JPH07116876A - Welding equipment by laser beam - Google Patents

Abstract

PURPOSE:To join a sleeve to a slender tube with a small diameter by holding high accuracy in the centering of a working head for welding by a laser beam. CONSTITUTION:A center hole is formed by piercing the inner part of a housing 1 in its axial direction, and an optical fiber 2, a converging optical system 3 and a reflection mirror 4 are provided in this center hole. Also, a guide shaft 9 is provided in an extended part in the longitudinal direction of the housing 1. Guide grooves 10 are formed on the circumference of this guide shaft 9, dividing in equal parts. Centering wires 11 are fitted respectively in these guide grooves 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser welding apparatus used for repairing a damaged portion of a heat transfer tube of a heat exchanger by covering the damaged portion with a sleeve from the inside.

[0002]

2. Description of the Related Art A large number of so-called thin tubes having a small diameter are used for heat transfer tubes of heat exchangers. When damage occurs in the thin tubes, a sleeve for covering the damaged portion from the inside is repaired. The outer diameter of this sleeve is somewhat smaller than the inner diameter of the thin tube to be inserted, and it is necessary to expand the sleeve after insertion to make it closely contact with the thin tube and further fix it by welding.

The laser welding method is most suitable for welding the sleeve to the inner surface of the thin tube. This allows the processing head to be sent inside a narrow tube, where the laser light is guided by the processing head sent inside the tube and focused through the lens, while being deflected by the mirror to the target part. Will be converged.

In using this laser welding method, the welding line of the sleeve that follows the inner surface of the thin tube is on the circumference,
The quality of centering of the processing head with respect to the center of the thin tube becomes a problem. In particular, if the inner diameter of the thin tube is as small as 10 to 14 mm, it becomes difficult to keep the centering accuracy high.

For example, the application of the pantograph system as disclosed in Japanese Patent Application Laid-Open No. 2-200387 is not suitable for practical use because the thin tube having the above size does not have enough room to receive the link mechanism. On the other hand, although an air bag type centering method is also conceivable, drawing an air pipe or the like into a place where the inside of the thin tube is originally narrow has a large effect on other parts, and is applicable to small tubes with a small diameter. difficult.

[0006]

In the welding of the sleeve to the thin tube, the joint between the members is fixed by the inner peripheral surface seal welding, and the joint is sealed so that the fluid in the thin tube does not leak from the damaged portion of the thin tube to the outside of the thin tube. There is a need. In order for this seal welding to be performed correctly between the sleeve and the thin tube, the centering mechanism of the processing head that irradiates the joint with laser light must be appropriate.

In the above-mentioned pantograph system, as the inner diameter of the thin tube becomes smaller, it is necessary to make each element contained in the thin tube smaller. For example, within 10 mm, the link mechanism, which is indispensable for centering the machining head, has a functional problem. May not be configurable as

Further, in a method in which an air bag is provided in the thin tube and is expanded by air sent from the outside to perform centering, the processing head is at a bare limit for housing the condenser lens, the reflection mirror and the like. However, it is necessary to additionally install air piping etc. for thin tubes within 10 mm,
It remains doubtful whether the device will work using this method.

Therefore, an object of the present invention is to provide a laser welding apparatus capable of joining a sleeve to a small-diameter thin tube while keeping the centering accuracy of the processing head high.

[0010]

A laser welding apparatus according to the present invention axially penetrates the inside of a housing to form a space, and an optical fiber, a condensing optical system and a reflection mirror are housed in the space, and At least one guide shaft is provided at the front end and / or the rear end in the longitudinal direction, and the guide shaft is divided into at least three guide grooves equally on the circumference, and each guide groove is defined in the radial direction. It is characterized in that the centering wire is attached by giving a given amount of deflection.

[0011]

The guide shaft at the front end and / or the rear end of the housing in the longitudinal direction is circumferentially equally divided into three guide grooves, and the guide shaft is bent in the radial direction. Each lead wire is attached.

At this time, the deflection given to the centering wire is determined according to the inner diameter of the sleeve. When the bending head is bent when the processing head is fed into the thin tube, the centering wire is contracted. Returns to the original position and adheres to the inner surface of the sleeve. In this way, the processing head can be accurately centered.

The centering wire does not require a large space because it is made of a thin wire material such as a piano wire. Therefore, the inner diameter of the sleeve is, for example, 1
The processing head can be centered with high accuracy even when the diameter is smaller than 0 mm.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings.

