JP2001300739A - Capacitor bank for resistance welding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a capacitor bank for resistance welding machine which is small, lightweight, is rich in its portability and whose utilizing efficiency is high. SOLUTION: The capacitor bank 5 consists of one capacitor or two or more capacitors connected in series or in parallel, and is connected to a charging power source in parallel. A weld zone 9 is connected through the capacitor bank 5 and a switching circuit 7 for weld control, and welding is performed by discharging from this capacitor bank 5. Charging from the charging power source to the capacitor bank 5 and a control including an energizing time to the switching circuit 7 for weld control, are performed by a control part 13. The time constant of the capacitor bank 5 is set to 0.05 sec to 10 sec.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a capacitor bank for a resistance welding machine, and more particularly to a capacitor bank for a resistance welding machine having a small size, light weight, high portability and high energy use efficiency.

[0002]

2. Description of the Related Art Conventionally, as a welding method used in a resistance welding machine, an electric current is passed through a contact portion of a material to be joined, and a portion to be joined is locally heated by heat generated by electric resistance generated there. It is known to perform welding by heating and further applying a mechanical pressure. In this welding method, a current of 100 A to 100 A
Although tens of thousands of amperes are used, a voltage of about 2 to 4 V is generally sufficient, and low-voltage, large-current power is often obtained from a motive power source via a transformer.

[0003] In this resistance welding machine, the transformer and the welding means are often separated and connected by a long cable so that the welding means can be moved freely in order to improve the workability of the welding operation. However, in this case, a large current required for welding flows through the connection cable, which causes a large loss.To compensate for the loss, a large transformer and a durable cable are required. For example, there were problems such as an increase in energy use efficiency and an increase in price.

On the other hand, there has been proposed a resistance welding machine in which electric energy is stored in a capacitor, and this electric energy is directly supplied to a material to be welded and used (Japanese Patent Laid-Open No. 2-379).
No. 72 (capacitor discharge type welding device). In this resistance welding machine, an input power supply is connected to a primary side of a transformer. A rectifier circuit, a switching element for controlling charging of the capacitor and a capacitor are connected to the secondary side of the transformer, and a welding means and a material for welding the capacitor in parallel to the capacitor are connected.

[0005] In a resistance welding machine using this capacitor,
The capacitor portion is relatively small and lightweight. For this reason,
There is an advantage that the connecting cable for connecting the capacitor portion and the welding means can be shortened, and the entire resistance welding machine can be reduced in size, weight, portability, and energy use efficiency.

[0006]

Since the capacitor has a DC internal resistance, a voltage drop occurs due to the DC internal resistance, and the discharge current is limited.
For example, if the voltage applied to the capacitor is 2.5 V and the internal resistance is 5 mΩ, the maximum dischargeable current is 500 A
In this case, the welding current in the resistance welding machine is small, and the material that can be welded is limited.

Further, in addition to the internal resistance of the capacitor, even if the connecting cable from the capacitor to the welding means is shortened, there is an electric resistance in the path, and there is a contact resistance between the materials to be welded. Will be done.

For this reason, a method of increasing the voltage by connecting capacitors in parallel and equivalently lowering the resistance value of the entire capacitor bank or connecting the capacitors in series to increase the obtained current is considered. Can be

However, in the resistance welding method, a large current is required in order to concentrate heat near the welded portion. However, there is a certain limitation on the energization time, and the current is generally in the range of 0.05 to 10 seconds.

When the number of capacitors and the voltage of the capacitors are increased, the electric energy stored in the capacitors can be reduced.
Since the electric energy supplied for welding is small, the electric energy is not effectively used, and the energy use efficiency is reduced.

Further, increasing the number of connected capacitors increases the overall size, and therefore sacrifices miniaturization, weight reduction, and portability. Further, since heat is also generated in the capacitor itself due to the internal resistance, the capacitor is deteriorated, and the reliability is affected.

Therefore, as a capacitor used in such a resistance welding machine, a capacitor having a low internal resistance and capable of storing a sufficient and optimal electric energy for welding has been demanded. Was not known.

The present invention has been made in view of such conventional problems, and has as its object to provide a compact, lightweight, highly portable capacitor bank for a resistance welding machine with high energy use efficiency.

[0014]

Therefore, according to the present invention (claim 1), the input side is connected to a power supply, and the output side is connected to the charge control means which can be adjusted to a predetermined DC voltage, and is connected in parallel to the charge control means. A capacitor bank to be charged and charged, welding means connected in parallel with the capacitor bank via a switching circuit, and a DC voltage output from the charge control means to control the switching circuit to perform the welding. A capacitor bank constituting a resistance welding machine having a control means for controlling the energization time to the means, comprising a single capacitor or two or more capacitors connected in series or in parallel, and having a time constant of 0.05 seconds or more. It is characterized by being in a range of 10 seconds.

The charging control means has an input side connected to a power supply and an output side adjustable to a predetermined DC voltage. The capacitor bank includes one capacitor or two or more capacitors connected in series or in parallel, and is connected to the charge control means. Then, the capacitor bank is charged by the charge control means.

