JP4321506B2 - Method for manufacturing photoelectric sensor - Google Patents

Description

The present invention relates to a method for manufacturing a photoelectric sensor including a light projecting / receiving unit and a signal processing unit.

  Conventionally, a photoelectric sensor including a light projecting / receiving unit and a signal processing unit has been used in a wide range of fields. The photoelectric sensor includes a light projecting / receiving unit, a signal processing unit, a lens, and the like, and these are usually housed in a rectangular casing. As the casing, a resin molded product that can be easily molded into a complicated shape is generally used.

However, in recent years, high chemical resistance and water resistance are sometimes required for photoelectric sensors used in production facilities. In order to realize such high chemical resistance and water resistance, a photoelectric sensor having a casing made of metal has been proposed (for example, Patent Document 1 (Japanese Patent Laid-Open No. Hei 8-241657)). A metal casing used for a conventional photoelectric sensor is manufactured by casting using aluminum or zinc as a material.
JP-A-8-241657

  Photoelectric sensors used in production facilities and the like are required to be downsized in addition to high chemical resistance and water resistance. However, in the conventional manufacturing by casting, it is necessary to make all the parts of the casing thicker than a predetermined thickness. This is because in the case of casting, voids (so-called “nests”) are generated unless a certain thickness is secured.

  As a result, the thickness of the conventional metal casing has to be relatively thick, and the metal casing can only be used for a relatively large photoelectric sensor. For this reason, it has been impossible to manufacture a small photoelectric sensor housing from metal. Thereby, high chemical resistance and water resistance have not been realized in a small photoelectric sensor.

  On the other hand, the proximity sensor case that detects magnetism or the like is generally formed in a columnar shape, but there are proximity sensors that use a metal case even if they are relatively small. The metal casing of such a proximity sensor is manufactured by cutting. If the casing is cylindrical like a proximity sensor, it is relatively easy to manufacture by cutting. However, manufacturing a rectangular photoelectric sensor casing by cutting is unrealistic in terms of manufacturing man-hours and manufacturing costs. Is.

The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a method for manufacturing a photoelectric sensor including a metal housing that can be configured to be relatively small.

  According to a photoelectric sensor based on the present invention, a photoelectric sensor comprising a mounting substrate on which components constituting the light projecting / receiving unit and the signal processing unit are mounted, and a housing in which at least the mounting substrate and the lens are stored. The housing includes a metal housing body provided with an opening for light projection and reception, and a translucent plate disposed in the opening. It has a rectangular outer shape and is manufactured by metal injection molding.

  According to this configuration, since the casing is formed by metal injection molding, a substantially square casing of the photoelectric sensor can be manufactured with high productivity, and the thickness of the casing should be relatively thin. Therefore, a relatively small casing can be made of metal.

  In the photoelectric sensor, an arch-shaped reinforcing piece may be provided along at least a part of the inner side surface of the opening. In metal injection molding, a sintering process is essential, but by providing an arch-shaped reinforcing piece in the opening, deformation of the opening in the sintering process can be suppressed.

  In the photoelectric sensor, the housing may have a connector portion protruding from the housing body, and the connector portion may be integrally formed with the housing body by metal injection molding. Unlike casting, it is possible to easily manufacture a housing having a complicated shape by using metal injection molding. Therefore, the connector part is also molded integrally with the housing body, so that the fixing strength of the connector part is improved and there is no seam between the housing body and the connector part. Sex is obtained.

  In the photoelectric sensor, the casing main body may have a thickness of a portion constituting at least a part of a main surface constituting the outer surface thereof of 1 mm or less. As described above, by using metal injection molding, the casing can be formed thin. As a result, a casing having a thickness of 1 mm or less, which has been impossible with casting, is manufactured. can do.

  In the photoelectric sensor, the material of the housing body may be stainless steel. Stainless steel is known to be excellent in chemical resistance and water resistance, but it is known that it is difficult to process such as cutting because it is hard, but it can be molded in the same way as other metals by using metal injection molding. is there. Thereby, the stainless steel housing excellent in chemical resistance and water resistance can be manufactured at a relatively low cost.

  ADVANTAGE OF THE INVENTION According to this invention, the photoelectric sensor provided with the metal housing | casing which can be comprised comparatively small can be provided.

  Hereinafter, the structure of the photoelectric sensor in each embodiment based on the present invention will be described with reference to the drawings. In each embodiment, the same or corresponding parts are denoted by the same reference numerals, and redundant description will not be repeated.

