Patent Publication Number: US-2019195666-A1

Title: Rotary encoder and rotary encoder manufacturing method

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2017-249922 filed on Dec. 26, 2017, the contents of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a rotary encoder having a waterproof function and to a method of manufacturing this rotary encoder. 
     Description of the Related Art 
     International Publication No. 2012/108021 discloses a rotary encoder in which a base end of an insulating resin cover, in which a rotation encoding section and rotation amount detecting section are housed, is attached to a metal case of a motor via packing, and the opening portion of the other end of the insulating resin cover is sealed with a metal lid via packing. 
     SUMMARY OF THE INVENTION 
     In the art disclosed in International Publication No. 2012/108021, an attempt is made to make the insulating resin cover waterproof by attaching the metal case and the metal lid to the insulating resin cover via packing, but there is a problem that the user cannot check whether liquid has intruded into the insulating resin cover. 
     The present invention is created to solve the above problem, and it is an object of the present invention to provide a rotary encoder that enables the user to check whether liquid has intruded into the cover and also to provide a method of manufacturing this rotary encoder. 
     A first aspect of the present invention is a rotary encoder having a waterproof function, including a cover formed of a light transmissive resin; a housing to which the cover is attached; and a thermosetting resin that is provided between the cover and the housing, and hardened by being irradiated with laser light. 
     A second aspect of the present invention is a manufacturing method of a rotary encoder having a waterproof function, the rotary encoder including a cover formed of a light transmissive resin; a housing to which the cover is attached; and a thermosetting resin that is provided between the cover and the housing. The method includes the step of securing the cover to the housing by irradiating the thermosetting resin with laser light from the cover side to harden the thermosetting resin. 
     According to the present invention, it is possible to check whether liquid has intruded into the interior of the cover. 
     The above and other objects features and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which a preferred embodiment of the present invention is shown by way of illustrative example. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic cross-sectional view of a rotary encoder; 
         FIG. 2  is a schematic view of the rotary encoder as seen from a cover side; 
         FIG. 3  is an enlarged view of the circle A portion of  FIG. 1 ; 
         FIG. 4  is a schematic cross-sectional view of the rotary encoder; 
         FIG. 5  is a schematic view of the rotary encoder as seen from the cover side; 
         FIG. 6  is an enlarged view of the circle B portion of  FIG. 4 ; 
         FIG. 7  is a schematic cross-sectional view of the rotary encoder; and 
         FIG. 8  is a schematic cross-sectional view of the rotary encoder. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     First Embodiment 
     [Configuration of the Rotary Encoder] 
       FIG. 1  is a schematic cross-sectional view of a rotary encoder  10 .  FIG. 2  is a schematic view of the rotary encoder  10  as seen from a cover  12  side.  FIG. 3  is an enlarged view of the circle A portion of  FIG. 1 . 
     The rotary encoder  10  includes a housing  14  made of metal and a cover  12  made of a light transmissive resin. A rotating encoder board, a light emitting element, a light receiving element, and the like, which are not shown in the drawings, are housed within a space formed by the housing  14  and the cover  12 . 
     Thermosetting resin  18  is provided on a surface of the cover  12  facing the housing  14 , which is a flange portion  16 . The thermosetting resin  18  is provided to have a ring shape (see  FIG. 2 ) when the rotary encoder  10  is viewed from the cover  12  side. The thermosetting resin  18  is formed integrally with the cover  12  when the cover  12  is formed using injection molding. 
     In a state where the cover  12  is assembled with the housing  14 , the thermosetting resin  18  is irradiated with laser light from the cover  12  side, thereby applying heat to the thermosetting resin  18  and causing the thermosetting resin  18  to harden. In this way, the cover  12  can be secured to the housing  14 . 
     The thermosetting resin  18  includes a plurality of grooves  18   a  (see  FIG. 3 ) on a surface thereof that abuts on the housing  14 . Due to these grooves  18   a  formed in the thermosetting resin  18 , the thermosetting resin  18  has a labyrinth structure. 
     [Operational Effect] 
     The rotary encoder  10  is formed of electronic components, and therefore it is necessary to ensure sealing performance that prevents liquid from intruding into the inside of the cover  12 . However, there is a concern that the seal between the cover  12  and the housing  14  will degrade due to defects in the seal at the time of manufacturing, weakening of the seal over time, and the like. Conventionally, there is a problem that even when liquid has intruded into the cover  12 , it is impossible for the user to confirm that liquid has intruded into the cover  12 , and this delays the discovery of abnormalities in the rotary encoder  10 . 
