JP4003862B2 - Compact - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a molded article suitable for application to a proximity sensor or the like.
[0002]
[Prior art]
Many proximity switches, photoelectric switches, and the like as detection switches are provided with a light emitting element such as an LED in order to recognize an operation state. In order to make the LED of the chip or unit arranged inside the housing visible from the outside, a part of the housing is configured with a light-transmitting component that transmits light emitted from the LED, or as shown in FIG. It is necessary to house the LED 2 in the housing 1 formed of a resin having translucency. In particular, water resistance, environmental resistance, and the like are required in an environment where a liquid such as water is used or in a production line.
[0003]
[Problems to be solved by the invention]
In a structure in which a part of the casing is formed of a light-transmitting component, it is necessary to use a material having both light-transmitting properties and mechanical strength as the material of the light-transmitting component. It is desirable to use a thermoplastic resin for a reason that the molding time is short for a thermosetting resin, it can be handled by a normal injection molding machine, and there are many resin options and a resin can be selected according to product specifications. However, generally, a thermoplastic resin (amorphous resin) having a good translucency tends to have a low mechanical strength, and therefore the types of resins that can be selected as a material for the translucent component are limited. There is a problem that the degree of freedom of design is small. Further, since the number of components of the housing increases, there is a problem that the component cost and the assembly cost are high, or the request for further miniaturization cannot be met. In particular, for applications that require environmental resistance, foreign matter (water, gas, etc.) can be prevented from entering the housing from the boundary between the components that make up the majority of the housing and the translucent components that fit into it. It is difficult to seal to prevent over time, and even if it is possible, there is a problem that the cost is high.
[0004]
Furthermore, as shown in FIG. 8, a structure in which the entire casing is formed of a translucent resin can be assumed. However, as described above, generally a thermoplastic resin (amorphous resin) having good translucency is mechanical. Since the strength tends to be small, there is a problem that the degree of freedom in product design is small with respect to the mechanical strength and durability of the housing.
Furthermore, when at least a part of the housing is formed of a light-transmitting component as described above, there is a problem in that the amount of light emitted from the light emitting body (LED, miniature bulb, etc.) emitted from the housing is reduced. For example, the LED 2 is obtained by sealing a light emitting element made of a semiconductor with a sealing body made of a transparent epoxy resin (hereinafter also referred to as “sealing body 2”). The light emitted from the light emitting element is emitted to the outside using the sealing body 2 as a medium. At this time, since the medium around the sealing body 2 is air, the first time at the interface due to the difference in the refractive index of these media. Reflection occurs, and the amount of light L transmitted to the outside decreases. When the light L emitted from the light emitting surface 2a reaches the inner surface 1a of the housing 1, the second reflection occurs at the interface due to the difference in refractive index between air and the housing 1, and when the light L further reaches the outer surface 1b of the housing 1, the housing 1 The third reflection occurs at the interface due to the difference in refractive index between the air and the outside air, and the amount of transmitted light decreases. In this way, the light La reaching the outside has a light amount reduced by these three reflections. Further, most of the light (for example, Lb shown in FIG. 8) that has returned inward due to these reflections is repeatedly reflected and attenuated without leaving the housing 1. For this reason, the LED 2 viewed from the outside of the housing 1 has a problem of low brightness and poor visibility.
[0005]
The present invention has been made in view of the above-mentioned points. It is intended to improve visibility by increasing the amount of light transmitted from the built-in light emitter to the outside world to increase luminance, and to further improve durability. An object is to provide a molded article.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the molded article of claim 1 is a molded article having a solid integrated structure having through holes for attachment, and has a light-transmitting thermoplasticity in which the luminous body is sealed integrally. A primary molded body made of resin, a resin secondary molded body made of a resin having a larger elastic modulus than the primary molded body, covering the surface of the primary molded body to form an outer shell thereof, and the secondary molded body An opening that is opened in the molded body to expose a part of the primary molded body to release stress generated in the primary molded body, and in particular, the secondary molded body is formed in the axial direction of the through hole. A pair of plates sandwiching the body , connecting these plates together to protect the primary molded body and forming the opening between the pair of plates, and the plate body A reinforcing portion connected to form an inner peripheral surface of the through hole to prevent deformation of the through hole; Characterized in that it.