(Embodiment 1)
Hereinafter, a first embodiment according to the present invention will be described with reference to FIGS. FIG. 1 is an exploded perspective view of the photoelectric sensor in the present embodiment, FIG. 2 is a flowchart showing a manufacturing process of the housing body of the photoelectric sensor in the present embodiment, and FIG. FIG. 4 is a front view of the housing body of the present embodiment, and FIG. 5 is a cross-sectional view of the housing body of the present embodiment.

  First, the structure of the photoelectric sensor will be described with reference to FIG. The photoelectric sensor 1 according to the present embodiment includes a light emitting / receiving unit mounting substrate 11 on which an electronic component constituting a light projecting / receiving unit such as a semiconductor laser and a light receiving element, a semiconductor device constituting a signal processing unit, and the like are mounted. The input / output mounting board 15 on which electronic parts such as semiconductor devices constituting the signal output section and the signal output section are mounted, and the light emitting / receiving section mounting board 11, the input / output mounting board 15, the lens 13, and the like are accommodated. A housing 51 is provided. The casing 51 includes a metal casing main body 52 provided with an opening 55 for light projection and reception, and a translucent plate 71 disposed in the opening 55.

  The light emitting / receiving unit mounting substrate 11 and the pair of lenses 13 are connected by a bracket 14. The light emitting / receiving unit mounting substrate 11 and the pair of lenses 13 connected by the bracket 14 are held by a resin holder 17 and housed in the internal space of the housing body 52.

  Similarly, the input / output mounting board 15 is also held by the holder 17 and housed in the housing body 52. A wiring board 19 for inputting / outputting signals to / from an operation panel 35 to be described later is provided. The wiring board 19 is also held by the holder 17 and housed in the housing body 52.

  A shield 21 made of a metal plate is disposed outside the wiring substrate 19, and an insulating sheet 23 is disposed outside the shield 21. A plate-like lid 31 made of the same metal as that of the casing main body 52 is disposed in an opening formed on the side surface of the casing main body 52 for inserting components therein. The outer periphery of the lid body 31 is attached to the housing body 52 so that the watertightness between the housing body 52 and the lid body 31 is maintained.

  A translucent plate 71 is attached to the opening 55 on the front side of the housing main body 52, and the translucent plate 71 is made of a colored transparent synthetic resin. Are different materials. Although the coefficient of thermal expansion is greatly different between the metal and the synthetic resin, the outer periphery of the translucent plate 71 can be secured so that the water-tightness between the two can be ensured even when the two behave differently due to temperature changes. Is bonded to the casing body 52 with an elastic adhesive. As the elastic adhesive, one made of modified silicon can be used.

  An opening is also provided on the upper surface of the housing main body 52, and a resin operation panel 35 incorporating a display unit composed of LEDs, a sensitivity adjustment volume, an operation changeover switch, and the like is attached thereto. These display unit, sensitivity adjustment volume, and the like may be omitted depending on the application. When the operation panel 35 itself is unnecessary, an opening for attaching the operation panel 35 of the housing body 52 may not be provided.

  As shown in FIGS. 1 and 3 to 5, the housing body 52 has a complicated shape. The reason why the housing body 52 having such a complicated shape can be made of metal is because the housing body 52 is manufactured by metal injection molding. Metal injection molding (MIM), also called metal powder injection molding, is a mixture of metal powder and binder mixed and kneaded, injected into a mold, and then sintered to form metal parts. It is a manufacturing method to manufacture. JP-A-6-122902 discloses an example of such metal injection molding.

  Next, the process of manufacturing the housing body 52 by metal injection molding will be described with reference to FIG. Before the process shown in FIG. 2, a mold used for metal injection molding is manufactured in advance. At this time, the size of the mold is set to be about 120% of the design dimension (dimension of the completed housing).

  First, the process proceeds to the kneading step. In the kneading step, a metal powder used as a material for the housing body and a resin material powder called a binder are mixed at a constant ratio and kneaded by applying heat. As the metal powder, it is preferable to use stainless steel powder from the viewpoint of improving the chemical resistance and water resistance of the completed casing. In addition, it is particularly preferable to use SUS316 among stainless steels because of its particularly excellent chemical resistance.

  Although SUS316 is excellent in chemical resistance and the like, it is a material that is difficult to machine. By using metal injection molding, a molded body can be manufactured in the same process as other metals. However, the metal powder is not limited to stainless steel powder, and an appropriate metal may be used according to the use of the photoelectric sensor.

