the embodiments of the present invention have been described above, the ultimate embodiment of the present invention is the conventional one in which the above-described adjustment of the press-contact force and welding current of the member to be welded (including the adjustment of the welding current conduction time). In order to ensure the highest quality welding of parts to be welded, which was not normally possible, without thermal distortion and defective products, the processing accuracy and material status of the parts to be welded and the power supply The skill of the best welding technician in consideration of the ability of the welding and its output state, etc. needed to be appropriate for the welding work, but the experience of this sharp welding technician who has been trained for a long time in welding work The technology, that is, the welding know-how to overcome the failure factors and pass it to the computer is input in advance to the computer, and depending on the situation of the welded part of the workpiece to be welded and the surrounding area, the welding current is not necessarily supplied, the heat of the welded part, and the nugget formation And melting When the operation is not performed normally and a defective product is likely to occur, the welding current flowing through the above-mentioned welded member and the welding force of the welded portion are corrected by computer control, and if the heat is insufficient, the current is increased. The measures such as lowering the pressure are taken instantaneously. For example, when the welding electrode wears and the tip of the electrode becomes thicker, when the member to be welded is inclined with respect to the axis of the welding electrode, when there is rust or dust on the welding surface, and of course, When the cutting size, shape, material, etc. are different from the standard ones, comprehensively evaluate the welding current conduction time, pressurized condition of the member to be welded, etc., make full use of those evaluations and pass the welding It is an object of the present invention to provide software for inputting, into a computer, advanced logical know-how for instructing the best response from all the welding operations to be performed.

The application to which the spot welding apparatus and the welding method according to the present invention are applied will be briefly described below.

For example, when butt-welding a thin pipe, welding a thin pipe to a flat plate, T-welding pipes, welding when a welding material or a coating film is present between flat plates, When you want to weld even if there are granular metals, ceramics, catalysts, etc. (it was impossible with conventional spot welding technology because there were many rejected products), the minimum time, the minimum pressure and the minimum input were required. Airtight welding is required. At this time, a pulsation method in which high heat repeats intermittently in about three thousandths of a second is required. However, in the welding technology and control technology using the conventional pressurizing method, DC, inverter,
A single-phase AC method using a capacitor is impossible. Therefore, as described above, the pressurization synchronized with the waveform of the welding current, that is, the pressurization becomes zero at the zero point of the welding current, and the pressurization becomes small at a small current, and the I ² R heat is sufficiently generated. Is used.

FIG. 15 (a) shows a cover member attached to the end face of a thin pipe.
It shows the case of welding, X in the figure ₁Is a thin-walled square pipe,
Y₁Is a lid member, and the square pipe X₁Is the lower electrode 101b
And in this state, by the upper electrode 101a.
Lid member Y₁Is pressed to the pipe end face side to perform welding.

In this case, since the thickness of the square pipe is thin, Joule heat is generated more than necessary in the conventional pressurizing method, so that the waist is bent near the welded portion, resulting in poor welding. On the other hand, an intermittent state of pulsation-like heat generation of a triple frequency (three-layer input, single-phase output) is preferable, and a minimum pressurization and time and a minimum input are preferable.

The method of welding the lid member to the pipe end face is not limited to a square pipe, but may be a round pipe.
Figure 15 (b) circular lid member to the end face of the round pipe X ₂ is Y ₂
Is shown, and here also a round pipe X ₂
So that pressing is held to the lower electrode 102b, a lid member Y ₂ in the pipe upper end surface by the upper electrode 102a it is.

[0172] Next Figure 16 shows a case of welding the branch pipe to the parent pipe, drawing X ₃ is a parent pipe, y ₁ ~y ₅
Is a branch pipe welded to the parent pipe.

FIG. 16 (b) shows the XVIb-XVIb of FIG. 16 (a).
FIG. 16C is a cross-sectional view taken along line XVIc-XVIc in FIG.

