Patent Publication Number: US-2023156871-A1

Title: Heater

Description:
TECHNICAL FIELD 
     The present disclosure relates to a heater to be used in a combustion gas atmosphere. 
     BACKGROUND OF INVENTION 
     A known technique is described in, for example, Patent Literature 1. 
     CITATION LIST 
     Patent Literature 
     Patent Literature 1: Japanese Unexamined Patent Application Publication No. 2-75187 
     SUMMARY 
     In one or more aspects of the present disclosure, a heater includes a base in a rod shape or a cylindrical shape, a heat element embedded in the base, a cylindrical body including a first end and a second end being open, and a metal fixture including a first hole receiving the cylindrical body. The cylindrical body includes a first cylinder including the first end and a second cylinder including the second end and continuous with the first cylinder. The second cylinder has a smaller outer diameter than the first cylinder. The cylindrical body includes at least one ridge located on an outer circumferential surface of the second cylinder and extending in an axial direction of the second cylinder. The cylindrical body receives the base with an end of the base placed and fixed through the first end being open. An inner circumferential surface of the first hole surrounds the second cylinder. The metal fixture is in contact with the at least one ridge. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The objects, features, and advantages of the present disclosure will become more apparent from the following detailed description and the drawings. 
         FIG.  1    is a sectional view of a heater according to an embodiment of the present disclosure. 
         FIG.  2    is a plan view of the heater according to the embodiment of the present disclosure. 
         FIG.  3    is a plan view of the heater according to the embodiment of the present disclosure. 
         FIG.  4    is an enlarged plan view of a main part of the heater according to a variation of the embodiment of the present disclosure. 
         FIG.  5    is an enlarged plan view of a main part of the heater according to a variation of the embodiment of the present disclosure. 
         FIG.  6    is a plan view of the heater according to a variation of the embodiment of the present disclosure. 
         FIG.  7    is an enlarged plan view of a main part of the heater according to a variation of the embodiment of the present disclosure. 
         FIG.  8    is an enlarged plan view of a main part of the heater according to a variation of the embodiment of the present disclosure. 
         FIG.  9    is an enlarged plan view of a main part of the heater according to a variation of the embodiment of the present disclosure. 
     
    
    
     DESCRIPTION OF EMBODIMENT 
     Various heaters that form the basis of a heater according to one or more embodiments of the present disclosure have been developed, including heaters for ignition devices of combustion equipment and glow plugs of automobile engines. For example, Patent Literature 1 describes a heater including cylindrical body externally fitted around the outer periphery of a base including an embedded heat element, and placed and fixed in a cylindrical housing. 
     In such a heater having the structure that forms the basis of the heater according to one or more embodiments of the present disclosure, the cylindrical body under an external force applied in the axis direction may slip off the housing, lowering the durability and reliability of the heater. 
     The heater according to one or more embodiments of the present disclosure will now be described in detail with reference to the drawings. 
       FIG.  1    is a sectional view of the heater according to an embodiment of the present disclosure.  FIG.  2    is a plan view of the heater according to the embodiment of the present disclosure.  FIG.  3    is a plan view of the heater according to the embodiment of the present disclosure.  FIG.  1    illustrates a cross section of the heater taken in the longitudinal direction of a base.  FIG.  2    is a view of the heater illustrated in  FIG.  1    as viewed in a D 1  direction indicated by an arrow.  FIG.  3    is view of the heater illustrated in  FIG.  1    as viewed in a D 2  direction indicated by an arrow. The D 1  direction (hereafter, simply referred to as a first direction D 1 ) and the D 2  direction (hereafter, simply referred to as a second direction D 2 ) are along the length of the base. In  FIGS.  2  and  3   , components other than a cylindrical body and a metal fixture are not illustrated. 
     A heater  1  according to the present embodiment includes a base  10 , a heat element  20 , a cylindrical body  30 , and a metal fixture  40 . 
