JPH04274877A - Method and device for feeding welding wire - Google Patents

Abstract

PURPOSE:To precisely control a welding wire feed speed and to improve the durability of piezoelectric elements for feeding in feeding of the welding wire by utilizing the piezoelectric elements. CONSTITUTION:The welding wire 2 is gripped at all times by either one contactor of a 1st contactor 12 and 2nd contactor 15 movable in the feed direction by the 2nd piezoelectric element 14, by which the generation of the deviation before and behind the feed direction of the welding wire 2 is eliminated and the wire feed speed is precisely controlled.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a welding wire feeding method and a welding wire feeding device used in automatic welding and the like.

0002

2. Description of the Related Art A welding wire feeding device using a piezoelectric element is disclosed in Japanese Patent Laid-Open No. 2-121776. In this device, the piezoelectric element is arranged obliquely to the feeding direction of the welding wire, and the wire contactor attached to the piezoelectric element makes an elliptical motion as the piezoelectric element expands and contracts. . This elliptical movement of the wire contact causes the wire contact to grasp and feed the welding wire, release the wire contact from the welding wire, and retreat the wire contact from the welding wire, thereby welding the welding wire. The feeding to the parts is carried out continuously. In this way, in a welding wire feeding device using a piezoelectric element, the displacement per stroke is extremely small, and the welding wire is fed by repeatedly feeding the welding wire intermittently by the elliptical movement of the wire contactor. A predetermined speed is obtained.

0003

However, in welding using a feeding device that utilizes the elliptical motion of a wire contactor as disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 2-121776, the following problems exist. When a welding wire drive unit having a wire contact driven by a piezoelectric element is placed on the wire reel side, the wire conduit that serves as a passage for the welding wire has frictional resistance, so the wire contact does not grasp the wire. Compressive stress may occur in the welding wire near the wire contact when the welding wire is fed out one stroke. In addition, in the case of a push-pull method in which a separate welding wire drive unit is added to the torch side, the welding wire is pulled toward the welding wire drive unit on the torch side while the wire contactor grasps the wire. Tensile stresses may also occur in the wire in the vicinity of the wire contact.

On the other hand, when a welding drive unit having a wire contact driven by a piezoelectric element is placed on the torch side, the wire conduit that serves as the welding wire passage has frictional resistance, so the wire contact When the wire is grasped and fed out one stroke, tensile stress may be generated in the welding wire near the wire contact. In addition, if another welding wire drive unit is added to the wire reel side, the welding wire is pushed out to the welding wire drive unit side on the wire reel side while the wire contactor is gripping the wire. Compressive stresses may also develop in the wire near the contacts.

[0005] In this way, the welding wire near the welding wire drive unit using a piezoelectric element always experiences complex stress fluctuations as described above, and even if the wire contactor feeds the welding wire by a predetermined amount, the wire While the contact moves back to the position immediately before feeding starts, the welding wire may shift back and forth in the feeding direction. Complex stress fluctuations near the wire contactor are also affected by the bending and wear of the wire conduit, making it difficult to accurately control the wire feeding speed. When the wire feeding speed becomes unstable, arc length and welding current fluctuate, spatter generation increases, and base metal penetration becomes unstable.

[0006] Furthermore, the wire feeding system disclosed in the above publication has the following problems. When grasping and feeding the welding wire, the piezoelectric element stretches and at the same time its tip is displaced along the wire feeding direction, so bending force acts on the entire piezoelectric element, which tends to cause cracks between each laminated plate and reduce durability. becomes a problem.

[0007] The present invention focuses on the above-mentioned problems, and provides a method for accurately controlling the wire feeding speed in feeding welding wire using a piezoelectric element and increasing the durability of the feeding piezoelectric element. The object of the present invention is to provide a possible welding wire feeding method and device.

[0008]

[Means for Solving the Problems] A welding wire feeding method according to the present invention that meets this objective includes gripping the welding wire with a first contact and then releasing the grip of the welding wire with the second contact. In this state, the first contact is advanced in the welding wire feeding direction, and when the first contact has finished advancing, the welding wire is gripped by the second contact, and the welding wire is moved by the second contact. After gripping the welding wire, the welding wire is fed by releasing the grip of the welding wire by the first contact and, in this state, retracting the first contact to its original position.

