JPH05293669A - Equipment and method for spot welding - Google Patents

Abstract

PURPOSE:To improve product yield by performing optimum welding according to a kind, a thickness, a surface condition, etc., of members to be welded and besides, correcting the pressure welding force and a welding current so that the respective changes are coincident with the change characteristics at the normal time when the abnormality occurs at the process of formation of a weld zone. CONSTITUTION:The pressure welding force and the welding current of the members A to be welded are monitored by a piezoelectric element 150 and a current measuring instrument 121, respectively and a driving current of an electromagnet 171 for generating the pressure welding force and the output of a welding power source circuit 120 are controlled to carry out formation of the spot weld zone so that the changes of the welding current and the pressure welding force which are monitored are coincident with the optimum change characteristics obtained from experience of an expert.

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 welded portion of a member to be welded is pressed and at the same time a welding current is applied between the members to be welded to weld the pressure-welded portion by Joule heat. Since the welding temperature is lower than that of the welding 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 the 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 with the welding apparatus main body.
1 and a lower movable arm 402 which is attached to the main body so as to be movable up and down, and welding electrodes 1a and 1b are respectively attached to the electrode holders 411 and 11b at the tips of the arms.
It is attached via 412. Then, above the electrode holder 411 at the tip of the fixed arm 401, the holder 4
Pneumatic cylinder 40 for pressurizing the welding electrode 1a via 11
3 is attached.

In such a spot welding apparatus 400,
The worker attaches the member A to be welded to the upper and lower welding electrodes 1a and 1b.
Drive device (not shown) that is placed between and performs a predetermined operation
Thus, the lower movable arm 402 is moved upward to sandwich the member A to be welded by the upper and lower welding electrodes 1a and 1b, and welding current is applied in this state to perform spot welding. At this time, the pneumatic cylinder 403 is driven by the operator's operation to appropriately control the pressure of the welding electrode, that is, the pressure contact force of the welding electrode of the member A to be welded according to the material and thickness of the member A to be welded. To do. As a result, good welding can be performed for each member A to be welded.

Besides the conventional spot welding apparatus, in which the worker performs the welding operation by the operation thereof, the members to be welded, which are installed on the manufacturing line of the factory and are automatically conveyed, are automatically transferred one after another. There is an automatic welding robot for welding.

FIG. 6 is a view for explaining such an automatic welding robot and shows a schematic structure of a spot welding robot hand. In the figure, reference numeral 500 designates a spot welding robot hand that clamps a member A to be welded by a pair of upper and lower welding electrodes 1a and 1b, and resistance-heats and welds the pressure-contacted portion with a pair of fixed arms 10. The fixed arm 10 has an arm 20, and the fixed arm 10 is attached to a fixed side frame 12 supported by a robot base (not shown) and a tip side of the frame 12, and the spot welding electrode is attached to the tip portion. 1b is fixed to the electrode holder 11. In addition, a welding transformer 2 is installed substantially in the center of the fixed-side frame 12, and the movable arm 2 is provided above the transformer 2.
0 driving cylinder 3 is attached.

The movable arm 20 is attached to the movable side frame 22 supported by the cylinder rod 3a of the drive cylinder 3 and the tip side of the frame 22,
An electrode holder 21 having a spot welding electrode 1a fixed to the tip portion thereof is formed. A support pin 22a is attached to the center of the movable frame 20, and the cylinder rod 3a of the drive cylinder 3 is connected to the support pin 22a.

Further, the fixed side and movable side frames 1
Movable blocks 513, 5 are provided at the rear ends of 0, 20 respectively.
23 is slidably mounted so that it can be slid back and forth by a pneumatic cylinder, a motor or the like, or manually.
Further, an adjusting 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 holds the member A to be welded, 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 clamp the member A to be welded, the welding electrodes A and B 1a and 1b are in a vertically pressurized state,
That is, the central axes of the upper welding electrode 1a and the lower welding electrode 1b are perpendicular to the pressure contact surface of the member A to be welded.

When a welding current is supplied from the transformer 2 between the welding electrodes 1a and 1b in this pressurized state, spot welding is performed on the member A to be welded. After that, the holding of the member to be welded by both the welding electrodes 1a and 1b is released and the welding electrodes 1a and 1b are moved to the next welding position. Therefore, the drive cylinder 3 is driven to move the movable arm 20 upward and Open the electrode slightly.

While the welding electrodes 1a and 1b facing each other are slightly open, the member A to be welded is slightly moved to align the welding electrodes 1a and 1b with the next welding position. After the completion of this alignment, 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 cylinder stops moving when is added. Then, in this state, similarly to the above, the welding current is supplied from the transformer 2 to the welding electrodes 1a and 1b to perform spot welding. After that, the above operation is repeated to perform spot welding sequentially.

In the case where the member A to be welded is discharged or inserted from between the arms 10 and 20 by welding the other portion of the member A to be welded after the spot welding is completed in this way. Is caused to slide the movable blocks 513, 523 to the arm center side 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 projected in this state, the tip ends of the movable arm 20 and the fixed arm 10 are greatly opened.

In this state, the member A to be welded is rearranged so that the desired welded 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 frame rear end side, spot welding becomes possible. At this time, if there is a change in the thickness or shape of the member A to be welded, the adjusting mechanism 504 is adjusted so that both 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 in the central part of the arm is shown, as another structure of the robot hand, a spot in which the drive cylinder of the movable arm is arranged on the rear end side of the arm as shown in FIG. There is also a welding robot hand 600.

6 is the same as that of the robot hand 500, and 604 is an adjuster for adjusting the height position of the fulcrum of the movable arm 30 arranged behind the transformer 2. This is a mechanism in which the rod with screw 604a is configured to be retractable by its rotation, and the frame 32 of the movable arm 30 is rotatably supported at the tip of the rod with screw 604a. Reference numeral 603 denotes a drive cylinder that is disposed between the rear ends of the fixed and movable arms 10 and 30 and that rotates the movable arm 30. Is supported by
The tip of the push rod 603a is pivotally supported on 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 according to the thickness t of the member A to be welded, and the position between the upper and lower welding electrodes 1a and 1b is adjusted. When the welding member A is sandwiched,
The pressure applied by the upper welding electrode 1a acts perpendicularly to the pressure contact surface of the member A to be welded.

Other welding operations are performed by the robot hand 5 described above.
However, it is different from the robot hand in that the operation of greatly opening the upper and lower welding electrodes is performed by increasing the amount of immersion of the rod 603a of the drive cylinder 603.

However, in the spot welding devices 500 and 600 as described above, since the member A to be welded is pressurized by the pneumatic cylinders 3 and 603, the pressing force is constant. For example, as shown in FIG. Output welding current I from a power source such as
_{On the} other hand, the actual welding current I is obtained by applying a constant air pressure (pressurizing force P ₁ ) indicated by the alternate long and short dash line Pc in FIG.
₁ , that is, the current flowing through the pressure-contacted portion of the member A to be welded is obtained, and in this case, a large pressing force P ₁ is applied even at the zero point of the actual welding current waveform I ₁ or a small current in the vicinity thereof. The pressure was very wasteful.

In other words, in the spot welding pressurization, when the spot welding current I has a sine waveform I ₁ , when the maximum is I _m (t = t _m ), the applied pressure P is
If P ₁ is 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 pressurizing waveform Ps like a dotted line should be obtained. However, such a pressurization control has a drawback in that the pneumatic cylinder cannot follow the change of the welding current every half cycle due to the air resistance of the cylinder, and only a rough pressurization control can be performed. It was

Therefore, the inventors of the present invention, as a device improving such a point, pressurize the member A to be welded by the pressing force having the same waveform as the welding current I _1. There is no loss of power and is efficient. Spot welding equipment has already been developed.

FIGS. 9 (a) and 9 (b) are views for explaining a spot welding apparatus having such a structure. This apparatus has the same mechanical structure as that of the spot welding apparatus shown in FIG. It is composed. In the figure, 700 is the spot welding device, 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.
The power source unit 720 composed of two, the pair of upper and lower welding electrodes 1a and 1b for sandwiching the member A to be welded under pressure, and the upper welding electrode 1a are pressed to the lower welding electrode side by the pressing force by the electromagnetic attraction force. The spot welding portion 730 has an electromagnetic force generating mechanism 740. Here, the transformer 7
No. 03 iron core 703a has a primary coil 713 on the primary side.
However, on the secondary side, in addition to the first secondary coil 723a,
The secondary coil 723b is wound.

Further, in the electromagnetic force generating mechanism 740, the exciting coil 741a is connected to the second secondary coil 723b, the electromagnet 741, the contact piece 741b of the electromagnet 741, and the fulcrum 743 is moved vertically by the contact piece 741b. It is composed of a member 742 that can be moved downward and upward to the center. Here, the primary coil 713 is connected to the single-phase AC power supply 701 via the switch circuit 702. 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.
It may be connected to a 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 by both welding electrodes, and in this state, the switch circuit 702 supplies the welding current from the transformer 703 to the welding electrodes 1a and 1b. At this time, since the exciting coil 741a of the electromagnet 741 is connected to the second secondary coil 723b of the welding transformer 703, the pressure of the member A to be welded by the electromagnet 741 is applied to the welding current of the first secondary coil 723a. Since the welding is performed by the pressing force having the same waveform Ps as that of I ₁ , spot welding can be efficiently performed without loss of pressurizing power.

However, as described above, the spot welding apparatus 70 for simultaneously applying the welding current and pressing the electrodes in synchronism therewith
At 0, it is preferable that the spot welding current I ₁ and the pressurizing waveform P _S are completely synchronized, but when the two are out of synchronization, the resistance increases when the applied pressure is zero even if the current is small. Occurrence of sparks may cause holes in the member to be welded or the electrode. Therefore, in this apparatus, as shown in FIG. 8, a constant pressure P _C0 (pressurizing force P ₀ ) by the pneumatic or hydraulic pressure of the arm driving cylinder is further applied to the welding electrodes 1a and 1b.
The constant pressure P _C0 is combined with the pressure P _S synchronized with the welding current I ₁ so as to obtain an oscillating pressure, thereby eliminating the risk of damaging the member to be welded and the electrode. ..

That is, in this spot welding apparatus 700,
The constant pressure P of the pneumatic cylinder is applied to the welding of the member A to be welded.
c (Pressure force P₀) And the above welding voltage due to the attraction force of the electromagnet.
Flow I ₁And the vibration force Ps synchronized with
Therefore, even if the vibration pressure is 0, the pressure will be 0.
And therefore the spot welding current I₁And pressure waveform P
Even if the synchronization with s is lost, there is no drastic decrease in the applied pressure.
Therefore, the occurrence of sparks due to the increase in the resistance value of the contact part
Without, it is possible to avoid making holes in the parts to be welded and welding electrodes,
There is no risk of damage to the above-mentioned members to be welded or welding electrodes. Also,
In spot welding, if pressure is applied, it does not easily generate heat.
Welding heat I²R becomes small when the pressure is large
However, with this device 700, the welding current is applied as the pressing force.
When not in use, only small pressure is applied by the pneumatic cylinder.
Therefore, the heat generation at the beginning of energization increases and good spot welding can be performed.
can get. And this made it impossible before
Spot welding of 1, copper, titanium, etc. is also possible.

FIG. 9 (b) shows a modified example of the apparatus 700 of FIG. 9 (a), in which 800 is a spot welding apparatus of this modified example, in which the iron core 803 of the welding transformer 803 is used.
a on the primary side of the first and second primary side coils 713a,
713b is wound, and the second primary side coil 713b is connected to the exciting coil 741a of the electromagnet 741 so that the electromagnet 741 is driven by the primary side 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 work depends on the skill of a skilled worker. Many. First, the disadvantages and merits of a specific configuration for realizing the pressure control of spot welding will be described in detail.

For example, as shown in FIG. 9 (a), an electromagnet 741 is used to generate the pressure contact force of the member A to be welded by the welding electrode.
If this is driven by the secondary side output of the welding transformer 703, the circuit configuration for generating the pressure contact force is AC because it is simple, and in the case of a skilled worker, the vibration noise of the electromagnet is loud. Although there is a good aspect that the strength of the pressurization can be known, the problem is that the noise is large and a silicon steel plate is necessary for the iron core of the electromagnet 741. Further, as shown in FIG. 9 (b), the electromagnet 741 is connected to the welding transformer 8 as described above.
There is also a method of driving by the primary side input of No. 03, but in this case there is a risk of electric shock, so the method shown in FIG. 9 (a) is preferable. Further, in the method of FIG. 9 (a), the second electromagnetic coil 7
23b may be omitted and the electromagnetic coil 741a may be connected to the first electromagnetic coil 723a.

If the electromagnet is driven by direct current, noise will be reduced, but a rectifier circuit and a smoothing circuit must be added, which increases the cost of the device. In some cases, the direct current for driving the electromagnet may only be full-wave rectified for the secondary welding current and may not need to be smoothed. Although this DC current has advantages, it is preferable to employ a method in which appropriate vibration pressure is applied according to the waveform of the welding current shown in FIG.

Further, when the spot welding apparatus having the transformer mounted on the welding arm as described above, that is, when the so-called gantry is small, in the case where the electromagnet 741 is mounted on the spot welding apparatus 500 as shown in FIG. 10A, for example, The electromagnetic pressure is 30 kg to 60 kg, and the stroke t ₁ by driving the electromagnet 741 of the movable arm 20 is 3 mm at maximum.
It is about 0.1 mm.

