Patent Publication Number: US-2022236122-A1

Title: Pressure sensitive sensor

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of priority based on Japanese patent application No. 2021-011993 filed on Jan. 28, 2021 with the Japan Patent Office, and the entire disclosure of Japanese patent application No. 2021-011993 is incorporated herein by reference. 
     BACKGROUND 
     The present invention relates to a pressure sensitive sensor. 
     Known are pressure sensitive sensors performing a switch function when internal electric conductors are brought into a conducting state upon receiving an external force (for example, see JP H10-281906A (hereinafter, referred to as “Patent Document 1”)). The pressure sensitive sensors are used in opening/closing devices such as doors, windows, and shutters, and are used to detect passing vehicles, and are used as foot-pedal switches and the like. 
     SUMMARY 
     A pressure sensitive sensor described in Patent Document 1 has a hollow helical structure. Specifically, the pressure sensitive sensor has a hollow structure extending in a longitudinal direction in the central portion of the pressure sensitive sensor. In addition, four electric conductors are arranged at regular intervals in the circumferential direction around the hollow structure and spirally extend in the longitudinal direction. 
     In order to realize this hollow helical structure, the pressure sensitive sensor is manufactured through processes using a spacer to form the hollow structure. Specifically, the processes to manufacture the pressure sensitive sensor include a step of forming the pressure sensitive sensor by arranging the electric conductors around the spacer and a step of pulling out the spacer thereafter. 
     As a result, the pressure sensitive sensor of Patent Document 1 has a disadvantage that production costs are likely to increase. That is, there has been a problem that costs are likely to increase due to the tendencies that the number of processes to form the hollow structure increases, a material cost for the spacer increases, and a processing cost increases. 
     The pressure sensitive sensor is arranged along a shape of a portion of the above-mentioned opening/closing device where the sensor is arranged. For example, the pressure sensitive sensor may be arranged along shapes of convexly curved portions and concavely curved portions. There has been a problem that depending on the inner structure of the pressure sensitive sensor, it can be difficult to arrange the pressure sensitive sensor along the above-mentioned curved shapes (in other words, the pressure sensitive sensor can be inferior in allowable bending performance). 
     The present invention has been made to solve the above-mentioned problems and aims to inhibit the increase in production costs and to provide a pressure sensitive sensor that easily ensures the allowable bending performance. 
     In order to achieve the above mentioned purpose, the present invention provides means as indicated below. 
     A pressure sensitive sensor of the present invention includes a first conductive member formed into a long shape, the first conductive member having conductivity and elasticity; a second conductive member internally including a long space to arrange the first conductive member, the second conductive member having conductivity and elasticity; and an insulating member having an insulating property and elasticity, the insulating member holding the first conductive member to separate the first conductive member from the second conductive member, the insulating member being movable relative to at least one of the first conductive member and the second conductive member. 
     The pressure sensitive sensor of the present invention has a configuration in which the first conductive member and the second conductive member are coaxially arranged and between the first conductive member and the second conductive member, the insulating member is arranged and a space is formed. With this configuration, it is possible to manufacture the pressure sensitive sensor by a manufacturing method not using a spacer, such as extrusion molding, instead of the manufacturing method using the spacer as described in Patent Document 1. 
     The present invention has a configuration in which the insulating member is movable relative to at least one of the first conductive member and the second conductive member. Thus, the differences in expansion and contraction between the first conductive member and the second conductive member generated when the pressure sensitive sensor is bent can be easily absorbed by the above-described relative movement. 
     The pressure sensitive sensor of the present invention has effects of easily inhibiting the increase in manufacturing costs and easily ensuring the allowable bending performance. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a transverse sectional view showing a configuration of a pressure sensitive sensor according to a first embodiment of the present invention. 
         FIG. 2  is a transverse sectional view showing a state where a first conductive member and a second conductive member of the pressure sensitive sensor of  FIG. 1  are electrically connected. 
         FIG. 3  is a longitudinal sectional view showing a state where a pressure sensitive sensor of  FIG. 1  is bent. 
         FIG. 4A  is a transverse sectional view showing a configuration of a first variation of the pressure sensitive sensor of  FIG. 1 . 
         FIG. 4B  is a transverse sectional view showing a configuration of a second variation of the pressure sensitive sensor of  FIG. 1 . 
         FIG. 5A  is a transverse sectional view showing a configuration of a third variation of the pressure sensitive sensor of  FIG. 1 . 
         FIG. 5B  is a transverse sectional view showing a configuration of a fourth variation of the pressure sensitive sensor of  FIG. 1 . 
         FIG. 6A  is a transverse sectional view showing a configuration of a fifth variation of the pressure sensitive sensor of  FIG. 1 . 
         FIG. 6B  is a transverse sectional view showing a configuration of a sixth variation of the pressure sensitive sensor of  FIG. 1 . 
         FIG. 7A  is a transverse sectional view showing a configuration of a seventh variation of the pressure sensitive sensor of  FIG. 1 . 
         FIG. 7B  is a transverse sectional view showing a configuration of an eighth variation of the pressure sensitive sensor of  FIG. 1 . 
         FIG. 8  is a transverse sectional view showing a configuration of a ninth variation of the pressure sensitive sensor of  FIG. 1 . 
         FIG. 9  is a transverse sectional view showing a configuration of a pressure sensitive sensor according to a second embodiment of the present invention. 
         FIG. 10A  is a transverse sectional view showing a configuration of a first variation of the pressure sensitive sensor of  FIG. 9 . 
         FIG. 10B  is a transverse sectional view showing a configuration of a second variation of the pressure sensitive sensor of  FIG. 9 . 
         FIG. 11A  is a transverse sectional view showing a configuration of a third variation of the pressure sensitive sensor of  FIG. 9 . 
         FIG. 11B  is a transverse sectional view describing a configuration of the fourth variation of the pressure sensitive sensor of  FIG. 9 . 
         FIG. 12A  is a transverse sectional view showing a configuration of a fifth variation of the pressure sensitive sensor of  FIG. 9 . 
         FIG. 12B  is a transverse sectional view showing a configuration of a sixth variation of the pressure sensitive sensor of  FIG. 9 . 
         FIG. 13A  is a transverse sectional view showing a configuration of a seventh variation of the pressure sensitive sensor of  FIG. 9 . 
         FIG. 13B  is a transverse sectional view showing a configuration of an eighth variation of the pressure sensitive sensor of  FIG. 9 . 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     First Embodiment 
     Hereinafter, a pressure sensitive sensor  1  according to a first embodiment of the present invention will be described with reference to  FIG. 1  to  FIG. 8 . The pressure sensitive sensor  1  of the present embodiment has a circular columnar or cylindrical shape having a desired length.  FIG. 1  shows a sectional configuration of the pressure sensitive sensor  1  according to the first embodiment. 