     The base  10  is a rod or a cylindrical member with a length in a longitudinal direction and includes one end  10   a  and the other end  10   b.  The base  10  may include, for example, a round rod or a polygonal rod such as a square rod (hereafter also referred to as a plate), or a hexagonal rod. The base  10  may be in the shape of, for example, a cylinder or a polygonal cylinder, such as a square cylinder or a hexagonal cylinder. The base  10  included in the heater  1  according to the present embodiment is a plate, as illustrated in, for example,  FIG.  1   . The base  10  being a plate has, for example, a length of 30 to 60 mm, a width of 4.7 to 9 mm, and a thickness of 1.3 to 6 mm. 
     The base  10  is made of an insulating material. The base  10  is, for example, a sintered body made of an electrically insulating ceramic material. Examples of the ceramic material used for the base  10  include oxide ceramics, nitride ceramics, and carbide ceramics. The ceramic material used for the base  10  may be, for example, alumina ceramics, silicon nitride ceramics, aluminum nitride ceramics, or silicon carbide ceramics. 
     The base  10  made of silicon nitride ceramics has high strength, toughness, insulation, and heat resistance. The base  10  made of silicon nitride ceramics can be obtained with, for example, a method described below. A sintering aid is first mixed with silicon nitride that is a main component of silicon nitride ceramics to prepare a mixture. The sintering aid contains 5 to 15 mass % of rare earth element oxide, such as yttrium oxide, ytterbium oxide, or erbium oxide, 0.5 to 5 mass % of aluminum oxide, and silicon dioxide with a volume in a sintered body adjusted to be 1.5 to 5 mass %. The mixture is formed into a predetermined shape to produce a molded body. The molded body is then hot-pressed and fired at a temperature of 1650 to 1780° C. to obtain the base  10  made of silicon nitride ceramics. 
     The heat element  20  is a wire member that generates heat when energized. The heat element  20  is embedded in the base  10 . The heat element  20  included in the heater  1  according to the present embodiment has a folded shape including a bend as illustrated in, for example,  FIG.  1   . The heat element  20  has, for example, a circular, elliptical, or polygonal cross section. The cross section herein refers to a section perpendicular to the direction in which the heat element  20  extends. 
     The heat element  20  includes one end  20   a  and the other end  20   b.  The end  20   a  and the other end  20   b  are connected to respective two conductor layers  11  on the surface of the end  10   a  of the base  10  as illustrated in, for example,  FIG.  1   . The two conductor layers  11  serve as the electrodes of the heater  1 . Two lead terminals  21  for electrical connection with an external power supply are connected to the respective two conductor layers  11 . The conductor layer  11  is made of a metal material such as silver or copper. The conductor layer  11  can be formed by, for example, screen printing. The conductor layer  11  has, for example, a rectangular surface opposite to its surface facing the base  10 . The conductor layer  11  has, for example, a length of 5 mm in the longitudinal direction of the base  10  (hereafter, simply referred to as the longitudinal direction), a width of 6 mm, and a thickness of 100 μm. 
     The heat element  20  has, for example, a total length of 40 to 250 mm, and has a cross-sectional area of 0.0001 to 2 mm 2 . The heat element  20  can contain, as a main component, a carbide such as tungsten, molybdenum, and titanium, a nitride, or a silicide. 
     When the base  10  is made of silicon nitride ceramics, the heat element  20  may be made of tungsten carbide. This allows the coefficient of thermal expansion of the base  10  to be approximated to that of the heat element  20 , thus avoiding disconnection of the heat element  20  under heat cycling. 
     When the base  10  is made of silicon nitride ceramics, the heat element  20  may contain tungsten carbide as a main component and may contain 20 mass % or greater of silicon nitride. This allows the coefficient of thermal expansion of the base  10  to be approximated to that of the heat element  20 . This structure reduces thermal stress caused by the thermal expansion difference between the base  10  and the heat element  20  when the heater  1  is heated or cooled. 
     Each lead terminal  21  includes one end and the other end. One end of the lead terminal  21  is joined to the end  10   a  of the base  10  with the conductor layer  11 , thus electrically connecting the lead terminal  21  to the heat element  20 . The other end of the lead terminal  21  is connected to an external power supply. The lead terminal  21  and the conductor layer  11  may be joined with, for example, a brazing material. Examples of the brazing material include silver solder, gold-copper solder, and silver-copper solder. The lead terminal  21  is made of, for example, nickel. A portion of the lead terminal  21  other than its portions connected to the conductor layer  11  and to the external power supply may be covered with an insulating tube. This can reduce contact between the two lead terminals  21 . The tube may be made of, for example, a resin material with high heat resistance, such as a fluororesin. 
