JP3970680B2 - Annealing method for resin products - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a novel method for annealing a resin product. Specifically, the present invention relates to a technique for removing distortion generated in a heat-welded portion of a resin product in a short time.
[0002]
[Prior art]
The synthetic resin parts welded by the welding means such as hot plate welding method, vibration welding method, etc. have stress in the heat welding part, so it is necessary to remove the residual stress by keeping it at a constant temperature for a certain time or more is there.
[0003]
Therefore, in the prior art, there is a technique for removing the residual stress by heating the resin product while transporting the resin product on a predetermined path in a substantially sealed annealing furnace and maintaining the temperature at a constant temperature for a predetermined time or more.
[0004]
For example, a travel path for moving the resin product along a predetermined path is provided in the annealing furnace, and a heater is disposed in the vicinity of the travel path, so that the resin product travels from the start end to the end of the travel path by the heater. Some are heated to a predetermined temperature and kept at that temperature after reaching a predetermined temperature.
[0005]
[Problems to be solved by the invention]
Incidentally, the above-described conventional annealing method has several problems.
[0006]
First, because the temperature of the entire annealing furnace is raised using a near-infrared heater as the heater, it takes time to raise the temperature of the resin product to a certain temperature, which is necessary in each process for manufacturing the resin product. There is a problem that it is not consistent with time. For example, in the case of a certain type of automotive lamp, the time required for each process is about 40 seconds, while the time required for the annealing process is about 15 minutes. Therefore, in order to prevent stagnation of products on the production line, an annealing furnace capable of running 20 or more resin products is prepared on the line so that play time does not occur in each process. Must be. For this reason, there is a problem that a large space for an annealing furnace capable of running a large number of resin products on the line is required, which hinders downsizing of the manufacturing apparatus. In addition, a traveling route for traveling 20 or more resin products and a large number of heaters arranged in the vicinity of the traveling route must be provided, and the equipment cost becomes enormous and the spectral heat cost that takes time increases. There is a problem that it takes too much.
[0007]
Furthermore, for the resin product moving along a predetermined route, the heater must be arranged at a position that does not interfere with traveling, and the heater arrangement position is restricted. For this reason, a part near the heater and a part far from the heater are generated at the part requiring the strain removal of the resin product, and if it is kept at a predetermined temperature near the heater, the part far from the heater may rise to the predetermined temperature. If the part far from the heater is kept at a predetermined temperature without being sufficiently distorted, there is a problem that the part near the heater is heated to a temperature higher than the predetermined temperature and deformed. is there.
[0008]
Then, this invention makes it a subject to remove the distortion which arose in the heat welding part of the resin product in a short time, without requiring big equipment.
[0009]
[Means for Solving the Problems]
In order to solve the above-described problems, the method for annealing a resin product of the present invention includes a temperature raising step of irradiating far infrared rays to raise the surface temperature of the heat-welded portion of the resin product to a target temperature, and the surface of the heat-welded portion. A holding step for holding the temperature at the target temperature, and the holding step is performed by moving the heater away from the position where the heater was positioned during the temperature raising step so as to be separated from the heat welding portion. Further, the internal temperature of the heat welding part is raised to the target temperature or a temperature near the target temperature.
[0010]
Therefore, in the annealing method of the resin product of the present invention, the heat-welded portion of the resin product is heated in a short time because the heat-welded portion is heated by a far infrared ray that is easily absorbed by the thermoplastic resin, that is, the thermoplastic resin. To reach the target temperature.
[0011]
In addition, after the surface temperature of the heat-welded part of the resin product rises to the target temperature, the process proceeds to a holding process in which the surface temperature of the heat-welded part is maintained at the target temperature. It will never be too high. Further, since the holding step is performed by moving the heater away from the heat welding portion from the position located during the temperature raising step, simple equipment for the holding step is sufficient. .
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of an annealing method for resin products of the present invention will be described below with reference to the accompanying drawings. In the embodiment described below, the present invention relates to an envelope (resin product) in which a lamp body and a lens of a vehicular lamp are joined by heat welding such as hot plate welding or vibration welding. This is applied to an annealing method for removing residual stress at the joint (thermal weld) with the lens.
[0013]
In general, ABS resin, AAS resin, or ASA resin is used as the material of the lamp body 2 of the envelope 1 having a lamp space for arranging a light source or the like inside, and acrylic resin is used as the material of the lens 3. used. As described above, the envelope 1 of the vehicle lamp is an example of a resin product that removes the residual stress of the heat-welded portion by the method of the present invention, and the resin product to which the present invention is applied is a vehicle lamp. Of course, it is not limited to the envelope. Moreover, the material of each part joined by the heat welding of the said resin product is not limited to the above-mentioned resin material, ie, ABS resin, AAS resin, ASA resin, and acrylic resin.
