JP2015078825A - Glow plug and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a glow plug on which an element crack is hardly occurred in a ceramic heater, and which has high reliability, and a method of manufacturing the glow plug.SOLUTION: A glow plug 1 is equipped with a main body fitting 10, a ceramic heater 20 held on a tip end side GS of the main body fitting 10, a rod-shaped metallic axial member 40 inserted in the main body fitting 10 and extending in an axial direction HJ, and a connection member 50 for connecting a heater rear end portion 25 and an axial tip end portion 41. Of the axial member 40, an axial body portion 43 positioned between the axial tip end portion 41 and an axial rear end portion 45 has a plurality of deflection correcting portions 43f for correcting circumferential deflections of a body portion tip end portion 43s based on a body portion rear end portion 43k.

Description

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

  Conventionally, as a glow plug used for assisting starting of a diesel engine, a cylindrical metal shell having a shaft hole, a rod-shaped ceramic heater held on the tip side of the metal shell, and a shaft of the metal shell A rod-like metal shaft member inserted through a hole and a connecting member that connects a heater rear end portion of a ceramic heater and a center shaft tip portion of the center shaft member are known. Such a glow plug is disclosed in, for example, Patent Document 1 (see FIG. 1 of Patent Document 1 and its description).

JP 10-185192 A

  As a form of the middle shaft member of the glow plug, there is one in which the middle shaft body portion is cut so that the outer diameter is narrower than the front end portion of the middle shaft and the rear end portion of the middle shaft. In this medium shaft member, the rigidity of the medium shaft body portion (the bending rigidity in the radial direction perpendicular to the axial direction) can be reduced. For this reason, a glow plug was assembled using an intermediate shaft member that has a large circumferential deflection (hereinafter simply referred to as “the deflection of the intermediate shaft member”) at the front end portion of the central shaft relative to the rear end portion of the central shaft (which is also simply referred to as “runout of the central shaft member”). Even in this case, the bending stress applied to the ceramic heater can be relaxed. That is, since the ceramic heater is held on the front end side of the metal shell and connected to the central shaft member via the connecting member, if the deflection of the central shaft member is large, the bending stress applied to the ceramic heater increases. However, since this bending stress is absorbed by the bending of the middle shaft body portion having low rigidity, the bending stress generated in the ceramic heater can be relaxed.

  On the other hand, when the central shaft body portion of the central shaft member has the same diameter in the entire axial direction, there is an advantage that the central shaft body portion does not need to be cut. However, since the middle shaft member does not have a portion with low rigidity in the middle shaft body portion, the middle shaft body portion is hardly bent as a whole. For this reason, when the glow plug is assembled using the central shaft member having a large runout, the bending stress applied to the ceramic heater increases. In particular, when the central shaft member is processed and formed using a wire material obtained by cutting a coil material, the wire material is often bent originally, and the deflection of the central shaft member tends to increase. Therefore, when a glow plug is assembled using this central shaft member, the bending stress applied to the ceramic heater tends to increase. If the bending stress applied to the ceramic heater is large, the ceramic heater may be cracked.

  The present invention has been made in view of the present situation, and an object of the present invention is to provide a highly reliable glow plug and a method for manufacturing the same, in which an element crack is unlikely to occur in a ceramic heater.

  In one aspect of the present invention for solving the above-described problems, a cylindrical metal shell having a shaft hole, a rod-shaped ceramic heater held on the tip side of the metal shell, and the shaft hole of the metal shell are inserted. A glow plug comprising: a rod-shaped metal middle shaft member extending in the axial direction; and a connecting member connecting a heater rear end portion of the ceramic heater and a middle shaft front end portion of the middle shaft member. Among these, the middle shaft barrel located between the middle shaft tip and the middle shaft rear end is a shake correction that corrects the circumferential runout of the barrel tip with respect to the barrel rear end of the middle shaft barrel. A glow plug having a plurality of parts spaced apart from each other in the axial direction.

  In this glow plug, the middle shaft barrel of the middle shaft member is a shake correction unit that corrects the circumferential runout of the front end of the barrel relative to the rear end of the barrel (hereinafter also referred to simply as “runout of the middle shaft barrel”). Are provided apart from each other in the axial direction. In other words, the middle shaft barrel portion is less susceptible to the deflection of the middle shaft barrel portion than before the deflection correcting portion is provided on the middle shaft barrel portion (the barrel tip portion having the axis of the barrel rear end as a reference axis). The coaxiality of the axis line is reduced). For this reason, even when viewed as a whole of the middle shaft member including the middle shaft tip portion and the middle shaft rear end portion, the deflection of the middle shaft member (circumferential deflection of the middle shaft tip portion with respect to the middle shaft rear end portion) is suppressed ( The coaxiality of the axis at the tip end of the center axis with the axis at the rear end of the center axis as the reference axis is small). Therefore, the glow plug using the middle shaft member can be held at the distal end side of the metal shell, and the bending stress applied to the ceramic heater connected to the middle shaft member via the connection member can be reduced. Therefore, this glow plug has high reliability because it is hard to cause element cracks in the ceramic heater.

  In addition, as the “middle shaft member”, for example, a wire rod obtained by cutting a coil material is used to perform necessary processing on the front end portion of the middle shaft and the rear end portion of the middle shaft, and a vibration correcting portion is formed at a plurality of locations on the middle shaft body portion. Things. Moreover, what formed the shake correction part in the multiple places of the center axis | shaft trunk | drum using the center axis | shaft member formed by cutting is also mentioned.

The “middle shaft body” is a portion located between the front end portion of the middle shaft and the rear end portion of the middle shaft.
The “shake straightening part” is a part of the axial direction of the middle shaft barrel part, so that its own axis line and the axis line of the “non-correcting part (part other than the shake straightening part)” adjacent to itself are obliquely crossed. By connecting the "non-correcting part" adjacent to itself, or by connecting the "non-correcting part" to each other so that the axis of the "non-correcting part" adjacent to itself is obliquely crossed In addition, the central shaft body portion refers to a portion formed so as to reduce the “runout of the central shaft body portion” more than before the “runout correction portion” is formed.

  The “shake correction part” may be formed by plastically deforming a part of the central shaft body in the axial direction in a state where the vibration between the front end of the body and the rear end of the body is limited. As a method of plastically deforming a part of the axial direction of the middle shaft barrel portion, for example, rolling is mentioned. Further, the plastic deformation process such as rolling process may be performed over the entire circumference of a part in the axial direction of the central shaft body, or may be performed at a plurality of locations in the circumferential direction. In addition, when performing plastic deformation processing in a plurality of locations in the circumferential direction, it is preferable to perform the deformation evenly in the circumferential direction.

