JP6541548B2 - Glow plug - Google Patents

Description

  The present disclosure relates to a glow plug used for an internal combustion engine or the like.

  BACKGROUND ART Conventionally, glow plugs including a heater that generates heat by energization are used to assist the start of an internal combustion engine and the like. As the heater, for example, a so-called sheath heater including a tubular tube whose distal end is closed and a heating coil disposed in the tube may be employed. A technique has been proposed in which the heating coil of such a sheath heater is formed of a metal material whose main component is tungsten.

International Publication No. 2014/206847 International Publication No. 2011/162074

  When a high hardness metal such as tungsten is used as the material of the heating coil, the strength of the heating coil against the thermal expansion of the heating coil at the time of rapid heating of the sheath heater (for example, Mechanical strength is often weak. When the heating coil strength is weak, the heating coil may be damaged when the heating coil is deformed due to thermal expansion of the heating coil (for example, the heating coil is cracked). Also, if the thermal expansion coefficient of the tube (for example, the volumetric expansion coefficient) is higher than the thermal expansion coefficient of the heating coil, the heating coil is pulled by the thermally expanding tube at the time of rapid temperature rise of the sheath heater. May grow. If the heating coil is formed of a hard metal, such elongation may damage the heating coil.

  The present disclosure discloses a technique for suppressing the heating coil from being damaged.

  The present disclosure, for example, discloses the following application example.

Application Example 1
A tubular tube which extends along the direction of the first axis and whose tip is closed;
A helical, tungsten-based heat-generating coil disposed in the tube and having its tip joined to the tip of the tube and extending towards the rear end in the direction of the first axis; ,
A conductive member in which the rear end of the heat generating coil is joined to its front end;
A glow plug comprising
A flat surface including a second axis which is an axis of the middle portion of the heat generating coil for an intermediate portion which is a remaining portion of the heat generating coil except the three turns from the front end and the three turns from the rear end. In the X-ray transmission image, when the X-ray transmission image is obtained by irradiating the X-ray to the cross section of the one side portion divided in the cross section, a plurality of intermediate portions of the heating coil are represented in the X-ray transmission image At least one of the coil segment wires includes a undulating portion,
Glow plug.

  According to this configuration, when the heating coil containing tungsten as a main component is deformed, the undulated portion extends. Thereby, even if the heat generating coil is deformed by thermal expansion, it is possible to suppress the heat generating coil from being damaged. In addition, even if the heat generating coil is pulled by the thermally expanding tube and the heat generating coil is extended, the heat generating coil can be prevented from being damaged.

Application Example 2
The glow plug according to Application Example 1 is,
In the tube, an insulating powder filling the space between the tube and the heating coil is provided.
Glow plug.

  According to this configuration, heat is easily transmitted between the heating coil and the tube as compared to the case where there is a gap between the heating coil and the tube. It can be suppressed that the temperature of the heating coil becomes excessively high. As a result, damage to the heating coil due to heat can be suppressed. Further, since the thermal expansion of the heat generating coil is suppressed, it is possible to suppress the damage of the heat generating coil due to the deformation.

Application Example 3
The glow plug described in Application Example 1 or 2
In the X-ray transmission image, the maximum value of the distance in the direction of the second axis between the coil partial lines adjacent to each other is smaller than the minimum value of the line width in the direction of the second axis of the coil partial line
Glow plug.

  According to this configuration, since the coil partial wires of the heating coil are densely arranged, it is possible to suppress the variation in temperature distribution in the heating coil. Therefore, since it can suppress that the temperature of a part of heating coil becomes high locally locally, it can control that heating coil is damaged.

Application Example 4
The glow plug according to any one of application examples 1 to 3,
In the X-ray transmission image, two straight lines parallel to a line connecting the centers of gravity of the two cross-sectional portions at both ends of one coil partial line and in contact with the contour of the coil partial line When interposing the whole of the one coil partial wire with a straight line, the distance between the two straight lines is equal to or less than twice the minimum value of the line width in the direction of the second axis of the coil partial wire. Is
Glow plug.

  According to this configuration, it is possible to suppress an unintentional contact with the adjacent coil partial wire because the coil partial wire is too wavy.

  The present invention can be realized in various forms, and can be realized, for example, in a sheath heater for a glow plug, a method of manufacturing a sheath heater for a glow plug, a method of manufacturing a glow plug, and the like. .

It is a sectional view showing a glow plug as one embodiment. It is an explanatory view of heating coil 820. It is an explanatory view of a modification of heating coil 820. FIG. 16 is an explanatory view of the deformation of the tube 810 and the deformation of the heating coil 820. FIG. 7 is a cross-sectional view of another embodiment of a glow plug.

A. First embodiment:
A1. Glow plug configuration:
FIG. 1 is a cross-sectional view showing a glow plug according to one embodiment. The glow plug 10 functions as a heat source for assisting the start of an internal combustion engine (not shown) (for example, a diesel engine). The illustrated line AX1 indicates the central axis of the glow plug 10. Hereinafter, the central axis AX1 is also referred to as "first axial line AX1", and the direction parallel to the central axis AX1 is also referred to as "axial direction". The first direction D1 and the second direction D2 in the figure are parallel to the first axis AX1, and the second direction D2 is the direction opposite to the first direction D1. As described later, the heater member 800 that generates heat by energization forms an end portion of the glow plug 10 on the first direction D1 side. Hereinafter, such a first direction D1 side is also referred to as a “front end side”, and a second direction D2 side is also referred to as a “rear end side”. Further, the ends on the first direction D1 side of various members of the glow plug 10 are also referred to as "tips" and the ends on the second direction D2 side are also referred to as "rear ends".

