JP2001096375A - Capacitor type resistance welding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve safety as well as durability, and also miniaturize and lighten in a capacitor type resistance welding machine. SOLUTION: This capacitor type resistance welding machine for welding a metal plate by pinching the plate with the electrode tips opposed to each other, and applying a pressure and the current to the tips, is provided with an ultra-high capacity capacitor connected to the tips and a charging circuit charging the capacitor up to a welding voltage. Welding is performed by pressurizing the electrode tips and discharging electricity. Thereby, the weight of the resistance welding machine can drastically reduced and safety is ensured because the machine does not need incidental facilities such as a heavy transformer, thick secondary cable, high voltage primary cable, etc., comparing with the conventional welding machines.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention charges an ultra-large capacity capacitor, which does not use a welding transformer and supplies a welding current directly to an electrode tip of a resistance welding machine without passing through a welding transformer, up to a welding voltage, and welds a workpiece. The present invention relates to a capacitor-type resistance welding machine that performs welding by sandwiching between electrode tips, applying pressure, discharging a part of the electric charge stored in a capacitor, and supplying a welding current.

[0002]

2. Description of the Related Art Conventional resistance welding machines are:
Pressurize the electrode tip on the secondary side of the welding transformer and then adjust the primary current and energizing time by performing phase control with a thyristor installed on the primary side of the welding transformer, or PWM control with a transistor, or in the same way, After controlling the charging voltage of a capacitor installed on the side, the accumulated charge is discharged by a thyristor or the like, and welding is performed by flowing a welding current.

[0003] A welding transformer converts between voltage and current. That is, for example, welding a steel plate for an automobile body requires a large current of several thousand amperes, but the voltage may be low. Regarding the current control element, whether it is a mechanical switch or an electronic switch, it is relatively easy to design it to withstand a voltage of about 400 V, which is usually used as a welding power source. In order to open and close the current, the device becomes large-scale, for example, by connecting multiple elements in parallel, and there are problems in cost, size, and weight. Therefore, conventional welding machines generally use a welding transformer to control the welding current and the energizing time on the primary side, which has a high voltage but a small current.

Further, in the conventional capacitor welding machine, an aluminum electrolytic capacitor having a capacity of several thousand μF (microfarad) per element as an upper limit is used as in the prior art, so that the welding current is amplified by a welding transformer. Unless otherwise, it was difficult to apply the method to a resistance welding machine used for steel sheets having a thickness of about 0.6 mm or more, such as steel sheets for automobile bodies.

That is, conventionally, the adjustment and opening / closing of the welding current have conventionally been performed.
Welding transformers have been used to operate in smaller and more easily controllable ranges (several hundred to 2000A), but the disadvantages in this case are the size and weight of the welding transformer and the thickness of the secondary cable, or high voltage. It is a danger.

For example, in the case of a portable spot welding machine as an example, the weight of a portable transformer of 150 kVA is about 200 kg, cannot be held by hand, and must be suspended from the ceiling or placed on the floor. It is not a good working environment. The secondary cable connecting the welding transformer secondary terminal and the gun has a thickness of 150 to 200 m.
m ² about is required, the handling is very hard work.

When a gun with a transformer in which a welding transformer is integrated with a welding gun is used, the operator has to work with a primary cable, which is thinner (about 22 mm ² ), but a high voltage (about 400 V) on the primary side of the welding transformer. The part comes to the operator's hand, and there is a risk of electric shock. Furthermore, the weight of the welding gun for the welding transformer increases (about 40 to 60 kg), and even if it is supported from the ceiling by a spring balancer, the burden of handling increases.

[0008] The above-mentioned numerical values and disadvantages are enumerated as specific examples of a portable spot welder for automobile steel sheets, and are not limited to a portable welder, but are stationary welders, multi-welders, and robots. Regarding guns, the size and weight of welding transformers and guns, the burden of handling secondary cables, and the danger of high-voltage circuits are not limited to humans, but to robots.
Similar malfunctions exist, even for machines. Of course, the present invention is not limited to welding machines for automobile steel sheets but also to small welding machines having a small capacity applied to electronic components, etc., as described below, by implementing the present invention to eliminate the welding transformer and obtain the same advantages. Can be.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in order to solve such a problem. An ultra-high-capacity capacitor for supplying a welding current directly to an electrode tip without passing through a welding transformer, and a capacitor for supplying a welding voltage to the electrode tip. A charging circuit for charging, driving the electrode tip, sandwiching the workpiece, discharging a part of the electric charge stored in the capacitor directly to the welding circuit and applying a welding current to perform welding as described above. Fixed bugs.

