JP2758572B2 - Engine driven arc welding machine - 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 having an external output characteristic having a constant current characteristic.

[0002]

2. Description of the Related Art Conventionally, manual welding is the mainstream of engine-driven arc welding machines used for construction work outdoors. Therefore, as shown in FIG. 11, a chopper circuit for obtaining a general constant current characteristic by applying a power source having a constant current characteristic with high arc stability to an engine driven arc welding machine for the field is constituted. .

In this engine driven arc welding machine, an output from a generator 32 connected to an engine 31 is supplied to a rectifier 33.
Is rectified. The rectified output is smoothed by a smoothing capacitor 34 provided. The rectified output that has passed through the smoothing capacitor 34 is output by the high frequency on / off operation of the switching element 35, smoothed by the reactor 36, and welded terminals 37 and 38.
Supply welding current in between. The detected current value of the current detector 39 is given to the constant current control unit 40, and the switching element 35 is driven by the output of the constant current control unit 40 via the switching element driving unit 41. Reference numeral 42 denotes a reflux diode for maintaining an arc.

However, in such a welding machine having a constant current characteristic, when a high cellulosic-coated welding rod requiring a large short-circuit current is used, there is a problem that welding is likely to occur and welding defects occur.

As a method for increasing the current at the time of a short circuit, a device described in Japanese Utility Model Publication No. 4-35007 has been proposed. However, in this invention, in the current control circuit using the thyristor, the detection level of the arc current detection circuit is adjusted by the current setting circuit, and the reference value is adjusted by the ignition circuit via the output characteristic switching circuit. The phase control is performed in comparison with. This is to sharply increase the current when a short circuit occurs.

When a constant current output characteristic with high arc stability is adopted for an engine driven arc welding machine, the voltage drop of a welding cable near the maximum current output setting may be large depending on the operator's choice, or the welding of a sheath may be difficult. Since the welding output voltage rises when the type of rod and arc length are increased, a generator, semiconductor, and high-power engine with a capacity capable of outputting all the output of the maximum output curve in the constant current output characteristic are used. There is a technique described in Japanese Utility Model Publication No. 3-49802 as a technique that does not output a shaded portion which is an overload region in FIG. Since this technology is a welding machine that is used by connecting to a commercial power supply, load characteristics can be constantly generated, the power supply is stable, and it is designed on the assumption that the conditions are almost constant.

However, when the above technique is applied to an engine-driven arc welding machine used outdoors where no commercial power source is installed, the output characteristics are always designed to be constant, causing a problem. That is, use environment conditions,
If the engine output is insufficient due to a decrease in engine output due to aging, etc., or an engine with insufficient output is used, the required welding output will exceed the engine output, and the engine speed will drop extremely. The output becomes unstable, causing welding defects, engine deterioration due to engine overload, generation of a large amount of black smoke, and shortening of the life of the welding generator due to deterioration in cooling efficiency.

The present invention has been made in view of the above points, and in an engine driven arc welding machine having a constant current characteristic, when the welding output becomes overloaded due to welding work conditions, the welding output is reduced. It is an object of the present invention to provide an engine-driven arc welding machine that restricts and prevents overload.

Another object of the present invention is to provide an engine-driven arc welding machine capable of securing a voltage sufficient for generating an arc at the time of slowdown and starting an arc from the slowdown.

[0010]