Further, as shown in FIG. 10 (b), the spring member 75
If the movable arm 20 is pulled through 0, the spring member 750 is deformed as shown by the alternate long and short dash line by driving the electromagnet 741. In this case, the movable arm 2
The stroke t ₁ by driving the electromagnet 741 of 0 may be 0. When the pressure applied by the electromagnet 741 is superimposed on the pressure applied by the pneumatic cylinder 3, the main pressure applied by the pneumatic cylinder is about 50 kg to 100 kg, and the stroke of the movable arm driven by the pneumatic cylinder is 40 mm-20.
It may be about mm. Then, when the main pressurization reaches about 50 kg, the electromagnet is energized to superimpose the electromagnet pressurization. In this way, the welding ability is improved with the same welding current by about 20 to 30%.

Further, if the electromagnet 745 is arranged on the primary side of the welding transformer 2 as shown in FIG. 11, pressure is applied by pushing up the welding arm 20, and at this time, the secondary side pocket of the welding transformer 2 is That is, the structure is not arranged in the space from the welding transformer 2 to the welding electrodes 1a and 1b, and the loss due to the 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 swinging piece having a pressing member 745c for pressing the spring member 750 at one end is provided as the electromagnet on the fulcrum portion 745a ₁ of the main body 745a. 745b is swingably attached, and the swing piece 745c is attached.
Of the movable block 513 is used.
It is arranged via a height adjustable pedestal 746. Further, in this device, the rear end of the movable arm 20 is lowered by the driving of 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. Thus, the repulsive force of the spring member is applied to the member A to be welded as a pressure applied to 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.
The repulsive force is 3 due to the deformation of the spring member due to the contact with 50.
When the weight reaches about 0 kg, it is preferable to start energizing the electromagnet 745 and superimpose electromagnetic pressure. This increases workability by 10 to 20% as in the above case.

When the member A to be welded is discharged and inserted, the rear fulcrum of the movable arm 20 is moved near the central pushing force point of the cylinder by sliding the movable blocks 513 and 523. , The moving speed of the welding electrode of the movable arm can be increased.

Next, a method of grasping the goodness or badness of the nugget that determines the welding quality, that is, the spot melting portion, from the relationship between the thermal expansion of the nugget and the change of the electromagnetic pressing force will be described. When the nugget has thermal expansion, the electromagnet works more effectively, that is, the movable arm 20 is lifted, and the flexure of the spring member 750 by the electromagnet 741 is further increased. You can know.

First, the case where the welding current is alternating current will be described. In this case, it is possible to check the state of nugget generation by measuring the increase in the pressing force of the spring member due to the expansion of the nugget, and to know the state of nugget every half cycle by the change in pressure every half cycle.

Here, as a concrete measuring method of the pressing force,
If a method of catching the change of 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. Therefore, although the nugget undergoes a change in heat expansion every half cycle, it cannot be accurately grasped. That is, due to the air resistance of the cylinder, the movable arm 402 cannot follow the expansion change in each half cycle of the nugget, and only the rough nugget formation state can be grasped.

On the other hand, when the electromagnetic force and the deformation repulsive force of the arm or spring are used to press the welding electrode as in the spot welding apparatus of 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 expansion of the nugget every half cycle can be accurately captured.

Further, even if the pulsating current obtained by full-wave rectifying the alternating current is used 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, the expansion of the nugget does not change every half cycle, but in the case where the holder 411 of the welding electrode 1a is directly pressurized by the rod of the pneumatic cylinder 403 as shown in FIG. Cylinder air resistance works, delaying the cylinder rod displacement.
The actual change in nugget expansion and the change in the welding electrode itself are slightly different.

That is, since the welding electrode 1a hardly changes 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 pressure when the electrode displacement is fixed to. Therefore, in order to know the exact nugget formation situation, the true increase in pressure must be calculated from the actual electrode displacement.

On the other hand, as shown in FIGS. 10 and 11, when the rear end of the movable arm 20 is used as a fulcrum and the central portion of the movable arm is used as a force point to rotate by the cylinder rod 3a, Unlike the device in which the holder of the welding electrode 1a is directly pressed by the rod of the pneumatic cylinder 403 as shown in FIG. 5, the rear fulcrum of the movable arm 20 is structured to be capable of minute vertical movement, Even if the cylinder rod does not move, 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 in the pressing force can be accurately grasped.

As described above, in the system in which the pressure applied to the welding electrode is detected by the displacement of the rear fulcrum of the movable arm, the pressure applied to the welding electrode is not limited to the one applied by the electromagnet, but the application by the electromagnet as in the spot welding apparatus in FIG. 6 is performed. Even with a type that does not have a pressure mechanism, it is possible to accurately read the change in the pressing force from the expansion change due to the nugget type. In other words, compared with a structure in which an electrode is rigidly directly connected to a cylinder, if the structure in which the cylinder rod and the central portion of the movable arm are connected is used, the connecting point serves as a fulcrum and the change in the applied pressure from the movement of the rear fulcrum of the movable arm. Can be read. In this case, Fig. 12 (a)-
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 judged.

However, in this case, the welding electrode is pushed up due to the expansion due to the formation of the nugget, while the welding electrode tends to go down due to the softening of the member A to be welded. It works negatively. In other words, the electrode lowering (-) action due to increased pressure and the electrode lowering (-) due to softening of the base material
Since and overlap with each other to prevent the electrode rise (+) due to thermal expansion, the nugget expansion may not be read accurately, and the reading error of the pressing force may be large.

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

In the robot hand shown in FIGS. 6 and 7, since the movable arm 20 is supported with the central portion as a force point and the rear end portion as a fulcrum, only the movable arm 20 and the fixed arm 10 need to be rigidly designed. There is no need to design the housing with high rigidity, which is advantageous for small size and light weight. When the nugget formation is read out by the displacement of the welding electrode, the displacement of the welding electrode at the tip of the movable arm can be read out as the displacement at the rear end of the movable arm according to the principle of leverage. Further, in the robot hand shown in FIGS. 6 and 7, a jaw that requires particularly high rigidity for engaging the upper and lower welding electrodes like the welding device 400 in FIG. 5, that is, a movable arm that is vertically slidable on the welding device main body. Since it does not have a structure to which the 402 is attached, the structure is excellent in structural mechanics.

Further, in the apparatus 400 of FIG. 5, since the apparatus body receives the vibration pressurization by the pneumatic cylinder 403, a strong rigid body design is required.
In the robot hand 500, the pressing force is directly applied to the electrode, and the vibration pressurization by the electromagnet is not applied to the casing mechanism (jaw), but is applied to the movable arm 20 which has the cylinder force point at the central portion and swings around this at the fulcrum. It only takes. Therefore, it is possible to easily absorb the vibration by attaching the vibration absorbing material to the attachment portion of the parts such as the pneumatic cylinder and the electromagnet.

Further, in the apparatus 500 of FIGS. 10 and 11, the welding electrode 1a is moved by the pneumatic cylinder 3 to the position where it comes into contact with the member A to be welded. It can be positioned at a distance that does. Further, as in the device of FIG. 10 (a), the pressing force may be replaced by the spring member, and the elastic deformation force of the movable arm itself may be used. In this case, when the movable arm bends and the electromagnet sticks, the elastic deformation force of the flexure is applied between the welding electrodes as a pressing force.

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. Only the pressure will increase. This increase in pressure due to the pushing force exerts the same effect as when the forging pressure is applied even when the nugget is sufficiently completed, when the forging pressure works every half cycle when the welding current is alternating current. The pressurization by the electromagnet 741 is different from the constant pressurization by the pneumatic cylinder 3 even when the welding current is increased, and the pressurization and the vibration forging pressure are increased by the increase of the welding current.

Further, for example, in the spot welding apparatus 500 of FIG. 10 (a), the movable arm 2 is driven by driving the pneumatic cylinder 3.
When the central part of 0 (pneumatic fulcrum) rises, the movable arm 2
The rear fulcrum of 0 will be pushed down in reverse, but at this time there is little force applied to the rear fulcrum, so a rear fulcrum may be provided near the pneumatic fulcrum, and the welded member A is placed between the welding electrodes. When you do, you can greatly increase the stroke. That is, for example, the cam mechanism reduces the distance between the fulcrums at the same time as the movable arm is pulled up. Then, when the tip of the movable arm is sufficiently raised, the member to be welded (base material) is inserted between the electrodes. When the welded member A is placed at the spot position,
The pneumatic electrode lowers the welding electrode and at the same time widens the distance between the fulcrums.

The upper and lower welding electrodes come into contact with the member A to be welded,
When pressure is applied to this, at this time, the rear end of the movable arm is at a height position such that the stroke t ₁ (gap of the electromagnet) of the movable arm due to the driving of the electromagnet is about 3 mm. The gap of this electromagnet depends on the deflection coefficient of the movable arm arm. After that, the electromagnet 741 is energized.

Further, a pressure meter for measuring electrode displacement is attached at the time of fixing the welding electrode, and the change in the pressing force during welding is taken as data. The pass rate can be increased by controlling the pressure based on the data.

The advantages of the pressurization control by the electromagnet system will be described below in comparison with the pneumatic system. First, the pressurization control by the electromagnet method is more effective because the applied pressure can be lowered when the welding voltage is lowered. On the other hand, in the pneumatic system, pressurization irrelevant to changes in voltage is applied, unnecessarily large pressurization is applied even when the current is 0 or small, and the heat generation of I ² R is reduced. Since air pressure is delayed by nature, precise pressure control cannot be performed,
On the contrary, when the pressurization is small, there is a state in which the current is large, and at this time, welding is defective due to sparking or the nugget being able to be cleaned. On the contrary, when the increase in current is caught and the pressurization is increased, there are times when the current is decreasing due to a gap of several cycles. At this time, the welding strength is insufficient (nugget formation is insufficient). Therefore, in the electromagnetic pressurization method, it is possible to bring a line that has been stopped due to a defect in the past into a pass range without stopping it.

Further, in the case of the air pressurization type, if the size of the nugget is caught by the electrode displacement method and the current is stopped when it reaches a predetermined position, it suddenly cools to cause a contraction phenomenon, but the pressurization is momentary. There will be a shortage. At this time, on the contrary, it is time for 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 pressure type, in the case where the electromagnet is driven by the primary side current of the welding transformer as shown in Fig. 9 (b) (circuit operation by primary side), the electromagnet is Strong energization is performed, which allows forging pressure to be applied. This forging pressure has a movable arm as shown in FIG.
Since the structure of the rear end and the front end of the movable arm is applied to the highly rigid part without applying a pressure load to the housing, it is small and lightweight as a whole, and the forging pressure depends on the product, material and shape. It is possible to change.

The forging pressure is increased depending on how the nugget is formed, that is, when the nugget is larger than a predetermined nugget,
If the nugget is a little small, you can make it smaller.

When the number of members to be welded (base material) is large, the parts are defective, or the size of the projection bellows is defective, the initial abnormalities before energization are determined by the dimension of the electrode position. Instead of reading it, the abnormalities can be known by the change in the electrode pressing force.

With this method, the presence or absence of warp or distortion of the article (member to be welded) can be known by the change of the pressing force. It is impossible to catch this slight change in pressure force and abnormalities, for example, if there is warping or distortion, because the air cylinder does not have a quick response, but the electromagnet method can increase the pressure force instantaneously, so workability is impaired. You can do without it.

Further, not only the electromagnetic force can be changed in response to the pressure abnormality, but also the welding current can be changed. In other words, in the conventional method, it is possible to pass the product whose line was stopped due to a material abnormality 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, it is advisable to extend the energization time to increase the pressure (electromagnetic force) and decrease the current.

It is impossible to read the cause and countermeasures at this moment, but a realistic expert such as warpage or distortion of the member to be welded, or defective projection, or fear of contamination by foreign matter. If you put the data that adjusts the pressing force, welding current and energizing time in the computer based on the judgment of,
With the same judgment as an expert, it is possible to deal with the instantaneous setting of welding conditions.

Furthermore, this method for commonly using electromagnetic force and pneumatic pressure not only secures the welding strength with a small input power, but also allows the pressure contact trace of the welding electrode to be obtained by the pressurization followability and the optimum characteristics of the pressurization. Can be cleaned.

In the case of the electromagnetic pressurization method, both the electromagnetic force and the welding current are normal output values, but there is rust on the surface of the base metal, there is a film, dirt is contaminated with dust or oil, etc. 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 is increased, and the change in the pressurization is small or small. When the power supply voltage decreases and the current decreases and the nugget is small or the nugget formation speed is low, the pressurization is reduced and the energization time is lengthened due to the abnormality. In this way, the nugget formation can be brought to a regular strength by increasing the welding current, extending the current-carrying time, or shortening the rest time during pulsation. Further, even if the surface condition or the contact surface of the member to be welded is abnormal, it is possible to read the change in the characteristic curve of the pressure contact force or the electrode displacement and adjust the pressurizing force until a predetermined nugget is formed, thereby changing the heat generation. Such methods include aluminum, copper,
Particularly effective for non-ferrous metals such as brass. In other words, in the past, it was possible to deal with defective welding or line stop, but it is possible to dramatically increase the pass rate without stopping the line.