In the case of a super-large capacity capacitor represented by an electric double layer capacitor, several hundreds to 1,000
It is possible to realize a super large capacity of more than F (Farad), which is one million times larger than that of the conventional aluminum electrolytic capacitor. If a capacitor unit combining multiple cells is used, even if a welding transformer is not used, A large current required for direct welding can be supplied.

The appropriate charging voltage of the capacitor varies depending on the material and thickness of the welded product, the size of the gun arm, etc., but is usually about 2 to 10 V, and there is no danger of electric shock even if the worker touches it. The capacity of the super-large capacity capacitor is 5,000 to 20,000 for welding steel sheets for general automobile bodies.
A capacitor unit of about 00F (Farad) is used. The weight is about 2 to 8 kg, and even if it is attached to the welding gun, the increase in the burden on the worker is slight.

The charging current varies depending on the welding current and the usage rate.
However, as an example, the charging current is set to 100 A (equivalent continuous value).
And the thickness of the charging cable is 14mm^TwoAbout
Kickless scale used in general portable transformers
Cable (150-200mm ^TwoDegree) thinner than
The cable management burden is greatly improved.

As described above, the first aspect of the present invention comprises an ultra-large capacity capacitor for supplying a welding current directly to an electrode tip without passing through a welding transformer, and a charging circuit for charging the capacitor to a welding voltage. The electrode tip is pressurized to mechanically clamp the welded object, electrically connect the welding circuit for a predetermined energization time, discharge a part of the electric charge, conduct the welding current, perform welding, and then insert the electrode tip. I made it open. As a result, the problems of welding machines using conventional welding transformers were basically eliminated.

Although the gun arm and the electrode tip are water-cooled as before, water cooling is also applied to an ultra-large capacity capacitor depending on the usage rate. Attach a water-cooled pipe to the electrode plate of the capacitor terminal, or attach the capacitor body to a water-cooled copper or aluminum plate.

According to a second aspect of the present invention, a mechanical contact or an electronic switch for electrically opening and closing the welding circuit is provided between the super-capacitance capacitor and the electrode tip. After the pressure is applied, the switch is closed to energize, and at the end of welding, the switch is opened and then the electrode tip is opened. The switch must have a large capacity that can carry a large current of several thousand amperes. In this case, when the switch is opened and closed to turn on and off the welding current, the electrode tip and the Since is in a pressurized state, no electric spark is generated there.

According to a third aspect of the present invention, a contact electrode for opening and closing the welding circuit is provided behind the electrode tip on one side, and a spring for initial pressurization for expanding the contact electrode when no pressure is applied to cut off the welding circuit. ing. In this way, no voltage is applied to the electrode tip when the electrode tip comes into contact with the workpiece even when the electrode tip is driven to sandwich the workpiece and the initial pressure is applied. No electric sparks occur. Thereafter, the electrode tip is further pressurized, and a spring for initial pressurization is pushed in.
The contact electrode contacts to conduct electricity. At this point, pressure is applied due to the spring constant for initial pressurization.
The mechanical bounce between the electrode tip and the weldment, that is, the chattering phenomenon, is small, and electric spark is hardly generated in the contact electrode portion. Furthermore, if the contact electrode is made replaceable and regular maintenance is performed, good electrical contact can be maintained at all times.

In the third aspect, when the welding is completed and the electrode tip is opened, the contact electrode is first expanded and opened by the action of the spring for initial pressurization. In the welding machine according to the present invention, the electric charge of the super-capacitance capacitor is usually not completely discharged even after the welding is completed, and when the contact electrode having the potential is opened and the welding circuit is cut off in that state, the welding circuit is closed. Since the electrical impedance suddenly becomes infinite, a high voltage is generated between the contact electrodes, and an electric spark is easily generated. Therefore, in the present invention, in order to more effectively prevent the electric spark, the present invention is applied to claim 4 and claim 5 of the present invention.
The following means are provided.

According to a fourth aspect of the present invention, at the moment when the contact electrode is opened and an electric spark is generated, a power transistor or a thyristor is installed in parallel with the contact electrode and electrically forward with respect to the welding current. The electric spark is suppressed by turning on the electronic switch for a short time to bypass and reduce the high voltage generated between the contact electrodes.

