JP3600309B2 - Wire feed control device for welding - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to a wire feed control device for welding, and more particularly to a technique for controlling a wire heating state in TIG welding to which cold or hot wire is added, and for detecting a tip clogging in consumable electrode arc welding or the like.
[0002]
[Prior art]
FIG. 2 shows a configuration of a welding apparatus generally used conventionally as a hot wire TIG welding method.
[0003]
An arc power supply 4 for DC welding is connected to the tungsten electrode 2 and the base material 3 in the TIG welding torch 1 and an arc 5 is formed in an argon shielding gas with the tungsten electrode 2 as a negative electrode. The welding wire 6 for welding is guided from the wire feeder 7 through the conduit 8 and the wire torch 9 connected thereto to the arc forming part, where it is brought into contact with the base material 3. The wire torch 9 is mechanically connected to the TIG welding torch 1 by the connecting member 10 and moves integrally.
[0004]
A wire heating power supply 12 is connected between the contact tip 11 and the base material 3 disposed at the tip of the wire torch 9, and a DC or AC current flows through the wire 6 to generate Joule heat, thereby increasing the melting speed of the wire 6. I have. In the case of cold wire TIG welding in which the wire 6 is not energized and heated, the wire heating power supply 12 is omitted in FIG.
[0005]
The hot wire TIG welding is necessary to adjust the heating power according to the wire feed rate of addition, when the heating power is scant, the wire 6 or come out pressing the melt pool, abuts against the base material 3 The wire torch 9 and the TIG welding torch 1 connected thereto are lifted, and as a result, the arc length becomes very long, so that welding cannot be continued. Conversely, when the heating power is excessive, the wire 6 frequently overheats and melts, generating spatter and adhering to the tungsten electrode 2 or forming an arc between the tip of the wire 6 and the tungsten electrode 2 to form a welding state. Destabilize.
[0006]
Therefore, usually, an operator monitors the welded portion so that the wire 6 is properly melted, that is, the wire tip is in a state of being melted or immediately before melting and is always in contact with the base material 3. The heating power is adjusted by adjusting the current manually.
[0007]
Regarding the heating power adjustment, the present inventors detected the occurrence of fusing from the wire voltage as described in Japanese Patent Publication No. 5-75512, and when the fusing occurred, slightly reduced the heating power of the wire. By repeatedly increasing the heating power and causing the fusing again, a control method for automatically maintaining the wire heating power in a state close to the appropriate melting state was proposed.
[0008]
It is preferable that the occurrence of fusing be as small as possible. However, in this method, it is necessary to cause fusing at a frequency of about once every two to three seconds, and generation of some spatters cannot be avoided.
[0009]
In addition, the present inventors have proposed a push-pull wire feeding device as a device for expanding and contracting a feeding route of an additional wire from a motor to a chip during welding ( Japanese Patent Application No. 6-41170 : Japanese Patent Application Laid-Open No. 7-246470). No. )
[0010]
FIG. 3 is an explanatory view showing the configuration, in which a wire is supplied to a wire introduction portion to a pull roller 17 driven by a pull motor 16 incorporated in a GMA welding torch 15 attached to a tip arm 14 or the like of an articulated welding robot 13. An extender 18 that expands and contracts according to the expansion and contraction of the path is provided, and the wire feeding speed of the push motor 20 on which the intermediate arm 19 is mounted is controlled according to the amount of expansion and contraction.
[0011]
Reference numeral 21 denotes a conduit connecting the push motor 20 and the telescopic device 18, reference numeral 22 denotes a control device for the pull motor 16 and the push motor 20, reference numeral 23 denotes a conduit for guiding a wire between the wire reel 24 and the push motor 20, and reference numeral 25 denotes a stand. , 26 are wires.
[0012]
FIG. 4 illustrates details of the expander / contractor 18; 17 is a pull feed roller attached to a pull motor; 27, 28, and 29 are limit switches provided in the expander / contractor 18; 31 is a linear shaft, 32 is a slider,
33 is an outer cylinder, 34 is a stopper, 21 is a conduit, and 26 is a welding wire.
