JP2013228123A - Glow plug - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a glow plug which easily secures rigidity.SOLUTION: A glow plug 10 includes a metal fixture 500 having a through-hole 510 extending in an axial direction, a heater member 800 that generates heat by being applied with a current, and a center shaft 200 inserted into the through-hole. The metal fixture includes: a first part 591 which is located at an axial front end side and in which the inner diameter of the through-hole is a first inner diameter; and a second part 592 in which the inner diameter of the through-hole is a second inner diameter and which is disposed at the axial rear end side of the first part. A part of the heater member is inserted to a part formed by the first part the through-hole, and the front end of the heater member is disposed on the front side from the front end of the metal fixture. The heater member is held by the first part of the metal fixture. The center shaft includes a part which is electrically connected to the heater member and inserted to a part formed by the second part of the through-hole. The second inner diameter of the second part of the metal fixture is smaller than the first inner diameter of the first part of the metal fixture, and the thickness of the second part of the metal fixture is larger than the thickness of the first part of the metal fixture.

Description

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

  Conventionally, glow plugs that generate heat when energized are used for ignition of internal combustion engines and the like. As a structure of such a glow plug, for example, a structure having a housing having an inner hole, a heater inserted into the inner hole, and a central shaft for energizing the heater is proposed. A fitting portion is provided in the inner hole of the housing. The inner diameter of the fitting part is smaller than the inner diameter of the other part of the inner hole. The heater is press-fitted into the fitting portion. As a result, the heater is fixed to the housing.

Japanese Patent Laid-Open No. 11-94253

  However, sufficient consideration has not been given to devising the structure of the glow plug with a focus on ensuring rigidity. Such issues are not limited to glow plugs used to ignite internal combustion engines, but also reactivate exhaust gas heaters to raise the temperature of exhaust gases, catalysts and diesel particulate filters (DPFs). This is a problem common to glow plugs used in various devices such as a burner system for converting to a water heater and a water heater device for raising the temperature of cooling water.

  The main advantage of the present invention is to provide a glow plug that can easily ensure rigidity.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following application examples.

[Application Example 1] A metal fitting having a through-hole extending in the axial direction, the first portion being located on the distal end side in the axial direction and having an inner diameter of the through-hole being the first inner diameter, and the inner diameter of the through-hole being the first And a heater member that generates heat by energization, wherein a part of the heater member is the through-hole. The heater member is inserted into a portion formed by the first portion of the heater, the tip of the heater member is disposed closer to the tip than the tip of the fitting, and is held by the first portion of the fitting, and the penetration A glow plug comprising: a middle shaft inserted into a hole, the middle shaft including a portion electrically connected to the heater member and inserted into a portion formed by the second portion of the through hole. The second of the bracket The second inner diameter is less than the first inner diameter of the first part of the metal fitting, and the thickness of the second part of the metal fitting is smaller than the thickness of the first part of the metal fitting, Thick, glow plug.
According to this configuration, the rigidity of the glow plug can be easily ensured as compared with the case where the second inner diameter is larger than the first inner diameter.

Application Example 2 In the glow plug according to Application Example 1, the metal fitting includes a third portion disposed between the first portion and the second portion, and an inner diameter of the third portion is A glow plug that becomes smaller from the first part side toward the second part side.
According to this configuration, the third portion having a smaller inner diameter is disposed between the first portion and the second portion having different inner diameters from the first portion side toward the second portion side. The possibility that the rigidity of the metal fitting is lowered in the portion between the portion and the second portion can be reduced.

[Application Example 3] The glow plug according to Application Example 2, wherein the inner diameter of the third portion continuously decreases from the first portion side toward the second portion side.
According to this configuration, the third portion whose inner diameter continuously decreases from the first portion side toward the second portion side is disposed between the first portion and the second portion having different inner diameters. The possibility that the rigidity of the metal fitting is lowered in the portion between the first portion and the second portion can be further reduced.

[Application Example 4] The glow plug according to any one of Application Examples 1 to 3, wherein the metal fitting includes a screw thread formed on an outer surface of the metal fitting to be screwed into an attachment hole of the attachment object. The position of the first portion of the metal fitting in the axial direction is arranged at a position away from the screw thread toward the tip side, and the range of the second portion of the metal fitting in the axial direction is the first portion. A glow plug including a range from a position between a part and the thread to an end of the thread on the first part side.
According to this configuration, the inner diameter (second inner diameter) of the metal fitting in the range from the position between the first part and the screw thread to the end on the first part side of the screw thread is the first of the first part of the metal fitting. Since it is smaller than the inner diameter, the rigidity of the glow plug can be easily secured.

[Application Example 5] The glow plug according to any one of Application Examples 1 to 4, wherein an outer diameter of a portion disposed in a portion formed by the second portion of the through hole in the central shaft is A glow plug that is smaller than the outer diameter of the portion of the heater member held by the first portion.
According to this structure, the internal diameter of the 2nd part of a metal fitting can be appropriately made smaller than the internal diameter of the 1st part of a metal fitting.

