Patent Publication Number: US-2023160919-A1

Title: Low Heat-Resistant Sensor

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is the United States national phase of International Application No. PCT/JP2020/036579 filed Sep. 28, 2020, and claims priority to Japanese Patent Application No. 2019-190082 filed Oct. 17, 2019, the disclosures of which are hereby incorporated by reference in their entirety. 
    
    
     TECHNICAL FIELD 
     The present invention relates to a low heat-resistant sensor that is used for industrial equipment such as a vibration-measuring instrument. 
     BACKGROUND ART 
     Various sensors such as an acceleration sensor, a temperature sensor, and a pressure sensor have been used for various kinds of industrial equipment. Such a sensor mainly includes a sensor body that contains a sensor unit that acquires various kinds of information in a housing and a cable that is electrically connected to the sensor unit of the sensor body. 
     In particular, for the housing of the sensor body, a metal material such as stainless steel or aluminum is used for the purpose of, for example, strength, a measure against a noise, or heat resistance, or a resin material is used for the purpose of, for example, insulation or a reduction in weight. 
     In some manufacturing sites such as factories, chemicals such as acid or alkaline chemicals are used, and industrial equipment is exposed to the chemicals. Sensor bodies or cables are coated with fluorine resin by being fired at a high temperature of 300 degrees or more, and consequently, many sensors that are exposed to the chemicals and that are used for industrial equipment typically have chemical resistance (for example, JPA 2016-130633). 
     SUMMARY OF INVENTION 
     Technical Problem 
     However, as for a low heat-resistant sensor the heat resistance temperature of which is low, which is represented by an acceleration sensor, among various sensors, the heat resistance temperature of a sensor unit of a sensor body is about 85 degrees or a low temperature of about 60 degrees in some cases, there is a possibility that the sensor unit is damaged in the case where a housing that contains the sensor unit is coated with fluorine resin as it is, and the sensor body cannot be coated with fluorine resin. 
     It is possible that only a cable is coated with fluorine resin, and that only the housing is coated with fluorine resin before containing the sensor unit. In this case, however, it is necessary that after the cable and the housing are separately coated with fluorine resin, that the sensor unit is disposed in the housing, and that the cable and the sensor body are electrically connected to each other. For this reason, the low heat-resistant sensor has a structure in which a small gap appears between the sensor body and the cable and cannot certainly prevent chemicals from entering the sensor body from a portion at which the sensor body and the cable are connected to each other. 
     From the possibility of the entering of the chemicals, entering of water or dust is naturally assumed. These adversely affect the precision of the low heat-resistant sensor. For this reason, there is a need for development of a low heat-resistant sensor that is resistant to these. 
     The present invention has been accomplished in view of such circumstances, and it is an object of the present invention to provide a low heat-resistant sensor that has high chemical resistance, excellent drip-proof properties, and excellent dust-proof properties. 
     Solution to Problem 
     The present invention is invented to solve the problem of the existing technique described above. A low heat-resistant sensor according to the present invention includes a sensor body that includes a sensor unit that is disposed in a housing, and a cable that is electrically connected to the sensor unit of the sensor body. The housing of the sensor body is composed of fluorine resin, and the cable is covered by a tube composed of fluorine resin. A portion at which the housing and the tube are connected to each other is thermally bonded, and the housing and the tube are integrally formed. 
     In the case where the housing composed of fluorine resin and the tube composed of fluorine resin are thus integrally formed, there are no gaps in the entire low heat-resistant sensor, that is, the sensor unit and the cable are completely covered with the fluorine resin. For this reason, the low heat-resistant sensor has high chemical resistance, excellent drip-proof properties, and excellent dust-proof properties. 
     In the low heat-resistant sensor according to the present invention, the housing and the tube are thermally bonded to each other with a connection member that is composed of fluorine resin interposed therebetween. 
     A load is likely to be applied to the portion at which the housing and the tube are connected to each other, and repeated use rises the possibility of the appearance of a gap. However, in the case where the housing and the tube are thus thermally bonded to each other with the connection member that is composed of fluorine resin interposed therebetween, no gap appears between the housing and the tube due to the repeated use, and the low heat-resistant sensor can maintain high chemical resistance, excellent drip-proof properties, and excellent dust-proof properties. 
     In the low heat-resistant sensor according to the present invention, the housing includes a container that contains the sensor unit in a recessed portion and that is composed of fluorine resin, a plate that serves as a lid covering an opening of the recessed portion and that is composed of fluorine resin, and a frame body that is disposed such that the frame body surrounds a perimeter of the plate and that is composed of fluorine resin. The frame body and the container are thermally bonded to each other, and the frame body and the plate are thermally bonded to each other. 
