JP5335974B2 - Glow plug - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent generation of local excess stress on a heater element while ensuring sealability and heat conductivity, and to prevent fracture and breakage of a ceramic heater element even when the brittle ceramic heater element is used in the heater element, in the glow plug having a constitution in which the sealability in being mounted on an engine and efficient heat conductivity are ensured by pressing a tip-ward end face of an annular projection part disposed on a metallic cylindrical body against a seating surface of a mounting hole of the engine. <P>SOLUTION: A diameter-expanded part 29 having an inner diameter larger than that of a region holding an outer peripheral face of the heater element 11 in a tightening state, is disposed on a region corresponding to the annular projection part 22, of an inner peripheral face of the metallic cylindrical body 21, and a clearance gap K is formed between the inner peripheral face 29a of the diameter-expanded part 29 and the outer peripheral face of the heater element 11. The generation of excess stress is prevented as the heater element 11 is not tightened at a relatively-thick annular projection part 22. <P>COPYRIGHT: (C)2012,JPO&amp;INPIT

Description

  The present invention relates to a glow plug used for preheating or the like for promoting start-up of a diesel engine.

  As this type of glow plug, the one shown in FIG. 10 is known (Patent Document 1). The glow plug 201 generates heat by energizing the inside of a metal cylindrical body (also referred to as an outer cylinder) 21 having an annular convex portion 22 that protrudes outward on the outer peripheral surface and forms an annular shape in the circumferential direction. A rod-like or shaft-like heater element 11 having a resistance heating element within itself (in the tip) is fixed in an interference-fitted state by protruding the tip 10 of the heater element 11 from the tip of the metal cylindrical body 21. The metal cylindrical body 21 is fixed and assembled by welding in a state where the tip of the cylindrical metal shell 31 is in contact with the rear end of the annular protrusion 22. In such a glow plug 201, two electrode terminals (electrode extraction portions) 16, 17 connected to the resistance heating element 13 embedded in the heater element 11 are provided on the outer peripheral surface near the rear end of the heater element 11. It is formed to be exposed. For example, one electrode terminal 16 is coaxially arranged so as to hold insulation inside the metal shell 31 via a connecting metal ring (cylinder) 61 fitted on the rear end thereof. The metal shaft 51 (metal shaft) 51 is connected to a pin terminal 71 fixed to the rear end of the metal shaft 51. The other electrode terminal 17 is press-contacted to the inner surface of a metal cylindrical body 21 to which a heater element (hereinafter also referred to as a heater element or simply an element) 11 is fixed (press-fitted) by an interference fit, and serves as a ground electrode. It is configured to make. In this specification, with respect to the glow plug and its constituent members (parts) and their respective parts or portions, the “tip” refers to their lower ends in FIG. 10, and “rear end” refers to the opposite end. Say.

  Such a glow plug (hereinafter simply referred to as a plug) 201 is inserted into a plug mounting hole 103 in an engine cylinder head (engine head or simply engine) 101 and formed on the outer peripheral surface of the metal shell 31. It is attached by a screwing method via the male screw 37 formed. In the attachment, the end-facing end surface 23 of the annular protrusion 22 is strongly pressed against the annular seating surface 105 at the back of the plug attachment hole 103. Thereby, the plug 201 is positioned in the screwing direction. At the same time, a seal (airtight) between the combustion chamber and the outside in the mounting hole 103 is maintained, and the ground-side electrode terminal 17 of the element 11 is connected. And in such an attachment structure, it is comprised so that the heat of the metal cylindrical body 21 may be released to an engine so that it may mention below.

  In the assembly of the glow plug 201 having the above-described configuration, the heater element 11 is held in an interference-fitted state on the metal tubular body 21. Usually, the heater element 11 is relatively press-fitted into the metal tubular body 21. It is assembled by pushing (pushing it into an interference fit state). Here, the heater element 11 is held in an interference fit with the metal cylindrical body 21 because the airtightness (sealing) between the outer peripheral surface of the heater element 11 and the inner peripheral surface of the metal cylindrical body 21 is maintained. It is for holding. In addition to this, the heat of the heater element 11 and the metal cylindrical body 21 that are exposed to a high temperature by being disposed in the engine combustion chamber is efficiently transmitted to the engine and released. On the other hand, in the glow plug having the above-described configuration, the heat of the metal tubular body 21 is strongly pressed because the end-facing end surface 23 of the annular convex portion 22 is strongly pressed against the seating surface 105 of the plug mounting hole 103. Therefore, there is an advantage that the heat can be efficiently released to the engine (block).