  The present invention can be realized in various modes, and includes, for example, a glow plug, various parts (for example, metal fittings) constituting the glow plug, an internal combustion engine equipped with the glow plug, and the internal combustion engine. It can implement | achieve in aspects, such as a vehicle.

It is explanatory drawing which shows the glow plug as one Example of this invention. It is sectional drawing which mainly shows the structure of the metal shell of a glow plug. It is explanatory drawing which shows the glow plug 10a in 2nd Example.

A. First embodiment:
Next, embodiments of the present invention will be described based on examples. FIG. 1 is an explanatory view showing a glow plug as one embodiment of the present invention. The glow plug 10 functions as a heat source for assisting ignition of an internal combustion engine (for example, a diesel engine) (not shown). The glow plug 10 includes a terminal 100, a middle shaft 200, a ring-shaped insulating member 300, an O (O) ring 400, a metal shell 500 (also simply referred to as a metal bracket 500), and a heater member 800. Hereinafter, the central axis CL of the glow plug 10 is also referred to as an “axis”, and a direction parallel to the central axis CL is also referred to as an “axial direction”. The metal shell 500 has a through-hole 510 extending in the axial direction (extending along the central axis CL) (also referred to as a shaft hole 510). A heater member 800 is inserted into one opening OP1 of the through hole 510. A male screw portion 540 is formed on the outer peripheral surface of the metal shell 500. Male screw portion 540 includes a thread for screwing into a female screw of a mounting hole of an internal combustion engine (not shown). In a state where the glow plug 10 is mounted on the internal combustion engine, an end portion 500e on the opening OP1 side of the metal shell 500 (hereinafter referred to as a front end portion 500e) is in contact with an inner surface (not shown) of a mounting hole of the internal combustion engine. By sealing the combustion chamber. A part of the glow plug 10 that is closer to the heater member 800 than the front end portion 500e of the metallic shell 500 (more specifically, the front end portion 811 of the heater member 800) is inserted into the combustion chamber. The part of the glow plug 10 on the side opposite to the tip 500e of the metallic shell 500 is disposed outside the combustion chamber. Hereinafter, a direction parallel to the central axis CL toward a portion (for example, the end portion 811 of the heater member 800) inserted into the combustion chamber from a portion (for example, the male screw portion 540) disposed outside the combustion chamber. Is referred to as a first direction D1, and a direction opposite to the first direction D1 is referred to as a second direction D2. Further, the first direction D1 side of the glow plug 10 is also referred to as “front end side”, and the second direction D2 side of the glow plug 10 is also referred to as “rear end side”. In addition, an end on the first direction D1 side of various members is referred to as a “front end”, and an end on the second direction D2 side is also referred to as a “rear end”. In FIG. 1, the right side of the central axis CL shows the external configuration, and the left side of the central axis CL shows the cross-sectional configuration.

  The metal shell 500 is a member in which a conductive material (for example, a metal such as carbon steel or stainless steel) is formed in a cylindrical shape. The metal shell 500 is arranged so as to extend along the central axis CL. The metal shell 500 includes a tool engaging portion 520 disposed on the second direction D2 side, and a body portion 560 extending from the tool engaging portion 520 in the first direction D1. The tool engaging portion 520 is a portion that engages with a tool (not shown) when the glow plug 10 is attached or detached. The male screw portion 540 is formed on the outer peripheral surface of the body portion 560 on the second direction D2 side (tool engaging portion 520 side).

  In this embodiment, the heater member 800 is a so-called sheath heater and generates heat when energized. A part of the heater member 800 on the second direction D2 side is press-fitted into the through hole 510 from the opening OP1 on the first direction D1 side of the through hole 510. The front end portion of the heater member 800 (the front end portion 811 of the tube 810 described later) is disposed on the front end side with respect to the front end portion 500e of the metal shell 500 (the front end side with respect to the opening OP1 on the front end side of the through hole 510). The heater member 800 includes a heating coil 820, a control coil 830, insulating powder 840, a ring-shaped packing 850, and a tube 810 that accommodates these members 820, 830, 840, and 850. The tube 810 is a member in which a conductive material (for example, nickel alloy) is formed in a cylindrical shape. The tube 810 is arranged so as to extend along the central axis CL. A distal end portion (referred to as a distal end portion 811) of the tube 810 is closed, and a rear end portion (referred to as a rear end portion 819) of the tube 810 forms an opening.

  A distal end portion 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 control coil 830 is electrically connected to the rear end 829 of the heating coil 820. These connections are, for example, welding or brazing.

