JP5878815B2 - Glow plug and manufacturing method thereof - Google Patents

Description

  The present invention relates to a glow plug and a manufacturing method thereof.

  As a glow plug for preheating the combustion chamber of a diesel engine, for example, a cylindrical metal shell having an axial hole extending in the axial direction, a columnar metal shaft inserted into the shaft hole of the metal shell, a ceramic heater, and A glow plug having a cylindrical shape extending in the axial direction and including a metal connecting member (connecting ring) that connects a middle shaft and a ceramic heater is known (for example, see Patent Document 1). The coupling member is located on the proximal end side in the axial direction and is fitted on the distal end portion of the middle shaft, and the coupling member is located on the distal end side in the axial direction and connected to the proximal end portion of the ceramic heater. It has a tip.

JP 2009-74708 A

  By the way, as a method of fitting the base end of the connection to the front end of the central shaft, the front end of the central shaft is press-fitted into the connection base end from the base end side of the connection member (connection base end) and connected to the front end of the central shaft. There is a method of fitting (external fitting) the base end portion by interference fitting.

  However, as described above, when the distal end portion of the central shaft is press-fitted into the coupling proximal end portion of the coupling member from the proximal end side to the distal end side of the coupling member, the radially outer side of the central shaft distal end portion (the coupling proximal end) When the part (meat) on the side that contacts the inner peripheral surface of the part receives the force from the connecting base end part to the base end side in the axial direction, it moves to the base end side in the axial direction and the radial direction of the tip end part of the middle shaft In some cases, it protrudes outwardly in a bowl shape (in this application, this phenomenon is referred to as meat misalignment). This is because the material of the middle shaft tip is lower in hardness than the material of the connecting base end.

  For this reason, during press-fitting, the meat at the distal end portion of the middle shaft that protrudes outward due to meat displacement (a part of the distal end portion of the middle shaft) comes into contact with the connection base end portion from the base end side, and thereby the connection base There is a risk that press-fitting (moving in the press-fitting direction) of the front end of the middle shaft into the end may be hindered, and the middle shaft may not be properly press-fitted to a predetermined press-fitting completion position. As a result, the axial dimension of the glow plug may be out of the allowable range (too long).

  The present invention has been made in view of the present situation, and a method for manufacturing a glow plug capable of appropriately press-fitting a middle shaft tip portion into a connection base end portion, and a medium shaft tip portion appropriately within the connection base end portion. An object is to provide a glow plug that is press-fitted into a slab.

One aspect of the present invention includes a cylindrical metal shell having an axial hole extending in the axial direction, a columnar shape extending in the axial direction, and a metal central shaft inserted into the shaft hole of the metal shell, A ceramic heater having a heating resistor that generates heat, and a central shaft tip portion located on the tip end side in the axial direction of the middle shaft and a heater base end portion located on the base end side in the axial direction among the heaters A connecting member made of metal that is located on the proximal end side in the axial direction and is fitted on the distal end portion of the middle shaft, and a proximal end portion of the heater located on the distal end side in the axial direction A glow plug manufacturing method comprising: a coupling member having a coupling tip portion connected to a middle shaft fitting portion for fitting the middle shaft tip portion with the coupling base end portion by an interference fit. , Material whose hardness is lower than the connecting base end The intermediate shaft fitting portion, and a middle shaft concave portion recessed at the distal end portion of the middle shaft, wherein the middle shaft concave portion is adjacent to the proximal end side in the axial direction with respect to the middle shaft fitting portion. In a press-fitting external fitting process in which a distal end portion is press-fitted into the connection base end portion and the connection base end portion is externally fitted to the intermediate shaft fitting portion by an interference fit, a portion of the intermediate shaft fitting portion that is radially outside The portion that moves toward the axial base end side and protrudes outward in the radial direction by receiving a force from the connecting base end portion to the axial base end side during the press-fitting is connected to the connecting base end. A glow plug for inserting the middle shaft recess into the coupling base end while pushing into the middle shaft recess by the inner peripheral surface of the portion, and press-fitting the middle shaft tip into the coupling base end until reaching the press-fitting completion position. It is a manufacturing method.

  In the manufacturing method described above, for example, a middle shaft having the following middle shaft tip is used as the middle shaft. Specifically, the middle shaft front end portion is a middle shaft fitting portion that fits with a connection base end portion (for example, a cylindrical connection base end portion) by an interference fit, and has a lower hardness than the connection base end portion. And an annular middle shaft concave portion (provided in a shape recessed inward in the radial direction) that is recessed over the entire circumference of the distal end portion of the middle shaft, and is axially proximal to the middle shaft fitting portion A central axial recess adjacent to the side.

  Furthermore, the above-described manufacturing method includes a press-fitting external fitting process in which the center shaft tip is press-fitted into the connection base end from the base end side of the connection member, and the connection base end is externally fitted to the center shaft fitting portion by an interference fit. . In this press-fitting external fitting step, the middle shaft recess is inserted into the coupling base end, and the middle shaft tip is press-fitted into the coupling base end until reaching the press-fitting completion position. That is, of the front end portion of the middle shaft, a middle shaft concave portion is provided at a position where the middle shaft concave portion is inserted into the coupling base end portion until the middle shaft front end portion reaches the press-fitting completion position. Press fit.

  In other words, in the above-described manufacturing method, the base end surface of the connection base end portion reaches at least the press-fitting completion position reaching the center shaft recess (specifically, the base end surface of the connection base end portion is at least of the center shaft recess The intermediate shaft distal end is press-fitted into the connecting proximal end until the press-fitting completion position reaches the axial proximal end with respect to the distal end side edge located on the axial distal end side. That is, an intermediate shaft recess is provided at the front end of the center shaft so that a part or all of the center shaft recess is present on the front end side in the axial direction from the press-fitting completion position of the base end surface of the connection base end to the front end of the center shaft. The distal end portion is press-fitted into the connecting proximal end portion.

