JP3931817B2 - Laser welding method and welding apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a laser welding method and a welding apparatus for executing the method, and more particularly to the laser welding method and apparatus suitable for welding and bonding a plurality of synthetic resin materials by laser light.
[0002]
[Prior art]
As one means for welding and bonding a plurality of resin materials, a resin material that transmits almost all of the laser light and a resin material that absorbs the laser light and generates heat are held in contact with each other, such as a YAG laser. The laser beam is irradiated to a part of the absorbent resin material through the transparent resin material, and the irradiated portion of the absorbent resin material absorbs the energy of the laser beam to generate heat and melt, By applying a part of the heat to the part of the permeable resin material that is in contact with the irradiated part and raising the temperature of the part to melt and fuse it, these parts are cooled and solidified. A welding method for bonding a plurality of resin materials is known.
[0003]
Transparent resin materials that are one of a plurality of resin materials that can be bonded by this welding method include PP (polypropylene), PC (polycarbonate), ABS (acrylonitrile-butadiene-styrene copolymer), PA (polyamide). Various resin materials such as PBT (polybutylene terephthalate) and PPS (polyphenylene sulfide) are used. In addition, there is an example in which PBT, PPS, or the like is applied to a sensor or an actuator in order to satisfy hydrolysis resistance and dimensional accuracy.
[0004]
With regard to welding of resin materials that are poorly permeable to laser light, in the conventional technology, by increasing the amount of transmission by changing the conditions, controlling the joint, changing the material, molding conditions, annealing (heat treatment) time, etc. The above has ensured stable quality. However, there is a need for high-performance products in recent years, such as the fact that the resin material must be colored in terms of design, etc., and that high-temperature annealing must be performed in terms of dimensional shrinkage resistance or the environment. However, since these techniques may not be able to cope with them sufficiently, there is an urgent need to develop a highly reliable welding technique for resin materials with extremely poor permeability.
[0005]
In order to prevent poor welding that occurs when welding a resin material that does not transmit laser light sufficiently and a resin material that does not transmit laser light, even a resin material that is not sufficiently transparent using a high-power laser oscillator. When a laser beam that is so strong as to pass through is irradiated, an excessive temperature rise occurs in a portion other than the welded portion and the material melts, resulting in a derivative problem that causes trouble. Further, when the process window is small, there is a concern that the resin material is not sufficiently welded by the output of the laser beam set based on the molding conditions and annealing conditions.
[0006]
[Problems to be solved by the invention]
In view of the above-mentioned problems in the prior art, the present invention solves these problems by novel means, and in general resin materials including not only light-transmitting resin materials but also those having poor transmittance. In carrying out welding with laser light, the purpose is to further improve the quality of the welded part in order to meet the needs of highly functional products in recent years.
[0007]
[Means for Solving the Problems]
According to the present invention, as means for solving this problem, the laser welding method described in claims 1 and 3 of the claims and the laser welding apparatus described in claim 8 for executing the laser welding method are provided. provide.
[0008]
Since the laser welding property of the resin material is considered to reach the maximum level by giving the optimum laser output for the material, the laser welding method according to claim 1 or 3 is used for welding processing. Before irradiating the laser beam, without measuring the portion to be welded, the light transmittance of the light- transmitting material in this welded portion is directly measured in advance, By supplying information to the laser welding machine in units of lots or individual units, the output of the laser beam to be irradiated is controlled so as to change corresponding to the light transmittance of the material.
[0010]
The laser welding method for a plurality of materials according to the present invention can be suitably executed by a laser welding apparatus configured so that steps having substantially the same contents can be sequentially executed.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. FIG. 1 is a block diagram showing a system configuration as a first embodiment of a welding apparatus for executing the laser welding method of the present invention. In FIG. 1, reference numeral 1 denotes a laser light source such as a YAG laser oscillator. The laser light 3 generated in the laser light source 1 is focused by passing through an optical system 2 configured by combining lenses or the like, directed in a predetermined direction, and irradiated to a portion to be welded of a work material. The material to be processed includes a transmitting material 4 made of a resin material that generally transmits the laser light 3 and an absorbing material 5 made of an opaque resin material that is in contact with the laser light 3 and absorbs the laser light 3.