  The tube 810 is inserted with the distal end portion (referred to as the distal end portion 201) of the central shaft 200 from the opening of the tube 810 on the second direction D2 side. The front end 201 of the middle shaft 200 is electrically connected to the rear end 839 of the control coil 830 (for example, welding). The packing 850 is a member in which an electrically insulating material (for example, rubber such as silicon rubber or fluorine rubber) is formed in a ring shape. The packing 850 is disposed between the rear end 819 of the tube 810 and the central shaft 200. The insulating powder 840 is a powder of an electrically insulating material (for example, magnesium oxide) and is filled in the tube 810. The packing 850 and the insulating powder 840 electrically insulate the tube 810 and the middle shaft 200 over the entire circumference surrounding the central axis CL. Further, the insulating powder 840 suppresses an unintended electrical short circuit among the heating coil 820, the control coil 830, the central shaft 200, and the tube 810.

  The middle shaft 200 is a member in which a conductive material (for example, a metal such as nickel, stainless steel, or carbon steel) is formed in a columnar shape. The middle shaft 200 is supported by the metal shell 500 while being inserted into the through hole 510 of the metal shell 500. Specifically, the rear end portion (referred to as the rear end portion 209) of the middle shaft 200 is disposed on the second direction D2 side with respect to the opening OP2 on the second direction D2 side of the metal shell 500. The O-ring 400 and the insulating member 300 are fitted into the middle shaft 200 in this order from the second direction D2 side. The O-ring 400 is formed using an insulating material (for example, rubber such as silicon rubber or fluorine rubber). The insulating member 300 is formed using an insulating material (for example, resin). The O-ring 400 and the insulating member 300 are inserted inside the opening OP2 on the second direction D2 side of the metal shell 500. The O-ring 400 and the insulating member 300 are sandwiched between the inner surface of the through hole 510 of the metal shell 500 and the outer surface of the central shaft 200. Thus, the metal shell 500 supports the center shaft 200 via the O-ring 400 and the insulating member 300. Since the outer diameter of the middle shaft 200 is smaller than the inner diameter of the through hole 510, the outer surface of the middle shaft 200 is separated from the inner surface of the through hole 510 of the metal shell 500.

  The terminal 100 is a member in which a conductive material (for example, a metal such as nickel) is formed in a cap shape. The terminal 100 is fitted to the rear end 209 of the middle shaft 200 (the terminal 100 is electrically connected to the middle shaft 200). An insulating member 300 is sandwiched between the terminal 100 and the metal shell 500. Electric power is supplied to the heater member 800 through the terminal 100 and the central shaft 200.

  The metal shell 500 of the present embodiment can be divided into five portions 591 to 595 according to the inner diameter. For convenience of explanation, five portions 594, 591, 593, 592, and 595 arranged in order along the second direction D2 are divided into a fourth portion 594, a first portion 591, a third portion 593, a second portion 592, a second portion 592, and a second portion 592. 5 parts 595.

  FIG. 2 is a cross-sectional view (a cross-sectional view including the central axis CL) mainly showing the configuration of the metallic shell of the glow plug. 2A shows the glow plug 10 of the embodiment, and FIG. 2B shows the glow plug 10w of the reference example. First, the configuration of the embodiment of FIG.

  Description will be made in order along the second direction D2 from the end of the metal shell 500 on the first direction D1 side. The fourth portion 594 of the metal shell 500 forms an opening OP1 on the first direction D1 side of the metal shell 500. The first portion 591 is adjacent to the fourth portion 594 on the second direction D2 side. The position of the first portion 591 in the axial direction is disposed at a position away from the male screw portion 540 in the first direction D1 side (tip side). As shown in the drawing, the first portion 591 is disposed on the front end side in the axial direction of the metal shell 500 (the first portion 591 is closer to the opening OP1 on the front end side than the opening OP2 on the rear end side). A heater member 800 is press-fitted into the first portion 591. The inner diameter ID1 of the first portion 591 (hereinafter referred to as the first inner diameter ID1) is approximately the same as the outer diameter Oda of the heater member 800 (the outer diameter of the portion that contacts the first portion 591). The first portion 591 holds the heater member 800 by contacting the heater member 800. The inner surface of the first portion 591 is in contact with the outer surface of the heater member 800 over the entire circumference surrounding the central axis CL.

  The inner diameter of the fourth portion 594 of the metal shell 500 is slightly larger than the outer diameter Oda of the heater member 800. The inner diameter of the portion of the fourth portion 594 on the second direction D2 side (first portion 591 side) becomes smaller as it is closer to the first portion 591. When the heater member 800 is press-fitted into the through hole 510, the rear end portion 819 of the heater member 800 is guided into the first portion 591 by the inner surface of the fourth portion 594.

  The heater member 800 is inserted to a position between the front end (position E1) and the rear end (position E2) of the first portion 591 of the metal shell 500. That is, the portion of the inner surface of the first portion 591 that contacts the outer surface of the heater member 800 is a portion on the first direction D1 side. However, the heater member 800 may be inserted up to the rear end (position E2) of the first portion 591. That is, the entire inner surface of the first portion 591 may be in contact with the outer surface of the heater member 800.

