JP2004034467A - Sealing structure and sealing method for electrical component - Google Patents

Abstract

An object of the present invention is to provide a sealing structure and a sealing method in which an electric component such as a thermistor is molded with high quality using an inexpensive general-purpose fluororesin tube without using a special heat-shrinkable tube.
An electric component (thermistor) electrically connected to a distal end of a conductive wire is disposed inside a thermoplastic resin hollow tube (FEP tube) having no heat shrinkage, and one end of the hollow tube. Lead out from the portion, in this state the other end of the hollow tube is fitted into the bottomed cylindrical mold, then, while pressing the hollow tube toward the bottom of the mold, The other end of the hollow tube is heated and melted so that all of the electric components and a part of the conductive wire are closely covered and melted and solidified.
[Selection diagram] FIG.

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a sealing structure and a sealing method for an electric component having a structure in which an electric component such as a sensor is sealed with a fluorine resin or the like.
[0002]
[Related background art]
When a temperature sensor (electric component) such as a thermistor is used, it is often molded (sealed) with, for example, a fluororesin (FEP; fluorinated ethylene propylene, etc.) in order to prevent deterioration of its insulation and element characteristics. Is Specifically, for example, as disclosed in Japanese Patent Application Laid-Open No. 5-208423, an FEP tube containing a thermistor (electric component) inside is sandwiched between a pair of molds, and heated and perpendicular to the axial direction. Pressing is performed to heat and melt the FEP tube to mold the thermistor.
[0003]
[Problems to be solved by the invention]
However, in the above-described method, since the resin (FEP tube) heated and melted hardly flows, there is a problem that air in the FEP tube is hardly discharged to the outside and bubbles are easily left in the sensor sealing portion. In particular, when using a resin having transparency such as a fluororesin, the above-described bubbles may be judged to be unfavorable in appearance, even if they do not have any influence on the performance of the built-in electric components. is there. Therefore, the presence of bubbles causes a reduction in commercial value. Moreover, it is necessary to interpose a highly heat-resistant resin sheet such as PTFE (polytetrafluoroethylene) on the contact surface between the FEP tube and the mold, thereby facilitating removal of the FEP tube from the mold. Therefore, there is a problem that the operation cost is increased.
[0004]
On the other hand, Japanese Patent No. 3215301 discloses a technique of molding an electric component such as a thermistor using a special heat-shrinkable tube having a two-layer structure made of FEP. According to the molding technique using the heat-shrinkable tube, a thermistor or the like can be easily molded. However, special heat shrink tubes of this type are expensive and generally difficult to obtain.
[0005]
The present invention has been made in view of such circumstances, and its purpose is to mold a high-quality electric component such as a thermistor using a general-purpose inexpensive fluororesin tube without using a special heat-shrinkable tube. To provide a sealing structure and a sealing method.
[0006]
[Means for Solving the Problems]
In order to achieve the above-described object, a sealing structure for an electric component according to the present invention includes an electric component electrically connected to a distal end portion of a conductive wire and a heat sealing member for sealing the electric component, for example, a general-purpose FEP. It is composed of a sheath mainly composed of a hollow tube of a thermoplastic resin having no shrinkage,
In particular, all of the electrical components positioned inside the hollow tube and a part of the conductive wire are obtained by extracting the conductive wire from one end of the hollow tube and melting and solidifying the other end of the hollow tube. Are sealed and covered in close contact.
[0007]
That is, the sealing structure of the electric component according to the present invention is, for example, a sheath that is mainly composed of a hollow tube made of a general-purpose FEP and has no heat-shrinkable thermoplastic resin, in which the electric component is positioned in advance. By melting and solidifying the end side, all of the electric components have a mold structure covered with the melted and solidified thermoplastic resin together with the connection portion with the conductor.
[0008]
Incidentally, the sealing structure for an electric component according to the present invention preferably covers the electrical connection portion between the end of the conductor and the electric component with a protective tube made of a thermoplastic resin of the same material as the jacket. It is realized as a thing of the structure. Further, the sealing structure for an electric component according to the present invention is preferably realized as a structure in which an electric connection portion between the electric component and the conductive wire is arranged toward the other end of the jacket to be melted and solidified. Is done.