     The cylindrical body  30  protects the base  10  and the lead terminals  21 . The cylindrical body  30  may be in the shape of a cylinder, or for example, a polygonal cylinder, such as a square cylinder or a hexagonal cylinder. The cylindrical body  30  included in the heater  1  according to the present embodiment is cylindrical. The cylindrical body  30  has a first end  30   a  and a second end  30   b  being open. The end  10   a  of the base  10  is placed through the opening at the first end  30   a  and is fixed. 
     The cylindrical body  30  includes a first cylinder  31  having the first end  30   a  and a second cylinder  32  having the second end  30   b.  The second cylinder  32  is continuous with the first cylinder  31 . The second cylinder  32  has a smaller outer diameter than the first cylinder  31 . 
     The first cylinder  31  and the second cylinder  32  in the heater  1  according to the present embodiment are cylindrical. The first cylinder  31  has an axis aligned with an axis of the second cylinder  32 . The axial direction of the first cylinder  31  and the axial direction of the second cylinder  32  are along the length of the base  10 . 
     As illustrated in, for example,  FIG.  3   , the opening at the first end  30   a  of the cylindrical body  30  may be shaped to substantially match the planar shape of the base  10  as viewed in the second direction D 2 . This allows the cylindrical body  30  to tightly hold the base  10 . 
     An adhesive  50  is filled between the base  10  and an inner circumferential surface  30   c  of the cylindrical body  30  to fix the base  10  and the cylindrical body  30  to each other. The adhesive  50  may cover the joints between the base  10  and the lead terminals  21 . This improves the reliability of the electrical connection between the heater  1  and the external power supply. This thus improves the durability and reliability of the heater  1 . The adhesive  50  may fill the entire space defined by the inner circumferential surface  30   c  of the cylindrical body  30 . 
     The opening at the first end  30   a  may include a cutout from the center of the opening  31   b  as illustrated in, for example,  FIG.  3   . This allows the adhesive  50  to be filled between the surface of the base  10  and the inner circumferential surface  30   c  of the cylindrical body  30  through the cutout after the end  10   a  of the base  10  is placed through the opening in manufacturing the heater  1 . This reduces damage to the joints between the base  10  and the lead terminals  21  in the process of filling the adhesive  50 . 
     The cylindrical body  30  includes at least one ridge  33  on an outer circumferential surface  32   a  of the second cylinder  32  as illustrated in, for example,  FIGS.  1  and  2   . The ridge  33  extends in the longitudinal direction. The at least one ridge  33  may include an arc-shaped tip surface  33   a  opposite to its surface in contact with the outer circumferential surface  32   a  of the second cylinder  32  as viewed in a section perpendicular to the longitudinal direction. Although  FIGS.  1  and  2    illustrate one ridge  33  on the outer circumferential surface  32   a  of the second cylinder  32 , the at least one ridge  33  may be multiple ridges  33 . 
     The metal fixture  40  holds the cylindrical body  30  to facilitate mounting of the cylindrical body  30  on an external device. The metal fixture  40  is fixed to the external device. Examples of the external device include a heating device and a gas range. The metal fixture  40  has a flange shape. The metal fixture  40  is made of a metal material such as stainless steel or an iron-nickel-cobalt alloy. 
     The metal fixture  40  includes a cylindrical part  41  and a plate member  42 . The cylindrical part  41  includes a first hole  43  extending through the cylindrical part  41  in its axial direction. The axial direction of the cylindrical part  41  is along the length of the base  10 . The plate member  42  includes a second hole  44  extending through the plate member  42  in its thickness direction. The second hole  44  includes an inner circumferential surface  44   a  connected to an outer circumferential surface  41   a  of the cylindrical part  41 . The cylindrical part  41  and the plate member  42  may be integral with each other or separate members. 
