JP2007032878A - Glow plug and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a glow plug and its manufacturing method that can prevent the damage of a flexible member assembled in manufacturing, and reduce manufacturing time and labor. <P>SOLUTION: A tube 200 interposed between an axial hole 43 of a main fitting 40 and a center shaft 30 is compressed within a clearance because a rear end 202 is pressed by an O-ring 70 in a state of a tip part 201 abutting on the rear end face of a cylindrical part 80 in assembling. At this time, since the radial swell and contraction of the tube 200 following deformation is regulated by the clearance, the tube 200 is put in a state of abutting on the inner peripheral surface of the axial hole 43 and the outer peripheral surface of the center shaft 30 over many parts in a direction of an axis O to cause bellows-like deformation. Since the center shaft 30 is put in the form of being supported by the tube 200 in the axial hole 43 of the main fitting 40, even if resonance occurs, its amplitude is effectively limited. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a glow plug for assisting starting of a diesel engine and a method for manufacturing the same.

  Conventionally, glow plugs used to assist in starting diesel engines have a metallic metallic shell made of metal, and project the tip of a rod-shaped heater held at the tip end in the shaft hole. ing. Further, a metal rod-shaped central shaft protrudes from the rear end side of the metal shell, and is held in the shaft hole while being insulated from the metal shell. Both electrodes for energizing the heater are electrically connected to the metal shell and the central shaft, respectively.

  In recent years, diesel engines using glow plugs with such a structure are shifting to direct-injection diesel engines instead of conventional sub-chamber type diesel engines due to demands for smaller size, higher fuel consumption, higher output, etc. . Along with this, the mounting structure to the engine may be changed, and the glow plug is required to have a smaller diameter or a longer length. Further, ceramic heaters with high corrosion resistance are often used for glow plugs.

  By the way, since the natural frequency of the middle shaft decreases because the overall length of the glow plug becomes longer, the frequency of the vibration load generated by the operation of the diesel engine increases the chance of matching the natural frequency of the middle shaft, and resonance occurs. There was a risk that it would occur frequently. If resonance occurs, a portion corresponding to the antinode of the vibration of the central shaft may come into contact with the inner peripheral surface of the metal shell and insulation may not be maintained. Moreover, if the amplitude becomes large, the bending of the central shaft also becomes large, and there is a possibility of breaking. Furthermore, the ceramic heater may be damaged by internal stress transmitted from the center shaft.

Therefore, the intermediate shaft (lead member) is covered with an insulating coating to prevent short circuit between the central shaft and the metallic shell due to resonance, and the outer diameter of the insulating coating is brought close to the inner diameter of the metallic shell, thereby preventing the vibration of the central shaft due to resonance. A glow plug has been proposed in which the amplitude of the above is limited and the generated stress is reduced to prevent breakage of the central shaft (see, for example, Patent Document 1). Thus, if the stress generated by the resonance of the central axis is reduced, the ceramic heater can be prevented from being damaged.
Japanese Patent Laid-Open No. 11-176563

  However, in Patent Document 1, since the insulating coating and the central shaft are in close contact with each other, it is difficult to attach the insulating coating to the central shaft in the manufacturing process of the glow plug, and the insulating coating may be damaged. To prevent this, There is a problem that it is necessary to apply a lubricant such as grease to the central shaft in advance, which is troublesome.

  The present invention has been made to solve the above-described problems, and provides a glow plug and a method for manufacturing the same that can prevent damage to a flexible member that is assembled during manufacturing and can reduce the manufacturing effort. The purpose is to provide.

  In order to achieve the above object, a glow plug according to a first aspect of the present invention includes a central shaft extending along the axial direction, a heater member having a heating element that generates heat when energized, and a shaft hole. A metal shell that holds the radial direction of the heater member, and a tube-like flexible member that is interposed in a gap between the middle shaft and the shaft hole and has flexibility. The flexible member has a thickness smaller than the size of the gap and is compressed in a direction parallel to the axial direction, and comes into contact with each of the middle shaft and the shaft hole by deformation accompanying the compression. In this state, it is interposed in the gap.