In order to achieve the above object, the present invention provides a welding generator driven by an engine to form an AC output, and an AC output voltage of the welding generator. An automatic voltage adjustment circuit that adjusts to a constant value, a rectifier circuit that converts an AC output of the welding generator into a DC, a switching circuit that performs switching control of a DC output from the rectifier circuit and outputs the DC to a welding terminal, An engine comprising: a welding current detector for detecting an output current of a circuit; and a constant current control circuit for controlling the switching circuit in accordance with the detection current of the welding current detector and for constantly controlling the output current at the welding terminal. In the driving arc welding machine, a frequency detection circuit for detecting a frequency of an AC output of the welding generator, and a detection frequency of the frequency detection circuit is equal to or less than a set value. A constant value, and a frequency-voltage characteristic circuit for controlling the welding generator so as to output a voltage having a value proportional to the frequency when the value is equal to or less than the set value, and detecting an output voltage of the welding generator. A voltage detection circuit, and compares the detection voltage of the voltage detection circuit with a preset reference voltage, and when the detection voltage is lower than the reference voltage, gives a signal for suppressing the welding output to the constant current control circuit. An output suppression circuit that performs switching control of the switching circuit, and the constant current control circuit is configured to perform pulse width modulation in order to suppress and control the length of an ON period in the switching circuit. An engine-driven arc welder, and a welding generator driven by an engine to form an AC output according to claim 2, and the welding. An automatic voltage adjustment circuit for adjusting the AC output voltage of the generator to a constant value, a rectifier circuit for converting the AC output of the welding generator to DC, and a switching control of the DC output from the rectifier circuit to output to the welding terminal. Switching circuit, a welding current detector for detecting an output current of the switching circuit, and a constant current for controlling the switching circuit in accordance with the detection current of the welding current detector and for controlling the output current at the welding terminal constant. In an engine-driven arc welding machine having a control circuit, a frequency detection circuit for detecting a frequency of an AC output of the welding generator, and a constant value when the detection frequency of the frequency detection circuit is equal to or higher than a set value. A frequency-voltage characteristic circuit for controlling the welding generator so as to output a voltage having a value proportional to the frequency when the value is less than or equal to the frequency; A voltage detection circuit for detecting the output voltage of the device, and comparing the detection voltage of the voltage detection circuit with a preset reference voltage,
When the detection voltage is lower than the reference voltage, the constant voltage control circuit is provided with a signal for suppressing a welding output, and an output suppression circuit that performs switching control of the switching circuit. It has a frequency-voltage characteristic of a gentle slope below a predetermined frequency lower than the frequency, a stronger slope at a frequency higher than the predetermined frequency, and is configured to control the welding generator. And an engine driven arc welding machine.

[0011]

According to the structure of the first aspect, the frequency of the AC output of the generator is detected by the frequency detection circuit, and when the detected frequency is higher than the set value, the frequency is constant and when the detected frequency is lower than the set value, it is proportional to the frequency. The output voltage of the welding generator is controlled by the automatic voltage adjustment circuit so that the output voltage corresponds to the frequency so that the output voltage has the set value. Due to this action, the output frequency of the welding generator corresponds to the engine speed, so that if the engine is overloaded during welding work, the engine speed decreases. At this time, if a voltage detection circuit different from the frequency detection circuit detects the output voltage of the welding generator and gives the detected voltage to the output suppression circuit, the output suppression circuit compares the reference voltage with the reference voltage to prevent overload. The welding output required for Then, the length of the ON period of the switching circuit is suppressed by pulse width modulation, and as a result, the welding output is suppressed.

According to the second aspect of the present invention, the automatic voltage regulating circuit has a frequency-voltage characteristic having a gentle slope below a predetermined frequency lower than a set frequency and a stronger slope above a predetermined frequency. Control the output voltage of the machine. As a result, it is possible to secure a voltage sufficient for arc generation at the time of slowdown and to perform arc start from the slowdown.

[0013]

[0014]

According to the first aspect of the present invention, since the output frequency of the welding generator corresponds to the engine speed, the engine speed decreases when an overload occurs during welding work. It decreases in proportion to that. Therefore, the output voltage of the welding generator is detected and applied to the output suppression circuit to suppress the welding output necessary to prevent overload, thereby preventing the engine and the welding generator from being overloaded. And
The length of the ON period of the switching circuit is suppressed by pulse width modulation, and as a result, the welding output is suppressed.

According to the second aspect of the present invention, the automatic voltage adjustment circuit has a frequency-voltage characteristic having a gentle slope below a predetermined frequency lower than a set frequency and a stronger slope above a predetermined frequency. The output of the generator is controlled. As a result, it is possible to secure a voltage sufficient to generate an arc at the time of slowdown and to perform an arc start of the engine speed from the slowdown.

[0016]

[0017]

FIG. 1 is a block diagram showing an embodiment of the present invention, which is configured as an engine driven arc welding machine with a load limiting function. FIG. 2 is an engine output-revolution speed curve showing the relationship between the engine output and the engine speed, and FIG. 3 is an FV characteristic curve of the automatic voltage adjustment circuit.
FIG. 4 is a welding output characteristic diagram according to the present invention (shaded portions are cut as overload regions), and FIG. 5 shows ON / OFF operations of the switching elements.

A welding generator 2 is connected to the engine 1, and the power supply voltage of the welding generator 2 is regulated by an automatic voltage regulating circuit 14. Is rectified to DC, smoothed by the capacitor 4 and then supplied to the switching element 5. The output of the switching element 5 is supplied from output terminals 7 and 8 via a reactor 6. 9 is a reflux diode for maintaining the arc, and 10 is a welding current detector.