  As a specific form of the “shake correction part”, for example, a part of the central barrel part in the axial direction is pressed from the radially outer side to the radially inner side to cause plastic deformation with a reduced diameter over the entire circumference. Reduced diameter part. Further, with respect to a part of the axial direction of the middle shaft barrel portion, the entire surface of the twill knurling, the vertical knurling with the convex portion extending along the axial direction, and the convex portion extending in the circumferential direction perpendicular to the axial direction. Rolling knurls formed by plastic deformation by rolling, such as knurls such as horizontal knurls and slant knurls having protrusions extending in the axial direction. In addition, a male screw part in which a male screw is formed by plastic deformation by rolling over the entire circumference of a part in the axial direction of the middle shaft barrel part is also included.

Each “shake correction unit” may have the same axial dimension and cross-sectional shape (cross-sectional shape orthogonal to the axial direction), or may be different from each other.
Further, among the plurality of “non-correcting portions” that are portions other than the shake correcting portion in the central shaft barrel portion, the axial direction dimensions and cross-sectional shapes (cross-sectional shapes orthogonal to the axial direction) are the same. They may be different from each other.

The “center shaft tip portion” is a portion that is located on the tip side of the center shaft body portion and is connected to the connection member, and is preferably configured to be connected to the connection member. For example, when a cylindrical connection ring is used as the connection member, the shape of the tip end portion of the central shaft is a small diameter fitting portion to be fitted into the connection ring, and the fitting portion is connected with a larger diameter than this. There is a form in which a large-diameter portion that is positioned by contacting the connection ring when inserted into the ring is provided.
The “middle shaft rear end” is a portion located on the rear end side of the middle shaft barrel, and may be used as a terminal portion used for connection to the outside, or a terminal member may be attached to the rear end portion of the middle shaft. It may be fitted.

Examples of the “ceramic heater” include a ceramic heater in which a heating resistor made of a conductive ceramic is integrated with a base made of an insulating ceramic. Specific examples include a structure in which a heating resistor made of a conductive ceramic is embedded in a base made of insulating ceramic, or a ceramic heater having a structure in which the heating resistor is exposed to the outside of the base.
The “connecting member” has a cylindrical shape, and is fitted on the rear end of the heater of the ceramic heater at the front end thereof to be connected to the ceramic heater, and is fitted on the front end of the middle shaft member on the rear end side. The form connected to a center shaft member is mentioned.
The “metal fitting” holds the ceramic heater directly or indirectly. For example, the form which hold | maintains a ceramic heater directly with the front-end | tip part of a metal fitting by brazing is mentioned. Moreover, the form which hold | maintains a ceramic heater indirectly with the front-end | tip part of a metal shell through a cylindrical member is mentioned. Specifically, a ceramic heater is inserted into the cylindrical member to connect a part of the ceramic heater and the cylindrical member, and the cylindrical member is press-fitted into the shaft hole of the metallic shell and the cylindrical member and the metallic shell. The form etc. which connect with the front-end | tip part are mentioned.

  Furthermore, in the glow plug described above, the shake correcting portion may be a glow plug that is a reduced diameter portion in which a part of the central shaft body portion in the axial direction is reduced in diameter over the entire circumference.

In this way, by using a reduced diameter portion that is reduced in diameter over the entire circumference, it is possible to correct the bending of the central shaft barrel portion in the entire circumferential direction, so that the deflection of the central shaft barrel portion and further the deflection of the central shaft member can be ensured. Can be suppressed. Therefore, the glow plug using this central shaft member can surely reduce the bending stress applied to the ceramic heater, and element cracks are unlikely to occur in the ceramic heater.
In addition, examples of the “reduced diameter portion” include a form in which a cross section recessed inward in the radial direction forms a rectangular shape (a U shape), a V shape, or a U shape. Moreover, as a method of reducing the diameter to form the reduced diameter portion, for example, a rolling process is exemplified.

  Further, in the glow plug described above, the shake correction portion may be a glow plug that is a rolling knurl portion in which a knurl formed by rolling is formed on a part of the central barrel portion in the axial direction. .

  In this way, the deflection correction part is a rolling knurl part formed by knurls by rolling over the entire circumference, so that the bending of the central axis body part can be corrected in the entire circumferential direction. Can be reliably suppressed. Therefore, the glow plug using this central shaft member can surely reduce the bending stress applied to the ceramic heater, and element cracks are unlikely to occur in the ceramic heater.

  Furthermore, in the glow plug according to any one of the above, the middle shaft barrel portion includes at least one or more shake correction portions on each of a front end side and a rear end side with respect to a center in an axial direction of the center plug body. A plug is good.

  In this way, by providing a shake correction portion on each of the front end side and the rear end side of the middle shaft barrel portion, the shake can be corrected on both the front end side and the rear end side of the middle shaft barrel portion. The deflection of the central shaft member can be effectively suppressed. Therefore, the glow plug using this central shaft member can surely reduce the bending stress applied to the ceramic heater, and element cracks are unlikely to occur in the ceramic heater.

  Further, the glow plug according to any one of the above, wherein each of the shake correction portions has the same axial dimension, and the shake correction portions are formed at equal intervals in the axial direction. A plug is good.

  In this way, by providing the shake correction portions at equal intervals in the axial direction, the shake of the middle shaft barrel portion is corrected by each of the shake correction portions provided at the same size and equal intervals. It is possible to reliably correct the bending of the entire body portion, and to reliably suppress the deflection of the middle shaft barrel portion and further the deflection of the middle shaft member. Therefore, the glow plug using this central shaft member can surely reduce the bending stress applied to the ceramic heater, and element cracks are unlikely to occur in the ceramic heater.

  Furthermore, in the glow plug according to any one of the above, the sum of dimensions in the axial direction of the plurality of shake correction portions is a non-correction that is a portion other than the shake correction portion in the central shaft body portion. The glow plug is preferably made smaller than the sum of the dimensions in the axial direction of the portion.

  If the sum of the dimensions in the axial direction of the plurality of shake correction portions is too large, a large force is required when processing and forming the shake correction portions in the middle shaft barrel portion, which requires a large-sized device and increases costs. For this reason, the glow plug tends to be expensive. On the other hand, in this glow plug, the sum of the dimensions in the axial direction of the shake correcting portion is made smaller than the sum of the dimensions in the axial direction of the non-correcting portion. As a result, the force required to process and form the shake correction portion in the central shaft barrel portion can be reduced, and the cost can be reduced. Therefore, an inexpensive glow plug can be obtained.

  Furthermore, in the glow plug according to any one of the above, the intermediate shaft member is a wire material obtained by cutting a coil material having the same diameter as a non-correcting portion that is a portion other than the shake correcting portion of the central shaft body portion. In addition, it is preferable to use a glow plug formed with the shake correcting portion.