     The cylindrical body  30  is placed in the first hole  43  of the metal fixture  40 . Without the cylindrical body  30  being placed in the metal fixture  40 , the inner diameter of the first hole  43  of the metal fixture  40  is substantially equal to the diameter of an imaginary circle C (refer to  FIG.  2   ) circumscribed by the second cylinder  32  including the ridge  33 . In this state, the inner diameter of the first hole  43  may be, for example, 100% of the diameter of the imaginary circle C, or may be greater than or equal to 70% and less than 100% of the diameter of the imaginary circle C. With the cylindrical body  30  placed in the first hole  43  of the metal fixture  40 , a portion of the metal fixture  40  adjacent to the inner circumferential surface  43   a  can deform elastically toward the cylindrical body  30  as illustrated in, for example,  FIG.  2   . 
     The inner circumferential surface  43   a  of the first hole  43  in the metal fixture  40  surrounds the outer circumferential surface  32   a  of the second cylinder  32  and is in contact with the ridge  33 . In other words, in the cylindrical body  30 , the second cylinder  32  including the ridge  33  is press-fitted in the first hole  43 , and the tip surface  33   a  of the ridge  33  and a contact area  32   b  of the outer circumferential surface  32   a  of the second cylinder  32  is in contact with the inner circumferential surface  43   a  of the first hole  43  as illustrated in, for example,  FIG.  2   . The cylindrical body  30  is held in the metal fixture  40  under a frictional force generated between the tip surface  33   a  and the inner circumferential surface  43   a  and a frictional force generated between the contact area  32   b  and the inner circumferential surface  43   a.    
     The contact area  32   b  herein refers to a partial area of the outer circumferential surface  32   a  of the second cylinder  32  that is in contact with the inner circumferential surface  43   a  of the first hole  43  when the cylindrical body  30  is press-fitted in the first hole  43 . For the structure with one ridge  33  on the outer circumferential surface  32   a  of the second cylinder  32 , the contact area  32   b  may be at a position opposite to the ridge  33  in the radial direction of the second cylinder  32  as illustrated in, for example,  FIG.  2   . For the structure with multiple ridges  33  on the outer circumferential surface  32   a  of the second cylinder  32 , one or more contact areas  32   b  may be defined or no contact area  32   b  may be defined. 
     As illustrated in, for example,  FIG.  2   , the metal fixture  40  includes a portion  45  (hereafter, also referred to as a contact portion) that is located inward from an outer circumferential surface  31   a  of the first cylinder  31  when the cylindrical body  30  is press-fitted in the first hole  43 . The contact portion  45  has a smaller height from the outer circumferential surface  32   a  of the second cylinder  32  than from the outer circumferential surface  31   a  of the first cylinder  31  and overlaps the first cylinder  31  as viewed in the first direction D 1 . Although the cylindrical body  30  moves relative to the metal fixture  40  in the second direction D 2  under an external force in the second direction D 2  applied to the cylindrical body  30 , the first cylinder  31  included in the cylindrical body  30  comes in contact with the contact portion  45  and is thus restricted from moving further in the second direction D 2 . As described above, the heater  1  according to the present embodiment includes the cylindrical body  30  that avoids slipping off the metal fixture  40  under an external force applied in the second direction D 2 . The heater  1  can thus have improved durability and reliability. 
     In the heater  1  according to the present embodiment, a clearance G is left between the outer circumferential surface  32   a  of the second cylinder  32  and the inner circumferential surface  43   a  of the first hole  43  due to the ridge  33  on the outer circumferential surface  32   a  of the second cylinder  32 . This allows the metal fixture  40  to thermally expand toward the clearance G under heat cycling, thus reducing thermal stress applied from the metal fixture  40  to the cylindrical body  30 . As a result, the cylindrical body  30  is less likely to crack. This thus improves the durability and reliability of the heater  1 . 
     In the heater  1  according to the present embodiment as illustrated in, for example,  FIG.  1   , the tip surface  33   a  of the ridge  33  and the outer circumferential surface  31   a  of the first cylinder  31  are at the same height from the outer circumferential surface  32   a  of the second cylinder  32 . The tip surface  33   a  and the outer circumferential surface  31   a  are flush with each other, thus improving the mechanical strength of the ridge  33 . This thus improves the durability and reliability of the heater  1 . 
