KR20130096667A - Glow plug - Google Patents

Abstract

(Problem) It prevents the sealing member from deteriorating by heat more reliably.
(Solution) The glow plug 1 has a shaft hole 7 extending in the direction of the axis CL1, and is a male screw for screwing into the female screw portion FS formed in the attachment hole HO of the internal combustion engine EN. The cylindrical housing 2 provided with the screw part 8, the ceramic heater 4 inserted in the shaft hole 7 in the state in which at least its front-end part protruded from the front-end | tip of the housing 2, and the axis line CL1. In addition to the rod-shaped extending in the ()) direction, it is provided with a middle shaft (3) which is inserted into the shaft hole (7) to form a conduction path to the ceramic heater (4). An annular sealing member 31 made of an insulating material is disposed between the inner circumference of the housing 2 and the outer circumference of the middle shaft 3 in the forming range of the male screw portion 8 along the axis CL1.

Description

Glow PLUG

The present invention relates to a glow plug for use in preheating of diesel engines.

The glow plugs used for starting assistance of diesel engines have a housing having a shaft hole extending in the axial direction, a heater member inserted into the shaft hole to generate heat by energization, and a rod shape forming a conduction path to the heater member. It is provided with the middle axis of a shape. As the heater member, a ceramic heater having a heating element made of conductive ceramic or a sheath heater having a heating coil made of conductive metal is employed. Moreover, in general, the heater member is press-fitted to the inner circumference of the housing or the tubular member joined to the housing. The housing also has a tool engagement portion at its rear end for engaging the tool when attaching the glow plug to the internal combustion engine.

Further, inside the tool engagement portion, an annular sealing member made of a predetermined insulating material (for example, fluororubber or silicone rubber) is provided between the inner circumference of the housing and the outer circumference of the middle shaft (for example, Patent Document 1). And so on). By providing the sealing member, intrusion of liquid (for example, oil) into the shaft hole can be suppressed. As a result, the insulating property between the shaft hole and the housing can be maintained, and the liquid adheres to the portion fixed to the housing or the like in the heater member, and the liquid adhered by the heat generation of the heater member is carbonized. The occurrence of a short circuit can be suppressed.

Patent Document 1: Japanese Patent Publication No. 2005-315474

By the way, although a glow plug is normally arrange | positioned at the intake side of an internal combustion engine in order to aim at a fall of environmental temperature, it may not be possible to ensure sufficient arrangement space on an intake side, In this case, it is arrange | positioned at the exhaust side of an internal combustion engine. . However, when the glow plug is disposed on the exhaust side of the internal combustion engine, the tool engagement portion and its vicinity in the housing are exposed to a high temperature of about 250 ° C due to the influence of radiant heat and heat transfer from the exhaust manifold, turbocharger, and the like. Can be. Therefore, there exists a possibility that deterioration by heat (decrease of elasticity by generation | occurrence | production of a compression set) may generate | occur | produce in the sealing member arrange | positioned inside a tool engagement part.

In order to prevent deterioration of the sealing member by heat, it is conceivable to form the sealing member by a special material having excellent heat resistance (for example, Calleze (trademark) manufactured by DuPont). However, even when such a material having excellent heat resistance is applied to the sealing member, when used in an environment where it is exposed to a high temperature atmosphere for a long time like a glow plug, there is a fear that the compression set becomes large and airtightness may not be secured.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a glow plug which can more reliably prevent deterioration of a sealing member due to heat.

Hereinafter, each item suitable for solving the said objective is divided and demonstrated. Moreover, if necessary, the effect peculiar to a corresponding structure is added.

Configuration 1. The glow plug of the present configuration has a shaft hole extending in the axial direction and is located at a rear end side of the male screw portion for screwing into a female screw portion formed in the attachment hole of the internal combustion engine and the internal combustion engine. A cylindrical housing having a tool engagement portion to which the tool is engaged when attached to the

A heater member inserted into the shaft hole at least with its tip protruding from the tip of the housing;

A glow plug having a rod-shape extending in the axial direction and having a middle shaft inserted into the shaft hole to form a conduction path to the heater member,

An annular sealing member made of an insulating material is disposed between the inner circumference of the housing and the outer circumference of the intermediate shaft in the formation range of the male screw portion along the axis.