  As described above, the center shaft member processed and formed using the wire material obtained by cutting the coil material is often bent originally, and the deflection of the center shaft body portion and the center shaft member tend to be large. However, in this glow plug, since the plurality of shake correction portions spaced apart from each other in the axial direction are provided in the middle shaft barrel portion of the middle shaft member, the deflection of the middle shaft barrel portion and further the deflection of the middle shaft member can be suppressed. Therefore, this glow plug can appropriately reduce the bending stress applied to the ceramic heater even though the wire material obtained by cutting the coil material is used as the material of the central shaft member, and element cracks are hardly generated in the ceramic heater.

In another aspect, a cylindrical metal shell having a shaft hole, a rod-shaped ceramic heater held on the front end side of the metal shell, and a rod shape that is inserted through the shaft hole of the metal shell and extends in the axial direction. And a connecting member for connecting the heater rear end of the ceramic heater and the center shaft tip of the center shaft member, and of the center shaft member, the center shaft tip and the center shaft rear end of the center shaft member. The middle shaft barrel portion located between the center shaft barrel portions includes a plurality of runout correction portions that are corrected for the circumferential runout at the front end portion of the trunk portion with respect to the rear end portion of the middle shaft barrel portion, spaced apart from each other in the axial direction. A method of manufacturing a glow plug having a wire rod obtained by cutting a coil material having the same diameter as that of a non-correcting portion which is a portion other than the shake correcting portion of the middle shaft barrel portion, and a plurality of the shake correcting portions are used. Multiple ridges arranged in stripes at corresponding intervals The pair of rolling dies are clamped on the middle shaft barrel, and the pair of rolling dies are moved relative to each other in the direction in which the ridges extend to rotate the middle shaft barrel, thereby rotating the ridges. By using a straightening part forming step of forming a plurality of the shake correction parts by reducing a diameter of a part of the middle shaft body part by the press by the above-described method, and the glowing part using the middle shaft member formed with the shake correction parts. And an assembly process for assembling the plug.

  In this glow plug manufacturing method, since the correction part forming step is performed as described above, the center axis body part and the center axis in which the shake is effectively corrected compared with the case where the center part is provided with the shake correction part. The member can be easily and reliably formed. Therefore, when a glow plug is assembled using this central shaft member (assembly process), a high-reliability glow plug can be manufactured in which the bending stress applied to the ceramic heater is small, element cracking is unlikely to occur in the ceramic heater.

1 is a longitudinal sectional view of a glow plug according to Embodiment 1. FIG. It is the longitudinal cross-sectional view which expanded the site | part of the rear-end side among the glow plugs which concern on Embodiment 1. FIG. FIG. 4 is a plan view of a middle shaft member according to the first embodiment. FIG. 4 is a partial enlarged plan view of a central shaft member according to the first embodiment. FIG. 6 is a cross-sectional view (AA cross-sectional view in FIG. 4) of the shake correction portion of the central shaft member according to the first embodiment. It is explanatory drawing which concerns on Embodiment 1 and shows the rolling die used at a correction part formation process. It is explanatory drawing which shows a mode that it concerns on Embodiment 1 and forms a shake correction part with a rolling die in a correction part formation process. FIG. 10 is a partial enlarged plan view of a middle shaft member according to the second embodiment. FIG. 10 is a partial enlarged plan view of a middle shaft member according to the third embodiment. FIG. 10 is a partial enlarged plan view of a middle shaft member according to the fourth embodiment. FIG. 10 is a partial enlarged plan view of a middle shaft member according to the fifth embodiment. It is the longitudinal cross-sectional view which expanded the site | part of the rear end side among the glow plugs which concern on Embodiment 6. FIG. It is a graph which shows runout of a middle axis drum part about an example and a comparative example.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 and 2 show a glow plug 1 according to the first embodiment. 1 and 2, the direction along the axis AX of the glow plug 1 and the axis BX of the central shaft member 40 coaxial with the glow plug 1 is defined as an axial direction HJ, and the side of the axial direction HJ where the ceramic heater 20 is disposed ( The lower side in the figure is the front end side GS, and the opposite side (upper side in the figure) is the rear end side GK.
The glow plug 1 is attached to a fuel chamber (not shown) of a diesel engine, and is used as a heat source for assisting ignition when the engine is started. The glow plug 1 includes a metal shell 10, a ceramic heater 20, an outer cylinder 30, a middle shaft member 40, a connection ring (connection member) 50, a terminal member 60, and the like.

  Of these, the metal shell 10 is a cylindrical metal member (specifically, carbon steel) having a shaft hole 10h penetrating in the axial direction HJ. The metal shell 10 includes a metal fitting front end portion 11, a metal fitting rear end portion 15, and a metal fitting body portion 13 positioned therebetween. Of these, the rear end side GK of the metal shell 13 is provided with an attachment portion 13g formed with a male screw for attaching the glow plug 1 to an engine head (not shown) of the internal combustion engine. Further, the rear end portion 15 of the metal fitting is provided with a tool engaging portion 15c that has a hexagonal cross section and engages a tool when the glow plug 1 is attached to the engine head. As shown in FIG. 2, the opening portion of the shaft hole 10h in the metal rear end portion 15 is a tapered portion 15t that extends in a tapered shape toward the rear end side GK.

  Next, the ceramic heater 20 will be described. The ceramic heater 20 has a round bar shape, and has a shape in which the heater tip 21 is processed into a hemispherical curved surface. The ceramic heater 20 is made of a conductive ceramic (specifically, silicon nitride ceramic containing tungsten carbide as a conductive component) inside an insulating base 26 made of insulating ceramic (specifically, silicon nitride ceramic). The heating resistor 27 is embedded.

  Of these, the heating resistor 27 includes a heating portion 27c, a pair of lead portions 27d and 27e, and a pair of electrode extraction portions 27f and 27g. The heat generating portion 27c is disposed in the heater tip 21 and has a U-shaped bent shape, and generates heat to a high temperature when energized. The pair of lead portions 27 d and 27 e are connected to both ends of the heat generating portion 27 c and extend parallel to each other toward the heater rear end portion 25. The pair of electrode extraction portions 27 f and 27 g are connected to the pair of lead portions 27 d and 27 e at the heater rear end portion 25, and are exposed on the outer peripheral surface of the heater rear end portion 25. One electrode extraction portion 27g is located on the rear end side GK with respect to the other electrode extraction portion 27f.