According to another aspect of the present invention, a diode having a forward drop slightly higher than the welding voltage is installed in parallel with the contact electrode and electrically forward with respect to the welding current. Electric sparks are suppressed by bypassing and reducing high voltages above the resulting forward drop.

Further, according to the present invention, depending on the type of the welded material, a more accurate welding result can be obtained.
The following means are provided.

According to the present invention, the charging voltage at the start of welding is detected, and the energizing time is adjusted based on the detected value. If the charging voltage is low, the welding current decreases. Therefore, the energization time is extended by a predetermined value programmed in advance so as to compensate for the decrease in the calorific value of the weld due to the decrease.

The super-large capacity capacitor such as the electric double layer capacitor used in the present invention does not discharge all the accumulated charges by one-point welding as in the conventional capacitor welding machine, but conducts electricity during the discharging. I try to stop it. Therefore, welding conditions can be adjusted not only by the charging voltage as in the conventional capacitor welding machine but also by the energizing time. In this way, even if it is necessary to perform the next welding before the charging voltage of the capacitor, that is, the welding voltage has not sufficiently recovered, the energization time can be extended and corrected. There is no need to wait for the voltage to reach. Further, even when the welding conditions are changed to lower ones, the current can be shortened and adjusted without the need to discharge the electric charge of the capacitor and reset it as in the conventional case.

According to a seventh aspect of the present invention, a current sensor such as a toroidal coil or a Hall element is installed on the gun arm of the welding machine, and the welding current is detected every moment while performing welding, and the accumulated value is programmed in advance. When a predetermined value was reached, the power supply was stopped.

In this manner, as described above, not only when the charging voltage of the capacitor, that is, the welding voltage has not yet been sufficiently recovered, it is necessary to perform the next welding, but also there is a poor contact in the welded object. Even if there is any disturbance such as a change in welding current, a predetermined welding quality can be ensured.

Further, in the eighth aspect, a current sensor such as a toroidal coil or a Hall element and a voltage detection line from a capacitor terminal or an electrode chip are installed on a gun arm of a welding machine, and a welding current is generated while performing welding. The terminal voltage of the capacitor or the voltage between the electrode tips is detected every moment, and when the product of these, that is, the electric power, in other words, the welding energy reaches a predetermined value programmed in advance, the energization is stopped.

In this way, since the welding energy is always kept constant, a predetermined welding quality can be ensured even when various disturbances such as power supply fluctuations and load fluctuations occur.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment in which claim 1 of the present invention is applied to a portable gun. One of the terminals of the ultra-large capacity capacitor 1 is connected via the shunt 2 on one side.
The other is connected to the electrode tip 3 (+) and the other to the electrode tip 5 (−) via the gun arm 4. The electrode pressurizing actuator 6 is a pressurizing unit using, for example, an air cylinder or an electric motor. The positive and negative polarities (+) and (-) of the electrode tip may be connected to opposite polarities for convenience.

FIG. 2 is an electric circuit diagram when the first embodiment of the present invention is implemented. The control device 15 controls the charging circuit 13 to charge the ultra-large capacity capacitor 1 to a predetermined voltage. When performing welding, the control device 15 controls the actuator 6.
Is driven to apply a welding current by pressing the electrode tip 3 to close the circuit, open the electrode tip 3 after a predetermined energized time, and cut off the welding current.

FIG. 3 is a timing chart when the first embodiment of the present invention is implemented. When the electrode is pressurized and the opening amount becomes zero, that is, when the electrode comes into contact with the work, the electric charge of the capacitor is discharged to the welding circuit and the welding current starts to flow, and at the same time, the capacitor terminal voltage decreases. The initial slope waveform depends on the inductance of the welding circuit, and has a length of about 5 ms in the welding gun of this embodiment.

The welding current reaches a peak after the above initial slope, and then changes to a gentle down slope. In this embodiment, the electric impedance of the welding circuit, that is, the total value of the internal impedances of the gun arm, the workpiece, and the supercapacitor is about 500 μΩ, and the welding current is about 8,000 A. As the welding progresses, the electric charge stored in the super-capacitance capacitor is discharged, so that the capacitor terminal voltage waveform falls with a gentle down slope, and the welding current waveform accordingly falls. However, since the capacity of the super-large capacity capacitors used in the present embodiment was about 10,000 F (Farad), their drop rates were extremely small. That is, only a part of the accumulated electric charge of the super-large capacity capacitor is used in the spot welding of one spot. For this reason, the welding current waveform during the energization time is maintained at a substantially constant direct current, although there is a slight down slope.