  For this reason, even if the portion (meat) on the radially outer side of the middle shaft fitting portion moves to the axial base end side and protrudes radially outward during the press-fitting due to meat displacement, When the distal end side edge of the concave portion advances beyond the proximal end surface of the coupling proximal end portion to the axial distal end side (the middle axial recessed portion is inserted into the coupling proximal end portion), The peripheral surface can be pushed (accommodated) into the central shaft recess. For this reason, it can suppress that the press fit of the center-axis front-end | tip part (center-axis fitting part) is prevented by the influence of a gap | deviation in the middle of press-fit. Therefore, according to the manufacturing method described above, it is possible to appropriately press-fit the middle shaft tip portion (middle shaft fitting portion) into the coupling base end portion.

  The “press-fit completion position” is a position where the middle shaft recess is inserted into the coupling base end portion and at least a part of the middle shaft recess is disposed in the connection base end portion. The completion position. Therefore, the “press-fit completion position” may be set to a position where a part of the middle shaft recess is disposed within the connection base end, or set to a position where the entire center shaft recess is disposed within the connection base end. There is also a case.

  Further, the middle shaft concave portion is a portion adjacent to the proximal end side in the axial direction with respect to the middle shaft fitting portion in the tip portion of the middle shaft. A plurality of middle shaft recesses may be formed at the tip of the middle shaft. When a plurality of middle shaft recesses are formed, the leading edge of each middle shaft recess advances to the distal end side in the axial direction beyond the base end surface of the connection base end (each medium shaft recess is inserted into the connection base end). Thus, the meat overhanging due to the meat misalignment (specifically, a part of the middle shaft fitting portion adjacent to the distal end side that is adjacent to the distal end side with respect to the middle shaft recess) projects over the outside in the radial direction. The inner peripheral surface can be pushed (accommodated) into the central shaft recess.

  Further, in the above-described method for manufacturing a glow plug, the intermediate shaft has a base end surface that is an end surface on the base end side in the axial direction of the connection base end portion on the base end side in the axial direction with respect to the concave portion of the central shaft. A contact portion having a form capable of contacting; and the press-fitting and fitting step includes inserting the intermediate shaft recess into the connection base end portion, and causing the base end surface of the connection base end portion to contact the intermediate shaft. It is preferable that the glow plug manufacturing method in which the distal end portion of the central shaft is press-fitted into the connection base end portion until the press-fitting completion position in contact with the portion is reached.

  In the manufacturing method described above, in the press-fitting and fitting step, the middle shaft distal end portion is press-fitted into the coupling base end portion until the base end surface of the coupling base end portion comes into contact with the contact portion of the middle shaft. That is, in the press-fitting external fitting step, the position at which the base end surface of the connection base end part comes into contact with the contact part of the center shaft is set as the press-fit completion position, and the center shaft tip part is press-fitted into the connection base end part. Conventionally, in such a press-fitting external fitting process, a part of the middle shaft tip portion that protrudes outwardly by slipping is sandwiched between the proximal end surface of the coupling proximal end portion and the contact portion of the middle shaft, and the connection In some cases, the base end surface of the base end cannot be brought into contact with the contact portion of the center shaft (that is, the press-fit completion position is reached).

  On the other hand, in the manufacturing method described above, an intermediate shaft having an abutting portion in a form in which the proximal end surface of the coupling proximal end portion can abut on the proximal side in the axial direction with respect to the intermediate shaft recess is used as the intermediate shaft. In other words, the middle shaft in which the middle shaft concave portion is formed is used at a position on the distal end side in the axial direction with respect to the contact portion of the middle shaft (that is, a position inserted into the coupling base end portion).

  For this reason, in the press-fitting external fitting step, before the abutting portion of the middle shaft abuts on the base end surface of the connecting member, the middle shaft concave portion moves to the front end side in the axial direction from the base end surface of the connecting member (that is, the connecting base Inserted into the end). Thereby, in the middle of press-fitting, even if the outer portion (meat) of the middle shaft fitting portion has protruded radially outward due to meat displacement, the middle shaft recess is inserted into the coupling base end portion, This overhanging meat can be pushed (accommodated) into the central shaft recess by the inner peripheral surface of the connecting base end. Therefore, according to the above-described manufacturing method, the distal end portion of the center shaft is press-fitted into the connection base end portion, and the base end surface of the connection member (connection base end portion) is reliably brought into contact with the contact portion of the center shaft. Can do.

Another aspect of the present invention is a cylindrical metallic shell having an axial hole extending in the axial direction, a columnar shape extending in the axial direction, and a metal central shaft inserted into the axial hole of the metallic shell, A ceramic heater having a heating resistor that generates heat when energized, a middle shaft distal end portion located on the distal end side in the axial direction of the middle shaft, and a heater proximal end portion located on the proximal end side in the axial direction among the heaters. A connecting member made of metal to be connected, which is located on the proximal end side in the axial direction and is fitted on the distal end portion of the middle shaft; and the proximal end of the heater located on the distal end side in the axial direction And a connecting member having a connecting tip portion connected to the portion, wherein the center shaft tip portion is a center shaft fitting portion formed by externally fitting the connecting base end portion with an interference fit, and the connecting base end Middle shaft fitting part made of a material whose hardness is lower than the part, and Serial A center pole recess recessed in the center pole tip has a center shaft recess, adjacent to the axial direction base end side with respect to said intermediate shaft fitting portion, the above-mentioned state of being press-fitted into the connecting base end portion Of the distal end portion of the middle shaft, the middle shaft concave portion has a part or all of the middle shaft concave portion on the distal end side in the axial direction from the press-fitting completion position of the proximal end surface of the connection proximal end portion with respect to the middle shaft distal end portion. The glow plug accommodates a portion of the middle shaft fitting portion that is a radially outer portion of the middle shaft concave portion and that projects to the proximal side in the axial direction .
Also, a cylindrical metal shell having an axial hole extending in the axial direction, a columnar shape extending in the axial direction, a metal central shaft inserted into the shaft hole of the metal shell, and a heating resistor that generates heat when energized A metal heater that connects a ceramic heater having a body, a middle shaft tip portion located on the tip end side in the axial direction of the middle shaft, and a heater base end portion located on the base end side in the axial direction of the heater. A connecting base end portion that is located on the axial base end side and is fitted on the tip end portion of the middle shaft, and a connection that is positioned on the tip end side in the axial direction and connected to the heater base end portion A connecting member having a distal end portion, and the middle shaft distal end portion is a middle shaft fitting portion formed by externally fitting the coupling base end portion with an interference fit, and has a hardness lower than that of the connection base end portion. Middle shaft fitting portion made of material, and the above-mentioned middle shaft tip portion A recessed portion of the intermediate shaft, the intermediate shaft recessed portion adjacent to the proximal end side in the axial direction with respect to the intermediate shaft fitting portion, and the intermediate shaft recessed portion is inserted into the connecting proximal end portion, and the press-fit completion position A glow plug formed by press-fitting the distal end portion of the central shaft into the connecting base end portion is preferable.

