JP2016075403A - Glow plug - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress a short circuit between a power supply member and a nearby member having a different potential, and to suppress a decrease in durability of a glow plug.SOLUTION: A glow plug (10) comprises a rod-like heater element (40), a power supply member for supplying electric power to the heater element, a conductive member having a different potential from the power supply member, and an insulator (53) provided between the power supply member and conductive member. The power supply member has a large-diameter part (56), a small-diameter part, and a connection surface (57) connecting an outer side face of the large-diameter part and an outer side face of the small-diameter part together. The insulator is provided over from at least part of the large-diameter part to at least part of the small-diameter part. At least part of a region, overlapping the small-diameter part, of the insulator is arranged more closely to a center axis than the region overlapping the large-diameter part. The power supply member has a first space (80) formed between a first region (61), including at least part of a border (59) between the connection surface and the outer side face of the large-diameter part and extending toward the small-diameter part, and the insulator.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a glow plug.

  Generally, the glow plug includes a heating element provided at the tip in the axial direction and a power supply member (for example, a central shaft) for supplying power to the heating element. Conventionally, a configuration has been proposed in which a part of the surface of the middle shaft is covered with an insulating tube and insulation is ensured between the middle shaft and a member disposed outside the middle shaft and having a potential different from that of the middle shaft (for example, Patent Documents). 1). For example, in a glow plug with a pressure sensor, sensor-related members such as members constituting the pressure sensor and a transmission member for transmitting the displacement to the pressure sensor when the tip of the glow plug is displaced in the axial direction by the combustion pressure. Built into the glow plug. In such a glow plug, it is possible to prevent a short circuit between the insulating tube and the sensor-related member by covering the region near the sensor-related member in the central shaft with the insulating tube.

Japanese Patent Application Laid-Open No. 2014-016142

  The power feeding member generally includes a plurality of portions having different thicknesses. Therefore, regardless of whether or not the pressure sensor as described above is included, the short-circuit between adjacent members having different potentials is suppressed over a wider range where the diameter of the cross-section of the power supply member is different, and the cross-section It has been desired to suppress a decrease in the durability of the glow plug resulting from suppressing a short circuit over a wide range of different diameters.

  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 rod-shaped heater element that generates heat when energized and extends in the axial direction, and a rear end side of the heater element that is formed of a conductive material and extends in the axial direction. A power supply member for supplying power to the heater element, a conductive member disposed on the outer peripheral side of the power supply member and having a potential different from that of the power supply member, and surrounding the power supply member, There is provided a glow plug including a cylindrical insulator provided between a power supply member and the conductive member. In this glow plug, the power supply member includes a large-diameter portion, a small-diameter portion having a cross-sectional diameter perpendicular to the axial direction, which is smaller than the large-diameter portion, an outer surface of the large-diameter portion, and the small-diameter portion. A connecting surface connecting the outer surface of the diameter portion; and the insulator is provided from at least a portion of the large diameter portion to at least a portion of the small diameter portion along the axial direction. The insulator has at least a part of a region overlapping the small diameter portion when projected in a direction perpendicular to the axis, and the large diameter portion when projected in a direction perpendicular to the axis. It is arranged so as to be closer to the central axis of the power supply member than the overlapping region; in the power supply member, the small diameter portion includes at least a part of a boundary between the connection surface and the outer surface of the large diameter portion. Between the first region extending to the side and the insulator, Space is formed.

  According to the glow plug of this embodiment, in the power supply member, the first portion is provided between the insulator and the region including at least a part of the boundary between the connection surface and the outer surface of the large-diameter portion and extending toward the small-diameter portion. A space is formed. Therefore, for example, compared to the case where the power supply member and the insulator are in contact with each other without a gap, the tension applied to the insulator at the boundary is reduced, the damage to the insulator is suppressed, and the power supply member and the conductive material caused by the damage of the insulator are reduced. Occurrence of a short circuit with the sex member can be suppressed. As a result, the durability of the glow plug can be increased.

(2) In the glow plug of the above aspect, the insulator may be made of rubber or resin.
According to the glow plug of this embodiment, the effect of reducing the tension related to the insulator at the boundary between the connection surface and the outer surface of the large-diameter portion can be obtained more significantly, and the vibration isolation effect of the glow plug can be obtained. Can be increased.

(3) The glow plug according to the above aspect further includes an intermediate portion disposed between the large diameter portion and the small diameter portion and having the connection surface as an outer surface; the intermediate portion includes the small diameter portion. A melted portion having a diameter of the cross section larger than a diameter of the cross section of the intermediate portion; a second region including at least a part of the melted portion on a surface of the intermediate portion; and the insulator A second space may be formed between the two.
According to the glow plug of this form, by forming the second space between the intermediate portion of the power supply member and the insulator, it is possible to prevent tension from being applied to the insulator in the melted portion, and insulation caused by the melted portion. Can reduce body damage.

(4) In the glow plug of the above aspect, at least a partial region on the surface of the small-diameter portion, and a third region extending from the boundary between the small-diameter portion and the connection surface to the small-diameter portion side; A third space may be formed between the insulator and the insulator.
According to the glow plug of this form, the tension applied to the insulator at the boundary between the connection surface and the outer surface of the large-diameter portion can be further reduced, so that the effect of suppressing damage to the insulator can be enhanced.

(5) In the glow plug of the above aspect, in the cross section including the axis in the glow plug, the outer contour of the large diameter portion and the connection surface may be connected by a curved portion.
According to the glow plug of this form, it is possible to enhance the effect of suppressing damage to the insulator at the boundary between the connection surface and the outer surface of the large diameter portion.

(6) In the glow plug of the above aspect, the power feeding member includes a middle shaft extending in the axial direction, a rear end portion of the heater element, and a front end portion of the middle shaft, and the heater element and the middle shaft. And at least a part of the large-diameter part is the ring, and the insulator extends from at least a part of the ring along the axial direction. It is good also as providing over at least one part.
According to the glow plug of this embodiment, since the power supply member includes a ring into which the ring is fitted, it is difficult to ensure a distance between the power supply member and the conductive member disposed on the outer peripheral side of the power supply member. Even if it is a case, damage to an insulator can be suppressed, preventing the short circuit between an electric power feeding member and an electroconductive member with an insulator.

(7) The glow plug according to the above aspect further includes a pressure sensor for transmitting a displacement amount by which the heater element is displaced in the axial direction and converting the transmitted displacement amount into an electric signal; May be a transmission member for transmitting a displacement amount of the heater element displaced in the axial direction to the pressure sensor.
According to the glow plug of this embodiment, by providing the transmission member as the conductive member, even if it is difficult to secure the distance between the power supply member and the conductive member, the gap between the power supply member and the conductive member can be reduced. It is possible to suppress damage to the insulator while preventing the short circuit of the insulator with the insulator.

(8) The glow plug according to the above aspect further includes a metal shell that houses a part of the heater element and at least a part of each of the power supply member and the insulator; Is formed with a male screw portion for mounting the glow plug; the outer diameter of the male screw portion may be a nominal diameter of M6 or less.
According to the glow plug of this embodiment, since the outer diameter of the male screw portion is thin and the insulator is required to be formed thinner, the effect of suppressing damage to the insulator can be obtained more remarkably.

  The present invention can be realized in various forms other than those described above. For example, the present invention can be realized in the form of an insulator for a glow plug or a method for manufacturing a glow plug.

