JP5829879B2 - Ceramic glow plug and its assembly structure - Google Patents

Description

  The present invention relates to a ceramic glow plug used for preheating or the like of a diesel engine, and an assembly structure thereof.

  2. Description of the Related Art Conventionally, glow plugs used for diesel engine start-up assistance and the like include a cylindrical housing and a heater incorporating a heating element that generates heat when energized. Moreover, a ceramic heater may be employed as the heater.

  The ceramic heater is configured by housing a heat-generating ceramic heater element in a cylindrical base made of an insulating ceramic. In the glow plug having such a ceramic heater, the outer periphery of the intermediate portion of the ceramic heater is generally held by a cylindrical outer cylinder, and the outer cylinder is fixed to the housing ( For example, see Patent Document 1).

  Further, the outer peripheral surface of the outer cylinder is provided with a pressure contact portion that comes into pressure contact with the taper sheet of the engine head when the glow plug is assembled to the internal combustion engine (engine), and the pressure contact portion and the taper sheet are in close contact with each other. As a result, airtightness in the combustion chamber is ensured.

JP 2002-364842 A

  By the way, the housing may be made of stainless steel. In this case, when the glow plug is assembled to the internal combustion engine, the pressure contact portion is rubbed against the taper sheet, so that the pressure contact portion is deformed. (The press contact part may be damaged). If the pressure contact portion is deformed, the adhesion between the pressure contact portion and the taper sheet is impaired, and the airtightness in the combustion chamber may be reduced.

  In addition, the metal glow plug having a sheath heater including a metal heating resistor as the heater has a configuration in which airtightness is ensured by a pressure contact portion provided on the outer peripheral surface of its own housing being in close contact with the taper sheet. However, in the metal glow plug, a clearance can be formed between the outer peripheral surface of the sheath heater and the inner peripheral surface of the housing that holds the sheath heater at least inside the press contact portion. For this reason, when assembled to the internal combustion engine, the stress applied to the pressure contact portion due to the presence of the clearance is relieved, and deformation of the pressure contact portion is prevented. On the other hand, in a general ceramic glow plug, at least the surface of the outer cylinder located on the inner peripheral side of the press contact portion and the outer peripheral surface of the ceramic heater are in close contact. Therefore, at the time of assembly to the internal combustion engine, the stress applied to the press contact portion is not alleviated, and the press contact portion is likely to be deformed. That is, particularly in a ceramic glow plug, there is a concern about deformation of the pressure contact portion during assembly to the internal combustion engine.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an internal combustion engine in a ceramic glow plug in which at least a surface located on the inner peripheral side of a press contact portion of an outer cylinder is in close contact with an outer peripheral surface of a ceramic heater. It is an object of the present invention to provide a ceramic glow plug that can suppress deformation of the press-contact portion when assembled to the end, and that can more reliably prevent a decrease in hermeticity, and an assembly structure thereof.

  Hereinafter, each configuration suitable for solving the above-described object will be described in terms of items. In addition, the effect specific to the corresponding structure is added as needed.

Configuration 1. The ceramic glow plug of this configuration has an axial hole extending in the axial direction, and a cylindrical housing having a threaded portion for screwing into an attachment hole of the internal combustion engine on the outer peripheral surface;
A substrate made of an insulating ceramic, and a ceramic heater having a heating element made of a conductive ceramic and embedded in the substrate;
A cylindrical outer cylinder fixed to the front end of the housing and holding the outer periphery of the ceramic heater on its inner periphery;
The outer cylinder is made of stainless steel,
A small-diameter portion located on the tip side in the axial direction;
A larger diameter portion located on the rear end side in the axial direction than the smaller diameter portion, and having a larger diameter than the smaller diameter portion,
A ceramic glow plug that is located between the small diameter portion and the large diameter portion and has a pressure contact portion that presses against a taper sheet of the internal combustion engine when the screw portion is screwed into a mounting hole of the internal combustion engine. Because
Of the outer cylinder, at least the surface located on the inner peripheral side of the pressure contact portion is in close contact with the outer peripheral surface of the ceramic heater,
The outer cylinder includes a friction force reducing means for reducing a friction force generated between the tapered sheet and the press contact portion when the screw portion is screwed into a mounting hole of the internal combustion engine. .