[0009]
Further, the method of sealing an electric component according to the present invention includes disposing an electric component electrically connected to a distal end portion of a conductive wire inside a thermoplastic resin non-heat-shrinkable hollow tube. The conductor is led out from one end of the mold, and in this state, the other end of the hollow tube is fitted into a bottomed cylindrical mold, and then the hollow tube is pressed toward the bottom of the mold. While the other end of the hollow tube is heated and melted, the entirety of the electric component and a part of the conductive wire are closely covered and melted and solidified.
[0010]
That is, in the method for sealing an electric component according to the present invention, the other end of the hollow tube containing the electronic component is fitted into the bottomed cylindrical mold, and the other end of the hollow tube is sealed. Is pressed against only the hollow tube toward the bottom of the mold while heating. Then, while storing the heated and melted thermoplastic resin at the bottom of the mold, the connection portions between all of the electric components and the conductive wires are embedded in the thermoplastic resin, and then the heated and melted thermoplastic resin is cooled. Then, the electric component is molded by solidification.
[0011]
Further, the method of sealing an electric component according to the present invention is preferably such that the electric component electrically connected to the distal end of the conducting wire is placed inside the hollow tube together with a thermoplastic resin mass of the same material as the hollow tube. Then, the other end of the hollow tube is fitted into a bottomed cylindrical mold in this state. Then, while pressing the hollow tube toward the bottom of the mold, the other end of the hollow tube and the thermoplastic resin lump are heated and melted, so that all of the electric components and a part of the conductive wire adhere to each other. It is characterized by being covered and melted and solidified.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a sealing structure and a sealing method for an electric component according to an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view showing a schematic structure of a sealing structure for an electric component according to the present invention. Reference numeral 1 denotes an electric component including a thermistor as a resistance temperature measuring element (temperature sensor). This thermistor 1 is used by spot-welding a pair of lead terminals 2a and 2b to core wires 4 and 4 of two covered conductors 3 and 3 in advance. In particular, the thermistor 1 is embedded in the end of a hollow tube (FEP tube) 5 made of a general-purpose FEP and made of a non-heat-shrinkable thermoplastic resin made of a general-purpose FEP, together with the connection portions of the covered wires 3. The covered conductors 3 and 3 are led out of the open end of the hollow tube (FEP tube) 5 to the outside.
[0013]
By the way, embedding of the thermistor 1 and its connection with the covered conductors 3 and 3 by the jacket is performed by heating and melting the other end of the FEP tube 5 and flowing the resin material (FEP) which flows inside the FEP tube 5. This is performed by covering and solidifying the entire surface of the thermistor 1 and its connection with the covered conductors 3 and 3. That is, the connection between the thermistor 1 and the coated conductors 3, 3 is molded with a resin material (FEP) obtained by heating and melting a part of the FEP tube 5.
[0014]
As a result, the sealing structure of the electric component is formed by connecting the thermistor (electric component) 1 and the connecting portion between the covering conductors 3 and 3 with the sealing portion 5a molded by FEP and the sealing portion 5a. It is realized as a molded part in which the covered conductors 3 and 3 are integrated by covering them with a jacket consisting of a hollow tube (FEP tube) 5 of a predetermined length led out.
[0015]
When the connection between the thermistor (electrical component) 1 and its connection with the insulated wires 3 and 3 is molded by FEP, for example, as shown in FIG. 2, the lead terminals 2a and 2b of the thermistor 1 and the core wires of the insulated wires 3 and 3 are used. A heat-shrinkable protective tube 6 made of thermoplastic resin of the same material as the FEP tube (sheath body) 5 is previously placed on the connection portions spot-welded with the FEP tubes 4 and 4 and the distal end portions of the insulated wires 3 and 3. You may keep it. Incidentally, as for the protective tube 6, a small-diameter tube made of a thermoplastic resin (FEP) of the same material as the FEP tube (sheath body) 5 is set to an inner diameter slightly larger than the outer diameter of the coated conductors 3 and 3 in advance. It is sufficient if the diameter is expanded (expanded tube) so as to have heat shrinkage.