According to the said structure 1, the sealing member is comprised so that it may be arrange | positioned between a housing and a middle shaft in the formation range of a male screw part along an axis line. Therefore, the sealing member can be kept at a position spaced apart from the tool engagement portion that can be at a high temperature, thereby suppressing the temperature of the sealing member sufficiently low.

In addition, since the internal combustion engine is generally cooled by a coolant or the like, the male thread portion in contact with the internal combustion engine (female threaded portion) in the housing and its vicinity are sufficiently low (for example, 100) even in an environment where the tool engagement portion becomes extremely high. Or less). For this reason, the sealing member located inside the screw part can suppress the temperature further.

As mentioned above, according to the said structure 1, since the said effect is acting synergistically, deterioration of the sealing member by heat can be prevented more reliably.

Configuration 2. The glow plug of this configuration is characterized in that the sealing member is positioned in the formation range of the female screw portion along the axis in the state of screwing the male screw portion to the female screw portion in the configuration 1 above.

According to the said structure 2, it is comprised so that a sealing member may be located inside a female screw part in the state which screwed the male screw part with respect to the female screw part formed in the internal combustion engine (that is, the state which attached the glow plug to the internal combustion engine). Therefore, the heat of the tool engagement portion is less likely to be transmitted to the sealing member, and the outer circumference of the housing contacts the female screw portion (internal combustion engine), whereby a portion at a lower temperature comes into contact with the sealing member. Thereby, the temperature of a sealing member can be suppressed lower, and the deterioration of a sealing member by heat can be prevented more effectively.

Configuration 3. The glow plug of this configuration is located in the axially distal end side of the housing in the inner circumference of the housing in the range of formation of the male screw portion along the axis in the configuration 1 above. It characterized in that the stepped portion is formed to protrude.

According to the said structure 3, the movement of the sealing member toward the front end side rather than a step part can be regulated. Therefore, the original function of the sealing member of ensuring airtightness can be exhibited more reliably.

Configuration 4. The glow plug of this configuration is the configuration 3, wherein the housing,

A large diameter portion in which the sealing member is in contact with its inner circumference,

It is provided in the said axial direction tip side rather than the said large diameter part, and is provided with the small diameter part whose internal diameter is smaller than the internal diameter of the said large diameter part,

The step portion is constituted by a portion connecting the tip of the large diameter portion and the rear end of the small diameter portion,

The stepped portion is formed at the rear end side of the axial direction at least three times the screw pitch of the male screw portion at the tip of the complete screw portion in the male screw portion.

In addition, a "full threaded part" means a threaded part in which both the top of the mountain and the bottom of the valley have a perfect mountain shape.

In the state where the glow plug is attached to the internal combustion engine, axial force is applied to a portion located at the tip side of the housing than the male screw portion and a portion located near the portion of the male screw portion. Therefore, it is preferable that the portion to which axial force can be applied in the housing has excellent mechanical strength in order to prevent deformation due to axial force.

In view of this point, according to the configuration 4, the stepped portion is formed at the rear end side in the axial direction by three times or more the screw pitch of the male threaded portion than the fully threaded end of the male screwed portion. That is, the large diameter portion that is larger than the small diameter portion and may be relatively thin is formed at a position deviated from the area where the axial force may be applied, and the small diameter portion that is smaller than the large diameter portion and may be relatively thick may apply the axial force. It is formed at the position. Therefore, the mechanical strength in the site | part to which an axial force can be applied in a housing can fully be ensured. As a result, deformation of the housing can be prevented more reliably.

Configuration 5. The glow plug of this configuration is located in the axially distal end side of the middle shaft in the outer periphery of the middle shaft in the formation range of the male screw portion along the axis in the configuration 1, and toward the radially outer side. It is characterized in that the protruding protrusions are formed.

According to the said structure 5, the movement of the sealing member to the front end side rather than a projection part can be regulated. Therefore, the function of ensuring airtightness by a sealing member can be exhibited more reliably.

Configuration 6. The glow plug of this configuration is the configuration 1 or 2, wherein the sealing member is made of an insulating elastic material,

In the cross section of the said sealing member containing the central axis of the said sealing member, before arrange | positioning between the inner periphery of the said housing and the outer periphery of the said intermediate shaft,

The outline of the cross section of the sealing member is

A first outline which is located on the outer circumferential side and which forms a curved shape which is raised outward in the radial direction,

It is located on the inner circumferential side and has a curved shape that is raised in the radial direction in a state in which its radius of curvature is larger than the radius of curvature of the first outline, or has two outlines that form a straight line along the central axis of the sealing member. It is characterized by.