The automatic voltage regulating circuit 14 connected to the welding generator 2 is provided with a frequency for reducing the power supply voltage of the generator when the frequency of the AC power supply of the welding generator 2 falls below a certain frequency. It has a voltage (FV) characteristic. A voltage detector 17 is connected to an output of the rectifier 3 for rectifying the AC power of the welding generator 2, and the detector 17 sends a detected voltage to an output suppressor 18. When the detected voltage falls below a certain set voltage, the output control unit 18 sends an output suppression signal proportional to the voltage drop to the constant current characteristic control unit 15. At this time, the voltage detector 17 may detect the AC output voltage of the generator 2 for welding. Further, the welding current detector 10 is also connected to the constant current characteristic control unit 15.

Although not shown, a winding for supplying drive power to the switching element drive unit 16 is wound around the stator of the welding generator 2. The switching element driving section 16 is controlled by a control signal from the constant current characteristic control section 15 to turn on and off the switching element 5.

In the engine-driven arc welding machine shown in FIG. 1, when a welding cable is connected between the welding output terminals 7 and 8 to start a welding operation, a welding current detector 10 detects the welding current and controls the constant current characteristics. The switching element driving section 16 is controlled so that the current set by the section 15 is always constant, the ON period of the switching element 5 is adjusted, and the output current is constant.

The relationship between the engine output and the engine speed has a characteristic (governor characteristic) as shown in FIG.
Now, it is assumed that the engine is operating with no load, and the rotation speed is the no-load rotation speed (a). When a load is applied to the engine 1, the engine governor tries to maintain the rotation speed with the increase in the load, but the engine rotation speed decreases due to the characteristic, and the maximum output power passes through the rated output rotation speed (b). The number of revolutions drops to (c). When the load is further applied to cause an overload state, the engine speed decreases from the point (c), and the engine output also decreases.

Utilizing this characteristic, when the welding output is overloaded, the engine speed decreases, the frequency of the AC power supply voltage of the welding generator directly connected to the engine also decreases, and a preset value is set. When the frequency falls below the predetermined frequency, the power supply voltage of the welding generator is reduced due to the FV characteristic in the automatic voltage adjustment circuit 14. The voltage is detected by the voltage detector 17 and the detected voltage is sent to the output suppressor 18. Then, when the detected voltage is lower than the voltage set in advance in the output suppression unit 18, an output suppression signal is given to the constant current control unit 15 so as to suppress the welding output. Thereby, the switching element driving section 16 is controlled, the ON period of the switching element 5 performing the operation shown in FIG. 5 is shortened according to the voltage drop, and the overload area (shaded area) in FIG. 4 is not output. The welding output point moves from a to b on the output characteristic.

As a result, the engine 1, the welding generator 2,
The rectifier 3, the capacitor 4, and the like can be downsized without having excessive capacity.

Further, since the method of limiting the welding output is to monitor the engine speed, the engine is rotated in an appropriate state without exerting an excessive decrease in the engine speed, and the capability is sufficiently exhibited. In addition, the durability can be improved.

FIG. 6 shows a circuit configuration for realizing the overload limiting operation whose characteristics are shown in FIG. 4, and is used in combination with the circuit of FIG. FIG. 7 shows operation waveforms of the pulse width modulation (PWM control) shown in FIG.

In the circuit shown in FIG. 6, during normal operation, the welding current is detected by the welding current detector 10, converted into a comparison voltage proportional to the welding current, and the comparator 23 compares the reference voltage with the comparison voltage. , The output corresponding to the comparison result is PWM
The signal is sent to the control unit 24, and an intersecting period with the voltage of the triangular wave oscillator 25 is given to the switching element driving unit 16. Then, if the welding current is smaller than the set current, the comparison voltage becomes lower than the reference voltage, the comparator 23 of FIG. 6 outputs the output voltage lower than that of FIG. 7, and the crossing period with the triangular wave becomes longer, The ON period of the switching element becomes longer.

Conversely, if the welding current is larger than the set current, the comparison voltage also increases, so that the output voltage of the comparator 23 also increases, and the ON period of the switching element also decreases. By operating the reference voltage and the comparison voltage in this manner, constant current, that is, constant current control is achieved.

Here, when the welding output becomes overloaded, the engine speed falls below the set speed and the welding generator 2
The voltage of the generator is reduced by the FV characteristic shown in FIG. The voltage is applied to the voltage detector 1
7, the reference voltage control unit 21 serving as the output suppression unit 18.
If the detected voltage is lower than the voltage set in the reference voltage control unit 21, a signal for lowering the reference voltage in proportion to the decrease is sent to the reference voltage unit 22. Send.

The reference voltage output from the reference voltage section 22 is input to a comparator 23 and compared with a comparison voltage proportional to the welding current. When the reference voltage decreases, the comparator 23 outputs a high output voltage, and the ON period in FIG. 7 is shortened (from the first direction). As a result, the welding current is reduced and the load on the engine is also reduced, so that the engine speed increases again and the generator voltage also increases. For this reason, it is attempted to output an overload, but at this time, since the engine speed again decreases, the welding output and the engine output are balanced at a certain constant value.