  According to a second aspect of the present invention, there is provided a glow plug according to the first aspect of the present invention. And an insulating member that maintains the compressed state of the flexible member by pressing the flexible member in a direction parallel to the axial direction directly or through another member. I have.

  According to a third aspect of the present invention, in addition to the configuration of the second aspect of the invention, the glow plug of the invention is configured such that the outer diameter of the portion of the insulating member that presses the flexible member is that of the flexible member. Of these, the outer diameter of the portion in contact with the insulating member is larger.

  According to a fourth aspect of the present invention, there is provided a method for manufacturing a glow plug according to the second or third aspect, wherein the middle shaft to which the heater member is fixed is used as the shaft of the metal shell. A heater holding step of inserting the hole into the hole and holding the radial direction of the heater member at the tip end side of the shaft hole, and inserting the flexible member into the shaft hole from the rear end side of the shaft hole And an insertion step of inserting the middle shaft into the inner periphery of the flexible member, and the insulating member is disposed on the rear end side of the shaft hole, and the insulating member has a direction parallel to the axial direction. A compression step of compressing the flexible member.

  In the glow plug of the invention according to claim 1, the flexible member interposed in the gap between the shaft hole of the metal shell and the center shaft is compressed in a direction parallel to the axial direction, and the center shaft is deformed by the compression. In this state, the middle shaft is supported by the flexible member in the shaft hole. If the center shaft resonates with the vibration of the engine to which the glow plug is attached, there is a risk that a part of the center shaft that becomes the antinode of vibration will swing greatly due to the resonance. Since the middle shaft is supported, the resonance amplitude can be limited. Thereby, since the bending of the central shaft at the time of the occurrence of resonance is suppressed, it is possible to prevent breakage. In addition, in the structure of the glow plug in which the metal shell and the central shaft are used as electrodes for energizing the heating elements, the shaft hole and the central shaft do not come into contact if the deflection of the central shaft is suppressed, thereby preventing a short circuit. be able to.

  By the way, when the flexible member is disposed in the gap with the central shaft inserted through the shaft hole in the glow plug manufacturing process, the flexible member is in close contact with the inner peripheral surface of the shaft hole or the outer peripheral surface of the central shaft. If an attempt is made to place the gap in the gap in such a state, it cannot be placed smoothly due to friction between the closely contacting surfaces, and the flexible member may be damaged. However, in the present invention, since the thickness of the flexible member is smaller than the size of the gap between the shaft hole and the middle shaft, the flexible member can be easily deformed, and the inner circumferential surface of the shaft hole or the outer circumferential surface of the middle shaft. The flexible member can be easily disposed without being in close contact with the entire circumference. For this reason, the labor in the manufacturing process can be reduced, the breakage of the flexible member can be reduced, and the yield can be increased.

  Further, as in the invention according to claim 2, disposing the insulating member on the rear end side of the shaft hole so that the middle shaft and the shaft hole do not contact each other causes deformation of the flexible member after completion of the glow plug. It is effective in preventing. Further, since the flexible member can be compressed in the direction parallel to the axial direction by the insulating member, the insulating member is disposed on the rear end side after the flexible member is pre-compressed in the glow plug manufacturing process. It is not necessary to use a step process, and labor can be reduced. In addition, since the compressed state of the flexible member can be maintained by the insulating member even after the glow plug is completed, the flexible member may have elasticity as a property, and a material that can be selected as the flexible member is used. The production cost can be reduced.

  Further, when the flexible member is compressed in the process of manufacturing the glow plug, even if the position to be pressed of the flexible member is displaced due to deformation, as in the invention according to claim 3, If the outer diameter of the insulating member is larger than the outer diameter of the flexible member, the position where the flexible member should be pressed is shifted within a range that can be pressed by the insulating member. Can do.