[0016]
When such a protective tube 6 is used, when the thermistor (electric component) 1 and its connection portion with the covered conductors 3 and 3 are molded by FEP, the heat of the resin material (FEP) melted by heating causes the heat of the covered conductors 3 and 3. The coating material is directly transmitted to the coating material of No. 3 (for example, FEP), and the coating material is melted or peeled off, thereby preventing a problem that insulation failure occurs. Further, the protection tube 6 receives heat from the resin material (FEP) melted by heat and thermally shrinks to completely cover the thermistor (electrical component) 1 and the connection portions with the covered conductors 3, 3. The insulation between the terminals 2a and 2b (between the core wires 4 and 4) can be improved.
[0017]
Even if the covering material of the covered conductors 3 and 3 is melted, the movement thereof is suppressed by the protective tube 6, and the sheath is pressed down toward the axis of the core wires 4 and 4 by the heat shrinkage of the protective tube 6. There is no loss of insulation. In other words, it is possible to mold with a resin material (FEP) that is heated and melted together with the thermistor (electric component) 1 while preventing the coating of the coated conductors 3 and 3 from peeling off. At this time, in order to ensure the sealability between the FEP tube 5 and the protective tube 6 and further between the protective tubes 6 and 6 and the coating material of the coated conductors 3 and 3, all these materials should be the same. Is enough.
[0018]
In order to realize the sealing structure of the electric component having the above-described sealing structure, for example, the distal end portion of the hollow tube (FEP tube) 5 may be heated and melted as shown in FIG. Specifically, a component is prepared in which the core wires 4 and 4 of the covered conductors 3 and 3 are spot-welded to the lead terminals 2a and 2b of the thermistor 1 in advance. At this time, it goes without saying that the above-described protective tubes 6 may be fitted into the connection portions. Thereafter, the thermistor 1 is inserted into a hollow tube (FEP tube) 5 having a predetermined length, and the covered wires 3 and 3 are respectively led out from one end of the FEP tube 5. At this time, the housing position of the thermistor 1 is determined in consideration of the fact that the tip (the other end) side of the FEP tube 5 is heated and melted to mold the thermistor 1.
[0019]
Thereafter, the FEP tube 5 is inserted into a bottomed cylindrical mold 10 as shown in FIG. 3 (a) from the end on the side where the thermistor 1 is positioned. The mold 10 has a hole that is slightly larger than the outer diameter of the FEP tube 5, and also has a function as a heating element for heating the FEP tube 5 to a temperature higher than its melting point (260 ° C.). Note that a cooling ring 11 is attached to the upper end opening of the mold 10. The cooling ring 11 plays a role of locally cooling the upper end of the mold 10 by blowing cool air (air) from the periphery thereof. The local cooling of the mold 10 by the cooling ring 11 facilitates the pushing of the FEP tube 5 into the mold 10.
[0020]
In this state, the mold 10 is heated to the melting point of the FEP tube 5 (260 ° C.) or more while pressing (pressing) only the FEP tube 5 toward the bottom of the mold 10. Then, the tip of the FEP tube 5 pressed and pressed against the bottom of the mold 10 is heated by the mold 10, heated and melted, and accumulated at the bottom of the mold 10. Then, as the FEP tube 5 is pushed in, the amount (bulk) of the heated and melted resin material (FEP) that accumulates at the bottom of the mold 10 gradually increases, and eventually, as shown in FIG. 1 and its connection with the covered conductors 3 and 3 are covered with a heat-melted resin material (FEP) without gaps. In this state, the mold 10 is cooled to solidify the resin material (FEP) which has been heated and melted as described above, and the FEP tube 5 is pulled out from the mold 10, whereby the FEP tube 5 is drawn as shown in FIG. 1 or FIG. Then, a sealing structure in which the thermistor 1 is molded at the tip is completed.
