Abstract:
A switch unit includes an upper case that has an operation portion attached therein; a circuit board that has a switch attached thereto that is able to switch contact points by operation of the operation portion; and a lower case that fits into the upper case such that the lower case is surrounded by the upper case, and that accommodates the circuit board between the upper case and the lower case. A draining portion is provided at a side surface of the upper case, and the draining portion is integrally formed with a sidewall forming the side surface and protrudes downward, and has a width that gradually narrows from the top to the bottom thereof.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a switch unit into which water hardly permeates. 
         [0002]    Priority is claimed on Japanese Patent Application No. 2010-068131, filed Mar. 24, 2010, the content of which is incorporated herein by reference. 
       BACKGROUND ART 
       [0003]    A switch unit in which a printed-circuit board and the like are accommodated employs a structure into which water hardly permeates since it is necessary to prevent water from permeating into the switch unit. 
         [0004]    For example, a switch unit disclosed in Patent Document 1 has a structure that includes a lower case and an upper case fitted to the lower case from above. A printed-circuit board and the like are accommodated in the lower case, and operation portions of switches are provided at an upper portion of the upper case. Protruding portions formed on the side surfaces of the lower case are engaged with engaging holes formed at the side surfaces of the upper case, so that the upper case and the lower case are integrated with each other. Here, in order to prevent water from permeating from the engaging holes of the upper case, ribs are formed on the side surfaces of the upper case so as to surround upper portions and side portions of the engaging holes and guide water droplets and the like, which trickle down the side surfaces of the upper case from above, so that the water droplets flow down along the outsides of the ribs and the like. 
       CITATION LIST 
     Patent Document 
       [0005]    Patent Document 1: Japanese Unexamined Patent Application, First Publication No. 9-265851 
       SUMMARY OF INVENTION 
     Technical Problem 
       [0006]    However, in the switch unit having the above-mentioned structure, water flows over the ribs and flows to the inside of the ribs when a large amount of water falls on the upper case. Accordingly, there is a concern that water permeates from the locking holes. If the height of the rib is increased to prevent this, a fitting portion between the lower and upper cases becomes bulky. For this reason, there is a problem in that the size of the switch unit is increased. 
         [0007]    Accordingly, the invention provides a switch unit into which water hardly permeates. 
       Solution to Problem 
       [0008]    In a switch unit according to the invention, the following means is employed to solve the above-mentioned problem. 
         [0009]    A switch unit includes an upper case on which operation portions are mounted, a circuit board on which switches of which contact points are switched through the operation of the operation portions are mounted, and a lower case that is fitted to the upper case so that side surfaces of the lower case are surrounded by the upper case. The circuit board is accommodated between the upper case and the lower case. Draining portions, which are formed integrally with side walls forming side surfaces of the upper case so as to protrude downward and of which the width is gradually reduced toward the lower side from the upper side, are formed at the side surfaces of the upper case. 
         [0010]    According to the invention, water having trickled down the side surfaces of the upper case is guided to the draining portions and flows down so that the width is gradually reduced in accordance with the shape of the draining portion. Accordingly, it is possible to control a drain position. Further, even when a large amount of water falls, it is possible to guide the large amount of water by making the large amount of water trickle down. 
         [0011]    The switch unit may further include a connector that is provided on a bottom portion of the lower case and includes terminals electrically connected to the switches. The connector may include an opening portion that allows a plug electrically connected to the connector to be electrically connected to the terminals in a direction parallel to a longitudinal direction of the lower case as an insertion/separation direction. The draining portions may be disposed behind a position which overlaps the opening portion of the connector in the longitudinal direction of the lower case, in an insertion direction of the plug. 
         [0012]    In this case, it is possible to reduce the probability that water permeates into the connector from the opening portion of the connector. 
         [0013]    The draining portion may include two inclined sides that are inclined with respect to a horizontal direction at substantially the same angle and are disposed on the near side in the insertion direction of the plug and on the far side in the insertion direction of the plug, and the inclined side, which is disposed on the near side in the insertion direction of the plug, may be longer than the inclined side that is disposed on the far side in the insertion direction of the plug. 
         [0014]    In this case, the long inclined side of the flow passage for water, which is disposed on the near side, can guide water over a long distance as compared to the short inclined side of the flow passage for water that is disposed on the far side. Accordingly, even when the switch unit is in an inclined attitude where the rear portion of the switch unit in the longitudinal direction is lowered, it is possible to reduce the probability that water adheres near the opening portion of the connector. 
