JP6401022B2 - Glow plug and manufacturing method thereof - Google Patents

Description

  The present invention relates to a glow plug and a method for manufacturing the same.

  As a glow plug structure, a structure in which a heater element is connected to a central shaft provided in a shaft hole of a metal shell via a cylindrical ring is known (see Patent Document 1). In such a glow plug, the heater element is press-fitted on the front end side of the ring, and the center shaft is press-fitted on the rear end side of the ring.

JP 2014-119193 A

  In the glow plug of Patent Document 1, there has been a problem that sufficient consideration has not been given to suppressing the shaft runout in which the center axis is deviated from the axis of the ring. For example, in the middle shaft, when a corner R whose diameter gradually increases toward the rear end side is formed at the corner on the rear end side of the press-fitted portion that is press-fitted into the ring, the ring fits into the corner R in an inclined state. There is a risk that shaft runout may occur due to the rotation. Further, out of the portions of the members of the ring and the central shaft, the shaft runout may occur even when the contact surface that contacts the other member by press fitting does not have sufficient flatness. The shaft runout of the middle shaft with respect to the ring exerts an excessive stress on the heater element in a state where it is assembled as a glow plug, which causes damage to the heater element.

  The present invention has been made to solve the above-described problems, and can be realized as the following forms.

(1) According to one aspect of the present invention, a heater element that generates heat when energized; a middle shaft that extends in the axial direction from the front end side to the rear end side; and a cylindrical shape that connects the heater element to the front end side of the middle shaft And a glow plug comprising: In this glow plug, the middle shaft is press-fitted into the ring and is in contact with the inner peripheral surface of the ring; and is positioned on the rear end side of the press-fitting portion and on the end surface on the rear end side of the ring In the cross-section that appears when the central shaft is cut in the axial direction at a position passing through the press-fit portion and the contact portion, and the intermediate shaft that connects the press-fit portion and the contact portion. The contour has a concave portion that is recessed toward the rear end side from the contact portion. According to this aspect, since the contact between the center shaft and the ring is suppressed in the concave portion, the ring can be smoothly press-fitted into the press-fitting portion until the end surface of the ring comes into contact with the contact portion. As a result, the ring can be positioned with reference to the contact portion of the middle shaft. Therefore, the shaft runout of the middle shaft with respect to the ring can be suppressed. As a result, the stress applied to the heater element can be suppressed, and consequently damage to the heater element can be suppressed.

(2) In the glow plug of the above aspect, the contact portion may be in surface contact with the end face of the ring. According to this embodiment, stable contact with the ring by the contact portion can be realized.

(3) In the glow plug according to the aspect described above, a portion of the concave portion where the shaft diameter is thicker than the press-fit portion may be located on the rear end side from the contact portion. According to this form, the contact between the center shaft and the ring is further suppressed in the recess. Therefore, the shaft runout of the middle shaft with respect to the ring can be further suppressed.

(4) In the glow plug of the above aspect, in the cross section that appears when the central shaft and the ring are cut in the axial direction at a position passing through the press-fitting portion and the contact portion, the length of the contact portion is the length of the end face It may be shorter. According to this aspect, even when the flatness at the end face of the ring is lower than that of the contact portion, stable contact with the ring by the contact portion can be realized.

(5) In the glow plug according to the above aspect, the portion of the central shaft that extends from the press-fitted portion to the contact portion via the concave portion may be a portion formed by forging. According to this form, the flatness of the contact portion can be sufficiently secured.

(6) According to one aspect of the present invention, a heater element that generates heat when energized; a middle shaft that extends in the axial direction from the front end side to the rear end side; and a cylindrical shape that connects the heater element to the front end side of the middle shaft A method for manufacturing a glow plug is provided. In this manufacturing method, a press-fit portion that is press-fitted into the ring and is in contact with the inner peripheral surface of the ring is formed in the middle shaft; and a contact portion that is in contact with the end surface on the rear end side of the ring is The intermediate shaft that connects between the press-fit portion and the contact portion in a cross section that appears when the central shaft is cut in the axial direction at a position that passes through the press-fit portion and the contact portion. The middle shaft is formed such that the outline of the concave portion has a concave portion recessed toward the rear end side from the contact portion. According to this aspect, since the contact between the center shaft and the ring is suppressed in the concave portion, the ring can be smoothly press-fitted into the press-fitting portion until the end surface of the ring comes into contact with the contact portion. As a result, the ring is positioned with reference to the contact portion of the middle shaft. Therefore, the shaft runout of the middle shaft with respect to the ring can be suppressed. As a result, the stress applied to the heater element can be suppressed, and consequently damage to the heater element can be suppressed.