  In the glow plug manufacturing method according to the fourth aspect of the present invention, in the heater holding step, the heater member is held at the tip end side of the shaft hole while the center shaft to which the heater member is fixed is inserted into the shaft hole of the metal shell. In the insertion process, a flexible member is arranged in the gap between the shaft hole and the middle shaft, and in the compression process, an insulating member is arranged on the rear end side of the shaft hole so that the shaft hole and the middle shaft do not contact each other. In addition, the insulating member can compress the flexible member in a direction parallel to the axial direction. In a glow plug manufactured through such a manufacturing process, the flexible member is deformed in the gap between the shaft hole and the center shaft by compression, and the center shaft is supported in the shaft hole. Therefore, the engine to which the glow plug is attached Even when the central axis resonates due to vibration of the vibration, the resonance amplitude can be limited by the flexible member. In addition, since the flexible member is disposed in the gap before the flexible member is compressed, the flexible member is in close contact with the inner peripheral surface of the shaft hole or the outer peripheral surface of the middle shaft. And can be easily arranged. And since a flexible member is compressed when arrange | positioning an insulating member, the process of compressing a flexible member previously can be skipped, and a labor can be reduced.

  Hereinafter, an embodiment of a glow plug embodying the present invention will be described with reference to the drawings. First, the entire structure of the glow plug 100 of the present embodiment will be described with reference to FIG. FIG. 1 is a longitudinal sectional view of the glow plug 100. Note that the side where the ceramic heater 20 is disposed (the lower side in FIG. 1) in the direction of the axis O will be described as the tip side of the glow plug 100.

  A glow plug 100 shown in FIG. 1 is attached to a combustion chamber (not shown) of a direct injection diesel engine, for example, and is used as a heat source for assisting ignition at the time of engine start.

  The ceramic heater 20 has a round bar shape, and a heating element 24 having a substantially U-shaped cross section made of a conductive ceramic is embedded in a base 21 made of an insulating ceramic whose tip 22 is processed into a curved surface. Have. The heating element 24 is disposed at the tip 22 of the ceramic heater 20 and is connected to the heating element 27 whose both ends are folded back in a substantially U shape in accordance with the curved surface thereof, and to both ends of the heating element 27, respectively. And lead portions 28 and 29 extending substantially in parallel along the axis O toward the rear end portion 23. The heating element 27 is shaped so that its cross-sectional area is smaller than the cross-sectional area of the lead portions 28 and 29, and heat is generated mainly in the heating element 27 during energization. Further, on the outer peripheral surface of the rear end portion 23 of the ceramic heater 20, electrode extraction portions 25 and 26 protruding from the lead portions 28 and 29 are exposed at positions shifted from each other in the axis O direction. The ceramic heater 20 corresponds to the “heater member” in the present invention.

  The ceramic heater 20 is held by a cylindrical tubular body 80 so as to surround the outer periphery of the body portion. The electrode extraction portion 25 formed on the distal end side of the electrode extraction portions 25 and 26 is in contact with and electrically connected to the cylindrical body 80 in the cylindrical hole of the cylindrical body 80. The cylindrical body 80 is made of a metal member, and a thick collar portion 82 is formed on the rear end side of the trunk portion 81. A stepped engagement portion 83 is formed at the rear end of the collar portion 82, and the inner periphery of the distal end portion 41 of the cylindrical metal shell 40 is engaged with the engagement portion 83. At the time of the engagement, the axis of the ceramic heater 20 and the axis of the metal shell 40 coincide with the axis O. In this state, the portion of the ceramic heater 20 on the rear end side of the cylindrical body 80 is accommodated in the metal shell 40, and the metal shell 40 is positioned by the engaging portion 83 of the cylindrical body 80. The electrode extraction portion 26 provided at the rear end portion of the heater 20 has a structure that does not contact the metal metal shell 40. The electrode extraction portion 26 is electrically connected to the middle shaft 30 (described later).