  The glow plug 10 includes a metal shell 20, an inner shaft 30, a heater member 800, an O-ring 50, an insulating member 60, and a terminal member 80. The metal shell 20 is a cylindrical member having a through hole 20x extending along the central axis AX1. Further, the metal shell 20 includes a tool engaging portion 28 formed at an end on the second direction D2 side, an external thread 22 provided on the first direction D1 side with respect to the tool engaging portion 28, and an external thread And a body portion 21 that forms a portion closer to the first direction D1 than the portion 22. The tool engagement portion 28 is a portion engaged with a tool (not shown) when the glow plug 10 is detached. The male screw portion 22 includes a thread for screwing with a female screw of a mounting hole of an internal combustion engine (not shown). The tip end of the body portion 21 is in close contact with the inner surface of the mounting hole of the internal combustion engine to seal the mounting hole. The metal shell 20 is formed of a conductive material (for example, a metal such as carbon steel).

  The through shaft 20 is accommodated in the through hole 20 x of the metal shell 20. The central shaft 30 is a round bar-like member, and is formed of a conductive material (for example, stainless steel). The rear end 319 of the center shaft 30 protrudes from the opening OP2 on the second direction D2 side of the metal shell 20 in the second direction D2.

  In the vicinity of the opening OP2, an O-ring 50 is provided between the outer surface of the center shaft 30 and the inner surface of the through hole 20x of the metal shell 20. The O-ring 50 is formed of an elastic material (eg, rubber). Further, a ring-shaped insulating member 60 is attached to the opening OP2 of the metal shell 20. The insulating member 60 includes a cylindrical portion 62 and a flange portion 68 provided on the second direction D2 side of the cylindrical portion 62. The cylindrical portion 62 is sandwiched between the outer surface of the center shaft 30 and the inner surface of the opening OP2 of the metal shell 20. The insulating member 60 is formed of, for example, a resin. The metal shell 20 supports the center shaft 30 via the members 50 and 60.

  A terminal member 80 is disposed on the rear end side of the metal shell 20 (specifically, on the second direction D2 side of the insulating member 60). The terminal member 80 is a cap-like member and is formed of a conductive material (for example, a metal such as nickel). The flange portion 68 of the insulating member 60 is sandwiched between the terminal member 80 and the metal shell 20. The rear end 319 of the center shaft 30 is inserted into the terminal member 80. The terminal member 80 is fixed to the rear end 319 by the terminal member 80 being crimped. Thus, the terminal member 80 is electrically connected to the rear end 319.

  The heater member 800 is press-fitted into the end portion of the metal shell 20 (specifically, the opening OP1 on the first direction D1 side). In the present embodiment, the heater member 800 is a so-called sheath heater, and generates heat by energization (hereinafter also referred to as “sheath heater 800”). A part of the heater member 800 on the second direction D2 side is press-fit into the through hole 20x from the opening OP1 of the through hole 20x. The heater member 800 includes a helical heating coil 820, a helical rear end coil 830, an insulating powder 840, a ring-shaped packing 850, and a tube 810 for housing those members 820, 830, 840, and 850. ,including. The tube 810 is a member in which a conductive material (for example, a nickel alloy such as NCF 601 defined by Japanese JIS standard or DIN 2.4 633 (alloy 602) defined by DIN standard of Germany) is formed in a tubular shape. The tube 810 is arranged to extend along the central axis AX1. The tip of the tube 810 (referred to as “tip 811”) is closed, and the rear end of the tube 810 (referred to as “back 819”) forms an opening.

  The distal end 821 of the heating coil 820 is electrically connected to the distal end portion 811 of the tube 810. The front end 831 of the rear end coil 830 is electrically connected to the rear end 829 of the heat generating coil 820. These connections are, for example, welding or brazing.

  In the present embodiment, the heating coil 820 is formed of tungsten. The rear end coil 830 is formed of an alloy of iron, chromium and aluminum (Fe-Cr-Al).

  The distal end 321 of the center shaft 30 is inserted into the tube 810 from the opening on the second direction D2 side of the tube 810. The front end 321 of the center shaft 30 is electrically connected to the rear end 839 of the rear end coil 830. For example, in a state where the coil wire of the rear end coil 830 is wound around the front end 321 of the middle shaft 30, the wound portion and the middle shaft 30 are joined by welding. The rear end 839 of the rear end coil 830 is joined to the center shaft 30 via a welding portion 837 (a portion melted at the time of welding and including at least one of the component of the rear end coil 830 and the component of the center shaft 30). ing. The packing 850 is a member in which an electrically insulating material (for example, a rubber such as fluorine rubber) is formed in a ring shape. The packing 850 is disposed between the rear end 819 of the tube 810 and the center shaft 30. Insulating powder 840 is a powder of an electrically insulating material (eg, magnesium oxide, alumina, etc.), and is filled inside tube 810. The packing 850 and the insulating powder 840 electrically insulate between the tube 810 and the central shaft 30 all around the central axis AX1. Also, the insulating powder 840 suppresses an unintended electrical short between the heating coil 820, the rear end coil 830, the middle shaft 30 and the tube 810.