(7) In the method for manufacturing a glow plug in the above aspect, the ring may be press-fitted into the press-fitting portion until the end surface comes into surface contact with the contact portion. According to this embodiment, stable contact with the ring by the contact portion can be realized.

(8) In the method for manufacturing a glow plug according to the above aspect, the middle shaft may be formed so that a portion of the concave portion whose shaft diameter is thicker than the press-fitting portion is positioned on the rear end side from the contact portion. . According to this form, the contact between the center shaft and the ring is further suppressed in the recess. Therefore, the shaft runout of the middle shaft with respect to the ring can be further suppressed.

(9) In the method for manufacturing a glow plug according to the above aspect, in the cross section that appears when the center shaft and the ring are cut in the axial direction at a position passing through the press-fit portion and the contact portion, the length of the contact portion is The middle shaft may be formed so as to be shorter than the length of the end face. According to this aspect, even when the flatness at the end face of the ring is lower than that of the contact portion, stable contact with the ring by the contact portion can be realized.

(10) In the method for manufacturing a glow plug in the above aspect, the portion of the central shaft that extends from the press-fitted portion to the contact portion via the concave portion may be formed by forging. According to this form, the flatness of the contact portion can be sufficiently secured.

  The present invention can be realized in various forms other than the glow plug and the manufacturing method thereof. For example, it can be realized in the form of an internal combustion engine including the above-described glow plug, a central shaft used for the above-described glow plug, a manufacturing apparatus for manufacturing the above-described glow plug, and the like.

It is explanatory drawing which shows the structure of a glow plug. It is an expanded sectional view which shows a glow plug centering on the front end side of a center axis | shaft. It is explanatory drawing which shows the whole center axis | shaft. It is an enlarged view which shows the front end side in a center axis | shaft with a ring and a heater element. It is explanatory drawing which shows the cross section in a contact surface and a press-fit surface. It is process drawing which shows the manufacturing method of a glow plug.

A. Embodiment A1. Configuration of Glow Plug FIG. 1 is an explanatory diagram showing a configuration of the glow plug 10. The glow plug 10 is a heating device that functions as a heat source that assists ignition when starting an internal combustion engine (not shown) such as a diesel engine.

  FIG. 1 shows a cross-sectional shape of the glow plug 10 cut along a cross section passing through the axis AL of the glow plug 10. In the description of the present embodiment, the lower side of the glow plug 10 in FIG. 1 is referred to as “front end side”, and the upper side of FIG. 1 is referred to as “rear end side”.

  FIG. 1 shows the XYZ axes. The XYZ axes in FIG. 1 have an X axis, a Y axis, and a Z axis as three spatial axes orthogonal to each other. Of the X-axis directions along the X-axis, the + X-axis direction is a positive direction from the front of the paper to the back of the paper, and the −X-axis direction is a negative direction. Among the Y-axis directions along the Y-axis, the + Y-axis direction is a positive direction from the right side to the left side, and the −Y-axis direction is a negative direction. In the present embodiment, the Z axis is an axis along the axis AL of the glow plug 10. Among the Z-axis directions (axial directions) along the Z-axis, the + Z-axis direction is a positive direction from the front end side toward the rear end side, and the −Z-axis direction is a negative direction from the rear end side toward the front end side. Direction. The XYZ axes in FIG. 1 correspond to the XYZ axes in the other drawings.

  The glow plug 10 includes a terminal 100, a middle shaft 200, a metal shell 500, a ring 600, an outer cylinder 700, and a heater element 800. In the present embodiment, the axis AL of the glow plug 10 is also the axis of each member such as the terminal 100, the middle shaft 200, the metal shell 500, and the heater element 800.