     The pressure sensitive sensor  1  has a shape extending towards the front side and the back side of the plane of paper of  FIG. 1 . In this embodiment, an example will be described in which the pressure sensitive sensor  1  has a diameter of 4 mm. The diameter of the pressure sensitive sensor  1  may be smaller or larger than 4 mm. 
     The pressure sensitive sensor  1  includes, as shown in  FIG. 1 , a first conductive member  10 , a second conductive member  20 , a first insulating member (corresponding to an insulating member)  40  and a second insulating member  50  as main components. 
     The first conductive member  10  is a member arranged inside the second conductive member  20 . The first conductive member  10  is a member formed into a circular columnar shape and formed of a material having conductivity and elasticity. In this embodiment, an example will be described in which the first conductive member  10  has a circular shape in the transverse sectional view. Examples of the material to form the first conductive member  10  may include a conductive rubber containing carbon black. 
     The first conductive member  10  includes a first conductor  11 . The first conductor  11  is a wire rod formed of a metallic material having conductivity. The first conductor  11  is arranged along a center line in the circular columnar first conductive member  10 . In other words, the first conductor  11  is arranged coaxially with the first conductive member  10 . The first conductor  11  may be arranged in a place other than the center line in the first conductive member  10  as long as the first conductor  11  is arranged to be electrically conductive with the first conductive member  10 . 
     The second conductive member  20  is a cylindrical member having an internal space  30 , in which the first conductive member  10  and the first insulating member  40  are arranged. The second conductive member  20  is a member formed of a material having conductivity and elasticity. Examples of the material forming the second conductive member  20  may include conductive rubber such as polyolefin containing carbon black. 
     The second conductive member  20  includes a second conductor  21 . The second conductor  21  is a wire rod formed of a metallic material having conductivity. The second conductor  21  is arranged along the longitudinal direction in a peripheral wall of the cylindrical second conductive member  20 . 
     In this embodiment, a description will be made of an example in which the second conductor  21  is arranged at a position (or also referred to as “phase”) opposite the first insulating member  40  across the first conductive member  10 . The position where the second conductor  21  is arranged in the second conductive member  20  may be the above-mentioned position opposite the first insulating member  40 , or may be other position. 
     In this embodiment, a description will be made of an example in which the first conductor  11  and the second conductor  21  are tin-plated annealed copper stranded wires. Examples of the metallic material forming the first conductor  11  and the second conductor  21  may be a copper alloy containing copper as a component, silver, and a silver alloy containing silver as a component. 
     The first insulating member  40  is a circular columnar member arranged in the space  30  of the second conductive member  20  together with the first conductive member  10 . The first insulating member  40  has a diameter equal to an interval in a radial direction from the first conductive member  10  to the second conductive member  20 . 
     The first insulating member  40  is spirally arranged along a peripheral surface that is a surface of the first conductive member  10 . In this embodiment, a description will be made of an example in which the first insulating member  40  is a member holding the first conductive member  10  at a position coaxial with the second conductive member  20 . 
     The amount of movement (also referred to as “spiral pitch”) of the first insulating member  40  in the longitudinal direction produced while it goes around the first conductive member  10  one time can be appropriately set and is not particularly limited. Examples of a material forming the first insulating member  40  may include a rubber material, such as polyolefin, having an insulating property. 
     In this embodiment, a portion of the first insulating member  40  in contact with the first conductive member  10  is fusion-bonded with the first conductive member  10 . In other words, the first insulating member  40  is fixed to the first conductive member  10 . On the other hand, a portion of the first insulating member  40  in contact with the second conductive member  20  is not fusion-bonded with the second conductive member  20 . In other words, the first insulating member  40  is movable relative to the second conductive member  20 . If the first insulating member  40  and the first conductive member  10  use the same rubber material, they can be easily fixed by fusion-bonding. 
     In this embodiment, a description will be made of an example in which the first insulating member  40  and the first conductive member  10  are fusion-bonded, and the first insulating member  40  and the second conductive member  20  are not fusion-bonded; alternatively, a configuration may be adopted in which the first insulating member  40  and the first conductive member  10  are not fusion-bonded and the first insulating member  40  and the second conductive member  20  are fusion-bonded. Furthermore, a configuration may also be adopted in which the first insulating member  40  and the first conductive member  10  are not fusion-bonded and the first insulating member  40  and the second conductive member  20  are not fusion-bonded. 
     The second insulating member  50  is a cylindrical member that covers the outer peripheral surface of the second conductive member  20  and that forms an outer shape of the pressure sensitive sensor  1 . Examples of a material forming the second insulating member  50  may include a rubber material, such as polyurethane, having an insulating property. 
     In this embodiment, a portion of the second insulating member  50  in contact with the second conductive member  20  is not fusion-bonded with the second conductive member  20 . In other words, the second insulating member  50  is movable relative to the second conductive member  20 . The second insulating member  50  may be fusion-bonded with the second conductive member  20 . In other words, the second insulating member  50  may be fixed with the second conductive member  20 . 
     Next, a description will be made of an action of the pressure sensitive sensor  1  having the above-described configuration.  FIG. 2  shows a state where the first conductive member  10  and the second conductive member  20  of the pressure sensitive sensor  1  are electrically connected. 
     When pressing force P is not applied to the pressure sensitive sensor  1 , the first conductive member  10  and the second conductive member  20  are separated by the space  30  and the first insulating member  40  as shown in  FIG. 1 . That is, the first conductive member  10  and the second conductive member  20  are electrically separated as well. 
     When the pressing force P is applied to the pressure sensitive sensor  1 , the second insulating member  50  and the second conductive member  20  are elastically deformed as shown in  FIG. 2 . In this embodiment, a description will be made of an example in which the pressing force P directing from outside to the first conductive member  10  is applied. A part of the second conductive member  20 , to which the pressing force P is applied, is deformed towards the first conductive member  10 , and comes in contact with the first conductive member  10 . In other words, the first conductive member  10  and the second conductive member  20  become electrically conductive. 
     It is possible to detect whether the pressing force P is applied to the pressure sensitive sensor  1  based on the presence or absence of conductivity between the first conductive member  10  and the second conductive member  20 . It may be detected whether the pressing force P is applied to the pressure sensitive sensor  1  based on a resistance value between the first conductive member  10  and the second conductive member  20 . 
     Then, a description will be made of a case where the pressure sensitive sensor  1  having the above-described configuration is bent.  FIG. 3  shows a state when the pressure sensitive sensor  1  is bent. 
     When the pressure sensitive sensor  1  is bent, as shown in  FIG. 3 , force in a contracting direction is applied to an inner side portion (left portion in  FIG. 3 ) of the pressure sensitive sensor  1 , and force in an expanding direction is applied to an outer side portion (right portion in  FIG. 3 ) of the pressure sensitive sensor  1 . 
