Patent Publication Number: US-2022230821-A1

Title: Push switch

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This U.S. non-provisional application is a continuation of PCT International Application PCT/JP2020/011771 filed on Mar. 17, 2020 and designated the U.S., which is based on and claims priority to Japanese Patent Applications No. 2019-159864 filed Sep. 2, 2019, with the Japan Patent Office. The entire contents of these applications are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a push switch. 
     2. Description of the Related Art 
     Patent Document 1 relates to a push switch and discloses a technique in which a pushing member disposed between a cover sheet and a movable contact member presses a top portion of the movable contact member to deform the movable contact member, thereby allowing the movable contact member to contact a central contact portion. 
     [Patent Document 1] Japanese Patent Application Laid-Open No. 2018-6021 
     SUMMARY OF THE INVENTION 
     However, in the technique disclosed in Patent Document 1, both sides of the movable contact member are side-cut. Therefore, if an operational load of the movable contact member is increased without increasing the size of the movable contact member, the stress amplitude of both sides of the movable contact member increases, and cracks are likely to occur on both sides of the movable contact member. 
     A push switch of an aspect of the invention contains a case including a housing space having an upper opening and including fixed contacts disposed on a bottom of the housing space, a movable contact member disposed in the housing space configured to deform in response to receiving pressure applied from above, and contacting the fixed contacts upon defoming in response to the received pressure, and a pushing member disposed on the movable contact member and configured to transmit the received pressure to the movable contact member, wherein the movable contact member includes a pair of first linear edges, wherein the pushing member includes a plurality of projecting pressing portions disposed on a bottom surface of the pushing member facing the movable contact member, and wherein the plurality of pressing portions is disposed on the bottom surface at positions not overlapping a straight line that passes through a center of the movable contact member and intersecting each of the pair of first linear edges. 
     According to one embodiment, an operational load of the movable contact member can be increased while suppressing the increase in stress amplitude on both sides of the movable contact member. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a push switch according to one embodiment; 
         FIG. 2  is an exploded perspective view of a push switch according to one embodiment; 
         FIG. 3  is a perspective view of a bottom surface side of a pushing member according to one embodiment; 
         FIG. 4  is a planar view of a pressing position of a metal contact by the pushing member according to one embodiment; 
         FIG. 5A  is a diagram illustrating a relationship between distances and operational loads in the push switch according to one embodiment; 
         FIG. 5B  is a diagram illustrating a relationship between the distances and stress amplitudes in the push switch according to one embodiment; 
         FIG. 6A  is a diagram illustrating a relationship between lengths and the operational loads in the push switch according to one embodiment; 
         FIG. 6B  is a diagram illustrating a relationship between the lengths and stress amplitudes in the push switch according to one embodiment; 
         FIG. 7A  is a diagram illustrating a relationship between angles and the operational loads in the push switch according to one embodiment; 
         FIG. 7B  is a diagram illustrating a relationship between the angles and the stress amplitudes in the push switch according to one embodiment; 
         FIG. 8  is a diagram illustrating a first modification example of a pushing member according to one embodiment; 
         FIG. 9  is a diagram illustrating a second modification example of a pushing member according to one embodiment; 
         FIG. 10  is a diagram illustrating a comparison of the operational loads of the push switch according to one embodiment and that of conventional push switches; 
         FIG. 11  is a diagram illustrating a comparison of the stress amplitudes of the push switch according to one embodiment and that of the conventional push switches; 
         FIG. 12  is a diagram illustrating a first example of a pushing member used in the conventional push switch; and 
         FIG. 13  is a diagram illustrating a second example of a pushing member used in the conventional push switch. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereinafter, one embodiment will be described with reference to the drawings. In the following description, for convenience, the Z-axis direction in the drawing is vertically oriented. In addition, the Y-axis direction in the drawing is the left-right direction. In addition, the X-axis direction in the drawings is the front-rear direction. 
     [Outline of Push Switch  100 ] 
       FIG. 1  is a perspective view of a push switch  100  according to an embodiment. As illustrated in  FIG. 1 , the push switch  100  includes a case  110  having a rectangular shape that is thin in the Z-axis direction. A cover sheet  140  is provided on the upper surface of the case  110 . At the center of the cover sheet  140  is an upwardly projecting dome-like operating member  141 . 