         [0015]    Engaging claws, which are engaged with the lower case, may be formed on the insides of the side surfaces of the upper case; engagement accommodating portions, which are engaged with the engaging claws of the upper case, may be formed at a bottom of the lower case; and the bottom of the lower case may be fitted into the upper case and the engaging claws are locked to the engagement accommodating portions. 
         [0016]    In this case, since it is not necessary to form holes and the like that are used to lock the lower case to the upper case, it is possible to further reduce the probability that water permeates into the upper and lower cases. 
       Advantageous Effects of Invention 
       [0017]    According to the invention, water having trickled down the side surfaces of the upper case is guided to the draining portions and flows down so that the width is gradually reduced in accordance with the shape of the draining portion. Accordingly, it becomes possible to control a drain position. Further, even when a large amount of water falls, it is possible to guide the large amount of water by making the large amount of water trickle down. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0018]      FIG. 1  is a front view of a switch unit according to an embodiment of the invention. 
           [0019]      FIG. 2  is a cross-sectional view taken along line A-A of  FIG. 1 . 
           [0020]      FIG. 3  is a perspective view showing the appearance of the switch unit according to the embodiment on which a plug is mounted, when viewed obliquely from below. 
           [0021]      FIG. 4  is an exploded perspective view of the switch unit according to the embodiment. 
           [0022]      FIG. 5  is a cross-sectional view of main portions of the switch unit according to the embodiment. 
           [0023]      FIG. 6  is an enlarged view of a draining portion of the switch unit according to the embodiment. 
           [0024]      FIG. 7  is a view illustrating a drain state when the switch unit according to the embodiment is in a horizontal attitude. 
           [0025]      FIG. 8  is a view illustrating a drain state when the switch unit according to the embodiment is in an inclined attitude where the rear portion of the switch unit is lowered. 
           [0026]      FIG. 9  is a view illustrating a drain state when the switch unit according to the embodiment is in an inclined attitude where the front portion of the switch unit is lowered. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0027]    A switch unit according to an embodiment of the invention will be described below with reference to  FIGS. 1 to 9 . 
         [0028]    The switch unit according to this embodiment is a power window switch that is used to automatically open and close glass windows of a left hand drive car. This switch unit is provided on an armrest of a door of an automobile that corresponds to a driver&#39;s seat. Meanwhile, an arrow X indicates the front side of a vehicle in the respective drawings. 
         [0029]    As shown in  FIGS. 1 to 4 , a switch unit  1  includes an upper case  10  on which six knobs (operation portions)  2 ,  3 ,  4 ,  5 ,  6 , and  7  are mounted, a lower case  30  that is locked to the upper case  10  by being fitted into the upper case  10  from below, a circuit board  50  that is accommodated between the upper and lower cases  10  and  30 , and a connector  70  that is mounted on the lower case  30 , as main components. 
         [0030]    The knob  2  is an operation portion of a push lock switch (not shown) that locks a glass window, and is mounted in a tubular portion  11 , which is formed on an upper portion of the upper case  10 , so as to be capable of moving up and down. The knob  2  is linked to the push lock switch fixed to the upper surface of a circuit board  50 , and can switch a contact point of the push lock switch. 
         [0031]    The knob  3  is an operation portion of a seesaw switch (not shown) that locks a door, and is mounted in a tubular portion  12 , which is formed on an upper portion of the upper case  10 , so as to be capable of rocking in a front-rear direction. The knob  3  is linked to the seesaw switch fixed to the upper surface of the circuit board  50 , and can toggle a contact point of the seesaw switch. 
         [0032]    The knob  4  is an operation portion of a seesaw switch (not shown) for a driver&#39;s seat that is used to open and close a glass window of a driver&#39;s seat, and is mounted in a tubular portion  13 , which is formed on the upper portion of the upper case  10 , so as to be capable of rocking in the front-rear direction. The knob  4  is linked to the seesaw switch for a driver&#39;s seat that is fixed to the upper surface of the circuit board  50 , and can toggle a contact point of the seesaw switch. 
         [0033]    The knob  5  is an operation portion of a seesaw switch (not shown) for a passenger seat that is used to open and close a glass window of a passenger seat, and is mounted in a tubular portion  14 , which is formed on the upper portion of the upper case  10 , so as to be capable of rocking in the front-rear direction. The knob  5  is linked to the seesaw switch for a passenger seat that is fixed to the upper surface of the circuit board  50 , and can toggle a contact point of the seesaw switch. 
         [0034]    The knob  6  is an operation portion of a seesaw switch (not shown) for a rear seat close to the driver&#39;s seat that is used to open and close a glass window corresponding to the rear seat close to the driver&#39;s seat, and is mounted in a tubular portion  15 , which is formed on the upper portion of the upper case  10 , so as to be capable of rocking in the front-rear direction. The knob  6  is linked to the seesaw switch for the rear seat close to the driver&#39;s seat that is fixed to the upper surface of the circuit board  50 , and can toggle a contact point of the seesaw switch. 
