JP2006153338A - Glow plug - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a glow plug comprising a terminal portion capable of preventing the breakage of an axis and the increase of contact resistance on the terminal portion even when the stress caused by firing pressure from a combustion chamber and the stress caused by vibration or the like of an engine are applied to the terminal portion of a glow plug rear end portion in the glow plug where a ceramic heater and the axis are mechanically connected. <P>SOLUTION: In the ceramic heater 30, its rear end portion and a tip portion of the rod-shaped axis 20 are connected by a ring member 21. The terminal portion formed on the rear end portion of the rod-shaped axis 20 is composed of a circular member 70 and the rear end portion of the axis 20 projecting from the circular member 70 to a rear end side. By applying the terminal portion constituted as mentioned above, the stress applied to the axis 20 in vibration can be reduced in comparison with a conventional terminal portion constituted by combining a pin terminal and the axis 20, thus the breakage of the axis 20 and the increase of contact resistance can be inhibited or reduced. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a glow plug used for preheating a diesel engine and a glow plug used for heating liquid, gas, and the like.

  Conventionally, glow plugs have a heat generating coil housed at the end of a cylindrical metal tube with a bottom, and a heater that forms a heater, or an insulating ceramic as the base of the heater, and heat generated from the conductive ceramic inside. There are various shapes such as ceramic glow plugs that employ a ceramic heater with an embedded body. All of these glow plugs are used for preheating of a diesel engine, and conventionally, the glow plugs are used by being attached to the engine head in a form in which a heat generating portion at the tip of the heater protrudes into the auxiliary combustion chamber. The heat generating part protruding into the sub-combustion chamber is connected to a connector formed at the rear end of the glow plug with a cap or terminal plate (electrode plate) so that electric power is supplied from an external power source such as a battery. Heat was generated and the engine was preheated (pre-glow).

  In recent years, there is a direct injection type diesel engine in which fuel and air are directly injected into a combustion chamber and ignited for the purpose of improving fuel consumption and output. For environmental considerations, there is also a so-called afterglow that causes the glow plug to generate heat by energizing the glow plug even after the engine is started for the purpose of purifying exhaust gas. As described above, a demand for a ceramic glow plug is increasing among the above glow plugs due to a demand for high temperature durability due to higher performance of the engine.

  Conventionally, this ceramic glow plug has the following configuration. As shown in FIG. 9A, the ceramic heater 130, the metal shell 110 provided with a male screw portion for mounting to the engine head, the outer cylinder 160 for press-fitting and holding the ceramic heater 130, and the ceramic heater 130 are provided. The pin terminal 170 for supplying electric power from the outside to the heating element, the middle shaft 120 and the lead coil RC, the insulating member 140 for ensuring insulation between the middle shaft 120 and the metal shell 110, and the insulating member 140 are pressed, An O-ring 150 or the like that keeps the airtightness in the metal shell 110 is provided (see Patent Document 1).

  In the glow plug having the above configuration, a socket terminal for supplying power from the battery is connected to the pin terminal 170 at the rear end of the glow plug. The conduction path of the electric power is roughly grounded to the center shaft 120, the ceramic heater 130, the outer cylinder 160, the metal shell 110, and the engine head. The glow plug of this configuration can relieve the stress of the lead coil RC even when the combustion pressure from the combustion chamber acts on the ceramic heater 130 toward the rear end in the axial direction due to combustion of the engine. It is possible to prevent the heater 130 from being destroyed or damaged.