     The force in the contracting direction and the force in the expanding direction acting on the second conductive member  20  arranged on an outer peripheral side of the pressure sensitive sensor  1  are stronger than force in the contracting direction and force in the expanding direction acting on the first conductive member  10  arranged at the center of the pressure sensitive sensor  1 . 
     Since the second conductive member  20  is not fusion-bonded with the first insulating member  40 , the second conductive member  20  is in contact with the first insulating member  40  to be relatively movable. Thus, the inner side portion of the second conductive member  20  contracts while moving in a longitudinal direction relative to the first insulating member  40 . The outer side portion of the second conductive member  20  expands while moving in the longitudinal direction relative to the first insulating member  40 . 
     In contrast, when the second conductive member  20  is fusion-bonded and integrated with the first insulating member  40 , the inner side portion of the second conductive member  20  is constrained by the first insulating member  40  and the first conductive member  10  and is less likely to contract. The outer side portion of the second conductive member  20  is constrained by the first insulating member  40  and the first conductive member  10  and is less likely to expand. 
     The force in the contracting direction and the force in the expanding direction acting on the second insulating member  50  arranged on the outer peripheral side of the second conductive member  20  are stronger than force in the contracting direction and force in the expanding direction acting on the second conductive member  20  arranged on a center side. 
     Since the second insulating member  50  is not fusion-bonded with the second conductive member  20 , the second insulating member  50  is in contact with the second conductive member  20  to be relatively movable. Thus, the inner side portion of the second insulating member  50  contracts while moving in the longitudinal direction relative to the second conductive member  20 . The outer side portion of the second insulating member  50  expands while moving in the longitudinal direction relative to the second conductive member  20 . 
     In contrast, when the second insulating member  50  is fusion-bonded and integrated with the second conductive member  20 , the inner side portion of the second insulating member  50  is constrained by the second conductive member  20  and is less likely to contract. The outer side portion of the second insulating member  50  is constrained by the second conductive member  20  and is less likely to expand. 
     Next, a description will be made of an example of a method for manufacturing the pressure sensitive sensor  1  having the above-described configuration with reference to  FIG. 1 . 
     First, the first conductive member  10  is formed by a well-known manufacturing method, such as extrusion molding. The first conductive member  10  is formed into a circular columnar shape having the first conductor  11  arranged inside. 
     Then, the circular columnar first insulating member  40  is spirally arranged around the first conductive member  10 . The first insulating member  40  is formed by a well-known manufacturing method, such as extrusion molding. When the first insulating member  40  is arranged, management is performed to adjust temperature of the first conductive member  10  and the first insulating member  40  to temperature at which they are mutually fusion-bonded. The fusion-bonding temperature is temperature determined in accordance with types of materials forming the first conductive member  10  and the first insulating member  40 . The first conductive member  10  and the first insulating member  40  may be fixed using an adhesive agent. 
     Next, the cylindrical second conductive member  20  is arranged around the first insulating member  40 . At this time, the space  30  is formed between the first conductive member  10  and the second conductive member  20 . The second conductive member  20  is formed by a well-known manufacturing method, such as extrusion molding. When the second conductive member  20  is arranged, management is performed to adjust temperature of the first insulating member  40  and the second conductive member  20  to temperature at which they are not fusion-bonded. 
     Here, the temperature at which no fusion-bonding occurs is temperature less than temperature at which the first insulating member  40  and the second conductive member  20  are fusion-bonded. The temperature at which no fusion-bonding occurs is temperature determined in accordance with types of materials forming the first insulating member  40  and the second conductive member  20 . 
     Next, the cylindrical second insulating member  50  is arranged around the second conductive member  20 . The second insulating member  50  is formed by a well-known manufacturing method, such as extrusion molding. When the second insulating member  50  is arranged, management is performed to adjust temperature of the second conductive member  20  and the second insulating member  50  to temperature at which the second conductive member  20  and the second insulating member  50  are not mutually fusion-bonded. Through the above-described processes, the pressure sensitive sensor  1  is manufactured. 
     Here, the temperature at which no fusion-bonding occurs is temperature less than temperature at which the second conductive member  20  and the second insulating member  50  are fusion-bonded. The temperature at which no fusion-bonding occurs is temperature determined in accordance with types of materials forming the second conductive member  20  and the second insulating member  50 . 
     The above-described pressure sensitive sensor  1  has a configuration in which the first conductive member  10  and the second conductive member  20  are coaxially arranged, and between the first conductive member  10  and the second conductive member  20 , the first insulating member  40  is arranged and the space  30  is formed. With such a configuration, the pressure sensitive sensor  1  can be produced by a manufacturing method not using a spacer, such as extrusion molding, and an increase in manufacturing costs can be easily inhibited. 
     The pressure sensitive sensor  1  has a configuration in which the first insulating member  40  and the second conductive member  20  are movable relative to each other. Thus, the differences in expansion and contraction between the first conductive member  10  and the second conductive member  20  generated when the pressure sensitive sensor  1  is bent are easily absorbed by the relative movement of the first insulating member  40  and the second conductive member  20 . That is, it is easy to ensure an allowable bending performance of the pressure sensitive sensor  1 . 
     The allowable bending performance of the pressure sensitive sensor  1  is also easily ensured in a configuration in which the first insulating member  40  and the first conductive member  10  are movable relative to each other. In addition, the allowable bending performance of the pressure sensitive sensor  1  can be furthermore easily ensured by adopting a configuration in which the second insulating member  50  and the second conductive member  20  are movable relatively to each other. 
     The first insulating member  40  is spirally arranged around the first conductive member  10 , whereby the first conductive member  10  can be held to be separated from the second conductive member  20  by one first insulating member  40 . In comparison with a case where multiple first insulating members  40  are used, the second conductive member  20  easily deforms in response to the force from outside, and the second conductive member  20  and the first conductive member  10  easily come in contact with each other. Also, the number of the first insulating member  40  can be reduced, which contributes to reduction of manufacturing costs. 
     The pressure sensitive sensor  1  is not limited to the shape described in the above embodiment, and may have other shapes. For example, the pressure sensitive sensor  1  may have various shapes as described below. 
       FIG. 4A  is a transverse sectional view showing a configuration of a pressure sensitive sensor  1 A. In the pressure sensitive sensor  1 A, a shape of a first insulating member  40 A is different compared to the pressure sensitive sensor  1 . Other components than the first insulating member  40 A have the same shapes as those of the pressure sensitive sensor  1 . 
     The first insulating member  40 A is a member formed into a rectangular columnar shape. The first insulating member  40 A is spirally arranged along a circumferential surface of the first conductive member  10 . The first insulating member  40 A has a substantially rectangular shape extending in the radial direction from the first conductive member  10  towards the second conductive member  20  in the transverse sectional view. 