[0013]
The slider 32 moves along the linear shaft 31 according to the expansion and contraction of the compression spring 30, and the limit switches 27, 28, and 29 are turned on / off depending on the state. The movement of the slider 32 is limited by a stopper 34 so that the compression spring 30 does not move further away from the fully extended state.
[0014]
When the pull motor 17 and the push motor 20 are fed at a constant speed in this state, the extender 18 expands and contracts as a result of a difference between the speeds of the wires sent from both motors and a change in the wire path in the conduit 21 on the way.
[0015]
The speed of the push motor 20 is controlled such that the state of expansion and contraction of the extender 18 is known from changes in the limit switches 27, 28 and 29 so that the tip of the slider 32 is always near the center limit switch 28.
[0016]
Thereby, even if the arm of the welding robot 13 moves abruptly and the wire path in the conduit 21 changes suddenly due to a large bending of the conduit 21, the amount of the change is temporarily set by the expander 18. Then, the speed of the push motor 20 is changed to return to the reference expansion / contraction state.
[0017]
[Problems to be solved by the invention]
In the proposed technique in the JP-A 7-246470 discloses the Purumota has focusing on only the this constant speed supplied by, consideration of the state of the base metal was not from Purumota. That is, in order to prevent the torch from being lifted due to the tension of the wire and the occurrence of spatter due to overheating and fusing, the welding operator must constantly adjust the wire feeding speed and the heating current while monitoring the welding condition of the wire. have.
[0018]
Further, in the conventional automatic control method using the above-described fusing phenomenon, spatter may still occur, and since spatter accumulates on the tungsten electrode, there is a problem that it is difficult to continuously operate for a long time.
[0019]
Furthermore, in the above-mentioned GMA welding, when the current-carrying tip is used for a long time, the wear of the tip hole progresses, causing a contact failure and breaking of the arc. For this reason, especially in GMA welding mounted on a welding robot, it is often performed to change the time before the arc is cut off at a fixed time.
[0020]
However, at the same time, foreign substances such as plating dust of the copper-plated wire collect in the current-carrying tip hole, and often cause wire clogging during welding. Since the time of occurrence of this wire clogging is uncertain and a practical method for detecting it in advance has not yet been realized, sudden interruption of the arc may cause welding defects in the product. This has been a major obstacle to achieving continuous unmanned operation.
[0021]
The present invention has been made based on such a background, and an object of the present invention is to reduce the frequency of occurrence of spatter in TIG welding and maintain a proper wire melting state by using a wire heating current and a wire feeding speed. It is an object of the present invention to provide a welding wire feed control device capable of performing automatic adjustment such as the above.
[0022]
Another object of the present invention is to provide a welding wire feed control device with a chip clogging progress detector capable of performing chip replacement before chip clogging occurs in GMA welding.
[0023]
[Means for Solving the Problems]
In order to achieve the above object, a first present invention provides:
A pull motor arranged on the welding torch side and controlled at a constant speed, a push motor arranged on the wire reel side, a conduit for guiding a wire between the pull motor and the push motor, and a telescopic device for expanding and contracting a wire guide path. And detecting means for detecting the expansion and contraction state of the expander,
The present invention is directed to a welding wire feed control device configured to control the rotation of the push motor so as to always have a constant telescopic device length based on a signal from the detection means.
[0024]
A feed resistance detecting means for detecting a drive current of the pull motor independently controlled at a constant speed and detecting a wire feed resistance between the pull motor and the base material is provided.
[0025]
In order to achieve the above object, a second present invention provides:
A contact detecting means for detecting whether the wire for hot wire TIG welding is in contact with or separated from the base material;
When the contact detecting means detects that the wire is separated from the base material, the wire feed resistance between the pull motor and the base material is detected by the pull motor current to detect chip clogging beforehand. It is characterized by the following.