  The third portion 593 of the metal shell 500 is a portion adjacent to the first portion 591 on the second direction D2 side. The position of the third portion 593 in the axial direction is disposed at a position away from the male screw portion 540 toward the first direction D1. The second portion 592 of the metal shell 500 is a portion adjacent to the third portion 593 on the second direction D2 side. A position E3 in the axial direction of the tip of the second portion 592 is disposed at a position away from the male screw portion 540 toward the first direction D1. The second portion 592 extends from the position E3 toward the second direction D2 over the male screw portion 540 to a position E4 that overlaps the tool engaging portion 520. The inner diameter ID2 of the second portion 592 (hereinafter referred to as the second inner diameter ID2) is smaller than the first inner diameter ID1 of the first portion 591.

  Moreover, the outer diameter of the trunk | drum 560 is constant except the part in which the external thread part 540 was formed. That is, the outer diameter OD2 of the second portion 592 in the body portion 560 is the same as the outer diameter OD1 of the first portion 591. Accordingly, the thickness T2 of the second portion 592 is thicker than the thickness T1 of the first portion 591 (the thickness is the thickness in the direction orthogonal to the central axis CL).

  The fifth portion 595 of the metal shell 500 is a portion adjacent to the second portion 592 on the second direction D2 side. The fifth portion 595 forms an opening OP <b> 2 on the second direction D <b> 2 side of the metal shell 500. The inner diameter of the fifth portion 595 is larger than the second inner diameter ID2 of the second portion 592.

  Next, the configuration of the reference example in FIG. In the reference example, the outer shape of the metal shell 500w (tool engaging portion 520w, male screw portion 540, body portion 560w) is the metal shell 500 (tool engaging portion 520, male screw portion 540, body portion 560) of the embodiment. It is the same as the external shape. However, the shape of the through hole 510w of the reference example is different from the shape of the through hole 510 of the example. The middle shaft 200 is the same as that of the embodiment. The configuration of the heater member 800w of the reference example is different from the embodiment in that a tapered portion 816w (hereinafter referred to as a tapered portion 816w) is formed on the second direction D2 side. In the taper portion 816w, the outer diameter is smaller toward the second direction D2. The internal configuration of the heater member 800w is the same as the internal configuration of the heater member 800 of the embodiment. Note that in FIG. 2B, the same components as those in FIG. 2A are denoted by the same reference numerals, and description thereof is omitted.

  The metal shell 500w of the reference example can be divided into four portions 594, 591, 592w, and 595w arranged in order along the second direction D2 according to the inner diameter (in the reference example, the third portion is omitted). ) The fourth portion 594 and the first portion 591 are the same as the fourth portion 594 and the first portion 591 of the embodiment, respectively. The heater member 800w is press-fitted into the first portion 591. The outer diameter Oda of the heater member 800w (the outer diameter of the portion in contact with the first portion 591) is approximately the same as the first inner diameter ID1 of the first portion 591.

  The second portion 592w is adjacent to the second direction D2 side of the first portion 591 of the metal shell 500w. The second portion 592w is different from the second portion 592 of the embodiment. In the reference example, the inner diameter ID2w of the second portion 592w is larger than the first inner diameter ID1 of the first portion 591. Further, the second portion 592w extends from the rear end (position E2) of the first portion 591 toward the second direction D2 side to the position E4 that overlaps the tool engaging portion 520w over the male screw portion 540. ing. Further, the outer diameter OD2w of the second portion 592w in the body portion 560w is the same as the outer diameter OD1 of the first portion 591. Accordingly, the thickness T2w of the second portion 592w is thinner than the thickness T1 of the first portion 591.

  A fifth portion 595w is adjacent to the second portion 592w on the second direction D2 side. The fifth portion 595w forms an opening OP2w on the second direction D2 side of the metal shell 500w. The inner diameter of the fifth portion 595w is larger than the second inner diameter ID2w of the second portion 592w.

  Thus, in the reference example, the inner diameter of the metal shell 500w is the smallest in the first portion 591 that contacts the heater member 800w (first inner diameter ID1), and the inner diameters of the other portions are larger than the first inner diameter ID1. And the thickness of the trunk | drum 560w of the metal shell 500 is the thickest in the 1st part 591 (thickness T1), and the thickness of another part is thinner than the thickness T1.

  Next, advantages of the glow plug 10 of the embodiment will be described. In the embodiment, the second inner diameter ID2 of the second portion 592 is smaller than the first inner diameter ID1 of the first portion 591. Therefore, the rigidity of the glow plug 10 can be easily ensured as compared with the reference example (glow plug 10w) in which the inner diameter ID2w of the second portion 592w is larger than the first inner diameter ID1 of the first portion 591.