The welding means is connected to the capacitor bank via a switching circuit, and performs welding by discharging from the capacitor bank. The control means controls the DC voltage output from the charge control means, detects the state of charge of the capacitor bank, and controls the switching circuit based on the detected signal to control the energization time to the welding means. . However, it is preferable that the control means also detects a state such as pressurization of the welding means, and controls the energization time to the welding means including the detected signal.

The capacitor bank ideally can store enough electrical energy to provide good welding,
Desirably, there is no internal resistance and no energy consumption in the capacitor bank. However, since the capacitors constituting the capacitor bank actually have an internal resistance, the time constant of the capacitor bank is set in the range of 0.05 seconds to 10 seconds, which is almost equal to the range of the energizing time during welding in the resistance welding machine. This improves energy use efficiency.

This is to provide a resistance welding machine with high energy use efficiency in which the required number of capacitors is minimized and the electric energy discharged from the capacitor bank is used by the welding means in the most efficient manner. Can be done.
For this reason, the resistance welding machine can be made small, lightweight and highly portable.

Further, the present invention (claim 2) is characterized in that the capacitor is an electric double layer capacitor.

The electric double layer capacitor can store a large amount of electric energy, so that the number of capacitors can be reduced. Therefore, the resistance welding machine can be made smaller, lighter, and more portable.

Further, the present invention (claim 3) is characterized in that a cooling means is provided.

In order to prevent deterioration of the performance of the capacitor due to Joule heat generated in the DC internal resistance in the capacitor,
Cooling means is provided. The cooling means may be any method such as air cooling, water cooling, and electronic cooling.

[0023]

Embodiments of the present invention will be described below. FIG. 1 shows a circuit diagram of an embodiment of the present invention. In FIG. 1, a charge control unit 3 is connected to input terminals 1A and 1B of a resistance welding machine 10.

The charging controller 3 is supplied with electric power from a DC power supply (not shown), and its output voltage is adjustable. One end of the output terminal of the charging control unit 3 is connected to one end of the capacitor bank 5 and one end of the switching circuit 7 for welding control.

The other end of the welding control switching circuit 7 is
It is connected to one end of the weld 9. In addition, the charge control unit 3
Are connected to the other end of the capacitor bank 5 and the other end of the welded portion 9.

A cooling fan 11 is provided on the side of the capacitor bank 5. The control unit 13 extracts a signal from each unit of the resistance welding machine 10 and controls each unit. The capacitor bank 5 is configured by connecting a plurality of electric double layer capacitors (not shown) connected in parallel in several stages in series.

Further, a material (not shown) to be welded is sandwiched in the welded portion 9 at a predetermined pressure. The pressure at this time is detected by a pressure sensor (not shown), and the detected pressure signal is input to the control unit 13. Further, the control section 13 detects and inputs the voltage of the capacitor bank 5 and
Thereby, the state of charge of the capacitor bank 5 can be detected.

Next, the operation of the embodiment of the present invention will be described. In FIG. 1, an electric double layer capacitor is used as a capacitor used for the capacitor bank 5 in the resistance welding machine 10 in that large electric energy can be stored. The capacitor bank 5 is charged by the charge control unit 3 to a voltage required for welding.

At this time, under the control of the control unit 13, the battery is charged while being compared with the voltage signal detected from the capacitor bank 5. When the completion of the charging is confirmed and the pressure signal exceeds a predetermined value, the welding control switching circuit 7 is turned ON, and the welding control switching circuit 7 is discharged from the capacitor bank 5.
After a predetermined energizing time, the welding control switching circuit 7 is turned off.
F. By this discharge, welding is performed in the welded portion 9.

As a characteristic of the capacitor bank 5 used in the resistance welding machine 10, it is desirable from the viewpoint of energy use efficiency that a large amount of energy stored in the capacitor bank 5 can be discharged within the energization time. On the other hand, in general, the time constant t (sec) of a capacitor is given as a measure of the characteristics of the capacitor.

The time constant t is the capacitance C of the capacitor.
(F), when the DC internal resistance of the capacitor is R (Ω),
It is represented by t = C · R (sec). When the capacitor is discharged only by the DC internal resistance of the capacitor in an ideal short circuit state without applying an external load, the time constant t is up to 1 / e of the capacitor voltage before discharging (e: natural logarithm), that is, 36.8
% Is a measure of the discharge time before dropping to%.

At this time, the value of the DC internal resistance R is a constant current.
It is a value expressed as R = ΔV / I (Ω) from the voltage drop ΔV (V) after 10 msec when discharging at I (A). Therefore, the time constant of the capacitor bank 5 is desirably close to the energization time of the welding control switching circuit 7, and varies depending on the size of the resistance welding machine 10, the object to be welded, and the purpose of welding. In the range of 05-10 seconds,
Preferably 0.08 to 5 seconds, more preferably 0.1 to 5 seconds
The range is 3 seconds.

Since the capacitor bank 5 is composed of a plurality of electric double layer capacitors having a fixed capacitance and internal resistance, the series and parallel connection of the capacitors is set so that the time constant of the capacitor bank 5 becomes as close as possible to the energization time. Although it is difficult to set the combination, in consideration of such energy use efficiency, the combination of the series-parallel connection is adjusted so that the time constant of the capacitor bank 5 becomes closest to the energization time.