[0027]
[Action]
As described above, in the first aspect of the present invention, the wire feed path expander is arranged between the pull motor and the push motor, feedback control is performed by the push motor so that the expansion and contraction state is constant, and the pull motor is located near the torch. In the case of feeding the wire at a constant speed in the above, the pull motor has a certain force generated by the expander, a certain force for rotating the wire feeding pull roller without load, and a wire between the wire and the base material. Will generate a force obtained by adding the force received from the outside.
[0028]
In this case, the fluctuation of the force constituted by the frictional force received when passing through the tip that guides the energized wire and the reaction force received from the base material by the wire contacting the base material results in the motor current of the pull motor being changed. Detected as fluctuation.
[0029]
Therefore, whether or not the wire is in contact with the base material is electrically detected, and based on the amount of change in the pull motor current when the wire is in contact and the amount of change in the pull motor current when the wire is not in contact, the wire is used as the base material. It is possible to detect the force applied to the wire and the progress of chip clogging, which can be useful for controlling the state of wire melting and detecting chip clogging.
[0030]
In TIG welding, a strong pressing force is generated when the wire does not melt and a hard wire hits the base material. When the wire is in an appropriate molten state, the wire is softened, so that no contact reaction force is generated even if the wire is in contact. Accordingly, when the reaction force from the base material can be detected, the wire feeding speed, the wire heating power, the wire insertion position, and the like can be changed to control the wire heating state to an appropriate value.
[0031]
Further, according to the second aspect of the present invention, occurrence of chip clogging can be detected in advance and surely, and chips can be replaced at an appropriate time before the occurrence of chip clogging, so that chip clogging during welding does not occur and defective products are not generated. , Continuous unmanned operation on robot welding lines, etc. is possible.
[0032]
【Example】
(First embodiment)
FIG. 1 is a configuration diagram of a push-pull wire feed control device for a TIG welding device according to a first embodiment of the present invention.
[0033]
In addition to the TIG arc power supply 4, the wire heating power supply 12, and the TIG welding torch 1, a wire feeding device 7 having a built-in push motor 20 for wire feeding is placed away from the TIG welding torch 1 and a wire torch incorporating a pull motor 16 is provided. An extender 18 that extends and retracts the guide path of the wire 6 is disposed between the end of the conduit 8 that guides the wire 6 toward the wire 9 and the pull motor 16. Hot wire TIG welding is performed by these devices.
[0034]
Since the expander / contractor 18 has the same structure as that of FIG. 4 described in the related art, a detailed description thereof will be omitted. Reference numeral 35 denotes a wire-related control device for forming a wire feed control and a wire heating current control signal. An expansion / contraction state detection circuit 36 receives the H (high) and L (low) signals of the limit switches 27, 28, and 29 (see FIG. 4) of the expander 18 and increases and reduces the speed by the control circuit 37 of the push motor 20. Command.
[0035]
Reference numeral 38 denotes a pull motor control circuit that controls the pull motor 16 at a constant speed in accordance with an operator's command, and 39 denotes a circuit that detects and controls the pull motor current, and outputs a control signal for instructing an increase or decrease in the wire heating current depending on the state of the pull motor current. Output to the heating current control circuit 40.
[0036]
The wire heating current control circuit 40 receives the wire speed signal from the pull motor control circuit 38, outputs an output current corresponding to the wire speed as an initial current, and thereafter increases or decreases the current in accordance with the pull motor current. Reference numeral 41 denotes a touch detection circuit incorporated in the wire heating power supply 12, which is described in Japanese Patent Publication No. 5-75511. The H and L signals indicate whether the wire 6 is in contact with or separated from the base material 3. Output to the pull motor current detection control circuit 39.
[0037]
Next, the operation of the apparatus of the present embodiment will be described. The wire feeding itself is performed by using the expander / contractor 18 according to the method described in Japanese Patent Application No. 6-41170. Therefore, the extender 18 is basically shortened to such a length that the center limit switch 28 (see FIG. 4) is turned on and off.