According to the said structure 6, when the sealing member is pushed in between a housing | casing and a middle shaft, the site | part which comprises a 2nd outline of a sealing member supports the whole sealing member, and is a core which suppresses the curvature and sinking. Function. Therefore, it is possible to more reliably prevent the occurrence of bending and wrinkles in the inner circumferential surface of the sealing member in contact with the middle axis, and more reliably contact the inner circumferential surface of the sealing member against the middle axis. As a result, the sealing property between a sealing member and a middle axis can be improved more.

In addition, when the sealing member is press-fitted between the housing and the middle shaft, the sealing member is compressed along the radial direction, but according to the above configuration 6, since the first outline is a curved shape that rises radially outward, the sealing member Deformation by compression can be performed smoothly.

Moreover, by making a 1st outline line into a curved shape, the sealing member deform | transforms so that a large part may move to the small part of thickness in thickness along the radial direction at the time of the deformation | transformation. Therefore, in the sealing member disposed between the housing and the middle shaft, it is difficult to produce a deformation site having a high internal stress locally. As a result, it is possible to more reliably prevent damage (cutting) of the sealing member due to internal stress when the glow plug is subjected to vibration or the like from the outside.

1 is a front view showing the configuration of a glow plug;
2 is a cross-sectional view showing the configuration of a glow plug;
3 is a cross-sectional view of the sealing member before being disposed between the housing and the middle shaft;
4 is a cross-sectional view showing another example of a sealing member before being disposed between the housing and the middle shaft;
5 is an enlarged cross-sectional view of a housing or the like showing the configuration of a stepped portion or the like;
6 is an enlarged cross-sectional view showing a glow plug attached to an internal combustion engine;
FIG. 7 is a cross-sectional view showing a projection formed on the central shaft and the like in another embodiment. FIG.

EMBODIMENT OF THE INVENTION Hereinafter, one Embodiment is described, referring drawings. 1 is a front view of the glow plug 1, and FIG. 2 is a cross-sectional view of the glow plug 1. In addition, in FIG. 1, 2 etc., the lower side of drawing is made into the front end side of the glow plug 1, and the upper side is demonstrated to the rear end side.

As shown in FIG. 1 and FIG. 2, the glow plug 1 includes a housing 2, a middle shaft 3, a ceramic heater 4 as a heater member, an outer cylinder 5, a terminal pin 6, and the like. Equipped with.

The housing 2 is formed in a tubular shape by a predetermined metal material (for example, an iron-based material such as S45C), and has a shaft hole 7 extending along the axis CL1 direction. Moreover, the male screw part 8 for attaching the glow plug 1 to the female screw part formed in the attachment hole of the internal combustion engine is formed in the outer periphery of the center part of the housing 2 in the axial line CL1 direction. In addition, a tool engaging portion 9 having a hexagonal cross section is formed on the outer circumference of the rear end of the housing 2, and when the male screw portion 8 is screwed into the female screw portion, the tool engaging portion 9 is formed. The attachment tool is engaged with the. Moreover, in this embodiment, it is comprised so that the thickness of the housing | casing 2 may be below a predetermined value (for example, 1.7 mm) in the curved part of the male screw part 8.

In addition, the shaft shaft 7 of the housing 2 accommodates the above-mentioned intermediate shaft 3, which is made of metal and has a round rod shape. The intermediate shaft 3 has a solid shape, and is configured to have a constant outer diameter along the axis CL1 in the present embodiment. In addition, the front end of the middle shaft 3 is joined (for example, welded) to the rear end of the cylindrical connecting member 10 formed of a conductive metal material (for example, an iron-based material such as SUS). The rear end of the ceramic heater 4 is press-fitted to the front end of the connecting member 10. As a result, the middle shaft 3 and the ceramic heater 4 are mechanically and electrically connected via the connecting member 10.

In addition, the terminal pin 6 made of metal is fixed to the rear end of the middle shaft 3, and the direct current (short circuit) between the front end of the terminal pin 6 and the rear end of the housing 2 is fixed. In order to prevent this, an insulating bush 11 made of an insulating material is provided.

