Patent Publication Number: US-2016238431-A1

Title: Liquid surface sensor

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is based on Japanese Patent Application No. 2013-210334 filed on Oct. 7, 2013, the disclosure of which is incorporated herein by reference. 
     TECHNICAL FIELD 
     The present disclosure relates to a liquid surface sensor applied to a container storing a liquid. 
     BACKGROUND ART 
     Conventionally, Patent Literature 1 discloses a type of a liquid surface sensor having a configuration including a sensor main body fastened to a tank and a float provided to float on a liquid. In the configuration, since an insertion part arranged at the sensor main body is inserted into an insertion hole formed in the float, the float is assembled to the sensor main body and is movable in a vertical direction. 
     Further, the float supports a sensor magnet, and a reed switch is received in the insertion part arranged at the sensor main body. As the above configuration, when the sensor magnet approaches the reed switch according to a variation of a height of a liquid surface, the reed switch is switched from an off state to an on state. 
     According to the above configuration, the float is movable relative to the sensor main body in the vertical direction by a distance where the insertion part is movable in the insertion hole in the vertical direction. Therefore, when a height of the insertion part in the vertical direction becomes larger, a stroke amount that is the distance where the float is movable in the vertical direction becomes smaller. However, in the above configuration, in addition of the reed switch, a reed wiring that is a rod shape and transmits a signal from the reed switch is received in the insertion part. Therefore, the insertion part becomes large in size, and it is difficult to ensure a distance between the sensor magnet and the reed switch. 
     Then, the liquid surface sensor has to be used in an environment where a magnetic noise from external is applied to the liquid surface sensor. Further, it is possible that a direction of the magnetic noise applied from external matches a direction of a magnetic field generated by the sensor magnet. In this case, the magnetic field of the sensor magnet is increased by the magnetic noise. Thus, in the liquid surface sensor where the distance between the sensor magnet and the reed switch is insufficiently ensured, even though the sensor magnet is separated from the reed switch by a maximum distance, it is impossible that the reed switch is switched from the on state to the off state. 
     PRIOR ART LITERATURES 
     Patent Literature 
     Patent Literature 1: JP2010-107370A 
     SUMMARY OF INVENTION 
     The present disclosure is made in view of the above matters, and it is an object of the present disclosure to provide a liquid surface sensor which improves a resistance for a magnetic noise applied from external. 
     According to an aspect of the present disclosure, to achieve the above object, the liquid surface sensor includes a fastened body including a fastened main body that is fastened to a container storing a liquid and an axle part that is a tubular shape and protrudes from the fastened main body, a float floating on the liquid and including an insertion hole into which the axle is inserted and assembled to the fastened body and being movable relative to the fastened body in a vertical direction in a case where the axle part is inserted into the through hole, a magnet part supported by the float and generating a magnetic field, and a switch mechanism received in the axle part. The switch mechanism includes a switch that is switched from an off state to an on state when being approached by the magnet part, a receiving part that receives the switch, an output part that is exposed from the receiving part toward a first direction of the axle part and to which a signal indicating the on state of the switch or the off state of the switch is transmitted, and a conductive film that is a film covering an outer surface of the receiving part and extending from the output part in a second direction opposite to the first direction and to which the signal transmitted to the output part is transmitted. 
     According to the present disclosure, the signal of the switch transmitted to the output part exposed from the receiving part toward the first direction can be transmitted through the conductive film extending from the output part in the second direction. As the above configuration, a reed wiring transmitting the signal from the output part may be not received in the axle part. Since the conductive film is a film covering the outer surface of the receiving part, a miniaturization of the axle part receiving the switch mechanism can be obtained. 