  Next, the metal shell 40 is a long and thin cylindrical metal member having a shaft hole 43 penetrating in the direction of the axis O, and a glow plug 100 is attached to an engine head (not shown) on the rear end side of the body portion 44. ) Is formed. Further, a tool engaging portion 46 having a hexagonal cross section in the axial line is formed at the rear end of the body portion 44 and engages with a tool used for attachment to the engine head. Within the tool engagement portion 46, the shaft hole 43 has an enlarged diameter portion 45, and a step portion 47 is formed to connect portions having different diameters.

  The middle shaft 30 is a metal rod extending in the direction of the axis O, and is inserted into the shaft hole 43 of the metal shell 40. The front end portion 31 of the middle shaft 30 is fitted to a connection ring 35 fitted to the rear end portion 23 of the ceramic heater 20 so that the middle shaft 30 and the ceramic heater 20 are integrally connected. The electrode extraction portion 26 of the ceramic heater 20 is in contact with the cylindrical hole inner wall of the connection ring 35, and is electrically connected to the central shaft 30 via the connection ring 35. The metal shell 40 and the middle shaft 30 are electrically insulated with a gap. As will be described later, a tube 200 is interposed in the gap between the two. Each of the metal shell 40 and the central shaft 30 functions as an electrode for applying a voltage to the heating element 27 of the ceramic heater 20.

  An insulating O-ring 70 is engaged with the rear end portion 32 of the middle shaft 30 and is disposed in the stepped portion 47 of the shaft hole 43 of the metal shell 40. Further, an insulating support ring 60 is engaged with the rear end portion 32 and is fitted to the enlarged diameter portion 45, and the front end surface 62 presses the O-ring 70 toward the front end side in the axis O direction. . As a result, the O-ring 70 is brought into contact with the outer peripheral surface of the intermediate shaft 30, the inner peripheral surface of the stepped portion 47 of the shaft hole 43, and the front end surface 62 of the support ring 60, and airtightness inside and outside the shaft hole 43 is maintained. I'm leaning. Further, a flange 61 formed on the rear end side of the support ring 60 is in contact with the rear end of the tool engaging portion 46 and is interposed between the pin terminal 50 and the metal shell 40 so that both of them are interposed. Insulated. The support ring 60 corresponds to the “insulating member” in the present invention.

  Next, the pin terminal 50 is fitted into a portion of the rear end portion 32 of the middle shaft 30 that protrudes from the flange portion 61 of the support ring 60 toward the rear end side. The pin terminal 50 includes a cap-shaped body portion 52 that covers and covers the rear end portion 32 of the intermediate shaft 30, a pin-shaped protrusion portion 53 that protrudes from the body portion 52 toward the rear end side, and a front end side of the body portion 52. It is comprised from the collar part 51 protrudingly provided by radial direction. The pin terminal 50 is fixed to the rear end portion 32 of the middle shaft 30 by crimping the outer periphery of the body portion 52, and the pin terminal 50 and the middle shaft 30 are electrically connected. When the glow plug 100 is attached to the engine head (not shown), a plug cap (not shown) is fitted to the protrusion 53, and power is supplied from an external circuit.

  By the way, the center shaft 30 of the glow plug 100 of the present embodiment having the above-described structure is connected to the ceramic heater 20 whose tip 31 is press-fitted into the cylindrical body 80 joined to the metal shell 40. It is fixed by. On the other hand, the rear end portion 32 is supported by the support ring 60 and the O-ring 70 in the shaft hole 43 (in the enlarged diameter portion 45) at the rear end of the metal shell 40, but is not fixed. Therefore, when the glow plug 100 is attached to the engine head (not shown), the weight of the plug cap fitted to the pin terminal 50 fixed to the rear end portion 32 of the middle shaft 30 and the cord connected to the plug cap Is supported by the middle shaft 30, there is a possibility that the middle shaft 30 may be broken by an impact caused by external vibration such as engine vibration on the middle shaft 30. Therefore, in the present embodiment, the outer diameter of the middle shaft 30 is configured to be 70% or more of the inner diameter of the shaft hole 43 of the metal shell 40. As an example, in the glow plug 100 of the present embodiment, the inner diameter of the shaft hole 43 of the metal shell 40 is configured as Φ5.4, and the outer diameter of the middle shaft 30 is configured as Φ4.0.