Further, in the case of controlling the formation of such a nugget, not only the change of the pressure contact 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 (nugget formation state) is detected. It is even better to set the welding conditions based on the abnormal electric resistance. In other words, when controlling the thermal expansion of the nugget, the welding current decreases due to the surface coating of the welded member, and if the formation of the nugget is delayed, not only the change in the pressure contact force but also the change in the welding current is captured. It is better to solve the problem by, for example, increasing the pressure and increasing the energization time. For example, when warping or distortion of parts causes contact with parts other than the joint of the welded member to cause an extra welding current, or when the shape of the projection is large, increase the pressure to increase the current. Is good.

In some cases, it is not possible to determine whether the welding current should be increased or the duration should be increased in order to deal with the nugget formation abnormality or the like only by grasping the applied pressure. If there is an error in this judgment, welding defects will increase, but
By measuring the electric resistance, it can be seen that when the electric resistance is large, the surface condition is bad and rust, dust, and the like are considered, so it is better to increase the pressure and lengthen the welding time.

On the contrary, the electric resistance may be small depending on the shape of warpage or projection. At this time, the formation of the nugget is usually delayed only by the natural increase of the electric current, so that it is important to increase the welding current commensurate with the decrease of the electric resistance. It should be noted that, even if the welding current value is measured instead of measuring the magnitude of the electric resistance, it is possible to capture the abnormal state of the surface condition such as the film and dust. A phenomenon such as an increase in current occurs even when warping or abnormal projection occurs. In accordance with this, the magnitude of pressurization, current, energization time, pulsation, etc. can be changed as described above. However, it is difficult to perfectly match the welding current because there are many causes only by the abnormality of the electric resistance or the abnormality of the current value, and it is necessary to observe the pressure welding force and the change of the electrode in contrast.

Further, the abnormality of the electric resistance or the welding current becomes smaller than the normal one even when the welding electrode is normal but the product is inclined. Such a decrease may occur when the surface of the base material is defective as described above. In this case, if the welding pressure of the member to be welded is increased as planned and the welding current energization time is lengthened, the tip shape of the electrode is badly attached, the electrode trace becomes very dirty, and the welding strength becomes poor. When the change characteristic of the pressure contact force of the welding electrode at this time is also examined at the same time, it can be seen that the pressure contact force has the change characteristic (curve A ₁ ) shown in FIG. 14 (a), other than the standard characteristic (curve S ₁ ). In the case of (curves A ₁ , B ₁ , C ₁ ), there is a problem in the contact state between the welding electrode and the member A to be welded as shown in FIGS. 13 (a) to 13 (c), and it is necessary to take appropriate measures. There is.

Here, FIG. 13 (a) shows that when the member A to be welded is not perpendicular to the axis of the welding electrode, FIG. 13 (b), (c)
The member A to be welded is normally arranged, but the welding electrode 1
When the tips of a and 1b are worn out, especially in FIG.
FIG. 13 (c) shows the case where the opposite parts of the upper and lower electrodes are abraded in the same manner, and FIG. 13 (b) shows the case where the abraded parts of the upper and lower electrodes are different, and FIG. The characteristic curves A ₁ , C ₁ , and B ₁ in () correspond to each other.

Such an abnormality around the welding electrode can be immediately recognized by a person, but when the welding operation is unmanned and automated, from the characteristic curves A _{1 to} C ₁ shown in FIG.
Determine which of (a) to (c) is abnormal. However, in the case where the above waveforms are dealt with, it is impossible to respond promptly, and even if it is possible to determine which of the characteristic curves A _{1 to} C ₁ is after the welding is completed, this alone is useful as a countermeasure against defects. Absent. In this case, since the electric resistance (welding current) is measured at the same time, the change characteristic curves A _{2 to} C ₂ of the electric resistance shown in FIG. In the case of (change characteristic curve S ₂ ), the horizontality of the welded member A can be corrected in real time by determining which of the pressurizing characteristic curves A _{1 to} C ₁ . Here, when the pressurizing characteristic is the 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 mounting an automatic polishing machine. Monitoring this electric resistance or welding current value and automatically recovering the welding state to the normal state based on this is somewhat more responsive and reliable than the case of monitoring the pressure contact force, but it is certain. , I don't have enough time to get the perfect control.

In addition, the welding conditions (added in FIGS. 13 (a) to 13 (c))
Pressure change characteristic curve A₁~ C₁) Is the displacement of the welding electrode
The distance of the change in the height position of the welding electrode on the movable arm side is measured.
When viewed from the distance (dimension), as shown in Fig. 14 (c),
Characteristic curve A of pressure force of₁~ C₁Electrode displacement corresponding to
Characteristic A₃~ C₃Is obtained. That is, for each characteristic, the electrode is
The large amount of movement occurs and eventually equilibrates (with thermal expansion) and gradually
Changes greatly and decreases with cooling (stopping electricity). this
If you capture the first large change, the change in the pressing force will be the characteristic curve.
A₁Or characteristic curve B ₁Or characteristic curve C₁You can judge whether
Stop the in and turn on the characteristic curve A₁In the case of,
Correct the clamped state and change the characteristic curve B₁Or C₁In the case of
Replace or automatically repair the welding electrode. The characteristic curve A
₁Even if there is an abnormal welding condition,
It may be modified to the location. Furthermore, the current is stopped at the point t at the beginning of welding.
Therefore, when welding after correcting the above abnormal conditions, there is a slight
The welding current is about to increase, so apply a slightly stronger welding current again.
If it is poured for the first time, sufficient welding strength can be obtained.

Appropriate welding conditions can be automatically obtained by constantly detecting the three factors described above, namely, the change in pressure contact force, the change in electric resistance or welding current, and the change in electrode. It is the instantaneous adjustment of the pressing force, the adjustment of the welding current, the adjustment of the length of the energization time, and the adjustment of the interval of the energization of the pulsation when the welding current is a pulse current. Therefore, until now the line is stopped as a defect and most of the items that were discarded as a defect fall within the acceptable range. However, discard the parts that are defective enough to be corrected. In this way, by making full use of the welding pressure, welding resistance, welding current value, and welding time by detecting pressure contact force, electrical resistance, and electrode displacement, many products that had been rejected until now can be passed very efficiently. Can be Note that the characteristic waveform diagram used in the above description shows the trend as follows even if there are differences in instantaneous values in terms of AC current and DC current.
You may understand that it is as above.

Further, in addition to the above-mentioned three major welding conditions of pressure contact force, welding current, and energization time, there are factors that are indispensable for welding, such as the electrode material, size, tip shape and surface contamination. To do better, this needs to be constantly monitored. Further, the impedance Z of the secondary circuit of the welding transformer is Z = R + jX, but of the actual resistance R, the contact resistance of each member that constitutes the welding current circuit is also important, and this can be stabilized by sufficient tightening. Otherwise, the measured welding current data will be incorrect. Similarly, the interposition of a magnetic material in the welding current circuit also becomes a major variable, and if this is not taken into consideration, the data will be confused. In this way, the contact resistance of each part and the interposition of the magnetic substance give important results to the measurement of the welding current and the electric resistance together with the change of the power supply voltage, and therefore, they must be constantly monitored. Also, regarding the member to be welded that enters the circuit of welding current, the condition, material,
If various conditions such as shape, surface condition, angle with electrode, contact condition, etc. are not regularized, it may cause welding failure.

The above influences the electric resistance, the welding current, the heat generation, the vibration, the displacement, etc., so that it is necessary to always consider these influences in the measurement of the data. After that, it is necessary to change the correspondence of welding conditions based on correct judgment of data to obtain the best acceptance status. Despite the fact that this requires years of experience and intuition, the number of skilled workers with such ability is decreasing year by year. For this reason, by putting the judgments and responses of these excellent technicians in the computer, anyone can perform welding comparable to that of excellent technicians.

This is the purpose of the present invention. That is, the optimization data of the welding condition is made with an accurate sense like a god with a sharp edge, the cause of the welding condition which does not match this is accurately grasped, and the welding condition is Electric resistance, welding current fluctuations and heat generation (including nugget formation) errors that do not occur because of non-optimization do not cause welding defects, that is, when the welding conditions are not optimal In order to put the product in the acceptable range, it is necessary to change the welding current, the electrode pressure contact force, and the energizing time, in order to handle them.

For example, when the welding current decreases, the heat generation naturally decreases and the nugget becomes insufficient. However, if the pressure is appropriately lowered at this time, the heat generation is promoted by I ² R and the necessary nugget strength can be maintained. Of. If you still run out of nuggets, increase the power-on time. Also, as for the electrode's crevice, the area in contact with the member to be welded increases, and the nugget formation is insufficient with the same initial welding current, which affects the welding strength.
The pressurization must rise correspondingly, but the data about the accurate judgment response of a technician like God is stored in a computer, taking into account the change curves from the beginning of electrode replacement to the time of the next electrode replacement. If you put it in, unlike the conventional welding method where the rate of failure is large only by setting reliable conditions, most of welding defects will be resolved by the accurate judgment and response of this welding experienced person, and the conveyor may be stopped. It is possible to prevent waste of materials and energy by making defective products.

The present invention has been made on the basis of such research on conventional welding technology, and relates to a basic technology for putting the know-how of welding technicians into a computer. And a spot welding apparatus and a spot welding method capable of automatically performing welding that is comparable to welding with the know-how of a welding technician under the best welding conditions that could not be realized by reliable correspondence. With the goal.

The object of the present invention will be described in detail below. (1) Since the control of the pressure contact force of the member A to be welded cannot be instantaneously controlled by the conventional pneumatic control or hydraulic cylinder control, the strength of the welding current is The electromagnetic force has such a function that it is connected to the strength of the pressure contact force, and in particular, depending on the current waveform of, for example, 50 Hz, the pressure is weak when the current is zero and the pressure is highest at the highest current value. By adopting force pressurization, Joule heat (I ² R) is effectively used to achieve overall compactness and light weight. (2) During spot welding, the pressure applied by the welding electrode is applied vertically to the member A to be welded. (3) During spot welding, the stroke of the welding electrode, that is, the lifting stroke of the welding electrode is minimized to increase the workability of the spot welding operation, and when the member to be welded is inserted between the welding electrodes, the member to be welded and the welding electrode are 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 quick response to the electromagnet's pressurizing operation, various pressurizing operations are possible by the structure that can be performed without moving the rod of the pneumatic cylinder that moves up and down the welding electrode during pressurizing operation. To realize the characteristics. (5) Enable to automatically change the lifting speed of the welding electrode. (6) It is possible to automatically change the pressure applied by the pneumatic cylinder during welding. (7) Detect the state of nugget formation during welding. (8) It is possible to control the pressure contact force according to the formation condition of the nugget. For example, when the nugget formation 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 formation of voids and pinholes in the nugget portion. To do so. On the contrary, when the nugget is small and the forming speed is small, the pressing force is decreased to increase the current, and when it is still insufficient, the energization time is lengthened to increase the amount of heat generation. (9) It also enables automatic control of the welding current according to the nugget formation. For example, it is possible to detect a change in electric resistance or a welding current, and appropriately perform one or both of a welding current increase / decrease control and a conduction time control according to the change. (10) Detecting the tip shape of the welding electrode, the sandwiching state of the member to be welded by the welding electrode, and the like, and based on this, make it possible to automatically perform some degree of failure recovery processing. For example, relatively simple trouble recovery such as polishing and repair of the welding electrode tip can be automatically performed, and the manufacturing line can be automatically stopped so that the operator can be instructed. As described above, the object of the present invention is to provide a spot welding apparatus and a spot that can automatically perform the adjustment of the pressing force, the increase / decrease adjustment of the welding current, and the energization time adjustment, which are always related to each other so that the best welding is possible. To obtain a welding method.

[0076]

A spot welding apparatus according to the present invention (claim 1) is an apparatus for sandwiching a member to be welded by a pair of welding electrodes by pressure welding and spot welding the pressure welding portion by resistance heating. In the above, as a device for monitoring the welding process of the pressure contact portion, a pressure contact force monitoring device that monitors the pressure contact force of the member to be welded by the welding electrode, and a current monitor device that monitors the welding current applied to the welding electrode. And a computer for controlling an actuator device for moving up and down the welding electrode and a power supply device for outputting the welding current, and the computer has a material for the member to be welded, which influences the welding state. , Characteristics of pressure contact for best welding when various welding conditions including surface condition and thickness are set concretely. 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,
Based on specific setting data of the welding conditions input from the outside, characteristic reading means for reading the optimum change characteristic of the pressure contact force and the optimum change characteristic of the welding current including the energization time from the storage device in that case; In the case where the welding current is received, the pressure welding force monitor signal is received, and the welding current monitor signal is received, and the pressure welding force control means for controlling the actuator device so that the pressure welding force by the welding electrode matches the best change characteristic in that case. Of the welding current control means for controlling the power supply device so as to match the optimum change characteristics including the energization time.

In the spot welding apparatus of the present invention (claim 2), the main portion of the electrode supporting mechanism for supporting the welding electrodes so that they can approach and separate from each other is attached to the tip end fixed to the apparatus main body side. A fixed arm having a fixed-side welding electrode, and a movable arm supported so as to face the fixed arm with the rear end portion as a fulcrum of rotation and the central portion as a turning power point, and having a welding electrode at the front end side, The actuator device is a pneumatic or hydraulic cylinder or a solenoid type electromagnetic device for lifting and lowering the central portion of the movable arm.

In the spot welding device according to the present invention (claim 3), the pressure contact force monitoring device is incorporated in a part of an electrode support mechanism, and the pressure contact force of a member to be welded by the welding electrode is applied to the electrode. It has a piezoelectric element for detecting the pressure generated at the contact portion of the structure of the support mechanism, and is configured to monitor the output signal of the piezoelectric element as a pressure contact force.