In addition, the said outer cylinder 5 is formed in the tubular shape by the predetermined metal material, and is joined to the front-end | tip part of the housing 2. Moreover, the outer cylinder 5 supports the intermediate part along the axis line CL1 direction of the ceramic heater 4, and the front-end | tip part of the ceramic heater 4 is in the state exposed at the front-end | tip of the outer cylinder 5. As shown in FIG. Moreover, the outer cylinder 5 is equipped with the taper-shaped press-contact part 5A which outer diameter becomes small gradually toward the front end side in the axial line CL1 direction on the outer periphery. When attaching the glow plug 1 to the internal combustion engine, the press contact portion 5A is press-contacted with a taper sheet formed in the internal combustion engine to ensure airtightness in the combustion chamber. Moreover, the outer cylinder 5 is joined to the housing 2 by carrying out laser welding along the edge of the contact surface between itself and the housing 2 in a state where the rear end thereof is inserted into the shaft hole 7.

The ceramic heater 4 includes a round rod-shaped base 21 extending in the direction of the axis CL1, and a heat generating element 22 embedded therein and having an elongated 'U' shape. The base 21 is made of an insulating ceramic (for example, silicon nitride, alumina, etc.), and the heat generating element 22 has silicon nitride as a main component, but a conductive material (for example, molybdenum, tungsten carbide, or silicide) And the like).

In addition, the heat generating element 22 includes a heat generating portion 23 disposed at the distal end of the ceramic heater 4 and a pair of rod-shaped lead portions 24 extending from the distal end of the heat generating portion 23 toward the rear end side. And 25). The heat generating portion 23 is a portion that functions as a so-called heat generating resistor, and forms a 'U' shape along the curved surface at the tip portion of the ceramic heater 4 formed in a curved shape.

Further, the lead portions 24 and 25 are formed to extend substantially parallel to each other toward the rear end side of the ceramic heater 4, respectively. In the vicinity of the rear end of the lead portion 24 on one side, an electrode extraction portion 26 protrudes in the outer circumferential direction, and the electrode extraction portion 26 is exposed on the outer peripheral surface of the ceramic heater 4. Similarly, the electrode extraction portion 27 protrudes in the outer circumferential direction at a position near the rear end of the lead portion 25 on the other side, and the electrode extraction portion 27 is exposed on the outer circumferential surface of the ceramic heater 4. The electrode lead-out portion 26 of the lead portion 24 on the one side is located on the rear end side of the electrode lead-out portion 27 of the lead portion 25 on the other side along the axis CL1 direction.

In addition, the exposed portion of the electrode lead-out portion 26 is in contact with the inner circumferential surface of the connecting member 10, and electrical conduction between the intermediate shaft 3 and the lead portion 24 connected to the connecting member 10 is achieved. In addition, the exposed portion of the electrode extraction portion 27 is in contact with the inner circumferential surface of the outer cylinder 5, and electrical conduction between the housing 2 and the lead portion 25 joined to the outer cylinder 5 is achieved. That is, in this embodiment, the middle shaft 3 and the housing 2 function as an anode and a cathode for energizing the heat generating section 23 of the ceramic heater 4.

Moreover, in order to ensure the airtightness in the axial hole 7, the annular sealing member 31 which consists of an insulating elastic material (for example, fluororubber, a silicone rubber, etc.) between the housing | casing 2 and the intermediate shaft 3 is carried out. Is installed. In this embodiment, the sealing member 31 is provided between the inner periphery of the housing 2 and the outer periphery of the intermediate shaft 3 in the formation range RA of the male screw part 8 along the axis CL1. In addition, the sealing member 31 is provided in the shaft hole 7 by assembling the housing 2 and the intermediate shaft 3 and the like, and then pressing them in between them.

In addition, in this embodiment, as shown in FIG. 3, the center of the sealing member 31 which passes through the inner periphery of the sealing member 31 before arrange | positioning between the inner periphery of the housing 2 and the outer periphery of the intermediate shaft 3 is shown. In the cross section of the sealing member 31 including the shaft CL2, located on the outer circumferential side in the outline OL of the cross section of the sealing member 31 (that is, in contact with the inner circumference of the housing 2). The first outline OL1 has a curved shape that rises radially outward. On the other hand, the second outline OL2 located on the inner circumferential side (that is, in contact with the outer circumference of the middle axis 3) in the outline OL of the cross section forms a straight line along the central axis CL2. have.