  As the binder, a polymer material such as polyethylene or polyamide is generally used. A wax-based resin can also be used as the binder. The mixing ratio between the metal powder and the binder is generally about 6: 4.

  Next, the process proceeds to the granulation process. In the granulation step, the mixture is granulated so that the mixture of metal powder and binder can be supplied to the injection molding machine.

  Next, the process proceeds to an injection molding process. In the injection molding process, the mixed material granulated in the granulation process is injected into a mold using an injection molding machine and molded inside the mold to generate an intermediate molded body.

  Next, it progresses to a degreasing process. In the degreasing step, the intermediate molded body is placed in a degreasing furnace and heated at about 600 ° C. for about 24 to 48 hours to remove the binder (resin) component inside the intermediate molded body. In the degreasing process, in addition to heat degreasing to decompose and volatilize the binder with heat as described above, extraction degreasing to elute the binder with an organic solvent, etc., and photolytic degreasing to lower the molecular weight of the binder by irradiating ultraviolet rays Can also be used.

  Next, the process proceeds to the sintering process. In the sintering step, the molded body from which the binder component has been removed in the degreasing step is placed in a sintering furnace and sintered at a high temperature of about 1000 ° C. to 1200 ° C. for about 24 hours to obtain a metal body having a predetermined density.

  Next, the process proceeds to a post-processing step. Finally, as a post-processing step, a metal housing body is completed by performing a polishing process or the like.

  By using such metal injection molding, a metal material that is difficult to machine can be used as the material of the housing body. Further, in metal injection molding, a relatively thin molded body can be formed, so that the housing can be downsized. Furthermore, since an intermediate molded body is formed by injecting a mixture of metal powder and a binder into a mold, a molded body having a complicated shape can be formed in the same manner as in resin molding.

  Subsequently, the structure of the casing body 52 manufactured in such a process will be described in more detail. In the embodiment of the present embodiment, the casing main body 52 is configured in a square shape. Such a non-cylindrical casing is not easy to manufacture by machining such as cutting as described above, and is practically impossible particularly when a hard metal such as SUS316 is used. close. However, a rectangular casing can be easily manufactured by using metal injection molding. Note that the substantially square shape does not necessarily require that all the surfaces are configured as flat surfaces, and includes shapes in which a part is configured with a curved surface or the like.

  As shown in FIG. 3, the casing main body 52 of the present embodiment is provided with a cylindrical connector portion 57 protruding outward. The connector portion 57 is provided with electrodes therein and connected to a cable. The connector portion 57 is molded by the above-described metal injection molding simultaneously with the housing main body 52. By using metal injection molding, even such complicated shapes can be molded with metal.

  By simultaneously molding, the connector part 57 is molded integrally with the other parts of the housing main body 52 seamlessly. Thereby, the connection strength of the connector part 57 to the housing body 52 is improved, and the water resistance between the connector part 57 and the connection part of the housing body 52 can be improved.

  In the present embodiment, as shown in FIG. 3, a screw hole 53 is provided on the side surface of the housing body 52. The screw hole 53 is used when the photoelectric sensor 1 is attached to a manufacturing apparatus or the like. In a conventional metal casing made of aluminum or the like, there is a problem that if the screw is screwed into the screw hole 53 with a strong tightening torque, the metal constituting the casing is soft and the screw thread is crushed. there were. In order to avoid this, the tightening operation of the screw had to be performed while always controlling the tightening torque. By using metal injection molding, the housing main body 52 can be configured by a hard metal such as stainless steel. Therefore, by using such a hard metal, a screw hole that can withstand strong tightening torque can be configured. . Thereby, the management of the tightening torque at the time of tightening the screw is virtually unnecessary.

  As shown in FIG. 4, the housing body 52 of the present embodiment is provided with an opening 55. The opening 55 is for light projection and reception, and is an essential component in the photoelectric sensor 1. As a problem using the above metal injection molding, there is a deformation of the intermediate molded body in the sintering process. In particular, deformation at the top of the opening 55, which is an essential configuration, becomes a problem. Therefore, in the present embodiment, as shown in FIG. 4, an arch-shaped rib 56 is provided on the upper portion of the opening 55 to suppress the sag of the upper portion of the opening during sintering.