  According to the above configuration 1, the outer cylinder is provided with the friction force reducing means, and when the screw portion is screwed into the mounting hole of the internal combustion engine by the friction force reducing means (that is, the glow plug is connected to the internal combustion engine). The frictional force generated between the press contact portion and the taper sheet can be reduced. Therefore, in the ceramic glow plug in which at least the surface of the outer cylinder located on the inner peripheral side of the press contact portion is in close contact with the outer peripheral surface of the ceramic heater, and the press contact portion is liable to be deformed when assembled to the internal combustion engine. Can be effectively suppressed. As a result, it is possible to more reliably prevent a decrease in airtightness in the combustion chamber.

  In addition, as a frictional force reduction means, the structures 2-4 mentioned later are employable, for example.

  Configuration 2. The ceramic glow plug of this configuration is characterized in that, in the above configuration 1, the frictional force reducing means is a plating that the press contact portion has on its surface.

  As in the above configuration 2, the frictional force reducing means may be realized by plating provided on the surface of the press contact portion. In this case, the frictional force generated between the pressure contact portion and the taper sheet can be more reliably reduced, and deformation of the pressure contact portion can be more effectively suppressed.

  In addition, it is preferable that the thickness of the plating is 10 μm or more so that the effect of reducing the frictional force can be more reliably exhibited.

  Configuration 3. The ceramic glow plug of this configuration is the above-described configuration 1, wherein the frictional force reducing means is formed on the outer periphery of the outer cylinder and extends along the circumferential direction of the outer cylinder, and is inserted into the mounting hole of the internal combustion engine. It is a groove part which makes it possible to change the pressure contact part toward the rear end side in the axial direction when the screw part is screwed together.

  Like the said structure 3, it is good also as a frictional force reduction means being implement | achieved by the groove part provided in the outer periphery of an outer cylinder. In this case, a reaction force is applied from the taper sheet by screwing at the time of assembly to the internal combustion engine, but the pressure contact portion is deformed toward the rear end side in the axial direction due to the presence of the groove portion, so that the pressure contact portion is changed from the taper sheet. The stress applied to can be relaxed. As a result, the frictional force generated between the press contact portion and the taper sheet can be effectively reduced, and deformation of the press contact portion (scratching of the press contact portion) can be more reliably prevented.

Configuration 4. The ceramic glow plug of this configuration is the above configuration 1, wherein the frictional force reducing means is:
The plating provided on the surface of the pressure contact portion;
It is formed on the outer periphery of the outer cylinder and extends along the circumferential direction of the outer cylinder, and when the threaded portion is screwed into the mounting hole of the internal combustion engine, the pressure contact portion is directed toward the rear end in the axial direction. And a groove portion that can be deformed.

As in the configuration 4, the frictional force reducing means may be realized by both the plating and the groove. In this case, the frictional force generated between the pressure contact portion and the taper sheet can be extremely effectively reduced, and as a result, deformation of the pressure contact portion can be prevented more reliably.
Configuration 5. The ceramic glow plug of this configuration is characterized in that, in the above configuration 1, the frictional force reducing means is a coating provided on the surface of the press contact portion.
According to the said structure 5, the effect similar to the said structure 1 is show | played.

Configuration 6 . Assembly structure of a ceramic glow plug of the present configuration, the ceramic glow plug any crab described above configurations 1 to 5, a assembly structure of a ceramic glow plug formed by assembling an internal combustion engine,
Of the taper sheet of the internal combustion engine, at least a portion where the pressure contact portion is pressure-contacted is formed of a metal having iron (Fe) as a main component.

As in the above configuration 6, in the case where the press contact portion of the taper sheet is formed of a metal mainly composed of Fe, the deformation of the press contact portion during assembly to the internal combustion engine is more concerned. However, the concern can be eliminated by adopting the configuration 1 or the like. In other words, the ceramic glow plug of the above configuration 1 or the like is particularly significant when used in an internal combustion engine in which a portion of the taper sheet that is press-contacted by the press-contact portion is made of a metal whose main component is Fe.