In the spot welding apparatus according to the present invention (claim 4), the pressure contact force monitoring device detects the displacement amount of the movable link portion constituting the electrode support mechanism as the displacement amount of the welding electrode. It comprises a potentiometer and a pressure contact force calculating means for calculating the pressure contact force of the member to be welded based on the output of the potentiometer.

In the spot welding apparatus according to the present invention (claim 5), the power supply device includes a welding transformer whose secondary side output is connected to the welding electrode, and a primary side input of the welding transformer. And a power supply circuit for supplying a primary current having a desired waveform and frequency, and the current monitor device is a current measuring device for measuring the primary current.

According to a sixth aspect of the present invention, in the spot welding apparatus, an electromagnet for attracting a portion of the movable arm on the tip side from the rotational power point is provided, and the pressure contact force of the welding electrode is changed by the elasticity of the movable arm. The spot welding portion is formed by deformation so that the change of one or both of the pressure contact force and the welding current monitoring the drive current of the electromagnet is the optimum change characteristic of the pressure contact force from the characteristic reading means. The welding current is controlled so as to match the optimum change characteristics including the energization time.

In the above spot welding apparatus, the present invention has a spring member attached to the rear end of the movable arm and an electromagnet that elastically deforms the spring member by its electromagnetic force. , A pressing mechanism that presses the rear end of the movable arm by the elastic deformation force of the spring member and presses the welding electrode on the tip side of the movable arm against the member to be welded, and the formation of the spot welded portion is performed by the drive current of the electromagnet. Is controlled so that the change in one or both of the pressure contact force and the welding current being monitored coincides with the optimum change characteristic of the pressure contact force from the characteristic reading means and the optimum change characteristic of the welding current including the conduction time. It was done like this.

In the spot welding apparatus according to the present invention (claim 8), the movable arm or the spring member is further deformed by the pressure of the air pressure or the hydraulic cylinder or the solenoid, and the vibration pressure welding by the electromagnetic force is performed. A constant pressure contact force due to the pneumatic pressure or hydraulic pressure of the cylinder or the electromagnetic force of the solenoid is superimposed on the force.

In the spot welding apparatus according to the present invention (claim 9), the welding current is AC power or DC power, and the spot welding portion is formed by one of the strength of the welding electrode and the energization time, or Both of them are controlled so that changes in one or both of the pressure contact force and the welding current being monitored coincide with the optimum characteristic change of the pressure contact force from the characteristic reading means and the optimum change characteristic of the welding current including the energization time. It's something that you do.

According to the present invention (the tenth aspect), in the spot welding apparatus, the welding current is a pulse current, and the spot welding portion is formed by using one or both of the pulse width and the pulse interval of the welding electrode. Control is performed so that the change in one or both of the pressure contact force and the welding current being monitored coincides with the optimum characteristic change of the pressure contact force from the characteristic reading means and the optimum change characteristic of the welding current including the energization time. It is the one.

According to the present invention (the eleventh aspect), in the above spot welding apparatus, a primary side thereof is connected to a normal power source unrelated to welding current control, and a welding transformer for outputting a welding current to the secondary side, A power supply device comprising a power supply circuit for adjusting the secondary output of the welding transformer based on a control signal from the welding current control means, the electromagnet, the applied voltage to the primary side of the welding transformer, This electromagnet is a DC or AC electromagnet connected to its electromagnetic coil via an adjuster capable of adjusting the voltage, and the applied voltage to the primary side of the welding transformer is controlled by the adjuster immediately before the start of welding. Is input to apply appropriate pressure to the member to be welded.

In the spot welding apparatus of the present invention (the 12th aspect), the electromagnet and a first electromagnetic coil connected to the primary side of the welding transformer via a regulator capable of adjusting the voltage. , A second electromagnetic coil connected to the secondary side of the welding transformer as an electromagnet for direct current or alternating current mounted on one iron core, and
The applied voltage to the secondary side and the secondary side output of the welding transformer are superimposed on each other so as not to cancel their polarities, and then input to the first and second electromagnetic coils to apply the welding target member while welding current is being supplied. The pressure is synchronized with the welding current and the electromagnetic force generated by the coils is combined.

In the spot welding apparatus according to the present invention (claim 13), an AC electromagnet is used as the electromagnet, and when the AC welding current becomes zero, the pressure applied by the electromagnet is close to zero. When the AC welding current is maximized, the pressure applied by the electromagnet is maximized, and resistance heating by the welding current is optimal from the relationship between the current flowing through the welded member and the contact resistance of the welded member. It is designed to be

In the spot welding method according to the present invention (corresponding to claim 14), various welding conditions that affect the welding state, including the processing accuracy of the member to be welded, the material, and the ability of the welding power source, are specifically stated. In order to perform the best welding in the set welding mode, the optimum change characteristic of the welding force and the welding current are applied based on the comprehensive judgment based on the experience of the welding engineer for each welding mode. Obtained as optimum change characteristics including time, these optimum change characteristics are stored in a storage device of a computer, and at the time of welding, specific setting data of the above welding conditions is input to the computer from the outside to perform one welding. A mode is specified, the optimum change characteristic of the pressure contact force and the optimum change characteristic of the welding current including the energization time in this characteristic welding embodiment are read out from the storage device, and the spot During the contact, one or both of the pressure contact force and the welding current are controlled by the pre-programmed control means of the computer, and the optimum change characteristic of the pressure contact force in such a case, the optimum change of the welding current including the energization time. Feedback control is performed so as to match the characteristics.

The present invention (the structure according to claim 15) is, in the spot welding method, as a mode for carrying out the welding, one in which thin-walled pipes are butt-welded together, one in which the end faces of the thin-walled pipes are welded to a flat plate, and one in which thin-walled pipes are welded. Welding the end face to the side of the pipe in a T shape, welding opposite members to be welded with an adhesive or a coating film interposed between them, of the material containing metal, ceramic, catalyst on the joint surface It includes one for welding a member to be welded having a powder or granular material.

[0091]

In the present invention (the one according to claim 1),
The welding process in spot welding is monitored by monitoring the pressure contact force and welding current of the upper and lower spot welding electrodes, and the pressure contact force and welding current of the spot welding electrodes are controlled by a computer, that is, in the computer, Optimum change characteristics of welding force and welding current for the best welding when various welding conditions such as material, surface condition, and thickness of the welded member that affect the welding state are specifically set The optimum change characteristics including the energization time are stored in the storage device for each case, and the optimum change characteristics in that case are determined based on the specific setting data of the welding conditions input by the welding operator. The pressure contact force and welding current are read out from the storage device, and changes in one or both of the pressure contact force and welding current monitored above are detected. Since the pressure contact force and the welding current of the member to be welded are controlled so as to match these optimum change characteristics read out from the memory device, it is optimal 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 pressure contact force and the welding current can be modified so that their respective changes match the normal change characteristics.

In the case where the formation abnormality of the welded portion cannot be repaired only by controlling the pressure contact force and the welding electrode in the computer, for example, the member to be welded is inclined from the horizontal plane, and the pressure of the welding electrode is applied to the member to be welded. If welding is being performed in a state where vertical pressure is not applied or the tip of the welding electrode is worn unevenly, the product yield is improved by programming the line to stop and notify the operator. Can be improved.

Further, according to the present invention (the second aspect), the movable arm having the welding electrode on the tip side is supported with the rear end portion as a fulcrum of rotation and the central portion as a rotational power point. Since the central part of the arm is rotated and lifted or pulled down by an actuator device such as pneumatic or hydraulic cylinder,
The distance from the pressure contact (point of action) of the member to be welded by the welding electrode to the fulcrum of rotation of the movable arm can be made large to the full length of the movable arm. Even if the thickness fluctuates with respect to the standard thickness, the deviation of the axial direction of the welding electrode from the normal direction of the pressure contact surface of the member to be welded is small, and the pressure welding of the member to be welded by the welding electrode is always performed. Can be performed at an angle close to the vertical direction with respect to the pressure contact surface of.

In the present invention (the third aspect), the pressure contact force of the member to be welded by the welding electrode is applied to a part of the electrode supporting mechanism for supporting the movable arm with respect to the fixed arm by the electrode supporting mechanism. Since a piezoelectric element that detects the pressure generated in the contact portion of the structure is incorporated and the output signal of the piezoelectric element is monitored as the pressure contact force, the pressure contact force of the welding target member during welding can be read in real time. Therefore, the formation state of the welded portion, that is, the pressure contact force of the member to be welded, the change in welding current, and the energization time can be grasped at any time, and the abnormality in the welding state can be corrected to obtain a passing product.

Further, in the present invention (claim 4), a potentiometer for detecting the displacement amount of the movable link portion constituting the electrode support mechanism as the displacement amount of the welding electrode is provided, and based on the output of the potentiometer. Since the pressure contact force of the welded member is calculated, it is possible to read not only the pressure contact force of the welded member but also the displacement of the welding electrode in real time during welding, and more accurately grasp the formation state of the welded part. can do.

In the present invention (claim 5), the power supply device has a welding transformer whose secondary side output is connected to the welding electrode and a desired waveform for the primary side input of the welding transformer. And the power supply circuit for supplying the primary current of the frequency, the waveform of the welding current can be adapted to each condition depending on various conditions such as the material and thickness of the member to be welded. Further, since the current measuring device for measuring the primary current of the welding transformer is provided and the measured current is monitored as the welding current, the change of the welding current during welding can be read in real time, and the formation of the welded portion. The situation can be grasped at any time, and an abnormality in the welding situation can be detected.

According to the present invention (the sixth aspect), an electromagnet for attracting a portion of the movable arm on the tip side from the turning point is provided, and the pressure contact force of the welding electrode is generated by elastic deformation of the movable arm. Therefore, the mechanism for generating the pressure contact force of the welding electrode by the electromagnetic force can be easily realized only by the electromagnet. Further, the drive current of the electromagnet is controlled so that changes in the welding current and the pressure contact force being monitored match the optimum change characteristics from the characteristic reading means,
Since the spot welding portion is formed, even if the thickness and material of the member to be welded are different, spot welding can be performed with the optimum pressure contact force and welding current in each case, and during welding. Even if some abnormality occurs, it can be automatically repaired.

According to the present invention (claim 7), a spring member is attached to the rear end of the movable arm, and an electromagnet for elastically deforming the spring member by its electromagnetic force is arranged in the vicinity of the spring member. Since the rear end portion of the movable arm is pressed by the elastic deformation force of the spring member so that the welding electrode on the tip side of the movable arm is brought into pressure contact with the member to be welded, it is possible to apply an electromagnetic force without rotating the movable arm. Can be generated, and responsiveness and workability can be improved. Further, in this case, since the electromagnetic vibration is applied only to the movable arm and not to the apparatus body, the rigid body design of the apparatus body can be simplified.

In the present invention (the eighth aspect), the movable arm or the spring member is further deformed by the pressure of the pneumatic pressure or the hydraulic cylinder or the solenoid, and the vibration pressure contact force of the electromagnetic force causes the cylinder to move. Since the constant pressure contact force by pneumatic or hydraulic pressure or the electromagnetic force of the solenoid is superimposed, the pressure contact force does not fall below a certain value, and therefore, when the pressure contact force is extremely small,
It is possible to avoid excessive heat generation due to a synchronism shift between the welding current and the press contact force, and prevent damage to the welding electrode and the member to be welded.

In the present invention (claim 9), the welding current is AC power or DC power, and the strength and weakness of the welding electrode and the energization time are the characteristics of changes in the current monitor signal and the pressure contact force monitor signal. Since the formation of the spot welded portion is performed by controlling so as to match the optimum change characteristic from the reading means, the formation of the welded portion can be controlled to some extent during welding, and the welding electrode or the member to be welded can be controlled. Some troubles, such as some wear of the welding electrode,
Even if the member to be welded is slightly curved, it is possible to perform spot welding comparable to spot welding in a normal state.

In the present invention (the tenth aspect), the welding current is a pulse current, and the welding current monitoring the pulse width and the pulse interval of the welding electrode and the change in the pressure contact force have the above characteristics. Since the spot welded portion is formed by controlling so as to match the optimum change characteristic from the reading means, the formation of the welded portion can be controlled to some extent during welding as described above.

Further, according to the present invention (the eleventh aspect), the drive current of the electromagnet is supplied from the primary side of the welding transformer irrelevant to the control of the welding current through the regulator capable of adjusting the voltage to the electromagnetic coil. Since it is supplied to the member to be welded by the electromagnet, the pressure contact force can be controlled independently of the timing of applying the welding current to the member to be welded.

Further, the present invention (according to claim 12)
In the above, in the electromagnet, the first and second electromagnetic coils are attached to an iron core, and the first electromagnetic coil is connected to the primary side of the welding transformer through a voltage adjustable regulator, and
The electromagnetic coil is connected to the secondary side of the welding transformer, and the voltage applied to the primary side of the welding transformer and the secondary side output of the welding transformer are superposed so as not to cancel their polarities. And input to the second electromagnetic coil,
While the welding current is being supplied, the pressing of the member to be welded is performed in synchronism with the welding current and by combining the electromagnetic forces generated by the coils, so that various pressure contact forces can be controlled.

In the present invention (the thirteenth aspect), 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, and the AC When the welding current is maximized, the pressure applied by the electromagnet is maximized, and the resistance heating by the welding current is optimized from the relationship between the current flowing through the welded member and the contact resistance of the welded member. Therefore, 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.