     In the case where the frame body and the container are thus thermally bonded to each other, and the frame body and the plate are thus thermally bonded to each other, the sensor unit can be sealed in the housing without contact with the sensor unit, and the sensor unit can be prevented from being damaged due to heating during thermal bonding with certainty. 
     In the low heat-resistant sensor according to the present invention, the fluorine resin is polytetrafluoroethylene (PTFE) resin, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) resin, tetrafluoroethylene-hexafluoropropylene copolymer (FEP) resin, tetrafluoroethylene-ethylene copolymer (ETFE) resin, polyvinylidene fluoride (PVDF) resin, polychlorotrifluoroethylene (PCTFE) resin, chlorotrifluoroethylene-ethylene copolymer (ECTFE) resin, or polyvinyl fluoride (PVF) resin. 
     Such fluorine resin enables the low heat-resistant sensor to have particularly high chemical resistance, excellent drip-proof properties, and excellent dust-proof properties. 
     In the low heat-resistant sensor according to the present invention, the frame body and the connection member are composed of tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) resin. 
     In the low heat-resistant sensor according to the present invention, the container, the plate, and the tube are composed of polytetrafluoroethylene (PTFE) resin. 
     In the case where the frame body and the connection member are thus composed of the PFA resin, and the container, the plate, and the tube are thus composed of the PTFE resin, the container, the plate, and the tube hardly deform because the melting point of the PFA resin is lower than that of the PTFE resin, the frame body and the container can be thermally bonded to each other, the frame body and the plate can be thermally bonded to each other, the connection member and the container can be thermally bonded to each other, and the connection member and the tube can be thermally bonded to each other. 
     In the low heat-resistant sensor according to the present invention, the low heat-resistant sensor is MEMS (Micro Electro Mechanical Systems) or a pickup. 
     In the case where the low heat-resistant sensor is thus the MEMS or the pickup, characteristic structures according to the present invention can be suitably used. 
     The low heat-resistant sensor according to the present invention is an acceleration sensor. 
     In the case of the acceleration sensor as above, the effects of the structures according to the present invention can be increased. 
      A method of manufacturing a low heat-resistant sensor according to the present invention includes a step of disposing a sensor unit in a recessed portion of a container composed of fluorine resin, inserting a cable into a through-hole in communication with the recessed portion, and electrically connecting the sensor unit that is disposed in the recessed portion and the cable to each other, a step of disposing a plate composed of fluorine resin such that the plate covers an opening of the recessed portion and capping the recessed portion, a step of covering the cable by using a tube composed of fluorine resin, a step of disposing a frame body composed of fluorine resin such that the frame body surrounds the perimeter of the plate, a step of thermally bonding the frame body, the container, and the plate to each other, and a step of thermally bonding the container and the tube to each other. 
     The manufacturing method enables the low heat-resistant sensor that has high chemical resistance, excellent drip-proof properties, and excellent dust-proof properties to be manufactured because an integrally formed structure in which the sensor unit and the cable are completely covered with the fluorine resin is acquired. 
     In the method of manufacturing the low heat-resistant sensor according to the present invention, the step of thermally bonding the frame body, the container, and the plate to each other includes melting a part of the frame body by pressing the frame body against the sensor unit while heating the frame body, thermally bonding the frame body and the container to each other, and thermally bonding the frame body and the plate to each other. 
     In the case where the frame body and the container are thermally bonded to each other, and the frame body and the plate are thermally bonded to each other by pressing the frame body while heating the frame body as above, the sensor unit is not heated, the sensor unit can be sealed in the housing, and the sensor unit can be prevented from being damaged due to heating with certainty. 
     In the method of manufacturing the low heat-resistant sensor according to the present invention, the step of thermally bonding the container and the tube to each other includes thermally bonding the container and the tube to each other with a connection member that is composed of fluorine resin interposed therebetween. 
     In the method of manufacturing the low heat-resistant sensor according to the present invention, a part of the connection member is melted by pressing the connection member against the recessed portion while heating the connection member, the connection member and the container are thermally bonded to each other, and the connection member and the tube are thermally bonded to each other. 
     In the case where the container and the tube are thermally bonded to each other with the connection member that is composed of fluorine resin interposed therebetween, no gap appears at a portion at which the container and the tube are connected to each other even due to continuous use, and the low heat-resistant sensor that maintains high chemical resistance, excellent drip-proof properties, and excellent dust-proof properties can be manufactured. 
     Advantageous Effects of Invention 
     A low heat-resistant sensor according to the present invention has high chemical resistance, excellent drip-proof properties, and excellent dust-proof properties because a housing of a sensor body is composed of fluorine resin, a cable is covered by a tube composed of fluorine resin, and an integrally formed structure in which the housing and the tube are thermally bonded to each other is acquired. 