In addition, as shown in FIG. 4, in the said cross section, radial direction inner side of the 2nd outline line OL2 in the state whose curvature radius R2 is larger than the curvature radius R1 of the 1st outline line L1. You may comprise so that the curved shape which may raise may be made.

In addition, as shown in FIG. 5, the housing 2 has a tip in the direction of the axis CL1 relative to the large diameter portion 32 and the large diameter portion 32 in which the sealing member 31 contacts the inner circumference thereof. It is located in the side, but is provided with the small diameter part 33 whose inner diameter is smaller than the inner diameter of the large diameter part 32. As shown in FIG. In this embodiment, the outer diameter of the large diameter part 32 and the outer diameter of the small diameter part 33 are made substantially the same, and the thickness of the small diameter part 33 becomes thicker than the thickness of the large diameter part 32. As shown in FIG.

In addition, the stepped portion protruding inwardly in the radial direction is located at the distal end of the large diameter portion 32 and the rear end of the small diameter portion 33 at the distal end side of the sealing member 31 in the axial line CL1 direction ( 34) is formed. The stepped portion 34 is formed in the forming range RA of the male screw portion 8 along the axis CL1. In this embodiment, the male screw portion 8 is formed at the tip of the complete screw portion of the male screw portion 8. Is formed on the rear end side in the direction of the axis line CL1 at least three times the screw pitch. In other words, in the state where the glow plug 1 is attached to the internal combustion engine, the relatively large diameter portion 32 is located on the rear end side than the position where the axial force along the axis CL1 direction is applied, and the axial force It is comprised so that the small diameter part 33 which is comparatively thick and excellent in intensity | strength to a position to be applied is located.

In addition, in this embodiment, as shown in FIG. 6, in the state which screwed the male screw part 8 to the female screw part FS of the attachment hole HO formed in the engine head EH of the internal combustion engine EN, The arrangement position of the sealing member 31 is set so that the sealing member 31 may be located in the formation range of the female screw part FS along the said axis line CL1. In addition, the engine head EH is cooled by a coolant or the like, and the male screw portion 8 and its vicinity in contact with the engine head EH in the housing 2 are sufficiently low even when the internal combustion engine EN operates. For example, 100 degrees C or less) is comprised.

In addition, in this embodiment, the glow plug 1 is arrange | positioned at the exhaust side of the internal combustion engine EN. For this reason, the tool engagement part 9 which protrudes from the engine head EH in the housing 2 by the influence of radiant heat and heat transfer in an exhaust manifold, a turbocharger, etc., and its vicinity are about 250 degreeC. Can be high temperature.

As mentioned above, according to this embodiment, the sealing member 31 is arrange | positioned between the housing 2 and the intermediate shaft 3 in the formation range of the male screw part 8 along the axis CL1. Therefore, the sealing member 31 can be restrained from the tool engagement part 9 which can become high temperature in the position separated from the temperature of the sealing member 31 low enough.

In addition, since the engine head EH is cooled by a coolant or the like, the male screw portion 8 and the vicinity of the male screw portion 8 in contact with the internal combustion engine EN (female thread portion FS) in the housing 2 have a tool engagement portion 9. Even if the environment becomes extremely high temperature, the temperature is sufficiently low (for example, 100 ° C. or less). Therefore, in the sealing member 31 located inside the male screw part 8, temperature can be suppressed further.

As described above, according to the present embodiment, the above-described effect works synergistically, whereby deterioration of the sealing member 31 due to heat can be prevented more reliably.

Further, the sealing member inside the female screw portion FS in a state where the male screw portion 8 is screwed to the female screw portion FS (that is, the glow plug 1 is attached to the internal combustion engine EN). 31 is comprised so that it may be located. Therefore, the heat of the tool engagement portion 9 is less likely to be transmitted to the sealing member 31, and the outer circumference of the housing 2 contacts the female screw portion FS (internal combustion engine EN). The lower temperature portion comes into contact with the sealing member 31. For this reason, the temperature of the sealing member 31 can be further suppressed, and deterioration of the sealing member 31 by heat can be prevented more effectively.

In addition, the movement of the sealing member 31 toward the distal end side can be restricted by the step portion 34 formed on the inner circumference of the housing 2. Therefore, the original function of the sealing member 31 of ensuring airtightness can be exhibited more reliably.