     The push switch  100  can be switched between an on state and an off state by pressing the operating member  141  downward. Specifically, the push switch  100  is turned off when the operating member  141  is not pressed, and a first fixed contact  111  (see  FIG. 2 ) and a second fixed contact  112  (see  FIG. 2 ) provided inside the case  110  are turned off. 
     Meanwhile, the push switch  100  is turned on when the operating member  141  is pressed downward, and the first fixed contact  111  and the second fixed contact  112  are connected to each other through a metal contact  120  (see  FIG. 2 ). When the push switch  100  is released from the pressing operation of the operating member  141 , the push switch  100  automatically returns to its original state due to the resilient restoring force of the metal contact  120 . This automatically turns off the push switch  100 . 
     [Configuration of Push Switch  100 ] 
       FIG. 2  is an exploded perspective view of the push switch  100  according to an embodiment. As illustrated in  FIG. 2 , the push switch  100  is configured with the case  110 , metal contact  120 , pushing member  130 , and cover sheet  140 , starting from the bottom of the drawing. 
     The case  110  is a container-like member having a rectangular shape. The case  110  is a generally rectangular shape with a longitudinal direction in the X-axis direction and a shorter direction in the Y-axis direction in a planar view from above. The case  110  is formed with an opening in the upper portion of a housing space  110 A. The housing space  110 A is a generally rectangular shape with a longitudinal direction in the X-axis direction and a shorter direction in the Y-axis direction in a planar view from above. Within the housing space  110 A is the metal contact  120  and the pushing member  130 . For example, the case  110  is formed by insert molding using a relatively rigid insulating material (for example, a rigid resin and the like). 
     A bottom portion of the housing space  110 A is provided with four first fixed contacts  111  and three second fixed contacts  112 . The four first fixed contacts  111  are disposed at each of the four corners at the bottom of the housing space  110 A. Each of the four first fixed contacts  111  contacts the periphery of the metal contact  120  and is electrically connected to the metal contact  120  by positioning the metal contact  120  in the housing space  110 A. The three second fixed contacts  112  are disposed in the center of the bottom portion of the housing space  110 A. The three second fixed contacts  112  are electrically connected to the metal contact  120  by contacting the center (for example, the back portion of the top) of the metal contact  120  when the top of the metal contact  120  is deformed in a concave manner. Thereby the three second fixed contacts and the metal contact  120  are electrically connected, and are conductive with each of the four first fixed contacts  111  through the metal contact  120 . For example, the first fixed contacts  111  and the second fixed contacts  112  are formed by processing a metal plate. 
     The metal contact  120  is an example of a “movable contact member”. The metal contact  120  is a dome-shaped member formed from a thin metal plate. The metal contact  120  is disposed within the housing space  110 A of the case  110 . 
     The outer shape of the metal contact  120  is configured with a pair of first curved edges  122  on the front and rear sides and a pair of first linear edges  123  on the left and right sides in a planar view from above. The first curved edge  122  is a portion that extends curvedly along a circumferential portion having a predetermined radius. The first linear edge  123  is a portion that extends linearly along the X-axis direction. The metal contact  120  is shaped into an outer shape having a pair of first curved edges  122  and a pair of first linear edges  123  by being side-cut linearly along the X-axis of the left and right sides of the metal contact  120  relative to a member having a circular shape in a planar view from above. That is, the metal contact  120  has a longitudinal shape in which the X-axis direction is the longitudinal direction and the Y-axis direction is the shorter direction. 
     The metal contact  120  contacts with each of the four first fixed contacts  111  at the bottom of the housing space  110 A and is electrically connected to each of the four first fixed contacts  111  at its outer periphery. When the operating member  141  is pressed, the top  121  of the metal contact  120  is pressed downwardly by the pushing member  130 , and abruptly deforms (inverts) the top  121  in a concave shape when it exceeds a predetermined operating load. 
     Thus, the back portion of the top  121  in the metal contact  120  contacts the second fixed contacts  112  disposed on the bottom of the housing space  110 A, and is electrically connected to the second fixed contacts  112 . The metal contact  120  returns to its original projecting shape by elastic force when released from the pressing force from the pushing member  130 . 