[0038]
Now, when the TIG arc 5 is generated and the wire 6 is fed to the molten pool, a wire heating current roughly corresponding to the wire feeding speed is supplied from the wire heating power supply 12 at first. If the wire heating current tends to be insufficient, the wire feeding speed becomes faster than the progress of the wire melting, so that the wire tip hits the base material 3 and the pressing force against the pull motor 16 acts as a reaction force. Since the pull motor 16 generates a higher torque in an attempt to feed at a constant speed, the motor current increases.
[0039]
Conversely, when the wire heating current is excessive, the wire 6 is overheated and melted, and the wire tip is separated from the base material 3. The separation signal at the tip of the wire is detected by the touch detection circuit 41, and a control signal is output to the wire heating power supply 12 so as to reduce the wire heating current. At the same time, the pull motor current at this time is measured by the pull motor current detection circuit 39 and stored as a reference state in which the wire current does not increase. Then, the wire heating current is controlled so that the pull motor current approaches this value as much as possible and the wire heating current is kept as low as possible.
[0040]
In this way, the load obtained by adding the wire feed resistance from the pull motor outlet to the tip outlet and the load from the expander 18 is reflected in the pull motor current, and the pull motor current in which these loads are always subtracted, that is, the wire 6 becomes the mother. The wire heating current is to be controlled by detecting the reaction force to the motor generated upon hitting the material 3.
[0041]
In the first embodiment, when the tip is new and the clogging has not yet occurred, the pull motor current when the wire 6 is separated from the base material 3 is measured and stored as a reference value of the new tip state. The subsequent increase in the pull motor current when the wire 6 is separated from the base material 3 is determined to be due to chip clogging. Therefore, the occurrence of chip clogging in TIG welding can be detected from the change in the pull motor current.
[0042]
In the first embodiment, the case where the wire heating power is controlled by detecting the reaction force of the wire 6 hitting the base material 3 using the touch detection circuit 41 has been described. However, when the wire feeding resistance due to chip clogging is small, the same control can be performed simply by controlling the wire heating power so that the pull motor current becomes constant.
[0043]
(Second embodiment)
Next, a case where the method of the present invention is applied to consumable electrode arc welding will be described. Actually, the configuration is substantially the same as that of the conventional device shown in FIG. 3, and only the pull motor current detection circuit 39 in the wire feed control device 35 shown in FIG. 1 is added to the motor control device 22. Therefore, the drawings are omitted.
[0044]
In the case of GMA welding, an arc is generated at the tip of the wire. Except at the time of arc start, the wire tip may momentarily contact (short-circuit) with the base material, but it does not reach a state where it hits the base material and generates a reaction force, and most of it is in space. It can be said that it is in a floating state.
[0045]
Therefore, the pull motor current when the chip is in a new state is measured and stored, and it is easy to detect the occurrence of chip clogging from the temporal change of the pull motor current during use.
[0046]
According to the first and second embodiments, in TIG welding, the appropriate heating power of the wire 6 can be automatically maintained in a state where the generation of spatter is extremely small, so that the operator constantly monitors the welding power during welding to adjust the heating power. It is unnecessary to perform welding, which greatly contributes to the realization of unmanned and labor-saving welding.
[0047]
In addition, when the semi-automatic TIG welding is used, semi-automatic TIG welding can be easily performed without causing a situation in which the wire 6 hits the base material 3 to separate the torch from the base material 3 and cannot be welded.
[0048]
That is, in a normal semi-automatic TIG welding torch, there is also a meaning of minimizing the wire tension caused by the difficulty of adjusting the wire feeding speed, and the wire 6 is formed along the surface of the base material as much as possible in the molten pool under the arc. It is being sent to.