  Specifically, in the embodiment, the thickness T2 of the second portion 592 is equal to the first portion 591 even though the outer diameter of the body portion 560 is the same as the outer diameter of the body portion 560w of the reference example. It is thicker than the wall thickness T1. As described above, the thickness T2 of the second portion 592 can be increased without increasing the outer diameter of the metal shell 500 (the body portion 560). Accordingly, in the embodiment, the rigidity of the glow plug 10 (particularly, the metal shell 500) is larger than that of the reference example (glow plug 10w) in which the thickness T2w of the second portion 592w is thinner than the thickness T1 of the first portion 591. Can be improved. Further, the outer diameter of the metal shell 500 can be reduced without reducing the rigidity of the glow plug 10.

  In the embodiment, the third portion 593 disposed between the first portion 591 and the second portion 592 of the metal shell 500 is continuously directed from the first portion 591 side toward the second portion 592 side. The inner diameter is reduced. In particular, in the embodiment, the inner diameter of the third portion 593 changes from the first inner diameter ID1 to the second inner diameter ID2. As described above, the inner diameter of the through-hole 510 continuously changes between the first portion 591 and the second portion 592 without changing stepwise. Accordingly, when a force is applied to the glow plug 10 (for example, when the internal combustion engine operates or when the glow plug 10 is attached to the internal combustion engine), stress is applied to a portion between the first portion 591 and the second portion 592. The possibility of concentration can be reduced. On the other hand, in the glow plug 10w of the reference example, since the third portion is omitted, a step is formed between the first portion 591 and the second portion 592w (position E2). When a force is applied to the glow plug 10w, stress may concentrate on this stage. Therefore, compared to the reference example (glow plug 10w), the rigidity of the glow plug 10 of the embodiment (particularly the metal shell 500) can be improved.

  Moreover, the range of the axial direction of the 2nd part 592 of the metal shell 500 of an Example is as follows. That is, the front end (position E3) of the second portion 592 is disposed between the first portion 591 and the male screw portion 540 (screw thread) (specifically, the rear end (position) of the first portion 591. E2) and the tip (position F1) of the male screw portion 540). The rear end (position E4) of the second portion 592 is disposed closer to the second direction D2 than the position F1 of the front end (first portion 591 side) of the male screw portion 540 (screw thread). Thus, the axial range of the second portion 592 is from the position E3 between the first portion 591 and the male screw portion 540 to the end (position F1) of the male screw portion 540 on the first portion 591 side. Includes range. Since the inner diameter (second inner diameter ID2) of the metal shell 500 in the range (range from position E3 to position F1) is smaller than the first inner diameter ID1 of the first portion 591, the glow plug 10 (particularly, the metal shell 500). Can be easily secured. In particular, when the glow plug 10 is mounted on an internal combustion engine (not shown), the distal end portion 500e of the metallic shell 500 comes into contact with the inner surface of the mounting hole of the internal combustion engine. An axial force acts on a portion between the tip portion 500e and the tip portion 500e. In the embodiment, the rigidity of the portion where the axial force is applied can be easily ensured as compared with the reference example. Therefore, the glow plug 10 is attached to various internal combustion engines (for example, an internal combustion engine in which the tightening torque of the glow plug 10 is large). Can be applied.

  In the embodiment, the wall thickness T2 of the second portion 592 is the same as that of the first portion 591 over the entire range from the tip (position E3) of the second portion 592 to the tip (position F1) of the male screw portion 540. Thicker than wall thickness T1. Therefore, in the embodiment, the rigidity of the portion where the axial force acts on the metal shell 500 (that is, the portion between the tip (position F1) of the male screw portion 540 and the tip portion 500e in the metal shell 500) as compared with the reference example. Can be improved. Furthermore, in this embodiment, the wall thickness is thicker than the wall thickness T1 of the first portion 591 in the entire range from the front end (position F1) to the rear end (F2) of the male screw portion 540. Therefore, the rigidity of the metal shell 500 can be further improved.

  A part of the middle shaft 200 is disposed in the through hole 510 in the second portion 592 of the metal shell 500. The outer diameter ODb of the portion disposed in the second portion 592 of the middle shaft 200 is smaller than the outer diameter Oda of the heater member 800. Accordingly, the second inner diameter ID2 of the second portion 592 can be appropriately made smaller than the first inner diameter ID1 of the first portion 591.

  As described above, the rigidity of the glow plug 10 of the embodiment (particularly, the metal shell 500) can be improved as compared with the glow plug 10w of the reference example. Therefore, the glow plug 10 can be adapted to stricter design conditions. For example, the glow plug 10 can be made thin. Further, the tightening torque of the glow plug 10 can be increased. Also, a soft material that can be easily processed can be adopted as the material of the metal shell 500.

  In the embodiment, the inner diameter is not constant on the first direction D1 side from the second portion 592 of the metal shell 500, and is larger on the first direction D1 side (closer to the opening OP1). Therefore, by using a plurality of drills having different diameters, the through hole 510 (from the second portion 592 in the first direction D1 side) of the metal shell 500 can be easily formed. For example, a fourth portion 594 is formed using a large-diameter drill, then a first portion 591 and a third portion 593 are formed using a medium-diameter drill, and then a small-diameter drill is formed. It is possible to form the second portion 592 by using it.