     In the heater  1  according to the present embodiment as illustrated in, for example,  FIG.  1   , the inner circumferential surface  44   a  of the plate member  42  is connected to an end of the outer circumferential surface  41   a  of the cylindrical part  41  facing the first end  30   a  of the cylindrical body  30 . In this case, the metal fixture  40  has its portion adjacent to the first cylinder  31  with improved mechanical strength, and can effectively regulate the relative movement of the cylindrical body  30  in the second direction D 2 . The cylindrical body  30  can effectively avoid slipping off the metal fixture  40  under an external force applied in the second direction D 2 . The heater  1  can thus have improved durability and reliability. 
     Although  FIG.  1    illustrates the first cylinder  31  and the metal fixture  40  being separate in the longitudinal direction, the first cylinder  31  and the metal fixture  40  may be in contact with each other. This reduces cracks in the cylindrical body  30  that may occur when the cylindrical body  30  moves rapidly relative to the metal fixture  40  in the second direction D 2  with a large impact acting on the cylindrical body  30  in the second direction D 2  and collides with the metal fixture  40 . This thus improves the durability and reliability of the heater  1 . 
     As illustrated in, for example,  FIG.  1   , the metal fixture  40  may overlap the joints between the base  10  and the lead terminals  21  as viewed in the radial direction of the cylindrical body  30 . This allows heat generated in the heat element  20  and transferred to the joints between the base  10  and the lead terminals  21  to be dissipated outside through the metal fixture  40 , thus avoiding excess heating of the joints between the base  10  and the lead terminals  21 . This improves the reliability of the electrical connection between the heater  1  and the external power supply. This thus improves the durability and reliability of the heater  1 . 
     The heater  1  according to variations of the present embodiment will now be described with reference to  FIGS.  4  to  9   . 
       FIG.  4    is an enlarged plan view of a main part of the heater according to a variation of the embodiment of the present disclosure.  FIG.  5    is an enlarged plan view of a main part of the heater according to a variation of the embodiment of the present disclosure.  FIG.  6    is a plan view of the heater according to a variation of the embodiment of the present disclosure.  FIG.  7    is an enlarged plan view of a main part of the heater according to a variation of the embodiment of the present disclosure.  FIG.  8    is an enlarged plan view of a main part of the heater according to a variation of the embodiment of the present disclosure.  FIG.  9    is an enlarged plan view of a main part of the heater according to a variation of the embodiment of the present disclosure.  FIGS.  4 ,  5   , and  7  to  9  each are an enlarged view of a portion near the ridge in the heater.  FIG.  6    corresponds to the plan view of  FIG.  2   . 
     As illustrated in, for example,  FIG.  4   , the tip surface  33   a  of the ridge  33  may be at a lower height from the outer circumferential surface  32   a  of the second cylinder  32  than the outer circumferential surface  31   a  of the first cylinder  31 . As a result, the entire portion of the metal fixture  40  near the inner circumferential surface  43   a  serves as the contact portion  45 . In this structure, the cylindrical body  30  can effectively avoid slipping off the metal fixture  40  under an external force applied in the second direction D 2 . This thus improves the durability and reliability of the heater  1 . 
     For a certain number of ridges  33  or for a ridge  33  at a certain position, the ridge(s)  33  may be at a greater height from the outer circumferential surface  32   a  of the second cylinder  32  than from the outer circumferential surface  31   a  of the first cylinder  31 . As illustrated in, for example,  FIG.  2   , when a single elongated ridge  33  is on the second cylinder  32 , the metal fixture  40  can include the contact portion  45  for any height of the ridge  33 . The cylindrical body  30  can avoid slipping off the metal fixture  40  under an external force applied in the second direction D 2 . 