A2. Configuration of heating coil 820:
FIG. 2 is an explanatory view of the heating coil 820. As shown in FIG. FIG. 2A is a schematic view of the heater member 800 viewed in a direction perpendicular to the first axis AX1. In the figure, the appearance of the heat generating coil 820, the appearance of a portion including the leading end 831 of the rear end coil 830, the appearance of the welds 823 and 824, and the cross section of a portion including the tip 811 of the tube 810 (Cross-section by a flat surface including the first axis AX1) is shown. Illustration of the insulating powder 840 is omitted. A rear end 829 of the heat generating coil 820 and a front end 831 of the rear end coil 830 are a welded portion 823 (a portion melted at the time of welding and including at least one of a component of the heat generating coil 820 and a component of the rear end coil 830) It is joined through. The tip 821 of the heat generating coil 820 and the tip 811 of the tube 810 are joined via a welded portion 824 (a portion melted at the time of welding and including at least one of a component of the heat generating coil 820 and a component of the tube 810) It is done.

  The second axis AX2 in the figure is the axis (that is, the central axis) of the heating coil 820. The spiral shape of the heat generating coil 820 is formed around the second axis AX2. As illustrated, the second axis AX2 may not coincide with the first axis AX1. Such axial misalignment may occur due to manufacturing errors and the like. Also, as described later, such an axial deviation may be intentionally provided. In any case, even if the second axis AX2 does not strictly coincide with the first axis AX1, the second axis AX2 is approximately the same as the first axis AX1. For example, an angle formed by a direction parallel to the first axis AX1 toward the tip and a direction parallel to the second axis AX2 toward the tip is 30 degrees or less. It can be said that the heating coil 820 extends from the front end side in the direction of the first axis AX1 toward the rear end side.

  FIG. 2B is an X-ray transmission image of the heat generating coil 820. This X-ray transmission image is represented by X-rays transmitted through the heating coil 820 when the X-ray is irradiated to the cross section of one side of the heating coil 820 divided into flat cross sections including the second axis AX2. Image. Such an X-ray transmission image represents a projection view in the case where a portion on one side of the heating coil 820 divided in the cross section is projected along a direction perpendicular to the cross section on a projection plane parallel to the cross section. ing. In FIG. 2B, a half portion on the back side of the paper surface of the heating coil 820 of FIG. 2A is shown. In the drawing, a plurality of coil part lines CL separated from one another are shown along the second axis AX2. One coil partial line CL indicates a portion corresponding to approximately half a circumference of a coil wire which goes around the second axis AX2. The hatched area CS in the drawing is a cross section of the coil wire of the heating coil 820 superimposed on the X-ray transmission image. The cross section CS on the X-ray transmission image is an image representing the cross section of the heating coil 820 divided for acquisition of the X-ray transmission image, and the cross section of the coil wire at the cross section corresponds to the corresponding coil partial line of the X-ray transmission image It is identified by overlaying the X-ray transmission image so as to overlap the end of the CL. Each coil portion line CL extends across the second axis AX2 from the cross section CS on one side (upper side in the figure) to the cross section CS on the other side (lower side in the figure) as viewed from the second axis AX2. There is. Thus, one coil portion line CL is configured to connect two cross sections CS separated from each other.

  Further, as shown in FIG. 2A, in the first portion 822 including the tip 821 of the heating coil 820, the coil diameter and the coil pitch are parallel to the second axis AX2 for connection with the tube 810. It can change greatly depending on the position of the direction. Similarly, in the second portion 828 including the back end 829 of the heating coil 820, the coil diameter and the coil pitch are in accordance with the position in the direction parallel to the second axis AX2 for connection with the back end coil 830. Can change significantly. The coil diameter and the coil pitch are approximately constant in the remaining middle portion 820m except for the both end portions 822, 828. In the present embodiment, as the first portion 822, a portion corresponding to three turns from the tip 821 of the heat generating coil 820 is adopted. As a portion corresponding to three turns, a portion that makes three rounds around the second axis AX2 may be employed regardless of the distance from the second axis AX2 (that is, the coil diameter). Further, as the second portion 828, a portion corresponding to three turns from the rear end 829 of the heat generating coil 820 is adopted. In the X-ray transmission image of FIG. 2B, the three coil partial lines CL at the tip end side correspond to the first portion 822 and the three coil partial lines CL at the rear end side are the second portion 828 It corresponds to Thus, in the X-ray transmission image, the remainder of the plurality of coil partial lines CL excluding the three coil partial lines CL at the tip end side and the three coil partial lines CL at the rear end side is an intermediate portion It can be used as a coil partial line CL corresponding to 820 m.

  FIG. 2 (C) is an enlarged view of one coil partial line CL in the X-ray transmission image of FIG. 2 (B). The coil partial line CL is a coil partial line CL included in the middle portion 820 m. The first cross section CS1 and the second cross section CS2 in the figure are two cross sections CS located at both ends of one coil partial line CL. Two virtual straight lines La and Lb are shown in the figure. These imaginary straight lines La and Lb are straight lines in contact with both the contour of the first cross section CS1 and the contour of the second cross section CS2, and are two straight lines sandwiching the two cross sections CS1 and CS2 .