It is a cross-sectional schematic diagram showing schematic structure of a glow plug. It is an expanded sectional view of the area | region X in FIG. It is a cross-sectional schematic diagram which expands and shows the structure of the area | region containing the rear-end part of a heater element, and the front-end | tip part of a center axis | shaft. It is process drawing showing the manufacturing method of a glow plug. It is explanatory drawing showing the mode of step S140. It is explanatory drawing which shows the modification of 1st Embodiment. It is explanatory drawing showing the shape of an insulator. It is explanatory drawing showing the shape of an insulator. It is a cross-sectional schematic diagram which expands and shows the structure of the area | region containing the rear-end part of a heater element, and the front-end | tip part of a center axis | shaft. It is a cross-sectional schematic diagram showing schematic structure of a glow plug. It is explanatory drawing showing the shape of an insulator. It is explanatory drawing showing the shape of an insulator.

A. Overall configuration of the first embodiment:
FIG. 1 is a schematic cross-sectional view showing a schematic configuration of a glow plug 10 as a first embodiment of the present invention. FIG. 2 is an enlarged cross-sectional view of a portion indicated as a region X in FIG. The glow plug 10 of the present embodiment is attached to an internal combustion engine such as a diesel engine, and functions as a heat source that assists ignition when starting the internal combustion engine. The glow plug 10 can also be used as a heat source for a diesel particulate filter (DPF) reactivation burner system.

  As shown in FIG. 1, the glow plug 10 includes a housing 20, a heater element 40, a middle shaft 50, and a ring 60 as main components. The glow plug 10 further has a function as a pressure sensor for detecting the pressure (combustion pressure) in the cylinder of the internal combustion engine. The glow plug 10 includes a pressure detection element 35 as a pressure sensor. Further, the glow plug 10 includes a diaphragm 33, a connecting member 70, a transmission sleeve 32, and a sensor fixing member 34 as other necessary components accompanying the pressure sensor. Below, each part is demonstrated based on FIG. In the present specification, the lower side of the glow plug 10 in FIG. 1 in the direction of the axis O is called the “front end side” of the glow plug 10 and the upper side is called the “rear end side”.

  The housing 20 is formed of a conductive material (for example, a metal material such as carbon steel or stainless steel), and includes a metal shell 22 and a cap portion 24. The metal shell 22 is a substantially cylindrical member extending along the axis O. A shaft hole 21 that penetrates through the metal shell 22 along the axis O is formed inside the metal shell 22. The metal shell 22 has a male thread portion 23 (see FIG. 5) having a male thread for engaging with a female thread formed in a plug mounting hole of a cylinder head (not shown) of an internal combustion engine on the outer surface on the rear end side. 1). The cap portion 24 is an annular member disposed on the front end side of the metal shell 22. A tapered portion 25 having a diameter reduced toward the distal end side is provided on the distal end surface of the cap portion 24. The tapered portion 25 is in contact with a seat surface (not shown) provided in the plug mounting hole, thereby ensuring airtightness of the combustion chamber of the engine.

  The heater element 40 is a substantially columnar member extending along the axis O, and includes an insulating portion 41 and a conductive portion 42. The rear end portion side of the heater element 40 is accommodated in the shaft hole 21 at the front end portion of the metal shell 22, and the front end portion side of the heater element 40 passes through the cap portion 24 and the front end of the cap portion 24. Protruding from. The heater element 40 generates heat when electric power is supplied.

  The insulating part 41 is made of an insulating ceramic. In the present embodiment, the insulating part 41 is made of silicon nitride. However, the insulating part 41 is not limited to silicon nitride, and may be formed of other insulating ceramics such as alumina or sialon. The insulating portion 41 is a portion that forms the base of the heater element 40.

  The conductive portion 42 is embedded in the insulating portion 41, has a U-shaped structure that extends in the direction of the axis O and is bent with the tip end as a vertex, and is made of a conductive ceramic that generates resistance when energized. Is formed. In the present embodiment, the conductive portion 42 is made of tungsten carbide and silicon nitride. However, the conductive ceramic constituting the conductive portion 42 is not limited to tungsten carbide and silicon nitride, and may be other conductive ceramics such as molybdenum disilicide or tungsten disilicide, Further ceramics may be included.

  Both end portions of the U-shaped conductive portion 42 are exposed at the rear end surface of the heater element 40. One end portion is a first potential side end portion (plus side end portion) 44, and the other end portion is a second potential side end portion (minus side) having a lower potential than one end portion. End) 43. The conductive portion 42 has a first potential side connection terminal (plus side connection terminal) exposed on the side surface of the heater element 40 in the vicinity of the first potential side end portion (plus side end portion) 44. 46 is formed. In addition, the conductive portion 42 has a heater element 40 in the vicinity of the second potential side end portion (minus side end portion) 43 at a position closer to the tip side than the first potential side connection terminal 46. A second potential side connection terminal (minus side connection terminal) 45 exposed at the side surface is formed. In the present embodiment, the first potential-side connection terminal 46 and the second potential-side connection terminal 45 are formed of the same material as other portions of the conductive portion 42, and a part of the conductive portion 42. It is formed as. However, the first potential side connection terminal 46 and the second potential side connection terminal 45 may be formed separately from other parts of the conductive portion 42.

  The middle shaft 50 has a shape extending along the axis O, and is a rod-shaped member formed of a conductive material (for example, a metal material such as stainless steel such as SUS430, aluminum, copper, and iron). 22 is accommodated in the shaft hole 21 and arranged on the rear end side of the heater element 40. In the present embodiment, the axis of the middle shaft 50 coincides with the axis O of the glow plug 10.

  The ring 60 is a cylindrical member formed of a conductive material (for example, a metal material such as SUS410 or SUS630). The ring 60 is disposed inside the shaft hole 21 of the metal shell 22, and the rear end portion of the heater element 40 and the front end portion of the middle shaft 50 are fitted inside. The rear end portion of the heater element 40 is fitted into the ring 60 by press-fitting, whereby the first potential side connection terminal (plus side connection terminal) 46 exposed on the side surface of the heater element 40 is formed on the inner wall of the ring 60. Touch. As a result, the first potential side connection terminal (plus side connection terminal) 46 of the conductive portion 42 of the heater element 40 is electrically connected to the middle shaft 50 via the ring 60. In the present embodiment, the front end portion of the middle shaft 50 and the rear end portion of the ring 60 are connected by welding (for example, laser welding), but may be connected by press-fitting. In the present embodiment, an insulator 53 is further disposed on the surfaces (side surfaces) of the middle shaft 50 and the ring 60. The insulator 53 will be described in detail later.

  Here, in the ring 60, the rear end of the heater element 40 and the front end of the middle shaft 50 are separated from each other. As a result, the conductive portion 42 of the heater element 40 and the middle shaft 50 are electrically connected only through a path via the first potential side connection terminal (plus side connection terminal) 46. Instead of separating the rear end portion of the heater element 40 and the front end portion of the middle shaft 50, an insulating member may be disposed between them.

  On the side surface of the heater element 40, the first outer cylinder 30 is disposed on the distal end side with respect to the fitting position of the ring 60, and the second outer cylinder 31 is disposed on the distal end side with respect to the first outer cylinder 30. . The first outer cylinder 30 and the second outer cylinder 31 are cylindrical members formed of a conductive material (for example, a metal material such as SUS410 and SUS630), and the first outer cylinder 30 and the second outer cylinder 31 are in the first outer cylinder 30 and the second outer cylinder 31. The heater element 40 is assembled by press-fitting. By press-fitting the heater element 40 into the first outer cylinder 30, the second potential side connection terminal (minus side connection terminal) 45 of the conductive part 42 comes into contact with the inner wall of the first outer cylinder 30, and the conductive part 42 and the first outer cylinder 30 are electrically connected. Note that the second outer cylinder 31 can also be formed of an insulating material. The first outer cylinder 30 and the second outer cylinder 31 and the heater element 40 are brazed after the heater element 40 is inserted into the first outer cylinder 30 and the second outer cylinder 31 without press-fitting. May be assembled.

