JP2004330304A - WELDING OF BELLOWS USING PULSE MODULATION TYPE Nd-YAG LASER HAVING PEAK ENERGY - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make good welding of a bellows in which the deformation in a welding part is reduced possible by reducing the deformation in the welding part to the full. <P>SOLUTION: In welding equipment for welding the outside diameter of a bellows on which chillings for diaphragm made of circular steel are joined using a pulse modulation type Nd-YAG laser, this equipment is provided with an optical fiber for transmitting a laser beam which is converged with a laser beam converging lens to the object of welding, a welding laser head on which a converging lens for increasing the energy density by converging the laser beam transmitted through the optical fiber on the welding part is attached, a stage where the x-axis, the y-axis and the z-axis are made variable, a tracking part for indicating the welding part by inputting to a monitor through a CCD camera, moving the welding laser head in real time and making welding possible by accurately detecting the welding part, a rotating part of the bellows and the diaphragm for fixing the bellows and the circular bellows diaphragm by interlocking with the tracking part and inducing constant rotation and a supplying means of argon or inert gas for preventing oxidation at welding. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an apparatus for welding a bellows, which is made of a coated steel plate and combined with chilling for a diaphragm, using a pulse modulation type Nd-YAG laser.

Unlike the conventional ordinary CO ₂ laser, CW Nd-YAG laser, ordinary gas vapor laser and laser diode, the pulse-modulated Nd-YAG laser used in the present invention is a pulse-modulated Nd-YAG laser. The power supply device for inputting an electrical pulse signal for the purpose is completely different from that used in the conventional laser, has a high energy density per pulse, and can be induced as a stable output. Can be modulated to vary the energy of the pulses used for welding as needed.

Until now, many TIG weldings, ordinary CW CO ₂ lasers, CW Nd-YAG lasers, laser diodes and the like have been used to weld thin metal plates such as bellows. In the case of TIG welding, the degree of energy focusing is inferior to that of laser welding, a large amount of heat input energy is input, and precise welding is impossible, so high quality welding cannot be expected. Similarly, in the case of the CW laser, since the heat input at the welded part is intense and the welded part is easily deformed, high-quality welding cannot be expected.

  The prior art related to these will be discussed more specifically. First, technologies related to bellows welding are disclosed in Patent Literature 1, Patent Literature 2, and Patent Literature 3 below. All of these describe a bellows welding apparatus that performs bellows welding using a conventional laser beam. That is, in all of these inventions, when thin metal plates such as bellows are welded, the heat input energy at the welding site and the thin metal that can be changed by the heat input energy are essential considerations. No consideration is given to the deformation of the plate. Moreover, even when welding along the welding site, it does not include technical content for elaborate welding while tracking in real time based on video signals, and it is said that elaborate and good welding cannot be performed. There was a problem.

US Pat. No. 5,478,983 US Pat. No. 5,410,123 Korean Published Patent Publication 2001-0045143

  The present invention recognizes the problems of the conventional bellows welding as described above, and uses the pulse modulation type Nd− to weld the outer diameter of the bellows to which the chilling for the diaphragm made of the circular steel material coated with the film is coupled. When performing using a YAG laser, the focus of the peak type pulse energy, which is important in the process of bellows welding composed of a thin metal plate, is appropriately increased to supply low penetration energy to the welding site. It is possible to achieve good bellows welding with less deformation of the welded part by maximally reducing the deformation of the weld.

  That is, the object of the present invention is to recognize the problems of the TIG welding and the bellows welding using a normal laser and appropriately set the peak value at the start of the pulse input to the laser using the pulse modulation type YAG laser. It is intended to achieve high-quality bellows welding without deforming the welded part by reducing the heat input energy of the welded part while increasing the degree of convergence of the initial energy to the welded part of the thin metal plate.

  Another object of the present invention is to provide a matte black coating on the circular steel diaphragm chilling when welding the bellows diaphragm and bellows, thereby reducing the reflection of light generated from the illumination device and reducing the reflection of light from the CCD (charge coupled device). ) To obtain a good video signal from the camera and to move along the welding site in real time based on the good video signal, so that it is possible to prevent the malfunction of the laser head and to perform elaborate bellows welding. .