  Next, the outer cylinder 30 will be described. The outer cylinder 30 is a cylindrical metal member (specifically stainless steel) having a cylindrical hole 30h penetrating in the axial direction HJ. The outer cylinder 30 includes an outer cylinder body portion 31 positioned on the front end side GS, an outer cylinder fitting portion 35 positioned on the rear end side GK, and an outer cylinder flange portion 33 positioned therebetween. Among these, the outer cylinder trunk | drum 31 makes cylindrical shape. Further, the outer cylinder flange part 33 is larger in diameter than the outer cylinder body part 31. Moreover, the outer cylinder fitting part 35 makes the step shape fitted to the metal fitting front-end | tip part 11 of the above-mentioned metal shell 10. FIG.

  This outer cylinder 30 has the ceramic heater 20 in its own cylindrical hole 30h in a state where the heater front end 21 of the ceramic heater 20 protrudes toward the front end GS and the heater rear end 25 protrudes toward the rear end GK. Is inserted from the outside in the radial direction. Accordingly, one electrode extraction portion 27 f of the ceramic heater 20 is in contact with the outer cylinder 30 and is electrically connected to the outer cylinder 30. The outer cylinder fitting portion 35 of the outer cylinder 30 is laser welded to the metal fitting tip 11 while being fitted to the metal fitting tip 11 of the metal shell 10. Thereby, the ceramic heater 20 is held on the front end side GS of the metal shell 10 via the outer cylinder 30.

  Next, the middle shaft member 40 will be described. A central shaft member 40 is shown separately in FIGS. The middle shaft member 40 is inserted into the shaft hole 10h of the metal shell 10 in a state of being insulated from the metal shell 10, and has a round bar shape (the dimension of the axis direction HJ is 100 mm) extending in the axial direction HJ (specifically, Are stainless steel members. As will be described later, the central shaft member 40 is formed by using a coil material having the same diameter as the diameter Dg of the non-correcting portion 43g which is a portion other than the shake correcting portion 43f of the central shaft body portion 43.

  The middle shaft member 40 includes a middle shaft front end portion 41, a middle shaft rear end portion 45, and a middle shaft body portion 43 positioned therebetween. Among these, the middle shaft tip portion 41 is a portion connected to a connection ring 50 described later, and includes a fitting portion 41s having a small diameter and a large diameter portion 41k having a larger diameter. Further, the rear end portion 45 of the middle shaft is a portion into which a terminal member 60 described later is fitted, and a twill knurl 45i (see FIG. 2) is formed on the outer periphery.

  Next, the middle shaft body 43 will be described. The middle shaft body 43 has a vibration correction portion 43f (corrected by correcting a circumferential runout (runout of the middle shaft body 43) of the body front end portion 43s with respect to the body rear end 43k of the middle shaft body 43. 43f1 to 43f10) are formed apart from each other in the axial direction HJ (specifically, 10 pieces). Each shake correcting portion 43f is formed by rolling as described later. These shake correction parts 43f connect themselves and the non-correcting parts 43g adjacent to themselves so that their own axis and the axis of the non-correcting part 43g adjacent to itself cross. By connecting the non-correcting portions 43g to each other so that the axes of the non-correcting portions 43g adjacent to each other are obliquely crossed, the central shaft barrel portion 43 of the central shaft barrel portion 43 is formed more than before the shake correcting portion 43f is formed. It is a part formed so as to reduce vibration.

  Specifically, each shake correcting portion 43f is a reduced diameter portion in which a part of the central shaft body 43 in the axial direction HJ is reduced in diameter over the entire circumference. The reduced diameter portion (vibration correcting portion) 43f has a stepped shape that is recessed in a substantially rectangular shape on the inner side in the longitudinal section. The diameter Dg of the non-correcting portion 43g of the middle shaft body 43 is Dg = 2.700 mm, whereas the diameter Df of the shake correcting portion (reduced diameter portion) 43f is Df = 2.655 mm. Further, each of the shake correction portions 43f has the same dimension Lf in the axial direction HJ (specifically, Lf = 3.5 mm).

  Further, these shake correction portions 43f have a dimension Lg1 in the axial direction HJ of the non-correction portion 43g1 located between the shake correction portions 43f so that the gap between adjacent shake correction portions 43f is 3.5 mm. Lg1 = 3.5 mm) at equal intervals (specifically, an interval of 7.0 mm). Further, these shake correcting portions 43 f are formed in a well-balanced manner over almost the entire axial direction HJ of the central shaft body portion 43. Specifically, one shake correction portion 43f5 is arranged at the center HJC in the axial direction HJ of the middle shaft body portion 43, and four shake correction portions 43f1 to 43f4 are arranged at the front end side GS from this, and the rear end side Five shake correction portions 43f6 to 43f10 are arranged in the GK.

  The dimension Lg2 in the axial direction HJ of the non-correcting portion 43g2 located on the most distal side GS is Lg2 = 10.0 mm. On the other hand, the dimension Lg3 in the axial direction HJ of the non-correcting portion 43g3 located on the most rear end side GK is Lg3 = 3.0 mm. Therefore, the sum Lgt of the dimensions Lg1, Lg2, and Lg3 in the axial direction HJ of the non-correcting portion 43g is Lgt = 3.5 × 9 + 10.0 + 3.0 = 44.5 mm. On the other hand, the sum Lft of the dimensions Lf in the axial direction HJ of the shake correcting portion 43f is Lft = 3.5 × 10 = 35.0 mm. Therefore, the sum Lft of the dimension Lf in the axial direction HJ of the shake correcting portion 43f is smaller than the sum Lgt of the dimensions Lg1, Lg2, and Lg3 in the axial direction HJ of the non-correcting portion 43g (Lft <Lgt).

  Next, the connection ring 50 will be described. As shown in FIG. 1, the connection ring 50 is a cylindrical metal member (specifically stainless steel) that connects the heater rear end 25 of the ceramic heater 20 and the center shaft tip 41 of the center shaft member 40. is there. The connection ring 50 is disposed in the metal shell 10 so as to be separated from the metal ring 10. A heater rear end portion 25 of the ceramic heater 20 is press-fitted into a ring front end portion 51 located on the front end side GS in the connection ring 50. Thereby, the electrode extraction part 27 g of the ceramic heater 20 is in contact with the connection ring 50 and is electrically connected to the connection ring 50.

  On the other hand, the middle shaft front end portion 41 of the middle shaft member 40 is press-fitted into the ring rear end portion 55 located on the rear end side of the connection ring 50. Specifically, the fitting portion 41 s of the middle shaft front end portion 41 is fitted to the ring rear end portion 55, and the large-diameter portion 41 k of the middle shaft front end portion 41 is engaged with the ring rear end portion 55 so that the connection ring 50 Position it. Thus, the ceramic heater 20 and the central shaft member 40 are connected via the connection ring 50.