  As illustrated, the coil portion line CL is curved so as to extend out of the region sandwiched by these imaginary straight lines La and Lb. As described above, the coil part line CL includes an undulating portion (that is, a portion curved so as to protrude outside the region sandwiched by the imaginary straight lines La and Lb) as compared with the straight line connecting the cross sections CS1 and CS2. . As described above, in the present embodiment, the coil wire forming the heating coil 820 further undulates while circulating around the first axis AX1. In the present embodiment, all of the plurality of coil partial lines CL in the middle portion 820 m include the undulating portion.

  The above-mentioned second axis AX2 of the heating coil 820 including the undulated portion is specified using the middle portion 820m. For example, the middle portion 820m is projected along a direction parallel to the temporary axis on a projection plane perpendicular to the temporary axis passing through the inner peripheral side of the middle portion 820m. On the projection plane, the middle portion 820m is represented by a ring-shaped region. The direction of the provisional axis line that minimizes the area of the projected middle portion 820m may be adopted as the direction of the second axis line AX2. Then, the barycentric position of the ring-shaped area representing the projected middle portion 820m may be adopted as the position of the second axis AX2. The position of the center of gravity is the position of the center of gravity when it is assumed that the mass is uniformly distributed in the ring-shaped area. Such a barycentric position is located in the hole on the inner peripheral side of the ring-shaped area.

  FIG. 3 is an explanatory view of a modification of the heating coil 820. As shown in FIG. The heating coil 820 can be deformed by the thermal expansion of the heating coil 820 at the time of rapid temperature rise by energization. FIG. 3A shows how a coil partial line CL of the X-ray transmission image of the embodiment is deformed. The left part shows before deformation, and the right part shows after deformation. A force F may be applied to the coil part line CL to stretch the coil part line CL due to the thermal expansion of the other part of the heat generating coil 820. As described in FIG. 2C, in the embodiment, the coil partial line CL is undulated. Therefore, the coil part line CL can be extended by deforming the coiled part line CL so as to approach a straight line.

  FIG. 3B shows how the coil partial line CLr of the same X-ray transmission image of the heating coil of the reference example is deformed. The left part shows before deformation, and the right part shows after deformation. The heating coil of the reference example is not undulated as in the embodiment described with reference to FIG. 2C, and the coil partial line CLr of the X-ray transmission image is a straight line connecting the cross sections CS1 and CS2. Thus, in the reference example, since the coil partial line CLr is linear, the coil partial line CLr that receives the force F can not extend. As a result, as shown in the right part of FIG. 3B, the crack CR may occur in the coil partial line CLr (that is, the coil line). In particular, when the material of the heating coil contains a metal having high hardness such as tungsten, the mechanical strength of the coil wire is often weak. In such a case, since the coil partial line CLr can not be flexibly deformed according to the force F, the crack CR easily occurs. In the embodiment of FIG. 3A, the generation of such a crack CR can be suppressed by the extension of the undulated portion of the coil partial line CL.

  FIG. 4 is an explanatory view of the deformation of the tube 810 and the deformation of the heating coil 820. FIG. 4 shows a schematic view of the same heater member 800 as FIG. 2 (A). In addition to the heating coil 820, the tube 810 may also be deformed by thermal expansion during rapid temperature rise. For example, as shown by a dotted line in FIG. 4, the tube 810 extends in the first direction D1 substantially parallel to the first axis AX1 when viewed from the metal shell 20 (not shown). Here, when the thermal expansion coefficient of the tube 810 is larger than the thermal expansion coefficient of the heating coil 820, the heating coil 820 is pulled in the first direction D1 by the extending tube 810. For example, the coefficient of thermal expansion of nickel alloys such as NCF601 and DIN 2.4 633 (alloy 602) is greater than the coefficient of thermal expansion of tungsten. Thus, if the tube 810 is formed of such a nickel alloy, the thermal expansion of the tube 810 causes the heating coil 820 to be pulled along the first axis AX1.

  In the embodiment, as described with reference to FIG. 3A and the like, the coil partial line CL that is wound can be deformed so as to extend. Therefore, when the heat generating coil 820 is pulled in the first direction D1 by the tube 810, in addition to the expansion of the pitch of the spiral heat generating coil 820, the undulating portion of the coil wire can be expanded. Thus, the heating coil 820 can be extended without being damaged.

  In the reference example described in FIG. 3B, since the coil partial line CLr is not undulated, the coil partial line CLr can not extend like the coil partial line CL of the embodiment. Therefore, when the heating coil of the reference example is pulled in the first direction D1 by the tube 810, the pitch of the spiral heating coil 820 can be expanded, but the coil partial line CLr (that is, the coil wire) is not undulated. I can not stretch. Therefore, the crack CR as described in FIG. 3B is likely to occur. In the embodiment of FIG. 3 (A), such a crack CR can be suppressed by extending the waved portion of the coil partial line CL.