JP 2004-205148 A

  However, in the glow plug 201 having the above-described configuration, the heater element 11 has a longitudinal direction (axis line) particularly when the base is made of a brittle ceramic (hereinafter also referred to as ceramic heater element, heater element, or simply element). (G direction), there was a risk of breakage or breakage at or near the portion H corresponding to the annular convex portion 22 of the metal tubular body 21 indicated by the dotted line in the left diagram of FIG. The inventors of the present application investigated the cause in detail and examined it, and found the following. In the glow plug having the above-described structure, the end-facing end surface 23 of the annular protrusion 22 in the metal cylindrical body 21 is pressed against the seating surface 105 of the mounting hole 103 of the engine, ensuring the seal and the metal cylindrical body 21. The heat is released to the engine via the end face 23 facing the front end. For this reason, the thickness (the radial thickness) of the portion H where the annular protrusion 22 is present in the metallic cylindrical body 21 is the other portion (the metallic cylindrical body of FIG. 10). Compared with the thickness of the lower thin-walled cylinder portion 21 in FIG. 21, the thickness is partially thicker by the protruding dimension in the radial direction of the end-facing end surface 23. Moreover, in order to ensure the sealing property of the glow plug 201 and to improve the thermal conductivity as described above, it is desirable to ensure that the radial dimension of the distal end surface 23 is as large as possible. There is a request. Therefore, the thickness of the annular convex portion 22 must be considerably thicker than the thickness of the other thin cylindrical portion, specifically, several times the thickness of the other thin cylindrical portion. It will be thick.

  On the other hand, the heater element 11 is usually a cylinder having substantially the same diameter except that the tip is formed in a hemispherical shape, and this is formed in the axial direction of the metal cylindrical body 21. Is usually press-fitted and assembled so that a constant interference fit is achieved. On the other hand, the metal cylindrical body 21 is a thin straight cylinder (cylindrical) having a substantially constant thickness except for the portion H of the annular convex portion 22 as described above. For this reason, among the heater elements 11 that are in an interference fit state with such a metal cylindrical body 21, of the region in the direction of the axis G of the inner peripheral surface of the metal cylindrical body 21, it corresponds to the annular convex portion 22. In the region where the inner peripheral surface of the portion (annular convex corresponding region region) H that holds the outer peripheral surface of the heater element 11 in an interference fit state, other portions, ie, the relative absence of the annular convex portion 22 exists. In comparison with a thin-walled region (hereinafter also referred to as a thin-walled cylinder portion), a large compressive stress is locally applied several times corresponding to the thickness difference of the metal-made cylinder. As described above, the annular convex portion 22 locally tightens the region portion H corresponding to the annular convex portion 22 in the element 11 with a large tightening force. If the tightening force is extremely large and excessive, the element 11 is locally subjected to an extremely large compressive stress in the region H corresponding to the annular convex portion. This is considered to be a factor causing breakage (breaking) or breakage in the portion H in the axial direction of the heater element 11 or in the vicinity thereof.

  Such a problem can be solved immediately if the metal cylindrical body 21 is not provided with the thick annular protrusion 22. However, with this configuration, it is not possible to ensure the sealing performance in the attachment to the engine, or the performance is deteriorated. Further, the heat of the heater element 11 and the metal cylindrical body 21 cannot be efficiently released to the engine head through a short route.

  The present invention has been made in view of such problems, and its purpose is to ensure sealing performance and efficient thermal conductivity in mounting to an engine, such as a glow plug having the above-described configuration, in a metal cylindrical shape. In the structure in which the end-facing end surface of the annular convex portion provided on the body is pressed against the seating surface of the mounting hole of the engine, the heater element while ensuring the sealing performance and thermal conductivity In this case, it is possible to suppress or prevent excessive stress from being generated locally, and even if a brittle ceramic heater element is used for the heater element, breakage or breakage may occur. It is to prevent.