  The present invention uses a pulse-modulated Nd-YAG laser for the outer diameter of a bellows to which a chilling for a diaphragm (see FIG. 5) made of a circular steel material (SUS spring) coated with a matte surface is coupled. Relates to a welding apparatus. In this apparatus, Nd-YAG used for laser generation is an abbreviation of Neodymium-yttrium allumium garnnet, Nd is a doping substance, and YAG is a host. When the glass rod is manufactured, Nd has a specific gravity of about 1% of the host. The Nd-YAG bar has a radius similar to that of a glass bar having a radius of 6 to 10 mm and a length of about 10 mm. Position one or two lamps in the middle of an elliptical cavity with one or two focal points and position one or two lamps side by side or Nd− between them Position the YAG bar. At this time, each position of the lamp and the Nd-YAG rod is structured so that the light generated from the lamp can be effectively transmitted to the Nd-YAG rod by using the focus of the cavity to maximize its efficiency. To do. If power is supplied to the lamp, light generated from the lamp is effectively transmitted to the Nd-YAG rod, and Nd ions are excited to induce generation of a laser beam. At this time, the light generated from the lamp generates various wavelengths, but Nd-YAG that has absorbed the light generated from the lamp has the following characteristics when the Nd element excited by the light generated from the lamp falls to the ground state. Light having a constant wavelength of 06 μm is generated. At this time, the energy value of the generated laser beam has a close relationship with the electrical signal supplied to the flash lamp.

  In order to obtain the laser output for bellows welding desired by the user for the pulse modulation type Nd-YAG laser, the pulse signal supplied to the flash lamp has the same or similar form to the output of energy desired by the user. It must be supplied as a signal. The present invention uses a transistor (IGBT, Insulated Gate Bipolar Transistor) capable of switching a pulse signal from a normal three-phase 220V power source to a switching mode power supply and high speed to obtain a laser output suitable for bellows welding. A thin metal plate such as a bellows can be finely welded without significant deformation due to heat input, and is initially supplied to the lamp as a pulse signal having an appropriate peak value (see FIG. 2). Pulse output, frequency and pulse width can be controlled by opening the gate (turning the transistor on / off) at a desired time interval using the IGBT from the electrical energy obtained from the switching mode power supply. Is performed by controlling the width of the pulse signal supplied to turn on / off the transistor (IGBT) with a microcomputer, and the maximum pulse modulation frequency can be modulated up to 300 Hz depending on the welding speed and the desired output energy. is there.

  The pulse signal waveform that must be supplied to the pulse modulation type Nd-YAG laser in order to weld a thin metal plate such as a bellows in an elaborate and good state is as shown in FIG. , The peak value at the beginning of the pulse is appropriately increased to inject a small amount of heat input energy instantaneously, and the energy at the back of the pulse is reduced to prevent continuous heat input to the weld. This is an optimum pulse signal form that can prevent the deformation of a thin metal plate and perform high-quality bellows welding. That is, since the material of the bellows is a thin metal plate, if a large amount of energy is continuously input, it becomes impossible to perform high-quality elaborate welding by thermal deformation of the metal substance. Therefore, in order to instantaneously increase the energy absorption into the thin metal plate, an appropriately high pulse peak output capable of increasing the temperature of the metal surface before the heat is conducted to the metal is required. The pulse signal used in the present invention increases the laser light absorption coefficient by supplying a suitably high energy to the pulse modulation type Nd-YAG laser at the start portion, and high-quality elaborate welding with a small amount of heat input energy. To be able to.

  In this connection, in FIG. 3, if the change of the absorption coefficient (coupling coefficient) due to the temperature change of the metal is observed, the laser light absorbance is usually not so high in the metal at normal temperature, but the temperature of the metal surface increases. As a result, it can be seen that the laser light absorbance is greatly increased.

  The laser beam generated from the pulse-modulated Nd-YAG laser is transmitted through an optical fiber, and the laser beam is focused by a light focusing lens before being transmitted to a final target welding object. It is transmitted inside the fiber. The optical fiber used at this time was selected from the wavelength of a pulse modulation type Nd-YAG laser and made of a material with little loss (FQSI type, diameter 400 μm, length 10 m).

  The laser beam transmitted through the optical fiber is welded to obtain an optical part for focusing the laser beam, a CCD camera, and a good video signal in order to enable precise and good bellows laser welding. A laser welding head is constituted by an illumination unit for illuminating the laser beam.