  A connecting member 70, a transmission sleeve 32, a diaphragm 33, and a sensor fixing member 34 are disposed between the inner wall surface of the housing 20 and the heater element 40, the middle shaft 50 and the ring 60. All of these members are formed of a conductive material. The connecting member 70 can be formed of a metal material such as stainless steel such as SUS630 or a nickel alloy. The transmission sleeve 32, the diaphragm 33, and the sensor fixing member 34 can be formed of a metal material such as carbon steel or stainless steel. In the present embodiment, the transmission sleeve 32 and the diaphragm 33 correspond to a “conductive member” and a “transmission member” in the means for solving the problem.

  The connecting member 70 is a film-like elastic member that connects the heater element 40 and the housing 20 while allowing the heater element 40 to move along the axis O, and is disposed in the cap portion 24. A hole through which the heater element 40 passes is formed in the connecting member 70 at the center. And the inner peripheral part (the front end side of the connection member 70) in which the hole is formed is welded to the rear end part of the second outer cylinder 31 provided on the outer periphery of the heater element 40. The outer peripheral portion (the rear end side of the connecting member 70) is welded to the tip portion of the sensor fixing member 34. The connecting member 70 also serves to secure the airtightness in the housing 20 by connecting the heater element 40 and the housing 20 as described above. The connecting member 70 only needs to allow movement along the axis O of the heater element 40 by elastic deformation, and may be, for example, a bellows.

  The sensor fixing member 34 is a substantially cylindrical member. The sensor fixing member 34 is disposed along the inner wall surface of the shaft hole 21 of the metal shell 22, and a flange-like flange portion 36 protruding outward in the radial direction is formed in the vicinity of the tip of the sensor fixing member 34. The flange portion 36 is welded to the front end surface of the metal shell 22 and the rear end surface of the cap portion 24.

  The transmission sleeve 32 is a substantially cylindrical member, and is disposed radially inward of the sensor fixing member 34 in the shaft hole 21 of the metal shell 22. The distal end of the transmission sleeve 32 is fitted to the outside of the first outer cylinder 30 and is welded to the first outer cylinder 30. Thus, when the heater element 40 is displaced relative to the housing 20 along the direction of the axis O, the transmission sleeve 32 is also displaced together. As a result, the transmission sleeve 32 transmits the displacement of the heater element 40 along the axis O to the rear end side (diaphragm 33). Since the first outer cylinder 30 is formed thicker than the ring 60, the ring 60 and the center shaft 50 fitted in the ring 60 and the transmission sleeve 32 are separated from each other.

  The diaphragm 33 is an annular member. In the center of the diaphragm 33, an opening 37 through which the middle shaft 50 passes is provided. The rear end of the transmission sleeve 32 is welded to the inner peripheral portion of the diaphragm 33. Therefore, when the heater element 40 is displaced along the axis O in response to the pressure of combustion gas (combustion pressure), the displacement amount is transmitted to the diaphragm 33 by the transmission sleeve 32, and the diaphragm 33 is deformed. The rear end of the sensor fixing member 34 is welded to the outer peripheral portion of the diaphragm 33. In the present embodiment, the diaphragm 33 is fixed near the central portion in the housing 20 by the sensor fixing member 34.

  A pressure detection element 35 that detects a pressure by converting a deformation amount (transmitted displacement amount) of the diaphragm 33 into an electric signal is provided on the upper surface (rear end side surface) of the diaphragm 33 (see FIG. 2). ). In the present embodiment, a piezoresistive element is used as the pressure detection element 35. The pressure detection element 35 may be a different type of sensor element other than a piezoresistive element, for example, a piezoelectric element.

  The resistance value of the pressure detecting element 35 (piezoresistive element) according to the present embodiment changes according to the deformation amount of the diaphragm 33. An integrated circuit (not shown) provided at a predetermined portion in the housing 20 is electrically connected to the pressure detection element 35. The integrated circuit detects the combustion pressure of the internal combustion engine by detecting a change in the resistance value of the pressure detection element 35. The integrated circuit outputs an electric signal indicating the combustion pressure thus detected to an external ECU or the like through a wiring (not shown) inserted from the rear end of the housing 20.

  Returning to FIG. 1, a protective cylinder 72 is attached to the rear end side of the housing 20. A terminal fitting 73 that is electrically connected to the middle shaft 50 is disposed inside the protective cylinder 72.

  In the glow plug 10 configured as described above, when power is supplied from the terminal fitting 73, power is supplied to the conductive portion 42 through the central shaft 50, the ring 60, and the first potential side connection terminal 46, and the heater element 40 generates heat. At this time, the connection terminal 45 on the second potential side of the conductive portion 42 is grounded through the first outer cylinder 30, the transmission sleeve 32, the diaphragm 33, the sensor fixing member 34, the housing 20, and the cylinder head of the internal combustion engine. That is, the first outer cylinder 30, the transmission sleeve 32, the diaphragm 33, the sensor fixing member 34, and the housing 20 have a ground potential. In the present specification, the ground potential is not a ground in a strict sense, but is a potential of a member on the side that is arranged on the downstream side of the heater element as a power feeding direction and is grounded through the engine head. Refers to that.

B. Insulator placement:
The insulator 53 is a cylindrical member that is disposed so as to surround the middle shaft 50 and the ring 60 and is made of an insulating material. The insulator 53 is in close contact with a part of the surface of the middle shaft 50 and the ring 60. By providing the insulator 53, the middle shaft 50 and the ring 60, and a member (conductive member) disposed on the outer peripheral side of the middle shaft 50 and the ring 60 and having a different potential from the middle shaft 50 and the ring 60, Insulation between them can be ensured. Below, the arrangement | positioning aspect of the insulator 53 is demonstrated.

  FIG. 3 is a schematic cross-sectional view showing an enlarged configuration of a region including the rear end portion of the heater element 40 and the front end portion of the middle shaft 50. The middle shaft 50 includes an elongated portion 54 having a shape extending in parallel to the direction of the axis O, a fitting portion 52 positioned at the tip of the middle shaft 50, and a diameter expanding portion 55 that is a portion connecting the elongated portion 54 and the fitting portion 52. Prepare. The middle shaft 50 has a substantially circular cross section (hereinafter also referred to as a cross section) perpendicular to the direction of the axis O, and the diameters of the respective cross sections are different from each other. In FIG. 3, an axial range in which the extending portion 54, the fitting portion 52, the enlarged diameter portion 55, and the later-described large diameter portion 56 are arranged is indicated by an arrow extending in the axial direction.

  The elongated portion 54 has the smallest diameter in the cross section, and the diameter of the transverse section is substantially the same in the entire elongated portion 54. The fitting portion 52 is formed to have a larger cross-sectional diameter than the extending portion 54, and the enlarged diameter portion 55 has a shape in which the cross-sectional diameter gradually increases from the extending portion 54 toward the fitting portion 52. The tip of the fitting portion 52 is fitted into the ring 60. The fitting portion 52 is formed such that the diameter of the cross section of the portion to be fitted in the ring 60 is shorter than the diameter of the cross section of the other portion of the fitting portion 52 by a length corresponding to the thickness of the ring 60. . For this reason, when the fitting portion 52 is fitted into the ring 60, the diameter of the entire cross section of the fitting portion 52 and the ring 60 is substantially uniform.