In the present invention (according to claim 14), welding in which various welding conditions affecting the welding state, including the processing accuracy of the member to be welded, the material, and the ability of the welding power source, are specifically set. In order to perform the best welding in the embodiment, the optimum change characteristics of the welding force and the optimum change of the welding current including the energization time are determined based on the comprehensive judgment based on the experience of the welding engineer for each welding embodiment. Obtained as characteristics, these optimum change characteristics are stored in a storage device of a computer, and at the time of welding, specific setting data of the above-mentioned welding conditions is input to the computer from outside to specify one welding mode, The optimum change characteristic of the pressure contact force and the optimum change characteristic of the welding current including the conduction time in the specified welding embodiment are read out from the storage device, and during the spot welding, The pre-programmed control means of the computer matches one or both of the above-mentioned pressure contact force and welding current with the optimum change characteristic of the pressure contact force and the optimum change characteristic of the welding current including the energization time in that case. Since the feedback control is performed as described above, it is impossible to realize with the functions of the conventional welding machine and the uniform welding method. In any of the welding modes, it can be realized by a computer, and it is possible to easily perform welding work comparable to welding with the know-how of a welding expert.

Further, the present invention (according to claim 15)
In the above welding embodiment, thin-walled pipes are butt-welded with each other, end faces of the thin-walled pipes are welded to a flat plate, end-faces of the thin-walled pipes are welded to the side faces of the pipe in a T-shape, and opposite welding targets are used. Since it includes welding of members with an adhesive or a coating film interposed between them, welding of members to be welded having a powdery or granular material of metal, ceramic, or catalyst-containing material on the joint surface, In particular, the yield can be improved in the above-described welding implementation mode in which many products were rejected by the conventional spot welding technique.

[0107]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram for explaining a spot welding apparatus according to a first embodiment of the present invention. In the figure, reference numeral 100 is a spot welding apparatus for performing the spot welding by computer control. Robot hand unit 101 for performing spot welding work and welded member A
And a computer 130 for controlling the operation of the robot hand section 101 and the output current of the power supply device. The power supply device has a secondary side output as described above. A welding transformer 2 connected to a welding electrode, and a power supply circuit 12 for supplying a primary current of a desired waveform and frequency to a primary side input of the welding transformer.
It is composed of 0 and.

The detailed configurations of the robot hand unit 101 and the computer 130 will be described below. 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 that supports the two welding electrodes so that they can approach and separate from each other, an actuator device that drives the support mechanism to hold and release the member to be welded by the two welding electrodes 1a and 1b, and a welding electrode during welding. A pressurizing mechanism 170 for pressurizing 1a, 1b, a gap adjusting mechanism 160 for adjusting the gap between the pair of welding electrodes 1a, 1b, and a rotary fulcrum of the robot hand for moving and turning power point. And a fulcrum distance adjusting mechanism for adjusting the distance between

Here, the electrode supporting mechanism includes a pair of upper and lower fixed arms 10 constituting the robot hand section 101.
And the movable arm 20, and the fixed arm 1
0 is attached to the fixed-side frame 12 supported by a robot base (not shown) and the tip side of the frame 12,
It comprises an electrode holder 11 having a spot welding electrode 1b fixed to its tip portion. A welding transformer 2 is installed in a substantially central portion of the fixed frame 12, and a driving cylinder 3 of the movable arm 20 is attached to the upper portion of the transformer 2 as the actuator device.

Further, the gap adjusting mechanism 160 includes an upper side block member 161 having a trapezoidal side surface isosceles shape, which is slidably mounted between the rear end portion of the movable side frame 22 and a portion in the vicinity of the center thereof, and the side surface isosceles legs. The upper block member 16 is formed by the trapezoidal left and right block members 163 and 164.
1, a lower block member 162 that is held so as to be opposed to each other, a turning rod 165a with a screw for moving the left and right block members close to or away from each other, and the right side block member 164. It is composed of a drive motor 165 that is rotationally driven.

Here, linear engaging 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 side isosceles trapezoidal-shaped upper block member 161, and the above-mentioned lower side. A linear engagement protrusion 162a having an inverted trapezoidal cross section is also formed on the surface of the inclined side portion of the block member 162, and the left and right side surface isosceles trapezoidal block member 1 is formed.
On the surfaces of the slanted sides of 63 and 164, linear fitting grooves 163a that slidably fit with the linear engaging protrusions 161a and 162a of the slanted sides of the upper and lower blocks are formed.

Further, the tip end portion of the screwed rotating rod 165a is rotatably connected to the left block member 163, and the screw forming portion of the rod is a screw formed on the right block member 164. It is screwed into a hole (not shown), and the rear end side of the rod is the drive motor 165.
Is connected to a rotary shaft (not shown).

The pressing mechanism 170 includes a movable block 5 slidably mounted between a rear end portion of the fixed frame 12 and a central portion thereof, and a mount 172 placed at the center of the block. A swing lever 173 swingably attached to the upper surface of the mount 172, and the mount 172.
Of the electromagnet 17 arranged in the vicinity of the front side of 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 right above the pedestal 172.

Here, the electromagnet 171 is driven by the secondary side current of the welding transformer as shown in FIG. 9 (a). Further, a roller member 174 having a size in contact with the upper side of the leaf spring member 174 on the upper side thereof and the upper surface of the pedestal 172 on the lower side thereof is attached to the tip end side of the swing lever 173. The lever 173 is adapted to maintain a horizontal posture. Further, an adsorbing metal piece 171a for electromagnetically adsorbing the rear end side of the swing lever 173 is attached to the upper surface of the electromagnet 171.

Further, connecting rods 181a and 181a are provided at the rear end portions of the lower block member 162 and the movable block 5, respectively.
One end of 181b is rotatably supported, and the other end of each of the connecting rods having the flange portions 181a ₁ and 181b ₁ has a cylindrical member 182 in which the inner diameter of the central portion is larger than the inner diameters of both end portions. Are connected by. Here, the diameters of the flange portions of both the connecting rods 181a and 181b are the same as the inner diameter of the central portion of the tubular member 182, whereby the rear end portion of the movable arm 20 and the rear end portion of the fixed arm. It is possible to make slight changes in the height position with respect to.

Further, on the arm front side of the upper block member 161, a movable piece 161a movable along a sliding groove (not shown) formed in the movable frame 22 is attached. Pulling by driving the motor 140a incorporated in the movable frame 22,
By pushing back or the like, the upper block member 16
1 can be slid and moved. Similarly to the upper block 161, the sliding block 5 also has a moving piece 5a on the arm front side that slides in a sliding groove (not shown) formed in the fixed frame 12, A motor 140b that pulls or pushes back the motor and is linked with the motor 140a is incorporated in the frame body. The fulcrum-to-fulcrum moving mechanism includes
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, which is arranged between the spring member 174 and the lower block 162, monitors 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 the welding current to the member to be welded.

The computer 110 has a central processing unit (CPU) 110a for making various judgments and controls, and various welding conditions including the material, surface condition and thickness of the member to be welded, which influence the welding state. Storage device 11 for storing the changing characteristics of the pressure contact force and the welding current for performing the best welding in each case in the case of being set to each
0b and the data input device 110 for inputting the concrete data of the welding conditions to the CPU 110a from the outside.
d and a display device 110c that displays input data and the like.

Here, the CPU 110a, as a first control function, based on the concrete setting data Di1 of the welding condition input from the input device 110d, changes in the best pressure contact force and welding current in that case. The characteristic reading means Mcr for reading the characteristic data Dr from the storage device 110b and the pressure contact force monitor signal Dp are received, and the welding electrodes 1a, 1 are connected.
Optimum, in which the welding current includes the energization time in that case, receiving the welding current monitor signal Dc and the welding force control means Mma for controlling the pressurizing mechanism so that the welding force by b matches the best change characteristic in that case. The welding current control means Mps for controlling the power supply circuit 120 so as to match the change characteristic is provided.

Further, the CPU 110a uses the input data D from the data input device 110d as the second control function.
i, the signal Dh from the horizontality sensor, the current monitor signal Dc, the pressure contact force monitor signal Dp, etc., are subjected to 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, A fulcrum adjustment motor control means Msm for receiving a control command signal Csf and outputting a rear fulcrum movement motor control signal Csm, and a motor control means for receiving the control command signal C ₂ and outputting a gap adjustment motor control signal Cgm An air cylinder control means Mc is provided which receives the control command signal Csf from Mgm and outputs a drive control signal Cc of 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 this spot welding device, the storage device of the computer is equipped with optimum welding conditions corresponding to various welding modes, such as change characteristics of pressure contact force of welding target member, change characteristics of welding current, and change characteristics of welding electrode. Store as information. This information is obtained by the operator from past welding work experience, for example, the optimum welding conditions when these are specifically and uniformly set according to the material, thickness, surface condition, etc. of the member to be welded. is there. In other words, such information is updated or newly added during the experience of welding work, and it is the know-how that only the skilled person has been sensuously acquiring in the past.

In the actual welding operation, first, specific numerical values such as the material and thickness of the members to be welded are input to the computer from the input device 110d such as a keyboard, and the surface condition of the joint surface of the members to be welded and the like. For, also enter a pre-coded number.

Then, in the computer 110, the input / output data processing means Mio receives the input data Di from the input device 110d and performs a predetermined signal processing to perform the predetermined signal processing.
The storage data Dm is output to b, and the characteristic read command signal Di1 is output to the characteristic reading means Mcr. At this time, the processing means M
The io outputs the display data Dd to the welding data display device 110c and displays the input data on the display screen. Further, the characteristic reading means Mcr selects the optimum welding condition corresponding to the welding form specified by the input data from among the optimum welding conditions for each of the various welding forms in the storage device 110b, for example, the pressure contact force change characteristic Xp, welding. 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 pressure contact force control means Mma. As a result, the input / output data processing means Mio processes the read signal and displays the change characteristics Xc and Xp of the display device 110.
Graphically display on the display screen of c.

The input / output data processing means Mio outputs a control command signal C ₁ to the rear fulcrum adjustment motor control means Msm according to the thickness information of the member to be welded in the input data Di. Then, the motor 165 of the position adjusting mechanism 160 is driven, and the left and right block members 163 and 164 approach or separate from each other to adjust the distance between the upper and lower blocks 161 and 162. As a result, when the member to be welded is pressed by the welding electrodes 1a and 1b, the pressure applied by the welding electrode is applied vertically to the member to be welded.

After that, when a welding work start command is given to the computer 110 from the input device 110d, the sequence control function Fsc receives the welding start command signal Cs from the input / output data processing means Mio and starts the sequence control of the robot hand. .. As a result, the robot hand automatically welds predetermined portions of the members to be welded that are sequentially conveyed.

That is, the sequence control function Fsc includes the welding current control means Mps, the pressure contact force control means Mma, the air cylinder control means Mc, and the rear fulcrum adjustment motor control means Msm.
When a sequence control signal Csc is applied to the upper block member 16, the fulcrum distance adjusting motors 140a and 140b are driven by the control signal Csm from the control means Msm.
1 and the movable block 5 move to the front side of the arm, and the rear fulcrum of the movable arm 20 approaches the center turning point. At the same time, the control signal Cc from the air cylinder control means Mc
Thereby, the pneumatic cylinder 3 is driven to lift the movable arm 20 upward. As a result, the tip of the movable arm quickly rises, and the upper and lower welding electrodes 1a and 1b are opened sufficiently wide in a short time. Robot hand moves to swallow 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 moved. , 1b hold the member A to be welded, and at this time, the pressure contact force of the welding electrode 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 electromagnet 171 of 70 is operated by the control signals Cps and Cma from the welding current control means Mps and the press contact force control means Mma of the computer 110, respectively, to perform spot welding.

The welding operation will be described below. While the member A to be welded is sandwiched by the welding electrodes 1a and 1b,
A pressure contact force of the pneumatic cylinder 3 acts on the member to be welded A, and the member to be welded can be welded. Then, in this state, the power supply circuit 120 is driven to operate the welding transformer 1
When an AC current of a predetermined level is applied to the secondary side, the secondary side output of the transformer serves as welding current and the welding electrodes 1a, 1b.
Is supplied to. At this time, the electromagnet 171 of the pressing mechanism 170
Will also be supplied with the secondary output of the transformer 2,
A current having the same waveform as the welding current flows through the electromagnetic coil.
As a result, the same vibrational pressure as that of the welding current waveform is applied, and the welding portions 1a and 1b are melted and welded by solidification.

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 and the input of the computer 110. The output data processing means Mio and the pressure contact force monitor signal Dp are given to the pressure contact force control means Mma and the input / output data processing means Mio. Then, the welding current control means Mps controls the power supply circuit 120 so that the change in the monitored welding current matches the optimum change characteristic of the welding current in this case read from the storage device 110b. Further, the press contact force control means Mma controls the coil current of the electromagnet 174 so that the change in the monitored press contact force matches the optimum change characteristic of the press contact force read from the storage device 110b in this case. At the same time, the welding data display device 110c of the computer 110 graphically displays the change characteristics of the monitor current and the monitor pressure contact force.

Therefore, when the spot melted portion (nugget) is formed on the member A to be welded, even if the changes in the welding current and the pressure contact force deviate from the optimum welding conditions due to unforeseen factors, the welding can be performed while correcting the changes. Will be performed.

When 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 space between the upper and lower welding electrodes, and during this time, the member A to be welded is moved by another transport mechanism, in the same manner as above. Spot welding.