     In the axle part that is miniaturized, a height of the axle part in the vertical direction is suppressed. Therefore, a distance where the axle part can move in the vertical direction in the through hole is a stroke amount where the float can move relative to the fastened body in the vertical direction, and is enlarged. As the above description, a distance between the magnet part and the switch mechanism can be ensured. Thus, even though the direction of the magnetic field generated by the magnet part matches the direction of the magnetic field of the magnetic noise, the switch mechanism can be switched from the on state to the off state since the magnet part is separated from the switch mechanism. Thus, the liquid surface sensor in which a resistance for the magnetic noise applied from external is improved can be provided. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The above and other objects, features and advantages of the present disclosure will become more apparent from the following detailed description made with reference to the accompanying drawings. In the drawings: 
         FIG. 1  is a diagram showing a liquid surface sensor installed to a washer tank, according to a first embodiment of the present disclosure; 
         FIG. 2  is a plan view showing a reed switch connected with a terminal from a top side; 
         FIG. 3  is a perspective view showing the reed switch connected with the terminal; 
         FIG. 4  is a cross-sectional view along an IV-IV line in  FIG. 1  and showing a shape of a cross-sectional surface of a reed switch axle; 
         FIG. 5  is a diagram showing a principle that a maximum distance between the reed switch and a magnet is enlarged according to a miniaturization of the reed switch axle; 
         FIG. 6  is a diagram showing the liquid surface sensor installed to the washer tank, according to a second embodiment of the present disclosure; 
         FIG. 7  is a plan view showing the reed switch connected with the terminal from the top side; 
         FIG. 8  is a perspective view showing the reed switch connected with the terminal; and 
         FIG. 9  is a cross-sectional view along an IX-IX line in  FIG. 6  and showing the shape of the cross-sectional surface of the reed switch axle. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereafter, referring to drawings, embodiments of the present disclosure will be described. The substantially same parts or components as those in the embodiments are indicated with the same reference numerals and the same descriptions may be omitted. When only a part of a configuration in each embodiment is detailed, the other parts of the configuration can be configured as the same as a prior embodiment. Further, it is to be understood that the disclosure is not limited to the embodiments and constructions. The present disclosure is intended to cover various modification and equivalent arrangements. In addition, while the various combinations and configurations, which are preferred, other combinations and configurations, including more, less or only a single element, are also within the spirit and scope of the present disclosure. 
     First Embodiment 
     As shown in  FIG. 1 , a liquid surface sensor  100  according to a first embodiment of the present disclosure is installed to a washer tank  90 . The washer tank  90  is mounted to an engine room of a vehicle, and stores a washer liquid as a liquid. The liquid surface sensor  100  detects a decrease of a liquid surface in accordance with a decrease in water liquid stored in the washer tank  90 . The liquid surface sensor  100  is inserted into the washer tank  90  through an opening  91  formed on the washer tank  90 . 
     First, a configuration of the liquid surface sensor  100  will be described. Further, hereafter, a direction in which the liquid surface sensor  100  is inserted into the opening  91  is referred to as an axial direction AD. Furthermore, a direction parallel to a direction of gravity is referred to as a vertical direction VD. Moreover, a direction substantially perpendicular to the axial direction AD and the vertical direction VD is referred to as a horizontal direction HD. In addition, the axial direction AD includes a first direction in which a reed switch axle  13  protrudes, and a second direction that is opposite to the first direction. 
     The liquid surface sensor  100  includes a case  10 , a connector member  20 , a float  30 , a magnet  50 , a reed switch  40 , and terminals  60  and  70 . 
     The case  10  is made of a resin material such as a polypropylene. The case  10  includes a fastened main body  11 , the reed switch axle  13 , and a limiting part  16 . The fastened main body  11  is fastened to the washer tank  90  through a grommet  92 . The fastened main body  11  is a ring shape and has a diameter larger than the opening  91  has. The fastened main body  11  and the grommet  92  cooperates to liquid-tightly seal the opening  91  from an exterior of the washer tank  90 . The reed switch axle  13  is a tubular shape such as a cylindrical shape and protrudes in the first direction from a center of the fastened main body  11  along the axial direction AD. The reed switch axle  13  forms a receiving chamber  14  receiving the reed switch  40 , according to a shape of the reed switch axle  13  protruding in the axial direction AD. The reed switch axle  13  includes a distal end in the first direction, and a flange part  15  is arranged at the distal end. The limiting part  16  is a wall part extending in the vertical direction VD. The limiting part  16  limits a rotation of the float  30  relative to the reed switch axle  13  by being in contact with the float  30 . 