  Next, the terminal member 60 will be described. The terminal member 60 is a metal member, and includes a surrounding portion 61 located on the front end side GS and a terminal portion 65 located on the rear end side GK. Of these, the surrounding portion 61 has a bottomed cylindrical shape that opens to the front end side GS, is fitted around the middle shaft rear end portion 45 of the middle shaft member 40, and is fixed by crimping to the middle shaft rear end portion 45. As shown in FIG. 2, in the surrounding portion 61, the in-hole surrounding portion 61 s which is a part of the distal end side GS is disposed in the shaft hole 10 h of the metal shell 10. On the other hand, in the surrounding portion 61, the outer hole surrounding portion 61k on the rear end side GK with respect to the in-hole surrounding portion 61s is disposed outside the metal shell 10 (on the rear end side GK with respect to the metal shell 10). Further, a step portion 61 t is formed on the outer periphery of the surrounding portion 61. The terminal portion 65 is a portion that is used as a current-carrying terminal by fitting a plug cap (not shown) when the glow plug 1 is attached to the engine head.

  In the shaft hole 10h of the metal shell 10, there is an O-ring 71 between the metal back end 15 of the metal shell 10 and the in-hole enclosure 61s of the terminal member 60 (cylindrical space) in order from the front end GS. And the insulating spacer 73 is arrange | positioned. Of these, the O-ring 71 is made of an insulating rubber-like elastic body (specifically, fluorine-based rubber). The O-ring 71 seals the shaft hole 10h by sealing hermetically while insulating between the rear end portion 15 of the metal shell 10 and the inner-hole surrounding portion 61s of the terminal member 60.

  On the other hand, the insulating spacer 73 is made of a cylindrical insulator (specifically, nylon). The insulating spacer 73 is positioned on the rear end side GK with respect to the O-ring 71, and reliably separates the rear end portion 15 of the metal shell 10 and the in-hole enclosure portion 61 s of the terminal member 60. To prevent short circuit. In addition, the insulating spacer 73 has a rear end side GK having a diameter larger than that of the front end side GS, and comes into contact with the tapered portion 15t of the metal shell 10 from the rear end side GK, thereby limiting the insertion depth in the axial direction HJ. Has been. On the other hand, the insulating spacer 73 is engaged with the step portion 61t of the terminal member 60, and is biased toward the distal end side GS by the terminal member 60.

  As described above, in the glow plug 1 according to the first embodiment, the middle shaft barrel 43 of the middle shaft member 40 has the shake correction portions 43f that correct the deflection of the middle shaft barrel 43 separated from each other in the axial direction HJ. Have multiple. That is, in the middle shaft barrel portion 43, the deflection of the middle shaft barrel portion 43 is suppressed as compared with the case where the deflection correcting portion 43f is provided in the middle shaft barrel portion 43 (the axis of the barrel rear end portion 43k is defined as the reference axis line). The degree of coaxiality of the axis of the barrel tip 43s is reduced). For this reason, even when viewed as a whole of the middle shaft member 40 including the middle shaft tip portion 41 and the middle shaft rear end portion 45, the deflection of the middle shaft member 40 (circumferential deflection of the middle shaft tip portion 41 with respect to the middle shaft rear end portion 45). Is suppressed (the coaxiality of the axis of the middle shaft tip 41 with the axis of the rear end 45 of the middle shaft as the reference axis is reduced). Therefore, the glow plug 1 using the middle shaft member 40 can be held at the distal end side of the metal shell 10 and can reduce the bending stress applied to the ceramic heater 20 connected to the middle shaft member 40 via the connection ring 50. Therefore, the glow plug 1 has high reliability because it is difficult for element cracks to occur in the ceramic heater 20.

  Further, in the first embodiment, the shake correction portion 43f is a reduced diameter portion in which a part of the central shaft body portion 43 in the axial direction HJ is reduced in diameter over the entire circumference. Since the deflection portion 43f is reduced in diameter over the entire circumference in this way, the bending of the middle shaft barrel portion 43 in the entire circumferential direction can be corrected, so that the deflection of the middle shaft barrel portion 43 and further the middle shaft member 40 can be corrected. Can be reliably suppressed. Therefore, the glow plug 1 using the central shaft member 40 can reliably reduce the bending stress applied to the ceramic heater 20 and hardly cause element cracks in the ceramic heater 20.

  In the first embodiment, the middle shaft body 43 has a plurality of shake correction portions 43f on the front end side GS and the rear end side GK from the center HJC in the axial direction HJ thereof. As described above, by providing the shake correction portions 43f on the front end side GS and the rear end side GK of the middle shaft barrel portion 43, the shake can be corrected on both the front end side GS and the rear end side GK of the middle shaft barrel portion 43. It is possible to effectively suppress the deflection of the body portion 43 and further the deflection of the central shaft member 40.

Further, in the first embodiment, the dimension Lf in the axial direction HJ of each shake correcting portion 43f is made equal, and these shake correcting portions 43f are formed at equal intervals in the axial direction HJ. As described above, by providing the shake correction portions 43f with the same dimension Lf in the axial direction HJ and at equal intervals, the shake correction portions 43f with the same axial dimensions and equal intervals can correct the shake of the central shaft barrel portion 43. Therefore, the bending of the entire middle shaft body 43 can be reliably corrected, and the deflection of the middle shaft body 43 and further the deflection of the middle shaft member 40 can be reliably suppressed.

  In the first embodiment, the sum Lft of the dimension Lf in the axial direction HJ of the plurality of shake correcting portions 43f is made smaller than the sum Lgt of the dimensions Lg1, Lg2, and Lg3 in the axial direction HJ of the non-correcting portion 43g. . For this reason, since the force required to process and form the shake correction portion 43f in the central shaft barrel portion 43 is small, the cost can be reduced. Accordingly, an inexpensive glow plug 1 can be obtained.

  In the first embodiment, as will be described later, the middle shaft member 40 forms a shake correction portion 43f on a wire 40x obtained by cutting a coil material having the same diameter as the diameter Dg of the non-correction portion 43g of the middle shaft barrel portion 43. ing. In the middle shaft member 40 processed and formed using the wire 40x obtained by cutting the coil material, the wire 40x is often originally bent, and the deflection of the middle shaft body 43 and the deflection of the middle shaft member 40 tend to be large. However, in the first embodiment, the middle shaft body 43 of the middle shaft member 40 is provided with a plurality of shake correction portions 43f separated from each other in the axial direction HJ. Shake can be suppressed. Therefore, although the glow plug 1 uses the wire 40x obtained by cutting the coil material as the material of the central shaft member 40, the bending stress applied to the ceramic heater 20 can be appropriately reduced, and the ceramic heater 20 is not cracked. Not likely to occur.