  In the present embodiment, the central shaft 50 and the ring 60 constitute a “power supply member” in a means for solving the problem. The side surfaces of the elongated portion 54, the enlarged diameter portion 55, and the enlarged diameter portion 55 correspond to the “small diameter portion”, “intermediate portion”, and “connection surface” in the means for solving the problem, respectively. Further, the fitting portion 52 and the ring 60 correspond to a “large diameter portion” in the means for solving the problem. In the following description, the fitting portion 52 and the ring 60 are collectively referred to as a large diameter portion 56 and the side surface of the enlarged diameter portion 55 is referred to as a connection surface 57 (see FIG. 3). The difference between the diameter of the cross section of the large diameter portion 56 and the diameter of the small diameter portion (extension portion 54) can be, for example, 0.5 mm or more, and 1.0 mm or more. Is more preferable, and 1.05 mm or more is more preferable. The difference can be 2.7 mm or less, preferably 2.1 mm or less, and more preferably 1.95 mm or less.

  The insulator 53 is continuously provided from the tip of the ring 60 (tip of the large diameter portion 56) to the middle of the middle shaft 50 along the axial direction. A range in the direction of the axis O in which the insulator 53 is provided on the middle shaft 50 and the ring 60 is shown as a range Y in FIG.

  The insulator 53 is in close contact with the large diameter portion 56. Specifically, in this embodiment, the insulator 53 is in close contact with the entire large diameter portion 56. The insulator 53 is in close contact with the extended portion 54 in a region excluding a part of the extended portion 54 including a boundary with the enlarged diameter portion 55. Further, the insulator 53 includes a boundary between the connection surface 57 and the outer surface of the large-diameter portion 56 on the intermediate shaft 50 and extends to the connection surface 57 side, specifically, the enlarged-diameter portion 55 in the extension portion 54. In a region where a part of the region including the boundary with the connection surface 57 is combined, the intermediate shaft 50 is separated from the central shaft 50 without being in close contact therewith. In the following description, the non-contact region described above on the central shaft 50 is referred to as a region 61, and a space formed between the insulator 53 and the region 61 is referred to as a space 80 (see FIG. 3). On the intermediate shaft 50, the region 61 that is separated from the insulator 53 corresponds to a “first region” in the means for solving the problem, and is formed between the intermediate shaft 50 and the insulator 53 in the first region. The space 80 corresponds to a “first space” in the means for solving the problem. In FIG. 3, the boundary between the connection surface 57 and the outer surface of the large-diameter portion 56 is indicated by a one-dot chain line as a boundary 59.

  In the present embodiment, a melted portion 58 is formed at the boundary between the enlarged diameter portion 55 of the central shaft 50 and the elongated portion 54. The melted portion 58 is formed by welding a member including the enlarged diameter portion 55 and a member constituting the elongated portion 54, and has a larger cross-sectional diameter than the elongated portion 54. For this reason, the region 61 including the melting portion 58 and the space 80 formed on the region 61 correspond to a “second region” and a “second space” in the means for solving the problem, respectively.

  Further, in the present embodiment, the region 61 is a partial region on the surface of the extending part 54 and can be said to be an area extending from the boundary between the extending part 54 and the connection surface 57 to the extending part 54 side. Therefore, the region 61 and the space 80 correspond to a “third region” and a “third space” in the means for solving the problem, respectively.

  The insulator 53 is formed of an insulating material, for example, a material selected from a fluorine resin, a polyamide resin, a polyimide resin, a polyester resin, a polyether ether ketone (PEEK) resin, rubber, and a mixture thereof. be able to.

  In the present embodiment, the insulator 53 is fixed on the middle shaft 50 and the ring 60 by utilizing the property that the resin is thermally contracted. That is, the insulator 53 is attached by heat-shrinking the heat-shrinkable tube by applying a heat-shrinkable tube for forming the insulator 53 on the central shaft 50 and the ring 60 and heating. Examples of the material constituting the heat shrinkable tube include polytetrafluoroethylene (PTFE), tetrafluoroethylene / hexafluoropropylene copolymer (FEP), polyvinylidene fluoride (PVDF), and perfluoroalkoxy. Fluorine resin such as fluororesin (PFA), polyester resin such as polyethylene terephthalate (PET), polyamide elastomer resin such as polyvinyl chloride (PVC) resin, polyether block amide copolymer, PEEK resin, silicone resin, Mention may be made of fluorinated silicone rubber.

  The material forming the insulator 53 may have a Young's modulus of 70 GPa or less. By setting it as such a structure, the anti-vibration effect of the glow plug 10 can be improved. Each of the resins and rubbers described above is desirable because it satisfies this numerical range. The Young's modulus of the material forming the insulator 53 is preferably 10 GPa or less, more preferably 7 GPa or less, and even more preferably 5 GPa or less. In addition, there is no restriction | limiting in particular in the lower limit of the Young's modulus of the material which comprises the insulator 53, Usually, it will be 0.005 GPa or more.

C. Production method:
FIG. 4 is a process diagram showing a method for manufacturing the glow plug 10. When manufacturing the glow plug 10, first, the tip of the heater element 40 is inserted from the rear end side of the ring 60 to the tip side, and the heater element 40 is press-fitted into the ring 60 (step S100). As a result, the second potential side connection terminal (plus side connection terminal) 46 of the conductive portion 42 contacts the inner wall of the ring 60, and the conductive portion 42 and the ring 60 are electrically connected. At this time, when the heater element 40 is press-fitted into the ring 60, the close contact state between the positive connection terminal 46 and the inner wall of the ring 60 is enhanced, and the conductive portion 42 and the ring 60 are electrically connected. The resistance is sufficiently suppressed.

  Thereafter, the heater element 40 is press-fitted into the first outer cylinder 30 and the second outer cylinder 31, and the tip of the heater element 40 is projected from the tip of the second outer cylinder 31 (step S110). As a result, the second potential side connection terminal (minus side connection terminal) 45 of the conductive portion 42 is brought into close contact with the inner wall surface of the first outer cylinder 30, and the conductive portion 42 and the first outer cylinder 30 are electrically connected. Is done.

  Next, the member including the fitting portion 52 and the enlarged diameter portion 55 in the middle shaft 50 is fitted into the rear end portion of the ring 60 and welded at a position where the surface of the member contacts the rear end of the ring 60. (Step S120). And the member which consists of a part used as the expansion part 54 in the center shaft 50 is welded to the rear end of the part used as the enlarged diameter part 55 in the said member (step S130). Thereby, the center shaft 50 including the fitting portion 52, the enlarged diameter portion 55, and the elongated portion 54 is completed, and a melted portion 58 is formed between the enlarged diameter portion 55 and the elongated portion 54. In the present embodiment, the heater element 40 is placed in the first outer cylinder 30 and the second outer cylinder 31 before attaching a member constituting the middle shaft 50 to the rear end side of the ring 60 in which the heater element 40 is fitted. Although press-fitted, the order of these steps may be reversed. That is, step S110 may be performed after step S120, or may be performed after step S130.

  Next, the middle shaft 50 integrated with the ring 60 is fitted into a cylindrical member for forming the insulator 53, and a part of the extended portion 54 excluding the vicinity of the boundary with the enlarged diameter portion 55, and The region overlapping the large diameter portion 56 is heated to shrink the cylindrical member (step S140). Thereby, the insulator 53 that is in close contact with the central shaft 50 and the ring 60 at a predetermined location is completed.

  FIG. 5 is an explanatory diagram showing the state of step S140. FIG. 5A shows a state where the middle shaft 50 integrated with the ring 60 is fitted into a cylindrical heat-shrinkable tube 153 serving as the insulator 53. The heat-shrinkable tube 153 prepared in FIG. 5A has an inner diameter that is slightly larger than the diameter of the cross section of the fitting portion 52 of the central shaft 50. The operation of fitting the heat shrinkable tube 153 is performed so that the tip of the heat shrinkable tube 153 overlaps the tip of the ring 60.