     The pushing member  130  is mounted on the top  121  (for example, center part) of the metal contact  120 . The pushing member  130  is formed of a resin material such as PET and the like. The upper surface of the pushing member  130  is upwardly projecting dome-shaped with a central top  131 . The pushing member  130  is bonded by any adhesive methods (for example, laser welding and the like) with respect to the back of a top  141 A of the operating member  141  of the cover sheet  140 . 
     The outer shape of the pushing member  130  is configured by a pair of second curved edges  132  on the front and rear sides and a pair of second linear edges  133  on the left and right sides in a planar view from above. The second curved edge  132  is a portion that extends curvedly along a circumferential portion having a predetermined radius. The second linear edge  133  is a portion that extends linearly along the X-axis direction. A pair of the second linear edges  133  are parallel to a pair of the first linear edges  123  of the metal contact  120 . The pushing member  130  is shaped into an outer shape having a pair of second curved edges  132  and a pair of second linear edges  133  by being side-cut linearly along the X-axis with respect to a member having a circular shape in a planar view from above. That is, the pushing member  130  has a longitudinal shape in which the X-axis direction is the longitudinal direction and the Y-axis direction is the shorter direction. 
     The cover sheet  140  is a thin sheet-like member mounted on the top surface of the case  110 . The cover sheet  140  is formed of a resin material such as PET and the like. The cover sheet  140  is a generally rectangular shape with a longitudinal direction in the X-axis direction and a shorter direction in the Y-axis direction in a planar view from above. That is, the cover sheet  140  is a shape substantially the same as the case  110  in a planar view from above. The cover sheet  140  is bonded to the upper surface of the case  110  by any bonding methods (for example, laser welding and the like) while covering the upper surface of the case  110 . The cover sheet  140  seals the housing space  110 A by closing the upper opening of the housing space  110 A of the case  110 . At the center of the cover sheet  140  is an upwardly projecting dome-like operating member  141 . The operating member  141  is the part where the operating portion performs a downward pressing operation. 
     A center  120 P (top  121 ) of the metal contact  120 , a center  130 P (top  131 ) of the pushing member  130 , and a center  140 P (top  141 A) of the cover sheet  140  overlap each other on an axis AX. 
     (Configuration of Bottom Surface of Pushing Member  130 ) 
       FIG. 3  is a perspective view of the bottom surface of the pushing member  130  of an embodiment. As illustrated in  FIG. 3 , a bottom surface  130 B of the pushing member  130  is planar. 
     As illustrated in  FIG. 3 , the pushing member  130  of the present embodiment is provided with each of the four pressing portions  134  with respect to each of the four corners of the bottom surface  130 B. In particular, the four pressing portions  134  are symmetrically disposed with respect to the center  130 P of the pushing member  130  (that is, the center  120 P of the metal contact  120 ). 
     Each pressing portion  134  protrudes downwardly from the bottom surface  130 B. Each pressing portion  134  has a predetermined height from the bottom surface  130 B. The bottom surface of each pressing portion  134  is planar. 
     A straight line SL 1  illustrated in  FIG. 3  is a line extending in the Y-axis direction through the center  130 P of the pushing member  130  and orthogonal to each of the pair of the second linear edges  133 . A straight line SL 2  illustrated in  FIG. 3  is a line extending in the X-axis direction through the center  130 P of the pushing member  130  and is a straight line parallel to each of the pair of the second linear edges  133 . 
     As illustrated in  FIG. 3 , at the bottom surface  130 B, each of the four pressing members  134  is provided in each of the four corners so that each of the four pressing members  134  does not overlap the straight line SL 1 . 
     Each pressing portion  134  has an inner circumferential surface  134 A, an outer circumferential surface  134 B, a side  134 C, and a side  134 D. The inner circumferential surface  134 A is a side extending along the circumference of a circle having a radius L 1  centered on a center  130 P of the pushing member  130 . The outer circumferential surface  134 B is a side extending along the curved edge  132 . The side  134 C is a side extending along a line at a predetermined angle with respect to the straight line SL 2 , and the line passes through the center  130 P of the pushing member  130 . The side  134 D is a side extending along the second linear edge  133 . 