When the welding of one member A to be welded is completed by sequentially performing spot welding in this manner, the movable block 5 and the upper block member 161 are moved so that the rear fulcrum of the movable arm 20 becomes the turning point of the intermediate portion. While being brought close to each other, the pneumatic cylinder 3 is driven to greatly expand the space between the upper and lower welding electrodes, and the processed welded member A is discharged and the unprocessed welded member A is inserted.

In this way, the automatic welding of the members A to be welded, which are successively 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 pressure welding force of the member A to be welded during spot welding, the change in welding current, and the welding current energization time are calculated in these cases. Since the computer is controlled so that the optimum change characteristics suitable for the welding situation are obtained,
Optimal welding can be performed according to the type, thickness, surface condition, etc. of the member to be welded. In addition, when an abnormality occurs in the process of forming the welded portion, the change in the pressure contact force, the change in welding current and the The energization times can be modified so that they match those at normal times.

(2) In addition, when the formation abnormality of the welded portion cannot be repaired only by controlling the pressure contact force and the welding current in the computer, for example, the member to be welded is tilted from the horizontal plane and the welding electrode is not pressurized. If welding is being performed when vertical pressure is not applied to the work piece or when the tip of the welding electrode is unevenly worn, program the product by stopping the line and notifying the operator. The yield can be improved.

(3) Further, the movable arm 20 having the welding electrodes 1a and 1b on the tip end side is supported so that the rear end portion thereof serves as a fulcrum of rotation and the central portion serves as a turning power point. Since the central portion is lifted and lowered by the pneumatic cylinder 3, the distance from the pressure contact (point of action) 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 varies from the standard thickness depending on the type of welded member and the welding site, the normal line of the welding surface of the welded member in the axial direction of the welding electrode The deviation from the direction is small, and the welding electrode can always be pressed against the member to be welded at an angle close to the vertical direction with respect to the pressure contact surface of the member to be welded. Therefore, in some cases, the mechanism 160 for adjusting the electrode gap interval may be unnecessary.

(4) Further, since the adjusting mechanism 160 for adjusting the height position of the rotation fulcrum of the rear end of the movable arm with respect to the rear end of the fixed arm is provided, the member A to be welded is added by the movable welding electrode 1a. The pressure can always be applied perpendicularly to the pressure contact surface of the member to be welded, whereby good spot welding can always be performed regardless of the thickness of the member A to be welded.

(5) Furthermore, since the distance between the rotation fulcrum of the rear end of the movable arm 20 and the rotational power point of the central portion can be changed, the lifting speed of the movable welding electrode can be changed. Yes, for example, when inserting the member to be welded between the upper and lower welding electrodes, when the upper and lower welding electrodes are widely separated so that the welding electrodes do not interfere with the members to be welded, the rotation fulcrum of the arm rear end is moved forward. By moving and bringing it closer to the turning point of the central portion, the ascending / descending speed is increased and the workability can be improved.

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

(7) Further, the power supply device supplies a primary current of a desired waveform and frequency to a welding transformer whose secondary output is connected to the welding electrode and a primary input of the welding transformer. Since it is composed of the power supply circuit 120, 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) Further, 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, the change of the welding current during welding can be read in real time. Therefore, the state of formation of the welded portion can be grasped at any time, and an abnormality in the welding state can be detected. (9) In addition, the formation of the spot welding portion is performed by the electromagnet 1
Since the drive current of 71 is controlled and 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 workpiece A is welded.
Even if the thickness and material of the product are different, spot welding can be performed by the pressure contact 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, and some abnormalities may occur during welding. If a problem occurs, it can be automatically repaired. Further, the welding transformer 2 is attached to the electromagnet 171.
Since a part of the secondary side output is supplied, it is possible to pressurize the welding electrode in synchronization with the welding current, and it is possible to effectively pressurize the member to be welded.

(10) A spring member 174 is provided at the rear end of the movable arm.
An electromagnet 171 that mounts and elastically deforms the spring member by its electromagnetic force is arranged in the vicinity of the spring member, and the movable arm rear end portion is pressed by the elastic deformation force of the spring member to weld the tip end side thereof. The electrode 1a is welded to the member A
Since the pressure is applied to the movable arm 2,
It can be generated without turning 0, and responsiveness and workability can be improved. Further, in this case, since the electromagnetic vibration is applied only to the movable arm 20 and not to the apparatus body, the rigid body setting of the apparatus body can be simplified. Further, in the apparatus of this embodiment, since the center of pressurization is the tension structure, the pneumatic cylinder can be arranged on the transformer, and the size and weight are reduced.

(11) Further, the spring member 174 is further deformed by the pressurizing force of the pneumatic cylinder 3, and a constant pressure contact force by the pneumatic pressure of the cylinder is superimposed on the pressure contact force of the welded member A by the electromagnetic force. Since the pressure contact force does not fall below a certain value, excessive heat generation due to the synchronization deviation between the welding current and the pressure contact force can be avoided when the pressure contact force is extremely small. It is possible to prevent damage to the members.

(12) In addition, the formation of the spot welded portion (nugget) is adjusted so that the strength and weakness of the welding electrode and the energization time are changed by the change of the current monitor signal or the pressure contact force monitor signal to the optimum change characteristic from the characteristic reading means. Since it is possible to control the formation of the welded portion to some extent during welding, some defects in the welding electrode or the member to be welded, for example, the welding electrode is slightly worn or the member to be welded Even if it is slightly curved, it is possible to perform spot welding that is comparable to spot welding in the normal state. When the welding current is a pulse current, the spot welding portion is formed by changing the pulse width and pulse interval of the welding electrode by the current monitor signal and the pressure contact force monitor signal from the characteristic reading means. If the control is performed so as to match the change characteristics, the formation of the welded portion can be controlled to some extent during welding as described above.

Other Modifications of the configuration of the spot welding apparatus will be described. For example, if a potentiometer for detecting the displacement amount of the movable link portion constituting the electrode support mechanism as the displacement amount of the welding electrode is provided, and the pressure contact force of the welded member is calculated based on the output of the potentiometer, During welding, it is possible to read not only the contact pressure of the work piece but also the displacement of the welding electrode in real time.
The formation state of the welded portion can be more accurately grasped by adding data based on electrode displacement.

As shown in FIG. 7, a movable arm 20 having a welding electrode 1a at its tip is rotatably supported with respect to the fixed arm 10 with its central portion as a fulcrum and its rear end as a force point. You may do it. In this type, since the cylinder comes to the rear of the transformer, the structure is simple compared to the case where the pneumatic cylinder 2 is arranged on the transformer, and the head is low, which is excellent in workability. The whole device is larger and heavier than the one that pulls and pressurizes the central part.

Also, as shown in FIG. 10 (a), the movable arm 20
Electromagnet 741 that draws the part on the tip side from the turning power point
And the pressure contact force of the welding electrode 1a is applied to the movable arm 2
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 since the elasticity of the arm itself is used, the pneumatic cylinder is used. The responsiveness of pressurization can be improved. For example, a sufficient pressurizing effect can be obtained even if the stroke of the pneumatic cylinder rod is about 0.1 mm.

Further, although a sound is produced by the pressurization by the electromagnet 171, an AC having a normal 50 to 60 cycles or a triple frequency may have a simple structure. In the case of static pressurization, if the power source of the electromagnet is set to DC, which is about full-wave rectified, the noise is quiet, and the electromagnetic iron core is simply formed of iron material, and the circuit configuration can be relatively simple.

The load of the pressure contact force of the leaf spring member 171 is 1/3 of the total pressure contact force of the welding electrode of the member A to be welded.
The pressure may be about ½ and the rest may use the pressure contact force due to elastic deformation of the movable arm.

Next explained is a spot welding apparatus according to the second embodiment of the invention. This device is a simplified version of the device of the first embodiment as shown in FIG. 3, that is, the gap adjusting mechanism between electrodes and the adjusting mechanism between fulcrums are removed, and the pressurizing mechanism has a simple structure. This point is the same as the device of the first embodiment.

That is, reference numeral 270 denotes the pressurizing mechanism of the apparatus of this embodiment. This pressurizing mechanism 270 has a spring cylinder 32 arranged on the fixed-side frame 12 via a mount 33 and a central portion at the tip of the cylinder rod 32a. Of the fixed frame 12 and the swing frame 31 for supporting the rear end side of the movable side frame 22 at its tip end.
1 Electromagnet 4 attached to the rear side via a gantry 40
1 and 1.

Here, a pressing roller 31b is attached to the tip end side of the swing frame 31 so as to abut against and push up the rear end lower surface of the movable side frame 22, and the rear end portion of the electromagnet 41 is attached. An attracting metal piece 31a for electromagnetically attracting the iron core 41b and pulling down the rear end portion is attached, and an electromagnetic coil 41a is wound around the iron core 41b.

A spring member 32b which is elastically deformed by the downward displacement of the cylinder rod 32a is built in the spring cylinder 32. This elastic deformation force is applied to the rear end portion of the swing frame 31 by the electromagnet 41. I try to generate it by sucking in.

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

In the spot welding apparatus of the second embodiment as described above, the fulcrum-to-fulcrum adjusting mechanism and the electrode-to-electrode gap adjusting mechanism in the apparatus of the first embodiment are removed, so that the operation of moving the rear fulcrum of the movable arm is performed. , And there is no operation for adjusting the height position of the rear end of the movable arm, but otherwise the welding is performed by computer control in the same manner as in the first embodiment.

In the above-described embodiment, the electromagnet 171 is used to generate the pressure applied to the welding electrode. However, the pneumatic cylinder 3 is used to generate a constant pressurization of the welding electrode, and this is applied to the vibration pressurization by the electromagnet. They may be superposed and these pressurizing forces may be controlled by the pressure contact force control means Mma,
In this case, it is possible to follow the actual change in the pressure contact force even with a more complicated change characteristic of the pressure contact force, and finely control the pressure contact force.

Other modifications of the above embodiments will be briefly described below. As a first modification, for example, the first
In the spot welding apparatus 100 of the embodiment, instead of the above power supply device, a primary side thereof is connected to a normal power source unrelated to welding current control, a welding transformer for outputting a welding current to the secondary side, and welding current control means. A power supply circuit for adjusting the secondary side output of the welding transformer based on a control signal from the welding transformer, and the voltage applied to the primary side of the welding transformer can be adjusted by the electromagnet. A direct current or alternating current electromagnet connected to the electromagnetic coil through a regulator, and the voltage applied to the primary side of the transformer is controlled by the regulator just before starting welding and input to the electromagnet.
Appropriate pressure may be applied to the member to be welded. In this case, there is an effect that the pressure contact 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 in which the electromagnet is connected to the primary side of the welding transformer via a voltage adjustable regulator. A coil and a second electromagnetic coil connected to the secondary side of the welding transformer are used as a DC or AC electromagnet mounted on one iron core, and the voltage applied to the primary side of the transformer and the transformer The secondary outputs are superimposed on each other so as not to cancel their respective polarities and input to the first and second electromagnetic coils, and while the welding current is being supplied, the pressurization of the welding target member is synchronized with the welding current and The electromagnetic force generated by the coils may be combined to perform the control. In this case, various pressure contact forces can be controlled.

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 pressure applied by the electromagnet is reduced. When it becomes close to zero and the AC welding current is maximized, the pressure applied by the electromagnet is maximized, and the resistance heating by the welding current causes the current flowing through the member to be welded and the contact resistance of the member to be welded. The relationship may be optimized, and in this case Joule heat, that is, I
The heat effect of ² is the best, and there is an effect that the maximum welding effect can be pursued with a constant welding machine input.

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

FIG. 4 shows a third embodiment of the present invention, which is not a robot hand mounted type, but a general spot welding device which can be controlled by a computer, and the same reference numerals as those in FIG. 5 are the same. In this embodiment, the pressurizing air cylinder 403 of the welding electrode 1a and the welding power source device (not shown) are driven and controlled by the computer 110 of the first embodiment device, and are not shown. However, the spot welding device 403 is equipped with a pressure contact force monitoring device and a welding current monitoring device.

Further, in this apparatus, the pressure contact force of the member A to be welded is controlled by the pneumatic cylinder 403. Therefore, the 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 that abuts on the portion facing 0 is provided, thereby improving the responsiveness of the pneumatic cylinder 403.

At this time, the urging spring exerts a repulsive force of 0 to 100 kg at a stroke of 4 mm, a repulsive force of 100 to 300 kg at a stroke of 2.5 mm, and 300 to 300 at a stroke of 1.0 mm. Those capable of producing a repulsive force of 500 kg are applicable. Specifically, for example, for a T-shaped welding of a thin round Al pipe, a leaf spring having a repulsive force of 0 to 100 kg with a stroke of 3 mm, and for a T-shaped welding of a thick stainless pipe is 2 mm. A ring projection with a repulsive force of 150-300 kg
It is advisable to use a spring of 0 to 500 kg to secure the forging pressure characteristic.

Also in the third embodiment having such a structure, there is an effect by the computer control in the apparatus of the first and second embodiments.

