JP2001300740A - Resistance welding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resistance welding machine from which a high current free from a fluctuation can be taken out without drawing on an environmental temperature and the calorification of a capacitor itself, whose utilizing efficiency of energy is satisfactory and with a long life. SOLUTION: After making data of a relation between a temperature and the voltage of a charge control part 3 so that a current value in the beginning of a discharge, which is made to flow from a capacitor bank 5 to a weld zone 9, becomes almost constant even when the temperature is changed, it is stored in a control part 13 in advance as a table. By calculating the voltage of the charge control part 3, which corresponds to this temperature according to the table, a charge control is performed in the control part 13 so that the voltage of the charge control part 3 becomes this calculated voltage value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resistance welding machine, and more particularly to a resistance welding machine capable of extracting a large current without fluctuation regardless of environmental temperature or heat generation of a capacitor itself, having good energy use efficiency, and having a long service life. .

[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 mechanical pressure. In this welding method, a current of 100 A is used in order to use heat generated by electric resistance.
Although a voltage of about 2 to 4 V is generally sufficient, a low-voltage, large-current power is often obtained from a power AC power supply 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]

However, since a capacitor has a DC internal resistance (hereinafter simply referred to as an internal resistance) due to the resistance of an electrode or an electrolytic solution which is a constituent element thereof, when the capacitor is discharged, the internal resistance is reduced. A voltage drop occurs due to the resistance. It is known that the internal resistance changes depending on the temperature of the capacitor.

In a resistance welding machine using such a capacitor, the current at the beginning of discharge is an important factor that determines the welding quality. Therefore, it is difficult for the internal resistance to change due to the environmental temperature at which the capacitor is installed and the current value to change. And the welding quality was not constant, which had a bad effect.

Further, when welding is repeatedly performed and charging and discharging of the capacitor with a large current are repeated, the temperature of the capacitor itself rises due to heat generated by the internal resistance. For this reason, there is a problem that the internal resistance changes, which also has a bad effect.

It is also possible to insert a variable compensation resistor in the circuit so as to compensate for the change of the internal resistance due to temperature and to make the resistance constant throughout the circuit. Heat is also generated in the resistor, and energy efficiency is deteriorated, and cooling of the compensating resistor is required.

Therefore, there has been a demand for a capacitor-type resistance welding machine in which the current value at the beginning of discharge is constant regardless of the temperature.

On the other hand, it is generally known that the life of a capacitor is greatly affected by the operating temperature and also by the applied voltage. For this reason, it is preferable to use the capacitor at a low temperature and a low voltage as much as possible, and it has been demanded to extend the life of the capacitor and, consequently, the life of the entire device by optimal charge / discharge control.

The present invention has been made in view of such conventional problems, and a large current without fluctuations can be taken out irrespective of the environmental temperature and heat generation of the capacitor itself. It is intended to provide a welding machine.

[0013]

Therefore, according to the present invention (claim 1), an input side is connected to a power supply, and an output side is a charge control means for outputting an adjustable DC voltage, and the charge control means is connected in parallel to the charge control means. A capacitor bank connected and charged to the capacitor bank, connected to the capacitor bank via a switching circuit,
Welding means for performing welding by discharging from the capacitor bank, temperature detecting means for detecting the temperature of the capacitor bank, and necessary for making the initial current value flowing from the capacitor bank almost constant regardless of the temperature. A charging voltage calculating means for calculating a charging voltage of the capacitor bank from the data based on the temperature detected by the temperature detecting means based on data of a relationship between the charging voltage of the capacitor bank and the temperature obtained in advance; Control means for controlling the charge control means for charging the capacitor bank with the voltage calculated by the voltage calculation means.

The charging control means has an input side connected to a power supply and an output side adjustable to a predetermined DC voltage. A capacitor bank consists of one capacitor or two or more capacitors connected in series or in parallel. And it is connected in parallel to this charge control means and charged. The welding means is connected to the capacitor bank via a switching circuit, and performs welding by discharging from the capacitor bank.

The temperature detecting means detects the temperature of the capacitor bank. Then, even if the temperature changes, the charging voltage of the capacitor bank required for each temperature is acquired in advance so that the current value of the initial stage of the discharge flowing from the capacitor bank to the welding means is substantially constant, and a table or a table is obtained from the data. Create a function.

The charging voltage calculating means calculates the charging voltage to the capacitor bank by using a table or a function based on the temperature detected by the temperature detecting means. The control means controls the charge control means to charge the capacitor bank to the voltage calculated by the charge voltage calculation means.

As described above, a large current that does not fluctuate regardless of the environmental temperature or the heat generated by the capacitor itself can be taken out of the capacitor bank, and the welding quality can be stabilized.