Another reference invention different from the present invention is to energize the inner side of a metallic cylindrical body having an annular convex portion projecting outward on the outer circumferential surface of its own cylindrical portion and forming an annular shape in the circumferential direction. A rod-shaped or shaft-shaped heater element having a resistance heating element that generates heat is fixed as an interference fit,
A glow plug in which a cylindrical metal shell is assembled coaxially with the metal cylindrical body on the rear end side of the metal cylindrical body formed by fixing the heater element,
It is inserted into a glow plug mounting hole with a female screw in the engine head, and is configured to be mounted by a screw method using a male screw formed on the outer peripheral surface of the metal shell. In the mounting by the screwing, the tip of the annular convex portion In the glow plug configured such that the facing end surface is pressed against the annular seating surface behind the glow plug mounting hole,
Of the inner peripheral surface of the metallic cylindrical body, the inner diameter of the inner peripheral surface corresponding to the annular convex portion is larger than the inner diameter of the portion holding the outer peripheral surface of the heater element in an interference fit state. A large-diameter enlarged portion is provided, and a gap is formed between the inner peripheral surface of the enlarged-diameter portion and the outer peripheral surface of the heater element.

In the reference invention, the annular convex portion is formed so that an outer peripheral surface forms a cylindrical surface, and the end surface facing the tip forms a tapered surface at the tip of the cylindrical surface,
The distal end of the enlarged diameter portion may be present on the distal end side that exceeds a circumferential ridge line that forms a boundary between the cylindrical surface and the tapered tapered surface in the axial direction of the metal cylindrical body .

According to the first aspect of the present invention, current is supplied to the inner side of a metallic cylindrical body having an annular convex portion that protrudes outward and forms an annular shape in the circumferential direction on the outer peripheral surface of its cylindrical portion. A rod-shaped or shaft-shaped heater element having a resistance heating element that generates heat is fixed as an interference fit,
A glow plug in which a cylindrical metal shell is assembled coaxially with the metal cylindrical body on the rear end side of the metal cylindrical body formed by fixing the heater element,
It is configured to be inserted into a glow plug mounting hole with a female screw in the engine head and to be mounted by a screw method using a male screw formed on the outer peripheral surface of the metal shell. In the glow plug configured such that the facing end surface is pressed against the annular seating surface behind the glow plug mounting hole,
Of the inner peripheral surface of the metallic cylindrical body, the inner diameter of the inner peripheral surface corresponding to the annular convex portion is larger than the inner diameter of the portion holding the outer peripheral surface of the heater element in an interference fit state. A large-diameter enlarged portion is provided, and a gap is formed between the inner peripheral surface of the enlarged-diameter portion and the outer peripheral surface of the heater element.
It has a cylindrical shape, and the heater element is inserted, a part of its outer peripheral surface is on the inner peripheral surface of the enlarged-diameter portion, and a part of its inner peripheral surface is on the outer peripheral surface of the heater element. A heater element holding cylinder formed so as to hold the heater element by being pressed with its own spring property at a different position in the axial direction is arranged .

According to the second aspect of the present invention, current is supplied to the inner side of the metallic cylindrical body provided with an annular convex portion that protrudes outward and forms an annular shape in the circumferential direction on the outer peripheral surface of the cylindrical portion. A rod-shaped or shaft-shaped heater element having a resistance heating element that generates heat is fixed as an interference fit,
A glow plug in which a cylindrical metal shell is assembled coaxially with the metal cylindrical body on the rear end side of the metal cylindrical body formed by fixing the heater element,
It is inserted into a glow plug mounting hole with a female screw in the engine head, and is configured to be mounted by a screw method using a male screw formed on the outer peripheral surface of the metal shell. In the glow plug configured such that the facing end surface is pressed against the annular seating surface behind the glow plug mounting hole,
Of the inner peripheral surface of the metallic cylindrical body, the inner diameter of the inner peripheral surface corresponding to the annular convex portion is larger than the inner diameter of the portion holding the outer peripheral surface of the heater element in an interference fit state. A large-diameter enlarged portion is provided, and a gap is formed between the inner peripheral surface of the enlarged-diameter portion and the outer peripheral surface of the heater element.
While having a cylindrical shape, the heater element is inserted, and the outer peripheral surface of the rear end or the portion close to the rear end is pressed against the inner peripheral surface of the enlarged diameter portion by its own spring property. The inner peripheral surface closer to the tip than the portion pressed against the inner peripheral surface of the heater element by its own spring property is formed so as to hold the heater element by being pressed against the outer peripheral surface of the heater element by its own spring property. It is characterized in that the heater element holding cylinder is arranged .

According to a third aspect of the present invention, the heater element holding cylinder is made of metal, and an electrode terminal for energizing the resistance heating element is exposed on the outer peripheral surface of the heater element. Is fixed in the metal cylindrical body in an interference fit state, the electrode terminal is brought into pressure contact with the inner peripheral surface of the heater element holding cylinder, whereby the metal cylindrical body and the resistor are The glow plug according to claim 1, wherein the glow plug is electrically connected to the heating element.