     A method of manufacturing a low heat-resistant sensor according to the present invention does not damage a sensor unit and enables the low heat-resistant sensor that has high chemical resistance, excellent drip-proof properties, and excellent dust-proof properties to be manufactured with certainty because an integrally formed structure in which the sensor unit and a cable are completely covered with fluorine resin can be acquired, and the sensor unit is not heated to a high temperature during manufacturing. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a perspective view of a low heat-resistant sensor according to a first embodiment of the present invention. 
         FIG.  2    is a sectional view of the low heat-resistant sensor according to the first embodiment of the present invention illustrated in  FIG.  1    taken along line A-A. 
         FIG.  3    is an exploded perspective view of the low heat-resistant sensor according to the first embodiment of the present invention. 
         FIG.  4    is a perspective view of a low heat-resistant sensor according to a second embodiment of the present invention. 
         FIG.  5    is a sectional view of the low heat-resistant sensor according to the second embodiment of the present invention illustrated in  FIG.  4    taken along line B-B. 
         FIG.  6    is an exploded perspective view of the low heat-resistant sensor according to the second embodiment of the present invention. 
         FIG.  7    illustrate process diagrams illustrating the manufacturing processing of the low heat-resistant sensor according to the first embodiment of the present invention. 
         FIG.  8    illustrate process diagrams illustrating the manufacturing processing of the low heat-resistant sensor according to the first embodiment of the present invention. 
         FIG.  9    is a perspective view similar to the process diagram illustrated in  FIG.  8   (a). 
         FIG.  10    is a perspective view similar to the process diagram illustrated in  FIG.  8   (c). 
         FIG.  11    illustrates a process diagram illustrating a manufacturing process of the low heat-resistant sensor according to the first embodiment of the present invention. 
         FIG.  12    illustrates a process diagram illustrating a manufacturing process of the low heat-resistant sensor according to the first embodiment of the present invention. 
         FIG.  13    illustrates a process diagram illustrating a manufacturing process of the low heat-resistant sensor according to the first embodiment of the present invention. 
         FIG.  14    illustrate process diagrams illustrating the manufacturing processing of the low heat-resistant sensor according to the second embodiment of the present invention. 
         FIG.  15    illustrate process diagrams illustrating the manufacturing processing of the low heat-resistant sensor according to the second embodiment of the present invention. 
         FIG.  16    illustrates a process diagram illustrating a manufacturing process of the low heat-resistant sensor according to the second embodiment of the present invention. 
         FIG.  17    illustrates a process diagram illustrating a manufacturing process of the low heat-resistant sensor according to the second embodiment of the present invention. 
         FIG.  18    illustrates a process diagram illustrating a manufacturing process of the low heat-resistant sensor according to the second embodiment of the present invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Embodiments of the present invention will hereinafter be described in detail with reference to the drawings. 
     Low Heat-Resistant Sensor  10   
     A low heat-resistant sensor  10  according to the present invention is a heat-sensitive sensor the heat resistance temperature of which is 100 degrees or less and is not particularly limited to any sensor. In particular, a sensor unit  26  described later includes, for example, a substrate or an integrated circuit in some cases, and these are heat-sensitive depending on the sensor in some cases. As for the low heat-resistant sensor  10  that includes the sensor unit  26  that is thus heat-sensitive, the present invention provides the low heat-resistant sensor  10  that has high chemical resistance, excellent drip-proof properties, and excellent dust-proof properties and a method of manufacturing the low heat-resistant sensor  10 . An acceleration sensor can be taken as an example of the low heat-resistant sensor  10 . 
     As illustrated in  FIG.  1    to  FIG.  3   , the low heat-resistant sensor  10  according to a first embodiment of the present invention includes a sensor body  20  that includes the sensor unit  26  that is disposed in a housing  22  and a cable  40  that is electrically connected to the sensor unit  26  of the sensor body  20 . 
     The housing  22  of the sensor body  20  is composed of fluorine resin. The cable  40  is covered by a tube  42  composed of fluorine resin. A portion at which the housing  22  and the tube  42  are connected to each other is thermally bonded, and the housing  22  and the tube  42  are integrally formed. 
      The structure of the housing  22  is not particularly limited provided that the sensor unit  26  is firmly contained in an interior space and can cover the entire sensor unit  26  with certainty. 
     As illustrated in  FIG.  1    to  FIG.  3   , the housing  22  includes a container  32  that has a substantially rectangular cuboid shape and that includes a recessed portion  24  at the center, a plate  28  that is disposed above the sensor unit  26  and on a step portion  23  provided along the edge of an opening of the recessed portion  24  with the sensor unit  26  disposed in the recessed portion  24 , that serves as a lid for the recessed portion  24 , and that is composed of fluorine resin, and a frame body  30  that is disposed on a step portion  27  provided around the plate  28 , that surrounds the plate  28 , and that is composed of fluorine resin. In  FIG.  1    and  FIG.  3   , reference signs  21  represent mounting holes that are used when the low heat-resistant sensor  10  is mounted on a mating member (not illustrated) by using a fastener, and the mounting holes  21  are through-holes that are not in communication with the recessed portion  24  of the housing  22  and that are independent. 