(A) is sectional drawing which shows the structure of a glow plug, (b) is a front view which shows the structure of a glow plug. It is a partial expanded sectional view which shows the front-end | tip part of a glow plug. It is a cross-sectional schematic diagram which shows the state which assembled | attached the glow plug to the internal combustion engine. It is a partial expanded sectional view of the press-contact part etc. which show plating. It is a partial expanded sectional view which shows the structure of the outer cylinder etc. in 2nd Embodiment. In 2nd Embodiment, it is a cross-sectional schematic diagram which shows the state which assembled | attached the glow plug to the internal combustion engine. (A) is an enlarged cross-sectional schematic diagram which shows the press-contact part etc. in the middle of inserting the glow plug with respect to an attachment hole, (b) is the press-contact part in the state which assembled | attached the glow plug to the internal combustion engine. FIG.

Embodiments will be described below with reference to the drawings.
[First Embodiment]
FIG. 1A is a longitudinal sectional view of a ceramic glow plug (hereinafter referred to as “glow plug”) 1, and FIG. 1B is a front view of the glow plug 1. FIG. 2 is a partially enlarged cross-sectional view centering on the ceramic heater 4. In FIGS. 1 and 2, the lower side of the figure will be described as the front end side of the glow plug 1, and the upper side will be described as the rear end side.

  As shown in FIGS. 1A and 1B, the glow plug 1 includes a housing 2, a middle shaft 3, a ceramic heater 4, an outer cylinder 5, a terminal pin 6, and the like.

  The housing 2 is made of a predetermined metal material (for example, an iron-based material such as carbon steel such as S45C or stainless steel), and has a shaft hole 7 extending along the direction of the axis CL1. Furthermore, a screw portion 8 for assembling the glow plug 1 to the mounting hole of the internal combustion engine is formed on the outer periphery of the central portion in the longitudinal direction of the housing 2. In addition, a hook-shaped tool engaging portion 9 having a hexagonal cross section is formed on the outer periphery of the rear end portion of the housing 2. When the glow plug 1 (screw portion 8) is assembled to the internal combustion engine, A tool used in the tool engaging portion 9 is engaged.

  The shaft hole 7 of the housing 2 accommodates the middle shaft 3 made of a metal and having a round bar shape with a clearance from the inner peripheral surface of the housing 2. The front end portion of the middle shaft 3 is fitted into the rear end portion of the cylindrical connection member 10 formed of a metal material (for example, an iron-based material such as SUS), and the front end portion of the connection member 10 The rear end portion of the ceramic heater 4 is fitted. Thereby, the middle shaft 3 and the ceramic heater 4 are mechanically and electrically connected via the connection member 10. Note that a constricted portion 13 whose outer diameter is narrowed toward the distal end side is formed on the distal end side of the intermediate shaft 3, and stress transmitted to the intermediate shaft 3 is relaxed by the constricted portion 13.

  Further, a metal terminal pin 6 is fixed by caulking to the rear end portion of the middle shaft 3. Further, an insulating bush 11 made of an insulating material is provided between the front end portion of the terminal pin 6 and the rear end portion of the housing 2 in order to prevent direct electrical conduction between the two. . Further, an O-ring 12 made of an insulating material is provided between the housing 2 and the middle shaft 3 so as to contact the tip of the insulating bush 11 in order to improve the airtightness in the shaft hole 7 and the like. Yes.

  In addition, the outer cylinder 5 is made of stainless steel and has a cylindrical shape. The outer cylinder 5 holds an intermediate portion of the outer peripheral surface along the direction of the axis CL <b> 1 of the ceramic heater 4 on its inner periphery. And while the front-end | tip part of the ceramic heater 4 protrudes from the front-end | tip of the said outer cylinder 5, while the rear-end part of the ceramic heater 4 is inserted in the said shaft hole 7, it protrudes from the rear end of the outer cylinder 5. . Further, the outer cylinder 5 is subjected to laser welding along the contact surface between the front end surface of the housing 2 and the outer cylinder 5 in a state where the rear end portion of the outer cylinder 5 is press-fitted into the shaft hole 7. It is joined.