Conventionally, when a branch pipe is welded to a parent pipe, R-cut processing is performed on the welded portions of both the parent pipe and the branch pipe. In addition, the thickness of the branch pipe is thinner than that of the parent pipe and spot welding is impossible, and arc welding and gas brazing have been performed.

On the other hand, according to the present method, the R-cut is not required for both welding portions, and the hermetic welding can be completed completely by spot welding, which is useful.

In FIGS. 16 (c) and 16 (d), 103
Reference numerals a and 103b denote welding electrodes for holding a branch pipe and applying a welding current thereto, respectively.
Indicates that the positive electrode 103b is a negative electrode. Therefore, in this case, it is possible to weld _two branch pipes y ₁ and y ₂ simultaneously.

[0177] Next Fig. 17 shows a case hermetically welded thin pipe end face in a plate member, reference numeral X ₄ is a flat plate member, thin pipe member Z will be spot welded thereto. FIG. 17B shows a U-shaped pipe Y ₃ attached to the flat plate member X _5.
2 shows a case where both end faces are welded.

Next, FIG. 18 shows a case where various other types of welding are performed. FIG. 18 (a) shows a case where thin pipes X ₆ and Y ₆ are butt welded, and FIG. 18 (b) shows a U-shaped pipe. Y
₈ when welding garnish pipe member X ₈ on the end face of FIG. 18 (c) to be welded of the rod X _7, Y ₇ are composed of different kinds of metal, between those weld members weldable powdered metals for both, ceramic, across the material Z ₁ such as a catalyst, shows the case of welding, especially those welded across the semiconductor material between the metal member useful as a semiconductor element Yes, there are great benefits.

FIGS. 18 (d) and 18 (e) show a case where both members are welded with an insulating film interposed between the welding members. As shown in FIG. Use
These members from both sides of the member to be welded P _1, P ₂ the 2
A set of welding electrodes 1a ₁ , 1b ₁ , 1b ₂ , 1a _{2 is} pressed and sandwiched to apply a welding current.

[0180] At this time applied to different polarities voltages to the electrodes 1a ₁ and 1b ₂ in contact with the welding member P ₁ of the upper and electrodes 1b ₁ opposed to the electrodes 1a _1, 1b _2, 1a
_A voltage is also applied to ₂ so that the opposite ones have different polarities. Thus, as shown in FIG. 18E, the nugget N is formed by breaking the insulating film R between the members to be welded, and spot welding is performed.

[0181] In such hermetic welding, unless excellent welding know-how for applying a high level of pulsation is applied, welding failures occur frequently and the welding operation cannot be performed satisfactorily.

In the method of the present invention for performing spot welding by controlling the electromagnetic pressurization and the welding current by a computer, this is possible. Although the control of the present invention has been described with respect to welding, the basic knowledge of the present invention is to input the know-how accumulated through such a long experience to a computer and perform welding that was not possible conventionally by computer control. The principle can be applied not only to welding but also to spot brazing.

The following is a supplementary explanation of the present invention. In the above explanation, for mounting on an automatic welding robot,
Although a so-called gantry in which a welding transformer and a pressure arm are integrated has been described, it goes without saying that the present invention can be applied to a normal stationary spot welding machine or an automatic dedicated welding device. At this time, a pressurizing mechanism independent of the air pressurizing mechanism is necessary to prevent the air pressurizing mechanism of the pneumatic cylinder from interfering with the air resistance and losing the structure of the spring pressurizing.

The solenoid-type electromagnet may be used in place of the empty cylinder until the welding electrode sandwiches the member to be welded, taking advantage of the long stroke property of the solenoid-type electromagnet.

One aim of the present invention is to synchronize the electromagnet with the primary input of the welding transformer, ie the drive voltage unrelated to the control of the welding current, and the secondary output of the welding transformer, ie the welding current. The present invention is to superimpose two kinds of pressurizing forces, i.e., a vibrating pressurizing force due to a drive voltage that changes due to the pressure change and a constant pressing force due to a stroke movement of a pneumatic cylinder or a solenoid.