     Therefore, in the rotary encoder  10  of the present embodiment, the cover  12  is formed of a light transmissive resin. Furthermore, the thermosetting resin  18  that is hardened by being irradiated with laser light is arranged between the cover  12  and the housing  14 . Since the cover  12  is formed of a light transmissive resin, when liquid has intruded into the rotary encoder  10 , the user can see and visually confirm that liquid has intruded into the rotary encoder  10 . Furthermore, by forming the cover  12  from a light transmissive resin, the adhesion between the cover  12  and the housing  14  and the seal between the cover  12  and the housing  14  can be easily achieved by irradiating the thermosetting resin  18  provided between the cover  12  and the housing  14  with laser light from the cover  12  side. 
     Furthermore, in the rotary encoder  10  of the present embodiment, the cover  12  and the thermosetting resin  18  are formed integrally using injection molding. Since the cover  12  and the thermosetting resin  18  are formed integrally, it is possible to reduce the number of components and also the number of steps when assembling the rotary encoder  10 . 
     Yet further, in the rotary encoder  10  of the present embodiment, the thermosetting resin  18  is provided with a labyrinth structure due to the grooves  18   a  being formed in the thermosetting resin  18 . In this way, it is possible to improve sealing performance for preventing intrusion of the liquid into the cover  12 . 
     Second Embodiment 
     [Configuration of Rotary Encoder] 
       FIG. 4  is a schematic cross-sectional view of the rotary encoder  10 .  FIG. 5  is a schematic view of the rotary encoder  10  as seen from the cover  12  side.  FIG. 6  is an enlarged view of the circle B portion of  FIG. 4 . In the second embodiment, the arrangement of the thermosetting resin  18  is different from in the first embodiment. In the following, configurations that are the same as in the first embodiment are given the same reference numerals, and descriptions thereof are omitted. 
     The thermosetting resin  18  is provided on the surface of the cover  12  facing the housing  14 , which is the flange portion  16 . The thermosetting resin  18  is provided to have a double-layered ring shape (see  FIG. 5 ) including thermosetting resin  18   b  on an outer circumferential side and thermosetting resin  18   c  on an inner circumferential side, when the rotary encoder  10  is viewed from the cover  12  side. In this way, two layers of seals are provided from the outer side to the inner side of the cover  12 . 
     In a state where the cover  12  is assembled with the housing  14 , the thermosetting resin  18  is irradiated with laser light from the cover  12  side, thereby applying heat to the thermosetting resin  18  and causing the thermosetting resin  18  to harden. In this way, the cover  12  can be secured to the housing  14 . 
     [Operational Effect] 
     In the rotary encoder  10  of the present embodiment, the thermosetting resin  18  is provided in two layers from the outer side to the inner side of the cover  12 . In this way, it is possible to improve the sealing performance between the cover  12  and the housing  14 . Furthermore, when liquid intrudes into the thermosetting resin  18   b  on the outer circumferential side, the liquid collects between the thermosetting resin  18   b  on the outer circumferential side and the thermosetting resin  18   c  on the inner circumferential side, and therefore it is possible for the user to see and visually confirm that the sealing performance of the thermosetting resin  18  has degraded before the liquid intrudes into the rotary encoder  10 . 
     Third Embodiment 
       FIG. 7  is a schematic cross-sectional view of the rotary encoder  10 . In the third embodiment, the arrangement of the thermosetting resin  18  is different from in the first embodiment. In the following, configurations that are the same as in the first embodiment are given the same reference numerals, and descriptions thereof are omitted. 
     A groove portion  20  with a ring shape is formed in a surface of the housing  14  where the cover  12  is attached. A convex portion  22  with a ring shape that engages with the groove portion  20  of the housing  14  is formed on the flange portion  16  of the cover  12 . 
     The thermosetting resin  18  is formed integrally with the cover  12  through injection molding, and is provided on the surface of the flange portion  16  of the cover  12  facing the housing  14  and on the side surface of the convex portion  22 . In a state where the cover  12  is assembled with the housing  14 , the thermosetting resin  18  is irradiated with laser light from the cover  12  side, thereby applying heat to the thermosetting resin  18  and causing the thermosetting resin  18  to harden. In this way, the cover  12  can be secured to the housing  14 . 