Further, according to the present invention (claim 2), cooling means for cooling the capacitor bank, heating means for heating the capacitor bank, and comparing the temperature detected by the temperature detecting means with a set temperature. A temperature comparing means for calculating a temperature difference, and a control means for controlling the cooling means and / or the heating means based on the temperature difference calculated by the temperature comparing means.

The cooling means cools the capacitor bank.
The heating means heats the capacitor bank. The temperature comparing means compares the temperature detected by the temperature detecting means with the set temperature to calculate a temperature difference. The temperature control means controls the cooling means and / or the heating means based on the temperature difference calculated by the temperature comparison means.

This control may be turned on and off when the temperature difference reaches a predetermined value, or the heating amount and the cooling amount may be varied according to the magnitude of the temperature difference. Is also good. If you turn on and off,
It can be configured at low cost and can be adjusted to almost the set temperature.

As described above, in addition to the effect of the first aspect, the energy use efficiency of the capacitor bank is good and the life of the resistance welding machine can be extended.

Further, the present invention (claim 3) is characterized in that the capacitor bank comprises one electric double layer capacitor or two or more electric double layer capacitors connected in series or in parallel.

An electric double layer capacitor is used as a capacitor used in the resistance welding machine. An electric double layer capacitor can store large electric energy and does not involve a chemical reaction unlike a battery. Therefore, deterioration due to repeated charging and discharging is extremely small, and can be used as a maintenance-free power storage element. In addition, the constituent materials do not contain harmful substances such as heavy metals, which is preferable in terms of environment.

[0024]

Embodiments of the present invention will be described below. FIG. 1 shows a configuration diagram of the first embodiment of the present invention. In FIG. 1, input terminals 1A, 1
B is connected to the charge control unit 3. Power is supplied to the input terminals 1A and 1B from a power source (not shown). 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 thermocouple 11 corresponding to a temperature detecting means is provided on the front wall surface of the capacitor bank 5, and an output signal of the thermocouple 11 is input to the control unit 13. Further, the voltage of the capacitor bank 5 is detected as a voltage signal 15 and is similarly input to the control unit 13.

The capacitor bank 5 is formed by connecting a plurality of electric double layer capacitors (not shown) connected in parallel in several stages in series. Also, in the welded portion 9,
A material (not shown) to be welded is held 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.

Next, the operation of the first embodiment of the present invention will be described. In FIG. 1, an electric double layer capacitor is used for a capacitor used in the resistance welding machine 10 in that large electric energy can be stored. FIG. 2 shows the result of measuring the temperature dependence of the internal resistance of the electric double layer capacitor. As shown in FIG. 2, the internal resistance of the electric double layer capacitor is large at low temperatures and small at high temperatures.

Therefore, even if the temperature changes, in order to make the current value of the initial stage of the discharge flowing from the capacitor bank 5 to the welding portion 9 substantially constant, as shown in FIG. It is necessary to change the voltage and the charging voltage of the capacitor bank 5.

When this voltage is set, calculation is performed including the resistance due to wiring and the like (the charging voltage of the capacitor bank 5 by the charge control unit = current value at the initial stage of discharge × internal resistance and total resistance value including resistance due to wiring and the like). )
An actual welding experiment of the material may be performed, and the current may be calculated by an experiment such as measuring a current flowing through the welded portion 9.

The relationship between the temperature and the charging voltage of the capacitor bank 5 by the charging control unit 3 is converted into data and stored in the control unit 13 in advance as a table. The control unit 13 is constituted by a personal computer. Then, based on the temperature signal input from the thermocouple 11, the charging voltage of the capacitor bank 5 corresponding to this temperature is calculated based on the table.

However, the charging voltage of the capacitor bank 5 may be calculated by creating a function obtained from the relationship between the temperature and the charging voltage obtained by the experiment, without depending on the table.
Thereafter, the control unit 13 performs charge control so that the capacitor bank 5 is charged to the voltage value calculated by the charge control unit 3.

At this time, the calculated voltage value is set as a set voltage value, and charged while being compared with a voltage signal detected from the capacitor bank 5. And this charging is completed,
When the pressure signal exceeds a predetermined value, the welding control switching circuit 7 is turned on, the capacitor bank 5 is discharged, and after a predetermined energizing time, the welding control switching circuit 7 is turned off. By this discharge, welding is performed in the welded portion 9.

As described above, the change in the internal resistance due to the temperature of the capacitor bank 5 is compensated, and the current flowing through the welding portion 9 at the initial stage of the discharge becomes constant regardless of the temperature.

Next, FIG. 4 shows a configuration diagram of a second embodiment of the present invention. The same elements as those in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted. In FIG. 4, a cooling fan 17 serving as a cooling means is provided on the side of the capacitor bank 5 in the resistance welding machine 20.