  Next, a method for manufacturing the glow plug 1 will be described. First, manufacture of the center shaft member 40 will be described. First, a coil material having the same diameter as the diameter Dg (= 2.700 mm) of the non-correcting portion 43g of the central shaft body 43 is prepared, and this is cut to obtain a wire rod 40x having a predetermined dimension corresponding to the dimension of the central shaft member 40. obtain. Next, the front end GS of the wire rod 40x (middle shaft member 40) is pressed to form a fitting portion 41s and a large diameter portion 41k at the middle shaft tip portion 41. Further, a knurling process is performed on the rear end side GK of the wire rod 40x (middle shaft member 40) to form a twill knurl 45i on the outer periphery of the middle shaft rear end portion 45.

  Next, in the correction part forming step, a plurality of shake correction parts 43f are formed on the middle shaft body 43 of the wire 40x (middle shaft member 40) (see FIGS. 6 and 7). This correction | amendment part formation process is performed by the rolling process using a pair of rolling die TD1, TD2. As shown in FIG. 6, each rolling die TD1, TD2 includes a plate-shaped portion ta having a rectangular plate shape, and a plurality (specifically, 10 pieces) provided on one main surface of the plate-shaped portion ta. ) Of the ridge tb. The width Wt of each protrusion tb is equal to the dimension Lf in the axial direction HJ of the shake correcting portion 43f (Wt = 3.5 mm). Further, the plurality of ridges tb are arranged in stripes (parallel to each other) at an interval At = 7.0 mm equal to the interval between adjacent shake correction portions 43f.

  As shown in FIG. 7, in performing the correction portion forming step, the tip of the trunk portion of the middle shaft barrel portion 43 of the wire rod 40x in a state in which the wire rod 40x (the middle shaft member 40) can be rotated around the axis BX by the support member SB. The part 43s is supported. Next, the pair of rolling dies TD1 and TD2 are used to clamp the middle shaft body 43 of the wire rod 40x (the middle shaft member 40) (in FIG. 7, the middle shaft body 43 is sandwiched from the left and right directions), while the pair of rolling dies. TD1 and TD2 are relatively moved in directions opposite to each other in a direction in which the ridge tb extends (a direction orthogonal to the paper surface in FIG. 7). Specifically, one (on the right side in FIG. 7) the rolling die TD1 is moved from the front side to the back side, and the other (left side in FIG. 7) rolling die TD2 is moved from the back side to the front side. Move to. As a result, the middle shaft body 43 is rotated about the axis BX. Then, a part of the central shaft body 43 is reduced in diameter over the entire circumference by pressing with the ridge tb, and a plurality of shake correcting portions 43 f are formed in the central shaft body 43. Thus, the central shaft member 40 is created.

  Next, an assembly process for assembling the glow plug 1 will be described. First, the ceramic heater 20 and the connection ring 50 are prepared, and the heater rear end portion 25 of the ceramic heater 20 is press-fitted into the ring front end portion 51 of the connection ring 50. Also, the outer cylinder 30 is prepared, the ceramic heater 20 is press-fitted into the cylindrical hole 30h of the outer cylinder 30, the heater front end portion 21 projects from the outer cylinder 30 to the front end side GS, and the heater rear end portion 25 is It protrudes from the cylinder 30 to the rear end side GK.

Next, the fitting portion 41 s of the middle shaft front end portion 41 of the middle shaft member 40 described above is press-fitted into the ring rear end portion 55 of the connection ring 50, and the large diameter portion 41 k of the middle shaft front end portion 41 is inserted into the ring rear end portion 55. And the connecting ring 50 is positioned. Thereafter, the large-diameter portion 41k of the central shaft member 40 and the ring rear end portion 55 of the connection ring 50 are laser-welded.
Next, the metal shell 10 is prepared, and the central shaft member 40 integrated with the ceramic heater 20 and the like is inserted into the shaft hole 10h of the metal shell 10 from the tip side GS, and the outer cylinder is inserted into the metal tip portion 11 of the metal shell 10. The 30 outer cylinder fitting parts 35 are fitted, and these are laser-welded.

  Next, a terminal member 60, an insulating spacer 73, and an O-ring 71 are prepared, and the insulating spacer 73 is externally fitted into the hole surrounding portion 61 s of the terminal member 60. The ring 71 is fitted. Thereafter, the in-hole surrounding portion 61s of the terminal member 60 is inserted into the shaft hole 10h of the metal shell 10 from the rear end side GK together with the O-ring 71 and the insulating spacer 73. At that time, the middle shaft rear end portion 45 of the middle shaft member 40 is inserted into the surrounding portion 61 of the terminal member 60. Thereafter, the surrounding portion 61 of the terminal member 60 is crimped, and the middle shaft rear end portion 45 is fixed in the surrounding portion 61. Thus, the glow plug 1 is completed.

  As described above, in the method for manufacturing the glow plug 1 according to the first embodiment, since the correction portion forming process is performed as described above, compared to the case before the shake correction portion 43f is provided in the central shaft portion 43. The middle shaft body 43 and the middle shaft member 40 in which the shake is effectively corrected can be easily and reliably formed. Therefore, when the glow plug 1 is assembled using the central shaft member 40 in the assembly process, the bending stress applied to the ceramic heater 20 is small, and the ceramic heater 20 is unlikely to crack and is highly reliable and inexpensive. The plug 1 can be manufactured.

(Embodiments 2 to 5)
Next, second to fifth embodiments will be described (see FIGS. 8 to 11). In the glow plugs 201, 301, 401, and 501 according to the second to fifth embodiments, the forms of the shake correction portions 243f, 343f, 443f, and 543f provided in the central shaft barrel portions 243, 343, 443, and 543 are related to the first embodiment, respectively. It differs from the form of the shake correction part 43f. Other than that, the second embodiment is the same as the first embodiment, and the description of the same parts as the first embodiment is omitted or simplified.

  The middle shaft members 240, 340, 440, and 540 according to the second to fifth embodiments are formed using a coil material having the same diameter as the diameter Dg of the non-correcting portions 243g, 343g, 443g, and 543g, as in the first embodiment. Yes. On the other hand, the shake correction portions 243f, 343f, 443f, and 543f according to the second to fifth embodiments are center shafts positioned between the center shaft front end portions 241, 341, 441, and 541 and the center shaft rear end portions 245, 345, 445 and 545. This is a rolling knurl part in which knurls 243i, 343i, 443i, and 543i are formed by plastic deformation by a rolling process over the entire circumference of a part of the body portions 243, 343, 443, and 543 in the axial direction HJ.

Specifically, the shake correction portion 243f of the second embodiment (see FIG. 8) is a rolled knurl portion in which a twill knurl 243i is formed on the outer periphery.
Further, the shake correction portion 343f of the third embodiment (see FIG. 9) is a rolling knurl portion in which a vertical knurling 343i having a convex portion extending along the axial direction HJ is formed on the outer periphery.
In addition, the shake correction portion 443f of the fourth embodiment (see FIG. 10) is a rolling knurl portion in which a horizontal knurl 443i having a convex portion extending in the circumferential direction orthogonal to the axial direction HJ is formed on the outer periphery.
Further, the shake correction portion 543f of the fifth embodiment (see FIG. 11) is a rolling knurl portion in which oblique knurls 543i having a convex portion extending in the axial direction HJ are formed on the outer periphery.