  The terminal 100 of the glow plug 10 is a conductor configured to be connectable to a cable (not shown) that supplies power to the glow plug 10. In the present embodiment, the terminal 100 is made of metal (for example, carbon steel). In the present embodiment, the surface of the terminal 100 is plated (for example, tin (Sn), copper (Cu), nickel (Ni), silver (Ag), etc.).

  The middle shaft 200 of the glow plug 10 is a bar-shaped conductor extending in the axial direction from the front end side (−Z axis direction) to the rear end side (+ Z axis direction). In the present embodiment, the middle shaft 200 is made of metal (for example, stainless steel). The rear end side of the middle shaft 200 is inserted into the terminal 100. The front end side of the middle shaft 200 is press-fitted into the ring 600. Details of the middle shaft 200 will be described later.

  The metallic shell 500 of the glow plug 10 is a cylindrical conductor extending around the axis AL. In the present embodiment, the metallic shell 500 is made of metal (for example, carbon steel). In the present embodiment, the surface of the metal shell 500 is plated (for example, chromium (Cr), zinc (Zn), nickel (Ni), zinc-nickel alloy, etc.)). The metal shell 500 includes a shaft hole 510, a tool engaging portion 520, and a male screw portion 540.

  The shaft hole 510 of the metal shell 500 is a through hole extending around the axis AL. The inner diameter of the shaft hole 510 is larger than the outer shape of the middle shaft 200. Inside the shaft hole 510, the middle shaft 200 is held on the axis AL. A gap that electrically insulates the shaft hole 510 and the middle shaft 200 is formed between the shaft hole 510 and the middle shaft 200. In the present embodiment, the terminal 100 into which the rear end side of the middle shaft 200 is inserted is held on the rear end side of the shaft hole 510 via a cylindrical insulating member 300 and an annular insulating member 400. Yes. The tool engaging portion 520 of the metal shell 500 is configured to be engageable with a tool (not shown) used for attaching and removing the glow plug 10. The male screw portion 540 of the metal shell 500 is configured to be fixable to a female screw formed in an internal combustion engine (not shown). In the present embodiment, the male screw portion 540 is located on the tip side from the tool engaging portion 520.

  The ring 600 of the glow plug 10 is an annular conductor. In the present embodiment, the ring 600 is made of metal (for example, stainless steel). The middle shaft 200 is press-fitted on the rear end side of the ring 600. A heater element 800 is press-fitted on the tip side of the ring 600.

  The outer cylinder 700 of the glow plug 10 has a cylindrical shape extending about the axis AL. The heater element 800 is press-fitted into the outer cylinder 700 in a state where the heater element 800 protrudes from the front end side and the rear end side of the outer cylinder 700. The rear end side of the outer cylinder 700 is welded to the front end side of the metal shell 500.

  The heater element 800 of the glow plug 10 is a heating element (heating device) that generates heat when energized. In the present embodiment, the heater element 800 is a ceramic heater made of a ceramic composition. In the present embodiment, the heater element 800 includes a base 810 made of an insulating ceramic material and a heating resistor 830 made of a conductive ceramic material. A heating resistor 830 is embedded in the base 810. One end of the heating resistor 830 exposed on the side surface of the base 810 contacts the ring 600 and is electrically connected to the outside of the glow plug 10 via the ring 600, the middle shaft 200 and the terminal 100. The other end of the heating resistor 830 exposed on the side surface of the base 810 contacts the outer cylinder 700 and is electrically connected to the outside of the glow plug 10 via the outer cylinder 700 and the metal shell 500.

  FIG. 2 is an enlarged cross-sectional view showing the glow plug 10 with the front end side of the middle shaft 200 as the center. FIG. 3 is an explanatory diagram showing the entire middle shaft 200. FIG. 4 is an enlarged view showing the front end side of the middle shaft 200 together with the ring 600 and the heater element 800. The middle shaft 200 of the glow plug 10 has a shaft portion 250, a protruding portion 260, and a tip portion 270 on the tip side.

  The shaft portion 250 of the middle shaft 200 is a columnar portion located on the tip side of the shaft portion 240. In the present embodiment, the shaft portion 250 has a surface 258 connected to the protruding portion 260, and the surface 258 forms a corner R whose diameter gradually increases toward the protruding portion 260. In the present embodiment, the shaft portion 250 has a shape derived from the material from which the middle shaft 200 is based, except for the surface 258.