     The surface of the first insulating member  40 A in contact with the first conductive member  10  has a concavely curved shape along the peripheral surface of the first conductive member  10 , and is fusion-bonded with the first conductive member  10 . The surface of the first insulating member  40 A in contact with the second conductive member  20  has a convexly curved shape along the inner peripheral surface of the second conductive member  20 , and is not fusion-bonded with the second conductive member  20 . 
     Since the first insulating member  40 A is a member formed into the rectangular columnar shape, in comparison with the first insulating member  40  formed into a circular columnar shape, it is easy to increase areas in contact with the first conductive member  10  and the second conductive member  20 . Thus, the first insulating member  40 A can stably hold the first conductive member  10 . 
       FIG. 4B  is a transverse sectional view showing a configuration of a pressure sensitive sensor  1 B. In the pressure sensitive sensor  1 B, shapes of a second conductive member  20 B and a first insulating member  40 B are different compared to the pressure sensitive sensor  1 . Other components than the second conductive member  20 B and the first insulating member  40 B have the same shapes as those of the pressure sensitive sensor  1 . 
     The second conductive member  20 B is a cylindrical member having the internal space  30 , in which the first conductive member  10  and the first insulating member  40 B are arranged. The second conductive member  20 B includes a slit  22 B, in which an end of the first insulating member  40 B is arranged. The slit  22 B is a groove-shaped cutout formed in the second conductive member  20 B and spirally extends in the longitudinal direction along a circumferential surface of the second conductive member  20 B. 
     The first insulating member  40 B is a member formed into a rectangular columnar shape like the first insulating member  40 A. The end of the first insulating member  40 B on a second conductive member  20 B side passes through the inside of the slit  22 B and is in contact with an inner peripheral surface of the second insulating member  50 . 
     The first insulating member  40 B is not fusion-bonded with the second conductive member  20 B and the second insulating member  50 . In other words, the first insulating member  40 B is movable relative to the second conductive member  20 B and the second insulating member  50 . 
     Since the end of the first insulating member  40 B passes through the inside of the slit  22 B, it is easy to maintain an arrangement relationship between the first insulating member  40 B and the second conductive member  20 B in comparison with the pressure sensitive sensor  1  and the pressure sensitive sensor  1 A. 
       FIG. 5A  is a transverse sectional view showing a configuration of a pressure sensitive sensor  1 C. In the pressure sensitive sensor  1 C, a shape of a first insulating member  40 C is different compared to the pressure sensitive sensor  1 . Other components than the first insulating member  40 C have the same shapes as those of the pressure sensitive sensor  1 . 
     The first insulating member  40 C is a member spirally arranged along a circumferential surface of the first conductive member  10 . In the transverse sectional view, the first insulating member  40 C has a shape extending in the radial direction from the first conductive member  10  towards the second conductive member  20  and has a shape with recesses  41 C. 
     The surface of the first insulating member  40 C in contact with the first conductive member  10  has a concavely curved shape along the peripheral surface of the first conductive member  10 , and is fusion-bonded with the first conductive member  10 . The surface of the first insulating member  40 C in contact with the second conductive member  20  has a convexly curved shape along the inner peripheral surface of the second conductive member  20 , and is not fusion-bonded with the second conductive member  20 . 
     The recess  41 C is provided in each of a pair of surfaces of the first insulating member  40 C extending between the first conductive member  10  and the second conductive member  20 . In this embodiment, a description will be made of an example in which the recess  41 C is a groove having a substantially V-shape formed in the first insulating member  40 C. 
     In comparison with the case where the recesses  41 C are not provided, the first insulating member  40 C with the pair of recesses  41 C can have a part narrow in width and can easily buckle (or bend). Therefore, the first conductive member  10  and the second conductive member  20  easily come closer and come in contact with each other in comparison with the case where the recesses  41 C are not provided. 
     In this embodiment, a description has been made of an example in which the pair of recesses  41 C is provided in the first insulating member  40 C; alternatively, only one recess  41 C may be provided. The shape of the recess  41 C may be a V-shape or may be other shape, such as a U-shape, which allows the first insulating member  40 C to easily buckle. The position of this recess  41 C is preferably near the middle between the circumferential surface of the first conductive member  10  and the circumferential surface of the second conductive member  20 , which helps buckling. 
       FIG. 5B  is a transverse sectional view showing a configuration of a pressure sensitive sensor  1 D. In the pressure sensitive sensor  1 D, a shape of a first insulating member  40 D is different compared to the pressure sensitive sensor  1 . Other components than the first insulating member  40 D have the same shapes as those of the pressure sensitive sensor  1 . 
     The first insulating member  40 D is a member spirally arranged along the circumferential surface of the first conductive member  10 . The first insulating member  40 D has a curved rectangular shape extending in the radial direction from the first conductive member  10  towards the second conductive member  20  in the transverse sectional view. 
     The surface of the first insulating member  40 D in contact with the first conductive member  10  has a concavely curved shape along the peripheral surface of the first conductive member  10 , and is fusion-bonded with the first conductive member  10 . The surface of the first insulating member  40 D in contact with the second conductive member  20  has a convexly curved shape along the inner peripheral surface of the second conductive member  20 , and is not fusion-bonded with the second conductive member  20 . 
     In the first insulating member  40 D, one surface  41 D of a pair of surfaces extending between the first conductive member  10  and the second conductive member  20  has a convexly curved shape. The other surface  42 D of the pair of surfaces has a concavely curved shape. 
     In this embodiment, a description has been made of an example in which the first insulating member  40 D has a shape convexly curved in a counterclockwise direction in  FIG. 5B ; alternatively, the first insulating member  40 D may have a shape convexly curved in a clockwise direction. In the embodiment shown in  FIG. 5B , the first insulating member  40 D is spirally arranged in the counterclockwise direction along the circumferential surface of the first conductive member  10 . 
     The first insulating member  40 D has a curved rectangular shape. Thus, the first insulating member  40 D easily buckles (or bends) when the pressing force P is applied in comparison with a case where the first insulating member  40 D does not have the curved rectangular shape. Therefore, the first conductive member  10  and the second conductive member  20  easily come in contact with each other. 
       FIG. 6A  is a transverse sectional view showing a configuration of a pressure sensitive sensor  1 E. In the pressure sensitive sensor  1 E, a shape of a first insulating member  40 E is different compared to the pressure sensitive sensor  1 . Other components than the first insulating member  40 E have the same shapes as those of the pressure sensitive sensor  1 . 
     The first insulating member  40 E is a member formed into a cylindrical shape. The first insulating member  40 E is spirally arranged along the circumferential surface of the first conductive member  10 . In the transverse sectional view, the first insulating member  40 E has a shape having an outer peripheral surface  41 E and an inner peripheral surface  42 E. 