In the invention described in claim 4 , the heater element holding cylinder is pressed against the inner peripheral surface of the enlarged diameter portion of the metal cylindrical body by its own spring property.
The glow plug according to any one of claims 1 to 3, wherein the glow plug is welded to an inner peripheral surface or a rear end of the enlarged diameter portion.

The invention according to claim 5, wherein, the heater element cylindrical retaining bodies, one of the claims 1 to 4, characterized in that than the metallic, cylindrical member is as high hardness metal A glow plug according to claim 1 . The invention described in claim 6, wherein the any of claims 1 to 5, the inner circumferential surface of the heater element cylindrical retaining body, characterized in that the ionization tendency is formed following the metal layer Ni A glow plug according to claim 1 . Further, in the invention described in claim 7, the annular convex portion is formed so that an outer peripheral surface forms a cylindrical surface, and the end surface facing the tip forms a tapered surface at the tip of the cylindrical surface,
The distal end of the diameter-expanded portion is present on the distal end side beyond a circumferential ridge line that forms a boundary between the cylindrical surface and the tapered tapered surface in the axial direction of the metal cylindrical body. It is a glow plug of any one of 1-6.

In the glow plug of the reference invention described above , due to the above configuration, the inner peripheral surface of the portion corresponding to the annular convex portion of the metal cylindrical body is provided with an enlarged portion having a larger inner diameter than the outer peripheral surface of the heater element. The gap is formed between the inner peripheral surface of the enlarged diameter portion and the outer peripheral surface of the heater element. That is, according to the present invention, the outer peripheral surface of the heater element is excessively tightened as in the related art even if there is an annular convex portion that is thicker than the other portions because of the provision of such an enlarged diameter portion. This can be reliably reduced or prevented. Therefore, since it is possible to suppress or prevent the generation of large stress on the element, even if a heater element made of a brittle material such as a ceramic heater is used, there is a risk of damage or breakage. Can be reduced.

In the glow plug of the present invention, the end surface facing the tip of the annular convex portion is pressed against the seating surface of the mounting hole, and in order to improve the seal and heat conduction, an increase in the joint area by the pressing is required. Therefore, it is preferable to form the taper so as to have a taper. The outer peripheral surface of the annular convex portion is preferably formed in a cylindrical surface from the viewpoint of manufacturing or its configuration. On the other hand, as in the prior art, when the enlarged diameter portion is not provided on the inner side of the annular convex portion of the metal cylindrical body, and the heater element is in an interference fit state, the stress received by the heater element is: As for the axial direction, it can be said that it becomes the maximum at the portion fastened by the cylindrical surface that is the thickest in the annular convex portion. If the circumferential ridge line that forms the boundary between the cylindrical surface and the tapered tapered surface is exceeded, the thickness in the radial direction is surely reduced, and the stress applied to the element is reduced toward the tip side. Therefore, by forming the annular convex portion as described in claim 7 and setting the position of the tip of the enlarged diameter portion as described in the claim, the heater element is damaged or broken. The prevention effect is enhanced.

If the heater element holding cylinder is provided as in the first or second aspect of the invention, the element is also held in the enlarged diameter portion inside the annular convex portion of the metal cylindrical body. The That is, when such a heater element holding cylinder is not provided, the heater element is not held in the enlarged diameter portion, so that the holding power or stability of the element is reduced accordingly. Such a problem can be solved by providing an element holding cylinder. When the heater element holding cylinder according to claim 2 is embodied by a cylinder having a certain thickness, the outer diameter of the rear end portion is different from that of the tip portion. The body is illustrated. In such a different-diameter cylindrical body, both the large-diameter portion and the small-diameter portion may be formed of a parallel cylinder (stepped diameter-different cylinder), and the large-diameter portion near the rear end is directed toward the rear end. It is good also as a taper cylinder and a trumpet cylinder which expands in diameter. Moreover, it is good also as a taper cylinder and a trumpet cylinder which diameter-expands over the whole toward a rear end. In the second aspect of the present invention, a groove is provided in the circumferential direction on the inner surface of the enlarged diameter portion, and the outer peripheral surface of the rear end or rear end portion of the heater element holding cylinder is formed in the groove. You may make it fit in.