When the electrode tip is opened after a conduction time of about 200 ms, the welding current waveform instantaneously drops to zero because the electric impedance of the welding circuit suddenly becomes infinite, and a high voltage is applied between the electrode tip and the workpiece. As a result, an electric spark is easily generated. Subsequently, the capacitor terminal voltage waveform is recovered by the charging circuit, and gradually recovers and rises. This charging current value is set according to the equivalent continuous capacity according to the usage rate of the welding machine.

FIG. 4 is an electric circuit diagram according to a third embodiment of the present invention. The control device 15 controls the charging circuit 13 and
The super-large capacity capacitor 1 is charged to a predetermined voltage. When welding is performed, the controller 15 presses the electrode tip 3 and then closes the electronic switch 14 to supply a welding current. After a predetermined energizing time, the controller 15 opens the electronic switch 14 to cut off the welding current. Release 3. In this way, when the switch is turned on and off to turn on and off the welding current, the electrode tip and the welded article are in a pressurized state, so that no electric spark is generated there.

FIG. 5 is a structural view of an initial pressurizing unit according to a fourth embodiment of the present invention. In the non-pressurized state shown in FIG. 2A, the contact electrode 7 for supplying the welding current to the electrode tip 3 is spread by the spring 8 via the insulating plate 9, and when the electrode tip 3 comes into contact with the workpiece. No voltage is applied, and therefore no electrical spark occurs between the electrode tip and the weld. A cooling water inlet / outlet 10 for water-cooling the electrode tip is provided on a side closer to the electrode tip 3 than the contact electrode 7.

In the pressurization shown in FIG. 5B, after the pressurizing actuator pushes the electrode tip 3 into contact with the welded object 11, the spring 8 is further pushed down until the contacts of the contact electrode 7 come into contact. State. In this case, since the welding object is initially supplied with pressure by the electrode tip 3 having no potential and then supplied with power by the contact electrode 7, no electric spark is generated between the electrode tip and the welding object. When the contact electrodes come into contact with each other, it is possible that a slight electric spark is generated between the contact electrodes due to mechanical bouncing, that is, chattering phenomenon, depending on the contact condition at that time. Every
If regular maintenance is performed, good contact can always be maintained.

FIG. 6 shows the initial pressurizing unit 1 shown in FIG.
This is an embodiment in which No. 2 is attached to a welding gun. One of the terminals of the ultra-large capacity capacitor 1 is connected via the shunt 2 on one side.
The other is connected to the electrode tip 3 (+) and the other to the electrode tip 5 (−) via the gun arm 4. When the electrode pressurizing actuator 6 presses the electrode tip 3 to contact the welded object, no voltage is applied to the electrode tip 3,
There is no electric spark between the electrode tip and the weld. Thereafter, when the pressure actuator 6 further presses the electrode tip 3, the contact electrodes in the initial pressure unit 12 come into contact with each other to supply power to the welded object. In this figure, the initial pressurizing unit 7 is attached to the electrode chip 3 side, but it may be attached to the electrode chip 5 side. FIG. 7 is an electric circuit diagram of FIG. 6 to which the initial pressurizing unit is applied.

FIG. 8 is an electric circuit diagram of a fourth embodiment of the present invention. The control device 15 controls the charging circuit 13 and
The super-large capacity capacitor 1 is charged to a predetermined voltage. When welding is performed, the control device 15 presses the electrode tip 3, contacts the contact electrode in the initial pressurizing unit 12 and supplies power to supply a welding current, and opens the electrode tip 3 after a predetermined conduction time. To open the contact electrode and cut off the welding current. When the contact electrode is opened, the electrical impedance of the welding circuit suddenly becomes infinite,
A high voltage is generated between the contact points of the contact electrodes, and an electric spark is easily generated. In order to suppress this electric spark, in this embodiment, the electronic switch 16 for bypass is used.
Is installed.