  Further, by crimping the pin terminal 50 as described above, the support ring 60 is positioned while being pressed toward the front end side in the direction of the axis O, and the O-ring 70 is further pressed against the support ring 60. Positioned. The tube 200 has the rear end portion 202 pressed by the O-ring 70 in a state where the front end portion 201 is in contact with the rear end surface of the cylindrical body 80, and is compressed in the direction of the axis O. Is placed inside. The tube 200 corresponds to the “flexible member” in the present invention.

  Hereinafter, the detailed configuration of the tube 200 will be described with reference to FIGS. FIG. 2 is a perspective view of the tube 200. FIG. 3 is a cross-sectional view of the tube 200 as viewed from the direction of the arrows along the one-dot chain line PP in FIG. In FIG. 3, in order to show the relationship of the size of the tube 200, the axes of the middle shaft 30 and the metal shell 40 are drawn to be equal.

  A tube 200 shown in FIG. 2 is a cylindrical and flexible member made of insulating silicon. The tube 200 having such a configuration is formed by extrusion and is formed into a continuous tube shape, and is cut to a certain size. At the time of production, the dimensions of each part of the tube 200 are defined as follows. The length B in the axis O direction of the tube 200 is the length between the position where the rear end surface of the cylindrical body 80 is arranged and the position where the O-ring 70 is arranged in the axis O direction after the assembly of the glow plug 100. The extruded tube 200 is cut so as to be slightly longer than the length A (see FIG. 1). Further, as shown in FIG. 3, the outer diameter C of the tube 200 to be molded is smaller than the inner diameter E of the shaft hole 43 of the metal shell 40, and the inner diameter D of the tube 200 is outside the middle shaft 30. The die (not shown) of the extrusion molding machine is selected so as to be larger than the diameter F. That is, the thickness H of the molded tube 200 (radius difference between the outer diameter C and the inner diameter D) is the size G of the gap between the metal shell 40 and the middle shaft 30 (the inner diameter E of the metal shell 40 and the outer diameter of the middle shaft 30). (Radius difference with F).

  The O-ring 70 is disposed in the stepped portion 47 of the shaft hole 43, and the inner diameter J thereof is substantially the same as the outer diameter F of the middle shaft 30, and the outer diameter K is greater than the inner diameter E of the shaft hole 43. The radial thickness I (radial difference between the outer diameter K and the inner diameter J) is larger than the thickness H of the tube 200 and the gap G of the shaft hole 43. In other words, the O-ring 70 has an inner diameter J smaller than the inner diameter D of the tube 200 and an outer diameter K larger than the outer diameter C of the tube 200. The O-ring 70 compresses the tube 200 within the shaft hole 43 and It functions as a lid material that is maintained in a state of being accommodated in the hole 43. That is, the tube 200 is pressed by the support ring 60 indirectly through the O-ring 70.

  In the glow plug 100 having such a structure, a process of inserting the tube 200 into a gap between the shaft hole 43 of the metal shell 40 and the middle shaft 30 inserted through the shaft hole 43 is performed in the manufacturing process. Since the dimensions of each part of the tube 200 are defined so that the inner peripheral surface of the shaft hole 43 and the outer peripheral surface of the central shaft and the tube 200 do not adhere to each other as described above, the insertion is easy. Hereinafter, the manufacturing process of the glow plug 100 will be described with reference to FIGS. FIG. 4 is a diagram showing a schematic flow of the manufacturing process of the glow plug 100. FIG. 5 is a partial cross-sectional view of the glow plug 100 showing the tube compression process of FIG. 4 in more detail.