Preferably, it is desirable to use a milky white translucent elastomer as the light-transmitting thermoplastic resin forming the primary molded body.
[0007]
The opening also serves as an exit surface for light output from the light emitter and transmitted through the primary molded body.
According to such a configuration of the invention, by directly sealing the light emitter, a package having excellent environmental resistance is possible, and the refractive index of the light emitter and the thermoplastic resin directly sealing the light emitter is high. Since the difference is smaller than the difference in refractive index between the light emitter and air, it is difficult for light transmitted through the interface to attenuate. Furthermore, since the total number of interfaces between light media (translucent material, air) can be reduced, the light transmitted therethrough is not easily attenuated. Therefore, the transmission amount of the light emitted from the light emitter is increased, and the visibility from the outside is improved. Further, when an elastomer is used as the thermoplastic resin, the fluidity can be maintained at a low melting temperature, and therefore, it is difficult to exert a thermal and mechanical adverse effect on the light-emitting body that is an insert part during molding. In addition, since the elastic modulus is relatively small even at room temperature, the stress generated in the molded body during cooling after molding is small, and it is difficult to exert a mechanical adverse effect on the light-emitting body that is an insert part. Furthermore, by covering a part of the surface of the elastomer with a material having a large elastic modulus, it can be applied to applications that require mechanical strength.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
1 is a perspective view of a proximity sensor showing an embodiment of a molded body according to the present invention, FIG. 2 is a perspective view of a primary molded body of the proximity sensor shown in FIG. 1, and FIG. 3 is a primary molding of the proximity sensor shown in FIG. It is a perspective view of the secondary fabrication object which covers a body. The secondary molded body shown in FIG. 3 shows a state in which the primary molded body shown in FIG. 2 is removed from the proximity sensor shown in FIG. 1 for easy understanding of the shape.
[0009]
As shown in FIGS. 1 to 3, the proximity sensor (molded body) 10 includes a primary molded body 11 as a proximity sensor body, a secondary molded body 12 as an outer shell covering the primary molded body 11, and an electric wire 13.
The primary molded body 11 is intended to seal an insert part having a light emitter and transmit light from the light emitter to the outside, that is, to have visibility. The secondary molded body 12 is a proximity sensor. A molding resin that satisfies the specifications required for the sensor housing is selected for the purpose of housing the sensor 10, and sealing and housing of the sensor are realized without damaging the insert parts by two moldings. A solid integrated structure is adopted. Needless to say, a material that provides adhesion between the primary molding resin and the secondary molding resin is selected.
[0010]
As shown in FIG. 4, the primary molded body 11 is mounted with a core 21 around which a detection coil as an electric component or an electronic component is wound, a light emitting element (for example, LED) 22 as a light emitter, and other circuit elements 24. A circuit board 20 is inserted. Moreover, as for the electric wire 13, the terminal of the core wires 15-17 pulled out from the terminal 14a of the coating | covering material 14 is connected to the circuit board 20 (FIG. 6).
[0011]
The circuit board 20 and the end of the electric wire 13 are housed in a primary molding die (not shown), the terminal vicinity portion 14b of the coating 14 of the electric wire 13 is crimped, and the primary molding resin 25 is filled. . The primary molding resin 25 is filled in the gaps between the circuit board 20, the core 21, the light emitting element 22, and the circuit element 24, and becomes lower than the heat resistant temperature when it reaches the vicinity of these built-in components. Filled at melting temperature. For example, when a molten resin of 250 degrees Celsius is injected into the mold, the skin layer of the molten resin is cooled in the flow path and the core layer flows to the vicinity of the part while being kept at a high temperature. The skin layer has a temperature of about 90 degrees Celsius, and no problem arises even if the skin layer contacts a component having a heat resistant temperature of 100 degrees Celsius. Further, at this time, since the skin layer exhibits a heat insulating action, heat from the core layer kept at a high temperature does not reach the parts directly and does not have an adverse effect. In particular, polyester-based thermoplastic elastomers are translucent, have good flowability even in a relatively low temperature melt state, and can be injected at a relatively low pressure. It is possible to mold integrally without causing damage or displacement of the built-in parts. The light emitting surface 22a of the light emitting element 22 is in direct contact with the primary molding resin 25 and there is no air layer therebetween.