[0009] Furthermore, the welding wire feeding device according to the present invention in accordance with this object includes a first
a first piezoelectric element that drives the first contact in the radial direction of the welding wire, and a second piezoelectric element that drives the first contact in the welding wire feeding direction; a second contact provided adjacent to the first contact and capable of gripping the outer peripheral surface of the welding wire; and a third piezoelectric element that drives the second contact in the radial direction of the welding wire. It consists of a device equipped with the following.

0010

[Operation] In the welding wire feeding method and device configured as described above, the welding wire is held by the first contact driven by the first piezoelectric element, and in this state, the first contact is The welding wire is advanced in the feeding direction by the second piezoelectric element. This advancement of the first contact causes
Welding wire is fed by a predetermined amount. Once advancement of the first contact is completed, the welding wire is gripped by the second contact driven by the third piezoelectric element. When the welding wire is gripped by the second contact, the grip of the welding wire by the first contact is released, and the first contact is driven back to its original position by the second piezoelectric element. Next, the welding wire is gripped again by the retracted first contact, and when this gripping operation is completed, the gripping of the welding wire by the second contact is released, and the welding wire is gripped by the forward movement of the first contact. Delivery will take place. By repeating such operations, the welding wire is continuously fed and a predetermined feeding speed is obtained.

[0011] Here, since the welding wire is always held by at least one of the first contactor and the second contactor, even if tensile stress or the like is applied to the welding wire, the welding wire The wire does not shift back and forth in the feeding direction, making it possible to accurately control the wire feeding speed. Furthermore, since the second piezoelectric element for feeding the welding wire drives the first contactor in the feeding direction of the welding wire, no bending force acts on the second piezoelectric element. , it becomes possible to improve the durability of the second piezoelectric element for feeding the welding wire.

0012

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the welding wire feeding method and device according to the present invention will be described below with reference to the drawings.

First Embodiment FIGS. 1 to 3 show a first embodiment of the present invention. FIG. 3 shows an example of a welding device for automatically welding workpieces. Reference numeral 1 indicates a wire reel in which the welding wire 2 is stored in a wound state. 3 indicates a welding torch that positions the tip of the welding wire 2 at the welding location of the workpiece and performs welding. Wire reel 1 and welding torch 2
A welding wire feeding device 4 for feeding the welding wire 2 on the wire reel 1 side to the welding torch 3 side is provided between. The welding wire feeding device 4 and the welding torch 3 are connected by a flexible tubular wire conduit 5, and the welding wire 2 is inserted into the wire conduit 5.
is inserted. The welding torch 2 can be freely moved according to the shape of the workpiece. In this embodiment, the wire conduit 5 is connected to a welding transformer 7 via a power cable 6.

FIG. 1 shows the welding wire feeding device 4 in FIG. In FIG. 1, 11 indicates a cylindrical housing. The housing 11 is partitioned into chambers 11b and 11c by a partition wall 11a. Housing 1
A welding wire 2 is inserted through the center of the welding wire 1 . On the left and right sides of the chamber 11b of the housing 11, first contacts 12,
A first piezoelectric element 13 and a second piezoelectric element 14 are respectively provided. The left and right first contacts 12 are arranged to face each other. The first contact 12 has a grip portion 12
a can be elastically deformed in the radial direction of the welding wire 2. A substantially T-shaped gap is formed in the first contactor 12, and a first piezoelectric element 13 is arranged in this gap. The first piezoelectric element 13 is composed of a laminated piezoelectric element, and expands and contracts in response to a signal from the control section 8 shown in FIG. The grip portion 12a of the first contactor 12 can be displaced in the radial direction of the welding wire 2 by expansion and contraction of the first piezoelectric element 13. The welding wire 2 is gripped by the gripping portions 12a of the left and right first contacts 12 when the first piezoelectric element 13 is extended.

The left and right second piezoelectric elements 14 housed in the chamber 11b of the housing 11 are composed of two piezoelectric elements 14a and 14b in this embodiment. Piezoelectric element 14a
, 14b have displacement directions that match the feeding direction of the welding wire 2, and are arranged to sandwich the first contact 12. The piezoelectric elements 14a and 14b are composed of laminated piezoelectric elements, and are adapted to expand and contract in response to a signal from the control section 8 shown in FIG. The first contactor 12 is driven in the feeding direction A of the welding wire 2 by the expansion of one piezoelectric element 14a and the contraction of the other piezoelectric element 14b.