In the case of the invention described in claim 1 or 2, the configuration described in claim 3 is preferable. According to such a configuration, even in a plug having a design structure in which the ground electrode terminal exposed on the outer peripheral surface of the element is pressed against the inner peripheral surface of the annular convex portion to maintain conduction, the electrode terminal This is because the electrical connection between the metal cylinder and the metal cylinder is held via the heater element holding cylinder. Moreover, in such a configuration, the spring property (elastic force) can be adjusted by changing the hardness, strength, rigidity, thickness, etc. of the heater element holding cylinder. Since an appropriate pressing force (pressing force) to the electrode terminal can be easily applied, the design can be facilitated.

  As a technique for fixing the element in an interference fit in the metal cylindrical body, it is common to press-fit the element from the tip end side toward the tip end side from the metal cylindrical rear end side. Therefore, the heater element holding cylinder is disposed in the gap between the inner peripheral surface of the enlarged diameter portion and the outer peripheral surface of the heater element in the metal cylindrical body before press-fitting the element. In this case, the element may be placed in the enlarged diameter portion by press-fitting, and the element may be press-fitted as described above under the state. In the case where such a heater element holding cylinder is not provided, in the plug configured to hold the conduction by pressing the electrode against the inner surface (inner peripheral surface) of the metal cylindrical body, the electrode terminal is What is necessary is just to design an element so that it may be pressed by the inner surface (inner peripheral surface) of a metal cylindrical body in the position which does not correspond to an enlarged diameter part in an axial direction, and will be in an interference fit state.

In the arrangement of the heater element holding cylinder , as described in claim 4, the heater element holding cylinder is springy on an inner peripheral surface of the diameter-expanded portion of the metal cylinder. Instead of being pressed, it may be welded to the inner peripheral surface of the enlarged diameter portion or the rear end of the enlarged diameter portion. If it does in this way, in the assembly | attachment by the press injection of an element, since the problem that the said heater element holding | maintenance cylinder moves does not exist, the assembly | attachment becomes easy. Further, as described in claim 5, when the heater element holding cylinder is made of a metal having a hardness higher than that of the metal cylinder, the thickness and the desired strength and spring property are reduced. Therefore, the arrangement is easy even in a narrow portion such as the gap inside the enlarged diameter portion. Furthermore, as described in claim 6, it is preferable to form a metal layer having an ionization tendency of Ni or less on the inner peripheral surface of the heater element holding cylinder, and further, ionization that does not react with high-temperature water vapor. It is desirable to use a metal whose tendency is H or less. This is because the corrosion resistance of the inner peripheral surface of the heater element holding cylinder is improved, and the reliability of electrical connection is increased.

The longitudinal cross-sectional view of the reference form of the glow plug different from this invention, and its principal part enlarged view. The figure explaining the first half of the assembly | attachment process of the glow plug of FIG. The figure explaining the second half of the assembly | attachment process of the glow plug of FIG. The longitudinal cross-sectional view of the structure which has arrange | positioned the heater element holding | maintenance cylinder in the diameter expansion part of the metal cylinder in the glow plug of FIG. 1, and its principal part enlarged view. The A section enlarged view of FIG. Sectional drawing for description which attaches the cylinder for heater element holding | maintenance to the enlarged diameter part of a metal cylinder. Sectional drawing which shows another example of the cylinder for heater element holding | maintenance. The principal part expanded sectional view of the glow plug assembled | attached with another example of the cylinder for heater element holding | maintenance. The principal part expanded sectional view explaining the assembly | attachment state formed by externally fitting the front-end | tip of a metal shell to the outer peripheral surface of the enlarged diameter part of a metal cylindrical body in the glow plug of FIGS. The longitudinal cross-sectional view explaining the conventional glow plug, and its principal part enlarged view.

Before explaining embodiments of the glow plug according to claims 1 and 2 of the present invention, embodiments of the glow plug according to another invention (hereinafter referred to as reference embodiment or reference embodiment) are described. ) Will be described in detail with reference to FIGS. The glow plug 1 of the present embodiment is made of a metal ceramic element 11 having a shaft-shaped ceramic heater element 11 and the heater element 11 fixed (fixed) in a tightly fitted state with a tip (lower end in the drawing) 10 protruding. A cylindrical body (outer cylinder) 21 and a cylindrical metal shell 31 welded coaxially to the rear end (the upper end in the figure) of the metal cylindrical body 21 are configured as follows. .