[0012]
The above-described configuration of the laser welding apparatus of the first embodiment is the same as that of the conventional laser welding apparatus, and the laser beam 3 generated in the laser light source 1 is transmitted through the transmission material 4 from the optical system 2 and is opaque. The absorbing material 5 is irradiated and absorbed by the absorbing material 5 to generate heat and melt the irradiated portion of the absorbing material 5, and part of the heat of the transmitting material 4 in contact with the irradiated portion of the absorbing material 5. Also transmitted to the part and melts that part of the permeable material 4 so that the molten parts of the permeable material 4 and the absorbent material 5 are fused together, and when these parts are cooled, the permeable material 4 and the absorbent material 5 Weld and bond. However, this alone causes various problems as described above, and depending on the transmittance of the permeable material 4 and the nature of the absorbent material 5, there is a possibility that troubles may occur due to insufficient welding or excessive melting of the work material.
[0013]
As one of the features of the first embodiment, there is provided an arithmetic unit 6 including a microcomputer that can act on the laser light source 1 and control its output in real time. In addition, it may not be necessary when the laser light source 1 and the optical system 2 are structurally integrated, but when they are separated as shown in FIG. A flexible optical fiber 7 is provided to connect the gaps and transmit laser light. When the optical fiber 7 is provided, the degree of freedom in the relative positional relationship between the laser light source 1 and the optical system 2 is increased. In the case of the first embodiment, the laser light source 1 and the arithmetic unit 6 are electrically connected by a conducting wire or the like.
[0014]
Another feature of the laser welding apparatus according to the first embodiment is that the transmission material 4 of the material to be processed has a portion having the same thickness and transmittance as the welding portion other than the portion to be welded next, or Proximity to a separate model of the same shape as the transmission material 4 which is made of the same material as the transmission material 4 and is supported at a required distance from the work material, and measures the amount of light transmitted through them. A detector 8 is provided. An electrical signal output from the detector 8 is input to the above-described arithmetic unit 6 through a conducting wire. Further, a light source 9 for measurement is provided on the opposite side of the detector 8 with respect to the transmission material 4 (or its model), and the light beam 11 emitted from the light source 9 is focused and the detector 8 is passed through the transmission material 4. An optical system 10 including a lens or the like that is incident on the lens is provided.
[0015]
As the light source 9 for measurement, an oscillator of laser light similar to the laser light source 1 for welding processing but smaller than that can be used, and various light sources such as a halogen light source can be used. it can. Of course, the laser light source 1 for welding can be used as the light source 9 for measurement. The light beam 11 generated by the measurement light source 9 is preferably a laser beam having the same wavelength as that of the laser beam 3 generated by the welding laser beam source 1, but the laser beam has the same wavelength. It doesn't mean it has to be. Also in this case, the measurement light source 9 and its optical system 10 are separated and connected by a flexible optical fiber 12, but the light source 9 and the optical system 10 are integrated. Of course, the optical fiber 12 may be omitted.
[0016]
In the laser welding apparatus of the first embodiment, the transmission material 4 and the absorption material 5 of the work material are set at predetermined positions by a jig or the like (not shown), and both surfaces of the portion where the transmission processing of the transmission material 4 is not performed. Are positioned so that the measurement optical system 10 and the detector 8 face each other. However, as described above, the measurement system including the light source 9, the optical system 10, and the detector 8 with the model manufactured from the same resin material as that of the transmission material 4 is used as the laser light source 1 and the optical system 2 for welding processing. Alternatively, it may be separately provided at a position as far away as necessary from the system of the main body composed of the transmission material 4 and the absorbent material 5 of the work material.
[0017]
Since the laser welding apparatus of the first embodiment is configured as described above, the light beam 11 from the measurement light source 9 is irradiated to the transmission material 4 (or its model, the same applies hereinafter) before performing the laser welding. Then, the amount of the light beam 11 that has passed through the transmission material 4 is measured by the detector 8, and the signal is input to the arithmetic device 6 to calculate the transmittance of the transmission material 4. After that, laser welding is performed. First, an output corresponding to the magnitude of the transmittance calculated as a measurement result is set in the laser light source 1, and the set strength is set from the laser light source 1 through the optical system 2. Then, the laser beam 3 is irradiated to the workpiece material composed of the transmitting material 4 and the absorbing material 5.
[0018]
As a result, the intensity of the laser beam 3 irradiated to the welded portion changes to a magnitude that immediately corresponds to the transmittance of the transmitting material 4 that is welded at that time. That is, when the transmittance is high, the intensity of the laser beam 3 is made relatively weak, while when the transmittance is low, the intensity of the laser beam 3 is increased so that the energy of the excess and deficiency is welded. Since the heat is applied to the surface of the absorbent material 5, an appropriate amount of heat is generated on the surface of the absorbent material 5. Further, it is possible to prevent a trouble caused by a melted portion in the depth and perform high-quality laser welding.