FIG. 19 shows the waveform of such superimposed pressurization, where P _m1 is the electromagnetic force applied by the primary input of the welding transformer, P _m2 is the electromagnetic force applied by the secondary output of the welding transformer, and P _{m m} is superimposed electromagnetic pressure obtained by superposing these electromagnetic waveform, constant pressure applied by the movement of P _a or solenoid, P
_t0 is the total pressure obtained by superimposing the superimposed electromagnetic pressure P _m to the constant pressure P _a.

The three separate pressures P _m1 , P _m2 ,
P _a is the pressure mechanism so applied to the workpiece to be welded and overall may be designed from the standpoint of which a simple and reliable operation is small and light. In particular, in the electromagnet, a coil receiving a primary input of the transformer and a coil receiving a secondary output of the transformer may be collectively mounted on one iron core and wound.

For energizing the coil of the electromagnet, the primary-side applied voltage of 200 V of the transformer may be directly applied to the first coil, and the secondary output of the welding transformer may be applied to the second coil as it is.

Although the present invention has been described in the text, it can be applied not only to spot welding but also to spot brazing and special welding in which reactive materials such as ceramics, adhesives, and catalysts are mixed between joining members. Although the concept of spot welding is generally performed using a welding machine, the spot welding of the present invention includes conventional techniques such as arc welding, brazing welding, and gas welding, such as airtight welding of a container lid. This is a broad concept spot welding technology.

[0190]

As described above, according to the spot welding apparatus according to the present invention (the first aspect of the present invention), the welding process in spot welding is monitored, the press-contact forces of the upper and lower spot welding electrodes and the welding current are monitored. In addition, the welding force and the welding current of the spot welding electrode are controlled by a computer, that is, the computer controls various conditions including the material, surface condition, and thickness of the member to be welded, which affect the welding state. When the welding conditions are specifically set, the optimum change characteristics of the press-contact force for performing the best welding and the optimum change characteristics including the welding time of the welding current are stored in the storage device for each case, Based on the specific setting data of the welding conditions input by the welding worker, the optimum change characteristics in that case are determined for the welding force and welding current. The welding force and the welding current of the member to be welded are read from the storage device so that a change in one or both of the monitored welding force and the welding current coincides with these optimum change characteristics read from the storage device. Since the welding is controlled, the optimum welding can be performed according to the type, thickness, surface condition, and the like of the member to be welded. There is an effect that the welding current can be corrected so that each change matches the change characteristic at the time of normal.

If the computer cannot correct the abnormal formation of the welded portion only by controlling the pressing force or the welding electrode, for example, the member to be welded is inclined from a horizontal plane, and the pressure of the welding electrode is reduced. If welding is performed in a state where vertical pressure is not applied to the welding or when the tip of the welding electrode is unevenly worn, stop the line and program the operator to inform the operator, thereby increasing the product yield. There is an effect that can be improved.

[0192] In the above spot welding system, the
Electrode support mechanism is fixed to the end of the device, fixed to the main unit side
A fixed arm having a side welding electrode, and a rear end portion serving as a pivot point
And facing the fixed arm with the central part as the turning point
Movable arm with a welding electrode on the tip side
And the actuator device described above.
The pneumatic system is used to raise and lower the movable arm.
Or a hydraulic cylinder or solenoid, so that the distance from the pressure contact point (working point) of the member to be welded by the welding electrode to the pivot point of the movable arm can be increased to the full length of the movable arm. Even if the thickness of the welded part fluctuates from the standard thickness depending on the type of the member and the welded part, the deviation of the axial direction of the welding electrode from the normal direction of the pressure contact surface of the welded member is small, There is an effect that the pressure welding of the member to be welded can be performed at an angle close to the perpendicular direction to the pressure contact surface of the member to be welded.

