JP2014054665A - Protection control method of welding device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate an increase in the wiring number for connecting a welding power source PS and a welding torch WT, when providing a temperature sensor HD inside the welding torch WT for preventing burning.SOLUTION: When a starting switch SW becomes a closing state, a welding current Iw is conducted, and the temperature of a condensate 62 inside of a water-cooled type welding torch WT is detected by a temperature sensor HD, and when the temperature of this condensate 62 becomes a temperature reference value or more, a contact point HR of the temperature sensor HD changes to an opening state, and electric conduction of the welding current Iw is stopped. The contact point HR of the temperature sensor HD is connected in series to the starting switch SW, and an opening-closing state of the contact point HR of the starting switch SW and the temperature sensor HD is discriminated based on a change in a resistance value of a series circuit with the contact point HR of the starting switch SW and the temperature sensor HD. Thus, since the wiring number of torch cables does not increase, the welding torch WT can be restrained from becoming expensive.

Description

  The present invention relates to a protection control method for a welding apparatus that detects a condensate temperature of a water-cooled welding torch by a temperature sensor and stops energization of a welding current when the condensate temperature reaches a temperature reference value. It is.

  There are water-cooled welding torches used for arc welding such as plasma welding, TIG welding, carbon dioxide arc welding, mag welding, and MIG welding. In this water-cooled welding torch, cooling fluid such as water (hereinafter referred to as cooling water) flows into the torch, circulates it, and then flows out to cool the torch body, the nozzle, and the like. The cooling water is often circulated by providing a cooling water circulator. In this case, the cooling water cooled by the cooling water circulator is sent to the welding torch, and the condensate warmed when circulating inside the welding torch is returned to the cooling water circulator.

  If the welding torch exceeds the temperature due to an excess of the usage rate, an increase in ambient temperature, an insufficient flow rate of the cooling water, etc., the welding torch may burn out and become unusable. In order to prevent such a situation, the temperature of the condensate of the welding torch is detected by a temperature sensor, and the energization of the welding current is stopped when the temperature of the condensate reaches a predetermined temperature reference value. Conventionally, a protection control method for a welding apparatus is performed (see, for example, Patent Document 1). By this protection control method, welding is forcibly stopped when the condensate temperature correlated with the temperature rise of the welding torch reaches a temperature reference value at which the welding torch does not burn out. it can.

JP 2008-229644 A

  The welding torch is connected to the welding power source by a torch cable, and a water supply and condensate hose is included in the torch cable. Further, the welding power source and the cooling water circulator are connected by a water supply and condensate hose. Accordingly, water supply flows in the order of cooling water circulator → welding power source → welding torch, and condensate is returned in the order of welding torch → welding power source → cooling water circulator.

  In order to accurately detect the temperature rise of the welding torch, the temperature sensor needs to detect the temperature of the condensate inside the welding torch. This is because if the condensate temperature is detected inside the welding power source or the cooling water circulator, the temperature decreases while the condensate is returned, and the temperature rise of the welding torch cannot be accurately detected. . However, if a temperature sensor is provided inside the welding torch, two cables that connect the welding power source and the temperature sensor are used to notify the welding power source of the temperature sensor state (whether the condensate temperature is equal to or higher than the temperature reference value). It is necessary to add a control cable to the torch cable. When the number of control cables increases, there arises a problem that the cost of the torch cable increases. Furthermore, when the number of control cables increases, a disconnection accident due to routing or the like tends to occur.

  Therefore, in the present invention, even if the temperature sensor is provided inside the welding torch, the state of the temperature sensor can be notified to the welding power source without increasing the number of wiring of the torch cable connecting the welding power source and the welding torch. It is an object of the present invention to provide a protection control method for a welding apparatus.

In order to solve the above-mentioned problem, the invention of claim 1 is arc welding using a water-cooled welding torch, and when a start switch provided on the welding torch changes from an open state to a closed state, a welding current is obtained. The temperature of the condensate of the welding torch is detected by a temperature sensor, and when the temperature of the condensate exceeds a predetermined temperature reference value, the contact of the temperature sensor changes from a closed state to an open state. In the protection control method of the welding apparatus for stopping energization of the welding current,
The temperature sensor is provided at a position for detecting the temperature of the condensate inside the welding torch, and the contact of the temperature sensor is connected in series with the start switch, and a series circuit of the start switch and the contact of the temperature sensor Determining the open / closed state of the start switch and the contact of the temperature sensor based on the change in resistance value of
This is a protection control method for a welding apparatus.

