JP2567726Y2 - Engine driven arc welding machine with load limiting device - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine-driven arc welding machine with a load limiting device that obtains a constant current characteristic by switching control and limits a welding output characteristic according to welding conditions.

[0002]

2. Description of the Related Art Conventionally, manual welding of an engine-driven arc welding machine used for construction work in the field is mainly performed. However, in recent years, building materials such as aluminum and stainless steel are often used in building construction, and aluminum, stainless steel and the like are often welded outdoors. Therefore, even in the case of an engine driven arc welding machine for outdoor use, in addition to the conventional manual welding, T, which can weld aluminum, stainless steel, etc., can be used.
There is an increasing demand for welding machines equipped with a power source for IG welding.

[0003] As a welding generator for performing TIG welding, the output of a generator having a drooping characteristic can be used as a constant current characteristic by a control device. However, since the control device is expensive, it is generally used. In the case of performing TIG welding, a generator having a constant current characteristic is designed, and the welding control circuit is constituted by a chopper circuit 30 for obtaining a constant current characteristic enabling TIG welding as shown in FIG. I do. Engine 21
The output from the generator 22 connected to the rectifier 23 is rectified by the rectifier 23, and the smoothing capacitor 24 is used as a power source with a small impedance even when the transistor is operated at high speed. The current is applied, and the reactor 26 suppresses a rapid increase and decrease of the current, smoothes the output switched by the switching transistor 25, and stabilizes the welding conditions. The fluctuation of the welding current is detected by a current detector 27 and input to a transistor driving unit 29 via a constant current control unit 28 to control the welding current.

However, in general, when designing an arc welder using an engine as a drive source, a margin of horsepower of about 25% or more with respect to the rated output of welding is taken into consideration in consideration of the secular variation of engine output and the like. Choose the engine you have. Similarly, the generator is designed so that an output of about 10% or more of the rated output can be obtained. For example, in order to provide an engine generator rated 250 A in total, 250 (20 + 0.04 × 250) = 7.5 kW, 7.5 kW × 135% =
The engine that can output 10KW will be assembled to the generator.

[0005]

[Problems to be Solved by the Invention] In an engine driven type welding machine, in order to satisfy the output as a manual welding power source, the entire machine such as an engine becomes large and heavy, resulting in an uneconomical machine. Was. Further, in order to obtain a constant current characteristic, the switching element and the main rectifier have to select a sufficient capacity. As a method for preventing an increase in the size of a machine, there is a technique described in Japanese Utility Model Publication No. 3-49802 as a technique for controlling the capacity of a switching element and a main rectifier. Since this invention is a transformer type welding machine that is used by connecting to a commercial power supply, it is not necessary to design the maximum output to be higher than the rated output, and the input voltage is almost constant even if the welding output increases or decreases. Also, it is designed under almost constant conditions without being changed by the use condition like the engine.

Then, for example, I = 250A by hand welding,
V = 30V or I = 300A for TIG welding, V = 20V
If the arc length increases and the arc voltage rises when welding is performed, the current exceeding the rating flows through the switching element, so the output of the primary or secondary side of the transformer is detected, and manual welding and When the output exceeds the rated output of TIG welding, a switching output suppression circuit is provided to inhibit the output of the switching element from increasing.

However, in the case of an engine-driven arc welding machine for outdoor construction where no commercial power supply is installed as described above, when the above-described device disclosed in Japanese Utility Model Publication No. 3-49802 is used, Since the output current is always controlled to the current value that has been set once, the engine output has to be reduced due to changes in weather conditions, aging, etc., and variations in engine output. The balance between the welding output and the engine output is lost, the engine speed drops extremely, and the welding output becomes unstable, causing welding defects, engine changes due to engine overload, and large amounts of black smoke. Generation and, furthermore, a decrease in the cooling efficiency of the welding generator, leading to a shortened life.