     [Pressing Position of Metal Contact  120  by Pushing Member  130 ] 
       FIG. 4  is a planar view illustrating the pressing position of the metal contact  120  by the pushing member  130  of an embodiment.  FIG. 4  illustrates a stacked pushing member  130  and the metal contact  120 . 
     As illustrated in  FIG. 4 , the pushing member  130  is provided on the top  121  of the metal contact  120  so that the pair of the second linear edges  133  of the pushing member  130  and the pair of the first linear edges  123  of the metal contact  120  are parallel to each other. 
     In addition, as illustrated in  FIG. 4 , the pushing member  130  can press a position farther away in the X-axis direction from the straight line SL 1  (a line passing through the center  130 P and the midpoint of the first linear edges  123 ), that is, a position not overlapping the straight line SL 1 , against the metal contact  120  by each of the four pressing portions  134  provided in each of the four corners. 
     Thus, the push switch  100  of the present embodiment can push the metal contact  120  by the pushing member  130  so that an increase in the stress amplitude of the first linear edge  123  in the metal contact  120  is suppressed even when the operational load of the metal contact  120  is increased. 
     [Operational Load of Metal Contact  120 ] 
     In the push switch  100  of the present embodiment, the operational load of the metal contact  120  varies according to the distance L 1  (radius L 1 ) from the center  130 P of the pushing member  130  to the inner circumferential surface  134 A of the pressing portion  134 , the length L 2  of the inner circumferential surface  134 A, and the angle θ of the straight line SL 3  with respect to the straight line SL 2  as illustrated in  FIG. 3 . The straight line SL 3  is a line connecting the center  130 P of the pushing member  130  and the center  134 P of the pressing portion  134 . Thus, the push switch  100  of the present embodiment can set the operational load of the metal contact  120  to a target value by properly adjusting the distance L 1 , the length L 2 , and the angle θ in the pushing member  130 . 
       FIG. 5  is a diagram illustrating the relationship of distance L 1 , operating loads, and stress amplitudes in the push switch  100  according to an embodiment. For example, the push switch  100  in the present embodiment can increase the operational load of the metal contact  120  by increasing the distance L 1  in the pushing member  130 , by “the principle of leverage”, as illustrated in  FIG. 5A . Even in this case, the push switch  100  of the present embodiment is less likely to increase the stress amplitude of the first linear edge  123  of the metal contact  120 , as illustrated in  FIG. 5B . 
       FIG. 6  is a diagram illustrating the relationship of the length L 2 , the operational load, and stress amplitude of the push switch  100  of an embodiment. For example, as illustrated in  FIG. 6A , the push switch  100  in the present embodiment can increase the operational load of the metal contact  120  because the length L 2  in the pushing member  130  is smaller and the deformation of the portion of the metal contact  120  that is not coming in contact with the pushing member  130  becomes larger. Even in this case, the push switch  100  of the present embodiment is less likely to increase the stress amplitude of the first linear edge  123  of the metal contact  120 , as illustrated in  FIG. 6B . 
       FIG. 7  is a diagram illustrating the relationship of the angle θ, the operational load, and stress amplitude in the push switch  100  of an embodiment. For example, as illustrated in  FIG. 7A , the push switch  100  in the present embodiment increases the angle θ in the pushing member  130 , thereby increasing the amount of sinking near the first linear edge  123  in the metal contact  120 . Therefore, the operational load of the metal contact  120  can be increased. Even in this case, the push switch  100  of the present embodiment is less likely to increase the stress amplitude of the first linear edge  123  of the metal contact  120 , as illustrated in  FIG. 7B . 
     [First Modification of Pushing Member  130 ] 
       FIG. 8  is a diagram illustrating a first variation of the pushing member  130  of an embodiment. A pair of pressing portions  135  are symmetrically disposed with respect to the center  130 P of the bottom surface  130 B in the pushing member  130 - 1  in the first modification illustrated in  FIG. 8 . Each pressing portion  135  is of longest dimension in the Y-axis direction (axial direction perpendicular to the pair of the second linear edges  133 ) and extends along the curved edge  132 . 
