JPH0573513B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a separate type arc welding machine that is separated into two or more parts and connected to each other by a cable.

[Conventional technology]

Some arc welding machines have a welding power source, wire feed control, output adjustment, etc. all integrated, but it will be easier to work if these are separated. When the above-mentioned parts are installed separately, it is necessary to connect them with cables to transmit and receive control signals. For example, in a consumable electrode arc welding machine that uses a constant voltage power source, this control signal includes an output voltage setting signal and welding start/stop signals from the output adjustment section to the welding power source, and conversely, from the welding power source to the welding power source. It is necessary to transmit a welding current detection signal for self-maintaining a welding start signal to the output adjustment section. In addition, the wire feed speed setting value, that is, the welding current setting signal and the shielding gas discharge command signal, are required between the output adjustment section and the wire feed control section, and these are transmitted through dedicated control cables. Not only does this require a large number of cable cores, and the longer the distance between devices, the more cables are required and the equipment becomes more expensive. This increases the number of opportunities and requires a great deal of effort and expense for maintenance. To solve this problem, a welding power cable is also used as a control cable, and in order to separate the welding current and control signal, the control signal is converted into a frequency signal by a voltage/frequency conversion circuit, and this frequency signal is used as the welding power cable. A method has been considered in which the signal is sent to the receiving side via a cable, and the receiving side performs inverse conversion to return it to a voltage signal. (For example, JP-A-58-47569
(No.) [Problems to be Solved by the Invention] However, in the above-mentioned prior art, although the number of cables can be reduced, it has the following serious drawbacks. That is, in arc welding, the welding current changes randomly at extremely high speed, and the current and voltage waveforms contain many high frequency components. Moreover, this high frequency component is based on fluctuations in the welding power itself and has a high energy that is incomparable to the control signal, so it is impossible to completely separate the control signal from the welding power during welding. It was extremely easy for malfunctions to occur.

In addition, even in the above method, the signal is one-way, and if it is necessary to send and receive signals in both directions at the same time, it is necessary to prepare separate cables for each, so it is not very effective in reducing the number of cables. Nakatsuta.

The present invention solves the above-mentioned drawbacks of the prior art, and is completely unaffected by the welding current not only when welding is stopped but also during welding, and moreover, it is possible to simultaneously transmit and receive signals from both parts connected to the same cable at both ends. We proposed an arc welding machine that could do this.

[Means for solving problems]

The present invention includes a voltage/current conversion circuit that converts the output voltage of an output setting device into a corresponding constant current signal in one part installed separately, and a digital digital signal that detects the output voltage of this voltage/current conversion circuit. An output voltage detection circuit that generates a signal is provided, and the other part is provided with a current/voltage conversion circuit and a switching circuit that changes the impedance of the input circuit stepwise in accordance with the digital signal to be transmitted.
The two parts are connected by a pair of control cables to enable simultaneous transmission and reception of analog signals and digital signals. Furthermore, the number of cables is further reduced by sharing one wire of the power cable as one of the cables for signal transmission.

[Effect]

As described above, the present invention first converts the control voltage signal, which is an analog signal, into a constant current signal corresponding to the signal voltage on the transmitting side, and then transmits it, and then converts this current signal inversely into a voltage signal on the receiving side. By obtaining a control voltage signal and switching the impedance of the input circuit on the analog signal receiving side in stages according to the digital signal to be transmitted, the digital signal is sent to the transmitting side. This makes it possible to simultaneously transmit and receive signals using a common cable.

