JP2003236675A - Welding power source - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a welding power source which has a quick response speed for control and is suitable for joining a fine coated wire. <P>SOLUTION: The welding power source is characterized in that the power source is provided with a power source part which rectifies a commercially available AC voltage, an inverter part which transforms the output of the power source part into an AC voltage which has a frequency higher than the commercially available AC voltage, a welding transformer to which primary side the AC output from the inverter part is inputted and a low AC voltage induced in the secondary side is applied upon a pair of welding electrodes, an electric current detection means which detects the welding current on the secondary side of the welding transformer, a voltage detection means which detects the welding voltage between the pair of welding electrodes, and a feed back circuit which calculates the welding resistance from the welding current and the welding voltage and feeds back the welding resistance to the control circuit of the inverter part. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter type power supply or a transistor type power supply used for joining a fine coated wire to a terminal, and more particularly to a control method thereof.

[0002]

2. Description of the Related Art Conventionally, a pulse heating method has been used for joining finely coated wires to terminals. The pulse heating method includes a heater chip formed in a plate shape with a high resistance material such as molybdenum or titanium, and a thermocouple connected to the tip of the heater chip. The heater chip is heated by the pulse heating method. To be done. The pulse heating method is a method in which a large pulse current is passed and the Joule heat generated at this time is used for heating.

The fine coated wire has a diameter of several tens of μm to 1 mm, and the surface of the core wire is coated with an insulating film such as urethane resin. In order to bond such a fine coated wire to the terminal, solder is applied to the terminal in advance, and the fine coated wire to be bonded is placed thereon. After that, the tip of the heater chip is brought into contact with the finely coated wire to apply a large pulse current 10
When flowing at an interval of 0 ms to several 100 ms, the heater chip is heated by Joule heat, melts the insulating film and the solder, and joins the core wire of the fine coated wire to the terminal.

FIG. 3 is a block diagram of such a pulse heat power supply. In FIG. 3, 41 is a triac,
42 is a transformer for converting the output of the triac 41 into low voltage and large current and supplying it to the heater chip 43;
Is a thermocouple attached to the tip of the heater chip 43, 4
5 is a differential amplifier for amplifying the thermoelectromotive force obtained by the thermocouple 44, 46 is a temperature setting switch for setting the temperature of the heater chip 44, 47 is the difference between the output voltage of the amplifier 45 and the output voltage of the switch 46. Is a phase control circuit for controlling the current flowing through the heater chip 43 by turning on / off the triac 41, 51 is a terminal, 52 is a solder, and 53 is a fine coated wire.

Next, the operation of such a pulse heat power supply will be described. First, the phase control circuit 48 starts to operate, the triac 41 is turned on, and the AC voltage (AC100V) from the single-phase commercial AC power supply (not shown) is applied to the transformer 4.
2 is applied to the heater chip 43, and a current starts flowing through the heater chip 43.
As a result, the temperature of the heater chip 43 rises, and the temperature of the heater chip 43 is converted into a voltage by the thermocouple 44.

Next, the adder circuit 47 outputs the difference between the output voltage of the amplifier 45 which amplifies the thermoelectromotive force of the thermocouple 44 and the voltage from the switch 46 corresponding to the set temperature. Then, the phase control circuit 48 controls the triac 41 based on the output of the adding circuit 47 so that the temperature of the heater chip 43 becomes the set temperature.

As described above, since the temperature of the heater chip 43 is controlled by feeding back the thermoelectromotive force from the thermocouple 44, the response of the thermoelectromotive force of the thermocouple is delayed. Thermocouples also have a life. Further, since the single-phase commercial AC power supply is used as the primary power supply of the transformer, the time resolution is rough (10 ms at 50 Hz, 8.33 ms at 60 Hz).

[0008]

As described above, the conventional pulse heat power source is the feedback control of the thermoelectromotive force by the thermocouple, and the temperature of the heater chip is controlled by the phase control of the commercial frequency. There is a drawback in that unnecessary heat is applied to the vicinity of the joint portion of the heater chip due to the response delay and the coarseness of time resolution. The present invention has been made to solve the above problems, and an object of the present invention is to provide a welding power source having a high control response speed and a high time resolution.

[0009]

The present invention has been made focusing on the fact that the resistance value is a function of temperature. That is, the resistance value can be expressed by the following equation. R = ρ × {1 + α × (T−T25)} × (L / A) where ρ is the resistivity of the material forming the resistor. α is the temperature coefficient of the material forming the resistor, T25 is the reference temperature (here, 25 degrees Celsius), L is the length of the resistor, and A is the cross-sectional area of the resistor. From this equation, if the resistance value can be measured, the temperature can be calculated, and the welding current can be controlled using the resistance value itself as a control parameter.