In addition, in this embodiment, the inside diameter is larger than the small diameter part 33, and the comparatively thin large diameter part 32 is formed in the position away from the site to which axial force can be applied, and the internal diameter is smaller than the large diameter part 32, and is comparatively small The neck portion 33 is formed at a position where axial force can be applied. Therefore, the mechanical strength in the site | part to which axial force can be applied in the housing | casing 2 can fully be ensured. As a result, deformation of the housing 2 can be prevented more reliably.

In addition, in this embodiment, it is comprised so that 2nd outline line OL2 in the sealing member 31 may form a linear shape or a gentle curved shape. Accordingly, when the sealing member 31 is press-fitted between the housing 2 and the middle shaft 3, the portion of the sealing member 31 constituting the second outline OL2 supports the entire sealing member 31. It functions as a core which suppresses the bending and sinking. Therefore, it is possible to more reliably prevent the occurrence of bending or wrinkles in the inner circumferential surface of the sealing member 31 in contact with the middle shaft 3, and more reliably prevents the inner circumferential surface of the sealing member 31 from the middle shaft 3. Can be contacted. As a result, the sealing property between the sealing member 31 and the intermediate shaft 3 can be improved more.

Moreover, the 1st outline OL1 is made into the curved shape which protrudes radially outward. For this reason, the deformation | transformation by compression of the sealing member 31 can be performed smoothly. In addition, the sealing member 31 is deformed so that at the time of its deformation, a portion having a large thickness in the radial direction moves to a portion having a small thickness. Therefore, in the sealing member 31 disposed between the housing 2 and the middle shaft 3, it is difficult to produce a deformation site having a high internal stress locally. As a result, damage (cutting) of the sealing member 31 due to internal stress when the glow plug 1 is subjected to vibration or the like from the outside can be prevented more reliably.

In addition, in this embodiment, since the thickness of the housing | casing 2 is below a predetermined value in the curved part of the male screw part 8, the male screw part 8 with respect to the quantity of heat transmitted to the male screw part 8 is carried out. The amount of heat transmitted to the internal combustion engine EN can be increased, and the male screw portion 8 and its vicinity become sufficiently low. Therefore, the temperature of the sealing member 31 can be suppressed more reliably low, and the deterioration of the sealing member 31 by heat can be prevented effectively. In addition, by reducing the thickness of the housing 2 to a predetermined value, it is possible to reduce the weight of the glow plug 1, thereby improving fuel efficiency and reducing material costs.

In addition, it is not limited to the description content of the said embodiment, For example, you may carry out as follows. Of course, other application examples and modification examples which are not illustrated below are naturally possible.

(a) In the above embodiment, the sealing member 31 is disposed at the rear end side in the direction of the axis CL1 by at least three times the screw pitch of the male screw portion 8 than the tip of the male screw portion 8, but the sealing member ( The arrangement position of 31 is not limited to this, The sealing member 31 should just be arrange | positioned in the formation range RA of the male screw part 8 along the axis CL1.

(b) The cross-sectional shape of the sealing member 31 before placing between the inner periphery of the housing 2 and the outer periphery of the intermediate shaft 3 is not specifically limited. Therefore, for example, before arrange | positioning between the inner periphery of the housing 2 and the outer periphery of the intermediate shaft 3, you may comprise so that the cross-sectional shape of the sealing member 31 may have circular shape or rectangular shape.

(c) In the said embodiment, in order to regulate the movement to the front end side of the sealing member 31, the step part 34 is formed in the inner periphery of the housing 2. As shown in FIG. On the other hand, as shown in FIG. 7, in the formation range of the male screw part 8 along the axis line CL1, it is located in the outer side of the middle axis 3 rather than the sealing member 31 in the front end side of the axis line CL1 direction, and has a diameter. The protrusion part 35 which protrudes toward a direction outer side may be formed. Also in this case, movement to the front end side of the sealing member 31 can be regulated similarly to the case where the step part 34 is formed. In this case, the projection part 35 may be formed at the front end side of the male screw section 8 by three times the screw pitch of the male screw section 8 at the front end side in the axial CL1 direction rather than the position at the rear end side. In addition, by providing both the step portion 34 and the protrusion 35, the effect of restricting the movement of the sealing member 31 may be increased.