  The glow plug described above uses, for example, a middle shaft having the following middle shaft tip as the middle shaft. Specifically, the middle shaft front end portion is a middle shaft fitting portion that fits with a connection base end portion (for example, a cylindrical connection base end portion) by an interference fit, and has a lower hardness than the connection base end portion. And an annular middle shaft concave portion (provided in a shape recessed inward in the radial direction) that is recessed over the entire circumference of the distal end portion of the middle shaft, and is axially proximal to the middle shaft fitting portion A central axial recess adjacent to the side.

  In addition, the middle shaft concave portion is inserted into the coupling base end portion, and the middle shaft distal end portion is press-fitted into the coupling base end portion until reaching the press-fit completion position. That is, the middle shaft recess is provided at a position where the middle shaft recess is inserted into the coupling base end before the middle shaft leading end reaches the press-fitting completion position. It is press-fitted into the club.

  In other words, the middle shaft distal end portion is press-fitted into the connection proximal end portion until the proximal end surface of the connection proximal end portion reaches at least the press-fitting completion position reaching the middle shaft concave portion. In other words, the center shaft recess is provided at the tip of the center shaft so that a part or all of the center shaft recess exists on the tip end side in the axial direction from the press-fitting completion position of the base end surface of the connection base end to the center shaft tip. The middle shaft tip is press-fitted into the coupling base end.

  Therefore, as described above, while the middle shaft fitting portion is being press-fitted into the connection base end portion, the portion outside the middle shaft fitting portion (meat) is moved to the base end side in the axial direction due to the displacement of the meat. Even if the outer end of the central shaft is protruded radially outward, the leading edge of the central shaft recess extends beyond the base end surface of the connecting member to the front end side (the central shaft concave portion is inserted into the connecting base end). The inner peripheral surface of the connecting base end portion is pushed (accommodated) into the middle shaft recess. For this reason, during the press-fitting, the press-fitting of the center shaft fitting portion is not hindered due to the influence of the meat deviation. Therefore, the above-described glow plug is a glow plug in which the middle shaft fitting portion is appropriately press-fitted inside the connecting member (connecting base end portion).

Further, in the above glow plug, the intermediate shaft can contact a proximal end surface that is an end surface on the axial proximal end side of the connecting proximal end portion, closer to the axial proximal end side than the intermediate shaft recess. It is preferable that the base end surface of the connection base end portion is a glow plug that is in contact with the contact portion of the central shaft .
Further, in the glow plug, the middle shaft may be in contact with a proximal end surface which is an end surface on the axial direction proximal end side of the connecting proximal end portion, closer to the axial proximal end side than the middle shaft recess. The intermediate shaft recess is inserted into the connection base end portion, and the base end surface of the connection base end portion reaches the press-fitting completion position where the base end surface contacts the contact portion of the center shaft. Until now, it is preferable to use a glow plug formed by press-fitting the distal end portion of the central shaft into the connecting base end portion.

  The glow plug described above uses, as a middle shaft, a middle shaft having an abutting portion in a form in which the proximal end surface of the coupling proximal end portion can abut on the proximal side in the axial direction with respect to the middle shaft concave portion. In other words, the middle shaft in which the middle shaft recess is formed in a portion of the middle shaft that is closer to the tip in the axial direction than the contact portion (that is, a portion that is inserted into the coupling base end).

  For this reason, as described above, even if the outer portion (meat) of the intermediate shaft fitting portion protrudes radially outward due to the meat displacement during press-fitting, the base end surface of the connecting member is the contact portion of the intermediate shaft. Prior to abutting on (that is, before reaching the press-fitting completion position), the overhanging meat is pushed (accommodated) into the concave portion of the central shaft by the inner peripheral surface of the coupling base end. Therefore, the glow plug described above is a glow plug in which the base end surface of the connecting member is in contact with the contact portion of the center shaft.

It is a longitudinal cross-sectional view of the glow plug concerning embodiment. It is a figure explaining the manufacturing method of the glow plug concerning an embodiment. It is another figure explaining the manufacturing method of the glow plug concerning embodiment. It is another figure explaining the manufacturing method of the glow plug concerning embodiment. It is a figure explaining the press fit external fitting process concerning embodiment. It is another figure explaining the press fit external fitting process concerning embodiment. It is another figure explaining the press fit external fitting process concerning embodiment. It is another figure explaining the press fit external fitting process concerning embodiment. It is another figure explaining the manufacturing method of the glow plug concerning embodiment. It is another figure explaining the manufacturing method of the glow plug concerning embodiment. It is another figure explaining the manufacturing method of the glow plug concerning embodiment. It is another figure explaining the manufacturing method of the glow plug concerning embodiment. It is a figure explaining the manufacturing method of the glow plug concerning a modification. It is a figure explaining the conventional press fit external fitting process. It is another figure explaining the conventional press fit external fitting process.