FIG. 9 is a timing chart of the electric circuit diagram of FIG. The control device 15 turns on the bypass electronic switch just before the contact electrode is opened. While the contact electrode is still closed, most of the welding current flows to the contact electrode side because the contact electrode has a lower electrical impedance than the electronic switch for bypass.
When the contact electrode is opened, its electrical impedance becomes infinite, so that a bypass current flows through the bypass electronic switch, reducing the high voltage generated between the contact electrodes and suppressing welding while suppressing the occurrence of electric spark. It can be carried out. In FIG. 9, the dotted line portion of the voltage waveform between the contact electrodes is the high voltage waveform reduced by the bypass electronic switch.

FIG. 10 is an electric circuit diagram according to a fifth embodiment of the present invention. Here, instead of the bypass electronic switch 16 of FIG. 8, a bypass diode 17 having a forward drop slightly higher than the welding voltage is provided in parallel with the contact electrode and electrically forward with respect to the welding current. I have. This bypass diode has the effect of reducing the high voltage generated when the contact electrode is opened, like the electronic switch for bypass. In this case, the turn-on timing control is unnecessary, but instead, the voltage between the contact electrodes is reduced to the fore-drop voltage of the bypass diode.

By increasing the function of the control device 15 in the electric circuit diagram of FIG. 2, the sixth embodiment can be implemented. The control device 15 controls the charging circuit 13 to charge the ultra-large capacity capacitor 1 to a predetermined voltage. When welding is performed, the control device 15 detects the capacitor terminal voltage immediately before pressurizing the electrode tip 3, selects an appropriate energizing time programmed in advance according to the voltage value, and performs welding, so that the charging voltage of the capacitor is still high. That is, even if it is necessary to perform the next welding before the welding voltage is not sufficiently recovered, the energization time can be extended and corrected, so that there is no need to wait until the charging voltage reaches a predetermined value as in the related art. Further, even when the welding conditions are changed to lower ones, the current can be shortened and adjusted without the need to discharge the electric charge of the capacitor and reset it as in the conventional case.

FIG. 11 is an electric circuit diagram showing a seventh embodiment of the present invention. The control device 15 controls the charging circuit 13 to charge the ultra-large capacity capacitor 1 to a predetermined voltage. When welding is performed, the control device 13 detects the welding current every moment by the current sensor 18 while applying the welding current by pressurizing the electrode tip 3 and the accumulated value is changed to the accumulated value programmed in advance by the welding object. When reached, end welding. In this way, as described above, not only when the charging voltage of the capacitor, that is, the welding voltage does not sufficiently recover, but it is necessary to perform the next welding, as well as when the welding object has poor contact and the welding current Even if there is some disturbance such as a change in the welding speed, a predetermined welding quality can be ensured.

In the electric circuit diagram of FIG.
Claim 8 can be implemented by enhancing the function of. The control device 15 controls the charging circuit 13 to charge the ultra-large capacity capacitor 1 to a predetermined voltage. When performing welding, the control device 15 detects the welding current every moment by the current sensor 18 and the capacitor terminal voltage or the voltage between the electrode tips every moment by the voltage detection line while applying the welding current by pressurizing the electrode tip 3. Then, when the electric power, which is the product of the current and the voltage, that is, the cumulative value of the welding energy reaches a value programmed in advance by the welded material, the welding is terminated. In this way, the welding energy is always kept constant, so that a predetermined welding quality can be ensured even when various disturbances such as power supply fluctuations and load fluctuations occur.

Although the difference between the capacitor terminal voltage and the voltage between the electrode chips is the same in the electric circuit diagram, a voltage difference actually occurs due to the electric impedance of the gun arm and the shunt. In terms of detecting welding energy, it is desirable to mount a voltage detection wire at the position of the electrode tip. However, that part is the leading end of the welding operation, and is easily damaged by mechanical interference with a welded object or a jig, bending of a detection line, or welding scattering. Considering this point, detection of the capacitor terminal voltage does not have the above-mentioned problems and is advantageous for mounting, and the electric impedance of the gun arm and the shunt is considered to be almost a fixed value. It is also possible to subtract and convert to a voltage between electrode tips. Which of the capacitor terminal voltage and the voltage between the electrode tips is detected and controlled is selected in consideration of the above advantages and disadvantages.

[0043]

As described above, according to the first aspect of the present invention, not only conventional portable spot welding guns (C type and X type) but also stationary resistance welding machines, multi-welding machines, robot guns, etc. In comparison with a small welding machine for electronic parts, it is possible to eliminate problems caused by the size and weight of the welding transformer and gun, the burden of routing the secondary cable, the presence of a high voltage circuit, and the like. That is, the safety and durability of the resistance welding machine are improved, and the size and weight of the resistance welding machine are reduced.