  Moreover, the thickness of the housing body 52 can be reduced by using metal injection molding as described above. Therefore, in the case main body 52 of the present embodiment, as shown in FIG. 5, the thickness of the side surface 52 a is formed to 1.1 mm, and the thickness of the concave surface 52 b in the center is set to 0. It is formed to 6 mm. By using metal injection molding, it is possible to form such a thin casing that could not be realized by conventional casting. Thereby, the small housing body 52 can be manufactured while keeping the internal capacity the same.

(Embodiment 2)
Next, a second embodiment will be described with reference to FIG. FIG. 6 is a perspective view showing a structure for attaching a cable to the housing body in the present embodiment.

  In the housing main body 52 of the present embodiment, the connector portion 57 as in the first embodiment is not provided, and the cable 81 is fixed to the housing main body 52 by the fixing bracket 59. The fixing bracket 59 has a through hole, and the cable 81 is inserted into the through hole. Both side portions of the fixing bracket 59 are bent toward the housing body 52, and an engaged hole 59b is provided in the bent portion 59a.

  The housing body 52 is provided with a recess 61 to which the fixing bracket 59 is attached, and a pair of wedge-shaped engaging projections 62 are provided on both sides thereof. When the fixing bracket 59 is fixed to the housing main body 52, the fixing fitting 59 is inserted into the recess 61 so that the engaged hole 59 b of the fixing bracket 59 and the engaging protrusion 62 of the casing main body 52 are engaged. Both are fixed.

  However, when the fixing bracket 59 is made of a material having weak spring properties such as SUS316, when the fixing bracket 59 is inserted into the recess 61, the bent portion 59a of the fixing bracket 59 spread by the engagement protrusion 62 remains expanded. , Do not restore to the original shape. In such a case, after the fixing bracket 59 is inserted, the bent portion 59a is pressed from the side and caulked so that the engagement protrusion 62 and the engaged hole 59b are securely engaged, and the fixing bracket 59 is The housing main body 52 can be completely fixed.

  In addition, the said embodiment disclosed this time is an illustration in all the points, Comprising: It does not become the basis of limited interpretation. Therefore, the technical scope of the present invention is not interpreted only by the above-described embodiments, but is defined based on the description of the claims. Further, all modifications within the meaning and scope equivalent to the scope of the claims are included.

It is a disassembled perspective view of the photoelectric sensor in Embodiment 1 based on this invention. It is a flowchart which shows the manufacturing process of the housing body of the photoelectric sensor in Embodiment 1 based on this invention. It is a perspective view of the housing body in Embodiment 1 based on this invention. It is a front view of the housing body in the first embodiment based on the present invention. It is sectional drawing of the housing body in Embodiment 1 based on this invention. It is a perspective view which shows the attachment structure of the cable to the housing body in Embodiment 2 based on this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Photoelectric sensor, 11 Emitter / receiver mounting board, 13 Lens, 15 Input / output mounting board, 19 Wiring board, 31 Cover, 51 Housing, 52 Housing body, 55 Opening, 56 Rib, 57 Connector 71 Translucent plate.

Claims (3)

A mounting substrate on which components constituting the light projecting / receiving unit and the signal processing unit are mounted; and a housing in which at least the mounting substrate and the lens are stored;
The casing has a substantially square outer shape, and is formed of a metal having a first opening for light projection and reception on the front surface and a second opening for inserting a component inside on the side surface. A method for manufacturing a photoelectric sensor, comprising: a housing body; a transparent resin-made translucent plate disposed in the first opening; and a plate-shaped metal lid attached to the second opening. Because
By mixing and kneading the case body with a mixture of stainless steel powder and a binder, using an injection molding machine, the mold is injected, and the binder is degreased and sintered by molding. Manufacturing process;
The mounting substrate and the lens are connected by a bracket, the bracket and the mounting substrate and the lens connected by the bracket are held by a holder, and the lens is directed to the first opening, and A step of adhering the metal lid to the second opening after being housed in the internal space of the housing body with the insulating sheet disposed on the inner side of the lid disposed;
Adhering the transparent resin translucent plate to the first opening of the casing body with an elastic adhesive. The arch-shaped reinforcing piece is provided along at least a part of the inner surface of the first opening so as to have a strength capable of suppressing sagging during sintering. The manufacturing method of the photoelectric sensor of description.   The casing main body has a main surface that is 1.1 mm thick and has no opening, and a recess is provided in the center of the main surface, and the thickness of the portion is 0.6 mm. The manufacturing method of the photoelectric sensor of Claim 1 or 2.

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