  FIG. 5B shows a state where a predetermined portion of the heat shrinkable tube 153 is heated. In FIG. 5 (B), the heating location is indicated by an arrow. The heating temperature can be set to 50 ° C. to 550 ° C., for example, and may be appropriately set according to the type of the heat shrinkable tube 153 used. The heating can be performed by, for example, blowing hot air using a heat gun or the like, or heating using a heater, as long as local heating on a desired location is possible. By heating and contracting a specific portion of the heat-shrinkable tube 153, the ring 60 and the middle shaft 50 and the insulator 53 can be brought into close contact with each other at desired positions of the ring 60 and the middle shaft 50. In the present embodiment, the heat shrinkable tube 153 is shrunk on the large diameter portion 56. Thereby, the heat-shrinkable tube 153 is in close contact with the large-diameter portion 56. Further, the heat-shrinkable tube 153 is shrunk on a region separated from the connection surface 57 in the extending part 54. As a result, the heat-shrinkable tube 153 is in close contact with a region of the elongated portion 54 that is separated from the connection surface 57.

FIG. 5C shows a state where the attachment of the insulator 53 to the ring 60 and the middle shaft 50 is completed. In the insulator 53 of the present embodiment, the diameter of the outer periphery at the portion in close contact with the ring 60 and the intermediate shaft 50 is another member (for example, transmission) disposed on the outer peripheral side of the ring 60 and the intermediate shaft 50 in the glow plug 10. The sleeve 32 and the diaphragm 33) are formed so as to be smaller in diameter than the inner circumference.

  Returning to FIG. 4, after step S <b> 140, the transmission sleeve 32, the diaphragm 33, the sensor fixing member 34, and the main body are further added to the intermediate member including the heater element 40, the middle shaft 50, the ring 60, and the insulator 53. The metal fitting 22 is assembled (step S150). Here, the transmission sleeve 32, the diaphragm 33, and the sensor fixing member 34 are welded at predetermined positions, and the heater element 40 and the like are provided in a through hole that penetrates the transmission sleeve 32 disposed inside in the direction of the axis O. The intermediate member is disposed. Further, the metal shell 22 is disposed on the outer peripheral side of the sensor fixing member 34 (see FIG. 2).

  Thereafter, the flange portion 36 at the tip of the sensor fixing member 34 and the tip of the metal shell 22 are welded, and the heater element 40 (specifically, the first outer cylinder 30) and the tip of the transmission sleeve 32 are welded. . Further, between the rear end portion of the connecting member 70 and the front end portion of the sensor fixing member 34 and between the front end portion of the connecting member 70 and the heater element 40 (specifically, the rear end portion of the second outer cylinder 31). Weld. Further, the cap portion 24 is fitted from the front end side of the heater element 40, and is further press-fitted into the front end portion of the sensor fixing member 34, and the flange portion 36 of the sensor fixing member 34 and the cap portion 24 are welded (see FIG. 2). Thereafter, the protective cylinder 72 is attached to the rear end side of the metal shell 22, and the middle shaft 50 and the terminal metal fitting 73 are connected to complete the glow plug 10 (step S160).

  According to the glow plug of the present embodiment configured as described above, in the middle shaft 50, the region 61 including the boundary (boundary 59) between the connection surface 57 and the outer surface of the large-diameter portion 56 and extending toward the elongated portion 54 is provided. A space 80 (first space) is formed between the insulator 53 and the insulator 53. In the glow plug 10, the insulator 53 is bent radially inward at the boundary 59. In the present embodiment, when the space 80 described above is formed, the insulator 53 is bent from the boundary 59 to the rear end side without forming the space 80 and the insulator 53 is bent. In comparison, the tension applied to the bent portion on the boundary 59 in the insulator 53 can be reduced. If the tension at the bent portion of the insulator 53 is excessive, the insulator 53 may be damaged at the bent portion due to vibration or the like. In this embodiment, damage to the insulator 53 is suppressed by reducing the tension applied to the bent portion, and the middle shaft 50 and the ring 60 (power feeding member), the transmission sleeve 32 and the diaphragm 33 ( The occurrence of a short circuit between the conductive member and the conductive member can be suppressed.

  In particular, when the insulator 53 is made of rubber or resin as described above, at the front end side and the rear end side with the boundary 59 between the outer surface of the large diameter portion 56 and the connection surface 57 interposed therebetween, When the insulator 53 is brought into close contact with the power supply member, the insulator 53 has elasticity, so that tension is easily applied to the insulator 53 on the boundary 59. Therefore, in the case where the insulator 53 is made of rubber or resin, the effect of reducing the tension applied to the insulator 53 can be remarkably obtained by making the shape of the insulator 53 as shown in FIG. it can. Moreover, the effect which improves the vibration proof property of the glow plug 10 is also acquired by comprising the insulator 53 with the rubber | gum or resin which shows the Young's modulus mentioned above.

  In the present embodiment, a space 80 (second space) is formed between the insulator 53 and the region including the melted portion 58 on the surface of the central shaft 50. Therefore, it is possible to prevent the insulator 53 from being tensioned at the melting portion 58 and to suppress damage to the insulator 53 caused by the melting portion 58. In addition, even if it is a case where space (2nd space) is not provided between the 2nd area | region including the at least one part of the fusion | melting part 58 in the surface of an intermediate part, and the insulator 53, 1st space is not provided. The effect by providing can be acquired.

  Further, in the present embodiment, a space 80 (third space) between the insulator 53 and a region extending from the boundary between the extending portion 54 and the connection surface 57 to the extending portion 54 side on the surface of the extending portion 54 of the central shaft 50. Is provided. By providing such a third space, the position where the insulator 53 is in close contact with the elongated portion 54 becomes the rear end side. As a result, in the cross section including the axis O in the glow plug 10, the angle θ (see FIG. 3) formed by the connection surface 57 and the insulator 53 becomes larger, and the tension applied to the insulator 53 at the boundary 59 becomes smaller. Therefore, the effect of suppressing damage to the insulator 53 can be enhanced.

  In addition, according to the present embodiment, since damage to the insulator 53 can be suppressed, it is possible to reduce the size of the glow plug by forming the insulator 53 thinner and making the outer diameter of the glow plug thinner. . That is, by applying the insulator 53 of the present embodiment to a glow plug with a smaller outer diameter, damage to the insulator 53 is suppressed, and as a result, the life of the glow plug is extended or the performance of the glow plug is stabilized. The effect can be obtained remarkably. For example, in a glow plug with a pressure sensor as in the present embodiment, when the outer diameter of the male thread portion 23 of the metal shell 22 is M10 or less in nominal diameter, the effect of suppressing damage to the insulator 53 is remarkable. Can get to. By applying the insulator 53 of this embodiment, the nominal diameter can be set to M9, M8, or M6, for example.

  In addition, in the middle shaft 50, it is desirable to process a corner portion that is a boundary 59 between the outer surface of the large-diameter portion 56 and the connection surface 57 into a curved surface prior to the arrangement of the insulator 53. That is, it is desirable that the outer contour of the fitting portion 52 and the connection surface 57 are connected by a curve in a cross section including the axis O in the middle shaft 50. A corner portion that is a boundary 59 between the outer surface of the large-diameter portion 56 to be processed into a curved surface and the connection surface 57 is shown as a corner portion Z in FIG. With such a configuration, the effect of suppressing the damage of the insulator 53 at the boundary 59 can be enhanced. In the cross section, the outer contour of the fitting portion 52 and the connection surface 57 are connected by a curve when the radius of curvature of the curved portion connecting the outer contour of the fitting portion 52 and the connection surface 57 is R. , 0.005 mm ≦ R ≦ 0.25 mm.