Incidentally, there is a configuration in which the middle shaft 120 and the ceramic heater 130 are directly connected by a ring member 121 as shown in FIG. 9B instead of the lead coil RC. According to this configuration, in particular, when the size of the male thread portion of the metal shell is M8 or less, a predetermined cross-sectional area can be obtained even if the thickness of the ring member 121 is reduced. It is described that a gap with the metal shell 110 can be secured and insulation can be maintained without making the shape (see Patent Document 2).
JP 2003-56848 A JP 2003-130349 A

  However, with the configuration as described in Patent Document 2, it becomes apparent that the configuration of Patent Document 1 did not cause a problem. Because the heater is mechanically joined to the center shaft, when the combustion pressure from the combustion chamber exerts stress on the heater, the stress causes the center shaft to vibrate in the direction perpendicular to the axis, and the rear end of the glow plug Stress may be applied to the part. In addition, the cap connected to the connector vibrates due to the vibration of the engine itself, which may also apply a load to the rear end of the glow plug.

  In such a situation, the glow plug rear end structure described in Patent Document 1 is a pin terminal, and the connection between the heater and the central shaft is connected by the ring member described in Patent Document 2. In the case of the configuration (see FIG. 10), the following problem occurs.

  The pin terminal is fitted with its recess in a knurling provided at the rear end of the middle shaft and fixed by caulking the middle shaft from the outer periphery in the radial direction, or the inner periphery of the male screw and the pin terminal screwed at the rear end of the middle shaft It is fixed by screwing with a female screw threaded on the head. However, when it is fixed by screwing, it may be loosened by vibration, and even when it is fixed by crimping, the caulking may be loosened due to repeated stress. . Even if the joint between the two is kept loose, even if the glow plug has a small diameter of M8 or less, the center shaft itself is also reduced in diameter. In particular, breakage may occur near the rear end face of the metallic shell. In addition, since the diameter of the central shaft is reduced, the contact area with the pin terminal is reduced, the contact resistance becomes unstable, and heat generation is not stable.

  The inventors tried to elucidate this phenomenon after intensive studies. As a result, it has been found that the magnitude of stress due to vibration acting on the rear end of the central shaft is caused by the weight of the joined pin terminals constituting the connector. An object of the present invention is to provide a structure that solves the above problems by reducing the stress acting on the rear end of the glow plug in a glow plug having a structure in which vibration from the combustion chamber extends to the rear end of the glow plug. There is.

In order to achieve the above object, a glow plug of the invention described in claim 1 is provided.
A rod-shaped ceramic heater in which a heating element that generates heat when energized is housed inside its tip, and
The ceramic heater that has a shaft hole, holds the ceramic heater inserted in the radial direction of the shaft hole so that the tip of the ceramic heater protrudes from the tip surface of the ceramic heater, and is a male screw portion for engine attachment on its outer peripheral surface A cylindrical metal shell formed with
A rod-shaped central shaft for supplying power to the heating element, the rear end portion of the metal shell being disposed so as to protrude from the rear end surface of the metal shell;
A ring member that holds the rear end portion of the ceramic heater and the front end portion of the central shaft and mechanically connects the two;
An annular member disposed between the rear end surface of the metal shell and the rear end portion of the middle shaft in the axial direction and fixed to the middle shaft;
With
A glow plug which is a connector whose rear end is electrically connected to the outside,
The connector comprises at least a rear end portion of the middle shaft and the annular member.

  The connection between the ceramic heater and the central shaft is made of a ring member. When combustion pressure from the combustion chamber side is applied to the ceramic heater, the central shaft vibrates due to the stress and is transmitted to the connector at the rear end. On the other hand, the vibration of the engine itself and the vibration transmitted from the road surface also apply stress to the connector because the cap is connected to the connector. However, when the connector is constituted by the rear end portion of the middle shaft and the annular member as in the present invention, the pin terminal is joined to the conventional middle shaft (in other words, the middle shaft supports the pin terminal). Compared with the form, the weight of the member to be supported by the middle shaft is reduced, so that the load on the rear end portion of the middle shaft to which the annular member is joined is also reduced. Furthermore, while the rearmost end of the glow plug is a relatively heavy pin terminal, in the present invention, the rearmost end is constituted by a middle shaft, and an annular member is formed at a position on the front end side of the middle end. Thus, the distance from the working point to the working point is shortened. The distance from the force point (that is, the ceramic heater to which combustion pressure is applied) to the fulcrum (that is, the male thread formed on the outer peripheral surface of the metal shell) is the same, and the point of action (the point where the load is applied to the center shaft) That is, if the distance between the pin terminal and the rear end of the middle shaft in the conventional structure, and the portion to which the annular member on the front end side is fixed from the rear end of the middle shaft in the configuration of the present invention is shortened. The stress at the point of action is reduced. Therefore, the stress load on the central shaft is reduced. Therefore, the phenomenon that the fixing of the annular member is loosened can be suppressed or reduced.