     The connector member  20  is made of a resin material such as a polyethylene-terephthalate. The connector member  20  is fitted into the fastened main body  11 . The terminals  60  and  70  are fitted into the connector member  20 . The connector member  20  includes an engagement part  21 . When the engagement part  21  is engaged with a plug from external, the terminals  60  and  70  protruding in the engagement part  21  are electrically connected with a control circuit (not shown) from external. 
     The float  30  is made of a material having a specific gravity smaller than that of the washer liquid, and the float  30  can float on a liquid surface of the washer liquid. Specifically, the float  30  is made of a polypropylene resin added by a foaming agent. The float  30  is a columnar shape and extends in the axial direction AD. The float  30  includes a through hole  31  and a protrusion wall part  32 . The through hole  31  is a through hole into which the reed switch axle  13  is inserted. The through hole  31  penetrates the float  30  in the axial direction AD. The through hole  31  has an inner width in the horizontal direction HD which is smaller than an outer width of the flange part  15  in the horizontal direction HD. When the reed switch axle  13  is inserted through the through hole  31 , the float  30  is prevented from separating from the reed switch axle  13  according to the flange part  15 . As the above configuration, the float  30  is assembled to the case  10 , and is movable relative to the case  10  in the vertical direction VD. The protrusion wall part  32  is arranged at an end of the float  30  in the axial direction AD which is close to the fastened main body  11 . The protrusion wall part  32  extends in the vertical direction VD. When the float  30  starts to rotate relative to the reed switch axle  13 , the protrusion wall part  32  is in contact with the limiting part  16  to maintain a position of the float  30 . 
     The magnet  50  is a permanent magnet such as a ferrite magnet, and generates a magnetic field. The magnet  50  is a rectangle in a cross section, and is a prismatic shape extending in the axial direction AD. The magnet  50  is supported by the float  30 , and is placed at a position above the reed switch axle  13 . The magnet  50  and the float  30  can move up and down by following the liquid surface. 
     The reed switch  40  is a switch mechanism detecting a height of the liquid surface. In this case, the height of the liquid surface is also a level of the liquid surface. The reed switch  40  includes a switch main body  43  which is a tubular shape such as a cylindrical shape and extends in the axial direction AD, and a pair of reeds  41  and  42  which penetrates the switch main body  43 . The reed switch  40  is placed at a position where an axial direction of the switch main body  43  is parallel to the axial direction AD of the reed switch axle  13 , and is received in the receiving chamber  14 . The switch main body  43  is a glass pipe which is hollow and receives the reeds  41  and  42  which are a rod shape extending in the axial direction AD. According to the present embodiment, end parts of the reeds  41  and  42  are switch end parts. Each of the switch end parts can be bent. The switch end parts are arranged to be opposite to each other by a predetermined interval, so as to constitute a switch  44 . Between the reeds  41  and  42 , the reed  42  extends from the switch main body  43  in the first direction of the reed switch axle  13 , and the reed  41  extends from the switch main body  43  in the second direction of the reed switch axle  13 . 
     When a magnet field is applied to the reeds  41  and  42  from external, the switch end parts attract each other by being magnetized into different magnetic poles. Then, since the switch end parts are in contact with each other, the reed switch  40  is turned on to be conductive between the reeds  41  and  42 . In this case, the reed switch  40  is in an on state. A signal indicating an on state or an off state of the switch  44  is transmitted to end parts of the reeds  41  and  42  exposed from the switch main body  43 . According to the present embodiment, the end parts of the reeds  41  and  42  exposed from the switch main body  43  are output end parts. 
     The terminals  60  and  70  transmit a signal indicating the on state or an off state of the reed switch  40 . The terminals  60  and  70  are a strip plate shape and extend in the axial direction AD. The terminals  60  and  70  have end parts protruding in the axial direction AD from the connector member  20 . The terminal  60  is placed at a position above the terminal  70 . In the fastened main body  11 , the terminal  60  is connected to the reed  41  extending toward the connector member  20  from the switch main body  43  by soldering. 