  FIG. 6 is an explanatory diagram illustrating a modified example of the first embodiment. In FIG. 6, only the thick part 56, the enlarged part 55, the extended part 54, and the insulator 53 are shown in order to explain different parts from the glow plug of the first embodiment. In FIG. 6, parts common to the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  FIG. 6A shows a space 81 between the middle shaft 50 and the insulator 53 in a region extending from the part of the boundary 59 between the connection surface 57 and the outer surface of the large diameter portion 56 toward the connection surface 57. Although formed, the region extending from the other part of the boundary 59 toward the connection surface 57 represents a state in which the middle shaft 50 and the insulator 53 are in close contact with each other. Even in such a configuration, an effect of suppressing damage to the insulator 53 at the boundary 59 can be obtained at least in a portion where the space 81 is formed.

  In FIG. 6B, although the space 82 (first space) is formed between the entire connection surface 57 and the insulator 53, the extended portion 54 is in close contact with the insulator 53. This is different from the configuration shown in FIG. That is, the “third space” in the means for solving the problem is not formed. Even in such a configuration, the same effect of reducing the tension applied to the insulator 53 at the boundary 59 can be obtained by providing the first space.

  FIG. 6C is different from the configuration shown in FIG. 3 in that a contact portion 51 where the enlarged diameter portion 55 and the insulator 53 are in contact is formed in the middle of the enlarged diameter portion 55. That is, in FIG. 6C, the “second space” corresponding to the “first space” in the means for solving the problem and the “second region” including the melting part 58 are formed on the “second region”. A space 84 corresponding to “two spaces” is provided separately from each other. In the contact part 51, the enlarged diameter part 55 and the insulator 53 may be in close contact with each other. Even with such a configuration, the same effect as in the first embodiment can be obtained.

  FIG. 6D shows that a part of the insulator 53 that overlaps with the extending part 54 is provided with a region that does not adhere to the extending part 54 along the axial direction up to the rear end of the insulator 53. This is different from the configuration shown in FIG. With such a configuration, in addition to the same effects as those of the first embodiment, the tension applied to the insulator 53 at the boundary 59 is further reduced at the portion that is not in contact with the extending portion 54 over the rear end side in the axial direction. Further, the effect of reducing damage to the insulator 53 can be enhanced.

D. Second embodiment:
FIG. 7 is an explanatory diagram showing the shape of the insulator 53 provided in the glow plug according to the second embodiment. The glow plug of the second embodiment is the same as that of the first embodiment except for the shape of the insulator 53, and the same reference numerals are assigned to the parts common to the first embodiment, and detailed description thereof is omitted. .

  In the second embodiment, only the outer surface of the large-diameter portion 56 is in close contact with the insulator 53 in the power supply member. The power supply member is a region on the rear end side of the boundary 59 between the connection surface 57 and the outer surface of the large-diameter portion 56 in the region overlapping the insulator 53 when projected in a direction perpendicular to the axis O. As a whole, the insulator 53 is not in close contact, and a space 86 is formed between the insulator 53 and the middle shaft 50. With such a configuration, the same effect as in the first embodiment can be obtained, and the tension applied to the insulator 53 at the boundary 59 can be further reduced.

  As shown in FIG. 7, even when the elongated portion 54 and the insulator 53 are not in close contact with each other, at least one of the elongated portion 54 (small diameter portion) is caused in the glow plug 10 by vibration, gravity, or the like. The part may be in contact with the insulator 53. In FIG. 7, a region in the insulator 53 that overlaps the elongated portion 54 (small diameter portion) when projected in a direction perpendicular to the direction of the axis O is a region 65, and the range is indicated by an arrow. In FIG. 7, a region in the insulator 53 that overlaps the large diameter portion 56 when projected in a direction perpendicular to the direction of the axis O is a region 66, and the range is indicated by an arrow. Even when the elongated portion 54 (small diameter portion) and the insulator 53 are not in close contact with each other, the insulator 53 is such that at least a part of the region 65 is located on the central axis of the central shaft 50 (power feeding member) rather than the region 66. It will be arranged to be close.

E. Third embodiment:
FIG. 8 is an explanatory diagram showing the shape of the insulator 53 provided in the glow plug of the third embodiment. The glow plug of the third embodiment is the same as that of the first embodiment except for the shape of the insulator 53, and the same reference numerals are given to portions common to the first embodiment, and detailed description thereof is omitted. .

  In the power supply member of the third embodiment, the rear end side from the boundary between the outer surface of the extending portion 54 and the connection surface 57 in the region overlapping the insulator 53 when projected in the direction perpendicular to the axis O. Only the region on the rear end side is in close contact with the insulator 53 starting from the position separated from the insulator 53. And in this electric power feeding member, the whole area | region of the front end side rather than the area | region which contact | adheres among the area | regions which overlap with the insulator 53 when projected in the direction perpendicular | vertical with respect to the axis line O is the insulator 53. A space 87 is formed between the power feeding member and the insulator 53 without being in close contact. With such a configuration, the same effect as in the first embodiment can be obtained, and the tension applied to the insulator 53 at the boundary 59 can be further reduced. At this time, at least a part of the power supply member may be in contact with the insulator 53 in a region where the power supply member and the insulator 53 are not in close contact with each other.

  In the power supply member, in a region overlapping with the insulator 53 when projected in a direction perpendicular to the axis O, in a part of the region on either the front end side from the boundary 59 or the rear end side from the boundary 59 If the power supply member and the insulator 53 are in close contact with each other, damage to the insulator 53 at the boundary 59 can be suppressed. It is only necessary to secure a region in close contact with the insulator 53 in the power supply member to such an extent that the operation of assembling the power supply member integrated with the insulator 53 into the glow plug can be performed without hindrance.

F. Fourth embodiment:
FIG. 9 is an enlarged schematic cross-sectional view showing a configuration of a region including the rear end portion of the heater element 40 and the front end portion of the central shaft 50 in the glow plug of the fourth embodiment. The fourth embodiment has the same configuration as that of the first embodiment except that the shape of the central shaft 50 is different, and the same reference numerals are given to the parts common to the first embodiment. Detailed description will be omitted.

  In the fourth embodiment, the central shaft 50 does not have the diameter-expanded portion 55, and a step is provided between the fitting portion 52 and the elongated portion 54 so that the diameter of the cross section suddenly changes. In the fourth embodiment, the stepped portion on the surface of the central shaft 50 is the connection surface 57. In the fourth embodiment, on the intermediate shaft 50, between the insulator 63 and the region 63 extending from the connection surface 57 (boundary between the connection surface 57 and the outer surface of the large diameter portion 56) to the extended portion 54 side, A space 88 is formed. In the fourth embodiment, the same effect as that of the first embodiment can be obtained.

G. Fifth embodiment:
FIG. 10 is a schematic cross-sectional view illustrating a schematic configuration of the glow plug 110 according to the fifth embodiment. Unlike the glow plug 10, the glow plug 110 does not have a pressure sensor. In the fifth embodiment, parts common to the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  The glow plug 110 includes main metal shell 22, outer cylinder 130, heater element 40, middle shaft 50, ring 60, and insulator 53 as main components. In the glow plug 110, as in the glow plug 10, the rear end portion of the heater element 40 and the tip end portion of the center shaft 50 are fitted into the ring 60, and the first potential side connection terminal (plus Side connection terminal) 46 is electrically connected to the middle shaft 50 via the ring 60. In the glow plug 110, the heater element 40 is press-fitted into the outer cylinder 130, and the second potential side connection terminal (minus side connection terminal) 45 of the heater element 40 is connected to the metal shell 22 via the outer cylinder 130. Is electrically connected.

