JP2007283307A - Portable dc arc welding machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a portable DC arc welding machine which can be returned to a normal welding by terminating a short-circuit state in an early stage when a short circuit occurs. <P>SOLUTION: The portable DC arc welding machine having a portable DC arc welding power source for supplying the first constant current from the welding power source to a welding output terminal and supplying the second constant current larger than the first constant current in a short-circuit state comprise: detection circuits 101, CT for detecting the welding output voltage and the welding output current at the welding output terminals P, N; a control circuit 100 for forming a control signal so as to obtain the current characteristic according to the magnitude of the welding output voltage; and output circuits 110, 111 for supplying the welding current to the welding output terminals according to the control signal from the control circuit and the detected current from the detection circuits. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a portable DC arc welder, and more particularly to a portable DC arc welder including an engine driven arc welder and a battery driven arc welder.

  This type of arc welder is configured to be brought into a construction site and used as portability indicates, and the user is not necessarily a skilled person, and the workability of welding work becomes a problem. .

  For example, in a welding machine that flows a large current when the welding rod is short-circuited to the base metal, it is easy to transfer to the arc again even if the arc disappears due to a short-circuit, but there are many spatters etc. by scattering molten metal Occurs and the welding quality deteriorates.

  On the other hand, with the characteristics that do not flow a large current at the time of short circuit, the welding quality is improved, but it is difficult to regenerate the arc after the short circuit, the arc breaks or the welding rod remains stuck to the base metal, sometimes welding The work will be interrupted.

Therefore, there is an arc welding machine that has a characteristic of flowing a constant current for welding at the time of welding, and a characteristic of flowing a larger constant current at the time of a short circuit. The transition region of both characteristics shows a drooping characteristic (see Patent Document 1). .
Japanese Patent No. 2684320

  In the arc welding machine shown in Patent Document 1, a constant current at the time of welding and a constant current at the time of a short circuit are passed, and workability is improved.

  However, depending on the skill level of the operator, the welding rod may remain fixed to the base material, and the welding operation may be interrupted. In particular, it is likely to occur in a small current region and short arc work.

  This is due to the fact that when a larger electric current is applied to the base metal, the welded portion is further welded, and the welding rod is overheated and softened by the large current, making it difficult to separate from the base material. In this case, the welding rod is temporarily removed from the welding holder and cooled, the welding rod is removed and reattached to the welding holder, and the welding operation is resumed. During this time, the welding operation is interrupted.

  The present invention has been made in consideration of the above-described points, and an object of the present invention is to provide a portable DC arc welding machine that can quickly terminate a short-circuit state and return to normal welding when a short-circuit occurs.

In order to achieve the above object, in the present invention,
A portable DC arc welding power source is provided, and welding is performed by supplying a first constant current from the welding power source to a welding output terminal. When a short circuit occurs, a second constant current greater than the first constant current is applied. In the portable DC arc welder to supply,
A detection circuit for detecting a welding output voltage and a welding output current at the welding output terminal;
(i) When the welding output voltage is higher than a first predetermined value, for outputting the first constant current, (ii) the welding output voltage is set lower than the first predetermined value (Iii) for exhibiting drooping characteristics when the welding output voltage is between the first and second predetermined values for outputting the second constant current when lower than a second predetermined value. And (iv) a control signal for causing a third constant current smaller than the first constant current to flow when the welding output voltage is lower than the second predetermined value for a predetermined time or longer. A control circuit forming
A portable DC arc welder comprising: an output circuit for supplying a welding current to the welding output terminal in accordance with a control signal from the control circuit and a detection current from the detection circuit;
Is to provide.

  As described above, the present invention cools the welding rod by flowing a third constant current smaller than the welding current when a short circuit occurs during the welding operation and the short circuit time is longer than a predetermined time. When the welding rod is pulled away from the base metal and the welding output current is zero or the welding output voltage reaches the specified value, the constant welding current is applied again. It is possible to return to the welding work. Therefore, welding can be performed efficiently even if the skill level of the operator is not high.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

Embodiment 1

  FIG. 1 shows a circuit configuration according to the first embodiment of the present invention. In this case, the welding machine is configured as an engine-driven arc welding machine in which the welding generator G is driven by the engine E. The output of the welding generator G is converted into a direct current by the rectifier SCR and then a direct current is output to the welding output terminals P and N via the direct current reactor L. On the other hand, the auxiliary output of the welding generator G is converted into a single-phase alternating current by the inverter INV and supplied to the alternating current power output terminals U and V via the breaker CB.