A heater 19 as a heating means is attached to a side surface of each electric double layer capacitor. Heater 1
9 is a silicon rubber heater, for example. The cooling fan 17 and the heater 19 are controlled by the control unit 13.

Next, the operation of the second embodiment of the present invention will be described. The temperature characteristics of the internal resistance of an electric double layer capacitor
Due to the characteristics shown in FIG. 2, it is difficult to discharge a large current at a relatively low temperature side, and it is easy to perform a discharge at a high temperature. From the viewpoint of large current discharge, it is preferable that the discharge is maintained at a high temperature side. .

However, the life of the electric double layer capacitor is
It is known that the effect of the use temperature is large, and it is generally known that if the temperature is lowered by 10 ° C., the service life is doubled, so that it is not preferable that the electric double layer capacitor becomes high temperature.

On the other hand, when the electric double-layer capacitor is installed in a low-temperature environment and is used, since the internal resistance is large, it is difficult to discharge a large current, and the charging voltage is increased. As a factor affecting the life of the electric double layer capacitor, there is an effect of the applied voltage in addition to the operating temperature, and it is preferable to set the charging voltage as low as possible. For this reason, it is preferable to set and maintain the electric double layer capacitor at a certain intermediate predetermined temperature.

Therefore, a cooling fan 17 and a heater 19 are added as shown in FIG. The cooling fan 17 takes into consideration the flow of the wind in the capacitor bank 5 so that the electric double layer capacitors in the capacitor bank 5 are blown to the respective electric double layer capacitors as uniformly as possible, and the thermocouple 11 is not directly blown by the wind. I made it.

When the temperature of the condenser bank 5 exceeds the set temperature, the flow rate of the cooling fan 17 is controlled by the control unit 13 so that the flow rate is changed according to the difference between the temperature of the capacitor bank 5 and the set temperature. It is controlled by a control method or the like.

On the other hand, the heater 19 is connected to the capacitor bank 5
Is lower than the set temperature, the control unit 13 controls by the PID control method or the like so as to be heated according to the difference between the temperature of the capacitor bank 5 and the set temperature. However, PID
Control may be performed by ON or OFF regardless of the control method or the like.

As described above, in addition to controlling the charging voltage of the capacitor bank 5 by the signal from the thermocouple 11 as described in the first embodiment of the present invention, the temperature of the capacitor bank 5 is controlled in the second embodiment of the present invention. Control to keep it constant.

As a result, as compared with the first embodiment, the present embodiment is more effective against temperature rise due to self-heating of the capacitor due to charging / discharging of a large current due to repeated welding, regardless of the environmental temperature. Further, in this case, since the temperature of the capacitor does not rise excessively, the life of the capacitor can be extended.

In this embodiment, the cooling fan 17 is used as the cooling means. However, other cooling methods such as water cooling and electronic cooling can be used without being limited to this. Similarly, other heaters can be used for the heating means, and the entire condenser bank may be installed in a thermostat.

In both the first embodiment and the second embodiment, it is possible to change the charging voltage of the capacitor bank 5 including a change with time of the welded portion 9 and a change with the frequency of use. Further, in the case where charging and discharging are repeated in a short period of time with respect to the period of temperature change, the current flowing through the welded portion 9 during welding is detected, and the current value and the temperature are taken into consideration. Can also be changed.

Further, although the thermocouple 11 is used as the temperature detecting means, other detecting elements such as a thermistor may be used without being limited to this. Further, the thermocouple 11 is stuck on only the front wall surface of one electric double layer capacitor, but a plurality of thermocouples 11 may be stuck on the surface wall surface of a plurality of electric double layer capacitors, and processing may be performed from their measured temperatures. It is possible.

Further, when manufacturing the electric double layer capacitor itself, it is possible to measure the temperature inside the electric double layer capacitor by enclosing a small and thin thermistor or the like. This arrangement is desirable in that the temperature of the capacitor itself can be accurately detected.

Although a commercially available personal computer is used as the control unit 13, it is possible to use a one-chip CPU or the like to make a dedicated circuit and reduce the size. In this case, the entire apparatus can be reduced in size.

[0049]

(Embodiment 1) In the configuration of FIG. 1, the capacitor bank 5 has a rated voltage of 2.5 V and a capacitance of 100 V.
A series connection of 20 0F electric double layer capacitors was further connected in two stages in series. The temperature characteristic of the internal resistance (Ri) of the used electric double layer capacitor is shown in FIG.
It is shown in.