The heater element 11 is formed in a columnar shape or a round bar shape having the same diameter in the direction of the axis G, and is formed in a U-shape in the present embodiment in the inside of the distal end side in an insulating base (for example, silicon nitride ceramic). A resistance heating element 13 that generates heat when energized is embedded. Then, relay portions (lead portions) 14 and 15 are connected to both ends of the resistance heating element 13 in the insulating base, respectively, and both ends of the outer peripheral surface are located at positions deviated from each other in the vicinity of the rear end of the heater element 11. It is exposed to (side surface) and forms positive and negative electrode terminals (electrode extraction portions) 16 and 17. The tip 10 of the heater element 11 is processed into a curved surface.

On the other hand, a metal cylindrical body (outer cylinder) 21 that fixes the heater element 11 in an interference fit is made of stainless steel and formed as follows. That is, the metal cylindrical body 21 of the present reference embodiment has a cylindrical cylindrical portion 20 that is long in the axis G direction. However, an annular convex portion 22 as described below is provided on the outer peripheral surface near the rear end of the cylindrical portion 20. The cylindrical portion 20 is formed in a cylindrical shape having a thickness that has both an inner diameter and an outer diameter that are constant afterward, and that does not cause excessive tightening even in an interference fit by press-fitting the element 11. Further, the rear end of the cylindrical portion 20 is integrally provided with an annular convex portion 22 that protrudes outward in a radial shape and forms an annular shape in the circumferential direction, concentrically with the cylindrical portion 20 (coaxial line G). ing. The outer peripheral surface of the annular convex portion 22 forms a cylindrical surface 26 having the same diameter, and a tip end-facing end surface (downward end surface shown in the drawing) 23 having a tapered shape is formed at the tip of the cylindrical surface 26. . In addition, the rear end (also referred to as a rear-end-facing end surface) 25 of the annular convex portion 22 is perpendicular to the axis G (vertical plane) in this reference embodiment . That is, the front end-facing end surface 23 is tapered, the rear end facing end surface 25 is flat, and the cylindrical surface 26 has the same diameter.

As shown in the enlarged view in FIG. 1, such a metallic cylindrical body 21 forms a boundary between the tip 21 a and the cylindrical surface 26 of the annular convex portion 22 and the tip-facing end surface 23 having a tapered taper. A hole having a constant inner diameter (hereinafter also referred to as an interference fit hole), in which the region L1 from the circumferential ridge line 24 to a portion slightly closer to the tip can be fixed with the outer peripheral surface of the heater element 11 in an interference fit state. 27. In the present embodiment , the inner diameter of the region in the direction of the axis G extends from the rear end 25 of the annular convex portion 22 to the tip end side position slightly beyond the ridge line 24, and the inner diameter is an interference fit hole 27. Although it is concentric with the inner diameter, it is a diameter-enlarged portion 29 having a circular cross section that is larger than the inner diameter by a certain size. The inner diameter 29a of the enlarged diameter portion 29 is set so that the inner diameter 29a of the enlarged diameter portion 29 is fixed when the heater element 11 having a constant diameter (outer diameter) is fixed in an interference fit state by the interference fit hole 27. And the outer peripheral surface of the element 11 may be small enough to have a gap (annular gap) K, but in the present embodiment , the gap on one side ( The radial gap) K is expanded so as to be 1 mm.

  Further, the taper angle θ and the radial dimension of the end-facing end surface 23 of the annular convex portion 22 having such an enlarged diameter portion 29 are such that when the plug 1 is screwed into the plug attachment hole 103 of the engine and attached, The end-facing end surface 23 of the convex portion 22 is pressed against the seating surface 105 at the back of the mounting hole so as to hold the seal, and the heat of the heated metal cylindrical body 21 passes through the bonding surface by this pressing. It is set from the viewpoint of ensuring a bonding area capable of efficiently conducting heat to the engine head (indicated by a two-dot chain line in the figure) 101. Incidentally, the taper angle θ of the end-facing end surface 23 is basically set corresponding to the seating surface 105, but it can be said that it is preferably in the range of 60 to 150 degrees across the axis G. It may be a flat surface without a taper.