[0014]
An envelope 1 of a vehicular lamp is formed by joining a lamp body 2 and peripheral portions 2a and 3a of a lens 3 by heat welding. Then, stress remains in the heat welding portion 4 which is a joint portion between the peripheral edge portion 2a of the lamp body 2 and the peripheral edge portion 3a of the lens 3 due to heating at the time of heat welding.
[0015]
A far-infrared heater 5 is used to heat the heat welding part 4 of the envelope 1. The heater 5 is formed by embedding a heating wire 7 such as a nickel wire in a base material 6 made of ceramics, and has a parabolic shape in a vertical cross section in order to improve thermal efficiency. The area 8 surrounded by the heat generating surface 5a of 5 and the converging position F of the paraboloid is an effective heating range (area with broken line hatching) (see FIG. 2). In this effective heat generation range 8, the density of far infrared rays is high and the heat generation efficiency is good.
[0016]
The material of the heater that emits far infrared rays is not limited to ceramics, and the shape of the heat generating surface is not limited to a parabolic surface.
[0017]
At the position where the annealing step is performed, a moving base 9 is provided that can move in a direction to be separated from or in contact with the envelope 1, and a plurality of heaters 5, 5,. That is, when the moving base 9 is positioned close to the envelope 1, the plurality of heaters 5, 5,... Are supported by the moving base 9 so as to surround the heat welding portion 4 of the envelope 1. In addition, as shown in FIG. 2, the heaters 5, 5,... Are arranged so that the heat welding portion 4 of the envelope 1 is positioned in the region 8.
[0018]
Next, each process for removing the residual stress of the heat welding part 4 of the envelope 1 is demonstrated with reference to FIG.
[0019]
First, the envelope 1 is placed on the work support 10. At this time, the moving base 9 is spaced above the envelope 1 and stands by at the standby position (see FIG. 3A). The heaters 5, 5,... Are energized and heated to an appropriate temperature.
[0020]
When the envelope 1 is placed on the work support 10, the moving base 9 is lowered, and the heaters 5, 5,. It is located so that the heat welding part 4 may be surrounded (refer FIG. 1, FIG.3 (b)). In this state, the heat-welded portion 4 of the envelope 1 is positioned within the effective heat generation ranges 8, 8,... Of the heaters 5, 5,. Thereby, the temperature raising step is started.
[0021]
When the temperature of the surface 4a of the heat-welded portion 4 reaches the target temperature, that is, about 80 ° C. which is the glass transition point of the material resin of the lamp body 2 and the lens 3, the heat-welded portion 4 of the envelope 1 is The moving base 9 is raised so as to be positioned outside the effective heat generation ranges 8, 8,... Of the heaters 5, 5,. In this way, the holding process is started.
[0022]
The envelope 1 of a standard rear combination lamp of an automobile is a resin product, the temperature of the heat generating surface 5a of the heater 5 is 380 ° C. to 390 ° C., the heat generating surface 5a of the heater 5 and the surface 4a of the heat welding portion 4 ( 2), the temperature of the surface 4a of the heat-welded portion 4 is the target temperature in about 5 seconds after the temperature raising process is started in the state of FIG. It reaches some 80 ° C. When the temperature of the surface 4a of the heat-welded portion 4 reaches about 80 ° C., the temperature of the inner surface 4b (see FIG. 2) spaced from the surface 4a by about 3 mm from the heater 5 becomes around 50 ° C. (See FIG. 4).
[0023]
Then, by keeping the heaters 5, 5,... Away from the heat welding part 4, the temperature rise of the surface 4a of the heat welding part 4 to 80 ° C. or more can be suppressed, while the heaters 5, 5,. By maintaining an appropriate distance from the heat welded portion 4, the temperature of the surface 4a of the heat welded portion 4 is kept constant, and the temperature of the surface 4a is transmitted to the inside by heat conduction, so that the heat welded portion 4 The temperature inside increases.
[0025]
As the rising distance from the position in the temperature raising process of the heaters 5, 5,... For keeping the temperature of the surface 4a of the heat welding part 4 at about 80 ° C. and increasing the internal temperature, the rear combination lamp In the case of the envelope 1, it is about 50 mm.
[0026]
Then, the temperature of the inner surface 4b of the heat welded portion 4 rises to the target temperature of about 80 degrees C. When the temperature is held for a certain period of time, the holding process is terminated and the moving base 9 is raised to the standby position (FIG. 3). (See (c)).