For example, the internal resistance (Ri) at 25 ° C.
Is 2.65 mΩ. Therefore, the internal resistance (Rib) of the entire capacitor bank 5 at 25 ° C. is 0.265 m
Ω. And the temperature range used is 5 ° C to 45 ° C
In this range, the welding current of 7000 A including the internal resistance (Rib), the resistance of the wiring and the welding means, and the contact resistance of the material to be resistance-welded (0.3 mΩ in total) is always taken out. The charging voltage (Vc) was changed according to the temperature characteristics shown in FIG. Here, the charging current to the capacitor bank 5 was 100 A, and was supplied from a DC power supply.

With this configuration, the resistance welding machine 10 can be operated at room temperature 2
It was set in a room at 3 ° C., and a welding experiment was performed on two 0.6 mm-thick galvanized steel sheets under the conditions of a pressing force of 2450 N and a current of 0.2 second, and good welding results were obtained. When the welding was repeated, the temperature of the capacitor bank 5 increased due to charging and discharging, but similarly good welding results were obtained without any influence.

A similar experiment was conducted separately at room temperature of 10 ° C., but good welding results were obtained. In this embodiment, the temperature range is set to 5 ° C. to 45 ° C., and when the temperature of the capacitor bank 5 deviates from the above temperature range, the charging / discharging operation is not performed for safety.

Example 2 As shown in FIG. 4, a cooling fan 17 and a heater 19 were provided, and a welding experiment was performed in the same manner as in Example 1 except that the set temperature was set at 25 ° C. It was kept almost constant and the welding results were good.

In this embodiment, the electric double layer capacitor has the same configuration and connection as the capacitor bank 5 in the first embodiment. However, in consideration of the current flowing through the welding portion 9 and the resistance of the wiring, the capacitance and the capacitance are further reduced. It is also possible to consider and select the characteristics of the electric double layer capacitor such as the internal resistance and change the connection configuration, and there is no particular limitation.

Further, depending on the characteristics of the electric double layer capacitor, the welding material, etc., the capacitor bank 5 may be constituted by one electric double layer capacitor. In this case, the size and weight are further reduced, which is preferable. If a similar effect can be obtained without being limited to the present embodiment, there is no particular limitation.

[0056]

As described above, according to the present invention, it is possible to take out a large current that does not fluctuate irrespective of the ambient temperature or the heat generated by the capacitor itself, and to stabilize the welding quality.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a first embodiment of the present invention.

Fig. 2 Temperature dependence of internal resistance of electric double layer capacitor

FIG. 3 is a diagram showing a charging voltage with respect to a temperature of a capacitor bank using an electric double layer capacitor.

FIG. 4 is a configuration diagram of a second 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, 20 Resistance welding machine 11 Thermocouple 13 Control part 15 Voltage signal 17 Cooling fan 19 Heater

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H02J 7/10 H01G 9/00 531 (72) Inventor Shoichi Takeuchi 1150 Hazawacho, Kanagawa-ku, Yokohama-shi, Kanagawa Prefecture Asahi Glass (72) Inventor Hiroshi Ota 1-1-1 Suehirocho, Tsurumi-ku, Yokohama-shi, Kanagawa Prefecture Inside Asahi Glass Co., Ltd. (72) Inventor Katsuharu Ikeda 1150 Hazawacho, Kanagawa-ku, Yokohama-shi, Kanagawa Prefecture Asahi Glass Co., Ltd. Reference) 5G003 AA01 BA01 CA11 CB01 CC02 DA06 DA15 FA08 GC05

Claims (3)

[Claims] An input side is connected to a power supply, and an output side is a charge control means for outputting an adjustable DC voltage; a capacitor bank connected in parallel to the charge control means for charging; Welding means connected through a circuit and performing welding by discharging from the capacitor bank, temperature detecting means for detecting the temperature of the capacitor bank, and a current value at the initial stage of discharge flowing from the capacitor bank regardless of the temperature. Charging for calculating the charging voltage of the capacitor bank from the data based on the temperature detected by the temperature detecting means, based on data on the relationship between the charging voltage of the capacitor bank and the temperature acquired in advance, which is necessary to make the voltage substantially constant. Controlling a voltage calculating means and the charging control means for charging the capacitor bank with the voltage calculated by the charging voltage calculating means; A resistance welding machine comprising: 2. A cooling means for cooling the capacitor bank, a heating means for heating the capacitor bank, and a temperature comparing means for comparing a temperature detected by the temperature detecting means with a set temperature and calculating a temperature difference. 2. The resistance welding machine according to claim 1, further comprising control means for controlling the cooling means and / or the heating means based on the temperature difference calculated by the temperature comparing means. 3. The capacitor bank according to claim 1, wherein the capacitor bank comprises one electric double layer capacitor or two or more electric double layer capacitors connected in series or in parallel.
The resistance welding machine as described.