A first welding power source according to the present invention includes a power source section for rectifying a commercial AC voltage, an inverter section for converting an output of the power source section into an AC voltage having a frequency higher than the commercial AC voltage, and this inverter. AC output of the welding part is input to the primary side, a welding transformer for applying an AC low voltage induced on the secondary side to the pair of welding electrodes, and a current detecting means for detecting the welding current on the secondary side of the welding transformer. And a voltage detection means for detecting a welding voltage between the pair of welding electrodes, and a feedback circuit for calculating a welding resistance from these welding current and welding voltage and feeding back the welding resistance to the control circuit of the inverter section. It is characterized by that.

A second welding power source according to the present invention comprises a power source section for stepping down commercial AC voltage, rectifying it, and charging it with the voltage.
Between the pair of welding electrodes, an energization controller that limits the output of the power source to a fixed time width to energize the welding current to the pair of welding electrodes, a current detection unit that detects the welding current from the energization controller, And a feedback circuit for calculating a welding resistance from the welding current and the welding voltage and feeding back the welding resistance to the control circuit of the energization control unit. is there.

[0012]

According to the present invention, the resistance which is a function of temperature is calculated instead of the thermocouple and the welding current is controlled based on the result, so that the response delay is small. Moreover, since the inverter type welding power source or the transistor type welding power source capable of controlling the welding current by continuous wave is used, welding control with high time resolution can be performed.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below with reference to the drawings.

Embodiment 1 FIG. 1 is a block diagram of a main part of an inverter type welding power source which is a welding power source showing an embodiment of the present invention. In FIG. 1, 1 is a rectifying / smoothing unit that rectifies and smoothes an AC 200 V three-phase AC power source, which is a power source unit, and 2 is a DC power source from the rectifying / smoothing unit 1, which is controlled by a PWM control unit 10 described later to
An inverter section 3 for converting into an AC power source having a higher frequency than the three-phase AC power source of C200V, a welding transformer 3 for receiving an AC voltage from the inverter section 2 to obtain an AC output voltage of a large current at a low voltage, 4 a welding transformer 3 Rectifying part for rectifying the AC voltage power supply of 5 is a welding current detecting element which is a current detecting means, 6a and 6b are welding electrodes, 7 is a welding current obtained by the welding current detecting element 5 and the welding electrodes 6a and 6b. An amplification division unit that receives a voltage detected by the voltage detection means 12 provided, performs a predetermined amplification, and divides the amplified voltage by a current to calculate welding resistance, and 9 is a resistance change profile as a welding condition. The welding condition setting unit 10 that receives the set resistance profile from the welding condition setting unit 9 and the resistance value from the amplification division unit 7 are set so that the resistance value matches the set resistance profile. A PWM control unit for generating a drive signal of the inverter 2. Although not shown, the welding electrode 6
The fine coated wire and the terminal to which the fine coated wire is welded are sandwiched between a and 6b.

Next, the operation of such an inverter type welding power source will be described. A commercial three-phase AC200V power source is input to the rectifying / smoothing unit 1, rectified and smoothed, and input to the inverter unit 2. The inverter unit is composed of four transistors, and has an inverter drive signal S of a predetermined frequency sufficiently higher than the commercial AC frequency from the PWM control unit 10.
By 1 and S2, the four transistors are divided into two sets of transistors and alternately turned on / off to output a high-frequency AC rectangular wave.

The high frequency AC rectangular wave output from the inverter unit 2 is supplied to the primary coil of the transformer 3.
A low voltage, high current rectangular wave is generated in the secondary coil. The low-voltage, large-current rectangular wave generated in the secondary coil is converted into direct current by the rectifying unit 4 composed of a pair of diodes, and a welding current corresponding to the rectangular current flows into the welding electrodes 6a, 6b, and the object to be welded. Generates resistance heat. Due to this resistance heat generation, the fine coated wire which is the object to be welded is welded to the terminal.

Next, the generation of the inverter drive signals S1 and S2 of the PWM control section 10 will be described. A detection element 5 is provided for detecting the welding current, and the welding current I detected by the detection element 5 is input to one of the amplification division units 7. Further, a voltage drop occurs between the welding electrodes 6a and 6b according to the resistance value of the object to be welded. This voltage drop V is similarly input to the other side of the amplification division unit 7. In the amplification division unit 7, the welding current I and the drop voltage V are amplified and divided to obtain the welding resistance R.

The PWM control section 10 uses a commercially available PWM IC to generate a ramp signal having a frequency determined by an external timing resistor, and outputs from the set resistance profile of the welding condition setting section 9 and the amplification division section 7. Inverter drive signals S1 and S2 are generated so that the welding resistance R of 1 is matched.

In this way, welding according to the set temperature profile of the welding condition setting section 9 is possible, so that it is possible to appropriately weld the fine coated wire to the terminal without using a thermocouple to monitor the temperature. it can. Further, since the inverter is used, the control can be performed at a frequency higher than the frequency of the commercial power source, so that the control with high time resolution can be performed.