In FIG. 1, reference numeral 1 is a hollow cylindrical housing, and a center hole 1a is formed in the housing 1 so as to penetrate the housing 1 in the axial direction. Optical fiber 2,
The condensing optical system 3 that condenses the laser light and the reflection mirror 4 that deflects the laser light toward the processing target are arranged in the center hole 1a.

Among these elements, particularly the condensing optical system 3 and the reflecting mirror 4 have a housing having an outer diameter dimension slightly smaller than the inner diameter of a sleeve (not shown) fixed to the inner surface of a thin tube (not shown). It is possible to prevent the size from increasing in length so that it can be accommodated in 1 and can be easily configured by using general optical or mirror means for laser processing, except for the feature in this shape.

Further, a notch 1a is formed in the outer surface of the housing on the side where the laser beam deflected from the reflection mirror 4 arranged at the tip of the housing 1 is irradiated to the object to be machined, by cutting out a little in the longitudinal direction. ing. A passage 1c is formed along the longitudinal direction of the housing 1 from the notch 1a so as to be connected to the assist gas pipe so as to extend over a certain length.

The layout relationship of each element in the cross section of the housing 1 is shown in FIGS. 2, 3 and 4, respectively.
As shown in FIG. 2, the optical fiber 2 is supported by the guide member 5. A gas passage 6 is formed inside the guide member 5. The gas passage 6 communicates with the gas hole 6a (see FIG. 3). The reflection mirror 4 is supported by a mirror holder 7 as shown in FIG. Note that reference numeral 8 in FIG. 2 is a fixing screw.

Referring again to FIG. The housing 1 has a screw hole 1 formed on the inner surface of the front end side of the housing 1.
A guide shaft 9 having a threaded portion 9a screwed into d is provided. The guide shaft 9 is provided with three centering wires, for example, a piano wire 11, for centering along a guide groove 10 along the longitudinal direction.

Each piano wire 11 is provided with a bend to be described later so that a small amount of the wire is projected from the outer surface of the guide shaft 9 in the radial direction when the piano wire 11 is attached.

The guide groove 10 and the insertion hole 12a for supporting one end of the piano wire 11 are formed at positions equally divided in the circumferential direction (see FIG. 5). A tip 13 having an insertion hole 12b formed at the same pitch as the insertion hole 12a is provided at the tip of the guide shaft 9, and the other end of the piano wire 11 is inserted into the insertion hole 12b and supported. There is. The tip 13 is fixed to the guide shaft 9 with a bolt 14.

Deflection amounts of the three centering wires are set to the following values based on the wire diameter. The piano wire 11 uses a SWP material, and the wire diameter has a lower limit of 0.6 mm and an upper limit of 1.0 mm in order to obtain a constant tension. The amount of deflection due to this wire diameter is adjusted to 1.0 to 2.0 mm. The operation of the laser welding apparatus configured as described above will be described while describing the procedure for fixing the sleeve to the thin tube by seal welding. This seal weld is, for example, a joint between the thin tube Pi and the sleeve S shown in FIG.

Prior to the seal welding, the inner surface of the thin tube Pi is brushed to remove the attached dirt. Capillary Pi
In order to repair a defect penetrating the wall surface of the thin pipe, for example, a crack C, the defective part is covered with a sleeve S having an outer diameter smaller than the inner diameter of the thin pipe Pi, and two parts (P ₁ , P ₂ ) Weld the end faces of the thin pipe Pi and the sleeve S at one place (P ₃ ) at a total of 3 places.
The sleeve S is expanded from the inside by a suitable expanding device so as to be fitted to the inner surface of the thin tube Pi, and is brought into close contact with the inner surface of the thin tube Pi. Then, the processing head according to the present embodiment of the laser welding apparatus is sent from the front side of the tube sheet Pt to the position shown in the drawing for centering.

When the three piano wires 11 are fed along the inner side of the sleeve S so as to be contracted in the radial direction, the flexed piano wire 11 is displaced to its original position and is brought into close contact with the inner surface of the sleeve S. The machining head is correctly centered.

_First , seal welding is performed in order of the welding point P ₁ and then the welding point P ₂ . The processing gas is introduced into the gas passage 6 in the housing 1, and the assist gas is introduced into the passage 1c to flow around the welding point P ₁ through the notch 5. Laser light from a laser oscillator (not shown) is transmitted to the condensing optical system 3 through the optical fiber 2, further deflected at a substantially right angle by the reflection mirror 4, and irradiated onto the welding point P ₁ .