  The protruding portion 260 of the middle shaft 200 is a portion that is located on the distal end side of the shaft portion 250 and protrudes radially outward from the shaft portion 250. In the present embodiment, the protruding portion 260 is a portion formed by forging work on the material that is the base of the middle shaft 200. The protrusion 260 has a contact surface 265 and an outer peripheral surface 267.

  The contact surface 265 of the protruding portion 260 is a surface that is located on the rear end side with respect to the front end portion 270 and faces the front end side. The contact surface 265 is a contact portion that contacts the end surface 611 on the rear end side of the ring 600. In the present embodiment, the contact surface 265 is in surface contact with the end surface 611 of the ring 600. In the present embodiment, the contact surface 265 is a surface formed over the entire circumferential direction of the protruding portion 260. In other embodiments, the contact surface 265 may be a surface formed at two or more locations over the circumferential direction of the protrusion 260.

  In the present embodiment, the middle shaft 200 is welded to the ring 600 at the contact surface 265. In the present embodiment, the middle shaft 200 is welded to the ring 600 at a part of the contact surface 265. In other embodiments, the middle shaft 200 may be welded to the ring 600 across the contact surface 265. In other embodiments, the middle shaft 200 may not be welded to the ring 600.

  The outer peripheral surface 267 of the protrusion 260 is a surface that is located on the rear end side with respect to the contact surface 265 and faces the radially outer side. In the present embodiment, the outer peripheral surface 267 has a shape that expands radially outward from the center in the axial direction.

  The distal end portion 270 of the middle shaft 200 is a columnar portion that is located on the distal end side of the protruding portion 260 and has a smaller diameter than the protruding portion 260. In the present embodiment, the distal end portion 270 is a portion formed by forging work on the material that is the base of the middle shaft 200 together with the protruding portion 260. The tip 270 has an end surface 271, an inclined surface 273, and a press-fit surface 275.

  The end surface 271 of the distal end portion 270 constitutes an end surface on the distal end side of the middle shaft 200. The end surface 271 is a surface facing the front end side.

  The inclined surface 273 of the distal end portion 270 is located on the rear end side from the end surface 271 and is inclined with respect to the axis AL. The inclined surface 273 forms a tapered portion (inclined portion) whose diameter increases from the end surface 271 toward the press-fit surface 275.

  The press-fitting surface 275 of the distal end portion 270 is a surface that is located on the rear end side of the inclined surface 273 and extends along the axis AL. The press-fitting surface 275 is a contact portion that is press-fitted into the ring 600 and contacts the inner peripheral surface 613 of the ring 600.

  FIG. 5 is an explanatory diagram showing cross sections of the contact surface 265 and the press-fitting surface 275. The cross section of FIG. 5 is a cross section that appears when the central shaft 200 is cut in the axial direction at a position passing through the contact surface 265 and the press-fitting surface 275.

  In the cross section of FIG. 5, the outline of the central shaft 200 that connects between the contact surface 265 and the press-fitting surface 275 has a recess 280 that is recessed toward the rear end side from the contact surface 265. In the present embodiment, the recess 280 is a part formed by forging. In the present embodiment, the recess 280 is formed in the entire circumferential direction of the middle shaft 200. In another embodiment, when the end surface 611 of the ring 600 is uneven, the recess 280 may be partially formed at a position corresponding to the protrusion on the end surface 611.

  A base point PA in FIG. 5 indicates a connection point between the contact surface 265 and the recess 280. The recess 280 is located radially inward from the base point PA. In the cross section of FIG. 5, the length La of the contact surface 265 in the central shaft 200 is shorter than the length Lb of the end surface 611 in the ring 600. In other embodiments, the length La may be equal to or shorter than the length Lb.