Embodiment 2 FIG. 2 is a block diagram of a main part of a transistor type welding power source which is a welding power source showing another embodiment of the present invention. In FIG. 2, reference numerals 21, 22, 23 denote power supply units,
Reference numeral 21 is a transformer that steps down a commercial single-phase AC 100V AC voltage to a predetermined AC voltage, 22 is a rectifying unit that rectifies the AC voltage from the transformer 21, 23 is a capacitor that is charged with the rectified voltage from the rectifying unit 22, and 24 is A charging control unit for controlling the charging voltage to the capacitor 23, 25 is a welding head, 2
Reference numeral 6 is a transistor which is an energization control unit for supplying a welding current to the welding head 25 under the control of a gate control unit 29 which will be described later, 30 is a current detection element which is current detection means, 31 is voltage detection means, and 27 is welding. An amplification division unit that amplifies the current and the welding voltage by a predetermined amount and divides the amplified voltage by the current to calculate the welding resistance, 28 is a welding condition setting unit that sets a resistance profile that is a welding condition, and 29 is amplification division The gate control unit receives the welding resistance of the section 27 and the resistance profile of the welding condition setting section 28 and determines the gate voltage width of the transistor 26 so that the welding resistance matches the set resistance profile. Although not shown, the welding head 25
A fine coated wire and a terminal to which the fine coated wire is welded are sandwiched between them.

Next, the operation of such a transistor-type welding power source will be described. Commercial AC voltage AC100
V is stepped down to an appropriate voltage by the transformer 21, and full-wave rectified by the rectifying unit (bridge) 22 to charge the capacitor 23.
Here, the charging voltage of the capacitor 23 is a switching element (thyristor) 22 which is a part of the rectifying element of the rectifying unit 22.
The charging control unit 24 controls the ignition phases of a and 22a. In this way, the capacitor 23 is always charged with the predetermined charging voltage.

The current led from the capacitor 23 to the welding head 25 is current controlled by the transistor 26. That is, the welding current and the welding voltage are input to the amplification division unit 27, where the welding resistance is obtained and the gate control circuit 2
It is fed back to 9. The gate control circuit 29 determines the gate voltage of the transistor 26 according to the resistance profile set by the welding condition setting unit 28,
Control 6 In this way, the welding current flows through the welding head 25, and resistance heat is generated in the workpiece. Due to this resistance heat generation, the fine coated wire which is the object to be welded is welded to the terminal.

In this way, welding can be performed in accordance with the temperature profile set by the welding condition setting section 9. Therefore, it is possible to properly weld the fine coated wire to the terminal without monitoring the temperature using a thermocouple. it can. Further, since the welding current is continuously supplied for a fixed time width, control with high time resolution becomes possible.

[0024]

According to the present invention, as described above,
Transistor that can control the welding current by calculating resistance as a function of temperature instead of thermocouple and controlling the welding current based on the result, and can control the welding current by inverter type welding power source or continuous wave. Since a welding power source of the type is used, it is possible to perform welding control with high time resolution, and therefore it is possible to provide a highly reliable welding power source that does not add extra heat to the welded portion.

[Brief description of drawings]

FIG. 1 is a block diagram of a main part of an inverter-type welding power source that is a welding power source according to an embodiment of the present invention.

FIG. 2 is a block diagram of a main part of a transistor-type power source that is a welding power source according to another embodiment of the present invention.

FIG. 3 is a block diagram of a pulse heat power source which is a welding power source used for welding a conventional fine coated wire.

[Explanation of symbols]

1 Rectifying and smoothing section 2 Inverter section 3 welding transformer 4 Rectifier 5 Current detection element 6a, 6b Welding electrode 7 amplification division 9 Welding condition setting section 10 PWM control unit 12 Voltage detection means

Claims (2)

[Claims] 1. A power supply section for rectifying a commercial AC voltage, an inverter section for converting an output of the power supply section into an AC voltage having a frequency higher than the commercial AC voltage, and an AC output of the inverter section is input to a primary side. And a welding transformer for applying an AC low voltage induced on the secondary side to the pair of welding electrodes, a current detecting means for detecting a welding current on the secondary side of the welding transformer, and a welding electrode between the pair of welding electrodes. Welding resistance is calculated from the voltage detection means that detects the welding voltage and these welding current and welding voltage.
A welding power source having a feedback circuit for feeding back the welding resistance to the control circuit of the inverter section. 2. A power supply unit for stepping down and rectifying commercial AC voltage, and charging with the voltage, and an energization control unit for restricting the output of the power supply unit to a constant time width and supplying a welding current to a pair of welding electrodes. A current detecting means for detecting a welding current from the energization control section, a voltage detecting means for detecting a welding voltage between the pair of welding electrodes, and a welding resistance calculated from these welding current and welding voltage,
A welding power source having a feedback circuit for feeding back the welding resistance to the control circuit of the energization control unit.