  The welding output supplied to the welding output terminals P and N is controlled by the welding machine control circuit 100. The welding machine control circuit 100 performs output control by controlling the rectifier SCR based on the output voltage detected by the output voltage detection circuit 101 and the welding output current detected by the current transformer CT.

The output voltage X detected by the output voltage detection circuit 101 is subjected to the following determinations (a) to (c) by the voltage determination circuit 102.
(a) V1 ≦ X
(b) V2 ≦ X <V1
(c) X <V2
As a result, three determination results are obtained depending on the relationship of the value of X with respect to V1 and V2, and (a) the first constant current circuit 105 and (b) the drooping characteristic according to the determination results. An output is given to the circuit 106, (c) the time limit circuit 103 and the gate circuit 104.

  In accordance with the determination result of the voltage determination circuit 102, in addition to the first constant current circuit 105 and the drooping characteristic circuit 106, the second constant current circuit 107 and the third constant current circuit 108 are connected to the welding current setting device 201. Alternatively, a current control signal is formed and supplied to the output current control circuit 110 based on the current set value given from the trimmer T.

  The welding current setting device 201 basically sets a current value for the first constant current (welding current) circuit 105. The second constant current (short-circuit current) circuit 107 is set to a current value that increases or decreases in a range of 2.0 to 3.0 times in conjunction with the set value of the first constant current. On the other hand, the third constant current circuit 108 has its own adjustment trimmer T, and the third constant current is set independently of the first and second constant currents.

  The first constant current circuit 105 and the second constant current circuit 107 are supplied with currents I1 and I2 from the welding current setting device 201, and the drooping characteristic circuit 106 is supplied with I1 and I2 and is based on these reference voltages. And outputs a control signal to the output current control circuit 110. The third constant current circuit 108 outputs a control signal based on the set value from the trimmer T.

  When the third constant current circuit 108 generates an output, the gate circuit 104 is closed by the output of the time limit circuit 103, and the output of the voltage determination circuit 102 is controlled by the output of the second constant current circuit 107. The circuit is never given. That is, when the output voltage X is X ≦ V2, the output is output from only one of the second constant current circuit 107 and the third constant current circuit 108, and is not output from both.

  The output current control circuit 110 compares the current control signal with the current detection signal given from the current transformer CT via the converter 202 and the output current detection circuit 109 to form a drive signal, and sends it to the thyristor drive circuit 111. To control the rectifier SCR. Thereby, the welding current given to the welding output terminals P and N is controlled.

  This current control prevents a large current from flowing for a long time, eliminates the deterioration or damage of the covering material of the coated welding rod that occurs when the welding rod is released, and can stabilize the welding quality. In addition, as a result of the welding rod being able to be easily released, the arc start is simplified for the unskilled person, and the work such as grinder finishing after welding is reduced for the skilled person. Greatly improved.

  FIG. 2 is a flowchart showing the operation of the circuit shown in FIG. 1, and FIG. 3 is a current-voltage characteristic diagram showing the operation content. The operation of the circuit shown in FIG. 1 will be described with reference to the characteristic diagram of FIG. 3 based on the flowchart of FIG.

  It is assumed that the welding machine is now started and preparation for welding output is completed (step S1). As a result, the process proceeds to step S2 to determine whether or not welding is in progress. If not, the process stays in step S2 and waits for welding to start. If welding is in progress, the process proceeds to step S3 and the welding output voltage X Is less than or equal to the reference voltage V1.

  As shown in FIG. 3, the reference voltage V1 is a transition point from the welding constant current (first constant current I1) control region to the drooping characteristic region, and the output voltage X is larger than V1, that is, V1. If there is a relationship of ≦ X, the process proceeds to step S4, the first constant current control is performed, and the process returns to step S3. This state is a normal welding operation state.

  On the other hand, if the output voltage X is lower than V1, the process proceeds to step S5 to determine whether the voltage is between the reference voltage V1 and another reference voltage V2 set lower than V1. The other reference voltage V2 is a transition point from the drooping characteristic to the constant current characteristic region at the time of short circuit. If the welding output voltage X is between the two reference voltages V1 and V2, the process proceeds to step S6, where control by the drooping characteristic is performed.