  In addition, the outer cylinder 5 has a relatively small diameter small diameter portion 5A located on the front end side in the axis CL1 direction, and is located on the rear end side in the axis CL1 direction relative to the small diameter portion 5A, and has an outer diameter larger than the outer diameter of the small diameter portion 5A. Is provided with a large diameter portion 5B. Further, between the small diameter portion 5A and the large diameter portion 5B, a tapered pressure contact portion 5C that is tapered toward the tip end side in the axis line CL1 direction is formed.

  As shown in FIG. 2, the ceramic heater 4 is made of an insulating ceramic (for example, silicon nitride as a main component), has a cylindrical base 21 extending in the direction of the axis CL1, and is embedded in the cylindrical base 21. And a long and thin U-shaped heating element 22 made of conductive ceramic. The base 21 is formed so as to have substantially the same outer diameter except for its tip. The heat generating element 22 includes a heat generating portion 23 and a pair of rod-shaped lead portions 24 and 25 joined to both ends of the heat generating portion 23. The heat generating part 23 is a part that functions as a so-called heat generating resistor, and has a substantially U-shaped cross section along the curved surface at the tip of the ceramic heater 4 formed in a curved surface. In this embodiment, the cross-sectional area of the heat generating part 23 is made smaller than the cross-sectional area of the lead parts 24 and 25, and the (electrical) resistivity of the conductive ceramic constituting the heat generating part 23 The resistivity is higher than that of the conductive ceramic. Accordingly, the heat generation part 23 positively generates heat during energization.

  Further, the lead portions 24 and 25 extend substantially parallel to each other toward the rear end side of the ceramic heater 4. In addition, on the rear end side of one lead portion 24, an electrode extraction portion 26 protrudes in the outer peripheral direction, and the electrode extraction portion 26 is exposed on the outer peripheral surface of the ceramic heater 4. Similarly, the other lead portion 25 is also provided with an electrode extraction portion 27 protruding in the outer peripheral direction, and the electrode extraction portion 27 is exposed on the outer peripheral surface of the ceramic heater 4. In addition, the electrode extraction part 26 of one lead part 24 is formed on the rear end side in the axis line CL1 direction with respect to the electrode extraction part 27 of the other lead part 25.

  In addition, the exposed portion of the electrode extraction portion 26 is in contact with the inner peripheral surface of the connection member 10, and as a result, the middle shaft 3 connected to the connection member 10 and the lead portion 24 are electrically connected. ing. Further, the exposed portion of the electrode extraction portion 27 is in contact with the inner peripheral surface of the outer cylinder 5, and electrical continuity is achieved between the housing 2 joined to the outer cylinder 5 and the lead portion 25. Yes. That is, in the present embodiment, the middle shaft 3 and the housing 2 function as an anode and a cathode for energizing the heat generating portion 26 of the ceramic heater 4.

  Further, as shown in FIG. 3, when the screw portion 8 is screwed into the mounting hole HO of the internal combustion engine EN, the pressure contact portion 5C is pressed against the taper sheet TS of the internal combustion engine EN. Further, at least a surface of the outer cylinder 5 that is located on the inner peripheral side of the pressure contact portion 5C is in close contact with the outer peripheral surface of the ceramic heater 4 (in this embodiment, excluding the edge of the inner hole of the outer cylinder 5). Since the entire inner peripheral surface is in close contact with the outer peripheral surface of the ceramic heater 4, the press contact portion 5C is configured to be hardly deformed radially inward when the press contact portion 5C is pressed against the taper sheet TS. Has been. Of the taper sheet TS of the internal combustion engine EN, at least a portion to which the outer cylinder 5 is pressed is formed of a metal (for example, cast iron) whose main component is iron (Fe).

  In addition, in this embodiment, as shown in FIG. 4, the press contact portion 5 </ b> C is provided with a plating 5 </ b> D as a frictional force reducing means on its surface (in FIG. 4, for convenience of illustration, it is more than actual. The plating 5D is shown as thick). The plating 5D is formed of a predetermined metal material (for example, Cu, Ag, Ni, Zn, Au, or an alloy having one of these as a main component), and the thickness T thereof is a predetermined value (for example, 10 μm) or more.