         [0035]    The knob  7  is an operation portion of a seesaw switch (not shown) for a rear seat close to the passenger seat that is used to open and close a glass window corresponding to the rear seat close to the passenger seat, and is mounted in a tubular portion  16 , which is formed on the upper portion of the upper case  10 , so as to be capable of rocking in the front-rear direction. The knob  7  is linked to the seesaw switch for the rear seat close to the passenger seat that is fixed to the upper surface of the circuit board  50 , and can toggle a contact point of the seesaw switch. 
         [0036]    The upper case  10  has the shape of a box, of which the lower portion is opened, having a substantially rectangular parallelepiped shape. The above-mentioned tubular portions  11  to  16  protrude upward from an upper surface  17  of the upper case  10 . 
         [0037]    The lower case  30  includes a shallow bottom portion  31  that is formed at a rear portion thereof and has a small depth. A connector terminal accommodating portion  32 , which is connected to the shallow bottom portion  31 , is formed at a portion of the lower case  30 , which is closer to the front portion of the lower case than the middle portion of the lower case in the front-rear direction, so as to protrude downward. A box-shaped stepped portion  33 , which rises in the form of a step up to the same level as the shallow bottom portion  31 , is formed in front of the connector terminal accommodating portion  32 . 
         [0038]    Flooding preventive cover portions  34  are provided at a substantially middle portion of the lower case  30  in the front-rear direction (in other words, in the rear of the connector terminal accommodating portion  32 ) on both left and right sides of the connector terminal accommodating portion  32  in a width direction. Front end portions of the flooding preventive cover portions  34  are disposed so as to overlap a rear end portion of the connector terminal accommodating portion  32 . 
         [0039]    The flooding preventive cover portions  34  are formed in the shape of a flat plate. Lower edges of the flooding preventive cover portions  34  are positioned slightly above a lower edge of the connector terminal accommodating portion  32 . Rear end faces  35  of the flooding preventive cover portions  34  are formed of inclined surfaces that are inclined downward toward the front side. 
         [0040]    The shallow bottom portion  31 , the connector terminal accommodating portion  32 , the box-shaped stepped portion  33 , and the flooding preventive cover portions  34  are connected integrally with each other at the upper portion of the lower case  30 . An upper side wall portion  36 , which makes the circuit of the upper portion of the lower case, is formed at the upper portion of the lower case  30 . 
         [0041]    A pair of left and right engagement accommodating portions  37  are formed at left and right portions of a portion of the upper side wall portion  36  corresponding to the shallow bottom portion  31 , and a positioning rib  40  is formed at the middle portion of the front end of the upper side wall portion  36 . When the lower case  30  is viewed from below, the engagement accommodating portions  37  are formed at the bottom  39  of the lower case  30  as shown in  FIG. 3 . 
         [0042]    Boss portions  38  into which fixing screws are inserted protrude upward from the upper surface of the rear end portion of the shallow bottom portion  31  and the upper surface of the front end portion of the box-shaped stepped portion  33 . 
         [0043]    Holes  51  into which the boss portions  38  are inserted are formed in the circuit board  50 . The circuit board  50  is formed so that the corresponding boss portions  38  are inserted into the holes  51 . The circuit board  50  is placed on the upper side wall portion  36  of the lower case  30 . 
         [0044]    As shown in  FIG. 3 , the lower case  30  mounted on the circuit board  50  is inserted into the upper case  10  from an opening  18  that is formed in the lower portion of the upper case  10 . At that time, the positioning rib  40  of the lower case  30  is inserted into a positioning recess  22  formed on the inner surface of a front wall portion  21  of the upper case  10 , so that the lower case  30  is positioned relative to the upper case  10  in the width direction. 
         [0045]    As shown in  FIGS. 3 and 5 , engaging claws  20 , which are formed on the inner surfaces of left and right side walls  19  of the upper case  10  extending in the front-rear direction of a vehicle body, are locked to the engagement accommodating portions  37  of the lower case  30 . Accordingly, the lower case  30  is temporarily fixed to the upper case  10 . The engaging claw  20  is formed in a tapered shape where the length of the engaging claw protruding from the inner surface of the side wall  19  is increased toward the upper side. For this reason, it is possible to easily engage the engaging claws  20  with the engagement accommodating portions  37  by moving the lower case  30  up relative to the upper case  10 . 