     In the liquid surface sensor  100 , when the liquid surface of the washer liquid is sufficiently high, the float  30  displaces upward in a direction perpendicular to the reed switch axle  13 . In this case, since the magnet  50  is separated from the reed switch  40 , the reed switch  40  is turned off. In this case, the reed switch  40  is in the off state. When the washer liquid stored in the washer tank  90  is decreased, the float  30  displaces downward in a direction perpendicular to the reed switch axle  13 . Then, since the magnet  50  approaches the reed switch  40 , the reed switch  40  is switched from the off state to the on state by the magnetic field generated by the magnet  50 . 
     In the engine room where the liquid surface sensor  100  is arranged, magnets which are assembled to a motor and a power generator exist. Magnetic forces generated by the magnets are applied to the liquid surface sensor  100  as a magnetic noise applied from external. When a direction of the magnetic field generated by the magnet  50  matches a direction of the magnetic field of the magnetic noise, the magnetic field generated by the magnet  50  is increased. Then, even though the magnet  50  is separated from the reed switch  40  by a maximum distance, it is possible that the reed switch  40  is still in the on state. A configuration of the liquid surface sensor  100  which avoids a generation of the above matters will be described. 
     As shown in  FIGS. 1 to 3 , a conductive film  46  is arranged on the reed switch  40 . The conductive film  46  is a thin film made by a conductive coating that is directly sprayed on an outer surface of the reed switch  40 . Specifically, the conductive coating may be a silver coating, a silver-plated copper coating, a silver-plated nickel coating, a copper coating, or a nickel coating. The conductive film  46  covers the output end part of the reed  42  and extends in the second direction through an outer surface of the switch main body  43 . The conductive film  46  is a strip shape, extends in the axial direction AD from the reed  42  to the terminal  70 , and is connected with the terminal  70  in the reed switch axle  13 . The conductive film  46  has a high conductivity and can transmit the signal of the switch  44  transmitted to the reed  42  to the terminal  70 . The conductive film  46  is placed at a position that is separated from the reed  41  so as to prevent an occurrence of a short circuit between the conductive film  46  and the reed  41 . The conductive film  46  is placed at a position of the outer surface of the switch main body  43  other than an area that covers the switch  44  in the vertical direction VD. According to the first embodiment, specifically, the conductive film  46  is placed at a position of the switch main body  43  that covers the switch  44  in the horizontal direction HD. 
     The terminal  70  includes a bent part  71 . The bent part  71  is a part of the terminal  70  where the strip plate shape is bent into a semi-cylindrical shape. When a cross section of the terminal  70  is a section intersecting with the axial direction AD, a cross section of the bent part  71  that is parallel to the cross section of the terminal  70  is an arc shape and extends in a circumferential direction of the reed  41 . As the above configuration, a part of the bent part  71 , which is placed at a position in the receiving chamber  14 , is separated from the reed  41  to generate a gap and surrounds an area underneath the reed  41 . 
     As shown in  FIG. 4 , a radius of curvature is substantially constant in the cross section of the bent part  71 . Further, an outer diameter of the bent part  71  is set to be smaller than an outer diameter of the switch main body  43 . Therefore, the bent part  71  is received in an area of the switch main body  43  which is projected in the second direction along the axial direction AD. Thus, the bent part  71  can be received in the receiving chamber  14  by fitting the switch main body  43 . 
     As shown in  FIG. 1 , an end of the bent part  71  in the axial direction AD which is separated from the switch main body  43  is fitted into the connector member  20 . Therefore, a step generated between the bent part  71  and a part of the terminal  70  which is a flat plate shape is not exposed to an exterior of the connector member  20 . As the above configuration, when the terminal  70  is formed at the connector member  20  by an insert molding, it can be avoided that a situation where a mold release of a molding product is difficult or impossible due to the step of the terminal  70  in a step releasing the molding product from a molding die in the axial direction AD. 