     Each pressing portion  135  protrudes downwardly from the bottom surface  130 B. In addition, each pressing portion  135  has a certain height from the bottom surface  130 B. The bottom surface of each pressing portion  135  is planar. 
     The outer side  135 A of each pressing portion  135  is curved along the curved edge  132 . The side  135 B which is an inner side of each pressing portion (the side facing to the center  130 P) is linearly formed in a Y-axis direction. That is, the inner side  135 B of one pressing portion  135  and the inner side  135 B of the other pressing portion  135  are parallel to each other. 
     As illustrated in  FIG. 8 , at the bottom surface  130 B, the pair of the pressing portions  135  is provided along the pair of the curved edges  132  so that each of the pair of the pressing portions  135  does not overlap the straight line SL 1 , each of the curved edges having a corresponding pressing portion of the pressing portions. 
     Accordingly, the pushing member  130 - 1  of the first modification example can press a position farther away in the X-axis direction from the straight line SL 1  (a line passing through the center  130 P and the midpoint of the first linear edges  123 ), that is, a position not overlapping the straight line SL 1 , against the metal contact  120  by each of the pair of pressing portions  135 . 
     Thus, the pushing member  130 - 1  of the first modification example can press the metal contact  120  to suppress an increase in the stress amplitude of the first linear edge  123  of the metal contact  120  even when the operational load of the metal contact  120  is increased. 
     [Second Modification of Pushing Member  130 ] 
       FIG. 9  is a view illustrating a second modification example of the pushing member  130  of an embodiment. The pushing member  130 - 2  of the second modification example illustrated in  FIG. 9  is provided with each of the four pressing portions  136  with respect to each of the four corners of the bottom surface  130 B. In particular, four pressing portions  136  are symmetrically disposed with respect to the center  130 P of the pushing member  130 - 2 . 
     Each pressing portion  136  protrudes downwardly from the bottom surface  130 B. Each pressing portion  136  also has a certain thickness from the bottom surface  130 B. The bottom surface of each pressing portion  136  is planar. 
     Each of the pressing portions  136  illustrated in  FIG. 9  differs in shape from each of the pressing portions  134  illustrated in  FIG. 3  in a planar view from above. Each pressing portion  136  has a straight side  136 A parallel to the straight line SL 1 , a straight side  136 B parallel to the straight line SL 2 , a side  136 C extending along the curved edge  132 , and a side  136 D extending along the second linear edge  133 . 
     Therefore, in the pushing member  130 - 2  of the second modification example, two opposing sides  136 A are parallel to each other in the two pressing portions  136  adjacent in the X-axis direction. In addition, in the pushing member  130 - 2  of the second modification example, two opposing sides  136 B are parallel to each other in the two pressing portions  136  adjacent in the Y-axis direction. 
     Accordingly, the pushing member  130 - 2  of the second modification example may be processed for linear recessed portions (for example, machining, press machining, and the like) along the straight lines SL 1  and SL 2  in a region other than the pressing portions  136  with respect to the bottom surface  130 B, thereby forming each of the pressing portions  136  relatively easily. 
     As illustrated in  FIG. 9 , at the bottom surface  130 B, each of the four pressing portions  136  is disposed in each of the four corners so that each of the four pressing portions  136  does not overlap the straight line SL 1 . 
     Accordingly, the pushing member  130 - 2  of the second modification example can press a position farther away in the X-axis direction from the straight line SL 1  (a line passing through the center  130 P and the midpoint of the first linear edges  123 ), that is, a position not overlapping the straight line SL 1 , against the metal contact  120  by each of the four pressing portions  136 . 
     Thus, the pushing member  130 - 2  of the second modification example can press the metal contact  120  to suppress an increase in the stress amplitude of the first linear edge  123  of the metal contact  120  even when the operational load of the metal contact  120  is increased. 
     Comparative Example with Conventional Push Switches 
       FIG. 10  is a diagram illustrating a Comparative Example of an operational load between the push switch  100  of the present embodiment and a conventional push switch.  FIG. 11  is a diagram illustrating a Comparative Example of a stress amplitude between the push switch  100  of the present embodiment and a conventional push switch. 