  Also in the second to fifth embodiments, the shake correction portions 243f, 343f, 234f, 343f, 235f, 343f, 235f, 343f, A plurality of 443f and 543f are formed in the middle shaft barrel portions 243, 343, 443, and 543. For this reason, the middle shaft barrel portions 243, 343, 443, and 543 suppress the shake of the middle shaft barrel portions 243, 343, 443, and 543 as compared to the case before the shake correction portions 243f, 343f, 443f, and 543f are formed. Further, the deflection of the central shaft members 240, 340, 440, and 540 is suppressed. Therefore, the glow plugs 201, 301, 401, and 501 using these middle shaft members 240, 340, 440, and 540 have a small bending stress generated in the ceramic heater 20 and are less likely to cause element cracking in the ceramic heater 20 and have high reliability. high.

  Furthermore, in these Embodiments 2 to 5, the shake correction portions 243f, 343f, 443f, and 543f are rolling knurl portions in which knurls 243i, 343i, 443i, and 543i are formed by rolling over the entire circumference. For this reason, since the bending of the central shaft barrel portions 243, 343, 443, and 543 can be corrected in the entire circumferential direction, the deflection of the central shaft barrel portions 243, 343, 443, and 543 and the deflection of the central shaft members 240, 340, 440, and 540 are further improved. Can be reliably suppressed. Therefore, the glow plugs 201, 301, 401, and 501 can reliably reduce the bending stress generated in the ceramic heater 20, and element cracks are unlikely to occur in the ceramic heater 20. In addition, the same part as Embodiment 1 has the same effect as Embodiment 1. FIG.

(Embodiment 6)
Next, a sixth embodiment will be described (see FIG. 12). The glow plug 601 according to the sixth embodiment is different from the glow plug 1 of the first embodiment in the form of the rear end side GK of the glow plug 601. Other than that, the second embodiment is the same as the first embodiment, and the description of the same parts as the first embodiment is omitted or simplified.

  The glow plug 601 of the sixth embodiment includes the metal shell 10, the ceramic heater 20, the outer cylinder 30, the connection ring 50, and the like similar to those of the first embodiment. On the other hand, the forms of the terminal member 660, the O-ring 671, the insulating spacer 673, and the rear end side GK of the middle shaft member 640 are different from those of the first embodiment. The terminal member 60 of the first embodiment has a part (inner hole surrounding portion 61 s) disposed in the shaft hole 10 h of the metal shell 10, and the other part is outside the metal shell 10 (the rear end of the metal shell 10). Side GK) (see FIG. 2). On the other hand, the terminal member 660 of the sixth embodiment is configured to be entirely disposed outside the metal shell 10 (the rear end side GK from the metal shell 10) (see FIG. 12).

  Specifically, the terminal member 660 includes a terminal flange portion 663 positioned on the front end side GS, a terminal portion 665 positioned on the rear end side GK, and an enclosure portion 661 positioned therebetween. Of these, the terminal flange 663 is a part that abuts against a spacer flange 673k of an insulating spacer 673, which will be described later, and biases the insulating spacer 673 toward the distal end side GS. From the diameter of the shaft hole 10h of the metal shell 10 Is said to be large. Further, the surrounding portion 661 has a bottomed cylindrical shape that opens to the front end side GS, is fitted around the middle shaft rear end portion 645 of the middle shaft member 640, and is fixed by crimping to the middle shaft rear end portion 645. The terminal portion 665 has the same form as the terminal portion 65 of the first embodiment. The middle shaft member 640 of the sixth embodiment is formed of a wire 40x obtained by cutting a coil material having the same diameter as the diameter Dg of the non-correcting portion 643g, as in the first embodiment. The dimension in the axial direction HJ is shorter than the dimension in the axial direction HJ of the middle shaft rear end portion 45 of the first embodiment.

  In the first embodiment, the hole surrounding portion 61s of the terminal member 60 is inserted into the shaft hole 10h of the metal shell 10, and the O-ring 71 and the insulating spacer are interposed between the hole surrounding portion 61s and the metal shell 10. 73 is arranged (see FIG. 2). On the other hand, in the sixth embodiment, an O-ring 671 and an insulating spacer 673 are disposed between the middle shaft member 640 and the metal shell 10 (see FIG. 12).

  Specifically, the O-ring 671 is hermetically sealed while insulating between the rear end 15 of the metal shell 10 and the central shaft member 640. The insulating spacer 673 includes a spacer insertion portion 673s located on the front end side GS and a spacer flange 673k located on the rear end side GK. Among these, the spacer insertion portion 673 s is inserted into the shaft hole 10 h of the metal shell 10 and reliably separates the metal rear end 15 of the metal shell 10 and the middle shaft member 640. Further, the spacer flange 673k is larger in diameter than the shaft hole 10h of the metal shell 10, and is engaged with the metal rear end 15 of the metal shell 10 from the rear end side GK. On the other hand, the spacer flange 673k is in contact with the terminal flange 663 of the terminal member 660 as described above, and is biased toward the distal end GS by the terminal member 660.

  Also in the glow plug 601 of the sixth embodiment, among the middle shaft member 640, the shake correcting portion of the first embodiment is disposed on the middle shaft body portion 643 located between the middle shaft front end portion 641 (see FIG. 1) and the middle shaft rear end portion 645. Similarly to 43f, a plurality of shake correction portions 643f for correcting the circumferential shake of the barrel front end portion 643s with respect to the barrel rear end portion 643k are formed. For this reason, in the middle shaft barrel portion 643, the deflection of the middle shaft barrel portion 643 is suppressed and the deflection of the middle shaft member 640 is further suppressed compared to before the shake correction portion 643f (see also FIG. 1) is formed. . Therefore, the glow plug 601 using the central shaft member 640 has a small bending stress generated in the ceramic heater 20, and it is difficult to cause element cracking in the ceramic heater 20 and is highly reliable. In addition, the same part as Embodiment 1 has the same effect as Embodiment 1. FIG.

(Examples and Comparative Examples)
Next, the results of tests conducted to verify the effects of the present invention will be described. As an example of the present invention, 30 middle shaft members 40 according to Embodiment 1 were prepared. As described above, the middle shaft body 43 of the middle shaft member 40 is formed with a plurality (specifically, ten) of shake correction portions 43f spaced apart from each other in the axial direction HJ.
On the other hand, as a comparative example, in the manufacturing method of the glow plug 1 according to the first embodiment, 30 central shaft members immediately before the correction portion forming step are formed in the central shaft body portion 43 before the shake correcting portion 43f is formed. Prepared.