[0019]
In addition, it has the same shape as the permeation | transmission material 4 currently supported in a part away from the original permeation | transmission material 4 in a part of the permeation | transmission material 4 in the position a little away from the welding part of the permeation | transmission material 4 and the absorption material 5. When estimating the transmittance of the transmission material 4 in the welded portion by measuring the transmittance of the corresponding portion in the model, the transmittance of the position corresponding to the welded portion at that time is continuously measured (that is, the transmittance). It is possible to control the output of the laser light source 1 to change in real time. For example, the shape of the transmission material 4 and the model of the measurement part is complicated, When the light beam 11 is scattered, the transmittance of a representative portion is measured, the average value of the transmittance is calculated, and the output corresponding to the average value is set in the laser light source 1 to output the light. Control It may be.
[0020]
Needless to say, as a more basic method, all the welded portions of the permeable material 4 to be actually welded are traced in advance, and the in-plane distribution of transmittance is continuously measured. It is also possible to carry out laser welding according to the data after storing in the memory. When a large number of work materials having the same shape are repeatedly welded as in a normal welding process, first, the transmittance of the permeation material 4 of the work material is measured only once for the entire circumference of the welded portion. During the processing of the same lot, this method is the most efficient because it is only necessary to repeat the output control of the laser light source 1 with the same pattern by the arithmetic unit 6.
[0021]
In any case, the transmittance is measured for the transmission material 4 itself or a model of the transmission material 4 that is a part of the material to be processed, and then laser welding is performed. It is efficient to do it in units. However, because the shape of the transmission material 4 of the workpiece material is complicated and the thickness is not uniform, or the distribution of crystals inside the material is not uniform, and the transmittance varies for each part of the workpiece material. In addition, when the distribution of the transmittance of the transmission material 4 cannot be stored in the memory and the output control cannot be routinely performed, the transmission that changes every moment using a system with excellent tact time and controllability. The transmittance of each part of the material 4 may be measured individually and controlled so that the output of the laser light source 1 changes in real time according to the measurement result.
[0022]
In the arithmetic device 6, in order to calculate the output of the laser light source 1 from the transmittance detected by the detector 8, for example, arithmetic processing as shown in the flowchart of FIG. 2 is performed. That is, the relationship between the transmittance of the transmission material 4 and the output of the laser light source 1 is a map having the contents as shown in FIG. 3 showing the relationship between the transmittance x and the laser output W, or a functional expression W = f (x).
And is set in the memory in the arithmetic unit 6. Then, the transmittance is measured in step 201, and the obtained value is applied to the definition in step 202, whereby the optimum value of the output of the laser light source 1 is calculated. Since a general laser welding apparatus has an analog input system, the laser light source 1 generates a laser output having a magnitude corresponding to a voltage input as a command value. Accordingly, in step 203, the voltage waveform of the command value is changed to change the output of the laser light source 1. Regarding the output change pattern, it is also possible to perform multi-stage waveform control based on the result of measuring the change in transmittance over the entire circumference of the transmission material 4 along the line indicating the welding order.
[0023]
FIG. 4 illustrates a flowchart of a processing procedure when performing real-time processing. The difference between the process of FIG. 4 and the process of FIG. 2 is that step 402 is provided in FIG. 4. This process, for example, has a complicated change in the thickness of the permeable material 4 and the distribution of crystals in the welded portion. By setting an appropriate threshold value for the transmittance when the measured transmittance changes as illustrated in FIG. 5 and comparing the detected transmittance with those threshold values, When the transmittance is larger than the threshold value, the process proceeds to step 403 to change the output of the laser light source 1, but when the transmittance is smaller than the threshold value, the output is maintained, and the process returns to step 401 to repeat the transmittance measurement. Thus, the output of the laser light source 1 is controlled. As a result, as illustrated in FIG. 6, the output of the laser light source 1 increases or decreases.
[0024]
Although the laser light output control by measuring the transmittance of the transmission material 4 has been described above, according to this technique or algorithm, it is possible to construct a feedback control system from the viewpoint of quality assurance of welding. In other words, the quality indicators in laser welding include the welded area and the number of weld defects such as voids or delamination. These indicators are measured by various sensors, and the laser output and Control other parameters to achieve good laser welding. The various sensors mentioned here are a radiation thermometer that can measure the temperature in the vicinity of the welded portion, a gap sensor that can measure the gap between the welded portions, and the like.