     [Operational Effect] 
     In the rotary encoder  10  of the present embodiment, the ring-shaped groove portion  20  is formed in the surface of the housing  14  where the cover  12  is attached, and the ring-shaped convex portion  22  that engages with the groove portion  20  of the housing  14  is formed on the flange portion  16  of the cover  12 . In this way, it is possible to increase the surface area across which the thermosetting resin  18  is provided between the cover  12  and the housing  14 , and therefore it is possible to firmly attach the cover  12  to the housing  14 . 
     [Modifications] 
       FIG. 8  is a schematic cross-sectional view of the rotary encoder  10 . In the third embodiment, the groove portion  20  is formed in the housing  14  and the convex portion  22  is formed on the cover  12 , but as shown in  FIG. 8 , a groove portion  24  may be formed in the cover  12  and a convex portion  26  may be formed on the housing  14 . In this case, the thermosetting resin  18  is provided on the surface of the flange portion  16  of the cover  12  facing the housing  14  and on the side surface of the groove portion  24 . 
     [Technical Concepts Obtained from Embodiments] 
     The following is a record of the technical concepts that can be understood from the embodiments described above. 
     The rotary encoder ( 10 ) having a waterproof function, includes a cover ( 12 ) formed of a light transmissive resin; a housing ( 14 ) to which the cover ( 12 ) is attached; and a thermosetting resin ( 18 ) that is provided between the cover ( 12 ) and the housing ( 14 ), and hardened by being irradiated with laser light. In this way, when liquid has intruded into the rotary encoder ( 10 ), the user can see and visually confirm that liquid has intruded into the rotary encoder ( 10 ). Furthermore, by radiating the laser light from the cover ( 12 ) side, it is possible to easily achieve the adhesion between the cover ( 12 ) and the housing ( 14 ) and the seal between the cover ( 12 ) and the housing ( 14 ). 
     In the rotary encoder ( 10 ) described above, the thermosetting resin ( 18 ) is formed integrally with the cover ( 12 ). In this way, it is possible to reduce the number of components and also the number of steps when assembling the rotary encoder ( 10 ). 
     In the rotary encoder ( 10 ) described above, the thermosetting resin ( 18 ) may have a labyrinth structure. In this way, it is possible to improve the sealing performance for preventing the liquid from intruding into the cover ( 12 ). 
     In the rotary encoder ( 10 ) described above, the housing ( 14 ) may include a groove portion ( 20 ) or convex portion ( 26 ) on a surface thereof where the cover ( 12 ) is attached, the cover ( 12 ) may include a convex portion ( 22 ) or groove portion ( 24 ) that engages with the groove portion ( 20 ) or the convex portion ( 26 ), and the thermosetting resin ( 18 ) may be provided on the convex portion ( 22 ) or groove portion ( 24 ) of the cover ( 12 ). In this way, the cover ( 12 ) and the housing ( 14 ) can be firmly adhered to each other. 
     In the rotary encoder ( 10 ) described above, the thermosetting resin ( 18 ) may be provided in at least two layers from the outer side to the inner side of the cover ( 12 ). In this way, the user can see and visually confirm that the sealing performance of the thermosetting resin ( 18 ) has degraded, before liquid intrudes into the rotary encoder ( 10 ). 
     There is a manufacturing method of the rotary encoder ( 10 ) with a waterproof function in which the rotary encoder ( 10 ) includes the cover ( 12 ) formed of a light transmissive resin; the housing ( 14 ) to which the cover ( 12 ) is attached; and the thermosetting resin ( 18 ) that is provided between the cover ( 12 ) and the housing ( 14 ) The method includes the step of securing the cover ( 12 ) to the housing ( 14 ) by irradiating the thermosetting resin ( 18 ) with laser light from the cover ( 12 ) side to harden the thermosetting resin ( 18 ). In this way, when liquid has intruded into the rotary encoder ( 10 ), the user can see and visually confirm that liquid has intruded into the rotary encoder ( 10 ). Furthermore, by radiating the laser light from the cover ( 12 ) side, it is possible to easily achieve the adhesion between the cover ( 12 ) and the housing ( 14 ) and the seal between the cover ( 12 ) and the housing ( 14 ). 
     The present invention is not particularly limited to the embodiments described above, and various modifications are possible without departing from the essence and gist of the present invention.