Although each embodiment of the present invention has been described above, the ultimate embodiment of the present invention conventionally involves adjusting the pressure contact force of the member to be welded and the welding current (including adjusting the welding current energization time). In order to ensure the highest quality welding without heat distortion or defective products, which was normally impossible by using), the processing accuracy, material condition, power source What was required by the best welding engineer in consideration of the ability and output condition of the The technology, that is, the welding know-how for overcoming and passing the cause of defects, is input to the computer in advance, and depending on the conditions of the welded part of the workpiece to be welded and its surroundings, it is not always the case that welding current is applied, heat is generated in the welded part, and nugget formation And blend When it does not work normally and a defective product is likely to occur, the welding current applied to the above-mentioned welded member and the pressure contact force of the welded portion are corrected by computer control. It is an immediate action to reduce the pressure. For example, when the welding electrode becomes worn and the tip of the electrode becomes thicker, the member to be welded tilts with respect to the axis of the welding electrode, there is rust or dust on the welding surface, and of course the When the cutting dimensions, shape, material, etc. are different from the standard ones, the welding current passing time, the pressurization condition of the welded member, etc. are comprehensively evaluated and the welding is passed using these evaluations. It is intended to provide software for inputting to a computer a high degree of logical know-how instructing the best correspondence from all correspondences in welding work for making it possible.

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

For example, when butt welding thin-walled pipes, welding thin-walled pipes to flat plates, or T-welding pipes together, or when welding is desired even if a welding material or a coating film is present between flat plates, a powder is added to the joint surface. When you want to weld even if there are granular metals, ceramics, catalysts, etc. (which was impossible with the conventional spot welding technology because there are many rejected products), the minimum time, minimum pressure, and minimum input Must be hermetically welded. At this time, it is necessary to use a pulsation method in which high heat is intermittently repeated in about three thousandths of a second, but with welding technology and control technology using the conventional pressure method, direct current, inverter,
A single-phase AC method using a capacitor is also 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 when the current is small, and the heat of I ² R is sufficiently generated. To use.

In FIG. 15 (a), a cover member is attached to the end face of the thin-walled 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
Is held by the upper electrode 101a in this state.
Lid member Y₁Is pressed against the end face of the pipe for welding.

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

The method of welding the lid member to the end face of the pipe as described above is not limited to the 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
Shows the case of welding a round pipe X ₂
Is held by the lower electrode 102b, and the lid member Y ₂ is pressed against the upper end surface of the pipe by the upper electrode 102a.

Next, FIG. 16 shows a case where a branch pipe is welded to a parent pipe, where X ₃ is the parent pipe and y _{1 to} y _5.
Is a branch pipe welded to the parent pipe.

FIG. 16 (b) shows XVIb-XVIb of FIG. 16 (a).
16C is a view showing a section taken along line XVIc-XVIc in FIG.

Conventionally, when the branch pipe is welded to the parent pipe, the R cut processing is performed on the welded portions of both the parent pipe and the branch pipe. Further, the wall thickness of the branch pipe is thinner than that of the parent pipe, and spot welding is impossible, and arc welding or gas brazing has been performed.

On the other hand, in this method, it is convenient that the airtight welding can be completely performed by spot welding without the need for R-cutting at the welded portions of both.

In FIGS. 16C and 16D, 103
a and 103b are welding electrodes for holding the branch pipes and applying a welding current thereto, respectively.
Is the positive electrode and the negative electrode 103b is the negative electrode. Therefore, in this case, it is possible to weld _two branch pipes y ₁ and y ₂ at the same time.

Next, FIG. 17 shows a case where the end face of the thin-walled pipe is hermetically welded to a flat plate member. In the figure, X ₄ is a flat plate member, and Z is a thin-walled pipe member spot-welded thereto. In addition, FIG. 17 (b) shows that the U-shaped pipe Y ₃ is attached to the flat plate member X _5.
It shows the case where both end faces of are welded.

Next, FIG. 18 shows the case where various other welding is performed. FIG. 18 (a) shows the case where the thin-walled pipes X ₆ and Y ₆ are welded together, and FIG. 18 (b) shows the U-shaped pipe. Y
_In the case where the pipe member X ₈ is welded to the end face of ₈ by welding, in FIG. 18 (c), the rod-shaped welded members X ₇ and Y ₇ are made of different kinds of metal, and between these welded members. A case is shown in which welding is performed by sandwiching a material Z ₁ such as a powdery granular metal, ceramics, a catalyst, etc., which can be welded to both, and in particular, a semiconductor material sandwiched between metal members and welded is useful as a semiconductor element. Yes, there are great benefits.

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

At this time, voltages having different polarities are applied to the electrodes 1a ₁ and 1b ₂ which are in contact with the upper welding member P ₁ , and the electrodes 1b ₁ and 1a opposite to the electrodes 1a ₁ and 1b ₂ are applied.
Between polar but also facing the ₂ applies a different voltage. As a result, as shown in FIG. 18 (e), the insulating film R between the members to be welded is broken to form a nugget N and spot welding is performed.

In such airtight welding, unless good welding know-how for applying a high level pulsation is applied, welding defects frequently occur and the welding work cannot be performed well.

This can be achieved by the method of spot welding by controlling the electromagnetic pressure and the welding current of the present invention by the computer. Further, although the control of the present invention has been described with respect to welding, the basic idea of the present invention is to input the know-how accumulated through such long experience to a computer and simply carry out welding which was impossible in the past 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 the automatic welding robot,
Although the so-called gantry in which the welding transformer and the pressure arm are integrated has been shown, it goes without saying that the present invention can be applied to a normal stationary spot welder and an automatic dedicated welding device. At this time, a pressure mechanism independent of the air pressure mechanism is necessary in order to prevent the air resistance from interfering with the pressure mechanism of the pneumatic cylinder so that the spring pressure structure is not lost.

Instead of the empty cylinder, the solenoid electromagnet may be used until the welding electrode sandwiches the member to be welded by taking advantage of the long stroke of the solenoid electromagnet.

One aim of the present invention is to synchronize the primary side input of the electromagnet, that is, the drive voltage that is not related to the control of the welding current, and the secondary side output of the welding transformer, that is, the welding current. This is to superimpose two types of pressure forces, that is, the vibration pressure force caused by the driving voltage that changes with time and the constant pressure force caused by the stroke movement of the pneumatic cylinder or the solenoid.

FIG. 19 shows the waveform of such superimposed pressurization. P _m1 is the electromagnetic pressure applied by the primary input of the welding transformer, P _m2 is the electromagnetic pressure applied by the secondary output of the welding transformer, P _{m2 m} is a superimposed electromagnetic pressure force obtained by superimposing these electromagnetic wave types, P _a or a constant pressure force caused by movement of the solenoid, P
_t0 is a total pressure force obtained by superposing the above-mentioned constant pressure force P _a and the above-mentioned superimposed electromagnetic pressure force P _m .

These three separate pressures P _m1 , P _m2 ,
Since P _a is added to the member to be welded as a whole, it may be designed from the standpoint that the pressurizing mechanism is small, lightweight, and has a simple and reliable operation. In particular, in the electromagnet, the coil for receiving the primary side input of the transformer and the coil for receiving the secondary side output of the transformer may be collectively wound and mounted on one iron core.

To energize 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 side output of the welding transformer may be applied to the second coil as it is.

As described in the text, the present invention 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 performing spot welding using a welding machine is common, the spot welding of the present invention also includes conventional techniques such as arc welding, brazing welding, and gas welding in which the lid of a container is hermetically welded. It is a spot welding technology with a broad concept including.

[0190]

As described above, according to the spot welding apparatus of the present invention (claim 1), the welding process in spot welding is monitored and the pressure welding force and welding current of the upper and lower spot welding electrodes are monitored. In addition, the pressure welding force of the spot welding electrode and the welding current are controlled by a computer. That is, the computer controls various kinds of materials including the material, surface condition, and thickness of the member to be welded, which influence the welding state. When the welding conditions are specifically set, the optimum change characteristics of the pressure contact force and the welding current for performing the best welding, and the optimum change characteristics including the conduction time are stored in the storage device for each case, Based on the specific setting data of the above welding conditions input by the worker during welding, the optimum change characteristics in that case were determined for the welding force and welding current. The pressure contact force and the welding current of the member to be welded are read out from the memory device so that the change in one or both of the pressure contact force and the welding current being monitored coincides with the optimum change characteristics read out from the memory device. Since the control is performed, optimal welding can be performed according to the type, thickness, surface condition, etc. of the member to be welded. Moreover, when an abnormality occurs in the process of forming the welded portion, the above-mentioned pressure contact force and There is an effect that the welding current can be modified so that each change matches the change characteristic in the normal state.

When the above-mentioned computer cannot repair the formation abnormality of the welded portion only by controlling the pressure contact force and the welding electrode, for example, the member to be welded is inclined from the horizontal plane, and the pressure of the welding electrode is applied to the member to be welded. If welding is being performed in a state where vertical pressure is not applied or the tip of the welding electrode is unevenly worn, the product yield is improved by programming the line to stop and notify the operator. There is an effect that can be improved.

According to the present invention (the second aspect), in the above spot welding apparatus, the movable arm having the welding electrode on the tip side is used as the rotation fulcrum at the rear end as the turning power point. Since the movable arm is supported and the central portion thereof is lifted or pulled down by an actuator device such as a pneumatic or hydraulic cylinder, the pressure contact of the member to be welded by the welding electrode (acting point ) To the rotation fulcrum of the movable arm can be made large enough to fill the length of the movable arm, and even if the thickness of the welded portion varies from the standard thickness depending on the type of the member to be welded and the welding site. , The deviation of the welding electrode axial direction from the normal direction of the welding surface of the member to be welded is small, and the welding contact of the welding member by the welding electrode is always applied to the welding surface of the welding member. There is an effect that can be performed at an angle close to the vertical direction Te.

According to the present invention (corresponding to claim 3), in the spot welding apparatus, a part of the electrode supporting mechanism for supporting the movable arm with respect to the fixed arm is provided with a member to be welded by the welding electrode. Since a piezoelectric element for detecting the pressure contact force as a pressure generated in the contact portion of the structure of the electrode supporting mechanism is incorporated and the output signal of the piezoelectric element is monitored as the pressure contact force, the pressure contact of the welded member during welding is performed. The force can be read in real time, and the formation status of the welded part, that is, the pressure welding force of the workpiece to be welded, changes in welding current, and energization time can be grasped at any time. There is an effect that can be.

According to the present invention (the fourth aspect), the spot welding apparatus is provided with a potentiometer for detecting the displacement amount of the movable link portion constituting the electrode supporting mechanism as the displacement amount of the welding electrode. Since the pressure contact force of the welded member is calculated based on the output of the potentiometer, not only the pressure contact force of the welded member but also the displacement of the welding electrode can be read in real time during welding, and the welding portion There is an effect that the formation status can be grasped more accurately.

According to the present invention (the fifth aspect), in the spot welding apparatus, the power supply device is
Since the secondary side output is composed of a welding transformer connected to the welding electrode and a power supply circuit for supplying a primary current of a desired waveform and frequency to the primary side input of the welding transformer, There is an effect that the waveform of the welding current can be made suitable for each condition depending on various conditions such as material and thickness. Further, since the current measuring device for measuring the primary current of the above welding transformer is provided and the measured current is monitored as the welding current, it is possible to read the change of the welding current during welding in real time and form the welded portion. The effect is that the situation can be grasped at any time, and an abnormality in the welding situation can be detected.

According to the present invention (claim 6), in the spot welding apparatus, an electromagnet for attracting a portion of the movable arm on the tip side from the turning point is provided, and the pressure contact force of the welding electrode is applied to the movable arm. Since it is generated by elastic deformation of No. 3, there is an effect that the mechanism for generating the pressure contact force of the welding electrode by the electromagnetic force can be easily realized only by the electromagnet. The spot welding portion is formed by controlling the driving current of the electromagnet so that the changes in the welding current and the pressure contact force being monitored match the optimum change characteristics from the characteristic reading means. Even if the material to be welded has different thickness, material, etc., spot welding can be performed in each case by the optimum change characteristic pressure contact force and the optimum change characteristic welding current including energization time and pulsation timing. In addition, even if some abnormality occurs during welding, there is an effect that it can be automatically repaired.

According to the present invention (corresponding to claim 7), in the spot welding apparatus, a spring member is attached to the rear end of the movable arm, and an electromagnet for elastically deforming the spring member by its electromagnetic force is provided. The movable arm is arranged 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 so that the welding electrode on the tip side of the movable arm is pressed against the member to be welded. Can be generated without rotation, and responsiveness and workability can be improved. Further, in this case, since the electromagnetic vibration is applied only to the movable arm and not to the apparatus body, there is an effect that the rigid body design of the apparatus body can be simplified.

According to the present invention (the eighth aspect), in the spot welding apparatus, the movable arm or the spring member is further deformed by the pressure of the pneumatic pressure or the hydraulic cylinder or the solenoid, and the electromagnetic force is applied. Since the constant pressure contact force due to the pneumatic pressure or hydraulic pressure of the cylinder or the electromagnetic force of the solenoid is superimposed on the vibration pressure contact force due to, the pressure contact force does not fall below a certain value. It is possible to avoid excessive heat generation due to the synchronism shift between the electric current and the pressure contact force, and it is possible to prevent damage to the welding electrode and the member to be welded.

According to the present invention (corresponding to claim 9), in the spot welding apparatus, the welding current is AC power or DC power, and the strength and weakness of the welding electrode and the conduction time are the current monitor signal and the pressure contact force. Since the change of the monitor signal is controlled to match the optimum change characteristic from the characteristic reading means to form the spot welded portion, the formation of the welded portion can be controlled to some extent during welding. Even if there are some defects in the welding electrode or the member to be welded, for example, the welding electrode is slightly worn or the member to be welded is slightly curved, spot welding can be performed in the same manner as spot welding in the normal state. There is an effect that can be done.