If the load is further increased from this state, the degree of overload is increased, and the engine speed is greatly reduced and the generator voltage is also reduced. Decrease the reference voltage.
At this time, the value of the equilibrium state between the welding output and the engine output becomes the same, and the welding output characteristic passes on the line connecting ab in FIG. 4, and as a result, E × I = constant constant power characteristic Becomes That is, an output exceeding the constant power characteristic is an overload, and corresponds to a hatched portion in FIG.

FIG. 8 shows that the frequency-voltage (FV) characteristic of a welding generator having a slowdown function is modified and the overload limit is made to work more effectively by combining two types of FV characteristics below a set frequency. This shows characteristics that enable arc start from slow down.

Generally, an engine-driven arc welding machine employs a slowdown function in its automatic voltage adjustment circuit, which lowers the engine speed when welding is not being performed. Works effectively. That is, if a current regulator (not shown) is set in the vicinity of the welding maximum output current, the constant current characteristic control unit 15 will be activated when the welding operation is started from the slowdown rotation and an arc is generated.
Operates to output the set welding current instantaneously, but the engine output is not enough for the load condition because the engine speed is not yet high, and the engine speed shifts to high speed. Cannot be performed, which causes a problem in use.

However, this problem also occurs when the rotation speed of the engine is reduced, since the output voltage of the generator is reduced to a value at which an arc can be generated as shown in the characteristics of FIG. Regardless of the current condition, even if welding is started in a state where the engine speed is low and an arc is generated, the output control unit 18 operates to suppress the welding output, so that the engine is not burdened without fail. Rotation can be transferred at high speed.

FIG. 9 shows an internal configuration of the automatic voltage adjusting circuit 14 in the circuit of FIG. 1 in order to realize the characteristics of FIG. FIG. 10 shows the relationship between the combination of two types of FV characteristics below the set frequency in FIG. 8 and the circuit operation in FIG.

As shown in FIG. 8, the first FV characteristic is steep from the predetermined frequency to the set frequency, and the second FV characteristic is gentle below the predetermined frequency. Thereby, when the engine speed becomes lower than the engine frequency of the predetermined frequency due to the first FV characteristic, the output voltage of the welding generator is sharply reduced, and the function of suppressing the welding output at the time of overload is improved. The engine speed can be shifted at high speed without imposing a burden on the engine at the time of arc start. Also, a voltage sufficient to generate an arc at the time of slowdown is ensured by the second FV characteristic. The imaginary line indicates the output curve of the engine as an FV characteristic.

In the circuit shown in FIG. 9, the frequency-voltage conversion circuit 51 outputs a voltage signal corresponding to the engine speed (frequency) from each phase voltage U, V, W of the welding generator 2.
This output is assumed to be y = ax. This voltage signal is supplied to the adder 52, and the set voltage b of the voltage setter VR1 is added. As a result, the output y1 of the adder 52 becomes y1 = a
x + b, which corresponds to the second characteristic in FIG.

The output of the adder 52 is divided into two, one of which is directly supplied to one switching contact of the analog switch IC 55, and the other is supplied to the other switching contact of the analog switch IC 55 via the offset amplifier 53. The offset-added amplifier 53 includes a voltage setting device VR.
2. The input signal is amplified by k times after the input voltage is offset in accordance with the set voltage c by 2. Therefore, the output y2 of the offset-added amplifier 53 is given by y2 = k ｛(ax +
b) + c}. This is the first characteristic in FIG.

As a result, the analog switch IC 55 is provided with the first characteristic and the second characteristic, so that either one can be output by performing the switching. This switching is performed by the output of the comparator 54. The comparator 54 compares the first characteristic with the second characteristic and gives a switching command signal to the analog switch IC 55 so as to take out the larger one. As a result, the second characteristic is extracted in a low frequency region, and the first characteristic is extracted in a high frequency region.

An output signal voltage for producing the first or second characteristic extracted by the analog switch IC 55 is supplied to a setting operation unit 56, and the signal voltage is applied to a voltage setting unit V
If the voltage is lower than the voltage set by R3, it is directly supplied to the comparator 57.
, And compared with the reference voltage Vref to generate the welding generator 2
Field F. As a result, the field current control of the welding generator 2 based on the first characteristic and the second characteristic is performed, and a desired FV characteristic is obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of the present invention.

FIG. 2 is a characteristic diagram showing a relationship between an engine output and a rotation speed in the embodiment shown in FIG.