  The middle shaft 50 and the ring 60 included in the glow plug 110 have the same shape as in the first embodiment. On the ring 60 and the middle shaft 50, an insulator 53 having the same shape as that of the first embodiment is provided from the tip of the ring 60 to the middle of the extended portion 54 of the middle shaft 50. In the glow plug 110, the conductive member that has a potential different from that of the power supply member (the ring 60 and the middle shaft 50) is the metal shell 22, and the insulator 53 is provided so that the power supply member and the conductive member are separated. Insulation between them can be ensured. Also in the fifth embodiment, the insulator 53 has the same shape as that of the above-described embodiments, so that the insulation at the boundary 59 between the connection surface 57 and the outer surface of the large-diameter portion 56 is achieved. A similar effect of suppressing damage to the body 53 can be obtained.

  In particular, since the glow plug 110 has a simpler internal configuration, the outer diameter of the glow plug is further reduced by making the shape of the insulator 53 the same as that of each of the embodiments described above. The effect which can be reduced in size can be acquired more notably. That is, in the glow plug having a smaller outer diameter, the insulator 53 similar to that of each of the above-described embodiments is applied, thereby suppressing damage to the insulator 53. As a result, the lifetime of the glow plug is increased, or the glow plug is The effect of stabilizing the performance can be remarkably obtained. For example, it is easier to reduce the size of the glow plug such that the outer diameter of the male screw portion 23 of the metal shell 22 is M6 or less in nominal diameter while ensuring the effect of suppressing damage to the insulator 53.

H. Variations:
Modification 1 (deformation of the shape of the power feeding member):
In each of the above embodiments, the power supply member having the large diameter portion on the front end side and the thin diameter portion on the rear end side is used, but a different configuration may be used. That is, in the power supply member, the small diameter portion may be arranged on the tip side of the large diameter portion.

  In each said embodiment, although the shape of the cross section of the electric power feeding member was circular, it is good also as a different structure. For example, the shape of the cross section of the power supply member may be an ellipse or a polygon. In this case, the “diameter of the cross section” in the power supply member is the longest of the diameters passing through the center of gravity in the cross section (the line segment passing through the center of gravity of the cross section and having both end points on the outer periphery of the cross section). Say things.

  In the first to third and fifth embodiments described above, the melting portion 58 is provided between the intermediate portion (the enlarged diameter portion 55) and the elongated portion 54 (the narrow diameter portion) (the rear end in the intermediate portion). A different configuration may be used. For example, it is good also as providing a fusion | melting part in the middle part. If the second space is provided between the second region including the melted portion on the power supply member and the insulator, the same effect as the second space in the embodiment can be obtained. In addition, it is good also as not providing a fusion | melting part in an intermediate part. For example, the middle shaft having the elongated portion 54 and the fitting portion 52 may be integrally formed by a cutting process without a welding process. However, in the case where a member having a different cross-sectional diameter is welded to form a middle shaft having a melted portion, it is desirable that the metal material necessary for forming the middle shaft can be reduced. Further, by welding the members having close (or equal) cross-sectional diameters, the welding operation can be simplified and the energy required for welding can be reduced.

  In any case, if the present invention is applied when an insulator is provided from at least a part of the large diameter part to at least a part of the small diameter part, the outer surface of the large diameter part and the small diameter part A similar effect can be obtained that suppresses damage to the insulator at the boundary between the connection surface that connects the outer surface and the outer surface of the large-diameter portion.

Modification 2 (deformation of insulator):
In the first, second, fourth, and fifth embodiments described above, the insulator 53 is in close contact with the large-diameter portion 56 in the entire circumferential direction of the large-diameter portion 56, but may have a different configuration. . For example, on the outer surface of the large-diameter portion 56, the region extending from the part of the boundary 59 with the connection surface 57 to the front end side in the axial direction may be separated without being in close contact with the insulator 53.

  Moreover, in each said embodiment, although the insulator 53 was provided toward the rear end side from the front-end | tip side of the ring 60, ie, the ring 60 whole was covered, it is good also as a different structure. For example, the insulator 53 may be provided from the middle position in the axial direction of the ring 60 toward the rear end side, and the tip end portion of the ring 60 may not be covered with the insulator 53. Alternatively, the insulator 53 is not provided on the ring 60, and only the fitting portion 52 of the middle shaft 50 is covered with the insulator 53, and the “large diameter portion” of the “power supply member” in the means for solving the problem only by the fitting portion 52. May be configured.

  In each of the above embodiments, the fitting portion 52 of the central shaft 50 and the ring 60 constitute the large-diameter portion 56 of the power supply member, and the diameter of the cross section is substantially constant throughout the large-diameter portion. Good. For example, the ring 60 may be formed to have a larger cross-sectional diameter than the fitting portion 52 of the middle shaft 50. In this case, the ring 60 may be a large-diameter portion in the means for solving the problem, and the fitting portion 52 of the center shaft 50 may be a small-diameter portion in the means for solving the problem. In this case, the fitting portion 52 of the middle shaft 50 can be a large diameter portion in the means for solving the problem, and the elongated portion 54 of the middle shaft 50 can be a small diameter portion in the means for solving the problem.

  FIG. 11 is an explanatory diagram showing the shape of the insulator 53 in the glow plug of such a modification. The glow plug of this modification is the same as that of the first embodiment except for the shape of the power supply member and the insulator 53, and the same reference numerals are assigned to the same parts as those of the first embodiment, and detailed description thereof is omitted. To do.

  In FIG. 11, the fitting portion 52 of the middle shaft 50 has a constant cross-sectional diameter, and the tip of the fitting portion 52 is fitted in the ring 60. That is, the diameter of the cross section of the ring 60 is formed larger than the diameter of the cross section of the fitting portion 52 of the middle shaft 50. In FIG. 11, a portion exposed from the rear end of the ring 60 in the fitting portion 52 is shown as an exposed portion 154.

  In the modification of FIG. 11, a space 180 is formed between the middle shaft 50 and the insulator 53 from the rear end of the ring 60 toward the exposed portion 154 side. Therefore, the ring 60, the exposed portion 154, the rear end surface 157 of the ring 60, and the space 180 respectively correspond to the large diameter portion, the small diameter portion, the connection surface, and the first space in the means for solving the problem. In FIG. 11, the position of the boundary between the outer surface of the ring 60 (large diameter portion) and the rear end surface 157 (connection surface) is shown as a boundary 159.

  Further, in the modification of FIG. 11, in the region of the rear end portion of the exposed portion 154 (region 151), the entire circumferential direction is in close contact with the insulator 53, and the middle shaft 50 extends from the exposed portion 154 toward the extended portion 54 side. A space 80 similar to that of the first embodiment is formed between the insulator 53 and the insulator 53. Therefore, the exposed portion 154, the enlarged diameter portion 55, the elongated portion 54, the connection surface 57, and the space 80 are respectively a large diameter portion, an intermediate portion, a small diameter portion, a connection surface, and a first space in the means for solving the problem. Equivalent to.

Modification 3 (deformation of the arrangement of the large diameter portion):
In each said embodiment, although the large diameter part 56 and the expansion | extension part 54 (thin diameter part) were provided one place in the electric power feeding member, it is good also as a different structure. For example, a plurality of at least one of a large diameter part and a small diameter part may be provided.

  FIG. 12 is an explanatory diagram showing the shape of the insulator 53 in the glow plug of such a modification. In FIG. 12, parts that are the same as those in the first embodiment are given the same reference numerals, and detailed descriptions thereof are omitted.

  In the glow plug of FIG. 12, in the power feeding member, two large diameter portions 156, 256, and one extended portion 54 (small diameter portion) disposed between these large diameter portions 156, 256, Is provided. An enlarged diameter portion 155 is formed between the elongated portion 54 and the large diameter portion 156, and an enlarged diameter portion 255 is formed between the elongated portion 54 and the large diameter portion 256.