By adjusting in this manner, the ratio of the electric energy supplied to the welding to the electric energy stored in the capacitor bank 5 can be increased, and the electric energy can be used effectively. In addition, the number of connected electric double layer capacitors is minimized, which leads to a reduction in the size and weight of the resistance welding machine 10, and further improves portability.

When the resistance welding is energized, Joule heat is generated due to the DC internal resistance in the electric double layer capacitor, and when welding is repeated frequently, the temperature of the capacitors constituting the capacitor bank 5 rises due to the Joule heat. Would. An increase in the temperature of the electric double layer capacitor causes gas generation inside the cell and deterioration of the current collecting portion in the electric double layer capacitor cell, thereby greatly deteriorating the performance of the electric double layer capacitor.

For this reason, a cooling fan 11 is provided to prevent the temperature of the electric double layer capacitor from rising. Maintaining the temperature of the electric double layer capacitor at 45 ° C. or less, preferably 35 ° C. or less, more preferably 30 ° C. or less, from the viewpoint of preventing the deterioration of the electric double layer capacitor performance and extending the durability of the resistance welding machine 10 preferable. However, the cooling fan 11
Instead, another cooling method such as water cooling may be used.

In this embodiment, the capacitor bank 5
Although the electric double-layer capacitor has the above-described configuration, the configuration and connection can be changed in consideration of the required welding current and path resistance, material resistance, internal resistance and capacitance of the capacitor itself.

As long as the internal resistance of the capacitor is low and a capacity capable of accumulating current and electric energy that can be welded is obtained, the capacitor bank 5 may be composed of one capacitor. In this case, it is preferable because the size and weight are further reduced, and there is no particular limitation as long as the same effect can be obtained within the same range of the time constant without being limited to this embodiment.

Further, in this embodiment, the input terminals 1A, 1B
Although the configuration for supplying DC power to the power supply has been shown, the power may be further rectified and supplied from a power AC power supply via a transformer, or the controller 13 and these may be collectively installed at a remote position. In this case, the charging current to the capacitor bank 5 is sufficiently smaller than the welding current.
Up to a small loss.

[0040]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the configuration shown in FIG. 1, a capacitor bank 5 in which 20 electric double-layer capacitors having a rated voltage of 2.5 V, a capacitance of 1000 F, and a DC internal resistance of 2.8 mΩ are connected in parallel in two stages. The capacitor bank 5 is charged with a DC power supply of 5 V and 100 A, and a pressure of 2450 is used.
Under the conditions of N and 0.2 seconds of electric current, two galvanized steel sheets having a thickness of 0.6 mm were welded. This was performed at intervals of 10 seconds, and good welding results were obtained.

In this case, the capacitance of the entire capacitor bank 5 is 10000 F and the resistance is 0.3 mΩ, energy sufficient for welding is accumulated, and a current sufficient for welding can be discharged. At this time, the time constant represented by the product of the capacitance and the resistance is 3 seconds.

In order to suppress a rise in temperature due to self-heating due to the internal resistance of the capacitor, a cooling fan 11 is installed near the capacitor bank 5 so that the temperature does not exceed 45 ° C. in consideration of the air volume and the air direction. did.

[0043]

As described above, according to the present invention, a resistance welding machine having good energy use efficiency can be obtained while using as few capacitors as possible. For this reason, the resistance welding machine can be made small, lightweight and highly portable.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1A, 1B input terminal 3 charge control part 5 capacitor bank 7 switching circuit for welding control 9 welding part 10 resistance welding machine 11 cooling fan 13 control part

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Shoichi Takeuchi, Inventor Asahi Glass Co., Ltd., 1150 Hazawa-cho, Kanagawa-ku, Yokohama, Kanagawa Prefecture (72) Inventor Hiroshi Ota 1-1-1, Suehirocho, Tsurumi-ku, Yokohama-shi, Kanagawa Asahi Glass Co., Ltd. (72) Inventor Katsuharu Ikeda 1150 Hazawa-cho, Kanagawa-ku, Yokohama-shi, Kanagawa Prefecture Asahi Glass Co., Ltd. F-term (reference) 5H790 BA03 CC01 CC06 CC06 EA01 EA11 EB02

Claims (3)

[Claims] An input side is connected to a power supply, an output side is capable of adjusting a DC voltage to a predetermined DC voltage, a capacitor bank connected in parallel to the charge control means and charged, and the capacitor bank and a switching circuit. Welding means connected in parallel through, controlling the DC voltage output from the charging control means, controlling the switching circuit,
A capacitor bank constituting a resistance welding machine including a control means for controlling the current supply time to the welding means, comprising a single capacitor or two or more capacitors connected in series or in parallel, and having a time constant of 0.05. Seconds to 10
Capacitor bank for resistance welding machine, characterized in the range of seconds. 2. The capacitor bank according to claim 1, wherein the capacitor is an electric double layer capacitor. 3. The capacitor bank for a resistance welding machine according to claim 1, wherein cooling means is provided.