[0012]
Further, the primary molding resin 25 enters the inside from the terminal 14a where the covering material 14 is opened, and since the terminal vicinity portion 14b is crimped, the intrusion into the inside from the portion 14b is prevented, and the crimped portion 14b. To the terminal 14a and is spread out in a substantially trumpet shape. Of course, the primary molding resin 25 also enters between the core wires 15 to 17 in the terminal 14a. Thereby, the pulling strength (tensile strength) from the primary molded body 11 of the electric wire 13 is significantly improved, and the sealing performance of the insert part is ensured. In this way, the primary molded body 11 is molded.
[0013]
As shown in FIGS. 2 and 4, the primary molded body 11 has a substantially rectangular parallelepiped shape, and a screw mounting hole (step hole) 11 c is provided behind the circuit board 20 through the upper surface 11 a and the rear lower surface 11 b ′. Furthermore, a plurality of tapered holes 11d are provided from the upper surface 11a to the circuit board 20 in order to improve the adhesion with the secondary molded body 12 and prevent the circuit board 20 from being deformed. Grooves 11e and 11f are provided in the center of the front surface and a groove 11g is provided. The lower end of the groove 11g is connected to the front lower surface 11b.
[0014]
The central portion of the tip of the upper surface 11a of the primary molded body 11 protrudes above the light emitting element 22 to form a convex portion 11h. As a result, the light emitting element 22 is molded in close contact with the primary molded body 25 over the entire surface in the front, upper, and right and left directions of the light emitting surface 22a, and light emitted from the light emitting surface 22a directly passes through the primary molded resin 25 to the outside. That is, it is possible to go outside from the primary molded body 11.
[0015]
As shown in FIG. 4, the front lower surface 11 b of the primary molded body 11 is flush with the end surface (detection surface) 21 a of the core 21 fixed to the circuit board 20, and the rear portion is connected to the front lower surface 11 b. The lower surface 11b ′ is set to a predetermined height t from the front lower surface 11b. The front lower surface 11b serves as a reference surface (hereinafter referred to as “reference surface 11b”). Cylindrical protrusions 11i and 11i are provided on the left and right sides near the front end of the reference surface 11b, and the height thereof is set to the predetermined height t from the reference surface 11b.
[0016]
This primary molded body 11 is molded from a resin having translucency. As the resin having translucency, the above-mentioned polyester-based thermoplastic elastomer is an alloy material of an amorphous resin and a crystalline resin, has a milky white translucency , has translucency, and is elastic. Since the coefficient is small (for example, the longitudinal elastic modulus is 45 to 460 MPa) and the crack resistance is excellent, it is optimal for the implementation of the present invention.
[0017]
In addition, since this resin has a small longitudinal elastic modulus (Young's modulus), it absorbs the difference in linear expansion coefficient between the insert part and the secondary molded resin of the secondary molded body 12 described later, and the primary and secondary due to temperature changes. Decrease in adhesion between molding resins, generation of cracks, and the like can be suppressed. Moreover, since the glass transition point is not more than room temperature, the absolute value of the thermal stress applied to the insert part itself can be reduced.
[0018]
In addition to this, various thermoplastic elastomers are suitable as the transparent resin material, and engineering plastics such as polyarylate (PAR) and polycarbonate (PC) are also applicable depending on the conditions of the insert parts. When a translucent material is used, light from the light emitter is diffused and the entire molded body appears to emit light relatively uniformly. When a transparent material is used, the light emitter is directly observed, and reflected light on each surface (interface between the transparent resin and air) is also observed depending on the viewing position.
[0019]
Next, the primary molded body 11 is accommodated in a mold (not shown) for secondary molding, and secondary molding is performed from each gate provided facing the grooves 11e and 11f on both sides and the groove 11g on the front surface. Then, the molten molded resin 26 is pressurized and injected to form the secondary molded body 12. As the secondary molding resin 26, a hard resin is used in order to secure strength as an outer shell for protecting the primary molded body 11 and to obtain dimensional accuracy.