〔Example〕

FIG. 1 is a connection diagram showing an embodiment of the present invention.
In the figure, 1 is a welding power source, which includes a main circuit section 101 that converts three-phase AC input into DC with characteristics suitable for welding, a current/voltage conversion circuit 102 that converts an input signal current into a voltage signal, and an input signal. an input signal detection circuit 103 that generates a logic signal depending on the presence or absence of
an output voltage control circuit 104, a current transformer 105 for detecting the welding current, a welding current detection circuit 106 that receives the output of the current transformer 105 and drives the relay WCR,
It includes an impedance switching circuit 107 consisting of a parallel circuit of an output contact WCR _b of a welding current detection circuit 106 and a resistor _Rz , and a control power supply circuit 108. 2 Consumable electrode wire (hereinafter simply referred to as wire)
It is a wire feeding device for feeding wire to a welding part, and has a wire feeding electric motor 201 and an electric motor 2 inside.
01 to feed the wire 203 from the wire reel 202, and a motor control circuit 206 for controlling the rotational speed of the motor 201 to a speed according to the setting value of the welding current setting device 205. , a sequence control unit 207 for controlling shielding gas release, stopping, welding start, stop, etc., an output voltage setting device 208 that outputs a reference voltage signal for setting the welding voltage, and an output voltage setting device 208 for controlling the output voltage of the output voltage setting device 208. A voltage/current conversion circuit 209 converts the output voltage into a corresponding constant current signal, an output voltage detection circuit 210 detects the output voltage of the voltage/current conversion circuit 209, and generates a digital signal corresponding to the stepwise change in input voltage. It includes a solenoid valve 211 for shielding gas discharge. 3 is a single-core cable for transmitting the output current signal of the voltage/current conversion circuit 209 to the welding power source 1. Reference numeral 4 denotes a single-core cable that supplies power for control to the wire feeding device 2, and each return line of the cable 3 and the cable 4 is connected to one of the welding power cables 5a and 5b.
A is shared. 6 is a welding torch, which has a built-in trigger switch for commanding the start of welding. 7
is the object to be welded and is usually at ground potential. In addition, in order to share the return wires of the output voltage adjustment signal and the control power with one side of the welding power cable 5a, the welding power cable 5a is connected to the control circuit of the welding power source 1 and the control circuit of the wire feeding device 2. Connect each to the ground wire. Further, 8 is a shielding gas supply source, which is connected to the welding torch 6 through a gas hose 9, a welding power source 1, and a wire feeding device 2.

In the embodiment shown in the figure, when the trigger switch of the welding torch 6 is closed to start welding, this switch closing signal S is sent to the sequence control section 207, which first opens the shielding gas discharge electromagnetic valve 211 to weld the shielding gas. Emitted from torch 6. After the shield gas discharge starts, the motor control circuit 206
starts electric motor 201 and starts feeding wire 203. Simultaneously with this wire feeding, or a little before this, the sequence control unit 207 issues an output command,
Welding power source 1 starts supplying output voltage. In response to a command signal from the sequence control unit 207, the output voltage E _r of the output voltage setter 208 is converted to a constant current corresponding to the set voltage E _r by the voltage/power conversion circuit 209.
It is converted into _Ir and supplied to the input impedance switching circuit 107 via the control cable 3 and the welding power cable 5. In response to the output of the input impedance switching circuit 107, the current/voltage conversion circuit 10
At step 2, the current signal I _r is returned to the original voltage signal E _r and transmitted to the output voltage control circuit 104 . Also, the detection circuit 1
03 supplies a logic signal "1" to the output voltage control circuit 104 upon receiving the current signal I _r . When the output voltage control circuit 104 receives this output voltage control signal E _r and the logic signal "1", it sends an output adjustment signal to the main circuit section 101, and the main circuit section 101 adjusts the welding power to the welding torch 6. The material to be welded is supplied to the workpiece 7, and welding is started. The output of the output voltage control circuit 104 is an ignition pulse signal for the thyristor when the main circuit section 101 uses a unidirectional thyristor to phase control rectify the AC power source.
Further, when the main circuit section 101 is an analog element such as a transistor, the signal is an analog signal that controls the conduction state of these elements.

On the other hand, during the initial period immediately after the trigger switch of the welding torch is closed, the wire 203 has not yet reached the workpiece 7 and no welding arc is generated, so no welding current flows. Therefore, the current transformer 105 does not generate an output, and the output current detection circuit 10
Relay No. 6 WCR remains de-energized. Therefore, normally closed contact WCR _b of relay WCR remains closed, the impedance of the input circuit of current/voltage conversion circuit 102 is low, and as a result, the output terminal voltage of voltage/current conversion circuit 209 becomes low. For this purpose, the output voltage detection circuit 210 detects a low voltage and outputs a welding non-starting state to the sequence control unit 207. When the wire contacts the workpiece 7 and welding current begins to flow, current transformer 105 detects this, and relay WCR of welding current detection circuit 106 is energized to open contact WCR _b . As a result, voltage/current conversion circuit 2
The impedance of the output circuit 209 becomes high, and in order to maintain a constant current output against this high impedance, the output voltage of the voltage/current conversion circuit 209 becomes I _r
It becomes higher by R _z . In response to this high output voltage, output voltage detection circuit 210 outputs a welding current detection signal to sequence control section 207. Therefore, the value of the resistor _Rz is determined by the change in the output voltage of the voltage/current conversion circuit 209 that occurs when it is connected to the voltage that occurs in the cable due to the welding current and other noises. It is necessary to set the value to be sufficiently high compared to .