According to the second aspect of the present invention, when the switch is opened and closed to switch on and off the welding current, the electrode tip and the welded article are kept in a pressurized state, so that an electric spark is generated. Can be suppressed.

According to the third aspect of the present invention, no voltage is applied to the electrode tip when the electrode tip comes into contact with the welded object even when the electrode tip is driven to sandwich the welded object and initially pressurized. No electric spark is generated between the workpiece and the weldment. At the point when the contact electrode contacts and conducts electricity, pressure is applied by the initial pressurization spring constant, so that the mechanical bounce between the electrode tip and the weldment, that is, the chattering phenomenon is small, and the electric spark is not applied to the contact electrode portion. It is in a state where it hardly occurs. Further, the contact electrode can be replaced so that good electrical contact can always be maintained.

According to the fourth aspect of the present invention, at the moment when the contact electrode is opened and an electric spark occurs, the power transistor or the power transistor installed in parallel with the contact electrode and electrically forward with respect to the welding current is provided. An electric switch such as a thyristor is turned on for a short time to reduce the high voltage generated between the contact electrodes, thereby suppressing electric spark.

According to the fifth aspect of the present invention, a high voltage generated between the contact electrodes is supplied to the forward drop through a diode provided in parallel with the contact electrodes and electrically forward with respect to the welding current. The electric spark is suppressed by reducing it.

According to the sixth aspect of the present invention, the welding conditions can be adjusted not only by the charging voltage but also by the energizing time as compared with the conventional capacitor welding machine. Further, even when the next welding is performed before the charging voltage of the capacitor, that is, the welding voltage is not sufficiently recovered, the energization time can be extended and corrected, so that it is not necessary to wait until the charging voltage reaches the predetermined charging voltage unlike the related art. Further, even when the welding conditions are changed to lower ones, the current can be shortened and adjusted without the need to discharge the electric charge of the capacitor and reset it as in the conventional case.

According to the seventh aspect of the invention, when the next welding is performed before the charging voltage of the capacitor, that is, the welding voltage is not sufficiently recovered, or when the welding current is changed due to poor contact, some disturbance may occur. Even if there is, a predetermined welding quality can be ensured.

According to the eighth aspect of the present invention, since the welding energy is always kept constant, a predetermined welding quality can be ensured even when various disturbances such as power supply fluctuations and load fluctuations occur.

[Brief description of the drawings]

FIG. 1 is an external view showing an embodiment when the present invention is applied to a portable spot welding gun.

FIG. 2 is an electric circuit diagram when the present invention is implemented.

FIG. 3 is a timing chart when the present invention is implemented.

FIG. 4 is an electric circuit diagram using an electronic switch in the embodiment of the present invention.

FIG. 5 is a structural view when an initial pressurizing unit is used in the embodiment of the present invention.

FIG. 6 is an external view showing a spot welding gun in which an initial pressurizing unit is applied to the embodiment of the present invention.

FIG. 7 is an electric circuit diagram of a spot welding gun in which an initial pressurizing unit is applied to the embodiment of the present invention.

FIG. 8 is an electric circuit diagram in which an initial pressurizing unit and a bypass electronic switch are applied to the embodiment of the present invention.

FIG. 9 is a timing chart of an electric circuit diagram for suppressing a spark by an electronic switch for bypass.

FIG. 10 is an electric circuit diagram in which an initial pressurizing unit and a bypass diode are applied to the embodiment of the present invention.

FIG. 11 is an electric circuit diagram showing a case where a current sensor is applied to an embodiment of the present invention.

[Explanation of symbols]

 1 Ultra large capacity capacitor 2 Shunt 3 Electrode tip (+) 4 Gun arm 5 Electrode tip (−) 6 Pressure actuator 7 Contact electrode 8 Spring 9 Insulating plate 10 Cooling water 11 Welding object 12 Initial pressurization unit 13 Charging circuit 14 Electronic switch 15 Control device 16 Electronic switch for bypass 17 Diode for bypass 18 Current sensor

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B23K 11/25 511 B23K 11/25 511

Claims (8)