As described in detail above, in the present embodiment, at least the surface located on the inner peripheral side of the press contact portion 5C of the outer cylinder 5 is in close contact with the outer peripheral surface of the ceramic heater 4, and further, of the tapered sheet TS. A portion to be pressure-contacted of the pressure contact portion 5C is formed of a metal having Fe as a main component. Therefore, there is a greater concern about the deformation of the pressure contact portion 5C during assembly to the internal combustion engine EN. In this regard, according to the present embodiment, the outer cylinder 5 includes the plating 5D as the frictional force reducing means. Therefore, when the screw portion 8 is screwed into the mounting hole HO of the internal combustion engine EN, the frictional force generated between the press contact portion 5C and the taper sheet TS can be more reliably reduced. As a result, deformation of the pressure contact portion 5C can be effectively suppressed, and deterioration of the airtightness in the combustion chamber ER can be more reliably prevented.
[Second Embodiment]
Next, a second embodiment will be described with a focus on differences from the first embodiment with reference to the drawings. In the first embodiment, the plating 5D is provided as the frictional force reducing means. However, in the second embodiment, as shown in FIG. 5, the groove 5E is provided as the frictional force reducing means. . The groove portion 5E is formed on the outer periphery of the large diameter portion 5B, extends along the circumferential direction of the large diameter portion 5B, and has an annular shape centering on the axis CL1. Further, the groove 5E is formed in the vicinity of the rear end of the press contact portion 5C (for example, a position separated from the rear end of the press contact portion 5C by 0.5 mm to 3.0 mm along the axis CL1). Further, the groove portion 5E has a width W along the axis CL1 set to a predetermined value (for example, 0.5 mm) and a depth D set to a predetermined value (for example, 1.0 mm).

  In addition, as shown in FIG. 6, by adjusting the angle of the pressure contact portion 5C, when the screw portion 8 is screwed into the mounting hole HO of the internal combustion engine EN, at least the outer peripheral portion of the pressure contact portion 5C is the internal combustion engine. The taper sheet TS is pressed against the EN taper sheet TS. Specifically, in the pressure contact portion 5C, at least a portion corresponding to the groove 5E is in pressure contact with the taper sheet TS along the direction of the axis CL1. Further, the formation position, width W, and the like of the groove 5E are set as described above, so that when the screw portion 8 is screwed into the mounting hole HO of the internal combustion engine EN, FIGS. 7 (a) and 7 (b). As shown, the pressure contact portion 5C can be deformed toward the rear end side in the direction of the axis CL1.

  In the second embodiment, as in the first embodiment, the outer cylinder 5 is fixed to the distal end portion of the housing 2 with the rear end portion of the outer cylinder 5 being press-fitted into the shaft hole 7. . Therefore, it is preferable to form the groove 5E by cutting or the like after the outer cylinder 5 is fixed to the housing 2 in order to prevent the groove 5E from being crushed and deformed due to the press-fitting. In the case where the rear end portion of the outer cylinder 5 is not press-fitted into the shaft hole 7, the groove portion 5E may be formed before the outer cylinder 5 is fixed to the housing 2.

  As described above, according to the second embodiment, the same operational effects as those of the first embodiment are basically obtained. That is, due to the presence of the groove portion 5E, when the screw portion 8 is screwed into the mounting hole HO of the internal combustion engine EN, the press contact portion 5C can be deformed to the rear end side in the direction of the axis CL1, and the press contact portion from the taper sheet TS. The stress applied to 5C can be reduced. Thereby, the frictional force generated between the press contact part 5C and the taper sheet TS can be reduced, and the deformation of the press contact part 5C can be more reliably prevented. As a result, the airtightness in the combustion chamber ER can be more reliably ensured.

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

  (A) In the above embodiment, the frictional force reducing means is constituted by the plating 5D or the groove 5E. However, the frictional force reducing means may be constituted by both the plating 5D and the groove 5E. In this case, when the glow plug 1 is assembled to the internal combustion engine EN, the frictional force generated between the outer cylinder 5 and the taper sheet TS can be further reduced, and further deformation of the pressure contact portion 5C can be further reduced. It can be surely suppressed.