(Embodiment)
Next, embodiments of the present invention will be described with reference to the drawings.
First, the glow plug 100 according to the embodiment will be described. FIG. 1 is a longitudinal sectional view of the glow plug 100. As shown in FIG. 1, the glow plug 100 is attached to, for example, the attachment hole 155 of the direct injection diesel engine 150 and is used as a heat source that assists ignition when the engine 150 is started.

The glow plug 100 includes a metal shell 40 having a shaft hole 43 extending in an axial direction (a direction along the axis AX, a vertical direction in FIG. 1), a middle shaft 30 inserted into the shaft hole 43 of the metal shell 40, the ceramic heater 20, A heater holding member 80 and a connecting member 75 that connects the central shaft distal end portion 34 and the heater base end portion 23 are provided.
The middle shaft tip portion 34 is a portion located on the tip side in the axial direction (lower side in FIG. 1) of the middle shaft 30. Further, the heater base end portion 23 is a portion located on the base end side (upper side in FIG. 1) in the axial direction of the ceramic heater 20.

  Among these, the ceramic heater 20 has a round bar shape, and includes a base body 21 and a heating element 24 embedded in the base body 21 (see FIG. 1). The base 21 is made of an insulating ceramic, and the tip (heater tip 22) is hemispherically curved. The heating element 24 is made of a conductive ceramic and has a substantially U shape.

  The heating element 24 includes a heating resistor 27 disposed at the heater tip 22 and leads 28 and 29 connected to the ends of the heating resistor 27, respectively. The heating resistor 27 has a substantially U shape that fits the curved surface of the heater tip 22. The lead portions 28 and 29 extend from the end portion of the heating resistor 27 toward the base end portion 23 of the ceramic heater 20 substantially in parallel along the axis AX.

  The heat generating resistor 27 has a cross-sectional area smaller than that of the lead portions 28 and 29, and heat is generated mainly in the heat generating resistor 27 when energized. When the glow plug 100 is attached to the attachment hole 155 of the engine 150, the heater tip 22 where the heating resistor 27 is disposed is exposed in the combustion chamber 160 (see FIG. 1). In addition, on the outer peripheral surface on the base end side from the center of the ceramic heater 20, electrode extraction portions 25 and 26 that protrude radially outward from the lead portions 28 and 29 are exposed at positions shifted from each other in the axial direction. doing.

  The heater holding member 80 is made of a cylindrical metal member extending in the axial direction, and holds the body portion of the ceramic heater 20 in the radial direction in its own cylindrical hole 84. The heater holding member 80 exposes the heater front end portion 22 and the heater base end portion 23 from both ends of the cylindrical hole 84 (see FIG. 1). Of the electrode extraction portions 25 and 26 of the ceramic heater 20, the electrode extraction portion 25 formed on the distal end side is in contact with the inner peripheral surface of the cylindrical hole 84 of the heater holding member 80, and the electrode extraction portion 25 and the heater holding member 80 is electrically connected.

  The heater holding member 80 includes a cylindrical trunk portion 81, a thick collar portion 82 located on the proximal side of the cylindrical trunk portion 81, a tapered locking portion 85 located between the trunk portion 81 and the collar portion 82, And it has the metal fitting fitting part 83 adjacent to the base end of the collar part 82 (refer FIG.1 and FIG.3). When the glow plug 100 is attached to the attachment hole 155 of the engine 150, the engagement part 85 engages with a step 156 provided in the attachment hole 155, and the inside of the combustion chamber 160 through the attachment hole 155. To prevent gas leakage (see FIG. 1). The metal fitting part 83 is a cylindrical part for joining with a metal shell 40 to be described later, and the front end 41 of the metal shell 40 is fitted by press fitting.

  The connecting member 75 is made of metal and has a cylindrical shape (see FIGS. 1 and 3). The connecting member 75 is located on the proximal end side in the axial direction and is cylindrically connected to the distal end portion 34c of the middle shaft, and the heater proximal end portion 23 is located on the distal end side in the axial direction. It has the connection tip part 75b connected to. Specifically, the connecting distal end portion 75 b is externally fitted to the heater base end portion 23 exposed to the base end side from the metal fitting fitting portion 83 of the heater holding member 80.

  The electrode extraction portion 26 of the ceramic heater 20 is in contact with the inner peripheral surface of the connecting member 75. Thereby, the electrode extraction part 26 and the connection member 75 are electrically connected. Further, the front end portion 41 of the metallic shell 40 is joined to the fitting fitting portion 83 of the heater holding member 80. Thereby, the metal shell 40 and the heater holding member 80 are electrically connected. The heater base end portion 23 and the connecting member 75 of the ceramic heater 20 are disposed in the metal shell 40. However, the ceramic heater 20 and the metal shell 40 are respectively positioned on the heater holding member 80 and connected to the metal shell 40. Since the member 75 is maintained in a non-contact state, both are electrically insulated.

  The metal shell 40 is a cylindrical metal member having a shaft hole 43 penetrating in the axial direction (see FIG. 1). The metal shell 40 has a cylindrical middle body portion 44. On the proximal end side of the middle body portion 44, a screw portion 42 having a thread on the outer peripheral surface 45 is provided. When the glow plug 100 is attached to the attachment hole 155 of the engine 150, the screw portion 42 is screwed with a female screw 157 provided in the attachment hole 155 to fix the glow plug 100.

  Further, a tool engagement portion 46 that engages a tool used when the glow plug 100 is attached to the engine 150 is formed on the base end side of the middle barrel portion 44 (screw portion 42). The tool engaging portion 46 has a hexagonal cross section. The shaft hole 43 extends in a cylindrical shape from the distal end of the metallic shell 40 toward the proximal end side, is expanded in diameter in the tool engaging portion 46, and is connected to an opening on the proximal end side of the metallic shell 40.

  Further, the distal end portion 41 of the metal shell 40 is externally fitted to the metal fitting fitting portion 83 of the heater holding member 80 by press fitting. The inner periphery of the distal end portion 41 of the metal shell 40 is in close contact with the outer periphery of the metal fitting fitting 83. The fitting portion between the front end portion 41 of the metal shell 40 and the fitting fitting portion 83 is laser welded over the entire circumference. Thereby, the metal shell 40 and the heater holding member 80 are joined together.