     As shown in  FIG. 4 , the receiving chamber  14  formed in the reed switch axle  13  is an elliptical shape having a major axis that is in the horizontal direction HD. An inner dimension of the receiving chamber  14  in the vertical direction VD is slightly larger than the outer diameter of the switch main body  43 . An inner dimension of the receiving chamber  14  in the horizontal direction HD is larger than the inner dimension of the receiving chamber  14  in the vertical direction VD. Therefore, a gap  47  through which the conductive film  46  passes in the horizontal direction HD is generated between an inner wall surface of the receiving chamber  14  and the outer surface of the switch main body  43 . A shape of the reed switch axle  13  corresponds to a shape of the receiving chamber  14  in the cross section. Specifically, a height h of the reed switch axle  13  in the vertical direction VD is slightly larger than a width w of the reed switch axle  13  in the horizontal direction HD. 
     As the above configuration, a transmission member that is arranged to span the switch main body  43  in the axial direction AD and transmits the signal from the reed  42  may be not received in the receiving chamber  14 . In addition, since the conductive film  46  is a film covering the outer surface of the switch main body  43 , a miniaturization of the reed switch axle  13  forming the receiving chamber  14  can be obtained. 
     When the magnet  50  is separated from the reed switch  40  by the maximum distance, a maximum separating distance d_ 1  that is a distance between the magnet  50  and the reed switch  40  is enlarged according to the miniaturization of the reed switch axle  13 . Referring to  FIGS. 5(A) and 5(B) , a principle of the above phenomenon will be described.  FIG. 5(B)  is a diagram showing an operation of a float  130  in a case where a terminal  170  that is a rod shape and spans a switch main body, for a comparison. Further, the float  130  includes a through hole  131  having an inner dimension in the vertical direction VD that is equal to an inner dimension of the through hole  31  of the float  30 . 
     A stroke amount St_ 1  of the float  30  and a stroke amount St_ 2  of the float  130  are determined according to the inner dimensions of the through holes  31 ,  131  in the vertical direction VD and heights h (refer to  FIG. 4 ) of reed switch axles  13 ,  113  in the vertical direction VD, respectively. In this case, since the conductive film  46  is provided, the height h of the reed switch axle  13  is decreased by Δh from the height h of the reed switch axle  113  of an example where the terminal  70  is arranged in the receiving chamber  14 . Therefore, the stroke amount St_ 1  becomes larger than the stroke amount St_ 2  by a distance that is substantially equal to Δh that is a decreasing amount of the height h. Thus, the maximum separating distance d_ 1  between the reed switch  40  and the magnet  50  in an example where the conductive film  46  is used to decrease the height h is larger than the maximum separating distance d_ 2  between the reed switch  40  and the magnet  50  in an example where the terminal  170  is provided by Δh. 
     According to the first embodiment, the height h of the reed switch axle  13  is suppressed according to the miniaturization of the reed switch axle  13 . Therefore, a distance where the reed switch axle  13  can move in the vertical direction VD in the through hole  31  is the stroke amount St_ 1  where the float  30  can move relative to the case  10  in the vertical direction VD, and the stroke amount St_ 1  is enlarged. As the above description, the maximum separating distance d_ 1  between the magnet  50  and the reed switch  40  can be ensured. Therefore, even though the direction of the magnetic field generated by the magnet  50  matches the direction of the magnetic field of the magnetic noise, the reed switch  40  can be switched from the on state to the off state since the magnet  50  is separated from the reed switch  40 . Thus, the liquid surface sensor  100  in which a resistance for the magnetic noise applied from external is improved can be provided. 
     According to the first embodiment, since the terminal  70  is connected with the conductive film  46 , the terminal  70  functions to transmit signals. As the above configuration, a forming area of the conductive film  46  is limited to the outer surface of the switch main body  43  and an outer surface of the reed  42  protruding from the switch main body  43 . Then, since the forming area of the conductive film  46  is narrowed, it is difficult that the conductive film  46  is damaged. 
     According to the first embodiment, since an area of the cross section of the bent part  71  is smaller than an area of a cross section of the switch main body  43 , the bent part  71  can be received in a space in the receiving chamber  14  through which the switch main body  43  passes. As the above description, it can be avoided that the reed switch axle  13  is increased in size to receive the terminal  70 . 