  A base point PB in FIG. 5 indicates a connection point between the press-fitting surface 275 and the recess 280. Recess 280 is located on the rear end side from base point PB. In the present embodiment, the recess 280 has a larger shaft diameter than the press-fit surface 275 from the base point PB toward the rear end side. In the present embodiment, the portion of the recess 280 whose axial diameter is thicker than the press-fit surface 275 is located on the rear end side from the contact surface 265. In other embodiments, the portion of the recess 280 whose axial diameter is thicker than the press-fit surface 275 may be located on the distal side of the contact surface 265.

  In the present embodiment, as shown in FIG. 3, the middle shaft 200 includes a rear end shaft portion 210, a shaft portion 220, a shaft portion 230, and a shaft portion 240 in addition to the shaft portion 250, the protruding portion 260, and the front end portion 270. And have.

  The rear end shaft portion 210 of the middle shaft 200 is a columnar part having an end surface 211 on the rear end side. The end surface 211 is a surface facing the rear end side.

  The shaft portion 220 of the middle shaft 200 is a columnar portion adjacent to the front end side of the rear end shaft portion 210. In the present embodiment, knurls are formed on the surface of the shaft portion 220 by rolling. In another embodiment, knurls may be formed on the surface of the shaft portion 220 by cutting. In another embodiment, the end surface 211 may be formed on the rear end side of the shaft portion 220 where the knurling is formed without forming the rear end shaft portion 210.

  The shaft part 230 of the middle shaft 200 is a columnar part adjacent to the tip side of the shaft part 220. In the present embodiment, the shaft portion 230 has a shape derived from the material from which the middle shaft 200 is based.

  The shaft portion 240 of the middle shaft 200 is a columnar portion formed between the shaft portion 230 and the shaft portion 250. The shaft portion 240 has a plurality of reduced diameter portions 242 and a plurality of large diameter portions 247 that are alternately formed from the rear end side to the front end side. The reduced diameter portion 242 of the shaft portion 240 is a portion obtained by reducing the diameter of the material that is the base of the middle shaft 200 by rolling. The large-diameter portion 247 of the shaft portion 240 is a portion that has a shape derived from the material from which the middle shaft 200 is based. The diameter of the large diameter portion 247 is larger than the reduced diameter portion 242. The shaft runout of the middle shaft 200 is corrected by forming the plurality of reduced diameter portions 242 in the shaft portion 240. In another embodiment, the shaft portion 240 may be a columnar portion having a certain cross-sectional shape without having the reduced diameter portion 242 and the large diameter portion 247.

  FIG. 6 is a process diagram showing a method for manufacturing the glow plug 10. When manufacturing the glow plug 10, the manufacturer forms the middle shaft 200 by forging (step P112). In the present embodiment, the manufacturer forms each part of the protrusion 260, the tip 270, and the recess 280 by performing a forging process on the material from which the middle shaft 200 is based. In the present embodiment, the material from which the central shaft 200 is based is a coil material. After forming the middle shaft 200 by forging (step P112), the manufacturer forms the middle shaft 200 by rolling (step P114). In the present embodiment, the manufacturer forms each part of the central shaft 200 by rolling. In other embodiments, the order of forming each part of the central shaft 200 may be switched.

  After the middle shaft 200 is completed through the forging process (process P114), the manufacturer press-fits the rear end side of the heater element 800 to the front end side of the ring 600 (process P172). In the present embodiment, the manufacturer inserts the heater element 800 from the rear end side of the ring 600 with the front end side of the heater element 800 facing the ring 600, and the rear end side of the heater element 800 is the front end side of the ring 600. The heater element 800 continues to be inserted into the ring 600 until it is press-fitted into the ring 600. After press-fitting the heater element 800 into the ring 600 (process P172), the manufacturer press-fits the heater element 800 into the outer cylinder 700 by inserting the front end side of the heater element 800 from the rear end side of the outer cylinder 700 ( Process P174).

  After press-fitting the heater element 800 into the outer cylinder 700 (process P174), the manufacturer press-fits the front end portion 270 of the middle shaft 200 to the rear end side of the ring 600 into which the heater element 800 is press-fitted (process P176). In this embodiment, the manufacturer press-fits the ring 600 into the press-fit surface 275 until the end surface 611 of the ring 600 comes into surface contact with the contact surface 265 of the center shaft 200. In the present embodiment, the manufacturer welds the contact surface 265 of the central shaft 200 and the end surface 611 of the ring 600 (process P178). In other embodiments, the manufacturer may not weld the contact surface 265 of the central shaft 200 and the end surface 611 of the ring 600.