Therefore, the present invention detects the frequency of the welding generator by utilizing the characteristic that the engine speed decreases as the output of the welding generator increases. When the frequency falls below the set frequency, the output voltage of the welding generator is controlled to a lower voltage by an automatic voltage regulator circuit (hereinafter abbreviated as AVR circuit) having a preset frequency-control voltage characteristic (FV characteristic) function. Thus, when the voltage becomes equal to or lower than a predetermined voltage, an increase in the output of the switching element is suppressed, and a load control circuit that suppresses the output within the rated output is configured. It is intended to provide a welding machine.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and has a welding generator driven by an engine and an automatic voltage regulator for keeping the output voltage of the welding generator constant. A circuit, a rectifier and a smoothing capacitor for rectifying and smoothing the output power to DC, a switching element for switching the DC output to control the output, and an output current detector for detecting the output controlled output current. A constant current control means for controlling the ON / OFF cycle of the switching element detected by the output current detector and controlling the output current of the welding terminal; In the above, the frequency of the output voltage of the welding generator is detected, and the control voltage of the automatic voltage adjustment circuit is set in advance for a frequency equal to or lower than a preset frequency. An FV characteristic control unit that changes with the changed amount, and a constant current characteristic control unit that suppresses and controls an increase in the output of the switching element when the control voltage of the automatic voltage adjustment circuit is lower than a preset voltage. A transistor driving means for driving the switching element according to a control signal from the constant current characteristic control means,
An increase in the output of the switching element is suppressed based on the set voltage controlled by the FV characteristic control means, and the overload of the engine is controlled to maintain the engine speed in an appropriate state.

[0010]

According to the engine driven arc welding machine of the present invention, when the frequency of the welding generator does not decrease, the output voltage is maintained at a constant voltage by the automatic voltage adjusting circuit. Based on the detected output current, the constant current characteristic control means controls the ON / OFF cycle of the switching element, controls the transistor driving means by the control signal to drive the switching element,
Output current is controlled by constant current. When the welding output increases, the engine speed decreases accordingly. When the frequency of the welding generator fluctuates, for example, to a value at which the FV characteristic control means in the automatic voltage regulating circuit operates, the control voltage automatically drops, and the output voltage of the welding generator also drops. I will do it. This reduced output voltage is detected, and when the output voltage falls below a preset voltage (overload state), a signal from the voltage detection means is converted into an arbitrarily set output suppression signal so as to suppress the welding output, and A signal is sent to the constant current characteristic control means, and the constant current characteristic control means controls the output of the switching element to be suppressed, controls the transistor driving means by the control signal, drives the switching element, and controls the welding output. Can be reduced.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment according to the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of an engine driven arc welding machine with a load limiting device of the present invention,
FIG. 2 is a characteristic curve of the engine showing the relationship between the output and the number of revolutions of the engine driven arc welding machine with the load limiting device of the present invention, FIG. 3 is a wiring block diagram of the conventional engine driven arc welding machine, and FIG. FIG. 5 is a diagram illustrating an FV characteristic curve of the voltage adjustment circuit.

A welding generator 2 is connected to the engine 1, and the output of the welding generator 2 is controlled to be constant by an automatic voltage regulating circuit 13. The output of the welding generator 2 is supplied to a rectifier 3. Rectified to DC and smoothed capacitor 4
In this case, a power source with low impedance is used even when the transistor operates at high speed. Reference numeral 5 denotes a switching transistor that performs on / off operations at a high frequency and with a large current. Reference numeral 6 denotes a reactor that suppresses a sudden increase and decrease in current, smoothes an output switched by the switching transistor 5, and stabilizes welding conditions. A reactor for maintaining an arc current between the output terminals 7 and 8 when the switching transistor 5 is off, an arc, and a freewheeling diode that forms a closed circuit of a freewheeling diode. 9 is a current detector.

An FV for reducing the output voltage of the generator 2 when the frequency of the generator 2 is reduced below a certain frequency.
An automatic voltage regulating circuit 13 having a function of a characteristic control means is connected to the generator 2 for welding. Further, a voltage drop detecting unit 12 is connected to a DC voltage unit that rectifies the output from the welding generator 2, and the detecting unit 12 converts the signal into an output suppression signal arbitrarily set according to the voltage drop. To the constant current characteristic control unit 11. The current detector 9 is also connected to the constant current characteristic control unit 11.

A winding for supplying drive power to the transistor drive unit 14 is wound around the stator of the welding generator 2. The driving of the transistor driving unit 14 is controlled by a control signal from the constant current characteristic control unit 11 to turn on and off the switching transistor 5.