  The middle shaft 30 is made of metal, has a column shape extending in the axial direction, and is inserted into the shaft hole 43 of the metal shell 40 (see FIG. 1). The middle shaft 30 includes a cylindrical tip portion (a middle shaft tip portion 34), a portion adjacent to the proximal end side in the axial direction with respect to the middle shaft tip portion 34, and a large diameter portion 31 larger in diameter than the middle shaft tip portion 34. And a proximal end portion (middle shaft proximal end portion 32) located on the most proximal side. Of these, the large-diameter portion 31 is a contact portion 31d (a portion having an annular contact surface facing the distal end side in the axial direction, which is in contact with the proximal end surface 75d of the connecting member 75 fitted on the intermediate shaft distal end portion 34, 5).

  In the present embodiment, the connecting base end portion 75c of the connecting member 75 is externally fitted to the intermediate shaft distal end portion 34, so that the ceramic heater 20 and the intermediate shaft 30 are integrally connected in the axial direction via the connecting member 75. Yes. Thereby, the middle shaft 30 and the electrode extraction part 26 of the ceramic heater 20 are electrically connected through the connecting member 75. The base end surface 75d of the connecting member 75 is in contact with the contact portion 31d of the middle shaft 30.

  Further, in the present embodiment, the middle shaft 30 is made of a metal whose hardness is lower than that of the connecting member 75. Specifically, the middle shaft 30 is made of SUS430, and the connecting member 75 is made of SUS410. Therefore, the hardness of the middle shaft distal end portion 34 is lower than that of the connection proximal end portion 75c.

  By the way, in the present embodiment, the middle shaft distal end portion 34 is press-fitted into the coupling proximal end portion 75c of the coupling member 75, and the coupling proximal end portion is inserted into the middle shaft distal end portion 34 (more specifically, a middle shaft fitting portion 34b described later). 75c is externally fitted with an interference fit.

  Conventionally, as shown in FIG. 14 to FIG. 15, when the center shaft tip 434 is press-fitted into the connection base end 75 c of the connection member 75, the center shaft tip 434 is radially outward (the connection base end 75 c The portion (meat) on the side contacting the inner peripheral surface 75f) receives a force from the connecting base end portion 75c to the base end side in the axial direction (upper side in FIG. 15), thereby moving to the base end side in the axial direction. In some cases, it protrudes in the form of a bowl on the outer side in the radial direction of the tip end portion 434 of the central shaft (this phenomenon is referred to as meat displacement). This is because the material of the middle shaft front end portion 434 is lower in hardness than the material of the connection base end portion 75c.

  For this reason, during the press-fitting, the meat of the central shaft distal end portion 434 projecting outward due to the meat shift (referred to as the projecting meat 434g) comes into contact with the connection base end portion 75c from the base end side, and thereby the connection base In some cases, the press-fitting (moving in the press-fitting direction) of the middle shaft front end portion 434 into the end portion 75c is prevented, and the middle shaft 430 cannot be properly press-fitted to a predetermined press-fitting completion position. Specifically, an overhang 434g is sandwiched between the base end surface 75d of the connection base end portion 75c and the contact portion 431d of the center shaft 430, and the base end surface 75d of the connection base end portion 75c is connected to the contact portion of the center shaft 430. 431d may not be brought into contact with the 431d. As a result, the axial dimension of the glow plug 100 may be out of the allowable range (too long).

  On the other hand, in the present embodiment, as shown in FIG. 5, the middle shaft distal end portion 34 is a middle shaft fitting portion 34 b in which the coupling base end portion 75 c is fitted by an interference fit and is harder than the coupling base end portion 75 c. A middle shaft fitting portion 34b made of a low material, and an annular middle shaft concave portion 34c that is recessed over the entire circumference of the middle shaft tip portion 34 and is axially proximal to the middle shaft fitting portion 34b (upper side in FIG. 5) ) Adjacent to the central shaft recess 34c.

  For this reason, as shown in FIG. 6, a portion (meat) on the radially outer side of the center shaft fitting portion 34 b moves to the axial base end side (upper side in FIG. 6) due to a meat shift during press-fitting. Even if it protrudes outward in the radial direction, as shown in FIG. 7, the distal end side edge 34d of the central shaft concave portion 34c exceeds the proximal end surface 75d of the coupling proximal end portion 75c to the distal end side in the axial direction (upper side in FIG. 7). By proceeding (the middle shaft concave portion 34c is inserted into the coupling base end portion 75c), the protruding meat 34g can be pushed (accommodated) into the middle shaft concave portion 34c by the inner peripheral surface 75f of the coupling base end portion 75c. it can.

  For this reason, it is possible to suppress the press-fitting of the central shaft tip portion 34 from being hindered due to the shift of the meat during the press-fitting. Therefore, as shown in FIG. 8, the press-fitting completion position (the position shown in FIG. 8, the base end surface 75d of the connecting member 75 is in contact with the contact portion 31d of the intermediate shaft 30 is inserted into the connecting base end portion 75c. The middle shaft distal end portion 34 can be press-fitted into the coupling proximal end portion 75c until it reaches the contact position).

  Therefore, the glow plug 100 of the present embodiment is a glow plug in which the middle shaft distal end portion 34 (the middle shaft fitting portion 34b) is appropriately press-fitted into the coupling member 75 (the coupling base end portion 75c). Specifically, as shown in FIG. 8, the glow plug 100 of the present embodiment is a glow plug in which the base end surface 75 d of the connecting member 75 is in contact with the contact portion 31 d of the middle shaft 30. Specifically, in the glow plug 100 of the present embodiment, the press-fit is completed in which the middle shaft recess 34 c is inserted into the connection base end portion 75 c and the base end surface 75 d of the connection base end portion 75 c contacts the contact portion 31 d of the middle shaft 30. Until reaching the position, the middle shaft tip portion 34 becomes a glow plug press-fitted into the coupling base end portion 75c.