     The outer peripheral surface  41 E has a diameter equal to an interval in the radial direction from the first conductive member  10  to the second conductive member  20 . The outer peripheral surface  41 E is in contact with the first conductive member  10  and the second conductive member  20 . 
     A portion of the outer peripheral surface  41 E of the first insulating member  40 E in contact with the first conductive member  10  is fusion-bonded with the first conductive member  10 . A portion of the outer peripheral surface  41 E of the first insulating member  40 E in contact with the second conductive member  20  is not fusion-bonded with the second conductive member  20 . 
     The first insulating member  40 E has a hollow cylindrical shape. Thus, the first insulating member  40 E is easily crushed when the pressing force P is applied in comparison with a case where the first insulating member  40 E has a solid shape. Therefore, the first conductive member  10  and the second conductive member  20  easily come in contact with each other. 
       FIG. 6B  is a transverse sectional view showing a configuration of a pressure sensitive sensor  1 F. In the pressure sensitive sensor  1 F, shapes of a first conductive member  10 F and a first insulating member  40 F are different compared to the pressure sensitive sensor  1 . Other components than the first conductive member  10 F and the first insulating member  40 F have the same shapes as those of the pressure sensitive sensor  1 . 
     The first conductive member  10 F is a member formed into a substantially circular columnar shape. The first conductive member  10 F has a concave groove  12 F in the peripheral surface thereof to arrange the first insulating member  40 F. The groove  12 F is formed to spirally extend in a longitudinal direction of the first conductive member  10 F. 
     The first insulating member  40 F is a member formed into a circular columnar shape. The first insulating member  40 F is spirally arranged along the groove  12 F of the first conductive member  10 F. In the transverse sectional view, the diameter of the first insulating member  40 F is larger than the interval in the radial direction from the first conductive member  10 F to the second conductive member  20 . 
     The first insulating member  40 F is fusion-bonded with the first conductive member  10 F at the groove  12 F. A portion of the first insulating member  40 F in contact with the inner peripheral surface of the second conductive member  20  is not fusion-bonded with the second conductive member  20 . 
     Since the first insulating member  40 F is arranged in the groove  12 F of the first conductive member  10 F, it is easy to ensure a contact area between the first insulating member  40 F and the first conductive member  10 F. In other words, it is easy to ensure a fusion-bonding area between the first insulating member  40 F and the first conductive member  10 F. 
       FIG. 7A  is a transverse sectional view showing a configuration of a pressure sensitive sensor  1 G. In the pressure sensitive sensor  1 G, a shape of a first insulating member  40 G is different compared to the pressure sensitive sensor  1 . Other components than the first insulating member  40 G have the same shapes as those of the pressure sensitive sensor  1 . 
     The first insulating member  40 G is a member formed into a substantially circular columnar shape. In the transverse sectional view, the diameter of the first insulating member  40 G is larger than the interval in the radial direction from the first conductive member  10  to the second conductive member  20 . The first insulating member  40 G is spirally arranged along the circumferential surface of the first conductive member  10 . 
     The first insulating member  40 G has a concave groove  41 G in a circumferential surface thereof to arrange the first conductive member  10 . The first insulating member  40 G is fusion-bonded with the first conductive member  10  at the groove  41 G. A portion of the first insulating member  40 G in contact with the inner peripheral surface of the second conductive member  20  is not fusion-bonded with the second conductive member  20 . 
     Since the first conductive member  10  is arranged in the groove  41 G of the first insulating member  40 G, it is easy to ensure a contact area between the first insulating member  40 G and the first conductive member  10 . In other words, it is easy to ensure a fusion-bonding area between the first insulating member  40 G and the first conductive member  10 . 
       FIG. 7B  is a transverse sectional view showing a configuration of a pressure sensitive sensor  1 H. In the pressure sensitive sensor  1 H, shapes of a first conductive member  10 H, a first insulating member  40 H, and a second insulating member  50 H are different compared to the pressure sensitive sensor  1 . Other components than the first conductive member  10 H, the first insulating member  40 H and the second insulating member  50 H have the same shapes as those of the pressure sensitive sensor  1 . 
     The first conductive member  10 H is a member formed into a substantially circular columnar shape. The first conductive member  10 H has a concave groove  12 H in the peripheral surface thereof to arrange the first insulating member  40 H. The groove  12 H is formed to spirally extend in a longitudinal direction of the first conductive member  10 H. 
     The first insulating member  40 H is a member formed into a cylindrical shape. The first insulating member  40 H is spirally arranged along the groove  12 H of the first conductive member  10 H. In the transverse sectional view, the first insulating member  40 H has a shape having an outer peripheral surface  41 H and an inner peripheral surface  42 H. The diameter of the first insulating member  40 H is larger than an interval in the radial direction from the first conductive member  10 H to the second conductive member  20 . 
     The first insulating member  40 H is fusion-bonded with the first conductive member  10 H at the groove  12 H. A portion of the first insulating member  40 H in contact with the inner peripheral surface of the second conductive member  20  is not fusion-bonded with the second conductive member  20 . 
     The second insulating member  50 H is a member that covers the outer peripheral surface of the second conductive member  20  and that forms the outer shape of the pressure sensitive sensor  1 H. The second insulating member  50 H has a D-shaped outer shape in the transverse sectional view. 
     Specifically, the second insulating member  50 H has a curved surface  51 H extending along the second conductive member  20 , a pair of side surfaces  52 H,  52 H having planar shapes extending from both ends of the curved surface  51 H, and an end surface  53 H having a planar shape arranged between the pair of side surfaces  52 H,  52 H. 
     Since the second insulating member  50 H has the end surface  53 H, the pressure sensitive sensor  11 H can be easily arranged. That is, when the pressure sensitive sensor  1 H is arranged on a target, it becomes easy to stabilize an arrangement posture of the pressure sensitive sensor  1 H by placing the end surface  53 H in contact with the target. Stabilization of the arrangement posture of the pressure sensitive sensor  1 H facilitates the arrangement. 
       FIG. 8  is a transverse sectional view showing a configuration of a pressure sensitive sensor  1 J. In the pressure sensitive sensor  1 J, shapes of a first conductive member  10 J and a first insulating member  40 J are different compared to the pressure sensitive sensor  1 . Other components than the first conductive member  10 J and the first insulating member  40 J have the same shapes as those of the pressure sensitive sensor  1 . 
     The first conductive member  10 J is a member formed into a substantially circular columnar shape having an oval shape in the transverse sectional view. The first conductive member  10 J is formed so that the oval shape is rotated towards a longitudinal direction of the first conductive member  10 J. 
     The first conductive member  10 J has a concave groove  12 J in the peripheral surface thereof to arrange the first insulating member  40 J. More specifically, the groove  12 J is formed at a position where a minor axis of the oval shape and the peripheral surface of the oval shape intersect. 