Normally, the sequence control unit 207 opens and closes the output of the welding power source 1 in direct response to the opening and closing of the trigger switch while the welding current is not flowing, and when the welding current flows, the trigger switch is opened once and then the trigger switch is turned on again. The circuit is configured so that the welding start command continues to be held by the welding current detection signal until the welding current detection signal is pressed. Therefore, if the high voltage output signal of the output voltage detection circuit 210 is supplied to the sequence control section 207 as a welding current detection signal, the welding current detection signal can also be transmitted at the same time through the welding voltage setting signal transmission cable.
Of course, this signal is also used for other command signals, such as a signal for switching the wire feed speed from a low speed before welding starts to an actual high speed, switching the flow rate and type of shielding gas, or moving the welding torch in a fully automatic welding machine. It can also be used as a start command signal, etc.

Note that as one line of the signal transmission cable connecting each part, in addition to the welding power cable commonly used, a cable for supplying control power may be used. In addition, as an input impedance switching circuit provided on the receiving side of a constant current control signal, in addition to a circuit that simply turns on and off a single resistor as shown in the example shown in the figure, a plurality of input impedance switching circuits using two or more resistors can be used. The effective input impedance may be switched in multiple stages using the digitized signal. Also, similar effects can be obtained by replacing these resistors with constant voltage diodes.

Furthermore, as for each part of the welding machine that is installed separately, in addition to the welding power source and the wire feeding device as shown in the example shown, the welding power source has a wire feeding speed setting device (i.e., welding current setting device). those with
The object to be separated may be anything, such as separating only the output regulator into a separate remote control box. Further, when the welding power source used has constant current characteristics, it is sufficient to supply an output current setting signal to the welding power source and a welding voltage setting signal to the wire feeding device.

〔Effect of the invention〕

As described above, in the present invention, since the voltage signal to be transmitted is converted into a corresponding constant current signal and sent, it is possible to share a power cable that carries a large amount of power to one side of the signal transmission cable. Therefore, even if the number of cables is reduced, there will be no negative effects, and since the analog signal to be transmitted is made to be a constant current, the output voltage on the transmitting side can be changed by digitally changing the input impedance of the receiving circuit. Since this change can be detected on the constant current signal transmitting side and the digital signal from the receiving side can be determined, it is possible to simultaneously transmit and receive analog signals and digital signals in both directions using a common cable. This allows the number of cables to be minimized.

[Brief explanation of the drawing]

FIG. 1 is a connection diagram showing an embodiment of the present invention. 1... Welding power source, 101... Main circuit section, 102
...Current/voltage conversion circuit, 103...Input signal detection circuit, 104...Output voltage control circuit, 105...
... Current transformer, 106 ... Welding current detection circuit, 107
...Switching circuit, 2...Wire feeding device, 208...
... Output voltage setting device, 209 ... Voltage/current conversion circuit, 210 ... Output voltage detection circuit, 3 ... Cable, 4 ... Control power supply cable, 5a, 5b
...Power cable for welding.

Claims (1)

[Claims] 1. In a separate arc welding machine that is separated into two or more parts and connected to each other by a cable, an output adjustment section that generates an analog voltage signal to one of the mutually connected parts; A voltage/current conversion circuit that converts the output voltage of the output adjustment section into a constant current signal corresponding to the voltage and outputs the same; and a voltage/current conversion circuit that receives the output voltage of the voltage/current conversion circuit and generates a digital signal corresponding to the input voltage. An output voltage detection circuit is provided, and effective impedance of a current/voltage conversion circuit for converting a current signal from the one part into a voltage signal and an input circuit for the current signal is transmitted to the other part corresponding to the one part. a switching means for changing the digital signal stepwise according to the digital signal to be output, and a pair of cables connects the two parts, and the analog signal is sent from the one part and the digital signal is sent from the other part. Separate type arc welding machine that transmits and receives at the same time using a common cable. 2. The separate arc welding machine according to claim 1, wherein one of the pair of cables is shared with a welding power cable or a control power supply cable. 3. The separate type arc welding machine according to claim 1, wherein the switching means is means for changing the series resistance value of the input circuit for the current signal in stages. 4. The separate type arc welding machine according to claim 1, wherein the switching means is means for connecting a constant voltage diode in series to the input circuit for the current signal.