  In the modification of FIG. 12, the insulator is provided from the large diameter portion 156 to the middle position of the elongated portion 54 via the enlarged diameter portion 155. Here, the power supply member is in close contact with the insulator 53 in the entire circumferential direction in a region included in the large-diameter portion 156 among regions overlapping the insulator 53 when projected in a direction perpendicular to the axis O. ing. In addition, on the elongated portion 54 of the power supply member, the power supply member and the insulator 53 are in close contact with each other in the entire circumferential direction in a region separated from the enlarged diameter portion 155. In a region including the enlarged diameter portion 155 of the power supply member, a space 80 similar to that of the first embodiment is formed between the power supply member and the insulator 53.

  Even with such a configuration, the same effect as in the first embodiment can be obtained. It should be noted that the shape of the first space provided between the power supply member and the insulator 53 may be different from each other as illustrated in the first embodiment or in the third embodiment. Further, the shape of the insulator 53 is, for example, a shape further extended to the large diameter portion 256 side, and the end portion of the insulator 53 on the side away from the large diameter portion 156 is not located on the elongated portion 54. It is good also as being located on the enlarged diameter part 255. In any configuration, in the range where the insulator 53 is provided, the insulation between the power supply member and the conductive member which is disposed on the outer peripheral side of the power supply member and has a potential different from that of the power supply member is improved. In addition, an effect of suppressing damage to the insulator 53 can be obtained at the boundary between the connection surface and the outer surface of the large diameter portion.

Modification 4 (Modification of insulator formation method):
In each of the above embodiments, the insulator 53 is configured by a heat-shrinkable tube, and the insulator 53 and the power supply member are brought into close contact with each other by heat-shrinking the heat-shrinkable tube. However, different configurations may be employed. For example, the insulator 53 may be formed of a sheet made of an insulating material, and the insulating sheet may be wound around a predetermined position of the power supply member and bonded to the power supply member with an adhesive.

Modification 5 (deformation of a conductive member having a potential different from that of the central shaft):
In the first to fourth embodiments, the conductive member disposed on the outer peripheral side of the power supply member and having a potential different from that of the power supply member is the transmission sleeve 32 and the diaphragm 33. In the fifth embodiment, Although the conductive member is the metal shell 22, a different configuration may be used. The conductive member may be a member that is disposed on the outer peripheral side of the middle shaft 50 and has a potential different from that of the middle shaft 50, and is not limited to a member having a ground potential. For example, in a glow plug including a pressure sensor, the present invention may be applied by using a member that forms a signal line of the pressure sensor as the conductive member.

Modification 6 (Modification of the heater element configuration):
In each of the above embodiments, as the heater element provided in the glow plug, the heater element 40 in which the conductive portion 42 formed of conductive ceramics is embedded in the insulating portion 41 formed of insulating ceramics is used. It is good also as a different structure. For example, it is good also as a structure using the heater heating element exposed to the surface of the insulation part which consists of insulating ceramics. Alternatively, a metal heater in which a heating coil is arranged in a metal sheath tube may be used. In a glow plug including a power supply member having a large diameter portion and a small diameter portion as a power supply member for supplying power to the heater element, when an insulator is provided from at least a part of the large diameter portion to at least a part of the small diameter portion In addition, by applying the present invention, the same effect as the embodiment can be obtained.

  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 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.

DESCRIPTION OF SYMBOLS 10,110 ... Glow plug 20 ... Housing 21 ... Shaft hole 22 ... Main metal fitting 23 ... Male screw part 24 ... Cap part 25 ... Taper part 30 ... 1st outer cylinder 31 ... 2nd outer cylinder 32 ... Transmission sleeve 33 ... Diaphragm 34 ... Sensor fixing member 35 ... Pressure detecting element 36 ... Flange 37 ... Opening 40 ... Heater element 41 ... Insulating part 42 ... Conductive part 45 ... Second potential side connection terminal 46 ... First potential side connection terminal 50 ... Middle shaft 51 ... contact part 52 ... fitting part 53 ... insulator 54 ... extension part 55, 155, 255 ... enlarged diameter part 56, 156, 256 ... large diameter part 57 ... connection surface 58 ... melting part 59, 159 ... boundary 60 ... Rings 61-63, 65, 66 ... area 70 ... connecting member 72 ... protective cylinder 73 ... terminal fittings 80-88, 180 ... space 130 ... outer cylinder 151 ... area 153 ... heat shrinkage Over Bed 154 ... exposed portion 157 ... rear surface

Claims (8)

A rod-shaped heater element that generates heat when energized and extends in the axial direction, and is formed of a conductive material, extends in the axial direction, is disposed on the rear end side of the heater element, and supplies power to the heater element A power supply member, a conductive member that is disposed on the outer peripheral side of the power supply member and has a potential different from that of the power supply member, surrounds the power supply member, and is provided between the power supply member and the conductive member. In a glow plug comprising a cylindrical insulator,
The power supply member includes a large-diameter portion, a small-diameter portion having a cross-sectional diameter perpendicular to the axial direction, smaller than the large-diameter portion, an outer surface of the large-diameter portion, and an outer surface of the small-diameter portion. And a connecting surface that connects
The insulator is provided from at least a part of the large diameter part to at least a part of the small diameter part along the axial direction.
The insulator has at least a part of a region overlapping with the small diameter portion when projected in a direction perpendicular to the axis to overlap with the large diameter portion when projected in a direction perpendicular to the axis. It is arranged closer to the central axis of the power supply member than the region,
In the power supply member, a first space is provided between the insulator and a first region that includes at least a part of a boundary between the connection surface and the outer surface of the large-diameter portion and extends toward the small-diameter portion. A glow plug characterized in that is formed. The glow plug according to claim 1,
The glow plug is characterized in that the insulator is made of rubber or resin. A glow plug according to claim 1 or 2,
It is arranged between the large-diameter portion and the small-diameter portion, and comprises an intermediate portion having the connection surface as an outer surface,
The intermediate portion is formed with a melted portion having a diameter of the transverse section larger than that of the transverse section of the small diameter portion,
A glow plug, wherein a second space is formed between a second region including at least a part of the melted portion on the surface of the intermediate portion and the insulator. The glow plug according to any one of claims 1 to 3, wherein
Between at least a part of the surface of the small-diameter portion, a third region extending from the boundary between the small-diameter portion and the connection surface toward the small-diameter portion, and the insulator, A glow plug characterized in that three spaces are formed. The glow plug according to any one of claims 1 to 4, wherein
The glow plug is characterized in that, in a cross section including the axis line in the glow plug, the outer contour of the large diameter portion and the connection surface are connected by a curved portion. A glow plug according to any one of claims 1 to 5,
The power supply member includes a center shaft extending in the axial direction, a rear end portion of the heater element, and a front end portion of the center shaft, and a ring that electrically connects the heater element and the center shaft. Prepared,
At least a part of the large diameter part is the ring, and the insulator is provided from at least a part of the ring to at least a part of the small diameter part along the axial direction. Glow plug. The glow plug according to claim 6, further comprising:
A displacement sensor for transmitting the displacement amount of the heater element displaced in the axial direction, and a pressure sensor for converting the transmitted displacement amount into an electrical signal;
The glow plug according to claim 1, wherein the conductive member is a transmission member for transmitting a displacement amount of the heater element displaced in the axial direction to the pressure sensor. The glow plug according to any one of claims 1 to 7, further comprising:
A metal shell for housing a part of the heater element and at least a part of each of the power supply member and the insulator;
On the outer surface of the metal shell, a male screw part for mounting the glow plug is formed,
The glow plug is characterized in that an outer diameter of the male screw portion is a nominal diameter of M6 or less.

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