The invention of claim 2 provides a resistor in parallel with the contact of the temperature sensor.
The protection control method for a welding apparatus according to claim 1, wherein:

  According to the present invention, even if the temperature sensor is provided inside the welding torch, the temperature of the temperature sensor can be notified to the welding power source without increasing the number of torch cables connecting the welding power source and the welding torch. . For this reason, it can suppress that the cost of a welding torch becomes high, and can suppress that the generation | occurrence | production probability of the cutting accident of a wiring becomes high.

It is a block diagram of the plasma welding apparatus for enforcing the protection control method which concerns on Embodiment 1 of this invention. FIG. 2 is an equivalent circuit diagram of a series circuit including a start switch SW and a contact HR of a temperature sensor HD in FIG. 1. It is a block diagram of the plasma welding apparatus for enforcing the protection control method which concerns on Embodiment 2 of this invention. FIG. 4 is an equivalent circuit diagram of a series circuit including a start switch SW and a contact HR of a temperature sensor HD in FIG. 3.

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

  In the following description, a plasma welding apparatus that is particularly susceptible to burning of the welding torch is taken as an example. That is, in plasma welding, since the arc is constrained by the plasma nozzle to increase the energy density, if the cooling action of the welding torch decreases, there is a risk that the welding torch will soon burn out. Therefore, it is necessary to perform sufficient protection control.

[Embodiment 1]
FIG. 1 is a configuration diagram of a plasma welding apparatus for carrying out a protection control method according to Embodiment 1 of the present invention. In the figure, the plasma gas and shield gas pipes are not directly related to the present invention and are omitted for the sake of clarity. Hereinafter, each component will be described with reference to FIG.

  A welding torch WT surrounded by a broken line includes an electrode 1, a plasma nozzle 4 surrounding the electrode 1, and a shield nozzle 5 surrounding the electrode. The electrode 1 is a non-consumable electrode, and a tungsten electrode is often used. Plasma gas (not shown) flows through the plasma nozzle 4. A shield gas (not shown) flows through the shield nozzle 5. Argon gas is often used as the plasma gas and the shielding gas. The plasma arc 3 is restricted and narrowed by the plasma nozzle 4 and is generated between the electrode 1 and the base material 2. The plasma nozzle 4 is made of copper, and a flow path through which the cooling water 6 flows is provided inside. The welding torch WT is provided with a start switch SW. The start switch SW is a normally open contact and is closed when the welding operator manually turns it on. A temperature sensor HD is provided inside the welding torch WT in order to detect the temperature of the condensate 62 flowing out from the plasma nozzle 4. The temperature sensor HD includes a normally closed contact HR, and the contact HR is opened when the condensate temperature is equal to or higher than a predetermined temperature reference value Ht. A thermostat, a thermal guard, or the like is used for the temperature sensor HD. The temperature reference value Ht is set to a value that does not cause the welding torch WT to burn out due to excessive temperature due to an excess of usage rate, an increase in ambient temperature, an insufficient flow rate of cooling water, or the like. The temperature reference value Ht is a value specific to the temperature sensor HD to be installed. Since the temperature sensor HD has hysteresis, the contact HR once changed to the open state returns to the closed state when the temperature of the condensate drops by a predetermined value from the temperature reference value Ht.

  The cooling water circulator WC connects a water supply hose 71 for flowing water 61 to the welding power source PS, and connects a condensate hose 72 for flowing condensate 62 to the welding power source PS. This cooling water circulator WC cools the condensate 62 whose temperature has risen by a blower provided therein and circulates it again as water supply 61. The circulating cooling water 6 is classified into a water supply 61 and a condensate 62.

  The welding power source PS is a power source having a constant current characteristic or a drooping characteristic, a negative output is connected to the electrode 1 of the welding torch WT via the power cable 83, and a positive output is connected to the base material 2 via the welding cable 9. And a plasma arc 3 is generated by outputting a welding current Iw and a welding voltage Vw. Further, the water supply 61 flows from the welding power source PS through the water supply hose 81 into the flow path of the plasma nozzle 4, and the condensate 62 flowing out from the flow path of the plasma nozzle 4 returns to the welding power source PS through the condensate hose 82. . Accordingly, the water supply 61 flows in the order of the cooling water circulator WC → the welding power source PS → the plasma nozzle 4, and the condensed water 62 is returned in the order of the plasma nozzle 4 → the welding power source PS → the cooling water circulator WC.