  In the embodiment, the inner diameter of the end portion (fifth portion 595) on the second direction D2 side of the metal shell 500 is larger than the second inner diameter ID2 of the second portion 592. Thus, on the second direction D2 side from the second portion 592 of the metal shell 500, the inner diameter is not constant and is larger toward the second direction D2 side (closer to the opening OP2). Therefore, by using a plurality of drills having different diameters, the through hole 510 (from the second portion 592 to the second direction D2 side) of the metal shell 500 can be easily formed.

B. Second embodiment:
FIG. 3 is an explanatory view showing a glow plug 10a in the second embodiment. 3A shows a partial cross-sectional view similar to FIG. 1, and FIG. 3B shows an enlarged cross-sectional view of a part of the glow plug 10a on the first direction D1 side. There are two differences between the second embodiment and the first embodiment. The first difference is that the glow plug 10a of the second embodiment uses a ceramic heater (heater member 900) instead of the sheath heater (heater member 800). The second difference is that the tip portion 201a of the middle shaft 200a is processed to be thinner than other portions of the middle shaft 200a. The configuration of the other part of the central shaft 200a is the same as the configuration of the central shaft 200 of the first embodiment. The other structure of the glow plug 10a is the same as that of the glow plug 10 of the first embodiment. In FIGS. 3A and 3B, the same components as those of the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  As shown in FIG. 3B, the heater member 900 includes an outer cylinder 910, a ceramic heater 990, a conductive line 980, a ring-shaped insulating member 950, and insulating powder 945. The ceramic heater 990 includes a ceramic base 940, a heating element 920, a first electrode 960, and a second electrode 970. A part of the heater member 900 (outer cylinder 910) on the second direction D2 side is press-fitted into the through hole 510 (first portion 591) from the opening OP1 on the first direction D1 side of the through hole 510.

  The outer cylinder 910 is a member formed of a metal (conductive material) such as stainless steel in a cylindrical shape. Both the front end and the rear end of the outer cylinder 910 form an opening. The outer cylinder 910 includes a first portion 910a and a second portion 910b adjacent to the first portion 910a on the second direction D2 side. The inner diameter of the second portion 910b is the same as the inner diameter of the first portion 910a, and the outer diameter of the second portion 910b is larger than the outer diameter of the first portion 910a. The thickness of the second portion 910b is thicker than the thickness of the first portion 910a. The second portion 910b is press-fitted into the first portion 591 of the metal shell 500. The outer diameter of the second portion 910b of the outer cylinder 910 is approximately the same as the inner diameter of the first portion 591 of the metal shell 500.

  Part of the ceramic heater 990 on the second direction D2 side is inserted into the opening on the first direction D1 side of the outer cylinder 910. The ceramic heater 990 includes a ceramic base 940 formed in a rod shape. The ceramic base 940 is fixed to the outer cylinder 910 by brazing. For example, as will be described later, the end 979 of the second electrode 970 exposed from the outer peripheral surface of the ceramic base 940 and the outer cylinder 910 are connected by brazing. Therefore, the outer diameter of the ceramic base 940 is smaller than the inner diameter of the outer cylinder 910 by the amount of the brazing material interposed. The tip 991 of the ceramic heater 990 (that is, the tip of the heater member 900) is disposed on the tip side of the metal shell 500 on the tip side (the tip side of the opening OP1 on the tip side of the through hole 510). .

  The ceramic base 940 is formed using an insulating ceramic (for example, silicon nitride or alumina). Inside the ceramic base 940, a heating element 920 formed in a U-shape that is folded back in the first direction D1 and two electrodes 960 and 970 connected to the heating element 920 are embedded. The heating element 920 is formed using a conductive ceramic (for example, a powder material containing silicon nitride and tungsten carbide). Instead, the heating element 920 is formed using a high melting point metal (for example, a metal having a melting point of 2000 degrees Celsius or higher, such as tungsten (W), molybdenum (Mo), hafnium (Hf), rhenium (Re)). May be. The two electrodes 960 and 970 are formed using a conductive ceramic having an electric resistance smaller than that of the heating element 920. As a manufacturing method of the ceramic heater 990, for example, a method of firing a formed body obtained by forming the material of each member 920, 940, 960, 970 into the shape of the ceramic heater 990 can be employed.

  A tip 961 of the first electrode 960 is connected to one end 921 of the heating element 920. The first electrode 960 extends inside the ceramic base 940 toward the second direction D2 and is exposed on the surface of the ceramic base 940 on the second direction D2 side (the end 969 of the first electrode 960 is exposed). A hole is formed in the exposed end 969, and the tip 981 of the conductive line 980 is inserted into this hole. The conductive line 980 is electrically connected to the first electrode 960 (for example, brazed). The conductive line 980 is formed using a conductive material (for example, a mild steel wire).