The second configuration of the glow plug of the present invention is as follows.
The annular member is made of metal, and is caulked in a radial direction and fixed to the center shaft.

  Since the annular member is made of metal, the annular member can be fixed to the central shaft by caulking from the outer periphery of the annular member toward the inside in the radial direction. Since the caulking and fixing can be performed without using other members (such as a solder and an adhesive), the caulking can be fixed to the central shaft without increasing the weight at the point of action. Therefore, the connector can be formed without increasing the weight.

The third configuration of the glow plug of the present invention is as follows.
It is M8 or less of the external thread part formed in the outer peripheral surface of the said main metal fitting, It is characterized by the above-mentioned.

  As described above, when the diameter of the middle shaft is smaller than that of the conventional one such as M8 or less, there is a concern about the breakage of the middle shaft due to a decrease in the strength of the middle shaft. Therefore, it is possible to prevent breakage of the middle shaft and to reduce the frequency of occurrence thereof. Furthermore, since the stress is reduced, it can be improved that the contact resistance becomes unstable.

The glow plug of the present invention will be described below with reference to the drawings.
FIG. 1 is a half sectional view showing an entire glow plug 1 according to an embodiment of the present invention. The glow plug 1 is generally configured by combining a metal shell 10, a central shaft 20, a ceramic heater 30, an insulating member 40, an O-ring 50, an outer cylinder 60, and an annular member 70.

  A rod-shaped central shaft 20 with one end protruding toward the rear end side is accommodated on the inner peripheral side of the cylindrical metal shell 10 of the glow plug 1 of the present invention, and a ceramic heater 30 is connected to the front end side of the central shaft 20. ing. The outer surface of the ceramic heater 30 is held by the outer cylinder 60, and the outer cylinder is joined to the tip of the metal shell 10. On the other hand, the O-ring 50 and the insulating member 40 are inserted into the gap between the middle shaft 20 and the metallic shell 10 on the rear end side of the metallic shell 10, and the annular member 70 is fixed to the middle shaft 20 from the periphery on the rear end side of the insulating member 40. Has been.

Hereinafter, details of each member will be described.
The metal shell 10 has a cylindrical shape made of an iron-based material equivalent to S45C, and has a male screw 11 for attachment to the diesel engine head 300 (see FIG. 2) on its outer peripheral surface. A tool engagement portion 12 with which the attachment tool engages is formed on the rear end side. On the other hand, a shaft hole 13 is formed on the inner periphery of the metal shell, and a metal shell side taper 14 that expands the shaft hole 13 toward the rear end side at the rear end portion, and a further rear of the metal shell side taper 14. A large-diameter hole 15 is formed adjacent to the end side.

  The middle shaft 20 accommodated on the inner peripheral side of the metal shell 10 has a rod-like shape, and is made of an iron-based material such as S45C like the metal shell 10. The middle shaft 20 plays a role of conducting the electric power supplied from the outside to the rear end portion 26 to the ceramic heater 30, and the electrical connection is that the ring member 21 for conduction with the ceramic heater 30 is connected to the front end portion 22. Made by. A tip end portion 22 to which the ring member 21 is joined is formed with a joint diameter small portion 23 having a smaller diameter than the rear end side of the ring member 21 and a tip-facing end surface 25 that forms the joint diameter small portion 23. The ring member 21 is joined in a state where the rear end surface of the ring member 21 is in contact with the end surface 25 facing the front end.