  Next, for each of the middle shaft members of these examples and comparative examples, the runout of the middle shaft barrel portion (circumferential runout of the barrel tip portion with respect to the barrel rear end portion) was measured. The result is shown in FIG. In FIG. 13, the average value (average value of n = 30) of the deflection of the central barrel portion according to the comparative example is 100% (reference value). And the distribution of the shake value in the center shaft member of the comparative example and the distribution of the shake value in the center shaft member of the example are shown. As is clear from FIG. 13, the center shaft member 40 of the embodiment has a significantly smaller runout (about 20%) of the center shaft body 43 than the center shaft member of the comparative example. It can be seen that the variation is also small. From this result, it can be seen that the shake of the central shaft body 43 has been corrected by forming the plurality of vibration correction portions 43 f in the central shaft body 43.

In the above, the present invention has been described with reference to the embodiments. However, the present invention is not limited to the above-described first to sixth embodiments, and it is needless to say that the present invention can be appropriately modified and applied without departing from the gist thereof. Yes.
For example, in the method for manufacturing the glow plug 1 described in the first embodiment, prior to the correction portion forming step, the tip side GS of the wire 40x obtained by cutting the coil material is processed to fit the fitting portion 41s and the large diameter on the center shaft tip portion 41. While forming the portion 41k and processing the rear end side GK to form the twill knurled 45i on the outer periphery of the central shaft rear end portion 45, this is not restrictive. For example, after performing the correction portion forming step on the wire 40x obtained by cutting the coil material and forming the shake correction portion 43f on the central shaft barrel portion 43, the above processing may be performed on the front end side GS and the rear end side GK. . Further, the number of shake correction portions 43f and the like is not limited to 10 as in the first embodiment, and the length and material of the middle shaft barrel portion 43 are considered in a range in which the deflection of the middle shaft barrel portion 43 can be suppressed. A plurality of them may be formed.

1, 201, 301, 401, 501, 601 Glow plug 10 Metal shell 10h Shaft hole 20 Ceramic heater 25 Heater rear end 40, 240, 340, 440, 540, 640 Middle shaft member 40x Wire 41, 241, 341, 441 541, 641 Middle shaft tip 43, 243, 343, 443, 543, 643 Middle shaft barrel 43s, 243s, 343s, 443s, 543s, 643s Trunk tip 43k, 243k, 343k, 443k, 543k, 643k Part 43f (43f1 to 43f10), 643f shake correction part (reduced diameter part)
243f, 343f, 443f, 543f Runout correction part (rolling knurl part)
243i Ayame knurl 343i Longitudinal knurl 443i Lateral knurl 543i Oblique knurl 43g, 243g, 343g, 443g, 543g, 643g Non-correcting part 45, 245, 345, 445, 545, 645 Middle shaft rear end part 50 Connection ring (connection member)
BX Axis HJ (middle shaft member) Axis direction GS (Axis direction) Tip side GK (Axis direction) Rear end side Df (Smooth correction part) Diameter Dg (Non correction part) Diameter Lf (Spin correction part axis) Dimension Lft (in the axial direction of the shake correction portion) Sum Lg1, Lg2, Lg3 (in the axial direction of the non-correction portion) Lgt (in the axial direction of the non-correction portion) Sum HJC Center TD1, TD2 rolling dies tb ridge At (space between ridges)

Claims (8)

A cylindrical metal shell having a shaft hole;
A rod-shaped ceramic heater held on the tip side of the metal shell;
A metal middle shaft member that is inserted into the shaft hole of the metal shell and extends in the axial direction; and
A glow plug comprising: a connecting member that connects a heater rear end of the ceramic heater and a middle shaft tip of the middle shaft member;
Of the middle shaft member, the middle shaft barrel located between the middle shaft front end and the middle shaft rear end is
A glow plug having a plurality of shake correction portions, each of which is corrected with respect to a circumferential shake at a front end portion of the body portion with respect to a rear end portion of the middle shaft body portion, spaced apart from each other in the axial direction. The glow plug according to claim 1,
The shake correction part is
A glow plug, which is a reduced diameter portion in which a part of the central shaft body portion in the axial direction is reduced in diameter. The glow plug according to claim 1,
The shake correction part is
A glow plug which is a rolling knurl part in which a knurl by rolling is formed on a part of the central shaft body part in the axial direction over the entire circumference. The glow plug according to any one of claims 1 to 3, wherein
The central shaft barrel is
A glow plug having at least one or more shake correction portions on each of a front end side and a rear end side with respect to the center in the axial direction thereof. The glow plug according to any one of claims 1 to 4, wherein
A glow plug formed by equalizing the axial direction dimension of each of the shake correcting portions and forming these shake correcting portions at equal intervals in the axial direction. The glow plug according to any one of claims 1 to 5,
The sum of the dimensions in the axial direction of the plurality of shake correcting portions is made smaller than the sum of the dimensions in the axial direction of the non-correcting portion that is a portion other than the shake correcting portion of the central shaft barrel portion. Glow plug. The glow plug according to any one of claims 1 to 6,
The central shaft member is
A glow plug formed by forming the shake correction portion on a wire obtained by cutting a coil material having the same diameter as that of the non-correction portion, which is a portion other than the shake correction portion, of the central shaft barrel portion. A cylindrical metal shell having a shaft hole;
A rod-shaped ceramic heater held on the tip side of the metal shell;
A metal middle shaft member that is inserted into the shaft hole of the metal shell and extends in the axial direction; and
A connecting member that connects the rear end of the heater of the ceramic heater and the front end of the middle shaft member;
Of the middle shaft member, the middle shaft barrel located between the middle shaft front end and the middle shaft rear end is
A method of manufacturing a glow plug having a plurality of shake correction parts that correct circumferential runout of the front end portion of the trunk portion with respect to the rear end portion of the trunk portion of the middle shaft barrel portion, spaced apart from each other in the axial direction,
A wire material obtained by cutting a coil material having the same diameter as the diameter of the non-correcting portion, which is a portion other than the shake correcting portion, of the central shaft barrel portion is arranged in a stripe shape at intervals corresponding to the plurality of the shake correcting portions. The pair of rolling dies having a plurality of ridges are clamped on the middle shaft barrel, and the pair of rolling dies are moved relative to each other in the direction in which the ridges extend to rotate the middle shaft barrel. And a correction part forming step of forming a plurality of the shake correction parts by reducing the diameter of a part of the central shaft body part over the entire circumference by pressing with the ridges,
An assembly step of assembling the glow plug using the central shaft member on which the shake correcting portion is formed.

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