A3. Production method:
The glow plug 10 provided with the above-mentioned heating coil 820 can be manufactured by various methods. When producing the sheath heater 800, the manufacturer produces, for example, the tube 810 by processing a metal plate into a tubular shape. As a method of producing the tube 810 from a metal plate, there are, for example, a method of rounding a metal plate and performing arc welding, a method of deep drawing a metal plate, and the like. Further, the manufacturer performs welding of the heat generating coil 820 and the rear end coil 830 and welding of the rear end coil 830 and the middle shaft 30 to integrate the heating coil 820, the rear end coil 830 and the middle shaft 30. Do. The manufacturer places the rear end coil 830 and the heating coil 820 integrated with the center shaft 30 inside the tube 810. Thereafter, the manufacturer welds the distal end portion 811 of the tube 810 and the heating coil 820. For example, the distal end portion 811 of the tube 810 and the distal end 821 of the heating coil 820 are joined by arc welding from the outside of the tube 810. Thereafter, the manufacturer fills the inside of the tube 810 with the insulating powder 840. Thereby, a sheath heater 800 of a temporary shape is created.

  After filling the tube 810 with the insulating powder 840 and inserting the packing 850 on the rear end side of the tube 810, the manufacturer swaged against the sheath heater 800 using a swaging apparatus equipped with a chuck and a rotating die. The diameter of the sheath heater 800 is adjusted by performing the ging process. In the swaging process, the manufacturer grips the center shaft 30 fixed to the sheath heater 800 by the chuck and moves the sheath heater 800 along the central axis AX1 by moving the chuck, and around the tube 810 by the rotary die. Make a blow to Thus, the diameter of the sheath heater 800 is adjusted to a predetermined diameter. Thereby, the sheath heater 800 is completed.

  The manufacturer assembles the glow plug 10 using the completed sheath heater 800. Specifically, the manufacturer fixes the sheath heater 800 to which the center shaft 30 is fixed by press-fitting the through hole 20 x of the metal shell 20. Then, the manufacturer fits the O-ring 50 and the insulating member 60 into the opening OP2 on the rear end side of the metal shell 20. Then, the manufacturer fixes the terminal member 80 to the rear end 319 of the center shaft 30 by caulking the terminal member 80. Thus, the glow plug 10 is completed.

  In addition, various methods can be adopted as a method of manufacturing the heating coil 820 including the undulating portion described in FIG. 2 (B) and FIG. 2 (C). For example, in the above-described swaging of the sheath heater 800, the second axis AX2 of the heating coil 820, 820a may be intentionally shifted from the central axis AX1 of the tube 810. That is, a method may be employed in which the heating coil 820 is disposed at a position in the tube 810 such that the second axis AX2 deviates from the central axis AX1. When the tube 810 is struck, force is also applied to the heating coil 820 through the insulating powder 840. Thereby, the heating coil 820 is also deformed. Here, when the second axis AX2 of the heat generating coil 820 is deviated from the central axis AX1 of the tube 810, the distance between the heat generating coil 820 and the inner circumferential surface of the tube 810 is not uniform. When an impact is applied to the portion of the outer surface of the tube 810 where the gap is small, a strong force is applied to the portion of the heat generating coil 820 close to the impact position. When an impact is applied to the portion of the outer surface of the tube 810 where the gap is large, a weak force is applied to the portion of the heating coil 820 near the impact position. Thus, the strength of the force applied to the heating coil 820 is not uniform, and varies depending on the position on the heating coil 820. Therefore, the heat generating coil 820 deforms in a distorted manner. As a result, a heating coil 820 including the undulated portion described in FIG. 2B and FIG. 2C is formed.

  In addition, various methods can be adopted as a method of arranging the heating coil at a position where the second axis AX2 deviates from the first axis AX1. For example, in the embodiment of FIG. 2A, the second axis AX2 may be removed from the first axis AX1 by adjusting the welding position of the rear end 829 of the heat generating coil 820 and the front end 831 of the rear end coil 830. it can. Further, in the embodiment of FIG. 5, the second axis AX2 can be removed from the first axis AX1 by adjusting the welding position of the rear end 829a of the heat generating coil 820a and the center shaft 30.

  In addition, regardless of whether or not the second axis AX2 coincides with the first axis AX1, a plurality of hitting positions unevenly arranged on the outer surface of the tube 810 may be hit. According to this, since the heating coil 820 receives force at a plurality of unevenly arranged positions, it deforms into a distorted shape. As a result, a heating coil 820 including the undulated portion described in FIG. 2B and FIG. 2C is formed.

  Also, instead of the method using swaging of the sheath heater 800, another method may be adopted. For example, the heating coil 820 including the undulated portion may be formed by spirally winding a wire processed into a wavy shape in advance.

  In addition, as a manufacturing method of the glow plug 10, it may replace with the method mentioned above and may employ | adopt another method.

  As described above, in the present embodiment, in the X-ray transmission image described with reference to FIG. 2B, the plurality of coil partial lines CL representing the middle portion 820 m of the heating coil 820 include the undulated portions (see FIG. 2 (C)). Therefore, as described with reference to FIG. 3A, FIG. 4 and the like, when the heating coil 820 is deformed, the undulated portion extends. Even if the heat generating coil 820 is deformed by thermal expansion, damage to the heat generating coil 820 can be suppressed. Further, even if the heat generating coil 820 is pulled by the thermally expanding tube 810 and the heat generating coil 820 is extended, damage to the heat generating coil 820 can be suppressed.