[0049]
For this reason, if the arc length becomes slightly longer or shorter, the position where the tip of the wire comes into contact with the base material 3 is greatly displaced, and the wire comes off the molten pool, causing a problem that welding becomes difficult. Even with wires, semi-automatic TIG welding of TIG welding has hardly been put to practical use.
[0050]
On the other hand, the method of inserting wires in parallel from the inside of a shield nozzle along a tungsten electrode according to JP-A-3-297574, which is the present inventors, has been practically used in robot welding, but in semi-automatic TIG welding, Since the arc length is unstable and the wire melting rate is apt to change, the wire is more likely to hit the base material and lift the torch more easily, so that it has not been possible to use it.
[0051]
However, since the present invention eliminates the wire tension, semi-automatic TIG welding can be performed with a smaller torch capable of feeding the wire from the inside of the shield nozzle.
[0052]
When the present invention is applied to GMA welding, the occurrence of chip clogging can be detected in advance, and the chip can be replaced at an appropriate time before the occurrence of chip clogging. Is avoided, and continuous unmanned operation in a robot welding line or the like is possible.
[0053]
【The invention's effect】
The first aspect of the present invention is configured as described above, the force of pressing the wire against the base material can be detected, based on the wire feed speed, wire heating power, changing the wire insertion position, etc. The wire heating state can be controlled to an appropriate value. Further, the progress of chip clogging can be detected, which is useful for detecting chip clogging.
[0054]
Further, according to the second aspect of the present invention, occurrence of chip clogging can be detected in advance and surely, and chips can be replaced at an appropriate time before chip clogging occurs. Therefore, chip clogging during welding does not occur and defective products do not occur. It has features such as continuous unmanned operation on robot welding lines.
[Brief description of the drawings]
FIG. 1 is a configuration diagram illustrating an example of a hot wire TIG welding apparatus according to an embodiment of the present invention.
FIG. 2 is a configuration diagram of a conventional hot wire TIG welding apparatus.
FIG. 3 is a configuration diagram of a push-pull wire feeding device according to the prior application of the present invention.
FIG. 4 is a configuration diagram of the expander.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 TIG torch 2 Tungsten electrode 3 Base material 4 Arc power supply 5 Arc 6 Wire 7 Wire feeding device 8 Conduit 9 Wire torch 10 Connecting member 11 Contact chip 12 Heating power supply 16 Pull motor 18 Telescopic device 20 Push motor 22 Motor control device 35 Wire related control Device 36 Expansion / contraction state detection circuit 37 Push motor control circuit 38 Pull motor control circuit 39 Pull motor current detection circuit 40 Wire heating current control circuit 41 Touch detection circuit

Claims (4)

A pull motor arranged on the welding torch side and controlled at a constant speed;
A push motor arranged on the wire reel side,
A conduit for guiding a wire between the pull motor and the push motor,
A telescopic device that expands and contracts the wire guide path,
Detection means for detecting the expansion / contraction state of the expander,
In the welding wire feed control device configured to control the rotation of the push motor so as to always have a constant telescopic unit length based on the signal from the detection means,
A welding wire feeder comprising feed resistance detecting means for detecting a drive current of the pull motor independently controlled at a constant speed and detecting a wire feed resistance between the pull motor and the base material. Control device. 2. The welding wire feeding control device according to claim 1, wherein the wire heating power is adjusted so as to keep the wire feeding resistance between the wire feeding pull motor and the base material constant. The method according to claim 2, further comprising detecting means for detecting whether the wire is in contact with or separated from the base material, wherein a wire feed resistance between the pull motor and the base material when the wire is in contact with the base material is: A wire feed control device for welding, wherein the wire heating power is controlled so as to approach the wire feed resistance between the pull motor and the base material when the wire is separated from the base material. A contact detecting means for detecting whether the wire for hot wire TIG welding is in contact with or separated from the base material;
When the contact detecting means detects that the wire is separated from the base material, the wire feed resistance between the pull motor and the base material is detected by the pull motor current, so that chip clogging is detected beforehand. A wire feed control device for welding, characterized in that:

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