[0193] Moreover, the tip of the movable arm
Equipped with an electromagnet that draws the part, the welding force of the welding electrode
Is generated by the elastic deformation of the movable arm.
Therefore, the mechanism of generating the welding pressure of the welding electrode by electromagnetic force
There is an effect that can be easily realized only by the magnet. Ma
The welding current monitoring the drive current of the electromagnet.
The change in the flow and the pressure
The spot welding is performed by controlling to match the appropriate change characteristics.
Because the part is formed, the thickness of the member to be welded and
Even if the material is different, the pressure of the optimum change characteristic
Including contact force, energizing time and pulsation timing
Perform spot welding with the optimum change characteristics of welding current
This can be done even if some abnormalities occur during welding.
There is an effect that can be automatically repaired.

[0194]

[0195]

[0196]

According to the invention (claim 2 ), in the spot welding apparatus, a spring member is attached to the rear end of the movable arm, and the electromagnet for elastically deforming the spring member by its electromagnetic force is provided. The movable arm is disposed in the vicinity of the spring member, and the rear end of the movable arm is pressed by the elastic deformation force of the spring member to press the welding electrode on the distal end side against the member to be welded. This can be generated without the rotation of, and responsiveness and workability can be improved. Also, in this case, the electromagnetic vibration is applied only to the movable arm and not to the apparatus main body, so that there is an effect that the rigid design of the apparatus main body can be simplified.

According to the invention (claim 3 ), in the spot welding apparatus, the movable arm or the spring member is further deformed by the pressure of the pneumatic or hydraulic cylinder or the solenoid, and The constant pressure contact force due to the pneumatic or hydraulic pressure of the cylinder or the electromagnetic force of the solenoid is superimposed on the vibration pressure contact force due to the force, so the pressure contact force does not become less than a certain value, so when the pressure contact force is extremely small, Excessive heat generation due to the synchronization deviation between the welding current and the press contact force can be avoided, and there is an effect that damage to the welding electrode and the member to be welded can be prevented.

[0199]

[0200]

According to the invention (claim 4 ), in the spot welding apparatus, the drive current of the electromagnet can be adjusted from the primary side of the welding transformer independent of the control of the welding current. Since the pressure is supplied to the electromagnetic coil via the adjuster and the electromagnet applies an appropriate pressure to the member to be welded, the welding force is controlled independently of the timing of applying the welding current to the member to be welded. There is an effect that can be.

Further, according to the invention (claim 5 ), in the spot welding apparatus, the electromagnet is mounted on the iron core with the first and second electromagnetic coils, and the first electromagnetic coil is mounted on the iron core. The first transformer is connected to the primary side of the welding transformer via a voltage-adjustable regulator, and the second electromagnetic coil is connected to the secondary side of the welding transformer. The secondary output of the welding transformer is superimposed so as not to negate the respective polarities and input to the first and second electromagnetic coils. During welding of the welding current, the pressurization of the member to be welded is synchronized with the welding current. In addition, since the electromagnetic force generated by the above-described quantity coil is synthesized, the pressure contact force can be controlled in various ways.

According to the present invention (claim 6 ), in the spot welding apparatus, an AC electromagnet is used as the electromagnet, and when the AC welding current becomes zero, the pressing force by the electromagnet is used. Is close to zero, and when the AC welding current is maximized, the pressing force by the electromagnet is maximized, and the resistance heating by the welding current causes the current flowing through the workpiece to be welded and the contact resistance of the workpiece to be welded. , The Joule heat, that is, the thermal effect of I ² R is the best, and the maximum welding effect can be pursued with a constant welding machine input.

[0204]

[0205]

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram for explaining a spot welding apparatus according to an embodiment of the present invention.

FIG. 2 is a block diagram illustrating a computer mounted on the spot welding apparatus.

FIG. 3 is a schematic configuration diagram for explaining a spot welding apparatus according to a second embodiment of the present invention.

FIG. 4 is a view for explaining a spot welding apparatus according to a third embodiment of the present invention.

FIG. 5 is a schematic configuration diagram for explaining a conventional spot welding apparatus.

FIG. 6 is a view for explaining the structure of a robot hand mounted on a conventional robot welding apparatus.

FIG. 7 is a view for explaining the structure of another conventional robot hand.

FIG. 8 is a waveform diagram for explaining pressurization control of a welding electrode in the robot hand.