  Further, since the undulated portion suppresses the damage to the heat generating coil 820, a material of high hardness such as tungsten can be adopted as the material of the heat generating coil 820. The melting point of tungsten is approximately 3400 degrees Celsius, which is higher than other metals, so the heating coil can be heated to a high temperature. Therefore, the high specified temperature of the sheath heater (ie, the temperature after the temperature rise) can be realized.

  Further, as described in FIG. 1, the insulating powder 840 is disposed in the tube 810, and the insulating powder 840 fills the space between the tube 810 and the heating coil 820. Therefore, heat is more easily transferred between the heat generating coil 820 and the tube 810 as compared with the case where there is a gap between the heat generating coil 820 and the tube 810. Accordingly, it is possible to suppress that the temperature of the heating coil 820 becomes excessively high with respect to the specified temperature of the sheath heater 800 after the temperature rise (the same as the temperature of the tube 810). As a result, damage to the heating coil 820 due to heat can be suppressed. Moreover, since the thermal expansion of the heat generating coil 820 is suppressed, damage to the heat generating coil 820 due to deformation can be suppressed.

  Further, in FIG. 2B, the maximum distance Dg and the minimum line width Dc are shown. The maximum distance Dg is, in the X-ray transmission image of FIG. 2B, in the direction of the second axis AX2 between two adjacent coil partial lines CL among the plurality of coil partial lines CL representing the middle portion 820 m. It is the maximum value of the interval. The minimum line width Dc is the minimum value of the line widths in the direction of the second axis AX2 of the plurality of coil partial lines CL representing the middle portion 820m. In the present embodiment, Dg <Dc. That is, the gap between the plurality of coil partial lines CL is smaller than the line width of the coil partial line CL. As described above, since the coil partial lines CL (i.e., coil lines) of the heating coil 820 are densely arranged, variations in temperature distribution in the heating coil 820 can be suppressed. Therefore, it is possible to suppress that the temperature of a part of the heat generating coil 820 becomes excessively high locally, so it is possible to suppress the heat generating coil 820 from being damaged by the local heat or the local deformation. In the present embodiment, although Dg <Dc, it may be Dg よ い Dc.

  FIG. 2D is an explanatory view of the magnitude of the undulation of the coil partial line CL. In the figure, the same one coil partial line CL as that in FIG. 2C is shown. Hereinafter, this one coil partial line CL is also referred to as a target coil partial line CL. The first center of gravity Gc1 in the drawing is the center of gravity of the first cross section CS1. The first center of gravity Gc1 is the position of the center of gravity when it is assumed that the mass is uniformly distributed in the first cross section CS1. The second gravity center Gc2 is the gravity center of the second cross section CS2. The virtual line segment Lgc is a virtual line segment connecting the centers of gravity Gc1 and Gc2. The centers of gravity Gc1 and Gc2 in the X-ray transmission image can be identified, for example, using partial contour lines PL1 and PL2 (FIG. 2D) at the end of the coil partial line CL in the X-ray transmission image. Partial contour lines PL1 and PL2 are portions of the contour line of coil partial line CL corresponding to the end of coil partial line CL. Such partial contour lines PL1, PL2 correspond to part of the contours of the cross sections CS1, CS2. Therefore, the cross sections CS1 and CS2 can be specified by extending the arcs of the partial contour lines PL1 and PL2 to make them circular. Here, the cross-sectional shape of the coil wire can be easily identified, for example, by cutting the coil wire, and is usually a circular shape having the same diameter as the outer diameter of the coil wire. Also from this point, the circular shape obtained corresponds to the cross sections CS1 and CS2 by adopting the above-mentioned method. Then, the barycentric position (for example, the position of the center of the circular shape) of the obtained first cross section CS1 corresponds to the first barycenter Gc1. The second cross section CS2 and the second center of gravity Gc2 are similarly specified. As described above, in the X-ray transmission image, the centers of gravity Gc1 and Gc2 can be easily specified even if the boundary between the portion corresponding to the cross section CS1 or CS2 of the coil partial line CL and the remaining portion is not clear. it can. Alternatively, the centers of gravity Gc1 and Gc2 may be specified by superimposing an image representing the cross section of the heating coil 820 divided for obtaining an X-ray transmission image on the X-ray transmission image. Also in this case, the position of the image representing the cross section of the heat generating coil 820 with respect to the X-ray transmission image may be determined at a position where the outline of the cross section of the coil wire overlaps the partial outline PL1 and PL2 of the X-ray transmission image.

  Two virtual straight lines L1 and L2 in the figure are straight lines parallel to the virtual line segment Lgc and in contact with the contour of the target coil partial line CL, and are straight lines sandwiching the entire target coil partial line CL. The distance dL is a distance between these two virtual straight lines L1 and L2, and is a distance between the virtual straight lines L1 and L2 in a direction perpendicular to the two virtual straight lines L1 and L2. That is, when the distance dL is large, it can be said that the undulation of the target coil partial line CL is large.

  A coil part line CL having a large distance dL, that is, a coil part line CL having a large undulation, is likely to contact the adjacent coil part line CL. In order to suppress such an unintended short circuit, it is preferable that the distance dL be small. In the present embodiment, each interval dL (i.e., the maximum interval dL) of the plurality of coil partial lines CL representing the middle portion 820m is equal to or less than twice the minimum line width Dc described in FIG. This can suppress an unintended short circuit. In the present embodiment, the maximum distance dL is equal to or less than twice the minimum line width Dc, but the middle portion 820m may be provided with a portion where the distance dL exceeds twice the minimum line width Dc. .