[0025]
FIG. 7 shows a system capable of performing quality feedback control using a radiation thermometer 13 as a second embodiment of the welding apparatus for executing the laser welding method of the present invention. In the figure, 13 is a radiation thermometer that measures the temperature of the portion irradiated with the laser beam, that is, the welding temperature, as one of the factors indicating the quality of welding, and 14 is a signal detected by the radiation thermometer 13. It is an amplifier that amplifies. The reference numerals of the other parts are the same as those in the first embodiment shown in FIG.
[0026]
In the control system of the second embodiment, the same control procedure as that shown in FIG. 4 is used. In this case, in the step corresponding to step 401 in FIG. The welding temperature of the portion irradiated with the laser light is measured by the radiation thermometer 13. Then, in a step corresponding to step 402, the temperature measured by the radiation thermometer 13 is compared with one or more threshold values set for the temperature, and the laser output is changed when the measured temperature exceeds the threshold value On the other hand, control is performed such that the laser output is maintained when it does not exceed.
[0027]
FIG. 8 illustrates a more specific simulation. Since this is a simulation of control, FIG. 8 does not show the actual situation of feedback control, but considers the response to all possible changes in the welding temperature and sets the threshold value used for the temperature control. Is. Actually, as a result of the control included in the method of the present invention, such a large fluctuation range of the temperature does not occur, so that the change width of the control voltage becomes smaller.
[0028]
In the example shown in FIG. 8, four-stage threshold values indicated by broken lines are set, and the initial value of the control voltage input to the laser light source 1 as the output of the arithmetic unit 6 is 2.5V. The initial output of 2.5V is maintained within the range where the measured temperature is 180 ° C. or more of the lower limit 1 and does not exceed the threshold 230 ° C. of the upper limit 1, but when the temperature exceeds 230 ° C. of the upper limit 1, the control voltage Is 1V. Further, when the temperature rises beyond the upper limit 2 threshold of 250 ° C., the control voltage is lowered to 0.5V. As a result, the output of the laser light source 1 is lowered, so that the irradiated laser light is weakened, and the temperature measured at the welded portion is also lowered.
[0029]
The control voltage is returned to 1 V when the temperature of the measured welded portion falls to the upper limit 2 threshold value of 250 ° C. or lower and the upper limit 1 threshold value of 230 ° C. or higher. Increase the voltage to 2.5V. If the temperature of the welded portion further decreases and falls below the lower limit 1 threshold value of 180 ° C., the control voltage is set to 3.5V. If the temperature continues to decrease and falls below the lower limit 2 threshold of 110 ° C., the control voltage is increased to 4. As a result, the temperature of the welded portion also increases. Thereafter, by repeating the same correspondence, the welding temperature is controlled to converge within a narrow range of fluctuation and to become a substantially constant value.
[0030]
By performing such control, the laser welding method and apparatus of the second embodiment can achieve the same effects as those of the first embodiment. As a result, there is no variation in welding quality and the outflow of defective products can be prevented. Not only can the occurrence of defective products be prevented.
[0031]
In the present invention, not all of the plurality of materials to be processed are made of resin materials as in the above-described embodiment, and the transmission material 4 is made of an inorganic material such as transparent glass, or the absorbent material 5. When an opaque inorganic material such as metal or ceramics is used, both the transmissive material 4 and the absorbent material 5 may be other than the resin material.
[Brief description of the drawings]
FIG. 1 is a system configuration diagram showing a first embodiment of a laser welding apparatus according to the present invention.
FIG. 2 is a flowchart showing a basic control procedure.
FIG. 3 is a map that defines the relationship between transmittance and the output of a laser light source.
FIG. 4 is a flowchart showing a control procedure corresponding to a varying transmittance.
FIG. 5 is a diagram illustrating results of measuring varying transmittance.
FIG. 6 is a diagram showing a change in output of a laser light source corresponding to a varying transmittance.
FIG. 7 is a system configuration diagram showing a second embodiment of the laser welding apparatus according to the present invention.