FIG. 9 is a diagram showing a schematic configuration for explaining pressurization control of a welding electrode in the robot hand.

FIG. 10 is a view showing a specific pressing mechanism of a welding electrode in the robot hand of FIG. 5;

FIG. 11 is a view showing another specific pressing mechanism of the welding electrode in the robot hand of FIG. 5;

FIG. 12 is a diagram showing a process of forming a nugget in spot welding.

FIG. 13 is a diagram showing a form of welding failure in spot welding.

FIG. 14 is a diagram showing a change in the welding electrode, the pressure contact force, and a change in the position of the welding electrode in each welding failure mode.

FIG. 15 is an explanatory diagram of a case where a lid member is spot-welded to an end surface of a thin pipe.

FIG. 16 is an explanatory diagram of a case where a branch pipe is spot-welded to a parent pipe.

FIG. 17 is an explanatory diagram of a case where the end face of a thin pipe is spot-welded to a flat plate.

18 (a) and 18 (b) are views for explaining other welding modes, wherein FIG. 18 (a) is an explanatory view of butt welding of a thin pipe, and FIG. 18 (b) is a pipe attached to both end faces of a U-shaped pipe. FIG. 18 (c) is an explanatory view of simultaneous welding, and FIG.
FIG. 18 (d) is an explanatory view of a case in which powdery or granular metal, ceramic, a catalyst, etc. are sandwiched between two rod-shaped members to be welded, and FIG.
(e) is a sectional view before and after welding when flat plates are welded with an adhesive or the like interposed therebetween.

FIG. 19 is an explanatory diagram of a waveform of a total pressing force in which an air pressing force of a pneumatic cylinder and an electromagnetic pressing force by a primary input and a secondary output of a welding transformer are superimposed.

[Explanation of symbols]

 Reference Signs List 1a movable side welding electrode 1b fixed side welding electrode 2 welding transformer 3 pneumatic cylinder 3a cylinder rod 10 fixed arm 11 fixed side electrode holder 12 fixed side frame 20 movable arm 21 movable side electrode holder 22 movable side frame 100 spot welding device 110 computer 110a CPU 110b Storage device 110c Welding data display device 110d Data input device 120 Power supply device 121 Current measuring device (current monitoring device) 150 Piezoelectric element (pressure contact force monitoring device) 160 Height adjusting device 170 Electromagnetic pressing mechanism 180 Coupling mechanism A Member to be welded Fsc Sequence control function Mc Air cylinder control means Mio Input / output data processing means Mgm Gap adjustment motor control means Mma Pressure contact force control means Msm Rear fulcrum adjustment motor control means Mps Welding current control means Mcr Characteristics Detecting means

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI B23K 11/16 B23K 11/16 11/25 11/25 510 510 G01B 7/16 G01L 1/16 G01L 1/16 G05B 13/02 J G05B 13/02 G05F 1/00 G05F 1/00 G01B 7/18 Z (58) Fields investigated (Int. Cl. ⁷ , DB name) B23K 11/24 B23K 11/00 B23K 11/11 B23K 11/16 B23K 11/25 G01B 7/16 G01L 1/16 G05B 13/02 G05F 1/00

Claims (6)