  Further, in order to suppress the damage to the heating coil 820, it is preferable that the undulation of the coil partial line CL, that is, the distance dL be large. In the present embodiment, each interval dL (i.e., the minimum interval dL) of the plurality of coil partial lines CL representing the middle portion 820m is 1.1 or more times the minimum line width Dc. Thereby, damage to the heating coil 820 can be suppressed by extending the undulated portion. In the present embodiment, the minimum distance dL is 1.1 times or more of the minimum line width Dc, but the minimum distance dL in the middle portion 820 m may be less than 1.1 times the minimum line width Dc. .

B. Second embodiment:
FIG. 5 is a cross sectional view showing another embodiment of the glow plug. Only a portion of the glow plug 10a including the sheath heater 800a is shown in the figure. The difference with the embodiment of FIG. 1 is that the rear end coil 830 is omitted, and instead, a tungsten heating coil 820a formed and extended is provided. The configuration of the other parts of the glow plug 10a according to the second embodiment is the same as the configuration of the corresponding parts of the glow plug 10 according to the first embodiment (the same reference numerals are given to the same elements and the description is omitted To do).

  The tip 821 a of the heat generating coil 820 a is joined to the tip 811 of the tube 810. The rear end 829 a of the heat generating coil 820 a is joined to the front end 321 of the center shaft 30. These joints are, for example, welding. In the present embodiment, the tip 821a of the heat generating coil 820a and the tip 811 of the tube 810 are a welded portion 824a (a portion melted at the time of welding and including at least one of the component of the heat coil 820a and the component of the tube 810). It is joined via). Further, regarding the rear end 829a of the heating coil 820a, in a state where the coil wire of the heating coil 820a is wound around the front end 321 of the middle shaft 30, the wound portion and the middle shaft 30 are joined by welding. The rear end 829a of the heat generating coil 820a is joined to the center shaft 30 via a welding portion 827a (a portion melted at the time of welding and including at least one of the component of the heat generating coil 820a and the component of the center shaft 30). .

  The middle portion 820am in the figure is the remaining portion of the heating coil 820a excluding the portion 822a corresponding to three turns from the leading end 821a and the portion 828a corresponding to three turns from the rear end 829a. Although illustration is omitted, also in the second embodiment, in the X-ray transmission image obtained by the same method as in FIG. 2B of the heating coil 820a, each of the plurality of coil part lines representing the middle portion 820am of the heating coil 820a. However, it contains the part where it was undulating. Therefore, as in the first embodiment of FIG. 3A and FIG. 4, when the heat generating coil 820 a is deformed, the undulating portion is extended, so that the heat generating coil 820 a can be prevented from being damaged.

  Further, as shown in FIG. 5, the insulating powder 840 is disposed in the tube 810, and the insulating powder 840 fills the space between the tube 810 and the heating coil 820a. Therefore, as in the first embodiment, heat is easily transferred between the heating coil 820 a and the tube 810. Thus, it is possible to suppress the temperature of the heat generating coil 820a from becoming excessively high with respect to the specified temperature of the sheath heater 800 after the temperature rise. As a result, damage to the heating coil 820a due to heat can be suppressed. Further, since the thermal expansion of the heating coil 820a is suppressed, it is possible to suppress the damage of the heating coil 820a due to the deformation.

  Further, also in the present embodiment, the maximum interval Dg described in FIG. 2B is less than the minimum line width Dc. As described above, since the coil partial wires (that is, coil wires) of the heating coil 820 a are densely arranged, it is possible to suppress the variation in temperature distribution in the heating coil 820. Therefore, it is possible to suppress that the temperature of a part of the heat generating coil 820 becomes excessively high locally, so it is possible to suppress the heat generating coil 820 from being damaged by the local heat or the local deformation.

  Also in the present embodiment, as described in FIG. 2D, the maximum distance dL of the plurality of coil partial lines representing the middle portion 820am of the X-ray transmission image is not more than twice the minimum line width Dc. Is preferred. The minimum distance dL is preferably 1.1 or more times the minimum line width Dc.

C. Modification:
(1) The material of the heat generating coil (for example, the heat generating coil 820 in FIG. 1 and the heat generating coil 820 a in FIG. 5) is not limited to tungsten, and various materials containing tungsten as a main component can be adopted. Here, “main component” means a component having the highest content rate (unit: weight percent). The melting point of tungsten is approximately 3400 degrees Celsius, which is higher than other metals. Therefore, if a material containing tungsten as a main component is used, the temperature of the heating coil can be raised to a higher temperature than in the case of using other materials. As a result, a high specified temperature of the sheath heater after the temperature rise can be realized. Note that, as a material containing tungsten as a main component, for example, pure tungsten, an alloy of tungsten, nickel and copper, or an alloy of tungsten, nickel, and iron may be adopted. In any case, in order to realize a high specified temperature, the content of tungsten is preferably 50 wt% or more, particularly preferably 90 wt% or more, and most preferably 99 wt% or more.