     In the case of the present example, the mounting holes  21  are provided at four positions, but the number is not particularly limited, and the mounting holes  21  themselves may not be provided. In the case where the mounting holes  21  are not provided, the low heat-resistant sensor  10  is mounted on the mating member (not illustrated) by using double-sided tape or an adhesive. 
     An integrally formed structure in which the frame body  30  and the container  32  are thermally bonded to each other and in which the frame body  30  and the plate  28  are thermally bonded to each other is acquired by pressing the frame body  30  while heating the frame body  30  as described later. 
     That is, a part of the frame body  30  is melted by being heated, the plate  28  and the container  32  are thermally bonded to each other with the frame body  30  interposed therebetween, and the frame body  30 , the container  32 , and the plate  28  are integrally formed. 
     The sensor unit  26  that is provided in the recessed portion  24  of the container  32  may be secured to the recessed portion  24  in any way but is preferably secured by using an adhesive  29 . That is, the container  32  and the sensor unit  26  are integrally formed when the adhesive  29  is applied to the bottom surface of the recessed portion  24 , the sensor unit  26  is disposed in the recessed portion  24  in this state, and the adhesive  29  is solidified. A low-siloxane content adhesive, for example, can be used as the adhesive  29 . 
     A through-hole  25  in communication with the recessed portion  24  is provided in a side surface (a right-hand side surface in  FIG.  1    to  FIG.  3   ) of the housing  22 . The cable  40  is inserted in the through-hole  25 . The sensor unit  26  that is disposed in the recessed portion  24  and the cable  40  are electrically connected to each other by using, for example, solder  45 . 
     The cable  40  that is electrically connected is covered by the tube  42  composed of fluorine resin. An end portion (a lefthand end portion in  FIG.  1    and  FIG.  2   ) of the tube  42  is inserted in the through-hole  25 . 
     A step portion  41  for the tube  42  is provided in the through-hole  25 . Consequently, the position of the tube  42  in the housing  22  is determined. 
     In addition, as illustrated in  FIG.  2   , a portion at which the tube  42  and the housing  22  are connected to each other is thermally bonded by using a connection member  50  composed of fluorine resin. That is, the connection member  50  is inserted in an end portion of the through-hole  25  of the housing  22 . In this state, a part of the connection member  50  is melted by pressing the connection member  50  while heating the connection member  50 . Consequently, the housing  22  (the container  32 ) and the tube  42  are thermally bonded to each other with the connection member  50  interposed therebetween and are integrally formed. 
     A step portion  43  for the connection member  50  is provided at the end portion of the through-hole  25  (a right-hand end portion in  FIGS.  1  and  2   ). Consequently, the position of the connection member  50  at the side surface (the right-hand side surface in  FIG.  1    to  FIG.  3   ) of the housing  22  is determined. 
     Examples of the fluorine resin that is the materials of the housing  22 , the plate  28 , the frame body  30 , the tube  42 , and the connection member  50  include polytetrafluoroethylene (PTFE) resin, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) resin, tetrafluoroethylene-hexafluoropropylene copolymer (FEP) resin, tetrafluoroethylene-ethylene copolymer (ETFE) resin, polyvinylidene fluoride (PVDF) resin, polychlorotrifluoroethylene (PCTFE) resin, chlorotrifluoroethylene-ethylene copolymer (ECTFE) resin, and polyvinyl fluoride (PVF) resin. 
     Among these, fluorine resin having a relatively low melting point is preferably selected for the frame body  30  and the connection member  50  because these are directly heated, and fluorine resin having a melting point higher than that of the fluorine resin that is used for the frame body  30  and the connection member  50  is preferably selected for the housing  22 , the plate  28 , and the tube  42 . 
     In particular, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) resin is preferably used for the frame body  30  and the connection member  50 , and polytetrafluoroethylene (PTFE) resin is preferably used for the housing  22 , the plate  28 , and the tube  42 . 
     However, these combinations are not particularly limited, and the resin of each of the housing  22 , the plate  28 , the frame body  30 , the tube  42 , and the connection member  50  may be changed and is freely selected appropriately. 
     As for the low heat-resistant sensor  10  according to the first embodiment of the present invention, the frame body  30  and the container  32  are thermally bonded to each other, and the frame body  30  and the plate  28  are thermally bonded to each other in the sensor body  20 . Consequently, the integrally formed structure can be acquired by sealing the sensor unit  26  in the housing  22  without direct contact with the sensor unit  26 , and the sensor unit  26  can be prevented from being damaged due to heating during thermal bonding with certainty, as described above. 
     In addition, since the cable  40  is covered by the tube  42 , and the tube  42  and the housing  22  are thermally bonded to each other into the integrally formed structure, there are no gaps anywhere, and the low heat-resistant sensor  10  that has high chemical resistance, excellent drip-proof properties, and excellent dust-proof properties can be provided. 
     A low heat-resistant sensor  10  according to a second embodiment of the present invention will now be described. 