     As illustrated in, for example,  FIG.  5   , at least one ridge  33  may have a gradually decreasing height from the outer circumferential surface  32   a  of the second cylinder  32  toward the second end  30   b  of the cylindrical body  30 . The contact area between the tip surface  33   a  and the inner circumferential surface  43   a  is larger as compared with when the height of the ridge  33  from the outer circumferential surface  32   a  is constant. The cylindrical body  30  can be firmly fixed to the metal fixture  40 . In manufacturing the heater  1 , for example, the second end  30   b  of the cylindrical body  30  can be easily press-fitted into the first hole  43 . The press-fitting can be stopped at the position of the cylindrical body  30  firmly fixed to the metal fixture  40 , thus with no excess stress being applied to the cylindrical body  30 . The cylindrical body  30  and the metal fixture  40  can thus be fixed firmly while reducing cracks in the cylindrical body  30 . 
     As illustrated in, for example,  FIG.  6   , at least one ridge  33  may be multiple ridges  33 . The multiple ridges  33  may be located on the outer circumferential surface  32   a  of the second cylinder  32  and may be spaced from one another in the circumferential direction of the second cylinder  32 . Although  FIG.  6    illustrates four ridges  33  on the outer circumferential surface  32   a,  two, three, or five or more ridges  33  may be located on the outer circumferential surface  32   a.    
     Such multiple ridges  33  on the outer circumferential surface  32   a  of the second cylinder  32  have their tip surfaces  33   a  in contact with the inner circumferential surface  43   a  of the first hole  43 . This increases a frictional force between the cylindrical body  30  and the metal fixture  40 , allowing the metal fixture  40  to hold the cylindrical body  30  firmly. This improves the durability and reliability of the heater  1 . The structure including the multiple ridges  33  on the outer circumferential surface  32   a  as illustrated in, for example,  FIG.  6    may eliminate the contact area  32   b  on the outer circumferential surface  32   a  of the second cylinder  32 . 
     For the multiple ridges  33  on the outer circumferential surface  32   a,  the metal fixture  40  can include multiple contact portions  45  when the cylindrical body  30  is press-fitted in the first hole  43 , as illustrated in, for example,  FIG.  6   . This allows the metal fixture  40  to effectively regulate the relative movement of the cylindrical body  30  in the second direction D 2 . The cylindrical body  30  can thus effectively avoid slipping off the metal fixture  40  under an external force applied in the second direction D 2 . 
     As illustrated in, for example,  FIG.  6   , the multiple ridges  33  may be at equal intervals in the circumferential direction of the second cylinder  32 . With the cylindrical body  30  coming in contact with the metal fixture  40  under an external force applied in the second direction D 2 , the resultant force on the cylindrical body  30  is applied by the multiple contact portions  45  in the direction substantially aligned with the axial direction of the cylindrical body  30 . This can reduce bending moment in the cylindrical body  30 . This can reduce breakage of the cylindrical body  30 . The heater  1  can thus have improved durability and reliability. 
     As illustrated in, for example,  FIG.  7   , at least one ridge  33  may include a protrusion  33   b  having a greater height from the outer circumferential surface  32   a  of the second cylinder  32  than the outer circumferential surface  31   a  of the first cylinder  31 . With the protrusion  33   b  coming in contact with the metal fixture  40  under an external force in the second direction D 2  applied to the cylindrical body  30 , the metal fixture  40  effectively avoids moving relative to the cylindrical body  30  in the first direction D 1 . With the metal fixture  40  moving over the protrusion  33   b  and moving relatively in the first direction D 1  and the contact portion  45  coming in contact with the first cylinder  31 , the metal fixture  40  can avoid moving relative to the cylindrical body  30  in the first direction D 1 . With the ridge  33  including the protrusion  33   b,  the cylindrical body  30  can effectively avoid slipping off the metal fixture  40  under an external force applied in the second direction D 2 . This thus improves the durability and reliability of the heater  1 . 
     For the ridge  33  extending across the entire second cylinder  32  in the longitudinal direction, the protrusion  33   b  may be located at an end of the ridge  33  facing the first cylinder  31  and may be adjacent to the first cylinder  31  as illustrated in, for example,  FIG.  7   . This improves the mechanical strength of the protrusion  33   b  and reduces cracks in the protrusion  33   b  when the protrusion  33   b  comes in contact with the metal fixture  40 . This thus improves the durability and reliability of the heater  1 . 