[Heater formation process]
As shown in FIG. 4, first, an element molded body 251 that is an original shape of the heating element 24 of the ceramic heater 20 is formed by injection molding using a conductive ceramic powder, a binder, or the like as a raw material. On the other hand, the base body molded body 252 which is the original form of the base body 21 is molded into two parts by performing die press molding using an insulating ceramic powder as a raw material and having a concave portion in which the element molded body 251 is accommodated on its mating surface. Form as. Then, the element molded body 251 is sandwiched and accommodated in the recess of the base molded body 252 and subjected to press compression, and then subjected to a baking process such as binder removal processing and hot pressing, and the outer peripheral surface thereof is formed into a hemispherical rod shape. The ceramic heater 20 is formed by polishing and shaping.

[Heater press-fitting process]
Next, the connection ring 35 is formed of a steel material such as stainless steel into a pipe shape and press-fitted into the ceramic heater 20 so as to conduct the electrode extraction portion 26. Similarly, the cylindrical body 80 is also formed into a predetermined shape and press-fitted into the ceramic heater 20 to make the electrode extraction portion 25 conductive. In order to stabilize electrical continuity, plating such as Au or Cu may be performed.

[Center shaft joining process]
The middle shaft 30 is formed from a rod-shaped member of an iron-based material (for example, Fe—Cr—Mo steel) cut to a certain size by plastic working or cutting. Then, the outer periphery is laser welded with the tip 31 of the middle shaft 30 engaged in the connection ring 35 of the heater integrated member 250, and the middle shaft 30 and the heater integrated member 250 are joined together.

[Heater holding process]
Next, the metal shell 40 is formed by forming an iron-based material such as S45C into a cylindrical shape in which the tool engaging portion 46 and the like are formed, and rolling the thread on the male screw portion 42. The middle shaft 30 is inserted into the shaft hole 43 of the metal shell 40. And the inner periphery of the front-end | tip part 41 of the metal shell 40 is engaged with the engaging part 83 of the cylindrical body 80, and the metal shell 40 and the cylindrical body 80 are joined by laser welding. In addition, in order to avoid that the metal shell 40, which is an iron-based material, is rusted, a rust prevention treatment such as plating or painting may be performed after joining the cylindrical body 80.

[Tube insertion process]
Next, insulating silicon is formed into a cylindrical shape by extrusion molding and cut into a predetermined dimension to obtain a tube 200 (see FIG. 2). The tube 200 is inserted into the shaft hole 43 of the metallic shell 40 so that the central shaft 30 is inserted into the inner peripheral side, and is disposed in the gap between the metallic shell 40 and the central shaft 30. As described above with reference to FIG. 3, the outer diameter C of the tube 200 is smaller than the inner diameter E of the shaft hole 43 of the metal shell 40, and the inner diameter D of the tube 200 is larger than the outer diameter F of the middle shaft 30. 40 and the middle shaft 30 are not in close contact with each other and can be easily inserted into the gap between them. At this time, when the distal end portion 201 of the tube 200 abuts against the rear end surface of the cylindrical body 80, the tube 200 does not move further toward the distal end side, so that the axis line is within the gap between the metal shell 40, the middle shaft 30, and the connection ring 35. The tube 200 is positioned in the O direction. The tube insertion step corresponds to the “insertion step” in the present invention.

[Tube compression process]
Thereafter, as shown in FIG. 4, the O-ring 70, the support ring 60 and the pin terminal 50 are engaged with the rear end portion 32 of the middle shaft 30. As shown in FIG. 5, first, the O-ring 70 is engaged with the rear end portion 32 of the middle shaft 30 and is brought into contact with the rear end portion 202 of the tube 200 from the rear end side in the axis O direction. Further, the support ring 60 is engaged with the rear end portion 32 of the middle shaft 30, and the O-ring 70 is pressed toward the front end side in the axis O direction by the front end surface 62, and fitted into the enlarged diameter portion 45 of the shaft hole 43. (Compression process).