  An optical unit that focuses the laser beam transmitted through the optical fiber as a light size suitable for bellows welding includes a mirror used to change the direction of the beam transmitted through the optical fiber, The laser beam is changed and focused in a desired direction using a light focusing lens to focus the light, and high-density energy is transmitted to the welding site. The CCD camera is located near the laser welding head. It is attached and the welding part is observed and the image signal of the welding part is received by the CCD sensor and displayed on the monitor. The illumination unit observes the video signal of the welding part of the welding object more vividly on the monitor. It is something that can be done. In the bellows welding apparatus, an object to be welded that appears by illumination of the illumination unit is received by a CCD camera and displayed on a monitor on the basis of a video signal (image). The X-axis servo motor is varied in real time along the connecting portion of the X-axis, and the welding is performed precisely. The XY table controller adopted in the present invention is driven by two AC servo motors and can be moved up to 5/10000 mm, and is displayed on the monitor in cooperation with the monitor that receives and displays the video signal. By moving in real time along the welded part, it plays a role of enabling elaborate welding.

  The rotating body of the welding object can be rotated at a constant speed by fixing the bellows diaphragm and bellows to a jig (see Fig. 5), but if necessary, it can be rotated in the reverse or forward direction. obtain. In connection with the operation of the rotating body of the welding object, as can be seen from FIG. 4, welding conditions can be input via a monitor. Of the variables input on the monitor shown in the figure, the maximum speed is the speed at which the rotating body rotates and is displayed in rpm. The initial speed is the number of pulses emitted by the laser per second. Displayed in pps, which are also related to the power of the welding laser. The acceleration time is the time required to reach the maximum speed from the stop state, and the deceleration time is the time required to reach the stop state from the maximum speed.

  The variables that can be input from the monitor to achieve better laser welding are the rotation speed of the welding object, the number of pulses generated per second (laser output), acceleration time, deceleration time, video It is set by the precision of tracking when automatically tracking along the welding site when welding along the signal, and by controlling these variables well, it is possible to achieve elaborate and good bellows welding it can. That is, welding is performed while tracking in real time using the image signal of the welding part input to the monitor by the CCD camera, and the rotating body that fixes and rotates the bellows and the bellows diaphragm by one microprocessor, and tracking The AC servo motor that moves the XY drive shaft (laser head support) used at the time is integrated with each other so that optimum bellows welding can be performed.

  In connection with the bellows welding, the inert gas injection part is used during the welding period in order to prevent oxidation of the welded part and inflow of impurities in the usual manner and to achieve better welding. This is a device for continuously injecting an inert gas into the welding site.

  The chilling for bellows diaphragm used in connection with the present invention uses a steel wire (material; SUS) that is mattely blackened. Here, the reason for the coating treatment is to prevent reflection of light emitted from illuminations provided on both sides of the laser head, obtain a more accurate video signal, and induce more precise tracking.

  FIG. 5 shows a shaft, a stopper, a sleeve and the like for fixing the bellows diaphragm and the chilling for the diaphragm.

  The effect expected by the present invention is to recognize the problems of the TIG welding and the bellows welding using a normal laser, and give a peak value at the initial stage of the pulse by using a pulse modulation type YAG laser. The aim is to achieve high-quality bellows welding without increasing the degree of convergence and reducing the heat input energy of the welded part without deformation of the welded part.

  Another effect of the present invention is that when the bellows diaphragm and bellows are welded, the round bellows diaphragm made of a round steel material is coated with a matte black, reducing the light generated from the illumination device, and improving the quality of the CCD camera. The purpose is to obtain a video signal and to perform precise welding by tracking a welding portion in real time from the high-quality video signal.

  As an embodiment related to the present invention, a pulse modulation type Nd-YAG laser power supply circuit includes a switching mode power supply and high-speed switching means, and is supplied to a flash lamp as shown in FIG. A pulse signal having a peak value is supplied as an input signal of a flash lamp of a pulse modulation type Nd-YAG laser suitable for bellows welding which is a thin metal material. It is generated during the process of converting the light of the flash lamp into a laser beam by supplying an inert gas in order to prevent oxidation by injecting into the welding site during the bellows welding and to enable good quality welding. The cooling device is operated to cool the heat.