A second contact 15 and a third piezoelectric element 16 are housed on the left and right sides of the chamber 11c of the housing 11, respectively. The left and right second contacts 15 are arranged to face each other. The second contactor 15 is movable in the radial direction of the welding wire 2. Third piezoelectric element 13
is composed of a laminated piezoelectric element, and expands and contracts in response to a signal from the control section 8 shown in FIG. The second contactor 15 is configured to be displaced in the radial direction of the welding wire 2 by expansion and contraction of the third piezoelectric element 16. The welding wire 2 is gripped by the left and right third contacts 15 when the third piezoelectric element 16 is extended.

Next, the welding wire feeding method and its operation in the first embodiment will be explained. FIG. 2 shows the welding wire feeding operation by the welding wire feeding device 4. As shown in FIG. FIG. 2A shows a state in which the welding wire 2 is held by the first contact 12 and the second contact 15. Here, to explain the welding wire feeding state,
Mark B. In FIG. 2(a), the mark B is located at the first contact 12. In FIG. When the gripping of the welding wire 2 by the first contactor 12 is completed, as shown in FIG. 2(b), the gripping of the welding wire 2 by the second contactor 15 is released. When the grip of the welding wire 2 by the second contactor 15 is released, as shown in FIG. Moved to A. When the first contactor 12 is moved by a predetermined amount by the second piezoelectric element 14, (
As shown in d), the welding wire 2 is gripped by the second contact 15. When the welding wire 2 is gripped by the second contactor 15, as shown in FIG.
The grip of the welding wire 2 by the contactor 12 is released. When the grip of the welding wire 2 by the first contactor 12 is released, the first contactor 12 is returned to its original position by the driving force of the second piezoelectric element 14, as shown in FIG. 2(f). fall back. When the first contact 12 retreats to its original position, the welding wire 2 is gripped by the first contact 12, as shown in FIG. 2(g). When the operation shown in FIG. 2(g) is completed, the operation shifts to the operation shown in FIG. 2(a) again, and the same operation as described above is repeated, and the welding wire 2 is continuously fed.

While the welding wire 2 is being fed, the welding wire 2
is always held by at least one of the first contact 12 and the second contact 15, so tensile stress and stress are applied to the welding wire 2 due to frictional resistance with the wire conduit 5, etc. Even if compressive stress is applied, welding wire 2
will no longer shift back and forth in the feeding direction. therefore,
It becomes possible to accurately control the feeding speed of the welding wire 2, and by stabilizing the arc length and welding current, the occurrence of spatter is suppressed, and penetration into the base metal is also improved. Also,
The second piezoelectric element 14 for feeding the welding wire 2 is
The displacement direction is matched with the feeding direction of the welding wire 2,
Since the first contactor 12 is driven in the welding wire feeding direction, no bending force acts on the second piezoelectric element 14, which reduces the durability of the second piezoelectric element 14 for feeding the welding wire. This makes it possible to improve sexuality.

Second Embodiment FIG. 4 shows a second embodiment of the invention. The difference between the second embodiment and the first embodiment is that the chamber 1 of the housing 11
1c only, and the other parts are the same as in the first embodiment. Therefore, by assigning the same reference numerals as in the first embodiment to the corresponding parts, the explanation of the corresponding parts will be omitted, and only the different parts will be explained. . The same applies to other embodiments to be described later. A second contactor 15 is provided in the chamber 11c of the housing 11.
, a third piezoelectric element 16, and a fourth piezoelectric element 17 are provided. In the first embodiment, the second contactor 15 only had the function of gripping the welding wire 2, but in this embodiment, it also has the function of feeding the welding wire 2. Fourth
The piezoelectric element 17 has a function of driving the second contactor 15 in the feeding direction of the welding wire 2. Note that the structure of the second contactor 15 in this embodiment is different from that of the first contactor 1.
5, and the structure of the third piezoelectric element 16 is similar to that of the first piezoelectric element 13. Similarly, the fourth piezoelectric element 1
The structure of 7 is similar to the structure of the second piezoelectric element 16. That is, in this embodiment, both chambers 11b of the housing 11
, 11c have almost the same hardware configuration.