[0021]
Incidentally, when the thermistor 1 is molded by heating and melting the distal end side of the FEP tube 5 in this way, the entire surface of the thermistor 1 is sequentially arranged from the lower side while the heated and molten resin material (FEP) accumulates at the bottom of the mold 10. Since the air is covered, the air in the FEP tube 5 surely escapes from the upper end. As a result, there is no possibility that the sealing portion 5a contains bubbles or the like, and high-quality sealing can be performed. Further, since the outer shape of the resin material (FEP) that has been heated and melted can be solidified while being regulated by the mold 10, the sealing portion 5a having a good appearance can be formed. Therefore, even though the thermistor (electric component) 1 is molded using the inexpensive FEP tube 5 which is a general-purpose fluororesin, a high-quality and excellently shaped sealing structure can be easily realized. Moreover, since the manufacturing process is simple, there is an advantage that the manufacturing cost does not increase.
[0022]
In the case where the distal end of the FEP tube 5 is heated and melted as described above, it is desirable to provide a temperature gradient so as to increase the temperature from the distal end side (bottom side) of the mold 10. In order to provide such a temperature gradient, the mold 10 may be immersed in a liquid layer heated above the melting point of the FEP tube 5, for example, as shown in FIG. When such liquid layer heating is employed, the heat transfer property is better than that of hot air, heater heating, or the like, so that local heating of the mold 10 can be easily performed.
[0023]
Specifically, first, only the tip of the mold 10 is immersed in silicon oil (liquid layer) 12 and heated. After a lapse of a predetermined time, the mold 10 is gradually immersed in the silicon oil (liquid layer) 12 and heated at a predetermined immersion depth for a predetermined time. . At this time, the thickness of the mold 10 is gradually increased toward its upper part as shown in FIG. Is preferred.
[0024]
If the mold 10 is heated in this way, the heating and melting of the FEP tube 5 is positively promoted on the tip (bottom) side, so that the solidification of the FEP tube 5 is ensured from the tip. proceed. As a result, the air in the FEP tube 5 is reliably expelled from its upper end, so that it is possible to form an ideal sealing portion 5a that does not contain air bubbles.
[0025]
As described above, when the connection between the thermistor 1 and the coated conductors 3 and 3 is molded with a resin material (FEP) that is heated and melted, in the cooling and solidifying step, for example, the mold 10 is moved from the lower part to the upper part. , And the resin material (FEP) is solidified in order from the tip. That is, while the FEP tube 5 is pressed toward the bottom of the mold 10 to replenish the heat-melted resin material (FEP), the heat-melted resin material (FEP) is cooled and solidified in order from the bottom side of the mold 10. Thus, the connection portions between the thermistor 1 and the covered wires 3 are molded in order from the lower side.
[0026]
Incidentally, when the heat-melted resin material (FEP) is cooled and solidified from the middle part of the melting region, it is not possible to replenish the heat-melted resin material (FEP) to the lower side. Then, when the resin material (FEP) on the tip end side is solidified, it is unavoidable that so-called "sink" occurs due to heat shrinkage. Therefore, in order to realize a high-quality mold, it is desirable to solidify in order from the tip side as described above.
[0027]
Then, as shown in FIG. 1 described above, when the main body of the thermistor 1 is positioned at the tip side, first, the main body of the thermistor 1 is fixed with a solidified resin material (FEP), and then solidified subsequently. The connecting portions with the covered conductors 3 and 3 are molded by the resin material (FEP) to be formed. In the state where only the main body of the thermistor 1 is fixed in this way, the flow of the resin material (FEP) still molten may apply extra stress to the connection with the covered conductors 3 and 3. Therefore, there is a possibility that the core wires 4 and 4 are disconnected due to this.
[0028]
Therefore, in the present invention, in order to prevent the above-mentioned problems, for example, as shown in FIG. 5, a connecting portion between the thermistor (electric component) 1 and the covered conductors 3 and 3 is melted and solidified to mold the thermistor 1. It is arranged so as to face the distal end side of the body (EFP tube 1). Specifically, as shown in FIG. 6 (a), a pair of lead terminals 2a, 2b led out from one end of the thermistor 1 and covered conductors 3, 3 spot-welded to these lead terminals 2a, 2b, respectively. Of the thermistor 1 with respect to the distal end side of the jacket with respect to the body of the thermistor 1, and in this state, the thermistor 1 and the connection with the coated conductors 3, 3 are molded. It is what you do.