(d) In the above embodiment, the technical idea of the present invention is applied to the glow plug 1 (so-called ceramic glow plug) having the ceramic heater 4 as the heater member. However, the glow plug to which the technical idea of this invention is applicable is not limited to this. Therefore, for example, the technical idea of the present invention may be applied to a glow plug (so-called metal glow plug) provided with a sheath heater having a heating coil made of a conductive metal as a heater member.

(e) In the above embodiment, the glow plug 1 is disposed on the exhaust side of the internal combustion engine EN, but the glow plug 1 may be disposed on the intake side of the internal combustion engine EN. That is, the arrangement position of the glow plug 1 with respect to the internal combustion engine EN is not specifically limited.

(f) In the above embodiment, the middle shaft 3 is configured to have a constant outer diameter along the axis CL1, but the outer diameter gradually narrows toward the distal end side of the middle shaft 3 toward the distal end side. It is also possible to form a necked neck. In this case, stress relaxation and the like transmitted from the middle shaft 3 to the ceramic heater 4 can be achieved. In addition, it is preferable to form the necking at the front end side rather than the step | step part 34 and the protrusion part 35. FIG.

(g) In the above embodiment, the intermediate shaft 3 and the ceramic heater 4 are electrically connected through the connecting member 10, but the intermediate shaft 3 and the ceramic heater 4 are electrically connected by a predetermined lead wire or the like. May be connected.

(h) The shape of the ceramic heater 4 is not specifically limited, For example, an elliptical cross section shape, an elliptical cross section shape, and a polygonal cross section shape may be sufficient. As the ceramic heater, a so-called plate heater in which a heat generating element is sandwiched between a plurality of bases each forming a plate shape may be used.

1-glow plug 2-housing
3-Medium Axis 4-Ceramic Heater (Heater)
7-Axial hole 8-Male thread
9-tool engagement 31-sealing member
32-Large diameter 33-Small diameter
34-stepped part 35-protrusion
CL1-axis CL2-center axis (of sealing member)
EN-internal combustion engine FS-female thread
HO-Mounting Hole OL-Outline
OL1-first contour line OL2-second contour line

Claims (6)

In addition to having an axial hole extending in the axial direction, a male screw portion for screwing into a female screw portion formed in an attachment hole of the internal combustion engine and a rear end portion of the male screw portion to be engaged with the tool when attached to the internal combustion engine. A cylindrical housing having a tool engagement portion;
A heater member inserted into the shaft hole at least with its tip protruding from the tip of the housing;
A glow plug having a rod shape extending in the axial direction and having a middle axis inserted into the shaft hole to form a conduction path to the heater member,
A glow plug according to the axis, wherein an annular sealing member made of an insulating material is disposed between the inner circumference of the housing and the outer circumference of the middle shaft.
The method according to claim 1,
The glow plug, wherein the sealing member is positioned in a range of formation of the female screw portion along the axis in the state of screwing the male screw portion to the female screw portion.
The method according to claim 1,
The glow plug according to the above-mentioned axis line, wherein the inner circumference of the housing is provided with a step portion which is located at the distal end side in the axial direction than the sealing member and protrudes radially inward.
The method according to claim 3,
The housing includes:
A large diameter portion in which the sealing member is in contact with its inner circumference,
It is provided in the said axial direction tip side rather than the said large diameter part, and is provided with the small diameter part whose internal diameter is smaller than the internal diameter of the said large diameter part,
The step portion is constituted by a portion connecting the tip of the large diameter portion and the rear end of the small diameter portion,
And the stepped portion is formed at the rear end side of the axial direction at least three times the screw pitch of the male threaded portion at the tip of the complete threaded portion of the male threaded portion.
The method according to claim 1,
The glow plug according to the above-mentioned axis line, wherein the outer circumference of the middle shaft is provided with a projection which is located at the distal end side of the axial direction rather than the sealing member and protrudes outward in the radial direction.
The method according to claim 1 or 2,
The sealing member is made of an insulating elastic material,
In the cross section of the said sealing member containing the central axis of the said sealing member, before arrange | positioning between the inner periphery of the said housing and the outer periphery of the said intermediate shaft,
The outline of the cross section of the sealing member is
A first outline which is located on the outer circumferential side and which forms a curved shape which is raised outward in the radial direction,
It is located on the inner circumferential side and has a curved shape that is raised in the radial direction in a state in which its radius of curvature is larger than the radius of curvature of the first outline, or has two outlines that form a straight line along the central axis of the sealing member. It is characterized by.

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