  Based on the principle of FIG. 2 and FIG. 3, the peak value at the beginning of the pulse is appropriately increased to inject a small amount of heat input energy instantaneously, and the energy is decreased at the rear portion of the pulse, so An optimal electrical pulse signal for preventing the material from being deformed by continuous heat input and achieving high-quality bellows welding is supplied to the pulse modulation type Nd-YAG laser. That is, since the material of the bellows is a thin metal plate, if a large amount of energy is continuously input, the heat input energy increases and high-quality elaborate welding cannot be performed. Increasing energy absorption into the interior of the plate requires a reasonably high peak power that can raise the temperature before heat is conducted to the metal. The pulse-modulated Nd-YAG laser that supplies a suitably high energy to the signal start portion used in the present invention instantaneously increases the laser light absorption coefficient, and a high-quality and sophisticated bellows welding with a small amount of heat input energy. To be able to.

  In other words, the pulse-modulated Nd-YAG laser used in the present invention minimizes the deformation of the weld due to continuous heat input by using a peak pulse and a small amount of heat input energy. Welding with Rose can be achieved.

  Also, a pulse modulation type Nd-YAG laser and a welding head are attached to the laser head, and a video signal of a welding part is transmitted to a monitor via a camera, and welding is performed along the welding part based on the transmitted video signal of the welding part The tracking means and the microprocessor that can be used to rotate the welding object rotation speed, the number of pulses generated per second (laser output) to generate the laser beam, the acceleration time and deceleration time of the servo motor, etc. Operates in conjunction.

  Specific operation steps of bellows welding using a laser will be described.

  First, the laser welding system is roughly divided into a pulse modulation type Nd-YAG laser main body and a processing system, and the processing system is composed of a rotating body on which a welding object is fixed, an optical fiber, and an optical unit. A tracking unit to which an AC servomotor is attached so that the welding head is fixed and the XY table can be moved to the left and right.

  In the bellows laser welding system configured as described above, the rotation width of the welding object, the AC servo motor that drives the XY axis, and the pulse width and pulse size of the pulse modulation type Nd-YAG laser are mutually determined. Link them together and control them all with a computer program. Bellows welding controlled by a computer program will be specifically described step by step (see FIG. 4).

  A) First, power is supplied to the pulse modulation type Nd-YAG laser, the rotating body of the welding object, and the AC servo motor that drives the XY axes, the illumination device, the monitor, and the cooling device.

  B) When power is supplied, the image signal of the welded part on the monitor is displayed via the CCD camera, and movement to a desired position is achieved by clicking with the mouse.

  C) After moving to a desired position, the number and interval of welding are set by inputting the number and interval of machining from machining settings, and when the machining button is clicked, welding is automatically performed.

  D) More specifically, it is possible to perform movement setting, origin search, laser setting, center display setting, screen ratio setting, processing setting, and the like from the setting menu.

  When the movement setting is selected, the speed and position of the rotary shaft and the welding head transfer shaft can be set. When the position is moved in the horizontal direction, a numerical value of the distance to be moved is input and the movement button is pressed, and the position is moved to a predetermined position. By selecting “forward” or “reverse” as the rotation direction, the rotating body can be moved to a desired direction.

  For the moving speed, pressing the “Speed” button displays a window where the speed can be set, and the initial speed is displayed as pps (pulses per second), which is 1 / of the maximum speed. About 10 is preferable. The maximum speed is the maximum speed at the time of movement, and is expressed in rpm, which is a value valid only for the rotation axis. The acceleration time represents the time required to reach the maximum speed from the stop state, and the deceleration time represents the time required to reach the stop state from the maximum speed. In order to achieve good welding in the laser deceleration time and acceleration time, it is preferable to set so as to overlap and weld approximately 10 degrees.

  The auto tracking function adjusts with the fine adjustment speed and ratio. The fine adjustment speed determines the lateral movement speed during welding, and it is usually preferable to set a small value at a high speed and a large value at a low speed.

  E) Origin search is a function that searches the origin where the horizontal axis has already been set.

  F) In the laser settings, the laser power, frequency, intensity and processing time can be set. The high set sets the maximum power of the laser, and the low set sets the minimum power of the laser. The ratio of the high set and the low set varies depending on the intensity of the laser. That is, the high set lasts longer if the intensity of the laser is greater, and the lower set lasts longer if the intensity decreases. The processing time is automatically set if the rotational speed of the position movement is corrected.

  G) The center display setting allows the laser processing position to be confirmed.

  H) Screen ratio setting sets the ratio between the distance visible from the screen and the actual distance.

  B) When the machining button is pressed, the welding process is performed according to the welding conditions already set in the menu while moving left and right along the welding line at the number and interval set in “machining setting”.