Since the engine-driven arc welding machine of the present invention is constructed as described above, when a voltage is applied between the output terminals 7 and 8 to start a welding operation, the welding current is detected by the current detector 9. The constant current characteristic control unit 11 operates to detect the detected current and keep it constant at the set current.
14 to send a signal, ON of the switching transistor 5 by a signal from the transistor driving unit 14, by controlling the OFF period, and a constant current.

The output of the engine of the engine-driven arc welding machine of the present invention has characteristics as shown in FIG. When the load is applied to the engine 1 from the no-load rotation speed (a), the engine rotation speed decreases as the load increases, passes through the rated load rotation speed (b), and reaches the maximum output rotation speed (c). You. Further, the welding is continued to apply a load,
When the overload state is set, the engine speed decreases and the engine output decreases from the point of the maximum output speed (c). By utilizing this characteristic, the output voltage of the generator was reduced by the FV characteristic control means due to the decrease in the frequency of the welding generator directly connected to the engine, and the voltage was detected, whereby the setting was made arbitrarily. By converting the signal into an output suppression signal and providing the signal to the constant current characteristic control unit 11, the welding output point moves.

As a result, the engine 1, the welding generator 2, the rectifier 3, the smoothing capacitor 4 and the like can be reduced in size without having excessive capacity. In addition, since the welding output can be limited, the engine can be rotated in an appropriate state without excessively lowering the engine speed, so that the engine performance can be fully exhibited and the engine durability can be improved. Can be.

[0018]

[Effects of the Invention] As described above, according to the present invention,
In an engine-driven arc welding machine, overload of the engine can be controlled, and the engine speed can be maintained in an appropriate state. In addition, the constant current characteristic control unit limits the load under all welding conditions in both manual welding and TIG welding, so that the best arc quality can be maintained. Power can be effectively utilized, and the durability of the engine can be improved.

Furthermore, a slowdown function for lowering the engine speed when welding is not performed is employed in an engine-driven arc welding machine. However, if a current regulator is set to the maximum output, the slowdown function is used. When the welding work is started, the constant current characteristic control unit will try to output the maximum current instantaneously, but the engine speed is still high and the engine output is insufficient, so the engine speed is high. And the engine stalls, but this problem also suppresses the welding output when the engine speed decreases, so the engine speed does not depend on the output value from the current regulator. Even when welding is started in a low state, the rotation of the engine can be shifted to high speed without imposing a burden on the engine.

[Brief description of the drawings]

1 is a block diagram of one embodiment illustrating the load limiting device with an engine driven arc welder of this invention.

FIG. 2 is a characteristic curve of an engine showing the relationship between the output and the rotation speed of the arc welding machine of the present invention.

FIG. 3 is a wiring block diagram of a conventional engine-driven arc welding machine.

4 is a diagram showing an FV characteristic curve of the automatic voltage regulator circuit of the invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Engine 2 Welding generator 3 Rectifier 4 Smoothing capacitor 5 Switching transistor 6 Reactor 7, 8 Output terminal 9 Current detector 10 Reflux diode 11 Constant current characteristic control unit 12 Voltage drop detection unit 13 Automatic voltage adjustment circuit 14 Transistor drive unit

Claims (1)

(57) [Scope of request for utility model registration] 1. A welding generator driven by an engine, an automatic voltage adjusting circuit for keeping the output voltage of the welding generator constant, a rectifier and a smoothing capacitor for rectifying and smoothing the output power to DC. A switching element for switching the DC output to control the current output; an output current detector for detecting the output controlled output current; and an on / off cycle of the switching element detected by the output current detector. A constant current control means for controlling and controlling the output current of the welding terminal, wherein the engine-driven arc welding machine outputs welding by a constant current, wherein the frequency of the output voltage of the welding generator is detected and set in advance. FV at which the control voltage of the automatic voltage adjustment circuit changes by a preset amount for a frequency equal to or lower than the
A characteristic control unit; a constant current characteristic control unit configured to suppress and control an increase in output of the switching element when a control voltage of the automatic voltage adjustment circuit is lower than a preset voltage; A transistor driving means for driving the switching element according to a control signal; suppressing an increase in output of the switching element based on a set voltage controlled by the FV characteristic control means, controlling an overload of the engine, An engine-driven arc welding machine with a load limiting device, which maintains the rotational speed in an appropriate state.