  The ring member 21 is a cylindrical member having an outer diameter substantially equal to the maximum diameter of the middle shaft 20 (that is, the tip diameter large portion 24 of the middle shaft 20). By having a diameter, it can be joined coaxially with the central shaft.

  The ceramic heater 30 has a structure in which a heating element 32 and a lead portion 33 made of conductive ceramic are embedded in a rod-shaped insulating ceramic base 31. The heating element 32 is located on the distal end side inside the ceramic heater 30 and is formed in a substantially U shape. Two lead portions 33 extending rearward from the respective base ends of the heating element 32 are formed. One of the lead portions 33 is formed by exposing the electrode extraction portion 34 to the surface of the ceramic base 31 so as to be conductive with the ring member 21 at the rear end portion of the ceramic heater 30. On the other hand, an electrode extraction part 35 is similarly formed in the radial direction so as to be electrically connected to the outer cylinder 60 on the tip side from the electrode extraction part 34.

  The outer cylinder 60 has a cylindrical body made of stainless steel, and a shaft hole 61 is formed on its inner peripheral side. A distal end portion 36 of the ceramic heater 30 in which the heating element 32 is accommodated is inserted into the shaft hole 61 so as to protrude from the distal end surface 66 of the outer cylinder 60 and is press-fitted and exposed to the outer peripheral surface of the ceramic heater 30. At least a part of the electrode extraction portion 34 is in contact with the surface of the shaft hole 61 (the inner peripheral surface of the outer cylinder 60) and is electrically connected. A small diameter portion 62 that fits into the metal shell 10 is formed at the rear end portion of the outer cylinder 60, and a flange 63 that protrudes in the radial direction is formed at the front end side, and the rear end surface of the flange portion 63 is the metal shell. A taper 65 is formed on the rear end-facing end face 64 that contacts the front end face 16 and the front end side of the flange 63 to maintain airtightness with the combustion chamber when attached to the engine head 300 as shown in FIG. Has been.

  On the rear end side of the glow plug 1, as shown in FIG. 2, a terminal portion 75 to which a wiring cord with a socket terminal for supplying power from an external power source is connected is formed. Prior to the formation of the terminal portion 75, the O-ring 50 for keeping the outside and inside of the glow plug 1 airtight is disposed on the distal end surface 41 of the insulating member 40 while being pressed toward the distal end in the axial direction. The annular member 70 constituting the terminal portion 75 also serves to fix the O-ring 50 and the insulating member 40 so as not to be detached from the middle shaft 20. The terminal portion 75 projects the rear end portion 26 of the middle shaft 20 further from the rear end face 42 of the insulating member 40 toward the rear end side, and the annular member 70 (made of stainless steel) so that the middle shaft 20 is positioned on the inner peripheral side. Is circumferentially caulked. The rear end portion 26 of the intermediate shaft 20 and the annular member 70 constitute a terminal portion 75, and this terminal portion 75 corresponds to the connector of the present invention.

  Since this terminal portion 75 is exposed from the engine head 300 or accommodated and mounted inside the engine head, stainless steel or the like is used so as not to be deteriorated by being exposed to moisture such as outside air or rain water and engine oil mixed with metal powder. It is formed of a metal material having excellent corrosion resistance.

Each of the above members is manufactured as follows, and is assembled with each other to constitute the glow plug 1.
First, the heating element 32 and the lead part 33 are integrally molded from a ceramic powder as a raw material, and prepared as a heating part powder molding 330. On the other hand, as the ceramic base 31, ceramic powder as a raw material is press-molded in advance to form a divided molded body 340 having a concave portion in which the heat generating portion powder molded body 330 is accommodated on its mating surface (see FIG. 3 (a)). Then, the heat generating part powder molded body 330 is accommodated in a concave portion provided in the divided molded body 340, and after press compression, the outer peripheral surface is subjected to a baking process such as a binder removal process and a hot press. The ceramic heater 30 shown in FIG. 3B is obtained by polishing and arranging in a cylindrical shape. (Note that in FIG. 3A, the portions that become the electrode extraction portions 34 and 35 after completion of the ceramic heater 30 are shown in parentheses.)