     The low heat-resistant sensor  10  illustrated in  FIG.  4    to  FIG.  6    basically has the same structure as that of the low heat-resistant sensor  10  according to the first embodiment illustrated in  FIG.  1    to  FIG.  3   . Accordingly, like components are designated by like reference signs, and the detailed description thereof is omitted. 
     As illustrated in  FIG.  4    to  FIG.  6   , the low heat-resistant sensor  10  according to the second embodiment of the present invention includes the sensor body  20  that includes the sensor unit  26  that is disposed in the housing  22  that has a substantially cylindrical shape and the cable  40  that is electrically connected to the sensor unit  26  of the sensor body  20 . As for the sensor unit  26 , a support plate  88  is mounted on a bottom portion by using a fastener  90 . 
     The housing  22  of the sensor body  20  is composed of fluorine resin. The cable  40  is covered by the tube  42  composed of fluorine resin. A portion at which the housing  22  and the tube  42  are connected to each other is thermally bonded, and the housing  22  and the tube  42  are integrally formed. 
     As illustrated in  FIG.  4    to  FIG.  6   , the housing  22  includes the container  32  that has a substantially cylindrical shape and that includes the recessed portion  24  at the center, the plate  28  that is disposed above the sensor unit  26  and on a step portion  86  provided along the edge of an opening of the recessed portion  24  with the sensor unit  26  disposed in the recessed portion  24 , that serves as a lid for the opening of the recessed portion  24 , and that is composed of fluorine resin, and the frame body  30  that is provided around the plate  28 , that is disposed on the step portion  86 , that surrounds the plate  28 , and that is composed of fluorine resin. 
     The support plate  88  that is provided on the bottom portion of the sensor unit  26  is accurately fitted to a bottom portion of the recessed portion  24 . Consequently, the sensor unit  26  can be held in the housing  22  with certainty. 
     A flange portion  33  that is provided at the lower end of the housing  22  has the mounting holes  21  that are used when the low heat-resistant sensor  10  is mounted on the mating member (not illustrated) by using a fastener. The mounting holes  21  are through-holes that are not in communication with the recessed portion  24  of the housing  22  and that are independent. 
     In the case of the present embodiment, the mounting holes  21  are provided at three positions, but the number is not particularly limited, and the mounting holes  21  themselves may not be provided. In the case where the mounting holes  21  are not provided, the low heat-resistant sensor  10  is mounted on the mating member (not illustrated) by using double-sided tape or an adhesive. 
     An integrally formed structure in which the frame body  30  and the container  32  are thermally bonded to each other and in which the frame body  30  and the plate  28  are thermally bonded to each other is acquired by pressing the frame body  30  while heating the frame body  30  as described later. 
     That is, a part of the frame body  30  is melted by being heated, the plate  28  and the container  32  are thermally bonded to each other with the frame body  30  interposed therebetween, and the frame body  30 , the container  32 , and the plate  28  are integrally formed. 
     The sensor unit  26  that is provided in the recessed portion  24  of the container  32  may be secured to the recessed portion  24  in any way but is preferably secured by using the adhesive  29 . That is, the container  32  and the sensor unit  26  are integrally formed with the support plate  88  interposed therebetween when the adhesive  29  is applied to the bottom portion of the recessed portion  24 , the sensor unit  26 , together with the support plate  88 , is disposed in the recessed portion  24  in this state, and the adhesive  29  is solidified. A low-siloxane content adhesive, for example, can be used as the adhesive  29 . 
      The through-hole  25  in communication with the recessed portion  24  is provided in a side surface (a right-hand side surface in  FIG.  4    to  FIG.  6   ) of the housing  22 . The cable  40  is inserted in the through-hole  25 . An engagement projecting portion  85  of the sensor unit  26  that is disposed in the recessed portion  24  and an engagement recessed portion  84  that is provided at an end portion of the cable  40  are electrically connected to each other by recess-projection engagement. The sensor unit  26  and the cable  40  are not limited by electrical connection made by the recess-projection engagement, but soldering, for example, may be acceptable. As for the engagement recessed portion  84  and the engagement projecting portion  85 , a projecting portion and a recessed portion may be conversely provided. 
     The cable  40  that is electrically connected is covered by the tube  42  composed of fluorine resin. An end portion (a lefthand end portion in  FIG.  4    and  FIG.  5   ) of the tube  42  is inserted in the through-hole  25 . 
     In addition, as illustrated in  FIG.  4    and  FIG.  5   , a portion at which the tube  42  and the housing  22  are connected to each other is thermally bonded by using the connection member  50  composed of fluorine resin. That is, the connection member  50  is inserted in the end portion of the through-hole  25  of the housing  22 . In this state, a part of the connection member  50  is melted by pressing the connection member  50  while heating the connection member  50 . Consequently, the housing  22  (the container  32 ) and the tube  42  are thermally bonded to each other with the connection member  50  interposed therebetween and are integrally formed. 
     A flange portion  51  is provided on the connection member  50 . Consequently, when the connection member  50  is fitted into the through-hole  25 , the flange portion  51  prevents the connection member  50  from excessively entering the back of the through-hole  25 . 