         [0046]    After the lower case  30  is temporarily fixed to the upper case  10  by the engaging claws  20  and the engagement accommodating portion  37 , screws (not shown) inserted into the boss portions  38  are screwed to screw holes (not shown) formed in the upper case  10 . Accordingly, the lower case  30  is reliably fixed to the upper case  10 , and the circuit board  50  is accommodated and fixed between the lower case  30  and the upper case  10 . When the lower case  30  is fixed to the upper case  10  as described above, all side surfaces of the upper side wall portion  36  of the lower case  30  are surrounded by the upper case  10 . 
         [0047]    The connector  70  includes a housing portion  71  and a plurality of terminals  72  that are formed substantially in an L shape and protrude forward from the front end of the housing portion  71 . The connector  70  is inserted into the lower case  30  from below and fixed to the lower case  30 . When the connector  70  is fixed, the terminals  72  are accommodated in the connector terminal accommodating portion  32  and connected to the circuit board  50 . The respective terminals  72  and the terminals of the above-mentioned respective switches fixed to the circuit board  50  are connected to each other through the circuit board  50 . That is, the lower case  30  includes the connector  70  at the bottom portion thereof. 
         [0048]    The housing portion  71  is disposed between the left and right flooding preventive cover portions  34 , and is covered with the flooding preventive cover portions  34  so that only the lower edge portions of the housing portion  71  are exposed to the outside. Further, the rear end of the housing portion  71  and the lower ends of the rear end faces  35  of the flooding preventive cover portions  34  are disposed at substantially the same position in the front-rear direction. 
         [0049]    Since the rear portion of the housing portion  71  is opened, a plug  100  can be inserted into the housing portion  71  from an opening portion  73  as shown in  FIG. 3 . An insertion/separation direction of the plug  100  is a direction that is parallel to the longitudinal direction of the lower case  30  (in other words, the front-rear direction of the vehicle body). The plug  100  is inserted into the connector  70  toward the front side, so that the plug  100  is electrically connected to the terminals  72  of the connector  70 . 
         [0050]    Draining portions  23 , which protrude downward, are formed at the left and right side surfaces of the upper case  10  at a substantially middle portion of the upper case  10  in the front-rear direction. The draining portions  23  are formed integrally with the side walls  19  in the shape of a flat plate. In this embodiment, the draining portions  23  are formed in a trapezoidal shape so that the width of the draining portion in the longitudinal direction of the upper case  10  (in other words, the width of the draining portion in the front-rear direction of the vehicle body) is reduced toward the bottom. The draining portions  23  are positioned outside the flooding preventive cover portions  34  of the lower case  30  as shown in  FIG. 3 , and are positioned in front of the opening portion  73  of the connector  70  as shown in  FIG. 1 . In other words, the draining portions  23  are disposed behind the position, which overlaps the opening portion  73  of the connector  70 , in the insertion direction of the plug  100 . 
         [0051]    An inclined side  24  formed at the front portion of the draining portion  23  is formed so that an inclination angle a between the inclined side  24  and a horizontal direction is in the range of, preferably, 45° to 70° and, more preferably, 55° to 65°. Meanwhile, an inclined side  25  formed at the rear portion of the draining portion is formed so that an inclination angle β between the inclined side  25  and the horizontal direction is in the range of, preferably, 45° to 70° and, more preferably, 55° to 65°. Further, the inclination angle α between the inclined side  24  and the horizontal direction and the inclination angle β between the inclined side  25  and the horizontal direction have been formed so as to be equal to each other in this embodiment, but the invention is not limited thereto. Furthermore, the length of the inclined side  25 , which is disposed close to the rear portion of the vehicle body, is larger than the length of the inclined side  24 , which is disposed close to the front portion of the vehicle body. In other words, the length of the inclined side  25 , which is disposed on the near side in the insertion direction of the plug  100 , is larger than the length of the inclined side  24  that is disposed on the far side in the insertion direction of the plug  100 . Moreover, it is preferable that the lower end of the inclined side  25  formed close to the rear portion of the vehicle body be positioned closer to the front portion of the vehicle body than the opening portion  73  of the connector  70 . 
         [0052]    Next, the operation of the switch unit  1  will be described with reference to  FIGS. 7 to 9 . Meanwhile, a dashed-dotted line shows the line of flow of water in  FIGS. 7 to 9 . 
         [0053]    For example, it is supposed that rain falls on the switch unit  1  when a door corresponding to the driver&#39;s seat is opened while it is raining 
         [0054]      FIG. 7  shows a case when a vehicle stops or travels in a horizontal place,  FIG. 8  shows a case when a vehicle stops or travels on an uphill road, and  FIG. 9  shows a case when a vehicle stops or travels on a downhill road. 