  The ring member 21 is formed of a steel material such as stainless steel in a pipe shape so that its inner diameter is slightly larger than the outer diameter of the ceramic heater 30 (FIG. 4A). Similarly, the outer cylinder 60 is also formed so that its own inner hole 61 is slightly larger than the outer diameter of the ceramic heater 30. The members fitted to the outer periphery of the ceramic heater 30 are the inner peripheral surfaces of the ring member 21 and the outer cylinder 60 for the purpose of reducing the press-fitting load and preventing oxidation of the electrode extraction portions 34 and 35 exposed on the surface of the ceramic heater 30. Is subjected to soft plating excellent in oxidation resistance such as Cu and Au. In addition, since the rear end side of the ring member 21 is laser-welded to the middle shaft 20, the portion to be welded (specifically, the portion in contact with the joint diameter small portion 23 on the inner peripheral surface of the ring member 21) is plated. Is not necessarily applied.

  Then, the ceramic heater 30 is fitted by press fitting, interference fitting, or the like so that the one electrode extraction portion 34 of the lead portion 33 is electrically connected to the inner peripheral surface of the tip portion of the ring member 21 to achieve conduction. Similarly, with respect to the electrode extraction part 35, the outer cylinder 60 is press-fitted to the outer periphery of the ceramic heater 30 by fitting, interference fitting, or the like, so that the electrode extraction part 35 and the outer cylinder 60 are electrically connected. The tube 60 and the ring member 21 are integrated (FIG. 4B). (Hereinafter, this integrated member is referred to as a heater integrated member.)

  On the other hand, the central shaft 20 forms the central shaft 20 by performing plastic working, cutting or the like on a rod-shaped member made of an iron-based material such as S45C cut to a certain size. One end of a rod-like member that is the front end side of the middle shaft 20 is formed with a small joining diameter portion 23 that is joined to the ring member 21, and the other end that is the rear end side is fixed with an annular member 70 to a terminal portion (connector) 75. Therefore, a knurling process is applied to a portion where the inner peripheral surface of the annular member 70 abuts.

  A positioning end surface 25 serving as a boundary surface with the large distal end diameter portion 24 is formed on the rear end side of the small joint diameter portion 23 serving as the distal end side of the middle shaft 20. By forming the positioning end face 25 in advance and securing the axial length of the small joint diameter portion 23, the joint diameter small portion 23 press-fitting length when the ring member 21 and the middle shaft 20 are joined in a later process. It is also possible to avoid the problem that the bonding strength is insufficient due to the shortage. In addition, it becomes easy to match | combine coaxially when this joining diameter small part 23 joins a heater integrated member by making the outer diameter substantially equivalent to the internal diameter of the ring member 21. FIG.

  Laser welding L is performed on the intermediate shaft 20 manufactured as described above and the above-described heater integrated member (FIG. 5A). At the time of this welding, welding is performed in a state where the small joint diameter portion 23 of the middle shaft 20 is inserted into the ring member 21 and the positioning end surface 25 of the middle shaft 20 is pressed against the rear end surface of the ring member 21. By doing in this way, it becomes possible to join, suppressing the shift | offset | difference of the coaxiality of the center axis | shaft 20 and a heater integral member to the minimum.

  In this way, the metal shell 10 is inserted into the inner hole 13 of the metal shell 10 from the rear end side of the joined heater integrated member and the middle shaft 20, that is, the rear end side of the middle shaft 20 (FIG. 5B). . Then, the front end surface of the metallic shell 10 is brought into contact with the rear end-facing end surface 64 of the outer cylinder 60 and joined to the small diameter portion 62 and the flange 63 of the outer cylinder 60 by laser welding L.