     At least one ridge  33  may include a cutout  33   c  in the outer surface in the radial direction of the second cylinder  32 . In this case, when the cylindrical body  30  moves relative to the metal fixture  40  in the second direction D 2  under an external force in the second direction D 2  applied to the cylindrical body  30 , the metal fixture  40  can be caught in the cutout  33   c  with its elastic restoring force as illustrated in, for example,  FIG.  8   . Under an external force in the second direction D 2  applied to the cylindrical body  30 , the metal fixture  40  has its portion caught in the cutout  33   c  in contact with the inner circumferential surface of the cutout  33   c  and is thus restricted from moving relative to the cylindrical body  30  in the first direction D 1 . With the contact portion  45  coming in contact with the first cylinder  31  when the metal fixture  40  relatively moves in the first direction D 1  by moving over the cutout  33   c,  the metal fixture  40  can avoid moving relative to the cylindrical body  30  in the first direction D 1 . Under an external force in the first direction D 1  applied to the cylindrical body  30 , the metal fixture  40  has its portion caught in the cutout  33   c  in contact with the inner circumferential surface of the cutout  33   c  and is thus restricted from moving relative to the cylindrical body  30  in the second direction D 2 . The cylindrical body  30  can effectively avoid slipping off the metal fixture  40  under an external force applied in the first direction D 1  or in the second direction D 2  when the ridge  33  includes the cutout  33   c.  This thus improves the durability and reliability of the heater  1 . 
     The metal fixture  40  may be placed in the cutout  33   c  when the heater  1  is manufactured or when the heater  1  is mounted in an external device. 
     As illustrated in, for example,  FIG.  9   , in the metal fixture  40 , the inner circumferential surface  44   a  of the second hole  44  in the plate member  42  may be connected to an end of the outer circumferential surface  41   a  of the cylindrical part  41  facing the second end. This allows the plate member  42  to be apart from the heat element  20 , thus avoiding heat generated by the heat element  20  dissipated more than intended outside through the plate member  42 . This can improve the heating efficiency of the heater  1 . 
     The present disclosure may be implemented in the following forms. 
     In one or more embodiments of the present disclosure, a heater includes a base in a rod shape or a cylindrical shape, a heat element embedded in the base, a cylindrical body including a first end and a second end being open, and a metal fixture including a first hole receiving the cylindrical body. The cylindrical body includes a first cylinder including the first end and a second cylinder including the second end and continuous with the first cylinder. The second cylinder has a smaller outer diameter than the first cylinder. The cylindrical body includes at least one ridge located on an outer circumferential surface of the second cylinder and extending in an axial direction of the second cylinder. The cylindrical body receives the base with an end of the base placed and fixed through the first end being open. An inner circumferential surface of the first hole surrounds the second cylinder. The metal fixture is in contact with the at least one ridge. 
     The heater according to one or more embodiments of the present disclosure can have improved durability and reliability. 
     Although the embodiment of the present disclosure has been described in detail, the present disclosure is not limited to the embodiment described above, and may be changed or modified in various manners without departing from the spirit and scope of the present disclosure. The components described in the above embodiment may be entirely or partially combined as appropriate unless any contradiction arises. 
     REFERENCE SIGNS 
       1  heater 
       10  base 
       10   a  one end 
       10   b  the other end 
       11  conductor layer 
       20  heat element 
       20   a  one end 
       20   b  the other end 
       21  lead terminal 
       30  cylindrical body 
       30   a  first end 
       30   b  second end 
       30   c  inner circumferential surface 
       31  first cylinder 
       31   a  outer circumferential surface 
       31   b  opening 
       32  second cylinder 
       32   a  outer circumferential surface 
       32   b  contact area 
       33  ridge 
       33   a  tip surface 
       33   b  protrusion 
       33   c  cutout 
       40  metal fixture 
       41  cylindrical part 
       41   a  outer circumferential surface 
       42  plate member 
       43  first hole 
       43   a  inner circumferential surface 
       44  second hole 
       44   a  inner circumferential surface 
       45  contact portion 
       50  adhesive