FIG. 3 is a diagram showing frequency-voltage characteristics of the automatic voltage adjustment circuit 14 in the embodiment of FIG.

FIG. 4 is a view showing a welding output voltage-current characteristic of the embodiment shown in FIG. 1;

FIG. 5 is a diagram showing switching waveforms of a switching element 5 in the embodiment shown in FIG.

FIG. 6 is a block diagram showing an internal configuration and a related configuration of a constant current control unit 15 in the embodiment of FIG. 1;

7 is a waveform chart showing an operation of a PWM control unit 24 in the constant current control unit 15 shown in FIG.

FIG. 8 is an imaginary line showing a frequency-voltage characteristic and an engine output curve of the automatic voltage regulator 14 in the embodiment of FIG. 1 as FV characteristics.

FIG. 9 is a circuit diagram for realizing the characteristics of FIG.

FIG. 10 is an explanatory diagram showing the relationship between the combination of two types of FV characteristics below the set frequency in FIG. 8 and the circuit operation in FIG. 9;

FIG. 11 is a diagram showing a configuration of a conventional engine-driven arc welding machine.

[Explanation of symbols]

 1, 31 Engine 2, 32 Welding generator 3, 33 Rectifier 4, 34 Smoothing capacitor 5, 35 Switching element 6, 36 Reactor 7, 8, 37, 38 Welding output terminal 9, 42 Reflux diode 10, 39 Current detector 15, 40 constant current control unit 14 automatic voltage adjustment circuit 16, 41 switching element drive unit 17 voltage detection unit 18 output suppression unit 21 reference voltage control unit (output suppression unit) 22 reference voltage unit 23 comparator 24 PWM control unit 25 triangular wave Oscillator 51 Frequency-voltage conversion circuit (frequency detection circuit) 52 Adder 53 Amplifier with offset 54 Comparator 55 Analog switch IC 56 Set voltage calculation unit 57 Comparator

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) B23K 9/073

Claims (2)

(57) [Claims] 1. A welding generator driven by an engine to generate an AC output, an automatic voltage adjusting circuit for adjusting the AC output voltage of the welding generator to a constant value, and a DC generator for converting the AC output of the welding generator to a DC. Rectifier circuit, a switching circuit for switching the DC output from the rectifier circuit to output to a welding terminal, a welding current detector for detecting an output current of the switching circuit, and a detection for the welding current detector. Controlling the switching circuit according to the current,
In an engine-driven arc welding machine having a constant current control circuit that controls the output current at the welding terminal constant, a frequency detection circuit that detects a frequency of an AC output of the welding generator, and a detection frequency of the frequency detection circuit. Is a constant value when is equal to or greater than the set value, a frequency-voltage characteristic circuit that controls the welding generator so as to output a voltage having a value proportional to the frequency when equal to or less than the set value, A voltage detection circuit for detecting an output voltage, and comparing a detection voltage of the voltage detection circuit with a preset reference voltage, and when the detection voltage is lower than the reference voltage,
An output suppressing circuit that supplies a signal for suppressing a welding output to the constant current control circuit and performs switching control of the switching circuit; and wherein the constant current control circuit controls the length of an ON period in the switching circuit. An engine-driven arc welding machine configured to perform pulse width modulation. 2. A welding generator driven by an engine to generate an AC output, an automatic voltage adjusting circuit for adjusting an AC output voltage of the welding generator to a constant value, and a DC generator for converting the AC output of the welding generator to a DC. Rectifier circuit, a switching circuit for switching the DC output from the rectifier circuit to output to a welding terminal, a welding current detector for detecting an output current of the switching circuit, and a detection for the welding current detector. Controlling the switching circuit according to the current,
In an engine-driven arc welding machine having a constant current control circuit that controls the output current at the welding terminal constant, a frequency detection circuit that detects a frequency of an AC output of the welding generator, and a detection frequency of the frequency detection circuit. Is a constant value when is equal to or greater than the set value, a frequency-voltage characteristic circuit that controls the welding generator so as to output a voltage having a value proportional to the frequency when equal to or less than the set value, A voltage detection circuit for detecting an output voltage, and comparing a detection voltage of the voltage detection circuit with a preset reference voltage, and when the detection voltage is lower than the reference voltage,
An output suppression circuit that performs a switching control of the switching circuit by giving a signal for suppressing a welding output to the constant current control circuit, wherein the automatic voltage adjustment circuit has a gradual slope below a predetermined frequency lower than a set frequency. An engine-driven arc welding machine characterized by having a frequency-voltage characteristic of a stronger gradient at a frequency higher than a predetermined frequency and controlling the welding generator.