     In the graph of  FIG. 10 , the vertical axis indicates the operational load of the metal contact. In the graph of  FIG. 11 , the longitudinal axis indicates the stress amplitude of both sides of the metal contact. In the graphs of  FIGS. 10 and 11 , the horizontal axis represents the type of push switch. 
     Here, “A” is the conventional push switch using a pushing member  210  illustrated in  FIG. 12 . “B” is the conventional push switch using a pushing member  220  illustrated in  FIG. 13 . “C” is the push switch  100  of the present embodiment using the pushing member  130  illustrated in  FIG. 3 . “D” is the push switch  100  of the present embodiment using the pushing member  130 - 1  illustrated in  FIG. 8 . “E” is the push switch  100  of the present embodiment using the pushing member  130 - 2  illustrated in  FIG. 9 . 
     In the Comparative Example, the conventional push switch having the same configuration as the push switch  100  of the present embodiment, except for the pushing member, is used. 
     As illustrated in  FIG. 10 , the push switches  100  (“C”, “D”, “E”) of the present embodiment can increase the operational load of the metal contact  120  compared to the conventional push switches (“A”, “B”). Also, as illustrated in  FIG. 11 , the push switches  100  (“C”, “D”, “E”) of the present embodiment can equal or lower the stress amplitude of the first linear edge  123  at the metal contact  120  compared to the conventional push switches. 
     First Example of Pushing Member Used for Conventional Push Switch 
       FIG. 12  is a diagram illustrating a first example of a pushing member used for the conventional push switch. As illustrated in  FIG. 12 , the conventional pushing member  210  has a circular shape in planar view. A bottom surface  210 A of the pushing member  210  is circular and planar. That is, the pushing member  210  presses against the top of the metal contact throughout the circular bottom surface  210 A. 
     Second Example of Pushing Member Used for Conventional Push Switch 
       FIG. 13  is a diagram illustrating a second example of a pushing member used for the conventional push switch. As illustrated in  FIG. 13 , the conventional pushing member  220  has a circular shape in a planar view. A bottom surface  220 A of the pushing member  220  is circular and planar. A circular pressing portion  221  is formed on the bottom surface  220 A along the outer peripheral edge of the bottom surface  220 A. The pressing portion  221  protrudes downwardly from the bottom surface  220 A and is a portion having a certain thickness from the bottom surface  220 A. That is, the pushing member  220  presses against the top of the metal contact throughout the annular pressing portion  221  on the bottom surface  220 A. 
     As described above, the push switch  100  according to an embodiment comprises the case  110  including the housing space  110 A having the upper opening and the first fixed contacts  111  provided on the bottom of the housing space  110 A; the metal contact  120  disposed in the housing space  110 A and coming in contact with the first fixed contacts  111  through deformation by receiving pressure applied from above; and the pushing member  130  disposed on the top of the metal contact  120  and transmitting the pressure to the metal contact  120 , wherein the metal contact  120  includes the pair of first linear edges  123  extending linearly, wherein the pushing member  130  includes a plurality of projecting pressing portions  134  disposed on a bottom surface  130 B facing the metal contact  120 , and wherein the plurality of pressing portions  134  is disposed on the bottom surface  130 B at positions not overlapping a straight line SL 1  that passes through the center of the metal contact  120  and intersecting each of the pair of first linear edges  123 . 
     Thus, the push switch  100  of the present embodiment can press the metal contact  120  by the pushing member  130  so that an increase in the stress amplitude of the first linear edge  123  of the metal contact  120  is suppressed even when the operational load of the metal contact  120  is increased. Therefore, the push switch  100  of the present embodiment can suppress the generation of cracks or the like in the metal contact  120 , and hence can achieve a longer life of the metal contact  120 . 
     While one embodiment of the invention has been described in detail above, the invention is not limited to these embodiments, and various modifications or variations are possible within the scope of the invention as defined in the appended claims. 
     For example, in the push switch of the present invention, the pushing member may have at least a plurality of pressing portions and may not be side-cut (for example, not having a pair of second linear edges, but circular in a planar view). 
     Furthermore, the pair of first linear edges  123  of the metal contact  120  is not limited to a straight line in a mathematical sense, and may be rounded to the extent of still appearing to be linear.