  The welding power source PS and the start switch SW provided in the welding torch WT are connected by a control kale 84, the other end of the start switch SW is connected in series with the contact HR of the temperature sensor HD, and the contact HR of the temperature sensor HD. Is connected to the welding power source PS by a control cable 85. That is, the start switch SW and the contact HR of the temperature sensor HD are connected in series. As described above, the start switch SW is a normally open contact and is turned on when turned on. The contact HR of the temperature sensor HD is a normally closed contact, and is a contact that opens when the condensate temperature becomes equal to or higher than the temperature reference value Ht. Based on the change in the resistance value of the series circuit with the start switch SW and the contact HR of the temperature sensor HD, the output of the welding power source PS is controlled as follows.

1) When the welding operator turns on the start switch SW to start welding, the start switch SW changes from the open state to the closed state. At this time, since the condensate temperature is lower than the temperature reference value Ht, the contact HR of the temperature sensor HD remains closed. Therefore, the resistance value of the series circuit formed by the contact point HR of the start switch SW and the temperature sensor HD is approximately 0Ω. When the resistance value becomes approximately 0Ω, a control current flows through the start switch SW. The welding power source PS discriminates this and starts output, and starts energization of the welding current Iw (for the sake of simplicity, the pilot arc at the time of arc start is omitted).

2) Since the start switch SW remains on and the welding is continued, if the condensate temperature becomes equal to or higher than the temperature reference value Ht, the contact HR of the temperature sensor HD changes to an open state. For this reason, the resistance value of the series circuit by the contact HR of the start switch SW and the temperature sensor HD becomes infinite. Therefore, the control current is not supplied to the start switch SW. The welding power source PS discriminates this, stops the output, and stops energization of the welding current Iw. This protects the plasma nozzle 4 from melting due to excessive temperature and burning the welding torch WT.

3) Since the contact point HR of the temperature sensor HD remains open until the condensate temperature falls to a temperature lower than the temperature reference value Ht by a predetermined value, the welding current Iw is energized even if the start switch SW is turned on. do not do. When the start switch SW is turned on after the condensate temperature decreases and the contact point HR of the temperature sensor HD returns to the closed state, the welding current Iw is energized.

  The torch cable connecting the welding power source PS and the welding torch WT includes a water supply hose 81, a condensate hose 82, a power cable 83, and control cables 84 and 85.

  FIG. 2 is an equivalent circuit diagram of a series circuit of the start switch SW and the contact HR of the temperature sensor HD in FIG. 1 described above. A constant voltage control power supply (for example, 24V) is connected to the first resistor R1 (for example, 10 kΩ). The other end of the first resistor R1 is connected to one end of the start switch SW. The other end of the start switch SW is connected to one end of a normally closed contact HR of the temperature sensor HD. The other end of the contact HR is grounded. A detection point is between the first resistor R1 and the start switch SW. The resistance value of the series circuit with the start switch SW and the contact point HR of the temperature sensor HD is referred to as a series circuit resistance value. The voltage at the detection point is called a detection voltage value, and the current value flowing through the detection point is called a detection current value. The control power supply, the first resistor R1, and the installation position are provided inside the welding power supply PS.

  When the start switch SW is in the OFF state, it is in the open state, so that the series circuit resistance value is infinite, the detection voltage value is 24V, and the detection current value is 0A regardless of the state of the contact HR of the temperature sensor HD. Become. In this state, the output of the welding power source PS is stopped. When the condensate temperature is lower than the temperature reference value Ht, the contact HR of the temperature sensor HD is in the closed state. When the start switch SW is turned on in this state, the series circuit resistance value becomes approximately 0Ω, which is detected. The voltage value is 0 V, and the detected current value is 2.4 mA. In this state, the welding power source PS starts outputting. If the condensate temperature is equal to or higher than the temperature reference value Ht and the contact HR of the temperature sensor HD is opened when the start switch SW is on, the series circuit resistance value becomes infinite and the detected voltage value Becomes 24V, and the detected current value becomes 0A. In this state, the output of the welding power source PS is stopped. Therefore, the welding power source PS can determine the state of the contact HR of the start switch SW and the temperature sensor HD based on the detected voltage value or the detected current value based on the change in the series circuit resistance value. The welding power source PS can control the stop or start of the output based on the determination result.