  Thereafter, the O-ring 50 and the insulating member 40 are fitted into the gap between the large-diameter hole 15 of the metal shell 10 and the middle shaft 20 from the rear end side of the middle shaft 20 (FIG. 6A). Then, the annular member 70 is placed on the rear end surface of the insulating member 40 (FIG. 6B), pressed toward the distal end in the axial direction, and crimped in the radial direction, as shown in FIG. 6C. The terminal portion 75 is formed with a structure. Thus, the members constituting the glow plug 1 are integrated, and the glow plug is completed.

(Evaluation methods)
Next, a test for verifying the effectiveness of the glow plug of the present embodiment was conducted. For each glow plug with a nominal diameter of M10, M8, and M6 formed on the outer peripheral surface of the metal shell, the center shaft has a diameter of φ4.0 mm, φ3.2 mm, or φ2.4 mm. is doing. Note that the diameter of the central shaft is the diameter of the portion constituting the terminal portion 75. In the conventional example as a comparison object, the pin terminal 170 ′ shown in FIG. 10 forms the terminal portion of the rear end of the glow plug, whereas the embodiment of the present invention is the annular member 70 shown in FIG. It is the structure of the terminal part 75 by. In this evaluation method, a vibration test is performed in an energized state (that is, a heat generation state) in order to verify the durability during use, and this test system is shown in FIG.

  The terminal part 75 of the glow plug to be measured is held by the holder 280 of the vibration tester and fixed so that the glow plug is substantially horizontal. The test condition of the vibration test is that the glow plug is vibrated in the horizontal direction at 2000 Hz and 50 G at room temperature, and the load is applied to the terminal portion 75. A coupler connected to a power source is connected to the terminal portion 75 for power supply, and the ground side is electrically grounded by holding the flange 63 of the outer cylinder 60 from the outer peripheral direction. The supplied power is energized at a DC of 13 V in a cycle of energization 180 seconds-disconnection 60 seconds. This durability test was conducted for 200 hours. In addition, in order to assume the case where the energization to the heat generating part is equivalent to the actual use state, the terminal part 75 is in an insulated state with respect to the holder 280 of the vibration tester.

  After conducting the above-mentioned energization vibration test, 1. Check for breakage of the middle shaft 20 at the rear end. Table 1 shows whether or not the contact resistance between the middle shaft 20 and the annular member 70 or the pin terminal 170 ′ is increased. 1. As for the evaluation of breakage of the middle shaft, the middle shaft 20 is visually checked for cracks and breakage, and “○” indicates that no breakage due to crack or the like has occurred. It is shown. Then, in the middle shaft breakage evaluation, the resistance value was measured for those that were not broken. As shown in FIG. 7B, the resistance value is measured between the terminal portion 75 which is the rear end portion of the middle shaft 20 and the outer cylinder 60 which is grounded when attached to the engine head. did. The criterion for determining that the contact resistance has increased is NG when the initial resistance value (300 mΩ) has increased by 20% or more. In addition, 10 evaluations are performed for each connector shape and each of the middle shafts having the respective middle shaft diameters, and the notation in parentheses in Table 1 indicates the number of occurrences of NG in ten.

  According to this result, it can be seen that even if the pin terminal-shaped connector (170 ′) which is a conventional example has a central axis of φ4.0 mm, no crack is generated in the central axis. However, when the contact resistance is measured, it can be confirmed that some of the contact resistance has increased. Further, in particular, a φ3.2 mm which is a central shaft as applied when the screw diameter of the male screw portion formed on the metal shell is M8, and a φ2.4 mm as applied to M6. And it can be confirmed that the durability of the central shaft itself is insufficient such that the crack occurrence rate of the central shaft is 5 out of 10 and all 10 out of 10. On the other hand, in the case of the connector using the annular member 70 according to the embodiment of the present invention, the occurrence of cracks in the central shaft was not recognized regardless of the central shaft of any diameter. Moreover, even if it measured the contact resistance, there was no thing which contact resistance increased, and it has confirmed that it was favorable in the central axis of any diameter. From this result, it can be confirmed that the effect that the terminal portion 75 is constituted by the annular member 70 is particularly large for the middle shaft used for M8 or less.