  At this time, the tube 200 receives a pressing force toward the distal end side in the axis O direction accompanying the fitting of the support ring 60 through the O-ring 70. On the other hand, the distal end portion 201 of the tube 200 is in contact with the rear end surface (see FIG. 1) of the cylindrical body 80, and the tube 200 sandwiched between the rear end surface of the cylindrical body 80 and the O-ring 70 has an axis O. Compressed in the direction to cause deformation. Since the deformation of the tube 200 is performed in the gap between the metal shell 40 and the central shaft 30, the expansion and contraction of the diameter of the tube 200 accompanying the deformation is restricted. For this reason, the tube 200 abuts against the inner peripheral surface of the shaft hole 43 of the metal shell 40 and the outer peripheral surface of the middle shaft 30 at several locations in the direction of the axis O, resulting in bellows-like deformation. Since the middle shaft 30 is supported by the tube 200 in the shaft hole 43 of the metal shell 40, the amplitude when the middle shaft 30 resonates can be effectively limited.

  Then, the pin terminal 50 is fitted into the rear end portion 32 of the middle shaft 30 (terminal arrangement step), and the outer periphery of the trunk portion 52 is crimped in a state where the support ring 60 is pressed toward the distal end side by the flange portion 51 (caulking). Process). As a result, the pin terminal 50 is fixed to the middle shaft 30 with the support ring 60 and the O-ring 70 positioned, and the glow plug 100 is completed.

  The present invention can be variously modified. For example, although the O-ring 70 is disposed at the position of the step portion 47 of the shaft hole 43, it is not always necessary to be disposed within the shaft hole 43. For example, it is formed in an annular plate shape, and the shaft hole 43 is closed while being in contact with the rear end surface of the tool engaging portion 46 and the outer peripheral surface of the middle shaft 30, and at that time, the rear end portion 202 of the tube 200 is closed. It is good also as a structure which presses in an axis line O direction.

  Moreover, a crease | fold, a groove | channel, etc. may be formed in the tube 200, and the deformation | transformation accompanying compression of the tube 200 may be performed uniformly in the axis line O direction. Similarly, when the tube 200 is formed, the tube 200 may be formed in a bellows shape in advance. Alternatively, the tube 200 may be disposed in the gap between the metal shell 40 and the middle shaft 30 in a state in which the tube 200 is compressed and plastically deformed in advance. In the case of such a configuration, the deformation of the tube 200 itself reduces the contact area of the tube 200 with respect to the metal shell 40 and the middle shaft 30, so that the insertion is easy.

  Further, in this embodiment, the tube 200 made of insulating silicon is described as an example of the flexible member. However, since it is only necessary to limit the amplitude of the central axis when resonating, for example, insulating rubber or soft plastic is used. However, a tube may be manufactured as long as it has heat resistance required for using a glow plug. In the present embodiment, since the tube 200 is maintained in a compressed state by the support ring 60 via the O-ring 70, even if the tube is formed from the elastic member, the deformation of the tube is maintained, and the same effect can be obtained. Further, a conductive tube may be used as long as the middle shaft 30 is covered with an insulating coating or the like.

  Depending on the design dimensions such as the thickness of the tube 200, the thickness of the connection ring 35, and the size of the gap between the metal shell 40 and the central shaft 30, the end surface of the distal end portion 201 of the tube 200 is connected to the connection ring 35 in the tube insertion process. The tube 200 may not be inserted into the gap between the outer peripheral surface of the connection ring 35 and the inner peripheral surface of the shaft hole 43 of the metal shell 40 due to contact with the end surface on the rear end side. Alternatively, due to the thickness of the tube 200, the tip 201 is caught while passing through the gap between the inner peripheral surface of the shaft hole 43 of the metal shell 40 and the outer peripheral surface of the middle shaft 30 and the outer peripheral surface of the connection ring 35, The tip 201 may stop at that position. However, in the tube compression step, the tube 200 that is compressed and deformed between the end surface on the rear end side of the connection ring 35 and the O-ring 70 is the outer peripheral surface of the middle shaft 30 as in the present embodiment. And the position of the end surface of the rear end portion 202 of the deformed tube 200 is located closer to the front end side in the axis O direction than the O-ring 70. This is sufficient, and both the front end 201 and the rear end 202 of the tube 200 may not be maintained in a pressed state.