  Further, the contact portion between the middle shaft 30 (contact portion 31d) and the connection member 75 (connection base end portion 75c) is laser-welded over the entire circumference (see FIGS. 1 and 9). Thereby, the middle shaft 30 and the connecting member 75 are integrated. Further, as described above, since the ceramic heater 20 and the metal shell 40 are respectively positioned on the heater holding member 80, the intermediate shaft 30 and the metal shell 40 are in a non-contact state within the shaft hole 43 of the metal shell 40. Maintained and electrically isolated.

  A part of the proximal end portion of the intermediate shaft 30 (the intermediate shaft proximal end portion 32) protrudes from the proximal end of the metal shell 40 to the proximal end side (see FIG. 1). The base end portion 32 is fitted with an O-ring 70 and a cylindrical insulating support ring 60 having an insertion hole. The O-ring 70 is made of an elastic member having an insulating property such as fluorine rubber, acrylic rubber, or silicon rubber, and is formed in an annular shape. The support ring 60 is disposed so as to be pushed into a portion where the diameter of the shaft hole 43 of the metal shell 40 is expanded, and is responsible for positioning of the middle shaft 30 inserted through itself and insulation between the middle shaft 30 and the metal shell 40. ing.

  Further, the O-ring 70 is pressed against the front end surface of the support ring 60, closely contacts the inner peripheral surface of the shaft hole 43 and the outer peripheral surface of the central shaft base end portion 32 of the metal shell 40, and seals the inside of the metal shell 40. It has stopped. Further, the terminal fitting 50 is fitted into a portion of the middle shaft base end portion 32 that protrudes from the base end of the support ring 60 toward the base end side. When the glow plug 100 is attached to the engine 150, a plug cap (not shown) is fitted into the terminal fitting 50, and power is supplied from an external circuit.

Next, a method for manufacturing a glow plug according to the present embodiment will be described.
First, as shown in FIG. 2, the ceramic heater 20 is produced in a heater formation process. Specifically, first, an element molded body 351 that is the original shape of the heating element 24 of the ceramic heater 20 is formed by injection molding using conductive ceramic powder, a binder, or the like as a raw material.

On the other hand, die press molding is performed using insulating ceramic powder as a raw material to form a base molded body 352 that is the original form of the base 21. Specifically, the base molded body 352 is formed as a two-divided molded body having a concave portion in which the element molded body 351 is accommodated.
Next, while the element molded body 351 is accommodated in the recesses of the base molded bodies 352 and 352, the base molded bodies 352 and 352 are overlapped and press-compressed. Then, the ceramic heater 20 is formed by polishing the outer peripheral surface into a hemispherical rod shape through a baking process such as binder removal processing and hot pressing.

  Next, as shown in FIG. 3, in the heater press-fitting step, the ceramic heater 20 is press-fitted into the connecting member 75 from the front end (heater front end 22) side, and the heater base end 23 is connected to the connecting member 75. The connecting tip 75b is fitted (see FIG. 1). Thereby, the electrode extraction part 26 of the ceramic heater 20 and the connecting member 75 are electrically connected. Subsequently, the ceramic heater 20 is press-fitted and fitted into the heater holding member 80 from the front end (heater front end 22) side. Thereby, the electrode extraction part 25 of the ceramic heater 20 and the heater holding member 80 are electrically connected (refer FIG. 1). In the heater press-fitting step, the ceramic heater 20, the heater holding member 80, and the connecting member 75 that are assembled together are referred to as a heater assembly member 350 (see FIG. 4).

  Next, as shown in FIG. 4 and FIG. 5, a middle shaft 30 having a middle shaft tip portion 34 having a middle shaft fitting portion 34 b and a middle shaft recess 34 c is prepared. Then, the heater base member 350 is press-fitted into the connection base end portion 75c of the connection member 75, and the connection base end portion 75c is externally fitted to the center shaft fitting portion 34b of the center shaft front end portion 34 by an interference fit. More specifically, as shown in FIG. 8, the middle shaft distal end portion 34 is moved into the coupling proximal end portion 75c until the middle shaft recessed portion 34c of the middle shaft distal end portion 34 reaches the press-fitting completion position to be inserted into the coupling proximal end portion 75c. Press fit into. More specifically, the intermediate shaft distal end portion 34 is connected to the connection proximal end portion 75c until the proximal end surface 75d of the connection member 75 reaches a position where the proximal end surface 75d contacts the contact portion 31d of the intermediate shaft 30 (this position is the press-fit completion position of the present embodiment). Press fit inside.

  By the way, as shown in FIG. 5, the middle shaft distal end portion 34 of the present embodiment has the entire middle shaft distal end portion 34 in a position adjacent to the axial proximal end side (upper side in FIG. 5) with respect to the middle shaft fitting portion 34 b. An annular middle shaft recess 34c that is recessed over the circumference is provided.

  For this reason, as shown in FIG. 6, a portion (meat) on the radially outer side of the center shaft fitting portion 34 b moves to the axial base end side (upper side in FIG. 6) due to a meat shift during press-fitting. Even if it protrudes outward in the radial direction, as shown in FIG. 7, the distal end side edge 34d of the central shaft concave portion 34c exceeds the proximal end surface 75d of the coupling proximal end portion 75c to the distal end side in the axial direction (upper side in FIG. 7). By proceeding (the middle shaft concave portion 34c is inserted into the coupling base end portion 75c), the protruding meat 34g can be pushed (accommodated) into the middle shaft concave portion 34c by the inner peripheral surface 75f of the coupling base end portion 75c. it can.

  For this reason, it can suppress that the press fit of the center axis | shaft front-end | tip part 34 is prevented by the influence of a gap | deviation in the middle of a press fit external fitting process. Therefore, as shown in FIG. 8, the press-fitting completion position (the position shown in FIG. 8, the base end surface 75d of the connecting member 75 is in contact with the contact portion 31d of the intermediate shaft 30 is inserted into the connecting base end portion 75c. The middle shaft distal end portion 34 can be press-fitted into the coupling proximal end portion 75c until it reaches the contact position).