         [0055]    Even in any one of cases, rain falling on the switch unit  1  trickles down the side walls  19  of the upper case  10  and falls down. Further, when water droplets, which fall down from immediately above the draining portions  23 , reach both the inclined sides  24  and  25  of the draining portions  23 , the water droplets flow down along these inclined sides  24  and  25 . Finally, the water droplets are collected at lower sides  26  of the draining portions  21 , and are separated and fall down from the lower sides  26 . 
         [0056]    Water droplets, which do not trickle down portions of the side walls  19  of the upper case  10  immediately above the draining portions  23  but trickle down the peripheral portions of the draining portions  23 , are also drawn into the flow of water flowing to both the inclined sides  24  and  25  of the draining portions  23 , are guided to the draining portions  23 , and flow down along the inclined sides  24  and  25 . Finally, the water droplets are collected at lower sides  26  of the draining portions  21 , and are separated and fall down from the lower sides  26 . 
         [0057]    Since it is possible to guide water, which flows around the draining portions  23 , to the draining portions  23  and to collect the flow of water at the lower sides  26  of the draining portions  23  as described above, it is possible to specify drain positions at the lower sides  26  of the draining portions  23 . Since the positions of the lower sides  26  of the draining portions  23  are shifted to the front portion of the vehicle body from the position of the opening portion  73  of the connector  70 , the opening portion  73  of the connector  70  is not flooded with water falling down from the lower sides  26 . That is, when the draining portions  23  are formed, it is possible to actively guide water, which might fall down from the side walls  19  of the upper case  10  near the opening portion  73  of the connector  70  when the draining portions  23  are not formed, to the draining portions  23 . Accordingly, it is possible to prevent the opening portion  73  of the connector  70  from being flooded. As a result, it is possible to reduce the probability that water permeates into the connector  70  from the opening portion  73  of the connector  70 . 
         [0058]    Further, even when a large amount of water falls, it is possible to guide a large amount of water by making the large amount of water trickle down the inclined sides  24  and  25  of the draining portions  23 . 
         [0059]    The long inclined side  25  of the flow passage for water can guide water over a long distance as compared to the short inclined side  24  of the flow passage for water. Accordingly, the force of water flowing along the long inclined side  25  of the flow passage for water becomes stronger than the force of water flowing along the short inclined side  24  of the flow passage for water. That is, a force, which guides water, of the long inclined side  25  of the flow passage for water becomes stronger than that of the short inclined side  24  of the flow passage for water. For this reason, even when the switch unit  1  is in an inclined attitude where the rear portion of the switch unit in the longitudinal direction is lowered as shown in  FIG. 8 , it is possible to reduce the probability that water adheres near the opening portion  73  of the connector  70 . 
         [0060]    In addition, since holes or the like used to lock the lower case  30  are not formed on the side walls  19  of the upper case  10 , it is possible to significantly reduce the probability that water permeates into the upper and lower cases  10  and  30 . 
       Other Embodiments 
       [0061]    Meanwhile, the invention is not limited to the above-mentioned embodiment. 
         [0062]    For example, in the above-mentioned embodiment, the inclined sides  24  and  25  of the draining portions  23  have been formed in a linear shape. However, the inclined sides may be formed in a concave curved shape. Further, the shape of the draining portion  23  is not limited to a trapezoidal shape, and may be, for example, an inverted triangular shape. In this case, inclined sides may also be formed in a linear shape or a concave curved shape. 
         [0063]    Furthermore, the switch unit is not limited to a power window switch and may be applied as switch units for a variety of uses. 
       INDUSTRIAL APPLICABILITY 
       [0064]    According to the invention, water having trickled down the side surfaces of the upper case is guided to the draining portions and flows down so that the width is gradually reduced in accordance with the shape of the draining portion. Accordingly, it is possible to control a drain position. Further, even when a large amount of water falls, it is possible to guide the large amount of water by making the large amount of water trickle down. 
       REFERENCE SIGNS LIST 
       [0065]      1 : switch unit 
         [0066]      2  to  7 : knob (operation portion) 
         [0067]      10 : upper case  10   
         [0068]      19 : side wall 
         [0069]      20 : engaging claw 
         [0070]      23 : draining portion 
         [0071]      24 ,  25 : inclined side 
         [0072]      30 : lower case 
         [0073]      37 : engagement accommodating portion 
         [0074]      39 : bottom 
         [0075]      50 : circuit board 
         [0076]      70 : connector 
         [0077]      72 : terminal 
         [0078]      73 : opening portion 
         [0079]      100 : plug