At the time of this laser light irradiation, the processing head is simultaneously rotated by a rotation driving device (not shown), laser light is irradiated on the circumference, and seal welding is performed along the inner surface of the sleeve S.

Further, the welding point P ₂ can also be moved along with the position of the processing head, and similarly, by irradiating laser light, seal welding can be performed along the inner surface of the sleeve S.

The welding point P ₃ can be subjected to seal welding by TIG welding or laser welding without using the processing head of this embodiment.

An example of the construction conditions of this embodiment is as follows.

Thin tube material = SUS304 (diameter 14 to 17 mm) Sleeve material = SUS304 (inner diameter 10 mm) Processing head length = 1000 mm Centering error = ± 0.1 mm> Laser light = YAG laser Laser output = 0.5 to 3 kw Processing Speed = 100 to 1000 mm / min Set point distance = +2 to -10 mm Collect point distance = 10 to 20 mm Assist gas = Any one of Ar, He and N ₂ Assist gas amount = 10 to 200 l / min Centering error = ± 0.1 mm> As described above, in the laser welding apparatus of the above-described embodiment, the centering mechanism by the piano wire 11 does not occupy a large space, and the processing head is used even when the inner diameter of the sleeve for repair is within 10 mm. Centering can be performed with high accuracy.

The present embodiment is not limited to the above embodiment, but can be implemented in the following modes.

That is, the centering mechanism using the centering wire can be provided at two or more locations including the rear end portion of the housing 1 depending on the length of the processing head. As the centering wire, a hard steel wire, a stainless steel wire, or an oil tempered wire can be used instead of the piano wire. The guide grooves for the centering wire may be formed at positions that are equally divided into six parts (every 60 °) on the circumference, and the centering wires may be attached to the respective guide grooves.

[0033]

As described above, in the present invention, the guide shaft is provided at the front end and / or the rear end of the housing in the longitudinal direction, and at least three guide grooves are formed equally on the circumference thereof. Since the centering wire is attached by giving each guide groove a certain amount of deflection in the radial direction, the centering wire does not occupy a large space and even when the inner diameter of the sleeve is a small diameter within 10 mm, for example. The processing head can be centered with high accuracy.

Therefore, according to the present invention, there is an excellent effect that the heat exchanger, in particular, the repair of a small-diameter thin tube can be easily carried out.

[Brief description of drawings]

FIG. 1 is a sectional view showing a laser welding apparatus according to the present invention.

FIG. 2 is a sectional view taken along the line A ₁ -A _{1 of} FIG.

FIG. 3 is a sectional view taken along the line A ₂ -A _{2 of} FIG.

FIG. 4 is a sectional view taken along the line A ₃ -A _{3 of} FIG.

FIG. 5 is a cross-sectional view taken along the A ₄ -A ₄ line in FIG.

FIG. 6 is a view showing a welding execution state of the device according to the present invention.

[Explanation of symbols]

 1 ... Housing 2 ... Optical fiber 3 ... Condensing optical system 4 ... Reflecting mirror 9 ... Guide shaft 10 ... Guide groove 11 ... Piano wire

Claims (3)

[Claims] 1. An optical fiber, a condensing optical system, and a reflection mirror built in a processing head rotated by a rotation driving mechanism, wherein laser light is transmitted from the optical fiber to the condensing optical system, and further, the reflection is performed. In a laser welding device in which a sleeve member on the inner surface of a thin tube is deflected by a mirror to irradiate, a space is formed by axially penetrating the inside of a housing, and the optical fiber, a condensing optical system, and a reflection mirror are formed. At least one guide shaft is provided at the front and / or rear end in the longitudinal direction of the housing, the guide shaft being accommodated in the space, and at least three guide grooves are equally divided on the circumference of the guide shaft. A laser welding device, wherein the guide groove is formed, and a bending amount of a predetermined amount is given to each of the guide grooves to attach a centering wire. 2. The laser welding device according to claim 1, wherein a notch is formed on a side of the outer surface of the housing which is irradiated with the laser beam deflected by the reflection mirror. 3. The laser welding apparatus according to claim 2, wherein a passage for assist gas, which communicates with the notch and is externally connected to the assist gas pipe, is provided in the housing.