     Examples of the fluorine resin that is the materials of the housing  22 , the plate  28 , the frame body  30 , the tube  42 , and the connection member  50  include polytetrafluoroethylene (PTFE) resin, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) resin, tetrafluoroethylene-hexafluoropropylene copolymer (FEP) resin, tetrafluoroethylene-ethylene copolymer (ETFE) resin, polyvinylidene fluoride (PVDF) resin, polychlorotrifluoroethylene (PCTFE) resin, chlorotrifluoroethylene-ethylene copolymer (ECTFE) resin, and polyvinyl fluoride (PVF) resin. 
     Among these, fluorine resin having a relatively low melting point is preferably selected for the frame body  30  and the connection member  50  because these are directly heated, and fluorine resin having a melting point higher than that of the fluorine resin that is used for the frame body  30  and the connection member  50  is preferably selected for the housing  22 , the plate  28 , and the tube  42 . 
     In particular, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) resin is preferably used for the frame body  30  and the connection member  50 , and polytetrafluoroethylene (PTFE) resin is preferably used for the housing  22 , the plate  28 , and the tube  42 . 
     However, these combinations are not particularly limited, and the resin of each of the housing  22 , the plate  28 , the frame body  30 , the tube  42 , and the connection member  50  may be changed and is freely selected appropriately. 
     As for the low heat-resistant sensor  10  according to the second embodiment of the present invention, the frame body  30  and the container  32  are thermally bonded to each other, and the frame body  30  and the plate  28  are thermally bonded to each other in the sensor body  20 . Consequently, the integrally formed structure can be acquired by sealing the sensor unit  26  in the housing  22  without direct contact with the sensor unit  26 , and the sensor unit  26  can be prevented from being damaged due to heating during thermal bonding with certainty, as described above. 
     In addition, since the cable  40  is covered by the tube  42 , and the tube  42  and the housing  22  are thermally bonded to each other into the integrally formed structure, there are no gaps anywhere, and the low heat-resistant sensor  10  that has high chemical resistance, excellent drip-proof properties, and excellent dust-proof properties can be provided. 
     Method of Manufacturing Low Heat-Resistant Sensor  10   
     A method of manufacturing the low heat-resistant sensor  10  according to the first embodiment of the present invention described above will now be described. 
     As illustrated in  FIG.  7 ( a ) , the housing  22  that includes the recessed portion  24  for the sensor unit  26  and that is composed of fluorine resin is first prepared. 
     Subsequently, as illustrated in  FIG.  7 ( b ) , the adhesive  29  is applied to the bottom portion of the recessed portion  24  of the housing  22 , the sensor unit  26  is disposed in the recessed portion  24  from above, the adhesive  29  is dried, and the sensor unit  26  is firmly secured to the recessed portion  24 . 
     In addition, as illustrated in  FIG.  7 ( c ) , the connection member  50  that is composed of fluorine resin is mounted in the through-hole  25  that is provided in a side portion of the housing  22 . 
     Subsequently, as illustrated in  FIG.  8 ( a )  and  FIG.  9   , the cable  40  is inserted into the through-hole  25  such that the end portion of the cable  40  reaches a location in the recessed portion  24  of the housing  22 . 
     In addition, as illustrated in  FIG.  8 ( b ) , the sensor unit  26  and the cable  40  that is inserted in the through-hole  25  are soldered by using the solder  45 , and the sensor unit  26  and the cable  40  are electrically connected to each other. The plate  28  is disposed above the sensor unit  26  that is disposed in the recessed portion  24  and on the step portion  23  that is provided along the edge of the opening of the recessed portion  24  such that the recessed portion  24  is capped with the plate  28 . 
     Subsequently, as illustrated in  FIG.  8 ( c )  and  FIG.  10   , the frame body  30  composed of fluorine resin is disposed on the step portion  27  that is provided around the plate  28 , and the plate  28  is surrounded by the frame body  30 . At this time, the thickness of the frame body  30  is preferably set such that the frame body  30  protrudes from the plate  28  slightly upward. 
     In addition, as illustrated in  FIG.  11   , a heating and pressing apparatus  61  that presses the frame body  30  is disposed above the housing  22 , and a heating and pressing apparatus  71  that heats and presses the connection member  50  is disposed laterally from the connection member  50 . 
     Subsequently, as illustrated in  FIG.  12   , the heating and pressing apparatus  61  is moved to a location right above the frame body  30  by using a cylinder  80 , and the heating and pressing apparatus  71  is moved to a location right next to the connection member  50  by using a cylinder  82 . 
     As illustrated in  FIG.  13   , the frame body  30  is pressed by the heating and pressing apparatus  61  against the housing  22  by using the cylinder  80  and is heated for a predetermined time, a part of the frame body  30  is melted, the frame body  30  and the housing  22  are integrally formed, and the frame body  30  and the plate  28  are integrally formed. 
     In addition to this, the connection member  50  is pressed by the heating and pressing apparatus  71  against the housing  22  by using the cylinder  82  and is heated for a predetermined time, a part of the connection member  50  is melted, the connection member  50  and the housing  22  are integrally formed, and the connection member  50  and the tube  42  are integrally formed. Reference signs  60  and  62  represent heaters, and reference signs  68  and  70  represent thermocouples. 