     The first insulating member  40 J is a member formed into a cylindrical shape. The first insulating member  40 J is spirally arranged along the groove  12 J of the first conductive member  10 J. In the transverse sectional view, the first insulating member  40 J has a shape having an outer peripheral surface  41 J and an inner peripheral surface  42 J. The diameter of the first insulating member  40 J is larger than a maximum value of an interval in the radial direction from the first conductive member  10 J to the second conductive member  20 . 
     The first insulating member  40 J is fusion-bonded with the first conductive member  10 J at the groove  12 J. A portion of the first insulating member  40 J in contact with the inner peripheral surface of the second conductive member  20  is not fusion-bonded with the second conductive member  20 . 
     Since the cross-sectional shape of the first conductive member  10 J has an oval shape, it is easy to shorten the shortest distance between the first conductive member  10 J and the inner peripheral surface of the second conductive member  20 . Specifically, it is easy to shorten a distance from an intersection between the peripheral surface of the first conductive member  10 J and a major axis of the oval shape to the inner peripheral surface of the second conductive member  20  in comparison with a case where the first conductive member  10 J is formed into a circular shape. Thus, the first conductive member  10 J and the second conductive member  20  are easily brought into contact with each other. 
     Second Embodiment 
     Hereinafter, a pressure sensitive sensor according to a second embodiment of the present invention will be described with reference to  FIG. 9  to  FIG. 13B . The basic structure of the pressure sensitive sensor of the present embodiment is similar to that of the first embodiment; however, the number of the first insulating members is different from the first embodiment. Thus, in this embodiment, components associated with the first insulating member will be described with reference to  FIG. 9  to  FIG. 13B , and explanations of the same components will be omitted. 
     A pressure sensitive sensor  100  of the present embodiment includes, as shown in  FIG. 9 , the first conductive member  10 , the second conductive member  20 , first insulating members (corresponding to insulating members)  140 , and the second insulating member  50  as main components. 
     The first insulating members  140  are circular columnar members arranged together with the first conductive member  10  in the space  30  of the second conductive member  20 . The first insulating members  140  each have a diameter equal to the interval in the radial direction from the first conductive member  10  to the second conductive member  20 . 
     In this embodiment, three first insulating members  140  are arranged in the space  30 . In this embodiment, a description will be made of an example in which the three first insulating members  140  are arranged at equal intervals in a circumferential direction around the first conductive member  10 . 
     The first insulating members  140  may be arranged at equal intervals or may be arranged at unequal intervals. More specifically, the intervals are not limited as long as one first insulating member  140  is arranged on a virtual straight line L passing through the center of the first conductive member  10 . The number of the arranged first insulating members  140  may be three, or may be more than three. 
     In this embodiment, a description will be made of an example in which the second conductor  21  is arranged between the first insulating members  140  arranged next to each other in the circumferential direction. For example, a description will be made of an example in which the second conductor  21  is arranged in the middle of the adjacent first insulating members  140 . The second conductor  21  may be arranged in the middle of the adjacent first insulating members  140  or may be arranged in a position closer to either one of the first insulating members  140 . 
     In this embodiment, a description will be made of an example in which the first insulating members  140  are spirally arranged along the peripheral surface that is the surface of the first conductive member  10 . The first insulating members  140  may be arranged to linearly extend along a longitudinal direction of the first conductive member  10 . 
     The amount of movement (also referred to as “spiral pitch”) of the first insulating member  140  in the longitudinal direction produced while it goes around the first conductive member  10  one time can be appropriately set and is not particularly limited. Examples of a material forming the first insulating member  140  may include a rubber material, such as the polyolefin, having an insulating property. 
     In this embodiment, a portion of the first insulating member  140  in contact with the first conductive member  10  is fusion-bonded with the first conductive member  10 . In other words, the first insulating members  140  are fixed to the first conductive member  10 . On the other hand, a portion of the first insulating member  140  in contact with the second conductive member  20  is not fusion-bonded with the second conductive member  20 . In other words, the first insulating members  140  are movable relative to the second conductive member  20 . 
     In this embodiment, a description has been made of an example in which the first insulating members  140  and the first conductive member  10  are fusion-bonded, and the first insulating members  140  and the second conductive member  20  are not fusion-bonded; alternatively, a configuration may be adopted in which the first insulating members  140  and the first conductive member  10  are not fusion-bonded, and the first insulating members  140  and the second conductive member  20  are fusion-bonded. Furthermore, a configuration may be adopted in which the first insulating members  140  and the first conductive member  10  are not fusion-bonded and the first insulating members  140  and the second conductive member  20  are not fusion bonded. 
     In the pressure sensitive sensor  100  having the above-described configuration, a conductive state and an action when the pressure sensitive sensor  100  is bent are similar to those of the pressure sensitive sensor  1  of the first embodiment; and thus, such explanations are omitted. 
     With the pressure sensitive sensor  100  having the above-described configuration, the first conductive member  10  can be held and separated from the second conductive member  20  by the three first insulating members  140 . In comparison with the case of having one first insulating member  140 , the first conductive member  10  can be easily held and separated from the second conductive member  20 . 
     Since one first insulating member  140  is arranged on the virtual straight line L across the first conductive member  10 , the second conductive member  20  can be easily deformed when an external force is applied in a direction of the virtual straight line L in comparison with a case where two first insulating members  140  are arranged. That is, the second conductive member  20  and the first conductive member  10  easily come in contact with each other. Also, the pressure sensitive sensor  100  can be easily bent in the direction of the virtual straight line L. 
     The pressure sensitive sensor  100  is not limited to the shape described in the above embodiment, but may have other shapes. For example, the pressure sensitive sensor  100  may have various shapes as described below. 
       FIG. 10A  is a transverse sectional view showing a configuration of a pressure sensitive sensor  100 A. In the pressure sensitive sensor  100 A, shapes of first insulating members  140 A are different compared to the pressure sensitive sensor  100 . Other components than the first insulating members  140 A have the same shapes as those of the pressure sensitive sensor  100 . 
     Three first insulating members  140 A are members each formed into a rectangular columnar shape like the first insulating member  40 A. The three first insulating members  140 A are spirally arranged along the circumferential surface of the first conductive member  10 . The three first insulating members  140 A may be arranged to linearly extend along the longitudinal direction of the first conductive member  10 . 
     As in the case of the first insulating members  140 , the three first insulating members  140 A may be arranged at equal intervals in the circumferential direction around the first conductive member  10  or may be arranged at unequal intervals. The number of the arranged first insulating members  140 A may be three, or may be more than three. 