  However, it is also possible to design the tube 200 so that the end surface of the distal end portion 201 does not come into contact with the end surface on the rear end side of the connection ring 35. For example, as in the glow plug 300 shown in FIG. A flange 338 may be provided in the portion 331 so that when the tube 400 is inserted, the end surface of the distal end portion 401 abuts against the flange 338 so that the insertion depth of the tube 400 is limited.

  Alternatively, the end surface on the rear end side of the connection ring 35 is chamfered, and when the tube 200 is inserted, the distal end portion 201 is connected to the inner peripheral surface of the shaft hole 43 of the metal shell 40 and the outer peripheral surface of the connection ring 35. You may make it guide during. Alternatively, the outer diameter of the intermediate shaft 30 is designed to be substantially the same as the outer diameter of the connection ring 35, and the outer diameter of the portion fitted into the connection ring 35 is reduced to match the inner diameter of the connection ring 35. When looking into the shaft hole 43 from the rear end side in the O direction, the end face on the rear end side of the connection ring 35 is not visible, and the end face of the tip portion 201 of the tube 200, the end face on the rear end side of the connection ring 35, May be prevented.

  Further, in the present embodiment, the ceramic heater 20 is provided as a heater member provided in the glow plug 100, and the manufacturing method thereof is described. However, the manufacturing method is not limited to this, and any known manufacturing method may be used. . Furthermore, the heater member is not limited to the ceramic heater 20, and may be a sheathed heater in which a coil-shaped heating resistor or control resistor is arranged in a metal sheath tube whose tip is closed in a hemispherical shape. That is, the present invention is not limited to the shape of the heater member, and the heat generation specifications of the heater may be set as appropriate.

  The present invention can be used not only for a glow plug having only a heat generation function but also for a glow plug incorporating a temperature sensor, a pressure sensor, or the like.

1 is a longitudinal sectional view of a glow plug 100. FIG. 2 is a perspective view of a tube 200. FIG. It is sectional drawing of the tube 200 seen from the arrow direction in the dashed-dotted line PP of FIG. 3 is a diagram showing a schematic flow of a manufacturing process of the glow plug 100. FIG. It is a fragmentary sectional view of the glow plug 100 which shows the tube compression process of FIG. 4 in detail. It is a longitudinal cross-sectional view of the glow plug 300 as a modification.

Explanation of symbols

20 Ceramic heater 27 Heating element 30 Middle shaft 40 Metal shell 43 Shaft hole 60 Support ring 100 Glow plug 200 Tube

Claims (4)

A central axis extending along the axial direction;
A heater member having a heating element that generates heat when energized;
A metal shell that has a shaft hole, the central shaft is inserted into the shaft hole, and holds the radial direction of the heater member;
A tube-like flexible member that is interposed in a gap between the middle shaft and the shaft hole and has flexibility,
The flexible member has a thickness smaller than the size of the gap and is compressed in a direction parallel to the axial direction, and comes into contact with each of the middle shaft and the shaft hole by deformation accompanying the compression. A glow plug characterized by being interposed in the gap in a state. An insulating member fitted into a gap between the middle shaft and the shaft hole at a rear end portion of the shaft hole;
An insulating member is provided in which the distal end portion of the insulating member presses the flexible member in a direction parallel to the axial direction directly or through another member, and maintains the compressed state of the flexible member. The glow plug according to claim 1.   The outer diameter of a portion of the insulating member that presses the flexible member is larger than an outer diameter of a portion of the flexible member that is in contact with the insulating member. Glow plug. A method for producing a glow plug according to claim 2 or 3,
A heater holding step of inserting the middle shaft to which the heater member is fixed into the shaft hole of the metal shell, and holding a radial direction of the heater member at a tip side of the shaft hole;
An insertion step of inserting the flexible member into the axial hole from the rear end side of the axial hole and inserting the intermediate shaft into the inner periphery of the flexible member;
And a compression step of compressing the flexible member in a direction parallel to the axial direction with the insulating member disposed on the rear end side of the shaft hole. Plug manufacturing method.

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