  (B) In the above embodiment, the frictional force reducing means is realized by plating or a groove, but the frictional force reducing means may be realized by other means. Therefore, for example, metal coating or butyrol coating (for example, aluminum powder coating butyroll or the like) provided in a portion of the outer cylinder 5 that is in pressure contact with the tapered sheet TS may be used as the frictional force reducing means. Further, the outer cylinder 5 may be provided with a frictional force reducing means by performing chemical conversion treatment (for example, a water-soluble non-reactive sealer containing a lubricant) on a portion of the outer cylinder 5 that is in pressure contact with the tapered sheet TS. In butyrol coating, for example, butyrol # 1000A silver (product name) can be used, and in the chemical conversion treatment, for example, sealer 300WL (product name) can be used.

  (C) The shape of the ceramic heater 4 is not particularly limited, and may be, for example, an elliptical cross section, an elliptical cross section, or a polygonal cross section. Further, it may be embodied as a so-called plate heater in which a plurality of insulating substrates are formed in a plate shape and a heating element is sandwiched therebetween.

  DESCRIPTION OF SYMBOLS 1 ... Glow plug (ceramic glow plug), 2 ... Housing, 4 ... Ceramic heater, 5 ... Outer cylinder, 5A ... Small diameter part, 5B ... Large diameter part, 5C ... Pressure-contact part, 5D ... Plating (friction force reduction means), 5E: Groove (frictional force reducing means) 7: Shaft hole, 8: Screw part, 21 ... Base, 22 ... Heating element, CL1 ... Axis, EN ... Internal combustion engine, HO ... Mounting hole, TS ... Tapered sheet.

Claims (6)

A cylindrical housing having an axial hole extending in the axial direction and having a threaded portion for screwing into an attachment hole of the internal combustion engine on the outer peripheral surface;
A substrate made of an insulating ceramic, and a ceramic heater having a heating element made of a conductive ceramic and embedded in the substrate;
A cylindrical outer cylinder fixed to the front end of the housing and holding the outer periphery of the ceramic heater on its inner periphery;
The outer cylinder is made of stainless steel,
A small-diameter portion located on the tip side in the axial direction;
A larger diameter portion located on the rear end side in the axial direction than the smaller diameter portion, and having a larger diameter than the smaller diameter portion,
A ceramic glow plug that is located between the small diameter portion and the large diameter portion and has a pressure contact portion that presses against a taper sheet of the internal combustion engine when the screw portion is screwed into a mounting hole of the internal combustion engine. Because
Of the outer cylinder, at least the surface located on the inner peripheral side of the pressure contact portion is in close contact with the outer peripheral surface of the ceramic heater,
The outer cylinder includes a friction force reducing means for reducing a friction force generated between the tapered sheet and the press contact portion when the screw portion is screwed into a mounting hole of the internal combustion engine. Ceramic glow plug.   2. The ceramic glow plug according to claim 1, wherein the frictional force reducing means is a plating provided on the surface of the pressure contact portion. 3.   The frictional force reducing means is formed on the outer periphery of the outer cylinder and extends along the circumferential direction of the outer cylinder, and when the threaded portion is screwed into the mounting hole of the internal combustion engine, the pressure contact portion is 2. The ceramic glow plug according to claim 1, wherein the ceramic glow plug is a groove that is deformable toward the rear end side in the axial direction. The frictional force reducing means is
The plating provided on the surface of the pressure contact portion;
It is formed on the outer periphery of the outer cylinder and extends along the circumferential direction of the outer cylinder, and when the threaded portion is screwed into the mounting hole of the internal combustion engine, the pressure contact portion is directed toward the rear end in the axial direction. The ceramic glow plug according to claim 1, wherein the ceramic glow plug is configured to be deformable. The ceramic glow plug according to claim 1, wherein the frictional force reducing means is a coating provided on a surface of the press contact portion. A ceramic glow plug assembly structure, wherein the ceramic glow plug according to any one of claims 1 to 5 is assembled to an internal combustion engine,
An assembly structure of a ceramic glow plug, wherein at least a portion of the tapered sheet of the internal combustion engine to which the pressure contact portion is pressed is formed of a metal having iron as a main component.

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