  A tip 971 of the second electrode 970 is connected to the other end 929 of the heating element 920. The second electrode 970 extends inside the ceramic base 940 toward the outer peripheral surface on the second direction D2 side, and is exposed from the outer peripheral surface of the ceramic base 940 (the end 979 of the second electrode 970 is exposed). The exposed end 979 is electrically connected to the outer cylinder 910 (for example, brazed).

  An end 201a of the middle shaft 200a is inserted into the outer cylinder 910 from the opening of the outer cylinder 910 on the second direction D2 side. A rear end portion 989 of the conductive line 980 is connected to the end portion 201a. The rear end portion 989 of the conductive line 980 forms a coil wound around the end portion 201a of the middle shaft 200a.

  The insulating member 950 is a member in which an electrically insulating material (for example, rubber such as silicon rubber or fluorine rubber) is formed in a ring shape. The insulating member 950 is disposed between the rear end 919 of the outer cylinder 910 and the middle shaft 200a. The insulating powder 945 is a powder of an electrically insulating material (for example, magnesium oxide) and is filled in the outer cylinder 910. The insulating member 950 and the insulating powder 945 electrically insulate between the outer cylinder 910 and the middle shaft 200a over the entire circumference surrounding the central axis CL. Further, the insulating powder 945 suppresses an unintended electrical short circuit among the middle shaft 200a, the conductive line 980, the ceramic heater 990, and the outer cylinder 910.

  As described above, the glow plug 10a of the second embodiment uses the ceramic heater (heater member 900) instead of the sheath heater (heater member 800). Also in the second embodiment, the configuration of the metallic shell 500 and the middle shaft 200a is the same as the construction of the metallic shell 500 and the middle shaft 200 of the first embodiment, so that the glow plug 10a of the second embodiment has the first configuration. It has the same various advantages as the glow plug 10 of the embodiment. For example, the rigidity of the glow plug 10a using a ceramic heater can be improved in the same manner as the rigidity of the glow plug 10 using a sheath heater.

C. Variations:
(1) The configuration of the metal shell 500 is not limited to the configuration illustrated in FIGS. 1 to 3, and various configurations can be employed. For example, a portion where the inner diameter changes stepwise may be provided between the first portion 591 and the third portion 593. In addition, a portion where the inner diameter changes stepwise may be provided between the second portion 592 and the third portion 593. In any case, it is preferable to provide a third portion 593 having a smaller inner diameter from the first portion 591 side toward the second portion 592 side between the first portion 591 and the second portion 592. By so doing, it is possible to suppress the occurrence of a portion in which the inner diameter greatly changes in a stepped manner between the first portion 591 and the second portion 592, and thus it is possible to suppress a decrease in rigidity of the metal shell 500. Here, the inner diameter of the third portion 593 may change stepwise through a plurality of steps, or instead may change continuously. If the third portion 593 whose inner diameter changes continuously as in the embodiment of FIG. 2A, the possibility of stress concentration on a part of the third portion 593 can be reduced. In any case, the inner diameter of the third portion 593 preferably changes within the range from the first inner diameter ID1 of the first portion 591 to the second inner diameter ID2 of the second portion 592. If it carries out like this, since it can suppress effectively that the part which an internal diameter changes large stepwise is produced, the rigidity fall of the metal shell 500 can be suppressed effectively. However, the third portion 593 can be omitted.

  Further, the fourth portion 594 may be omitted. In this case, like the heater member 800w in FIG. 2B, the heater member includes a tapered portion (for example, a tapered portion 816w) whose outer diameter decreases toward the second direction D2, and the rear end of the heater member. It is preferable that the outer diameter (for example, the end 819w) is smaller than the first inner diameter ID1 of the first portion 591. By so doing, the heater member can be easily press-fitted into the first portion 591.

  Further, the fifth portion 595 may be omitted, and the second portion 592 may extend to the rear end of the metal shell 500. In addition, the rear end (FIG. 2A, position E4) of the second portion 592 may be disposed between the front end (position F1) and the rear end (position F2) of the male screw portion 540. You may arrange | position at the 1st direction D1 side rather than the front-end | tip (position F1) of the part 540. Further, the outer diameter OD2 of the second portion 592 may be smaller than the outer diameter OD1 of the first portion 591.

  Generally, the structure of the metal shell includes a first portion in which the inner diameter of the through hole is the first inner diameter, and a second portion in which the inner diameter of the through hole is the second inner diameter (smaller than the first inner diameter). Various configurations can be employed. And the 1st part hold | maintains a heater member and the center axis | shaft electrically connected to the heater member contains the part inserted in the part formed of the 2nd part of a through-hole. In this way, the rigidity of the glow plug can be easily secured.

