JP2542552B2 - Engine driven arc welder for TIG and hand welding with overload 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 welder that obtains constant current characteristics by switching control, and more specifically, TIG with an overload limiting device that limits welding output characteristics according to welding conditions, manual welding. A dual-purpose engine-driven arc welder.

[0002]

2. Description of the Related Art Conventionally, an engine-driven arc welding machine used for construction work outdoors has mainly been a hand welding. However, in recent years, many building materials such as aluminum and stainless steel are used in building construction, and aluminum and stainless steel are often welded outdoors. Therefore, even an engine-driven arc welder for outdoor use can weld aluminum, stainless steel, etc. in addition to conventional manual welding.
There is a growing demand for welding machines with a power source for IG welding.

As a welding power generator for performing TIG welding, the output of a power generator having a drooping characteristic can be used as a constant current characteristic by a control device, but the control device is expensive and is generally used. In the case of TIG welding, a generator with a constant voltage characteristic is designed, and as shown in FIG.
A chopper circuit 33 for obtaining constant current characteristics enabling IG welding is configured. Generator 22 connected to engine 21
Output is rectified by the rectifier 23, and the smoothing capacitor 24 serves as a power source with a low impedance even when the transistor operates at high speed. The switching transistor 25 performs on / off operation at high frequency and with a large current, and the reactor 27 generates a current. Is suppressed, the output switched by the switching transistor 25 is smoothed, and the welding conditions are stabilized. 28 and 29 are welding terminals, 3
0 is a current detector, 31 is a constant current control unit, and 32 is a transistor drive unit that drives the switching transistor 25.

However, generally, when designing an arc welder using an engine as a drive source, a horsepower margin of about 25% or more relative to the rated output of welding is taken into consideration in consideration of secular changes in engine output variations. Select the engine you have. Similarly, the generator shall be designed so that an output of about 10% or more of the rated output can be obtained. For example, 250 (20 + 0.04 × 250) ＝ 7.5KW, 7.5KW × 135% =
An engine that can output 10KW will be installed in the generator.

[0005]

FIG. 7 shows a power supply characteristic curve in which the horizontal axis represents the arc current I and the vertical axis represents the arc voltage V. In the same figure, the load line Va for manual welding and the load line Vb for TIG welding, which are defined by the JIS standard, are shown by a one-dot chain line and a two-dot chain line, respectively. Hand welding and TIG
The welding load lines Va and Vb show the relationship between arc current and voltage, respectively, Va = 20 + 0.04I, Vb = 14 + 0.02I.
It is represented by. By the way, in the engine-driven arc welding machine as described above, as shown in FIG. 7, the rated value for the manual welding power source (a) point 250 (20 + 0.04 × 250) = 7.5 KW, the rated value for the TIG welding power source ( b) Point 300 (14 + 0.02 x 300) = 6
In order to satisfy the kw welding power source, the engine is supplying the extra output of the hatched part, and the entire machine such as the engine becomes large and heavy, and it becomes an uneconomical machine. Further, in order to obtain the constant current characteristic, the switching element and the main rectifier also had to be selected with sufficient capacity.

Therefore, as a technique for controlling the capacitance of the switching element and the main rectifier, there is a technique disclosed in Japanese Utility Model Publication No. 3-49802. Since the technique of Jitsuhei 3-49802 is a transformer type welding machine that is used by connecting to a commercial power source,
It is not necessary to design the maximum output higher than the rated output, the input voltage is almost constant even if the welding output increases or decreases, and the rectifier does not change depending on the operating conditions such as the engine. It was designed in.

Then, for example, I = 250 A for manual welding,
V = 30V or TIG welding I = 300A, V = 20V
If the arc length increases and the arc voltage rises during welding in, the current exceeding the rating flows in the switching element, so the output of the primary side or secondary side of the transformer is detected and A switching output suppression circuit is provided to prohibit an increase in the output of the switching element when the rated output of TIG welding is exceeded.

However, in an engine-driven arc welder for outdoor construction where a commercial power source is not installed as described above, the engine speed constantly fluctuates depending on the welding load condition, and therefore, according to Japanese Utility Model Publication No. 3-49802. As described above, the welding output cannot be used as the detection means, and an overload limiting circuit has been devised so that the engine and the generator are not overloaded due to individual welding conditions.