According to the present invention (claim 10), in the spot welding apparatus, the welding current is a pulse current, and the pulse width and pulse interval of the welding electrode are monitored. Since the change of the pressure contact force is controlled to match the optimum change characteristic from the characteristic reading means to form the spot welded portion, the formation of the welded portion is controlled to some extent during the welding as described above. There is an effect that can be.

According to the present invention (the eleventh aspect), in the spot welding apparatus, the drive current of the electromagnet can be adjusted from the primary side of the welding transformer, which is unrelated to the control of the welding current. Since it is supplied to the electromagnetic coil via the adjuster and the member to be welded is appropriately pressurized by the electromagnet, the pressure contact 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, the present invention (according to claim 12)
According to the above, in the spot welding apparatus, the electromagnet is provided with the first and second electromagnetic coils mounted on the iron core, and the first electromagnetic coil is provided with a regulator capable of adjusting the voltage on the primary side of the welding transformer. And the second electromagnetic coil is connected to the secondary side of the welding transformer, and the polarity of the applied voltage to the primary side of the welding transformer and the secondary side output of the welding transformer is not canceled. So as to be input to the above-mentioned first and second electromagnetic coils and to apply pressure to the member to be welded while the welding current is being supplied, in synchronism with the welding current and by combining the electromagnetic forces of both coils. Therefore, it is possible to control more various pressure contact forces.

According to the present invention (the thirteenth aspect), 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 is reduced. Is close to zero, and when the AC welding current is maximized, the pressure applied by the electromagnet is maximized, and the resistance heating by the welding current causes the current flowing through the welded member and the contact resistance of the welded member to Therefore, the Joule heat, that is, the thermal effect of I ² R is optimized, and the maximum welding effect can be pursued with a constant welding machine input.

According to the spot welding method of the present invention (the fourteenth aspect), various welding conditions that affect the welding state, including the processing accuracy of the member to be welded, the material, and the ability of the welding power source, can be obtained. In order to carry out the best welding in the welding mode specifically set, the optimum change characteristic of the welding force and the welding current are determined based on the comprehensive judgment based on the experience of the welding engineer for each welding mode. , The optimum change characteristics including the energization time are stored, these optimum change characteristics are stored in the memory device of the computer, and at the time of welding, specific setting data of the above welding conditions is input to the computer from the outside. Identify one welding embodiment,
The optimum change characteristic of the pressure contact force and the optimum change characteristic of the welding current including the conduction time in the specified welding embodiment are read from the storage device, and during the spot welding, the pressure contact is performed by the pre-programmed control means of the computer. Since one or both of the force and the welding current are feedback-controlled so that these changes coincide with the optimum change characteristic of the pressure contact force and the optimum change characteristic of the welding current including the conduction time in that case, conventional welding is performed. To realize the best correspondence in the welding work, which could not be realized by the function of the machine and the uniform welding method, only by a skilled welding operator, by a computer in every aspect of welding execution And the effect of being able to easily perform the best possible welding work only with the know-how of a welding expert. .

Furthermore, the present invention (according to claim 15)
According to the above, in the spot welding method, as the welding mode, the thin-walled pipes are butt-welded together, the end face of the thin-walled pipe is welded to a flat plate, and the end face of the thin-walled pipe is welded to the side face of the pipe in a T-shape. To be welded, members to be welded facing each other with an adhesive material or a coating film interposed between them, and members to be welded having a powder or granular material of a metal, ceramic, or catalyst-containing material on the joint surface. Therefore, the yield is improved particularly in the above-described welding implementation mode in which many products were rejected by the conventional spot welding technique.

[Brief description of 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 configuration diagram for explaining 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 diagram 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 diagram for explaining the structure of a robot hand mounted on a conventional robot welding apparatus.

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

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

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

10 is a diagram showing a specific pressing mechanism for a welding electrode in the robot hand shown in FIG.

FIG. 11 is a diagram showing another specific pressing mechanism for the welding electrode in the robot hand shown in 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 defective welding in spot welding.

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

FIG. 15 is an explanatory diagram for spot welding a lid member to an end surface of a thin pipe.

FIG. 16 is an explanatory diagram of spot welding a branch pipe to a parent pipe.

FIG. 17 is an explanatory diagram for spot welding the end face of the thin-walled pipe to a flat plate.

FIG. 18 is a diagram for explaining another welding mode, FIG. 18 (a) is an explanatory diagram for butt welding a thin-walled pipe, and FIG. Fig. 18 (c) shows an explanatory diagram for simultaneous welding.
Fig. 18 (d), which is an explanatory diagram for welding by sandwiching powdery metal particles, ceramics, a catalyst, etc. between two rod-shaped members to be welded.
(e) is a sectional view before and after welding when flat plates are welded with an adhesive or the like interposed.

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

[Explanation of symbols]

 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 position adjusting device 170 Electromagnetic pressure mechanism 180 Coupling mechanism A Parts 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

Front page continuation (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location B23K 11/24 336 9265-4E 11/25 9265-4E 510 9265-4E G01B 7/18 Z 9106-2F G01L 1 / 16 G05B 13/02 J 9131-3H G05F 1/00 4237-5H

Claims (15)

[Claims] 1. A pair of welding electrodes for applying a welding current to a member to be welded, an electrode supporting mechanism for supporting the two welding electrodes so that they can come close to and away from each other, and the two welding electrodes by driving the electrode supporting mechanism. An actuator device for holding and releasing a member to be welded by electrodes, and 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 are provided. In a spot welding apparatus for spot welding by resistance heating of a pressure contact portion by a welding electrode, as a device for monitoring the welding process of the pressure contact portion, a pressure contact force monitoring device for monitoring the pressure contact force of the member to be welded by the welding electrode is used. , A current monitor device for monitoring the welding current applied to the welding electrode, and the computer has an effect on the welding state. The material of the member to be welded, the surface conditions,
A memory that stores, for each case, the change characteristics of the pressure contact force for performing the best welding and the change characteristics of the welding current including the energization time when various welding conditions including the thickness are specifically set. Characteristic reading means for reading the optimum change characteristics of the pressure contact force and the optimum change characteristics of the welding current including the energization time from the storage device based on the apparatus and the specific setting data of the welding conditions input from the outside. A pressure contact force control means for controlling the actuator device so that the change of the pressure contact force by the welding electrode matches the optimum change characteristic in that case, and the welding current monitor signal, A welding current control means for controlling the power supply device so that the change in the welding current matches the optimum change characteristic including the energizing time in that case is provided. And spot welding equipment. 2. The spot welding apparatus according to claim 1, wherein the electrode support mechanism includes a fixed arm fixed to the apparatus body side and having a fixed-side welding electrode at a tip thereof, and a rear end portion as a rotation fulcrum. The movable body has a movable arm supported by the central portion so as to face the fixed arm and has a welding electrode on the tip side, and the actuator device includes pneumatic pressure for lifting and lowering the movable arm. A spot welding device characterized by being a hydraulic cylinder or a solenoid. 3. The spot welding apparatus according to claim 1, wherein the pressure contact force monitoring device is incorporated in a part of an electrode supporting mechanism, and a pressure contact force of a welding target member by the welding electrode is applied to a structure of the electrode supporting mechanism. 2. A spot welding apparatus, comprising: a piezoelectric element that detects a pressure generated at a contact portion of the piezoelectric element and monitoring an output signal of the piezoelectric element as a pressure contact force. 4. The spot welding apparatus according to claim 1, wherein the pressure contact force monitoring device detects a displacement amount of a movable link portion forming the electrode support mechanism as a displacement amount of the welding electrode, and the potentiometer. And a pressure contact force calculation means for calculating the pressure contact force of the member to be welded on the basis of the output of the spot welding apparatus. 5. The spot welding apparatus according to claim 1, wherein the power supply device is based on a welding transformer whose secondary output is connected to the welding electrode, and a control signal from the welding current control means. It comprises a power supply circuit for supplying a primary current of a desired waveform and frequency to the primary side input of the welding transformer, and the current monitor device is a current measuring device for measuring the primary side input current. Spot welding equipment. 6. The spot welding apparatus according to claim 2, further comprising an electromagnet that draws a portion of the movable arm on a tip side from a turning point of the movable arm, and the pressing force of the welding electrode is generated by elastic deformation of the movable arm. In the formation of the spot welded portion, the driving current of the electromagnet is changed by changing one or both of the pressure contact force and the welding current being monitored, and the optimum change characteristic of the pressure contact force from the characteristic reading means and the welding current. The spot welding apparatus is characterized in that it is controlled so as to match the optimum change characteristics including the energization time. 7. The spot welding apparatus according to claim 2, further comprising a spring member attached to the rear end of the movable arm and an electromagnet that elastically deforms the spring member, and the elastic deformation force of the spring member The movable arm has a pressing mechanism that presses the rear end of the movable arm and presses the welding electrode on the tip side of the movable arm onto the member to be welded.The spot welding portion is formed by pressing the driving current of the electromagnet with the pressing force that is being monitored. And one or both of the welding current and the welding current are controlled so as to match the optimum changing characteristics of the pressure contact force from the characteristic reading means and the welding current, including the conduction time, respectively. 8. The spot welding apparatus according to claim 6 or 7, wherein the movable arm or the spring member is further deformed by the pressure of the air pressure or the hydraulic cylinder or the solenoid, and the vibration pressure contact force of the electromagnet is applied to the cylinder. A spot welding apparatus characterized in that a constant pressure contact force by pneumatic force, hydraulic pressure, or electromagnetic force of a solenoid is superimposed. 9. The spot welding apparatus according to claim 1, wherein the welding current is AC power or DC power, and the spot welding portion is formed by adjusting one or both of the intensity of the welding current and the energization time. Control is performed so that changes in one or both of the pressure contact force and the welding current being monitored match the optimum change characteristic of the pressure contact force from the characteristic reading means and the optimum change characteristic of the welding current including the energization time. Spot welding equipment. 10. The spot welding apparatus according to claim 1, wherein the welding current is a pulse current, and the spot welding portion is formed by monitoring one or both of a pulse width and a pulse interval of the welding current. The change in one or both of the pressure contact force and the welding current being performed is controlled so as to match the optimum change characteristic of the pressure contact force from the characteristic reading means and the optimum change characteristic of the welding current including the energization time. Spot welding equipment. 11. The spot welding apparatus according to claim 6 or 7, wherein a primary side of the spot welding apparatus is connected to a normal power source irrelevant to the welding current control, and a welding current is output to the secondary side, and the welding current. A power supply device comprising a power supply circuit for controlling the secondary side output of the welding transformer based on a control signal from the control means, and the electromagnet via a regulator capable of adjusting the voltage of the primary side of the welding transformer. A direct current or alternating current electromagnet connected to the electromagnetic coil, and the voltage applied to the primary side of the welding transformer is controlled by the adjuster and input to the electromagnet immediately before the start of welding, and is applied to the member to be welded. Spot welding equipment characterized by applying a pressing force. 12. The spot welding apparatus according to claim 11, wherein the electromagnet is connected to a primary side of the welding transformer via a regulator capable of adjusting a voltage, and a welding coil of the welding magnet. The second electromagnetic coil connected to the secondary side is an electromagnet for direct current or alternating current mounted on one iron core, and the applied voltage to the primary side of the welding transformer and the secondary side output of the welding transformer are used. They are input to the first and second electromagnetic coils in a superimposed manner so as not to cancel their respective polarities, and while the welding current is being applied, the pressurization of the member to be welded is synchronized with the welding current and the electromagnetic force generated by both coils is applied. The spot welding device is characterized in that it is performed by synthesizing. 13. The spot welding apparatus according to claim 12, wherein 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, and the AC welding is performed. When the current is maximized, the pressure applied by the electromagnet is maximized, and the resistance heating due to the welding current is optimized from the relationship between the current flowing through the welded member and the contact resistance of the welded member. Spot welding equipment characterized in that. 14. A method for performing spot welding in which a predetermined portion of two members to be welded is pressure-welded and a welding current is applied to the pressure-welded portion to weld the pressure-welded portion by computer control, wherein the welding of the members to be welded is performed. Accuracy, material, ability of welding power source,
A comprehensive judgment based on the experience of a welding engineer for each of the welding modes should be taken in order to realize the best welding in the modes of welding in which various welding conditions affecting the welding state are specifically set. The optimum change characteristics of the pressure contact force and the welding current, including the conduction time, are obtained as the optimum change characteristics based on the above, and these optimum change characteristics are stored in the memory of the computer. The specific setting data is input to the computer to specify one welding mode, and the optimum change characteristics of the welding force and the optimum change characteristics of the welding current including the energization time in the specified welding mode are stored in the storage device. During read-out, the spot welding, one or both of the pressure welding force and welding current are controlled by the pre-programmed control means of the computer. Of optimum variation characteristics of contact pressure in the welding embodiment specified above, the welding current,
A spot welding method characterized in that feedback control is performed so as to match an optimum change characteristic including energization time. 15. The spot welding method according to claim 14, wherein the welding mode is such that thin-walled pipes are butt-welded together, or the end faces of the thin-walled pipes are welded to a flat plate.
Welding the end face of a thin-walled pipe in a T-shape on the side face of the pipe, welding opposite members to be welded with an adhesive or coating film interposed between them, metal, ceramic, catalyst on the joint surface What is claimed is: 1. A spot welding method, which includes a method for welding a member to be welded, which has a powdery or granular material of the material.