  Thus, since the terminal portion 75 is constituted by the annular member 70 and the rear end portion of the middle shaft 20 as compared with the conventional case where the terminal portion 75 is a pin terminal, it becomes possible to relieve stress on the middle shaft 20, and the middle shaft 20 It became possible to avoid breaking.

  In the evaluation test, an increase in the resistance value between the large-diameter portion 71 of the terminal portion 75 and the outer cylinder 60 is measured in order to confirm an increase in contact resistance. It is assumed that the wiring cord 200 including the socket terminal 210 as described in FIG. In particular, the glow plug of the present invention is particularly effective when the portion 220 that is electrically connected to the glow plug has a structure that conducts in contact with the center shaft as in the socket terminal 210 shown in FIG. . In the case of a pin terminal having a conventional connector shape, when the contact resistance has increased as in the above test, the power corresponding to the increased contact resistance is generated between the terminal portion (that is, between the pin terminal 109 and the central shaft 120). However, if the connector is formed of an annular member, not only will the increase in contact resistance be suppressed, but the contact resistance will increase. However, it is possible to configure an electric circuit in which the increased resistance is not interposed in the conduction path from the wiring cord.

FIG. 1 is a half sectional view showing an entire glow plug 1 according to an embodiment of the present invention. FIG. 2 is a view showing a schematic structure in which the glow plug 1 of the present invention is attached to the engine head 300. FIG. 3 is a diagram showing an outline of the manufacturing process of the ceramic heater 30 used in the glow plug 1 of the present invention. FIG. 4 is a diagram showing one step in the process of manufacturing the glow plug 1 of the present invention. FIG. 5 is a diagram showing one step in the process of manufacturing the glow plug 1 of the present invention. FIG. 6 is a diagram showing one step in the process of manufacturing the glow plug 1 of the present invention. FIG. 7 is a diagram showing an experimental system and a measurement system for verifying the effect of the glow plug 1 of the present invention. FIG. 8 is an example showing a use state in which the glow plug 1 of the present invention is particularly effective. FIG. 9 is an example of a conventional glow plug. FIG. 10 is a diagram showing a combination of conventional glow plugs.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Glow plug 10 Metal shell 20 Center shaft 21 Ring member 25 Stress relaxation part 30 Ceramic heater 40 Insulating member 50 O-ring 60 Outer cylinder 70 Annular member

Claims (3)

A rod-shaped ceramic heater in which a heating element that generates heat when energized is housed inside its tip, and
The ceramic heater that has a shaft hole, holds the ceramic heater inserted in the radial direction of the shaft hole so that the tip of the ceramic heater protrudes from the tip surface of the ceramic heater, and is a male screw portion for engine attachment on its outer peripheral surface A cylindrical metal shell formed with
A rod-shaped central shaft for supplying power to the heating element, the rear end portion of the metal shell being disposed so as to protrude from the rear end surface of the metal shell;
A ring member that holds the rear end portion of the ceramic heater and the front end portion of the central shaft and mechanically connects the two;
An annular member disposed between the rear end surface of the metal shell and the rear end portion of the middle shaft in the axial direction and fixed to the middle shaft;
With
A glow plug which is a connector whose rear end is electrically connected to the outside,
A glow plug comprising a connector comprising at least a rear end portion of the central shaft and the annular member. The glow plug according to claim 1, wherein the annular member is made of metal and is crimped in a radial direction to be fixed to the center shaft. The glow plug according to claim 1 or 2, wherein it is M8 or less of a male screw portion formed on the outer peripheral surface of the metal shell.

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