[0027]
In the case of the envelope 1 of the rear combination lamp, the temperature of the inner surface 4b of the heat welding part 4 reaches the target temperature (80 ° C.) in about 12 to 13 seconds from the start of the temperature raising process (see FIG. 4). The holding process is continued for about 17 seconds.
[0028]
By gradually cooling after the holding step, the stress remaining in the heat welded portion 4 is removed by heat welding.
[0029]
According to the above-described annealing method, the temperature can be raised to the target temperature of the heat-welded portion within about 30 seconds and maintained, and consistency with the process cycle of other processes can be obtained. There is no need to provide an unusually large space and time position on the top, and the equipment can be downsized and the equipment and operation costs can be reduced.
[0030]
Moreover, since the temperature of the heat-welded portion and the temperature can be maintained for each resin product, the product flow on the line becomes very smooth.
[0031]
Furthermore, in the above annealing method, a plurality of heaters 5, 5,... Can be arranged so as to surround the heat welded portion 4 in accordance with the shape of the heat welded portion 4, so that heating is necessary. Only a portion that needs to be heated can be heated without heating a portion that is not present, and problems such as deformation due to unnecessary heating can be solved.
[0032]
It should be noted that the shapes, structures, numerical values, and the like of the respective parts shown in the above-described embodiments are merely examples of the implementation performed in carrying out the present invention, and thus the technical scope of the present invention. Should not be interpreted in a limited way.
[0033]
【The invention's effect】
As is apparent from the above description, the annealing method of the resin product of the present invention is an annealing method in which the heat-welded part of the resin product is heated by a heater to remove the strain generated in the heat-welded part, a heating step of irradiating infrared rays raise the surface temperature of the heat welded portion to the target temperature, the surface temperature of the heat welded portion includes a holding step of holding to the target temperature, the holding step, the heater Moved away from the heat welded portion from the position located during the temperature raising step, and raised the internal temperature of the heat welded portion to the target temperature or a temperature near the target temperature during the holding step. It is characterized by making it.
[0034]
Therefore, in the annealing method of the resin product of the present invention, the heat-welded portion of the resin product is heated in a short time because the heat-welded portion is heated by a far infrared ray that is easily absorbed by the thermoplastic resin, that is, the thermoplastic resin. To reach the target temperature. Therefore, the resin product can be annealed in a very short time.
[0035]
In addition, after the surface temperature of the heat-welded part of the resin product rises to the target temperature, the process proceeds to a holding process in which the surface temperature of the heat-welded part is maintained at the target temperature. It will never be too high. Therefore, deformation of the resin product due to an abnormal increase in temperature can be avoided. Since the surface temperature is transmitted to the inside of the heat welded portion by heat conduction, the internal temperature rises to the target temperature by keeping the surface temperature at the target temperature.
[0036]
Furthermore, since annealing can be performed for each resin product, the equipment can be small, and the equipment can be miniaturized, the cost can be reduced, and the operation cost can be reduced.
[0037]
Then, further, the holding step, is performed by moving to space from the heat welded portion from the position located above the heater during temperature rise process, equipment for holding step is sufficient in those simple .
[0038]
In the invention described in claim 2 , the heater has a shape for condensing far infrared rays, and the thermal welding portion is positioned closer to the heater than the far infrared ray condensing position during the temperature raising step. Therefore, it is possible to efficiently raise the temperature of the heat welding part.
[Brief description of the drawings]
FIG. 1 shows an embodiment of the annealing method of the present invention, and FIG. 1 is a diagram showing a planar positional relationship between a resin product and a heater.
FIG. 2 is an enlarged side view of a heater.
FIG. 3 is a diagram schematically showing the whole process, and shows a schematic cross-sectional view in order of time series from left (a) to right (d) together with a graph.
FIG. 4 is a graph showing the transition of the surface temperature and internal temperature of the heat welded portion.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Envelop (resin product), 4 ... Thermal welding part, 4a ... Surface, 4b ... Inner surface (inside), 5 ... Heater, F ... Condensing position

Claims (2)

An annealing method for removing the distortion generated in the heat welded portion by heating the heat welded portion of the resin product with a heater,
A temperature raising step of irradiating far infrared rays to raise the surface temperature of the heat welded portion to a target temperature,
A holding step of holding the surface temperature of the heat welded portion at the target temperature;
The holding step is performed by moving the heater away from the heat welded portion from the position where the heater was located during the temperature raising step.
An annealing method for a resin product, characterized in that, during the holding step, the internal temperature of the heat welded portion is raised to the target temperature or a temperature in the vicinity of the target temperature. The said heater has a shape which condenses a far-infrared ray, The said heat welding part is located in a position near a heater from the condensing position of a far-infrared ray during the said temperature rising process. Annealing method for resin products.

Images