     According to the first embodiment, in the receiving chamber  14  that is narrowed due to the conductive film  46 , a gap can be generated between the terminal  70  where the bent part  71  that is a semi-cylindrical shape is provided, and the reed  41 . Therefore, it can be avoided that the terminal  70  and the reed  41  are in contact with each other in the receiving chamber  14  so as to lead to a short circuit. As the above description, it is preferable that a configuration that the bent part  71  is provided in the terminal  70  is applied to an example where the switch main body  43  is miniaturized by the conductive film  46 . 
     According to the first embodiment, the gap  47  through which the conductive film  46  passes is ensured between the inner wall surface of the receiving chamber  14  and the outer surface of the switch main body  43 . Therefore, even though a vibration is transmitted to the liquid surface sensor  100  from external, it can be avoided that the conductive film  46  is damaged due to a friction between the conductive film  46  and the inner wall surface. 
     According to the first embodiment, the conductive film  46  is placed at a position of a side surface of the switch main body  43  other than an area that covers the switch  44  in the vertical direction VD. Therefore, it is impossible that an increasing in size of the reed switch axle  13  in the vertical direction VD is generated due to the gap  47 . Thus, a high reliability of the conductive film  46  can be ensured, and the resistance for the magnetic noise is improved. 
     According to the first embodiment, the case  10  is equivalent to a fastened body, the reed switch axle  13  is equivalent to an axle part, and the connector member  20  is equivalent to a support member. Further, the through hole  31  is equivalent to an insertion hole, the reed switch  40  is equivalent to a switch mechanism, the reed  41  is equivalent to a reed part, and the reed  42  is equivalent to an output part. Furthermore, the switch main body  43  is equivalent to a receiving part, the magnet  50  is equivalent to a magnet part, and the terminal  70  is equivalent to a connection member. Moreover, the washer tank  90  is equivalent to a container. 
     Second Embodiment 
     A second embodiment of the present disclosure shown in  FIGS. 6 to 9  is a modification example of the first embodiment. As shown in  FIGS. 6 to 8 , in the second embodiment, a conductive film  246  arranged on the reed switch  40  is a strip shape and extends in the axial direction AD from the reed  42  to a terminal  270 . The conductive film  246  is placed at a position of the outer surface of the switch main body  43  over the switch  44 . 
     The terminal  270  includes a cylindrical part  271  and a semi-cylindrical part  272 . As shown in  FIG. 9 , an outer diameter of the cylindrical part  271  and an outer diameter of the semi-cylindrical part  272  are smaller than the outer diameter of the switch main body  43 . Therefore, the cylindrical part  271  and the semi-cylindrical part  272  are received in a receiving chamber  214 . The cylindrical part  271  is in contact with the switch main body  43  and is electrically connected with the conductive film  246 . The cylindrical part  271  is separated from the reed  41  to generate a gap and surrounds an entire periphery of the reed  41 . The semi-cylindrical part  272  is interposed between the cylindrical part  271  and the connector member  20 . The semi-cylindrical part  272  is separated from the reed  41  to generate a gap and is a semi-cylindrical shape surrounding an area underneath the reed  41 . The semi-cylindrical part  272  is open at an area over the reed  41 . Thus, the semi-cylindrical part  272  can be connected with the terminal  60  placed at a position over the terminal  270 , and can be connected with the reed  41 . 
     According to the second embodiment, as shown in  FIGS. 6 and 9 , a reed switch axle  213  is a tubular shape such as a cylindrical shape. Since the conductive film  246  is provided, a transmission member transmitting the signal from the reed  42  is cancelled from the receiving chamber  214 . An inner diameter of the reed switch axle  213  is slightly larger than the outer diameter of the switch main body  43 . Thus, the miniaturization of the reed switch axle  213  that forms the receiving chamber  214  is achieved. 
     According to the second embodiment, a height h of the reed switch axle  213  is suppressed according to the miniaturization of the reed switch axle  213 , as the same as the height h of the reed switch axle  213  in the first embodiment. Therefore, as shown in  FIG. 6 , a stroke amount where the float  30  can move in the vertical direction VD is enlarged. Thus, the resistance for the magnetic noise applied from external is improved. 
     According to the second embodiment, the reed switch axle  213  is equivalent to the axle part, the terminal  270  is equivalent to the connection member, and the cylindrical part  271  and the semi-cylindrical part  272  are equivalent to the bent part. 