[0029]
The thermistor 1 does not have the above-mentioned lead terminals 2a, 2b, but has, on its body, terminals 2c, 2d for external connection, and these terminals 2c, 2d have the core wires 4 of the coated conductors 3, 3. , 4 are spot-welded directly, as shown in FIG. 6 (b), the side on which the terminal portions 2c, 2d are provided is positioned on the distal end side of the jacket (EFP tube 1). The direction of the thermistor 1 may be set as described above.
[0030]
If the direction of the thermistor 1 for molding the FEP tube 1 with a resin material (FEP) heated and melted is set in this manner, the connection portion (spot welded portion) with the coated conductors 3 and 3 is solidified by cooling. Since it is quickly fixed by the material (FEP), no extra stress is applied to the connection part having relatively low strength as described above. As a result, the lead terminals 2a and 2b, the core wires 4 and 4, and the connection portions thereof, which are relatively weak in strength, are less likely to cause problems such as disconnection, and defective products can be effectively prevented. If a part of the electric component such as the thermistor 1 has a weak part, the weak part may be arranged toward the front end of the FEP tube 5 to similarly damage the weak part. Can be prevented.
[0031]
In the above-described embodiment, the FEP tube 5 itself is heated and melted from the front end side to mold the thermistor 1 and its connection part. In this case, however, it is necessary to heat and melt the FEP tube 5 over a considerable length, depending on the diameter of the FEP tube 5. Moreover, it is difficult to accurately define the molding position of the thermistor 1 molded by the sealing portion 5a.
[0032]
In order to solve such a problem, for example, as shown in the schematic configuration of FIG. 7 (a), the FEP tube 5 is heated and melted together with the FEP tube 5 in advance on the tip of the FEP tube 5 and / or the upper part of a built-in component such as the thermistor 1. For this purpose, a thermoplastic resin mass 7 made of the same material as that of the FEP tube 5 may be fitted. At the same time, the mold position of the built-in component such as the thermistor 1 is defined by the thermoplastic resin mass 7.
[0033]
In this way, the thermoplastic resin lump 7 is heated and melted together with the FEP tube 5 to generate a molten resin material (FEP), and the resin material (FEP) is used to mold the thermistor 1 (built-in material). 5 can be reduced. Further, as shown in FIG. 7 (b), a resin portion 5b having a relatively large solid structure can be easily formed at the tip end of the jacket where the thermistor (built-in component) 1 is molded. Then, even if air bubbles are mixed into the resin portion 5b, or "shrinkage" occurs on the outer peripheral surface due to thermal contraction, the resin portion 5b is cut as an extra portion as shown in FIG. 7B, for example. Therefore, it is possible to easily improve the quality while leaving only a good resin mold portion.
[0034]
In particular, since the position of the thermistor (built-in body) 1 is regulated and the thermistor (built-in body) 1 is molded with a resin material (FEP) heated and melted, for example, the thermistor (built-in body) 1 from the front end of the jacket body When it is necessary to determine the mold position with high precision, it is possible to set the mold position with high precision simply by cutting off the resin portion 5b at a predetermined dimensional position. Therefore, even if the built-in component is not the thermistor 1 but requires mounting dimensional accuracy of a proximity switch (proximity sensor) or the like, the mold position can be determined with high accuracy. That is, in this case, the molding position of the built-in component (electric component) is roughly regulated by the above-described thermoplastic resin mass 7, and then the excess resin portion 5b may be cut off. Incidentally, the adjustment of the mold position of the built-in component (electric component) may be performed by adjusting the length of the thermoplastic resin mass 7 fitted to the tip of the FEP tube 5 in advance. As a result, it is possible to obtain a sealing structure in which the distance between the sensor surface and the distal end portion of the casing is easily determined with high accuracy.