Therefore, the present invention configures an overload control circuit that detects the amount of change in the output of the welding generator that exceeds the rated output and suppresses it within the range of several percent of the rated value. It is an object of the present invention to provide an engine-driven arc welder for TIG / hand welding combined with an overload limiting device that solves the problem.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and is a welding generator driven by an engine, and a rectifier and a smoothing capacitor for rectifying and smoothing an AC output power supply of the welding generator. And a switching element for switching the DC output to control the output of current,
In the TIG / manual welding engine-driven arc welder that detects the output current with an output current detector and controls the ON / OFF cycle of the switching element to control the output current with constant current, the smoothing capacitor and the It is provided in the middle of wiring with the switching element, and the welding output becomes too large to cause an overload condition, which detects the DC voltage is lower than a predetermined peak voltage. While controlling the ON / OFF cycle of the switching element by the output current to have a constant current characteristic, by the detection signal from the overload state detecting means,
A constant current characteristic control means for controlling so as to suppress an increase in output of the switching element, and a switching element drive means for driving the switching element according to a control signal from the constant current characteristic control means. It is what

[0011]

According to the above structure, the constant current characteristic control means controls the ON / OFF cycle of the switching element based on the output current detected by the output current detector, and the switching element driving means is controlled by the control signal. , Drive the switching element and control the output current with constant current. Also, when the welding output becomes excessive and becomes overloaded, the engine speed decreases, the DC voltage becomes lower than the predetermined peak voltage,
It is detected by the overload state detecting means. Then, the constant current characteristic control means controls the output increase of the switching element by the detection signal from the overload state detection means, and controls the switching element drive means by the control signal to drive the switching element. , Reduce welding output.

[0012]

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 an electric circuit diagram of an engine-driven arc welder with an overload limiting device. Engine 1
The welding generator 2 is connected to the welding generator 2.
Output is rectified by rectifier 3 and smoothing capacitor 4
The power supply has low impedance even when the transistor operates at high speed. Reference numeral 5 is a switching transistor for performing on / off operation at high frequency and large current, 6 is a reactor for suppressing a sudden increase / decrease in current, smoothing the output switched by the switching transistor 5, and stabilizing welding conditions. It is a freewheeling diode that forms a closed circuit of a reactor, an arc, and a freewheeling diode for maintaining the arc current when the switching transistor 5 is off. Reference numerals 7 and 8 are output terminals, and 9 is a current detector. A variable resistor 11 and a capacitor 1 are provided at a point X provided on the way between the smoothing capacitor 4 and the switching transistor 5.
2, and an overload state detecting unit 14 including a Zener diode 13 is connected, and a constant current characteristic control unit 16 is further connected to the overload state detecting unit 14. The overload state detecting means 14 detects the overload state and transmits a detection signal to the constant current characteristic control section 16 and at the same time, the constant current characteristic control section 16.
It is also a circuit that supplies power to. The current detector 9 is connected to the constant current characteristic control unit 16.

A winding for supplying driving power to the transistor driving section 17 is wound around the stator of the welding generator 2. The transistor drive unit 17 is drive-controlled by a control signal from the constant current characteristic control unit 16 to turn on / off the switching transistor 5.

Since the present invention is constructed as described above,
When the welding work is started using the output terminals 7 and 8, the welding current is detected by the current detector 9, and the constant current characteristic control unit 16 operates to keep the welding current constant at the set current, and the transistor driving unit 17 is operated. Signal to the transistor driver 17
The ON / OFF cycle of the switching transistor 5 is controlled by the signal from the constant current to make a constant current.

Unlike the commercial power source, the engine-driven arc welding machine is connected to a load having a rectifying and smoothing circuit, and when the welding output is small, the generator output voltage waveform is as shown in FIG. It becomes a sine wave as shown in Fig. 4 (a)
As shown in, rectified and smoothed to become direct current. On the other hand, when the welding output is large, the output is limited, unlike the commercial power supply. Therefore, the generator output voltage waveform is close to the peak voltage of the sine wave due to the conduction angle of the rectifier, as shown in Fig. 3 (b). Is flattened, and the rectified and smoothed voltage on the DC side is reduced as shown in FIG. The flat portion of the sine wave shown in FIG. 3B expands in proportion to the increase in output, and the peak voltage decreases.