[0020]
The primary molded resin used for the primary molded body 11 has a small longitudinal elastic modulus but a large linear expansion coefficient. Therefore, in the sensor package, the secondary molded body 12 covers and restrains the entire outer peripheral surface of the primary molded body 11 with the secondary molded body 12. When the structure is adopted, all distortions caused by ambient temperature changes become the internal stress of the primary molded body 11, and a large stress is given to the insert part.
[0021]
Therefore, in the present invention, the secondary molded body 12 has a stress release structure that restricts only the portions that require mechanical strength and dimensional accuracy. That is, a predetermined region is opened with respect to the primary molded body 11, and the primary molded body is allowed to expand and contract in accordance with a change in ambient temperature at that portion, thereby generating an insert part of the primary molded body 11. It has a structure that can dissipate thermal stress to the outside. Typical secondary molding resins include PBT, ABS, and PC. These secondary molding resins 26 have a larger longitudinal elastic modulus than the primary molding resin 25 (for example, 2000 to 6000 MPa).
[0022]
As shown in FIGS. 3, 5, and 6, the secondary molded body 12 is a space formed between the upper plate 12 a that protects the upper surface 11 a of the primary molded body 11, the reference surface 11 b, and the end surface of each projection 11 i. The lower plate 12b that protects the end surface 21a of the core 21, the screw mounting reinforcing portion 12c that covers the inner peripheral surface of the screw mounting hole 11c and the stepped surface that contacts the screw head, and the holes 11d of the upper surface 11a are filled. The projection 12d that prevents deformation of the circuit board 20 such as warpage, and the upper plate 12a and the lower plate 12b that are filled in the grooves 11e on both sides are connected to each other and serve as a reinforcing portion that protects a part of the front side. The continuous portion 12e, the reinforcing portion 12f that fills the grooves 11f on both sides and protects a part of the rear side portion, the reinforcing portion 12g that fills the grooves 11e on the front surface and protects a part of the front surface, and the electric wire 13 Protective part which covers the terminal vicinity part 14b of the coating | covering material 14 Consisting of 2j and the like.
[0023]
The lower plate 12b of the secondary molded body 12 is formed in close contact with the reference surface 11b of the primary molded body 11, and the left and right projections 11i and 11i are accurately molded to a predetermined thickness t, and the lower surface is the rear portion. It is flush with the lower surface 11b ′. Each protrusion 11i prevents deformation due to the resin filled in the front portion of the upper surface 11a, and holds the space between the front lower surface 11b and the mold at a predetermined interval t. Thereby, the distance from the end surface (detection surface) 21a of the core 21 to the lower surface of the lower plate 12b is accurately set to the predetermined height t (FIG. 5), and variations in the operating distance of the proximity sensor 10 are suppressed. Further, the lower plate 12b is tightly formed on the reference surface 11b to ensure sealing performance, and the end surface 21a of the core 21 is sealed in a liquid-tight manner.
[0024]
Further, as shown in FIGS. 5 and 6, the strength is ensured by covering the inner peripheral surface and the step surface of the screw mounting hole 11c with the reinforcing portion 12c of the secondary molded body 12, and the lower surface of the screw head when mounting with a screw. The proximity sensor 10 is prevented from being deformed or damaged by the contact portion and the threaded shaft portion and the like, and the core wires 15 to 17 of the electric wire 13 are protected, and sealing performance is also ensured.
[0025]
In this way, the proximity sensor 10 is a structure that satisfies the sealing, strength, and translucency functions required for sensor sealing by the primary molded body 11 and the secondary molded body 12. By adopting such a structure, the proximity sensor 10 can be further reduced in size.
As shown in FIG. 7, the light L emitted from the light emitting surface 22a of the light emitting element 22 is directly transmitted through the primary molding resin 25 and exits from the primary molded body 11 as transmitted light La, and a part of the light L is from the outside (air). Is reflected by the boundary surface 11 s and returns to the resin 25 (inside the primary molded body 11) as reflected light Lb. However, when the light L emitted from the light emitting surface 22a travels directly from the resin 25 to the air (outside) and when it travels through the air to the resin 25, the reflectance at the boundary surface is greatly different, and the reflectance at the boundary surface 11s is different. Is much smaller than the reflectance on the inner surface 1a of the resin (casing 1) in the conventional structure shown in FIG. Therefore, most of the light L emitted from the light emitting surface 22a travels to the outside as transmitted light La, and the reflected light Lb is small.