[Claims] In a resistance welding machine for welding a metal plate by sandwiching it between opposed electrode tips and applying a current while applying a pressing force thereto, the resistance is directly applied to the electrode tips without passing through a welding transformer. Equipped with an ultra-large capacity capacitor that supplies welding current and a charging circuit that charges this capacitor up to the welding voltage
A capacitor-type resistance welding machine characterized in that an electrode tip is driven, a part of the electric charge accumulated in a capacitor is sandwiched by a welding object, a welding current is applied to perform welding, and the electrode tip is opened after welding is completed. . 2. In a resistance welding machine in which a welded piece of a metal plate is sandwiched between opposing electrode tips and energized and welded while applying a pressing force thereto, the electrode tips are directly connected to the electrode tips without passing through a welding transformer. Equipped with an ultra-large capacity capacitor that supplies welding current, a charging circuit that charges the capacitor up to the welding voltage, and a switch with mechanical contacts or electronic switches that electrically opens and closes the welding circuit. After sandwiching and initial pressurizing, a part of the electric charge accumulated in the capacitor is discharged by closing the switch for a predetermined energizing time, welding current is applied, welding is performed, and the electrode tip is opened after welding is completed. A capacitor type resistance welding machine characterized by the following. 3. A resistance welding machine in which a welded metal plate is sandwiched between opposing electrode tips and energized and welded while applying a pressing force thereto, wherein the electrode tips are directly connected to the electrode tips without passing through a welding transformer. An ultra-high-capacity capacitor that supplies welding current, a charging circuit that charges the capacitor up to the welding voltage, a contact electrode that opens and closes the welding circuit behind one of the electrode tips, A spring for initial pressurization to cut off is provided, and after the electrode tip is driven to sandwich the welded material and pressurized initially with the spring pressure for initial pressurization, the spring is further depressed and the contact electrode is brought into contact for a predetermined energizing time. To close off the welding circuit to discharge a part of the electric charge stored in the capacitor, apply welding current, perform welding, and open the electrode tip after welding is completed. Capacitor resistance welding machine according to. 4. A capacitor type resistance welding machine according to claim 3, further comprising an electronic switch such as a power transistor or a thyristor in parallel with said contact electrode and electrically forward with respect to a welding current. A capacitor-type resistance welding machine characterized in that by turning on an electronic switch for a short time at the moment of termination, a high voltage generated between the contacts when the contact electrodes are opened is reduced to suppress electric spark. 5. A capacitor type resistance welding machine according to claim 3, further comprising a diode having a forward drop slightly higher than a welding voltage in parallel with said contact electrode and electrically forward with respect to a welding current. A capacitor-type resistance welding machine characterized in that a high voltage generated between contacts when a contact electrode is opened is reduced to suppress an electric spark. 6. A resistance welding machine in which a welded metal plate is sandwiched between opposing electrode tips, and a current is applied while applying a pressure to the welded metal plate to weld the metal plates directly without passing through a welding transformer. Equipped with an ultra-large capacity capacitor for supplying welding current, a charging circuit for charging the capacitor up to the welding voltage, and capacitor terminal voltage detecting means, and a predetermined energizing time programmed in advance based on the value of the capacitor terminal voltage detected at the start of welding. A capacitor-type resistance welding machine characterized in that a part of the electric charge stored in a capacitor is discharged by only closing a welding circuit, and welding is performed by supplying a welding current. 7. A resistance welding machine in which a welded metal plate is sandwiched between opposing electrode tips and energized and welded while applying a pressing force to the electrode tips, without passing through a welding transformer directly to the electrode tips. A super-capacity capacitor for supplying a welding current, a charging circuit for charging the capacitor to a welding voltage, and a welding current detecting means are provided, and the electrode tip is pressurized to discharge the electric charge accumulated in the capacitor and supply the welding current. A capacitor-type resistance welding machine characterized by detecting a welding current while performing welding, and terminating energization when a cumulative value of the welding current reaches a predetermined value programmed in advance. 8. A resistance welding machine in which a welded metal plate is sandwiched between opposing electrode tips and energized and welded while applying a pressing force thereto, wherein the electrode tips are directly connected to the electrode tips without passing through a welding transformer. A capacitor for supplying a welding current, a charging circuit for charging the capacitor to a welding voltage, welding current detecting means, and capacitor terminal voltage or electrode tip voltage detecting means; The welding current and voltage are detected while the welding is performed by discharging the electric charge accumulated in the welding current and flowing the welding current, and the electric power that is the product of the welding current and the voltage, that is, the accumulated value of the welding energy is reduced to a predetermined value programmed in advance. A capacitor type resistance welding machine characterized by terminating energization when it reaches.