In this embodiment , the position of the ground electrode terminal 17 among the electrode terminals exposed on the outer peripheral surface of the element 11 is such that the element 11 is press-fitted into the cylindrical portion 20 of the metal cylindrical body 21. Is set so as to be positioned near the rear end portion of the tubular portion 20 when being positioned at a predetermined position and held (fixed) in an interference fit state. The electrode terminal 17 is pressed against the inner peripheral surface (an interference fitting hole) of the cylindrical portion 20 together with the outer peripheral surface of the heater element 11 at that position, and the plug 1 is attached to the engine head mounting hole. When set, it is set so as to be electrically connected to the engine head via the metallic cylindrical body 21. That is, in this reference embodiment , the element 11 is press-fitted for a predetermined stroke from the tip end 10 thereof to the inner end (hole) from the rear end 25 side of the metal tubular member 21, and is fitted into the metal tubular member 21. By maintaining the state, the ground electrode terminal 17 exposed on the outer peripheral surface (side surface) of the element 11 is electrically connected to the inner peripheral surface of the metal cylindrical body 21.

Then, as shown in FIG. 1, the metal shell 31 attaches the tip 33 to the rear end 25 of the annular projection 22 in the metal cylindrical body 21 to which the heater element 11 is fixed in this way. In the state of being brought into contact with each other in a coaxial shape (attached together), in the present embodiment , the airtight state is fixed by welding (laser welding in the circumferential direction). The metal shell 31 has an elongated cylindrical shape as a whole, and the inner peripheral surface thereof has substantially the same diameter except for a portion near the rear end. The outer peripheral surface has a straight pipe portion 35 having the same outer diameter as the outer diameter of the annular convex portion 22, and the rear side of the outer peripheral surface is inserted into a plug mounting hole 103 with a female screw in the engine head 101. A screw (male screw) 37 is formed so as to be inserted and attached by a screwing method, and a tool engaging portion (polygonal portion) for engaging a screwing tool is provided on the outer periphery of the rear end portion behind the screw 37. 39 is formed. A diameter-enlarged portion is coaxially provided at the rear end of the inner peripheral surface of the metal shell 31. A sealing O-ring 41 and an insulating member 43 are loaded in the portion, and the rear end of the element 11 A metal shaft 51 for connection to the other electrode terminal 16 is provided coaxially.

In the present embodiment , a cylindrical metal ring (ring member) 61 is fitted to the rear end of the element 11 with a part of the rear end thereof protruding, and is exposed to the side surface of the element 11. The terminal 16 is pressed and connected. An elongated metal shaft (middle shaft) 51 that forms a connecting wire for connection with the pin terminal 71 provided outside the metal shell 31 is provided on the inner side of the rear end of the cylindrical metal ring 61. Are press-fitted or connected by welding, and are provided coaxially in the metal shell 31. However, the metal shaft 51 is composed of a round bar having a different diameter with a middle portion 57 excluding the front end portion 53 and the rear end portion portion 55 being constricted. A part of the rear end portion 55 is protruded from the rear end of the metal shell 31, and an O-ring is formed on the enlarged diameter portion formed on the inner peripheral surface of the rear end of the metal shell 31 as described above. 41 and an annular insulating member 43 are loaded and interposed, and the seal and insulation therebetween are maintained. A pin terminal 71 is externally fitted to the rear end of the metal shaft 51, and is fixed by being crimped to a reduced diameter while being pressed to the front end side. The metal ring 61 that connects the rear end of the element 11 and the metal shaft 51 is made of stainless steel, and the surface is pre-plated with copper plating or gold plating.

The entire assembly procedure of the glow plug according to the present embodiment is as follows (see FIGS. 2 and 3). First, the rear end of the element 11 is press-fitted and fitted to the inner peripheral surface of the front end portion of the metal ring 61 so that the electrode terminal 16 is electrically connected (see the left diagram in FIG. 2). Next, in order to establish the electrical connection of the electrode terminal 17 for grounding, the metal cylindrical body 21 is press-fitted into the heater element 11 to a predetermined position and held in an interference fit state. Thus, the heater element 11, the metal cylindrical body 21, and the metal ring 61 are integrated (see the intermediate diagram in FIG. 2). Next, the front end portion 53 of the metal shaft 51 is press-fitted and positioned on the rear end side of the metal ring 61, and laser welding is performed (see the right figure in FIG. 2).

  And the rear end (illustrated upper end) of the metal shaft 51 integrated in this way is inserted from the front end side of the metal shell 31 to the inside thereof. Then, the rear end 25 of the annular convex portion 22 which is the rear end of the metallic cylindrical body 21 is brought into contact with the front end 33 of the metal shell 31 and joined by welding (see the left figure in FIG. 3). Thereafter, the O-ring 41 and the insulating member 43 are externally fitted to the rear end of the metal shaft 51, the pin terminal 71 is fitted to the rear end of the metal shaft 51, and the insulating member 43 is pressed to the front end side in the axis G direction. The glow plug 1 shown in FIG. 1 is obtained by caulking and fixing the outer peripheral surface of the portion closer to the tip of the terminal 71 into a reduced diameter.