[0035]
Note that the present invention is not limited to the above-described embodiment. Here, the tube 5 made of FEP is used as a general-purpose thermoplastic fluororesin, but the present invention can be similarly applied to a case where PFA (perfluoroalkoxy fluororesin) having higher heat resistance and environmental resistance than FEP is used. it can. However, in this case, since the heat melting temperature is further increased, it is needless to say that the built-in component (electric component) needs to have heat resistance of 320 ° C. or more, which is the melting temperature of PFA.
[0036]
In the embodiment, the case where the thermistor 1 is molded as an electric component is described as an example. However, the present invention can be similarly applied to a case where another electric component, for example, a proximity switch or the like is molded. In addition, the present invention can be variously modified and implemented without departing from the gist thereof.
[0037]
【The invention's effect】
As described above, according to the present invention, a heat-fused resin material is used while a hollow tube made of a general-purpose FEP and made of a thermoplastic resin having no heat shrinkage is used. Since the electric component housed in the hollow tube is molded by the method described above, it is possible to realize a simple, effective and inexpensive high-quality electric component sealing structure. In addition, using a cylindrical mold with a bottom in which the hollow tube is inserted, simply press the hollow tube toward the bottom of the mold and heat and melt it sequentially from its tip, so the work process is simple. In addition, a great effect can be obtained in practical use such that the manufacturing cost can be reduced.
[Brief description of the drawings]
FIG. 1 is an essential part cross-sectional view showing a schematic configuration of an electric component sealing structure according to a first embodiment of the present invention.
FIG. 2 is an essential part cross-sectional view showing a schematic configuration of an electric component sealing structure according to a second embodiment of the present invention.
FIG. 3 is a diagram illustrating a relationship with a mold for explaining a method of sealing an electric component according to an embodiment of the present invention.
FIG. 4 is a view showing a relationship with a mold for explaining a method for sealing an electric component according to another embodiment of the present invention.
FIG. 5 is an essential part cross-sectional view showing a schematic configuration of an electric component sealing structure according to a third embodiment of the present invention.
FIG. 6 is a view showing a main part of an electric component sealing structure according to a third embodiment of the present invention.
FIG. 7 is a view for explaining a method for sealing an electric component according to still another embodiment of the present invention.
[Explanation of symbols]
1 Thermistor (electric component)
3 Insulated wire 5 FEP tube (hollow tube)
5. Sealing part (solid part of resin material)
6 protective tube 7 thermoplastic resin lump 10 mold 11 cooling ring 12 liquid layer

Claims (5)

An electrical component electrically connected to the end of the conductive wire;
It consists of a hollow tube of a thermoplastic resin having no heat shrinkage, and derives the conducting wire from one end thereof, and the other end of all of the electric components housed inside the hollow tube and a part of the conducting wire. And an outer cover body that is melted and solidified by tightly covering the sealing member. The electrical component according to claim 1, wherein an electrical connection between the distal end of the conductive wire and the electrical component is covered with a protective tube made of a thermoplastic resin of the same material as the jacket. Structure. The sealing structure for an electric component according to claim 1, wherein the electric component is arranged such that an electric connection portion with the conductive wire is directed toward the other end of the jacket to be melted and solidified. An electric component electrically connected to the distal end of the conductive wire is arranged inside a hollow tube made of a thermoplastic resin having no heat shrinkage, and the conductive wire is led out from one end of the hollow tube. The other end of the hollow tube is fitted into the bottomed cylindrical mold,
While pressing the hollow tube toward the bottom of the mold, the other end of the hollow tube is heated and melted to tightly cover and solidify all of the electric components and a part of the conductive wire. Characteristic method of sealing electrical components. The electric component electrically connected to the tip of the conductive wire is arranged inside the hollow tube together with a thermoplastic resin mass of the same material as the hollow tube,
The sealing of an electric component according to claim 4, wherein the other end of the hollow tube and the thermoplastic resin mass are heated and melted to tightly cover and solidify all of the electric component and a part of the conductive wire. Stop method.

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