  Therefore, according to the manufacturing method of the present embodiment, the middle shaft distal end portion 34 (the middle shaft fitting portion 34b) can be appropriately press-fitted into the connection base end portion 75c. Thereby, the base end surface 75d of the connection member 75 (connection base end part 75c) can be reliably brought into contact with the contact part 31d of the middle shaft 30.

  Next, as shown in FIG. 9, in the intermediate shaft joining step, the contact portion between the intermediate shaft 30 (contact portion 31d) and the connection member 75 (connection base end portion 75c) is laser-welded over the entire circumference thereof. 30 and the heater integrated member 350 are joined and integrated. Specifically, the laser beam LB is irradiated over the entire outer periphery of the portion where the middle shaft 30 (contact portion 31d) and the connection member 75 (connection base end portion 75c) come into contact with each other. Are integrated by welding. Note that a unit in which the middle shaft 30 and the heater integrated member 350 are integrated is referred to as a middle shaft integrated member 360.

  Next, as shown in FIG. 10, in the fitting process, the middle shaft 30 of the middle shaft integrated member 360 is inserted into the shaft hole 43 of the metal shell 40 from the middle shaft base end portion 32 side. Then, the fitting fitting portion 83 of the heater holding member 80 is press-fitted into the distal end portion 41 of the metallic shell 40, and the distal end portion 41 of the metallic fitting 40 and the fitting fitting portion 83 are fitted.

  Thereafter, as shown in FIG. 11, in the metal fitting joining step, the contact portion between the tip 41 of the metal shell 40 and the heater holding member 80 is laser-welded over the entire circumference, and the metal shell 40 and the central shaft integral member 360 are Is integrated. More specifically, the entire outer periphery of the tip 41 of the metal shell 40 is irradiated with the laser beam LB, and the metal shell 40 and the central shaft integrated member 360 are integrated by welding.

  Next, as shown in FIG. 12, in the terminal assembly step, the O-ring 70 and the support ring 60 are externally fitted to the central shaft base end portion 32, and the diameter-enlarged portion of the shaft hole 43 of the metal shell 40. House inside. Further, the terminal fitting 50 is fitted into the central shaft base end portion 32, and the support ring 60 is pressed toward the distal end side by the terminal fitting 50. In this state, the terminal fitting 50 is fixed to the middle shaft 30 by crimping the outer periphery of the trunk portion 52 of the terminal fitting 50. Through such a process, the glow plug 100 is completed.

(Deformation)
Next, modifications of the present invention will be described. This modified embodiment differs from the embodiment in the form of the tip of the central shaft, and the other is the same.

  Specifically, as shown in FIG. 13, the middle shaft tip 234 of the middle shaft 230 according to the modified embodiment has two middle shaft recesses, unlike the middle shaft tip 34 (see FIG. 5) of the embodiment. Specifically, the middle shaft distal end portion 234 includes a first middle shaft fitting portion 234b1, a first middle shaft concave portion 234c1 adjacent to the first base shaft side (upper side in FIG. 13) with respect to the first middle shaft fitting portion 234b1, and A second intermediate shaft fitting portion 234b2 adjacent to the first intermediate shaft recess portion 234c1 on the axial direction proximal end side, and a second intermediate shaft recess portion 234c2 adjacent to the second intermediate shaft fitting portion 234b2 on the axial direction proximal end side. ing.

  Each of the first middle shaft fitting portion 234b1 and the second middle shaft fitting portion 234b2 is made of a material having a lower hardness than the connection base end portion 75c. Further, the first center shaft recess 234 c 1 and the second center shaft recess 234 c 2 are both radially inward of the outer periphery of the first center shaft fitting portion 234 b 1 and the second center shaft fitting portion 234 b 2 over the entire circumference of the center shaft tip portion 34. It is an annular recessed part recessed in the.

  When the intermediate shaft front end portion 234 having such a configuration is press-fitted into the coupling base end portion 75c, first, a slippage occurs in the first middle shaft fitting portion 234b1, and thereby the diameter of the first middle shaft fitting portion 234b1. Meat may overhang outside in the direction. However, thereafter, the distal end side edge 234d1 of the first middle shaft recess 234c1 advances to the distal end side in the axial direction beyond the proximal end surface 75d of the connection base end portion 75c (the first center shaft recess 234c1 is inserted into the connection base end portion 75c). Thus, the overhanging meat can be pushed (accommodated) into the first middle shaft recess 234c1 by the inner peripheral surface 75f of the coupling base end portion 75c.

  Subsequently, when the middle shaft distal end portion 234 is press-fitted into the coupling base end portion 75c, a flesh shift occurs in the second middle shaft fitting portion 234b2, thereby causing the second middle shaft fitting portion 234b2 to be radially outward. Meat may overhang. However, after that, the distal end side edge 234d2 of the second middle shaft recess 234c2 advances to the distal end side in the axial direction beyond the proximal end surface 75d of the connection base end 75c (the second center shaft recess 234c2 is inserted into the connection base end 75c). Thus, the overhanging meat can be pushed (accommodated) into the second middle shaft concave portion 234c2 by the inner peripheral surface 75f of the coupling base end portion 75c.

  Thus, also in this modified embodiment, the middle shaft distal end portion 234 can be appropriately press-fitted into the coupling base end portion 75c. Thereby, the base end surface 75d of the connection member 75 (connection base end part 75c) can be reliably brought into contact with the contact part 231d of the intermediate shaft 230.

  In the above, the present invention has been described with reference to the embodiments and modifications. However, the present invention is not limited to the above-described embodiments and the like, and can be applied with appropriate modifications without departing from the gist thereof. Not too long.