  N) The machining setting enables the number of machining and the machining interval to be set for continuous machining. When the number of machining and the machining interval are input, the machine is moved to the first position and the “machining” button is pressed to perform machining. When the “start position” or “standby position” button is pressed, it moves to the position given here. When the processing angle is further increased, the processing is further rotated, and the start portion and the end portion are slightly overlapped (rotated a little) to be processed.

It is the schematic of the bellows welding apparatus using the pulse modulation type Nd-YAG laser which has a peak energy. It is a figure which shows the output waveform of the pulse signal input into the flash lamp of the pulse modulation type Nd-YAG laser which has a peak energy. It is a figure which shows the laser beam absorptivity by a raise of metal surface temperature. It is a figure which shows the input variable displayed on a monitor at the time of bellows welding. It is a figure which shows the fixing | fixed part of a bellows and a circular bellows diaphragm.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pulse modulation type Nd-YAG laser 2 Laser power supply part 3 Laser cooling device 4 Laser welding head 5 XY table (with AC servo motor)
6 Optical fiber for laser transmission 7 Microprocessor 8 Monitor 9 Welding object 10 Rotating body (motor)
DESCRIPTION OF SYMBOLS 11 Illumination means 12 Camera 13 Inert gas input part 14 Welding condition input part 15 Seam tracker
(1) Shaft (2) Stopper (3) Stopper (4) Collar
(5) Sleeve (6) Bellows

Claims (5)

In a welding apparatus having an outer diameter of a bellows to which a chilling for a diaphragm made of a circular steel material is coupled using a pulse modulation type Nd-YAG laser having a peak energy,
A power supply unit for a pulse modulation type Nd-YAG laser having a switching mode power supply and high-speed switching means for generating a pulse having a waveform desired by the user with a stable output from the pulse modulation type Nd-YAG laser. When,
A pulse-modulated laser that is supplied with a pulse signal having an optimum peak value for welding a thin metal plate and generates a laser beam having a peak energy based on an electric signal stably supplied from the power supply unit. When,
A focusing lens for focusing the laser beam for transmitting the laser beam generated from the pulse modulation type laser generating the peak pulse energy through an optical fiber;
An optical fiber that transmits a laser beam focused by the laser beam focusing lens to a welding object;
A laser head for welding to which a focusing lens for focusing the laser beam transmitted through the optical fiber on the welding site to increase the energy density is attached;
A stage capable of varying the x-axis, y-axis, and z-axis for positioning a welding laser head to which the laser beam focusing lens is attached in a direction perpendicular to a welding object or a desired angle;
Illumination means that is attached to both sides of the stage to which the laser head is attached, and that illuminates the welding site so as to be easily observed by a CCD camera;
The welding site illuminated by the illumination means is input to a monitor via a CCD camera and displayed, and the welding laser head is moved in real time in conjunction with the displacement of the welding site based on the input video signal, A tracking unit that accurately locates the welding site and enables welding;
In conjunction with the tracking portion, the bellows and the circular bellows diaphragm are fixed, and a rotating portion of an excellent bellows and bellows diaphragm that induces constant rotation;
A pulse modulation type Nd− having a stable output, characterized by comprising means for supplying argon or an inert gas to prevent oxidation and achieve clean welding during welding of the bellows and the bellows diaphragm. Bellows welding equipment combined with bellows diaphragm using YAG laser. The bellows diaphragm chilling is a matte black coating on a circular steel wire to reduce reflection by illumination and obtain a more accurate video signal so that the welding site can be accurately tracked based on the video signal. The bellows welding apparatus according to claim 1, wherein a bellows diaphragm using a pulse-modulated Nd-YAG laser having a stable output according to claim 1 is coupled. The bellows diaphragm chilling is composed of a SUS material circular steel wire, and a bellows diaphragm using a pulse-modulated Nd-YAG laser having a stable output according to claim 1 is combined. The bellows welding apparatus according to claim 1. The electrical signal supplied to the flash lamp is characterized in that, among each pulse signal, a peak value is given at the initial stage of the pulse to increase the energy density and input to the flash lamp to increase the initial energy of the laser beam. 2. A bellows welding apparatus according to claim 1, wherein a bellows diaphragm using the pulse modulation type Nd-YAG laser having a stable output according to claim 1 is coupled. The pulse modulation type Nd- having stable output according to claim 1, wherein the pulse modulation type laser modulates the number of pulses generated per second and the pulse width to change the output energy. 2. A bellows welding apparatus according to claim 1, wherein a bellows diaphragm using a YAG laser is coupled.

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