In the second embodiment configured as described above, when a certain amount of welding wire 2 is fed by the first contact 12, the welding wire 2 grips the second contact 15 and A fixed amount is further fed by the driving force of the piezoelectric element 17 of No. 4. Therefore, the amount of welding wire 2 fed can be made larger than in the first embodiment.

Third Embodiment FIG. 5 shows a third embodiment of the present invention. In the first and second embodiments, the welding wire 2 was held from both sides by the left and right first contacts 12 or second contacts 15, but in this embodiment, the welding wire 2 is The welding wire is gripped by a pressure roller. In FIG. 5, a rotatable first pressure roller 21 is provided at a position facing the first contact 12 movably held by the holder 30. As shown in FIG. Similarly, a rotatable second pressure roller 22 is provided at a position opposing the second contactor 15 movably held by the holder 30 . Welding wire 2 is gripped by first contactor 12 and first pressure roller 21 when first piezoelectric element 13 is extended. Similarly, the welding wire 2 is gripped by the second contactor 15 and the second pressure roller 22 when the third piezoelectric element 16 is extended. In the third embodiment configured in this manner, components on the right side of the left and right contacts, piezoelectric elements, etc. are not required, and the configuration of the welding wire feeding device can be simplified. Other operations are similar to those of the second embodiment.

Fourth Embodiment FIGS. 6 to 8 show a fourth embodiment of the present invention. In the first to third embodiments described above, the direction of expansion and contraction of the piezoelectric element that grips the welding wire was perpendicular to the feeding direction of the welding wire, but in this embodiment, for the reason described later, The structure has been adopted.

When inserting the welding wire into the feeding path in preparation for welding work, if the above-mentioned gap between the contact and the welding wire is not sufficiently secured, the welding wire will get caught in the middle, reducing work efficiency. Deteriorate. Additionally, if a thick part of the welding wire passes through due to variations in the welding wire diameter during welding, the frictional resistance between the welding wire and the contact will increase, worsening wire feeding performance and making welding unstable. . In order to avoid these problems, if the gap between the contact and the welding wire is increased, the pressing force of the contact on the welding wire becomes insufficient. Therefore, in order to increase the elongation deformation of the laminated piezoelectric element, measures such as increasing the voltage applied to the piezoelectric element or increasing the number of laminated layers are taken. However, increasing the voltage puts a strain on the piezoelectric element and also poses problems in terms of insulation. Furthermore, when increasing the number of laminated piezoelectric elements, the piezoelectric elements bulge in the radial direction of the welding wire, leading to an increase in the size of the feeding device. In this example, we focused on the above-mentioned problem, and created a configuration that can increase the displacement of the contact that grips the welding wire while suppressing the bulge of the welding wire in the radial direction of the feeding device. It is being

In FIG. 6, the chamber 11b of the housing 11
On the left and right sides, a first contactor 12, a first piezoelectric element 13,
A second piezoelectric element 14 and a holder 30 are respectively provided. The left and right first contacts 12 are arranged to face each other. The first contactor 12 is connected to the first piezoelectric element 13
Supported by The first piezoelectric element 13 includes a piezoelectric element 13a and a piezoelectric element 13b. As shown in FIG. 7, one side of the piezoelectric element 13a is connected to one inclined surface 12a of the first contact 12. As shown in FIG. The other end of the piezoelectric element 13a is connected to one inclined surface 30a of a holder 30 movably arranged in the chamber 11b. One of the piezoelectric elements 13b is connected to the other inclined surface 1 of the first contactor 12.
It is connected to 2b. The other end of the piezoelectric element 13b is connected to the other inclined surface 30b of the holder 30.