  After connecting the heater element 800 to the front end side of the middle shaft 200 via the ring 600 (process P178), the manufacturer inserts the rear end side of the middle shaft 200 from the front end side of the metal shell 500 (process P182). Thereafter, the manufacturer welds the outer cylinder 700 to the metal shell 500 (process P184).

  After welding the outer cylinder 700 to the metal shell 500 (process P184), the manufacturer inserts the middle shaft 200 into the terminal 100 (process P186). In the present embodiment, the manufacturer attaches the insulating member 300 and the insulating member 400 to the front end side of the terminal 100, and then attaches the rear end side of the middle shaft 200 protruding from the rear end side of the shaft hole 510 in the metal shell 500, While being inserted into the terminal 100, the distal end side of the terminal 100 together with the insulating member 300 and the insulating member 400 is inserted into the shaft hole 510 of the metal shell 500.

  After inserting the middle shaft 200 into the terminal 100 (process P186), the manufacturer performs caulking and fixing to secure the terminal 100 to the middle shaft 200 (step P188). In the caulking and fixing (process P188), the manufacturer fixes the terminal 100 to the center shaft 200 by compressing the terminal 100 from the outside to the inside. In other embodiments, the manufacturer may fix the terminal 100 to the central shaft 200 by welding. Through these steps, the glow plug 10 is completed.

  According to the embodiment described above, since the contact between the center shaft 200 and the ring 600 is suppressed in the recess 280, the ring 600 is smoothly press-fitted into the press-fit surface 275 until the end surface 611 of the ring 600 comes into contact with the contact surface 265. it can. Thereby, the ring can be positioned with reference to the contact surface 265 of the middle shaft 200. Therefore, the shaft runout of the middle shaft 200 with respect to the ring 600 can be suppressed. As a result, the stress applied to the heater element 800 can be suppressed, and as a result, damage to the heater element 800 can be suppressed.

  Further, since the contact surface 265 is in surface contact with the end surface 611 of the ring 600, stable contact with the ring 600 by the contact surface 265 can be realized.

  In addition, since the portion of the concave portion 280 whose shaft diameter is larger than the press-fitting surface 275 is located on the rear end side of the contact surface 265, the contact between the central shaft 200 and the ring 600 is further suppressed in the concave portion 280. Therefore, the shaft runout of the middle shaft 200 with respect to the ring 600 can be further suppressed.

  Further, since the length La of the contact surface 265 is shorter than the length Lb of the end surface 611, even when the flatness of the end surface 611 of the ring 600 is lower than that of the contact surface 265, the contact surface 265 is stable with the ring 600. Contact can be achieved.

  Moreover, since the site | part of the center axis | shaft 200 from the press-fit surface 275 to the contact surface 265 via the recessed part 280 is a site | part shape | molded by the forging process, the flatness of the contact surface 265 can fully be ensured.

B. Other Embodiments The present invention is not limited to the above-described embodiments, examples, and modifications, and can be realized with various configurations without departing from the spirit thereof. For example, the technical features in the embodiments, examples, and modifications corresponding to the technical features in each embodiment described in the summary section of the invention are to solve some or all of the above-described problems, or In order to achieve part or all of the above-described effects, replacement or combination can be performed as appropriate. Further, if the technical feature is not described as essential in the present specification, it can be deleted as appropriate.

  The present invention is not limited to a glow plug (so-called ceramic glow plug) including a heater element (so-called ceramic heater) in which a heating resistor 830 made of a conductive ceramic material is embedded in a base body 810 made of an insulating ceramic material. It can be applied to a glow plug provided with a heater element. For example, the present invention can be applied to a glow plug (so-called metal glow plug) including a heater element (so-called sheath heater) in which a heating coil formed of a conductive material is disposed inside a sheath tube.