     The surface of the first insulating member  140 A in contact with the first conductive member  10  has a concavely curved shape along the peripheral surface of the first conductive member  10 , and is fusion-bonded with the first conductive member  10 . The surface of the first insulating member  140 A in contact with the second conductive member  20  has a convexly curved shape along the inner peripheral surface of the second conductive member  20 , and is not fusion-bonded with the second conductive member  20 . In other words, the first insulating members  140 A are movable relative to the second conductive member  20 . 
     In this embodiment, a description has been made of an example in which the first insulating members  140 A and the first conductive member  10  are fusion-bonded, and the first insulating members  140 A and the second conductive member  20  are not fusion-bonded; alternatively, a configuration may be adopted in which the first insulating members  140 A and the first conductive member  10  are not fusion-bonded, and the first insulating members  140 A and the second conductive member  20  are fusion-bonded. Furthermore, a configuration may be adopted in which the first insulating members  140 A and the first conductive member  10  are not fusion-bonded and the first insulating members  140 A and the second conductive member  20  are not fusion-bonded. 
       FIG. 10B  is a transverse sectional view showing a configuration of a pressure sensitive sensor  100 B. In the pressure sensitive sensor  100 B, shapes of a second conductive member  120 B and first insulating members  140 B are different compared to the pressure sensitive sensor  100 . Other components than the second conductive member  120 B and the first insulating members  140 B have the same shapes as those of the pressure sensitive sensor  100 . 
     The second conductive member  120 B is a cylindrical member having an internal space  30 , in which the first conductive member  10  and the first insulating members  140 B are arranged. The second conductive member  120 B has three slits  122 B, in which ends of the first insulating members  140 B are arranged. 
     The three slits  122 B are groove-shaped cutouts formed in the second conductive member  120 B and spirally extend in the longitudinal direction along a circumferential surface of the second conductive member  120 B. The three slits  122 B are arranged next to each other at equal intervals in the circumferential direction of the second conductive member  120 B or may be arranged at unequal intervals. 
     The second conductive member  120 B is divided into three portions by the three slits  122 B, and each of the three divided portions of the second conductive member  120 B has a second conductor  121 B arranged therein. The three second conductors  121 B are wire rods formed of a metallic material having conductivity. 
     The three first insulating members  140 B are members each formed into a rectangular columnar shape like the first insulating member  140 A. The three first insulating members  140 B are spirally arranged along the circumferential surface of the first conductive member  10 . The ends of the first insulating members  140 B on a second conductive member  120 B side pass through the insides of the slits  122 B and are in contact with the inner peripheral surface of the second insulating member  50 . 
     The first insulating members  140 B are not fusion-bonded with the second conductive member  120 B and the second insulating member  50 . In other words, the first insulating members  140 B are movable relative to the second conductive member  120 B and the second insulating member  50 . 
     In this embodiment, a description has been made of an example in which the slits  122 B and the first insulating members  140 B spirally extend; alternatively, the slits  122 B and the first insulating members  140 B may linearly extend. Each of the number of the slits  122 B and the number of the first insulating members  140 B may be three, or may be more than three. 
       FIG. 11A  is a transverse sectional view showing a configuration of a pressure sensitive sensor  100 C. In the pressure sensitive sensor  100 C, shapes of first insulating members  140 C are different compared to the pressure sensitive sensor  100 . Other components than the first insulating members  140 C have the same shapes as those of the pressure sensitive sensor  100 . 
     The three first insulating members  140 C are spirally arranged along the circumferential surface of the first conductive member  10 . In the transverse sectional view, the first insulating members  140 C each have a shape extending in the radial direction from the first conductive member  10  towards the second conductive member  20 , and each have a shape with recesses  41 C. 
     The surface of the first insulating member  140 C in contact with the first conductive member  10  has a concavely curved shape along the peripheral surface of the first conductive member  10 , and is fusion-bonded with the first conductive member  10 . The surface of the first insulating member  140 C in contact with the second conductive member  20  has a convexly curved shape along the inner peripheral surface of the second conductive member  20 , and is not fusion-bonded with the second conductive member  20 . In other words, the first insulating members  140 C are movable relative to the second conductive member  20 . 
     The recess  41 C is provided in each of a pair of surfaces of the first insulating member  140 C extending between the first conductive member  10  and the second conductive member  20 . In this embodiment, a description will be made of an example in which the recesses  41 C are grooves each having a substantially V-shape formed in the first insulating members  140 C. 
     With the pair of recesses  41 C, the first insulating member  140 C can have a part narrow in width and can easily buckle (or bend) in comparison with the case where the recesses  41 C are not provided. 
     In this embodiment, a description has been made of an example in which the pair of recesses  41 C is provided; alternatively, only one recess  41 C may be provided. The shape of the recess  41 C may be a V-shape or may be any other shape, such as a U-shape, which allows the first insulating member  140 C to easily buckle. 
     In this embodiment, a description has been made of an example in which the first insulating members  140 C spirally extend; alternatively, the first insulating members  140 C may linearly extend. The number of the arranged first insulating members  140 C may be three, or may be more than three. 
       FIG. 11B  is a transverse sectional view showing a configuration of a pressure sensitive sensor  100 D. In the pressure sensitive sensor  100 D, shapes of first insulating members  140 D are different compared to the pressure sensitive sensor  100 . Other components than the first insulating members  140 D have the same shapes as those of the pressure sensitive sensor  100 . 
     The three first insulating members  140 D are spirally arranged along the circumferential surface of the first conductive member  10 . The first insulating members  140 D each have a curved rectangular shape extending in the radial direction from the first conductive member  10  towards the second conductive member  20  in the transverse sectional view. 
     The surface of the first insulating member  140 D in contact with the first conductive member  10  has a concavely curved shape along the peripheral surface of the first conductive member  10 , and is fusion-bonded with the first conductive member  10 . The surface of the first insulating member  140 D in contact with the second conductive member  20  has a convexly curved shape along the inner peripheral surface of the second conductive member  20 , and is not fusion-bonded with the second conductive member  20 . In other words, the first insulating members  140 D are movable relative to the second conductive member  20 . 
     In the first insulating member  140 D, one surface  141 D of a pair of surfaces extending between the first conductive member  10  and the second conductive member  20  has a convexly curved shape. The other surface  142 D of the pair of surfaces has a concavely curved shape. 
     In this embodiment, a description has been made of an example in which the first insulating member  140 D has a shape convexly curved in the counterclockwise direction in  FIG. 11B ; alternatively, the first insulating member  140 D may have a shape convexly curved in the clockwise direction. 
     In this embodiment, a description has been made of an example in which the first insulating members  140 D spirally extend; alternatively, the first insulating members  140 D may linearly extend. The number of the arranged first insulating members  140 D may be three, or may be more than three. 
       FIG. 12A  is a transverse sectional view showing a configuration of a pressure sensitive sensor  100 E. In the pressure sensitive sensor  100 E, shapes of first insulating members  140 E are different compared to the pressure sensitive sensor  100 . Other components than the first insulating members  140 E have the same shapes as those of the pressure sensitive sensor  100 . 