(2) The undulating portion of the heat generating coil represents a plurality of intermediate portions (for example, the intermediate portion 820m in FIG. 2B, the intermediate portion 820am in FIG. 5) in the X-ray transmission image described in FIG. 2B. It may be provided only on some of the coil partial wires among the coil partial wires. In general, it is preferable that at least one of the plurality of coil part lines representing the middle part in the X-ray transmission image includes a wavy part. According to this configuration, it is possible to prevent the heating coil from being damaged by extending the undulated portion.

  In addition, in order to realize appropriate elongation of the coil wire, one coil partial line CL described in FIG. 2C protrudes on both of the one imaginary straight line La side and the other imaginary straight line Lb side. It is preferable to be curved. However, one coil partial line CL may extend only to one side of the one imaginary straight line La side and the other imaginary straight line Lb side.

(3) The material of the tube 810 may be another nickel alloy different from NCF 601 and DIN 2.4 633 (alloy 602), and may be a metal different from the nickel alloy (for example, stainless steel). In any case, the coefficient of thermal expansion of the tube 810 may be smaller than the coefficient of thermal expansion of the heating coil.

(4) As the configuration of the glow plug, various other configurations can be adopted instead of the above-described configuration. For example, the coils 820a, 830 may be joined to the tip 321 of the middle shaft 30 (eg, welded or brazed) without being wound around the tip 321 of the middle shaft 30. Further, an external thread is formed on the outer peripheral surface of the rear end 319 of the center shaft 30, and an internal thread is formed on the terminal member 80, and the terminal member 80 is screwed into the rear end 319 of the center shaft 30. The terminal member 80 may be fixed. Here, as the terminal member 80, a nut may be employed instead of the cap-like member.

(5) The above-mentioned glow plug is applicable not only to the glow plug utilized for starting assistance of an internal combustion engine but to various glow plugs. For example, an exhaust gas heater device for raising the temperature of exhaust gas, a burner system for reactivating a catalyst and a diesel particulate filter (DPF: Diesel Particulate Filter), a water heater device for raising the temperature of cooling water, etc. The glow plug of the above-mentioned embodiment is applicable to the glow plug used for various devices of the above.

  As mentioned above, although this invention was demonstrated based on embodiment and a modification, above-mentioned embodiment of the invention is for making an understanding of this invention easy, and does not limit this invention. The present invention can be modified and improved without departing from the spirit and the scope of the claims, and the present invention includes the equivalents thereof.

10, 10a: glow plug, 20: metal shell, 20x: through hole, 21: body portion, 22: male screw portion, 28: tool engaging portion, 30 .. ... Middle shaft, 321... Tip, 319... Rear end part, 50 .. O ring, 60 .. insulation member, 62 .. cylindrical part, 68 .. flange part, 80. Terminal member 800, 800a: Sheath heater (heater member), 810: Tube, 811: tip end portion, 819: rear end portion, 820, 820a: heating coil, 820 m, 820 am. . Middle part, 821, 821a ... tip, 829, 829a ... rear end, 822, 822a ... first part (end), 828, 828a ... second part (end), 823 824, 824a, 827a ... welds, 830 ... rear end coil, 831 ... tip, 837 ... welds, 839 ... rear end, 840 ... insulating powder, 850. .Packing, D1 ... first direction D2 ... second direction, CL ... coil partial wire, dL ... interval, CL, CLr ... coil partial wire, CR ... crack, CS ... cross section, CS1 ... first Cross section, CS2: second cross section, L1, L2, La, Lb: imaginary straight line, Dc: minimum line width, Dg: maximum interval, OP1: opening, OP2: opening, AX1 ... first axis (central axis), AX2 ... second axis, Gc1 ... first center of gravity, Gc2 ... second center of gravity, Lgc ... virtual line segment

Claims (4)

A tubular tube which extends along the direction of the first axis and whose tip is closed;
A helical, tungsten-based heat-generating coil disposed in the tube and having its tip joined to the tip of the tube and extending towards the rear end in the direction of the first axis; ,
A conductive member in which the rear end of the heat generating coil is joined to its front end;
A glow plug comprising
A flat surface including a second axis which is an axis of the middle portion of the heat generating coil for an intermediate portion which is a remaining portion of the heat generating coil except the three turns from the front end and the three turns from the rear end. In the X-ray transmission image, when the X-ray transmission image is obtained by irradiating the X-ray to the cross section of the one side portion divided in the cross section, a plurality of intermediate portions of the heating coil are represented in the X-ray transmission image At least one of the coil segment wires includes a undulating portion,
Glow plug. A glow plug according to claim 1, wherein
In the tube, an insulating powder filling the space between the tube and the heating coil is provided.
Glow plug. A glow plug according to claim 1 or 2, wherein
In the X-ray transmission image, the maximum value of the distance in the direction of the second axis between the coil partial lines adjacent to each other is smaller than the minimum value of the line width in the direction of the second axis of the coil partial line
Glow plug. A glow plug according to any one of claims 1 to 3, wherein
In the X-ray transmission image, two straight lines parallel to a line connecting the centers of gravity of the two cross-sectional portions at both ends of one coil partial line and in contact with the contour of the coil partial line When interposing the whole of the one coil partial wire with a straight line, the distance between the two straight lines is equal to or less than twice the minimum value of the line width in the direction of the second axis of the coil partial wire. Is
Glow plug.

Images