FIG. 8 is a diagram showing a simulation regarding the second embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Laser light source for welding processes 2, 10 ... Optical system 3 ... Laser beam for welding processes 4 ... Transmission material 5 ... Absorbing material 6 ... Arithmetic device 7, 12 ... Optical fiber 8 ... Photo detector 9 ... Light source for measurement 11 ... Light beam for measurement 13 ... Radiation thermometer 14 ... Amplifier

Claims (8)

A step of adhering and supporting a light-transmitting material and a light-absorbing material to be welded thereto;
Before irradiating the laser beam for welding processing, the light beam for measurement is irradiated to directly measure the light transmittance of the light-transmitting material in the welding portion without welding the portion to be welded. Measuring, and
Controlling the output of the laser light source for welding processing so as to increase or decrease according to the measured light transmittance of the light transmissive material;
Irradiating a welding laser beam from the welding laser light source to the portion to be welded, and transmitting the light-transmitting material to generate heat in the irradiated portion of the light-absorbing material When,
A step of fusing at least one of the light-absorbing material and the light-transmitting material with heat generated in the irradiated portion and then cooling and solidifying the material to weld them;
Laser welding method for a plurality of materials consisting of   2. The welding process according to claim 1, wherein a threshold value is set for the light transmittance of the light-transmitting material measured by irradiating the measurement light beam, and the measured light transmittance exceeds the threshold value for the welding process. A laser welding method for a plurality of materials, wherein the output of the laser light source is changed while the output of the laser light source for welding processing is maintained when the measured light transmittance does not exceed the threshold value. A laser beam generated by a laser light source is focused and irradiated to a portion to be welded of the work material, and the work material is in contact with the transmissive material and a transmissive material made of a material that transmits the laser light. A laser welding method comprising: an absorber made of a material that absorbs laser light; and performing laser welding in which a welded portion of the transmission material and the absorber is bonded to each other,
An arithmetic unit capable of acting on the laser light source to control increase / decrease in its output;
A detector that measures the amount of light that passes through the measurement material related to the transmission material of the material to be processed, and inputs an electrical output signal to the arithmetic device;
A measurement light source is provided opposite to the detector, and an optical system for converging a light beam emitted from the measurement light source and making it incident on the detector through the measurement material is provided,
Before performing the laser welding, the measurement material is irradiated with light from the measurement light source in advance, the amount of light transmitted through the measurement material is measured by a detector, and the measurement signal is calculated by the calculation device. To calculate the transmittance of the measurement material,
An output corresponding to the calculated transmittance of the measurement material is set in the laser light source, and laser processing is performed by irradiating the work material with a laser beam having intensity set from the laser light source. Run,
Accordingly, the laser welding method is characterized in that the intensity of the laser light applied to the welded portion changes to a magnitude that immediately corresponds to the transmittance of the transmitting material that is welded at that time. The measurement material may be a portion of the material to be processed having the same thickness and transmittance as the welded portion other than the welded portion to be welded next in the transparent material of the workable material, or the transparent material. 4. The laser welding method according to claim 3, comprising a separate model of the same shape as the transmission material which is made of the same material as that of the transmission material and is supported at a position away from the workpiece material. When a large number of workpieces having the same shape are repeatedly welded, the output of the laser light source is controlled by the arithmetic unit during the processing of the same lot by first measuring the transmittance of the measurement material. The laser welding method according to claim 3 or 4, wherein the laser welding is performed repeatedly in a pattern. When the shape of the transmission material of the work material is complicated and the thickness is not uniform, or the crystal distribution inside the material of the transmission material is not uniform, and the transmittance is different for each part of the work material When measuring, the transmittance of each part of the measurement material is individually measured, and real-time control is performed to change the output of the laser light source in real time according to the individual measurement results. The laser welding method according to any one of claims 3 to 5. In the arithmetic device, a threshold is set for the transmittance of the measurement material,
The relationship between the transmittance of the measurement material and the output of the laser light source is defined in a map or a function expression and set in a memory in the arithmetic device,
An arithmetic process is performed to calculate the output of the laser light source from the measured transmittance of the measurement material, and in the calculation process, the measured transmittance of the measurement material is applied to the definition. , Calculate the output of the laser light source,
When performing the real-time control, by comparing the measured transmittance of the measurement material with the threshold value, when the measured transmittance of the measurement material is greater than the threshold value, the output of the laser light source When the measured transmittance of the measurement material is smaller than the threshold value, the output is adjusted to maintain the output, and the measurement of the transmittance of the measurement material and the output adjustment of the laser light source are repeated. The laser welding method according to any one of claims 3 to 6, wherein an output of the laser light source is controlled.   A laser welding apparatus configured to execute the laser welding method according to claim 1.

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