(2) The configuration of the central shafts 200 and 200a is not limited to the configuration shown in FIGS. 1, 2A, and 3B, and various configurations can be employed. For example, a male screw may be formed on the outer surface of the rear end portion 209 of the middle shaft 200, 200a, and a female screw that is screwed with the male screw of the rear end portion 209 may be formed on the terminal 100. Further, the outer diameter of the middle shaft is not constant, and may change according to the position in the axial direction.

(3) The configuration of the heater member is not limited to the configuration shown in FIGS. 1, 2A, 2B, and 3B, and various configurations can be employed. For example, the control coil 830 in FIG. 1 may be omitted. Moreover, not only a sheath heater and a ceramic heater but various kinds of heaters can be adopted. Also, various configurations different from the configurations of the above-described embodiments can be adopted as the configuration of the connection portion between the heater member and the central shaft.

(4) In each of the above embodiments and modifications, as a method of electrically connecting two conductive members (for example, the central shaft 200 and the control coil 830 in FIG. 1), contact by fitting, screwing, or the like, Various methods such as brazing and welding can be employed.

(5) The glow plugs of the above embodiments and modifications can be used not only for ignition of internal combustion engines but also for various applications. For example, the above glow plug can be used as a heat source of an exhaust gas heater device for raising the temperature of exhaust gas from an internal combustion engine. The glow plug can be used as an ignition source for a burner system for reactivating a catalyst or a diesel particulate filter provided in an exhaust gas pipe. Such a burner system can be mounted on an exhaust gas pipe. The glow plug can be used as a heat source of a water heater device for raising the temperature of the cooling water of the internal combustion engine. In either case, a thread is formed on the inner surface of the mounting hole of the glow plug mounting target (for example, an internal combustion engine, an exhaust gas heater device, a burner system, a water heater device), and the glow plug is mounted on the outer surface of the bracket. It is preferable to form a screw thread for screwing into a screw thread formed in the attachment hole of the object. In this way, the glow plug can be easily attached to the attachment object.

  As mentioned above, although this invention was demonstrated based on the Example and the modification, Embodiment mentioned above is for making an understanding of this invention easy, and does not limit this invention. The present invention can be changed and improved without departing from the spirit and scope of the claims, and equivalents thereof are included in the present invention.

10, 10a, 10w ... Glow plug, 100 ... Terminal, 200, 200a ... Middle shaft, 300 ... Insulating member, 400 ... O-ring, 500, 500w ... Main metal fitting, 510, 510w ... through-hole, 520, 520w ... tool engaging part, 540 ... male screw part, 560,560w ... body part, 500e ... tip part, 591 ... first part, 592, 592w ... 2nd part, 593 ... 3rd part, 594 ... 4th part, 595 ... 5th part, 800, 800w ... heater member, 810 ... tube, 816w ... Tapered portion, 820 ... Heat coil, 830 ... Control coil, 840 ... Insulating powder, 850 ... Packing, 900 ... Heater member, 910 ... Outer cylinder, 910a ... 1st part, 910b ... 2nd part, 920 ... heating element, 940 ... ceramic substrate, 945 ... insulating powder, 950 ... insulating member, 960 ... 1st electric , 970 ... second electrode, 980 ... conductive lines, 990 ... ceramic heater

Claims (5)

A metal fitting having a through hole extending in the axial direction, wherein the first part is located on the distal end side in the axial direction and the inner diameter of the through hole is the first inner diameter, and the inner diameter of the through hole is the second inner diameter, and A second part disposed closer to the rear end side in the axial direction than the first part;
A heater member that generates heat when energized, wherein a part of the heater member is inserted into a part formed by the first part of the through-hole, and a tip of the heater member is disposed on a tip side of a tip of the metal fitting. The heater member held by the first portion of the metal fitting,
A middle shaft inserted into the through hole, the middle shaft being electrically connected to the heater member and including a portion inserted into a portion formed by the second portion of the through hole;
Glow plug with
The second inner diameter of the second part of the metal fitting is smaller than the first inner diameter of the first part of the metal fitting,
A glow plug in which the thickness of the second portion of the metal fitting is thicker than the thickness of the first portion of the metal fitting. The glow plug according to claim 1,
The metal fitting includes a third part disposed between the first part and the second part,
The inner diameter of the third part decreases from the first part side toward the second part side,
Glow plug. The glow plug according to claim 2,
The inner diameter of the third part continuously decreases from the first part side toward the second part side.
Glow plug. A glow plug according to any one of claims 1 to 3,
The metal fitting includes a screw thread formed on the outer surface of the metal fitting to be screwed into the attachment hole of the attachment object.
The position in the axial direction of the first portion of the metal fitting is disposed at a position away from the screw thread toward the tip side,
The range in the axial direction of the second portion of the metal fitting includes a range from a position between the first portion and the thread to an end on the first portion side of the thread,
Glow plug. The glow plug according to any one of claims 1 to 4,
An outer diameter of a portion arranged in a portion formed by the second portion of the through hole in the central shaft is smaller than an outer diameter of a portion held in the first portion in the heater member. plug.

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