  For example, in the embodiment, until the proximal end surface 75d of the coupling member 75 (the coupling proximal end portion 75c) abuts on the abutting portion 31d of the intermediate shaft 30, the middle shaft distal end portion 34 is press-fitted into the coupling proximal end portion 75c. did. That is, the press-fit completion position is set to a position where the base end surface of the connection base end portion comes into contact with the contact portion of the center shaft.

  However, the present invention is applied to all cases where the “press-fit completion position” is set to a position where the central shaft recess is inserted into the coupling base end. That is, the “press-fit completion position” is set to a position where at least a part of the middle shaft concave portion is disposed in the connection base end portion, and is applied to all cases in which the center shaft front end portion is press-fitted into the connection base end portion.

  Specifically, for example, as shown in FIG. 7, a position where a part of the central shaft recess 34 c is disposed in the connection base end portion 75 c is set as a “press-fit completion position”, and the connection member 75 (connection base The proximal end surface 75d of the end portion 75c) may be completed before the center shaft tip portion 34 is press-fitted before the position where the base end surface 75d contacts the contact portion 31d of the center shaft 30. Even in such a case, as shown in FIG. 7, since the overhanging meat 34g can be pushed (accommodated) into the middle shaft recess 34c, the overhanging meat 34g does not hinder the press-fitting of the middle shaft tip portion 34, so that the middle shaft The distal end portion 34 can be appropriately press-fitted into the coupling base end portion 75c.

20 Ceramic heater 23 Heater base end portion 27 Heating resistor 30, 230 Middle shaft 31d, 231d Contact portion 34, 234 Middle shaft distal end portion 34b Middle shaft fitting portion 34c Middle shaft concave portion 34d Front side edge 34g of middle shaft concave portion Overhang meat 40 Metal shell 75 Connecting member 75b Connecting tip end portion 75c Connecting base end portion 75d Base end surface 75f Inner peripheral surface 80 Heater holding member 100 Glow plug 234b1 First middle shaft fitting portion 234b2 Second middle shaft fitting portion 234c1 First middle shaft recess 234c2 Second middle shaft recess 234d1 Front end side edge 234d2 of the first central shaft recess portion Front end side edge of the second center shaft recess portion

Claims (4)

A cylindrical metal shell having an axial hole extending in the axial direction;
A columnar shape extending in the axial direction, a metal center shaft inserted into the shaft hole of the metal shell,
A ceramic heater having a heating resistor that generates heat when energized;
A metal connecting member that connects a middle shaft distal end portion located on the distal end side in the axial direction of the middle shaft and a heater proximal end portion located on the proximal end side in the axial direction among the heaters. A connecting member having a connecting base end portion that is positioned on the direction base end side and is fitted on the tip end portion of the middle shaft, and a connecting tip end portion that is positioned on the tip end side in the axial direction and connected to the heater base end portion A method of manufacturing a glow plug comprising:
The middle shaft tip is
A middle shaft fitting portion that fits with the coupling base end portion by an interference fit, and a middle shaft fitting portion made of a material having a hardness lower than that of the coupling base end portion, and
It is a middle shaft concave portion provided in the middle shaft tip portion, and has a middle shaft concave portion adjacent to the axial direction proximal end side with respect to the middle shaft fitting portion,
By press-fitting the inner shaft distal end to the connection base end portion, in the outer fitting causes press fitting-fitting process in an interference fit the connecting base end portion to the intermediate shaft fitting portion, the radially outer of the center pole fitting portion A portion that moves toward the axial base end side and protrudes outward in the radial direction by receiving a force from the connecting base end portion to the axial base end side during the press-fitting. Glow that inserts the middle shaft recess into the coupling base end while pushing into the middle shaft recess by the inner peripheral surface of the base end, and press fits the middle shaft tip into the coupling base end until reaching the press-fit completion position. Plug manufacturing method. A method of manufacturing a glow plug according to claim 1,
The central axis is
A contact portion in a form in which a proximal end surface that is an end surface on the axial direction proximal end side of the connection proximal end portion can be contacted to the axial proximal end side with respect to the middle shaft recess;
The press-fitting external fitting step is
The middle shaft recess is inserted into the coupling base end portion, and the middle shaft distal end portion is moved to the coupling base until the base end surface of the coupling base end portion reaches the press-fitting completion position where it abuts on the contact portion of the middle shaft. A method for manufacturing a glow plug that is press-fitted into an end. A cylindrical metal shell having an axial hole extending in the axial direction;
A columnar shape extending in the axial direction, a metal center shaft inserted into the shaft hole of the metal shell,
A ceramic heater having a heating resistor that generates heat when energized;
A metal connecting member that connects a middle shaft distal end portion located on the distal end side in the axial direction of the middle shaft and a heater proximal end portion located on the proximal end side in the axial direction among the heaters. A connecting member having a connecting base end portion that is positioned on the direction base end side and is fitted on the tip end portion of the middle shaft, and a connecting tip end portion that is positioned on the tip end side in the axial direction and connected to the heater base end portion And comprising
The center shaft tip is
A middle shaft fitting portion in which the coupling base end portion is externally fitted with an interference fit, and a middle shaft fitting portion made of a material whose hardness is lower than that of the coupling base end portion; and
A middle shaft recess recessed at the tip of the middle shaft, the middle shaft recess adjacent to the proximal end side in the axial direction with respect to the middle shaft fitting portion,
Of the tip end portions of the center shaft that are press-fitted into the connection base end portion, the center shaft recess is
A part or all of the central shaft concave portion is present on the distal end side in the axial direction from the press-fitting completion position of the proximal end surface of the coupling proximal end portion with respect to the central shaft distal end portion,
A glow plug that accommodates a portion of the middle shaft fitting portion that is radially outer and projecting toward the axial base end in the middle shaft recess . The glow plug according to claim 3,
The middle shaft has an abutting portion in a form in which a proximal end surface that is an end surface on the axial direction proximal end side of the connecting proximal end portions can contact the proximal end side in the axial direction with respect to the concave portion of the intermediate shaft,
The glow plug , wherein the base end surface of the connection base end portion is in contact with the contact portion of the center shaft .

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