Further, when the welding output becomes excessive, the engine 1 becomes overloaded, the engine speed decreases, the generated voltage also decreases, and at the same time, the DC voltage also decreases. When a voltage equal to or lower than the voltage set by the variable resistor 11 is supplied to the constant current characteristic control unit 16, the normal ON / OFF signal as shown in FIG. 2 (a) becomes unclear as shown in FIG. 2 (b). The welding output is reduced because the ON time of the switching transistor 5 is shortened as a result of continuous control, and the welding output point moves on the characteristic curve as shown in FIG. In the figure, Va indicates a load line for manual welding, and Vb
Indicates the load line of TIG welding.

Therefore, if the welding output becomes excessive, the vicinity of the peak voltage of the sine wave decreases, and the variable resistor 11
When a voltage equal to or lower than the voltage set in step 2 is supplied to the constant current characteristic control unit 16, the switching transistor 5 discontinuously operates and the ON time of the switching transistor 5 is shortened, so that the welding output can be limited. As a result, the engine 1, the generator 2, the rectifier 3, the smoothing capacitor 4 and the like can be downsized rather than having an excessive capacity. In addition, since the welding output can be limited by discontinuously operating the ON and OFF signals, the engine speed is not excessively reduced and the engine can be rotated in an appropriate state so that the engine capacity can be fully exhibited. It is possible to improve the durability of the engine.

[0018]

As described above, according to the present invention,
The engine, the generator, and the overload limiting device can be downsized, and it is not necessary to use one having an excessive capacity, and the cost can be reduced. Further, it is possible to effectively utilize the horsepower of the engine without reducing the rotation of the engine at the time of overload, and it is possible to improve the durability of the engine. In addition, the constant current characteristic control unit limits the overload under all welding conditions in both manual welding and TIG welding, and can maintain the best arc quality.

[Brief description of drawings]

FIG. 1 is a block diagram showing a TIG / manual welding engine-driven arc welding machine with an overload limiting device according to the present invention.

FIG. 2 is a diagram showing ON / OFF operation of a transistor according to the present invention, (a) is a diagram showing a normal operation of the transistor, and (b) is a diagram showing a discontinuous operation of the transistor.

FIG. 3 is a diagram showing an AC waveform from the generator according to the present invention, FIG. 3A shows an AC waveform when the welding output is small,
(B) shows an AC waveform when the welding output is large.

FIG. 4 is a diagram showing a DC voltage from a smoothing capacitor according to the present invention, (a) shows a DC voltage when the welding output is small, and (b) shows a DC voltage when the welding output is large. ing.

FIG. 5 is a diagram showing characteristic curves of an engine-driven arc welder according to the present invention.

FIG. 6 is a block diagram showing a conventional overload limiting device for an engine-driven arc welder.

FIG. 7 is a diagram showing a characteristic curve of a conventional engine-driven arc welder.

[Brief description of reference numerals]

 1 Engine 2 Generator 3 Rectifier 4 Smoothing Capacitor 5 Switching Transistor 6 Reactor 7, 8 Output Terminal 9 Current Detector 10 Reflux Diode 11 Variable Resistor 12 Capacitor 13 Zener Diode 14 Overload State Detecting Device 16 Constant Current Characteristic Control Unit 17 Transistor Drive Department

Claims (1)

(57) [Claims] 1. A welding generator driven by an engine, a rectifier and a smoothing capacitor for rectifying and smoothing an AC output power source to a DC current, a switching element for switching the DC output to control the current output, and The output current is detected by the output current detector, the on / off cycle of the switching element is controlled, and the output current is controlled to a constant current.
In an engine-driven arc welder for both IG and manual welding, the DC voltage should be lower than the specified peak voltage as it is provided in the middle of the wiring between the smoothing capacitor and the switching element, and the welding output becomes excessive and overloaded. And a constant current characteristic by controlling the ON / OFF cycle of the switching element by the output current detected by the output current detector, and detecting from the overload state detecting means. A constant current characteristic control means for controlling an output increase of the switching element by a signal, and a switching element drive means for driving the switching element by a control signal from the constant current characteristic control means. TI with overload limiting device characterized in that
Engine driven arc welder for both G and hand welding.