[0026]
Furthermore, most of the reflected light Lb again travels to the outside as transmitted light Lc, and the reflected light Ld becomes very small. Therefore, most of the light L emitted from the light emitting surface 22a of the light emitting element 22 comes out of the primary molded body 11, and the amount of transmitted light increases and the luminance increases. Moreover, the brightness | luminance of the wide range covering the front surface of the primary molded object 11 surrounding the light emission surface 22a, the convex part 11h, and both front side surfaces becomes high. Thereby, visual recognition by the light emitting element 22 is possible in a wide range of the proximity sensor 10.
[0027]
Further, since the luminance of the primary molded body 11 is increased over a wide range, the degree of freedom of arrangement of the light emitting elements 22 is increased, setting is easy, and the sensor can be miniaturized. In addition, a sensor package capable of improving water resistance and environmental resistance becomes possible.
[0028]
【The invention's effect】
As described above, according to the configuration of the present invention, a package excellent in productivity and environmental resistance can be obtained by directly sealing a light emitter with a thermoplastic resin, and light emitted from the light emitter can be obtained. The amount of transmitted light increases and visibility from the outside improves. In addition, when a thermoplastic elastomer is used as the thermoplastic resin, it is difficult to exert a thermal and mechanical adverse effect on the light-emitting body that is an insert part during molding, and the stress generated inside the molded body during cooling after molding is small. Therefore, it is difficult to exert a mechanical adverse effect on the light emitting body that is the insert part. Furthermore, if a part of the surface of the thermoplastic elastomer is covered with a material having a large elastic modulus, it can be applied to applications requiring mechanical strength.
[Brief description of the drawings]
FIG. 1 is a perspective view of a proximity sensor, showing a first embodiment of a molded body according to the present invention.
FIG. 2 is a perspective view of a primary molded body of the proximity sensor shown in FIG.
3 is a perspective view of a secondary molded body covering the primary molded body of the proximity sensor shown in FIG. 2, and shows a state where the primary molded body shown in FIG. 2 is removed from the proximity sensor shown in FIG.
4 is a cross-sectional view taken along arrows IV-IV of the primary molded body shown in FIG.
FIG. 5 is a cross-sectional view of the proximity sensor shown in FIG. 1 along the arrow VV.
6 is a sectional view taken along arrows VI-VI of the proximity sensor shown in FIG.
7 is an explanatory diagram of an optical path of light emitted from a light emitting element of the proximity sensor shown in FIG. 4. FIG.
FIG. 8 is an explanatory diagram of an optical path of light emitted from a light emitter housed in a housing of a conventional detection switch.
[Explanation of symbols]
10 Proximity sensor (molded product)
11 Primary molded body 12 Secondary molded body 13 Electric wire 20 Circuit board 21 Core 22 Light emitting element (light emitting body)
24 Circuit element 25 Primary molding resin 26 Secondary molding resin

Claims (3)

A molded body having a solid integrated structure having through holes for mounting, and a primary molded body made of a thermoplastic resin having a translucent property in which a light emitting body is sealed in a solid body, and more elastic than the primary molded body A resin secondary molded body made of a resin having a large coefficient and covering the surface of the primary molded body to form an outer shell thereof, and an opening in the secondary molded body to expose a part of the primary molded body An opening for releasing stress generated in the primary molded body,
The secondary molded body includes a pair of plate bodies sandwiching the primary molded body in the axial direction of the through-holes, and interconnecting these plate bodies to protect the primary molded body and the pair of plate bodies. A molding comprising: a continuous portion having the opening formed therebetween; and a reinforcing portion connected to the plate body to form an inner peripheral surface of the through hole to prevent deformation of the through hole. body.   The molded article according to claim 1, wherein the light-transmitting thermoplastic resin forming the primary molded article is a milky white translucent elastomer.   The molded body according to claim 1, wherein the opening forms an emission surface of light output from the light emitter and transmitted through the primary molded body.

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