  On the other hand, when the welding output voltage X is lower than the reference voltage V2, the constant current (second constant current I2) control at the time of short-circuiting in step S7 is performed, and the second constant current control in step S8 is also performed. Time is measured.

  This time is 0.1 to 0.5 seconds, and the second constant current control is performed until this time continues. When the short-circuit state continues for a predetermined time, the process proceeds to step S9 and the third constant current control is performed. Current (I3) control is performed. As shown in FIG. 3, the third constant current I3 is smaller than the first constant current, and has a size that can reliably detect whether the welding rod is not heated and is energized, for example. The current is 3 to 10A.

  As a result of limiting the welding output current by the third constant current, the welding rod is naturally cooled, and the sticking is easily released. When the welding rod is pulled away from the base material, the welding output current becomes zero and the output voltage rises. Therefore, it is possible to determine whether or not the fixation is released in step S10 by detecting any of these. If the fixation is released, the welding operation can be performed again by returning to step S2.

  The operation of the first embodiment will be described again generally using the characteristics shown in FIG. 3 as follows. The open circuit voltage of the welding output terminals P and N (FIG. 1) is V0, and constant current control is performed with the first constant current I1 during welding.

  When a short circuit occurs during welding, constant current control is performed with the second constant current I2. When a short circuit occurs during the welding operation, the drooping characteristic region is traced back to the first constant current region in the range of the reference voltages V1 to V2, but when the welding rod is welded, the second constant current region is controlled.

  When the operation in the second constant current region continues for 0.1 to 0.5 seconds, the operation moves to the third constant current region. As a result, when the welding rod cools, it can be detached from the base material, and when it is removed, the welding output current becomes zero or the output voltage rises. This is detected, it is determined that the fixation is released, and the normal welding operation is resumed.

  Each time a short circuit occurs, the current flowing through the welding rod is dropped to the third constant current, so that the welding rod is cooled and easily detached from the base material, and the welding operation can be performed continuously and smoothly.

1 is a circuit diagram showing a circuit configuration of Embodiment 1 of the present invention. The flowchart which shows operation | movement of Embodiment 1 shown in FIG. FIG. 2 is a current-voltage characteristic diagram showing operation characteristics of the first embodiment shown in FIG. 1.

Explanation of symbols

E engine, G welder, SCR rectifier, INV inverter,
L DC reactor, CB breaker, 100 welding machine control circuit,
101 output voltage detection circuit, 102 voltage determination circuit, 103 time limit circuit,
104 gate circuit, 105 first constant current circuit, 106 drooping characteristic circuit,
107 second constant current circuit, 108 third constant current circuit,
109 output current detection circuit, 110 output current control circuit,
111 rectifier drive circuit, 201 welding current detection circuit, 202 converter,
V0, V1, V2 voltage, I1 first constant current, I2 second constant current,
I3 Third constant current.

Claims (3)

A portable DC arc welding power source is provided, and a first constant current is supplied from the welding power source to the welding output terminal for arc welding, and a second constant current larger than the first constant current at the time of a short circuit. In portable DC arc welders that supply
A detection circuit for detecting a welding output voltage and a welding output current at the welding output terminal;
(i) for outputting the first constant current when the welding output voltage is higher than a first predetermined value, (ii) the welding output voltage is set lower than the first predetermined value For outputting the second constant current when lower than a second predetermined value; (iii) for exhibiting drooping characteristics when the welding output voltage is between the first and second predetermined values And (iv) a control signal for causing a third constant current smaller than the first constant current to flow when the welding output voltage is lower than the second predetermined value for a predetermined time or longer. A control circuit forming
A portable DC arc welding machine comprising: an output circuit that supplies a welding current to the welding output terminal in accordance with a control signal from the control circuit and a detection current from the detection circuit. In the portable direct current arc welding machine according to claim 1,
The portable DC arc welding machine, wherein the control circuit includes means for determining that the fixation is released when the welding output current becomes zero after the control by the third constant current. In the portable direct current arc welding machine according to claim 1,
The control circuit includes means for determining that the fixation is released when the welding output voltage rises to the first predetermined value or more after the control by the third constant current. Welding machine.

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