[Embodiment 2]
FIG. 3 is a configuration diagram of a plasma welding apparatus for carrying out the protection control method according to the second embodiment of the present invention. This figure corresponds to FIG. In FIG. 1, a second resistor R2 is added in parallel with the contact point HR of the temperature sensor HD in FIG. The rest is the same as in FIG.

  FIG. 4 is an equivalent circuit diagram of a series circuit of the start switch SW and the contact HR of the temperature sensor HD in FIG. 3 described above. This figure corresponds to FIG. This figure is the same as FIG. 2 except that a second resistor (for example, 10 kΩ) is added in parallel with the contact HR in FIG.

  When the start switch SW is in the OFF state, it is in the open state, so that the series circuit resistance value is infinite, the detection voltage value is 24V, and the detection current value is 0A regardless of the state of the contact HR of the temperature sensor HD. Become. In this state, the output of the welding power source PS is stopped. When the condensate temperature is lower than the temperature reference value Ht, the contact HR of the temperature sensor HD is in the closed state. When the start switch SW is turned on in this state, the series circuit resistance value becomes approximately 0Ω, which is detected. The voltage value is 0 V, and the detected current value is 2.4 mA. In this state, the welding power source PS starts outputting. Unlike the case of FIG. 2, when the condensate temperature is equal to or higher than the temperature reference value Ht and the contact point HR of the temperature sensor HD is opened when the start switch SW is turned on, the series circuit resistance value is different. Is 10 kΩ, the detection voltage value is 12 V, and the detection current value is 1.2 mA. In this state, since the temperature protection is activated, the output of the welding power source PS is stopped. Thus, in the case of FIG. 4, unlike the case of FIG. 2, the welding power source PS can determine that the temperature protection has been activated. For this reason, the welding power source PS can notify that the temperature protection has been operated by turning on the abnormality indicator lamp, sounding an alarm, etc., in addition to the control of stopping or starting the output.

  According to the present embodiment, the temperature sensor is provided at a position for detecting the temperature of the condensate inside the welding torch, and the contact of the temperature sensor is connected in series with the start switch, and the contact of the start switch and the temperature sensor Based on the change in the resistance value of the series circuit, the open / close state of the contacts of the start switch and the temperature sensor is determined. As a result, the welding power source can determine the state of the contacts of the start switch and the temperature sensor without increasing the number of torch cables. Therefore, in the present embodiment, even if the temperature sensor is provided inside the welding torch, the state of the temperature sensor is notified to the welding power source without increasing the number of wirings of the torch cable that connects the welding power source and the welding torch. Can do. For this reason, it can suppress that the cost of a welding torch becomes high, and can suppress that the generation | occurrence | production probability of the cutting accident of wiring becomes high.

  In the embodiment described above, the case of plasma welding in which arc welding is non-consumable electrode arc welding has been described. However, the present invention relates to other non-consumable electrode arc welding and consumable electrode arc welding using a water-cooled welding torch. It can also be applied to.

1 Electrode 2 Base material 3 Plasma arc 4 Plasma nozzle 5 Shield nozzle 6 Cooling water 9 Welding cable
61 Water supply
62 Condensate
71 Water hose
72 Condensate hose
81 Water hose
82 Condensate hose
83 Power cable
84, 85 Control Kale HD Temperature sensor HR Temperature sensor contact Ht Temperature reference value Iw Welding current PS Welding power source R1 First resistor R2 Second resistor SW Start switch Vw Welding voltage WC Cooling water circulator WT Welding torch

Claims (2)

In arc welding using a water-cooled welding torch, when a start switch provided on the welding torch changes from an open state to a closed state, energization of a welding current starts and the temperature of the condensate of the welding torch In a protection control method for a welding apparatus in which a contact of the temperature sensor changes from a closed state to an open state when the temperature of the condensate is equal to or higher than a predetermined temperature reference value detected by a sensor to stop energization of the welding current. ,
The temperature sensor is provided at a position for detecting the temperature of the condensate inside the welding torch, and the contact of the temperature sensor is connected in series with the start switch, and a series circuit of the start switch and the contact of the temperature sensor Determining the open / closed state of the start switch and the contact of the temperature sensor based on the change in resistance value of
A protection control method for a welding apparatus. Providing a resistor in parallel with the contact of the temperature sensor;
The protection control method for a welding apparatus according to claim 1.

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