The angle formed between the welding wire and the piezoelectric elements 13a and 13b is set to θ. Piezoelectric elements 13a, 13
By setting b to the angle θ, the amount of displacement of the first contactor 12 is made large. This displacement will be explained below. FIG. 8 shows the state of displacement of the first contact due to elongation deformation of the piezoelectric elements 13a and 13b. In the figure, L indicates the length of the piezoelectric element, and when a voltage is applied with P1 fixed, the piezoelectric element is elongated by ΔL. However, since it interferes with the displacement of the other piezoelectric element, point Q1 actually moves to Q2, and the amount of movement LG becomes the amount of displacement of the contact. Here, ΔL is minute compared to L, and the amount of movement of the first contactor 12 can be determined by the approximate expression LG≈ΔL/sinθ. The displacement magnification ratio when the angle θ is set to a predetermined value is shown below. Displacement magnification rate when θ=10° LG/△L≒5.
Displacement magnification rate when 8 times θ=45° LG/△L≒1.
4 times When the angle θ is smaller than 10°, the resultant force acting on the first contactor 12 is small, making it difficult to reliably feed the welding wire 2. Further, when the angle θ is larger than 45°, the magnification rate of displacement is not so large, and it becomes difficult to reduce the device in the radial direction. Therefore, it is desirable to set the angle θ in the range of 10° to 45°.

In this embodiment, the chamber 11b of the housing 11
The welding wire 2 is gripped and fed by the components arranged in the chamber 11c, and the welding wire 2 is only gripped by the components arranged in the chamber 11c. Note that the structures of the second contact 15 and the third piezoelectric element 16 arranged in the chamber 11c are similar to those of the first contact 12 and the first piezoelectric element 13 arranged in the chamber 11b.

In the fourth embodiment configured as described above, the first piezoelectric element 13 for gripping the welding wire 2 is
and the second piezoelectric element 16 are not arranged perpendicularly to the welding wire 2, but are arranged at an appropriate angle, so that the device can be made compact in the radial direction, and the The welding wire 2 is also reliably gripped by the second contact 12 and the second contact 15. Note that the first contact 1
2 in the feeding direction of the welding wire.
4 is the same as the other embodiments, and no bending force or the like acts on the second piezoelectric element 14.

[0028]

As explained above, when using the welding wire feeding method and device according to the present invention, the welding wire is fed by at least one of the first contact and the second contact. Since it is always held, the welding wire will not shift back and forth in the feeding direction even if tensile stress or compressive stress is applied to the welding wire. Therefore, it is possible to accurately control the feeding speed of the welding wire, suppressing the occurrence of spatter, and improving penetration into the base metal. Furthermore, since the second piezoelectric element for feeding the welding wire drives the first contact in the feeding direction of the welding wire, bending force is prevented from acting on the second piezoelectric element. can be avoided. Therefore, cracks due to bending force are less likely to occur in the second piezoelectric element,
The durability of the second piezoelectric element for feeding welding wire can be increased.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a welding wire feeding device used in a welding wire feeding method according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view showing the order in which welding wires are fed by the apparatus of FIG. 1;

FIG. 3 is a schematic configuration diagram of an automatic welding device in which the device of FIG. 1 is used.

FIG. 4 is a sectional view of a welding wire feeding device according to a second embodiment of the present invention.

FIG. 5 is a sectional view of a welding wire feeding device according to a third embodiment of the present invention.

FIG. 6 is a sectional view of a welding wire feeding device according to a fourth embodiment of the present invention.

FIG. 7 is a partially enlarged sectional view of FIG. 6;

8 is a characteristic diagram showing the relationship between the amount of displacement of each piezoelectric element and the amount of displacement of a contact in the device of FIG. 6; FIG.

[Explanation of symbols] 1 Wire reel 2 Welding wire 3 Welding torch 4 Welding wire feeding device 12 First contact 13 First piezoelectric element 14 Second piezoelectric element 15 Second contact 16 Third piezoelectric element 17 Fourth piezoelectric element 21 First pressure roller 22 Second pressure roller

Claims (2)

[Claims] Claim 1: After the welding wire is gripped by the first contact, the grip of the welding wire by the second contact is released, and in this state, the first contact is advanced in the welding wire feeding direction. , the welding wire is gripped by the second contactor when the first contactor has completed advancing, and after the welding wire is gripped by the second contactor, the gripping of the welding wire by the first contactor is released. A welding wire feeding method characterized in that the welding wire is fed by retracting the first contactor to its original position in this state. [Claim 2] A first member capable of gripping the outer peripheral surface of the welding wire.
a first piezoelectric element that drives the first contact in the radial direction of the welding wire, and a second piezoelectric element that drives the first contact in the welding wire feeding direction; a second contact provided adjacent to the first contact and capable of gripping the outer peripheral surface of the welding wire; and a third piezoelectric element that drives the second contact in the radial direction of the welding wire. A welding wire feeding device comprising: