JP2003251699A - Laser welding method for resin parts - Google Patents

Abstract

[57] An object of the present invention is to effectively prevent deterioration of mechanical properties due to molecular deterioration of a molten resin without strictly managing gaps. A bonding surface 1a of a transparent resin material 1 that is transmissive to laser light as a heating source and a bonding surface 2a of an absorbent resin material 2 that is absorbent to the laser light face each other. And an irradiation step in which the joining surfaces 1a, 2a are heated and melted by welding with the laser beam from the side of the transparent resin material 1 and are joined together. In this irradiation process, the laser beam is irradiated after the gap S between the joint surfaces 1a and 2a is set to an inert gas atmosphere. Molecular deterioration due to oxidation of the molten resin can be suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser welding method for resin parts, and more particularly to a transparent resin material which is transparent to laser light as a heating source and an absorbent material which absorbs the laser light. TECHNICAL FIELD The present invention relates to a laser welding method for a resin component in which a resinous material is integrally joined by laser welding.

[0002]

2. Description of the Related Art In recent years, from the viewpoints of weight reduction and cost reduction, it has been frequently practiced to resinize parts in various fields such as automobile parts into resin molded products. Further, from the viewpoint of high productivity of the resin molded product and the like, it is often the case that the resin molded product is divided into a plurality of parts in advance and molded, and the divided molded products are joined together.

Here, a laser welding method has been conventionally used as a method for joining resin materials. For example, in Japanese Unexamined Patent Publication No. 11-348132, a transparent resin material that is transparent to a laser beam and an absorptive resin material that is absorptive to the laser beam are superposed and There is disclosed a laser welding method in which a joining surface of a transmissive resin material and an absorptive resin material are heated and melted by irradiating a laser beam from the functional resin material side to integrally join the two.

In this laser welding method, the laser light transmitted through the transparent resin material reaches the joining surface of the absorptive resin material and is absorbed, and the laser light absorbed in the joining surface is accumulated as energy. As a result, the joint surface of the absorbent resin material is heated and melted, and the joint surface of the permeable resin material is heated and melted by heat transfer from the joint surface of the absorbent resin material. By heating and melting the joining surfaces of the permeable resin material and the absorptive resin material in this manner and then cooling and solidifying them, both can be integrally joined.

[0005]

However, due to manufacturing problems such as molding warpage of a resin material, there are almost inevitably small gaps between the joining surfaces of the permeable resin material and the absorbent resin material.

When a gap is present between both joint surfaces as described above, the resin that is heated and melted by laser irradiation reacts with oxygen present in the gap to cause molecular deterioration due to oxidation,
There is a problem in that the mechanical strength of the resin part is deteriorated, such as the tensile strength of the welded part being reduced.

If the joining surfaces can be completely brought into close contact with each other by using a pressure jig or the like, the contact between the molten resin and oxygen can be avoided by eliminating the above gap, so that the welded portion It is possible to reduce the molecular deterioration of the resin.

However, it is not easy to strictly control the gap so that the joint surfaces are in close contact with each other, and this is extremely difficult especially in the case of a resin component having a three-dimensionally complicated shape.

The present invention has been made in view of the above circumstances, and a laser welding method for resin parts capable of effectively preventing deterioration of mechanical properties due to molecular deterioration of molten resin without strict clearance control. It is a technical issue to be solved to provide the above.

[0010]

A laser welding method for resin parts according to the present invention, which solves the above-mentioned problems, comprises a bonding surface of a transparent resin material which is transparent to laser light as a heating source, and the laser light. And a bonding surface of the absorptive resin material having an absorptive property, and the laser light irradiation from the transparent resin material side, and the bonding surface of the transparent resin material and the absorptive resin. In a laser welding method of a resin component, which comprises an irradiation step of integrally melting the transparent resin material and the absorptive resin material by melting and welding the joining surfaces of the materials together, in the irradiation step, It is characterized in that the gap between the bonding surface of the permeable resin material and the bonding surface of the absorptive resin material is made an inert gas atmosphere, and then the irradiation of the laser beam is performed.

In a preferred embodiment, the inert gas is blown into the gap using a gas injection device.

In a preferred embodiment, the inert gas is blown from the front in the traveling direction of laser welding.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION A laser welding method for a resin component according to the present invention has a joining surface of a transparent resin material which is transparent to a laser beam as a heating source, and has absorptivity to the laser beam. By arranging the bonding surface of the absorptive resin material to face each other and irradiating the laser beam from the transparent resin material side, the bonding surfaces of the transparent resin material and the absorptive resin material are heated and melted. An irradiation step of welding and integrally joining the permeable resin material and the absorptive resin material.

In the arranging step, the joining surface of the permeable resin material and the joining surface of the absorbent resin material are opposed to each other. At this time, the gap formed between the two joint surfaces can be adjusted by using a pressure jig or the like, if necessary, so that heat can be transferred from the joint surface of the absorptive resin material to the transparent resin material in the irradiation step described later. The size is such that the joint surface is sufficiently heated and melted to secure the necessary joint strength. In addition, it is of course possible to make the gap as small as possible with a pressure jig or the like in order to further improve the bonding strength.

In the irradiation step, laser light is irradiated from the transparent resin material side toward the bonding surface of the absorbent resin material. The laser light emitted from the transparent resin material side passes through the inside of the joining end portion of the transparent resin material, reaches the joining surface of the absorbing resin material, and is absorbed. As a result of the laser light absorbed on the joint surface of the absorbent resin material being accumulated as energy, the joint surface of the absorbent resin material is heated and melted. The heat transfer from the bonding surface of the absorbent resin material heats and melts the bonding surface of the permeable resin material. By heating and melting the joining surfaces of the permeable resin material and the absorptive resin material in this manner and then cooling and solidifying them, both can be integrally joined.

In the joint thus obtained, the joint end faces are melted and joined together, and between the joint end faces, both resins constituting both members are melted and entangled with each other. Therefore, a strong joint state is formed and high joint strength and pressure resistance are obtained.

Here, in the laser welding method for resin parts of the present invention, in the irradiation step, the gap between the bonding surface of the transparent resin material and the bonding surface of the absorbent resin material is set to an inert gas atmosphere. Then, the laser light is irradiated. For this reason,
It is possible to prevent the resin melted by the heat generated by the irradiation of the laser beam from coming into contact with oxygen. Therefore, it is possible to effectively prevent the molecular deterioration due to the oxidation of the resin without strict control of the gap with a pressure jig or the like. Therefore, it is possible to prevent the mechanical properties of the resin component from being deteriorated, such as a decrease in the tensile strength of the welded portion.

Further, if strict clearance control is performed by a pressure jig or the like so as to eliminate the clearance between the joint surfaces as much as possible, the residual stress of the resin component after laser welding is increased due to the increase in the load required for the clearance control. There is a possibility that the size becomes large and a problem occurs in the strength of the resin part, or the appearance quality is deteriorated due to the protrusion of the molten resin. In this respect, according to the method of the present invention, as described above, strict clearance management is unnecessary, so that the load required for clearance management can be reduced. Therefore, the residual stress of the resin component can be reduced, and it is possible to suppress the deterioration of the strength and appearance quality of the resin component.

There is no particular limitation on the means for making the gap between the two joint surfaces an inert gas atmosphere. For example, it is possible to irradiate the laser beam with the permeable resin material and the absorptive resin material placed in a furnace or the like in an inert gas atmosphere, but using a gas injection device such as a nozzle It is preferable to blow an inert gas into the gap between the joint surfaces. If the inert gas is blown by the gas injection device, the gap can be simply and more surely made into the inert gas atmosphere, and therefore, the oxidative deterioration of the resin can be more surely prevented. .

When a gas injection device is used, it is preferable to blow an inert gas from the front (obliquely front) with respect to the traveling direction of laser welding. By doing so, it becomes easy and sure that the above-mentioned gap is previously made of an inert gas.

Here, it is preferable that the outlet of the inert gas in the gas injection device has a diameter of about 1 to 10 mm so that the inert gas can be more reliably blown into the gap.

The type of the inert gas is not particularly limited, and argon gas, nitrogen gas, etc. can be appropriately selected.

Here, the transparent resin material is not particularly limited as long as it has thermoplasticity and has a transmittance of a predetermined value or more for the laser light as the heating source. For example, nylon 6 (PA6) and nylon 66 (P
Polyamide (PA) such as A66), polyethylene (P)
E), polypropylene (PP), styrene-acrylonitrile copolymer, polyethylene terephthalate (PE
T), polystyrene, ABS, acrylic (PMME),
Examples thereof include polycarbonate (PC) and polybutylene terephthalate (PBT). If necessary, reinforcing fibers such as glass fiber and carbon fiber, or those to which a coloring material is added may be used.

The absorptive resin material is not particularly limited as long as it has a thermoplasticity and an absorptance of a laser beam as a heat source of a predetermined value or more. For example, polyamide (PA) such as nylon 6 (PA6) or nylon 66 (PA66), polyethylene (PE), polypropylene (PP) or styrene-acrylonitrile copolymer, polyethylene terephthalate (PET), polystyrene,
ABS, acrylic (PMME), polycarbonate (P
Examples thereof include C), polybutylene terephthalate (PBT), and the like, in which a predetermined coloring material such as carbon black, a dye, or a pigment is mixed. In addition, you may use what added reinforcing fiber, such as glass fiber and carbon fiber, as needed.

The permeable resin and the non-permeable resin are those which are compatible with each other. Examples of such a combination include a combination of resins of the same kind such as nylon 6 or nylon 66, a combination of nylon 6 and nylon 66, a combination of PET and P
Examples thereof include a combination with C and a combination with PC and PBT.

The type of the laser light used as the heating source depends on the absorption spectrum and the thickness (transmission distance of the laser light) of the transparent resin material that allows the laser light to pass through, and A material having a wavelength such that the transmittance becomes a predetermined value or more is appropriately selected. For example, YAG: Nd
³⁺ laser (laser light wavelength: 1060 nm) and semiconductor (diode) laser (laser light wavelength: 500 to 10)
00 nm) can be used.

Irradiation conditions such as laser output, irradiation density and processing speed (moving speed) can be appropriately set according to the type of resin.

The shapes of the permeable resin material and the absorptive resin material and the joining form of the two resin materials are not particularly limited, and the joining end portion and the absorbing portion of the permeable resin material such as a plate material or a bar material are used. Made by butt-joining the joining end faces of the joining end of the resinous material, or joining the joining end faces of the permeable resin material and the joining end face of the absorbent resin material, which consist of split bodies of a predetermined shape It may be a hollow body such as a box-shaped body or a tubular body.

[0029]

EXAMPLES Examples of the laser welding method for resin parts of the present invention will be specifically described below with reference to the drawings.

(Embodiment) The laser welding method for resin parts of the present embodiment is a step of arranging the joining surface of the transparent resin material and the joining surface of the absorptive resin material so as to face each other, and from the transparent resin material side. By irradiating the laser beam, the joint surface of the transparent resin material and the joint surface of the absorbent resin material are heated and melted to be welded to each other to integrally bond the transparent resin material and the absorbent resin material. And an irradiation step.

<Arrangement Step> First, the transparent resin material 1 and the absorbent resin material 2 were prepared.

The transmissive resin material 1 has such a transmissivity with respect to laser light that energy required for laser welding can reach the bonding surface 2a of the absorptive resin material 2. Specifically, in this example, a reinforced plastic obtained by adding 30 wt% of glass fiber as a reinforcing material to PA6 and an appropriate amount of carbon black as an auxiliary agent (coloring material) was used. The laser light transmittance of this transparent resin material 1 is 3
It is 0%.

The absorptive resin material 2 is absorptive of the laser light as a heating source. Specifically, in this example, a reinforced plastic obtained by adding 30% by weight of glass fiber as a reinforcing material and carbon black as an auxiliary agent (coloring material) to PA6 in an appropriate amount was used. The laser light absorptivity of this absorbent resin material 2 is 10
It is 0%.

The permeable resin material 1 and the absorbent resin material 2 both use PA6 as a matrix resin and are compatible with each other.

Then, the permeable resin material 1 was superposed on the absorbent resin material 2, and the joint surface 1a of the permeable resin material 1 and the joint surface 2a of the absorbent resin material 2 were opposed to each other. At this time, by gap management using a pressure jig (not shown),
A gap S of about 0.2 mm is entirely formed between the joint surfaces 1a and 2a.

<Irradiation Step> A semiconductor (diode) laser (manufactured by Roffin Co., as a laser beam used as a heating source,
A laser torch 3 emitting a wavelength of 940 nm) was prepared.

On the other hand, a gas injection nozzle 4 having a gas outlet of 3 mm was prepared as a gas injection device capable of injecting an argon gas as an inert gas.

The laser torch 3 and the gas injection nozzle 4 are attached to a robot (not shown) so that they can be moved in the same manner.

Then, by a robot operation (not shown), the laser torch 3 and the gas injection nozzle 4 are moved in the same manner, and an inert gas is blown from the gas injection nozzle 4 into the gap S to irradiate the laser beam. Gap S
After making the inert gas atmosphere, laser light emitted from the laser torch 3 was irradiated from the transparent resin material 1 side toward the bonding surface 2a of the absorbent resin material 2. Thereby, the joint surface 1a of the permeable resin material 1 and the joint surface 2a of the absorbent resin material 2
Was melted by heating and welded, and the permeable resin material 1 and the absorbent resin material 2 were integrally joined.

Here, as shown in FIGS. 1 and 2, the laser light from the laser torch 3 is absorbed by the absorptive resin material 2.
Irradiation is perpendicular to the joint surface 2a of (1) (with respect to the horizontal direction in which the gap S extends). On the other hand, the gas injection nozzle 3
Is located at the same height as the gap S, and the inert gas from the gas injection nozzle 3 is injected parallel to the horizontal direction in which the gap S extends. In addition, the inert gas from the gas injection nozzle 3 is applied to a portion irradiated with laser light obliquely from the scanning direction of laser light (moving direction, P arrow direction in FIG. 1), that is, the traveling direction of laser welding. It is sprayed beforehand.

The laser irradiation condition is output 400
W, scanning speed: 4 m / min.

As described above, in the irradiation process of this embodiment, the joining surface 1a of the transparent resin material 1 and the joining surface 2a of the absorbent resin material 2 are joined together.
Since the laser beam is radiated after the gap S between and is made into an inert gas atmosphere in advance, it is possible to prevent the resin melted by heat generated by the laser beam from coming into contact with oxygen. Therefore, it is possible to effectively prevent the molecular deterioration due to the oxidation of the resin without strict control of the gap with a pressure jig or the like. Therefore, it is possible to prevent the mechanical properties of the resin component from being deteriorated, such as a decrease in the tensile strength of the welded portion.

Further, in this embodiment, since the strict clearance control for eliminating the clearance is not performed and the load required for the clearance management is small, the residual stress of the resin component after laser welding is also small, and the resin component is small. It is possible to prevent the strength and the appearance quality from deteriorating.

Further, in this embodiment, the gas injection nozzle 3
Is used to spray the inert gas directly onto the gap S, and further, the inert gas is sprayed in advance on the portion irradiated with the laser light obliquely from the front with respect to the traveling direction of the laser welding. For this reason, the gap S can be simply and more reliably made into the inert gas atmosphere in advance, and therefore, it becomes possible to more reliably prevent the oxidative deterioration of the resin.

(Comparative Example 1) Laser welding was carried out in the same manner as in the above example except that the inert gas was not injected from the gas injection nozzle 3 into the gap S.

Comparative Example 2 The transparent resin material 1 and the absorptive resin material 2 were joined by vibration welding instead of laser welding.

(Comparative Example 3) Laser welding was carried out in the same manner as in the above-described example except that the above-mentioned gap S was set to 0 mm by strict gap management and that the inert gas was not jetted from the above-mentioned gas jet nozzle 3.

(Evaluation of Deterioration Degree of Resin in Welded Part) In the above Examples and Comparative Examples 1 to 3, the degree of molecular deterioration of the resin in the welded part was evaluated by the degree of non-decrease in molecular weight of the welded part.

That is, by using a molecular weight distribution measuring device (manufactured by Tosoh Corporation), the molecular weight in the welded portion and the molecular weight in the resin base material other than the welded portion were measured,
The ratio of the molecular weight of the welded portion to the molecular weight of the resin base material was determined, and this ratio was defined as the degree of non-decrease in molecular weight.

A large degree of non-decrease in molecular weight means that the molecular weight of the welded portion is large, that is, the degree of molecular deterioration of the resin is small.

As shown in FIG. 3 for the results of this Example and Comparative Example 1, in Comparative Example 1 in which the gap S was not an inert gas atmosphere, the non-decreasing degree of the molecular weight at the welded portion was as small as about 30, and the welded portion The resin was greatly deteriorated. In contrast,
In this example, the degree of non-decrease in molecular weight at the welded portion is 90.
It was about three times as high as that of the comparative example, and the resin in the welded portion was hardly deteriorated.

As shown in FIG. 4, the results of Comparative Examples 1 to 3 are vibration welded Comparative Example 2 and the gap S is set to 0 mm.
In addition, in Comparative Example 3 in which the inert gas was not injected from the gas injection nozzle 3, the degree of non-decrease in molecular weight at the welded portion was about 90. That is, the degree of non-decrease in molecular weight in the welded portion of this example was similar to the degree of non-decrease in molecular weight in the case of vibration welding and in the case of laser welding with a gap S of 0 mm.

(Evaluation of Tensile Strength of Welded Part) In the above example,
For Comparative Example 1 and Comparative Example 3, the tensile strength at the welded portion was evaluated. That is, using an autograph device for 5 kN (manufactured by Shimadzu Corporation), room temperature 23 ° C, humidity 50
%, And a test speed of 2 mm / min, a tensile strength test was performed in the direction perpendicular to the welding surface.

The results are shown in FIG. FIG. 5 shows the tensile strength ratio (%) in this example and Comparative Example 1 when the tensile strength in Comparative Example 3 is 100%.

As is clear from FIG. 5, the tensile strength of the welded portion in this example is almost the same as the tensile strength of the welded portion in Comparative Example 3 in which the gap S is set to 0 mm by strict clearance control. In addition, the tensile strength of the welded portion in Comparative Example 1 in which the gap S is not an inert gas atmosphere is about 2.
It was 5 times or more. The tensile strength of the welded part in the present example was 45 to 50 MPa, and the tensile strength of the welded part in Comparative Example 1 was 20 MPa or less.

As a result, if the degree of non-decrease in molecular weight at the welded portion is large (if the degree of molecular deterioration of the resin is small)
It was confirmed that a high tensile strength can be secured, and according to this example, a welded portion having a high tensile strength can be obtained.

[0057]

As described above in detail, in the laser welding method for resin parts of the present invention, the irradiation of the laser beam is performed after the gap between both joint surfaces is made an inert gas atmosphere in the irradiation step. It is possible to effectively prevent the molecular deterioration due to the oxidation of the resin without performing strict clearance control, and thus to prevent the mechanical properties of the resin part from being deteriorated such as the reduction of the tensile strength of the welded portion. It will be possible.

Since strict clearance control is not required,
It is possible to reduce the load required for the clearance management, and thus to reduce the residual stress of the resin component and suppress the deterioration of the strength and appearance quality of the resin component.

[Brief description of drawings]

FIG. 1 is a perspective view schematically illustrating a laser welding method for resin parts according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view schematically illustrating a laser welding method for resin parts according to an embodiment of the present invention.

FIG. 3 is a diagram showing the evaluation results of the non-decreasing degree of molecular weight at the welded portion in Example and Comparative Example 1.

FIG. 4 is a diagram showing the evaluation results of the non-decreasing degree of molecular weight at the welded portion for Comparative Examples 1 to 3.

FIG. 5 is a diagram showing evaluation results of tensile strength in a welded portion in Examples, Comparative Examples 1 and 3.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Transparent resin material 2 ... Absorbent resin material 3 ... Laser torch 4 ... Gas injection nozzle 1a, 2a ... Joining surface

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yusuke Umeya             1 Toyota Town, Toyota City, Aichi Prefecture Toyota Auto             Car Co., Ltd. F-term (reference) 4E068 CH07 CJ01 DB10                 4F211 AA23 AB13 AB18 AD19 AM30                       TA01 TC02 TD11 TH02 TH30                       TN27

Claims (3)

[Claims] 1. An arranging step in which a bonding surface of a transparent resin material that is transparent to laser light as a heating source and a bonding surface of an absorbent resin material that absorbs the laser light are opposed to each other. And by irradiating the laser beam from the transparent resin material side, the bonding surface of the transparent resin material and the bonding surface of the absorptive resin material are heated and melted to be welded to each other. In a laser welding method for a resin component, which comprises an irradiation step of integrally bonding an absorptive resin material, in the irradiation step, between the bonding surface of the transparent resin material and the bonding surface of the absorbent resin material. A laser welding method for a resin component, which comprises irradiating the above laser light after making the gap an inert gas atmosphere. 2. The laser welding method for resin parts according to claim 1, wherein the inert gas is blown into the gap using a gas injection device. 3. The laser welding method for resin parts according to claim 2, wherein the inert gas is blown from the front side in the traveling direction of laser welding.