     The three first insulating members  140 E are members each formed into a cylindrical shape. The first insulating members  140 E are spirally arranged along the circumferential surface of the first conductive member  10 . In the transverse sectional view, the first insulating members  140 E each have a shape having an outer peripheral surface  141 E and an inner peripheral surface  142 E. The outer peripheral surface  141 E is in contact with the first conductive member  10  and the second conductive member  20 . 
     A portion of the outer peripheral surface  141 E of the first insulating member  140 E in contact with the first conductive member  10  is fusion-bonded with the first conductive member  10 . A portion of the outer peripheral surface  141 E of the first insulating member  140 E in contact with the second conductive member  20  is not fusion-bonded with the second conductive member  20 . In other words, the first insulating members  140 E are movable relative to the second conductive member  20 . 
     In this embodiment, a description has been made of an example in which the first insulating members  140 E spirally extend; alternatively, the first insulating members  140 E may linearly extend. The number of the arranged first insulating members  140 E may be three, or may be more than three. 
       FIG. 12B  is a transverse sectional view showing a configuration of a pressure sensitive sensor  100 F. In the pressure sensitive sensor  100 F, shapes of a first conductive member  110 F and first insulating members  140 F are different compared to the pressure sensitive sensor  100 . Other components than the first conductive member  110 F and the first insulating members  140 F have the same shapes as those of the pressure sensitive sensor  100 . 
     The first conductive member  110 F is a member formed into a substantially circular columnar shape. The first conductive member  110 F has three concave grooves  112 F in the peripheral surface thereof to arrange the first insulating members  140 F. The grooves  112 F are formed to spirally extend in a longitudinal direction of the first conductive member  110 F. 
     The first insulating members  140 F are members each formed into a circular columnar shape. The first insulating members  140 F are spirally arranged along the grooves  112 F of the first conductive member  110 F. In the transverse sectional view, the diameter of the first insulating member  140 F is larger than the interval in the radial direction from the first conductive member  110 F to the second conductive member  20 . 
     The first insulating members  140 F are fusion-bonded with the first conductive member  110 F at the grooves  112 F. A portion of the first insulating member  140 F in contact with the inner peripheral surface of the second conductive member  20  is not fusion-bonded with the second conductive member  20 . In other words, the first insulating members  140 F are movable relative to the second conductive member  20 . 
     In this embodiment, a description has been made of an example in which the first insulating members  140 F and the grooves  112 F spirally extend; alternatively, the first insulating members  140 F and the grooves  112 F may linearly extend. Each of the number of the first insulating members  140 F and the number of the grooves  112 F may be three, or may be more than three. 
       FIG. 13A  is a transverse sectional view showing a configuration of a pressure sensitive sensor  100 G. In the pressure sensitive sensor  100 G, shapes of first insulating members  140 G are different compared to the pressure sensitive sensor  100 . Other components than the first insulating members  140 G have the same shapes as those of the pressure sensitive sensor  100 . 
     The three first insulating members  140 G are members each formed into a substantially circular columnar shape. In the transverse sectional view, the diameter of the first insulating member  140 G is larger than the interval in the radial direction from the first conductive member  10  to the second conductive member  20 . The first insulating members  140 G are spirally arranged along the circumferential surface of the first conductive member  10 . 
     The first insulating members  140 G each have a concave groove  141 G in a circumferential surface thereof to arrange the first conductive member  10 . The first insulating members  140 G are fusion-bonded with the first conductive member  10  at the grooves  141 G. A portion of the first insulating member  140 G in contact with the inner peripheral surface of the second conductive member  20  is not fusion-bonded with the second conductive member  20 . In other words, the first insulating members  140 G are movable relative to the second conductive member  20 . 
     In this embodiment, a description has been made of an example in which the first insulating members  140 G spirally extend; alternatively, the first insulating members  140 G may linearly extend. The number of the first insulating members  140 G may be three, or may be more than three. 
       FIG. 13B  is a transverse sectional view showing a configuration of a pressure sensitive sensor  100 H. In the pressure sensitive sensor  100 H, shapes of a first conductive member  110 H, first insulating members  140 H, and a second insulating member  150 H are different compared to the pressure sensitive sensor  100 . Other components than the first conductive member  110 H, the first insulating members  140 H, and the second insulating member  150 H have the same shapes as those of the pressure sensitive sensor  100 . 
     The first conductive member  110 H is a member formed into a substantially circular columnar shape. The first conductive member  110 H has concave grooves  112 H in the peripheral surface thereof to arrange the first insulating members  140 H. The grooves  112 H are formed to spirally extend in a longitudinal direction of the first conductive member  110 H. 
     The first insulating members  140 H are members each formed into a cylindrical shape. The first insulating members  140 H are spirally arranged along the grooves  112 H of the first conductive member  110 H. In the transverse sectional view, the first insulating members  140 H each have a shape having an outer peripheral surface  141 H and an inner peripheral surface  142 H. The diameter of the first insulating member  140 H is larger than the interval in the radial direction from the first conductive member  110 H to the second conductive member  20 . 
     The first insulating members  140 H are fusion-bonded with the first conductive member  1101 H at the grooves  112 H. A portion of the first insulating member  140 H in contact with the inner peripheral surface of the second conductive member  20  is not fusion-bonded with the second conductive member  20 . In other words, the first insulating members  110 H are movable relative to the second conductive member  20 . 
     The second insulating member  150 H is a cylindrical member that covers the outer peripheral surface of the second conductive member  20  and that forms the outer shape of the pressure sensitive sensor  100 H. The second insulating member  150 H has a D-shaped outer shape in the transverse sectional view. 
     Specifically, the second insulating member  150 H has a curved surface  151 H extending along the second conductive member  20 , a pair of side surfaces  152 H,  152 H having planar shapes extending from both ends of the curved surface  151 H, and an end surface  153 H having a planar shape arranged between the pair of side surfaces  152 H,  152 H. 
     In this embodiment, a description has been made of an example in which the first insulating members  140 H and the grooves  11211  spirally extend; alternatively, the first insulating members  140 H and the grooves  112 H may linearly extend. Each of the number of the first insulating members  140 H and the number of the grooves  112 H may be three, or may be more than three. 
     The technical scope of the present invention is not limited to the above-described embodiments and various modifications can be made within a range not deviating from a gist of the present invention. 
     For example, in the above-described embodiments, the pressure sensitive sensor has been described in an example in which the pressing force is detected based on the conductivity between the first conductive member and the second conductive member; alternatively, the pressing force may be detected based on a change of capacitance between the first conductive member and the second conductive member. 
     The present invention is not limited to the above-described embodiments, and may be applied to embodiments appropriately combined with any of these embodiments.