     After integral formation, cooling apparatuses  64  and  66  of the heating and pressing apparatuses  61  and  71  are quickly started, and heated portions are cooled. A two-step Peltier element is preferably used as the cooling apparatuses  64  and  66 . 
     After cooling for a predetermined time, the heating and pressing apparatuses  61  and  71  are withdrawn by the cylinders  80  and  82  in directions away from the housing  22 . Consequently, the manufacture of the low heat-resistant sensor  10  illustrated in  FIG.  1    and  FIG.  2    ends. 
     A method of manufacturing the low heat-resistant sensor  10  according to the second embodiment of the present invention described above will now be described. 
     As illustrated in  FIG.  14 ( a ) , the housing  22  that includes the recessed portion  24  for the sensor unit  26 , that is composed of fluorine resin, and that has a cylindrical shape is first prepared. 
     In addition to the housing  22 , the support plate  88  is mounted on the bottom portion of the sensor unit  26  by using the fastener  90 , the engagement projecting portion  85  of the sensor unit  26  is fitted into the engagement recessed portion  84  of the cable  40  by the recess-projection engagement, and the sensor unit  26  and the cable  40  are electrically connected to each other. 
     Subsequently, as illustrated in  FIG.  14 ( b ) , the adhesive  29  is applied to the bottom portion of the recessed portion  24  of the housing  22 . In this state, the sensor unit  26  on which the cable  40  and the support plate  88  are mounted is disposed in the recessed portion  24  of the housing  22 . At this time, the support plate  88  is preferably configured such that the support plate  88  is accurately fitted to the bottom portion of the recessed portion  24 . The cable  40  extends from a location in the recessed portion  24  to a location outside the housing  22  via the through-hole  25 . The adhesive  29  is dried, the sensor unit  26  is firmly secured to the recessed portion  24  with the support plate  88  interposed therebetween. 
     In addition, as illustrated in  FIG.  15 ( a ) , the connection member  50  composed of fluorine resin is mounted in the through-hole  25  that is provided in the side portion of the housing  22 . 
     Subsequently, as illustrated in  FIG.  15 ( b ) , the tube  42  is inserted into the cable  40  such that the end portion of the tube  42  reaches the engagement recessed portion  84  at the end portion of the cable  40  that is located in the through-hole  25 . 
     In addition, as illustrated in  FIG.  16   , the plate  28  is disposed above the sensor unit  26  that is disposed in the recessed portion  24  of the housing  22  and on the step portion  86  that is provided along the edge of the opening of the recessed portion  24  such that the recessed portion  24  is capped with the plate  28 . 
     Subsequently, the frame body  30  composed of fluorine resin is disposed on the step portion  86  that is provided around the plate  28 , and the plate  28  is surrounded by the frame body  30 . At this time, the thickness of the frame body  30  is preferably set such that the frame body  30  protrudes from the plate  28  slightly upward. 
     In addition, the heating and pressing apparatus  61  that presses the frame body  30  is disposed above the housing  22 , and the heating and pressing apparatus  71  that heats and presses the connection member  50  is disposed laterally from the connection member  50 . 
     Subsequently, as illustrated in  FIG.  17   , the heating and pressing apparatus  61  is moved to a location right above the frame body  30  by using the cylinder  80 , and the heating and pressing apparatus  71  is moved to a location right next to the connection member  50  by using the cylinder  82 . 
     As illustrated in  FIG.  18   , the frame body  30  is pressed by the heating and pressing apparatus  61  against the housing  22  by using the cylinder  80  and is heated for a predetermined time, a part of the frame body  30  is melted, the frame body  30  and the housing  22  are integrally formed, and the frame body  30  and the plate  28  are integrally formed. 
     In addition to this, the connection member  50  is pressed by the heating and pressing apparatus  71  against the housing  22  by using the cylinder  82  and is heated for a predetermined time, a part of the connection member  50  is melted, the connection member  50  and the housing  22  are integrally formed, and the connection member  50  and the tube  42  are integrally formed. The reference signs  60  and  62  represent heaters, and the reference signs  68  and  70  represent thermocouples. 
     After integral formation, the cooling apparatuses  64  and  66  of the heating and pressing apparatuses  61  and  71  are quickly started, and heated portions are cooled. A two-step Peltier element is preferably used as the cooling apparatuses  64  and  66 . 
      After cooling for a predetermined time, the heating and pressing apparatuses  61  and  71  are withdrawn by the cylinders  80  and  82  in directions away from the housing  22 . Consequently, the manufacture of the low heat-resistant sensor  10  illustrated in  FIG.  4    and  FIG.  5    ends. 
     The low heat-resistant sensors  10  and the methods of manufacturing the low heat-resistant sensors  10  according to the present invention are described above. However, the structure of each low heat-resistant sensor  10 , that is, the structure of the housing  22  that contains the sensor unit  26  is not particularly limited. 
     According to the present embodiment, MEMS (Micro Electro Mechanical Systems) (the first embodiment) and a pickup (the second embodiment) are used as the sensor unit  26 , but this is not a limitation. For example, a piezoelectric element may be used other than these. 
     Also, the manufacturing methods according to the present invention are not limited by the order described above, but various modifications can be made without departing from the object of the present invention. 
     