  As shown in FIG. 5, the embodiment to which the present invention can be applied includes an inclined surface (tapered portion) connecting the end surface 611 and the outer peripheral surface, and an end surface 611 and an inner peripheral surface on the rear end side of the ring 600. The connecting inclined surface (tapered portion) is not limited to the formed embodiment. In other embodiments, the inclined surface may be formed only on the outer peripheral surface side, the inclined surface may be formed only on the inner peripheral surface side, or on either the outer peripheral surface side or the inner peripheral surface side. However, the inclined surface may not be formed. In the embodiment in which the inclined surface is not formed on the inner peripheral surface side, it is desirable that the base point PB is located on the rear end side from the contact surface 265.

DESCRIPTION OF SYMBOLS 10 ... Glow plug 100 ... Terminal 200 ... Middle shaft 210 ... Rear end shaft part 211 ... End surface 220 ... Shaft part 230 ... Shaft part 240 ... Shaft part 242 ... Reduced diameter part 247 ... Large diameter part 250 ... Shaft part 258 ... Surface 260 ... Protruding part 265 ... contact surface (contact part)
267 ... outer peripheral surface 270 ... tip portion 271 ... end surface 273 ... inclined surface 275 ... press-fit surface (press-fit portion)
280 ... concave portion 300 ... insulating member 400 ... insulating member 500 ... metal shell 510 ... shaft hole 520 ... tool engaging portion 540 ... male screw portion 600 ... ring 611 ... end face 613 ... inner peripheral surface 700 ... outer cylinder 800 ... heater element 810 ... Base 830 ... Heating resistor

Claims (8)

A heater element that generates heat when energized;
A middle shaft extending in the axial direction from the front end side to the rear end side;
A glow plug comprising: a cylindrical ring connecting the heater element to the tip side of the central shaft;
The central axis is
A press-fitting portion that is press-fitted into the ring and contacts an inner peripheral surface of the ring;
A contact portion located on the rear end side from the press-fitting portion and in contact with the end surface on the rear end side of the ring;
In the cross section that appears when the middle shaft is cut in the axial direction at a position that passes through the press-fitting portion and the contact portion, the contour of the middle shaft that connects between the press-fitting portion and the contact portion is behind the contact portion. have a recess which is recessed in the end-to-side,
The glow plug according to claim 1, wherein a portion of the concave portion having a larger shaft diameter than the press-fitting portion is located on the rear end side with respect to the contact portion .   The glow plug according to claim 1, wherein the contact portion is in surface contact with the end face of the ring. In the cross section that appears when the center pole and said ring at a position passing through the press-fit section and the contact portion is cut in the axial direction, the length of the contact portion is shorter than the length of the end face, claim 1 or claim 2 Glow plug as described in. The glow plug according to any one of claims 1 to 3 , wherein a portion of the central shaft that extends from the press-fitted portion to the contact portion via the recess is a portion formed by forging. A heater element that generates heat when energized;
A middle shaft extending in the axial direction from the front end side to the rear end side;
A glow plug manufacturing method for manufacturing a glow plug comprising: a cylindrical ring connecting the heater element to the tip side of the central shaft;
A press-fitting portion that is press-fitted into the ring and is in contact with the inner peripheral surface of the ring, is formed on the middle shaft;
Forming a contact portion in contact with the end surface on the rear end side of the ring on the rear end side from the press-fitting portion in the middle shaft;
In the cross section that appears when the middle shaft is cut in the axial direction at a position that passes through the press-fitted portion and the contact portion, the contour of the middle shaft that connects between the press-fit portion and the contact portion is behind the contact portion. It has a recess which is recessed on the end side, and
In the concave portion, the portion where the shaft diameter is thicker than the press-fit portion is positioned on the rear end side from the contact portion,
A method for manufacturing a glow plug, wherein the middle shaft is formed . The method for manufacturing a glow plug according to claim 5 , wherein the ring is press-fitted into the press-fitting portion until the end surface comes into surface contact with the contact portion. In the cross section that appears when the central shaft and the ring are cut in the axial direction at a position passing through the press-fitted portion and the contact portion, the central shaft is formed so that the length of the contact portion is shorter than the length of the end face A method for manufacturing a glow plug according to claim 5 or 6 . The method for manufacturing a glow plug according to any one of claims 5 to 7 , wherein a portion of the central shaft that extends from the press-fit portion to the contact portion via the concave portion is formed by forging.

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