     Other Embodiment 
     The present disclosure is not limited to the embodiments mentioned above, and can be applied to various embodiments and combinations within the spirit and scope of the present disclosure. 
     According to the above embodiments, since the resistance for the magnetic noise in the liquid surface sensor is ensured, a type number of the liquid surface sensor can be decreased. Specifically, in a conventional liquid surface sensor, since a resistance for a magnetic noise is insufficient, it is necessary to control a direction of a magnetic force generated by a magnet to be opposite to a direction of a magnetic noise. According to the above configuration, since the magnetic force of the magnet and the magnetic noise cancel each other, it is difficult that an erroneous operation of a reed switch is generated due to the magnetic noise. However, in this case, it is necessary that an attachment direction of the magnet changes according to a type of a vehicle to which the liquid surface sensor is installed, and then a new type of the liquid surface sensor is generated. According to the above embodiments, in the liquid surface sensor, since the maximum separating distance between the reed switch and the magnet is enlarged, the resistance for the magnetic noise is ensured. Therefore, the same type of the liquid surface sensor can be used without respect to the type of the vehicle to which the liquid surface sensor is installed. Thus, since it is unnecessary to change a direction of the reed switch and a direction of the magnet according to the type of the vehicle, a cost of the liquid surface sensor is reduced by decreasing the type of the liquid surface sensor. 
     According to the above embodiments, a shape of the conductive film that is a strip shape and has a narrow width can be properly changed. For example, the conductive film may be a shape that a width of the conductive film is continuously enlarged toward a direction opposite to the first direction of the reed switch axle. Alternatively, plural conductive films may be arranged on the outer surface of the switch main body. 
     According to the above embodiments, the case is assembled to the opening of the washer tank as the fastened body. However, a configuration of the fastened body may be properly changed. For example, an assembly that is constituted by the case and a bracket may be equivalent to the fastened body. Further, when a shape of the cross section of the reed switch axle can suppress the height of the reed switch axle in the vertical direction VD, the shape may be different from the above mentioned shapes. Furthermore, a shape of the insertion hole may be properly changed to fit the shape of the reed switch axle. 
     According to the above embodiments, the terminals  70  and  270  are a shape that is bent to surround the reed  41 . However, when the terminals  70  and  270  are separated from the reed  41  to generate a gap, the terminals  70  and  270  may be a member that is a flat strip plate shape or a rod shape, and the member may extend along the reed  41  as the connection member. Alternatively, since the connection member is larger than the switch main body in the horizontal direction HD, the connection member may be a shape protruding from the area of the switch main body which is projected in the axial direction AD. Further, a shape of the reeds  41  and  42  which are equivalent to the output part and the reed part is not limited to a rod shape, and may be properly changed. 
     According to the above embodiments, the magnet that is a rectangle plate shape is used as the magnet part. However, a shape and a material of a member that is equivalent to the magnet part may be properly changed. Further, a position of the magnet part which is supported may be properly changed. Furthermore, plural magnets may be used to constitute the magnet part. Moreover, the magnet part may be placed at a position underneath the reed switch. A configuration that is equivalent to the switch mechanism is not limited to the reed switch, and may be properly changed. 
     As the above description, the present disclosure is described based on examples in which the liquid surface sensor detects the height of the liquid surface of the washer liquid stored in the washer tank of the vehicle. However, the present disclosure is not limited to be applied to a detection of the height of the liquid surface of the washer liquid. The present disclosure can be applied to a liquid surface sensor in a container which is installed to a vehicle. In this case, the container may stores a liquid other than the above mentioned liquid, such as an engine oil, a brake fluid, an engine coolant, and a fuel. Further, the present disclosure can be applied to a liquid surface sensor used in a container including various consumer appliances or various transportation machines, without being limited to the vehicle. 
     While the present disclosure has been described with reference to the embodiments thereof, it is to be understood that the disclosure is not limited to the embodiments and constructions. The present disclosure is intended to cover various modification and equivalent arrangements. In addition, while the various combinations and configurations, which are preferred, other combinations and configurations, including more, less or only a single element, are also within the spirit and scope of the present disclosure.