       
         
          Reference Signs List
           
               
               
            
               
                 
                   10 
                 
                 low heat-resistant sensor 
               
               
                 
                   20 
                 
                 sensor body 
               
               
                 
                   21 
                 
                 mounting hole 
               
               
                 
                   22 
                 
                 housing 
               
               
                 
                   23 
                 
                 step portion 
               
               
                 
                   24 
                 
                 recessed portion 
               
               
                 
                   25 
                 
                 through hole 
               
               
                 
                   26 
                 
                 sensor unit 
               
               
                 
                   27 
                 
                 step portion 
               
               
                 
                   28 
                 
                 plate 
               
               
                 
                   29 
                 
                 adhesive 
               
               
                 
                   30 
                 
                 frame body 
               
               
                 
                   32 
                 
                 container 
               
               
                 
                   33 
                 
                 flange portion 
               
               
                 
                   40 
                 
                 cable 
               
               
                 
                   41 
                 
                 step portion 
               
               
                 
                   42 
                 
                 tube 
               
               
                 
                   43 
                 
                 step portion 
               
               
                 
                   45 
                 
                 solder 
               
               
                 
                   50 
                 
                 connection member 
               
               
                 
                   51 
                 
                 flange portion 
               
               
                 
                   60 
                 
                 heater 
               
               
                 
                   61 
                 
                 heating and pressing apparatus 
               
               
                 
                   62 
                 
                 heater 
               
               
                 
                   64 
                 
                 cooling apparatus 
               
               
                 
                   66 
                 
                 cooling apparatus 
               
               
                 
                   68 
                 
                 thermocouple 
               
               
                 
                   70 
                 
                 thermocouple 
               
               
                 
                   71 
                 
                 heating and pressing apparatus 
               
               
                 
                   80 
                 
                 cylinder 
               
               
                 
                   82 
                 
                 cylinder 
               
               
                 
                   84 
                 
                 engagement recessed portion 
               
               
                 
                   85 
                 
                 engagement projecting portion 
               
               
                 
                   86 
                 
                 step portion 
               
               
                 
                   88 
                 
                 support plate 
               
               
                 
                   90 
                 
                 fastener