(57) [Claims] A pair of welding electrodes for applying a welding current to a member to be welded; an electrode support mechanism for supporting the two welding electrodes so as to be able to approach and separate from each other; An actuator device for clamping and releasing the member to be welded by the electrode, a power supply device for supplying a welding current to the welding electrode, and a computer for controlling the actuator device and the power supply device; In a spot welding apparatus for performing spot welding by resistance heating of a welded portion by a welding electrode, as a device for monitoring a welding process of the welded portion,
A welding force monitoring device that monitors a welding force of the member to be welded by the welding electrode; and a current monitoring device that monitors a welding current applied to the welding electrode. When various welding conditions including the material, surface condition, and thickness of the member to be welded are specifically set, the change characteristics of the press-contact force and the change characteristics of the welding current, including the energization time, for performing the best welding. And a storage device for storing in each case, based on the specific setting data of the welding conditions input from the outside, the optimum change characteristics of the welding force in that case and the optimum change of the welding current including the energizing time. A characteristic reading means for reading characteristics from a storage device, and receiving the pressure contact force monitor signal so that a change in the pressure contact force by the welding electrode coincides with an optimum change characteristic in that case. Pressing force control means for controlling the actuator device; welding current control means for receiving the welding current monitor signal and controlling the power supply device such that a change in the welding current matches an optimum change characteristic including a current supply time in that case. structure with a door
Has a formation, the electrode support mechanism is fixed to the apparatus main body, the tip
A fixed arm with a fixed-side welding electrode and a rear end pivotally supported
As a point, the central part is a turning power point and the above fixed arm
Movable with a welding electrode on the tip side, supported opposite
Arm, and the actuator device lifts and moves the movable arm.
Sora圧A Rui to fine cuts are hydraulic cylinders or,
It is a solenoid that draws a part on the tip side from the turning point of the movable arm.
An electromagnet for controlling the welding force of the welding electrode.
The spot welding portion is formed by the elastic current of the electromagnet.
Is one of the pressing force and the welding electrode monitored above.
Or both changes are caused by pressure welding from the characteristic reading means.
Optimum change characteristics of welding force and welding current
A spot welding apparatus characterized in that the spot welding apparatus is controlled so as to coincide with the welding characteristics. 2. A spot welding apparatus according to claim 1, wherein said spring member is attached to a rear end of said movable arm.
An electromagnet for elastically deforming the spring member;
The rear end of the movable arm is pressed by the elastic deformation force of
Pressing mechanism that presses the welding electrode on the tip side of
The formation of the spot welded portion includes a drive current of the electromagnet.
Is one of the welding pressure and the welding current monitored above.
Or both changes are caused by pressure welding from the characteristic reading means.
Consistent with the optimal change characteristics of force and welding current including the energizing time
Spot welding apparatus characterized by performing such control in such a manner. 3. A spot welding apparatus according to claim 1 or 2, wherein the pressure of the pneumatic or hydraulic cylinder or a solenoid
The movable arm or spring member is further deformed by force
Then, the vibration pressure of the electromagnet
Or constant pressure welding by hydraulic or solenoid electromagnetic force
A spot welding apparatus characterized in that a force is superimposed . 4. A spot welding apparatus according to claim 1 or 2, wherein, of the connection independent of the normal power supply to the primary side welding current control
A welding transformer that outputs welding current to the secondary side,
Based on the control signal from the welding current control means, the welding torque
A power supply circuit for controlling a secondary output of the lance
Device, the voltage of the electromagnet can be adjusted on the primary side of the welding transformer
DC connected to the electromagnetic coil through a functional regulator or
An electromagnet for alternating current and the voltage applied to the primary side of the welding transformer immediately before the start of welding
Is input to the electromagnet by controlling the
A spot welding apparatus wherein an appropriate pressing force is applied to a contact member . 5. The spot welding apparatus according to claim 4, wherein the electromagnet is connected to a primary side of the welding transformer via a regulator capable of adjusting a voltage.
A first electromagnetic coil connected by
And a second electromagnetic coil connected to the secondary side of the
A DC or AC electromagnet mounted on the welding transformer, the voltage applied to the primary side of the welding transformer and the welding transformer
Do not cancel each polarity of the secondary output of the
Superimposed and input to the first and second electromagnetic coils, welding
During energization of current, pressurization of the workpiece is synchronized with the welding current.
And combine the electromagnetic force of the two coils.
Spot welding apparatus is characterized in that the. 6. The spot welding apparatus according to claim 5 , wherein an AC electromagnet is used as said electromagnet.
When the flow becomes zero, the pressing force by the electromagnet is close to zero.
When the AC welding current is maximized,
Set the applied pressure to the maximum, and
The heat flowing through the workpiece and the contact resistance of the workpiece
Spot welding equipment characterized in that it is optimized from the relationship of