  The glow plug 1 assembled in this manner is then inserted into the plug mounting hole 103 in the engine head 101 and mounted in a screwed manner via a male screw 37 formed on the outer peripheral surface of the metal shell 31. In the mounting, the end-facing end surface 23 of the annular convex portion 22 is pressed against the annular seating surface 105 in the back of the plug mounting hole 103 and is electrically connected to the electrode terminal 17 on the ground side of the element 11 together with the seal. Connection is secured.

The following points are important in the glow plug 1 of the present embodiment . That is, in such a glow plug 1, the protruding end surface 23 of the annular protrusion 22 has a sufficient amount of protrusion in the radial direction as in the conventional case, and the plug mounting hole 103 is secured at the leading end surface 23. Is pressed against the seating surface 105. Therefore, during the driving of the engine, the heat of the element 11 and the metal cylindrical body 21 can be efficiently released to the engine head through the joint surface by the pressing as in the conventional case. That is, in the glow plug 1 of the present embodiment , the heat transfer performance is not hindered.

  In addition, the element 11 is held in an interference-fitted state in the relatively thin-walled tubular portion 20 of the metal tubular body 21, and corresponds to the relatively thick-walled annular convex portion 22. In the region (L2), since the enlarged diameter portion 29 is provided on the inner peripheral surface thereof, the interference fit is not provided, and the outer peripheral surface of the element 11 has a gap K. For this reason, the element 11 does not receive excessive tightening locally in this region L2, that is, in a portion corresponding to the annular convex portion 22 that is relatively thick. Accordingly, since the stress generated in the element 11 is reduced accordingly, the element 11 can be prevented from being broken or broken. Thereby, even if the heater element 11 made of a brittle material such as a ceramic heater is used, there is a remarkable effect that the risk of causing breakage or breakage can be reduced.

Moreover, in this reference embodiment , the end-facing end surface 23 of the annular convex portion 22 is formed to be tapered and the outer peripheral surface thereof is formed to be the cylindrical surface 26. And the position of the front-end | tip of the enlarged diameter part 29 is made into the front end side beyond the ridgeline 24 from the rear end 25 of the cyclic | annular convex part 22 in the axis line G direction. That is, in this reference embodiment , the enlarged diameter portion 29 is provided on the inner peripheral surface of the annular convex portion 22, but the distal end of the enlarged diameter portion 29 is not within the range of the cylindrical surface 26, but the cylindrical surface. The heater element 11 is not tightened at a portion corresponding to the cylindrical surface 26 of the annular convex portion 22 that is the thickest because the heater element 11 is present at a position beyond the ridge line 24 at the tip of 26. Therefore, since the region where the excessive stress is generated in the element 11 can be made extremely small, there is a remarkable effect that the risk of the element being damaged or broken can be greatly reduced.

Next, an embodiment embodying the glow plug of the present invention according to claims 1 to 2 will be described with reference to FIGS. However, the glow plug of this embodiment is a gap (annular) between the enlarged diameter portion 29 of the metal tubular body 21 and the outer peripheral surface of the heater element 11 in the glow plug 1 of the reference embodiment (or the reference embodiment). The heater element holding cylinder 81 having a cylindrical shape is disposed in the gap K), and the grounding electrode terminal 17 is pressed against the inner peripheral surface of the heater element holding cylinder 81. The only difference is that electrical continuity is maintained. Therefore, the same parts as those of the glow plug 1 of the reference embodiment are denoted by the same reference numerals, and the difference will be mainly described. Hereinafter, the same applies to other examples.

  That is, in this embodiment, the heater element holding the cylindrical shape in the gap (annular gap) K between the inner peripheral surface 29a of the enlarged diameter portion 29 and the outer peripheral surface of the heater element 11 in the metal cylindrical body 21. A cylinder 81 is disposed. However, in this arrangement state, a part of the rear end portion of the outer peripheral surface of the heater element holding cylinder 81 forms the large diameter portion 83 and is pressed against the inner peripheral surface 29a of the enlarged diameter portion 29 by its own spring property. Is set to On the other hand, in the heater element holding cylinder 81, the inner peripheral surface 86 at the distal end portion is pressed against the inner peripheral surface 29a of the enlarged diameter portion 29 due to its own spring property. 11 is held in the heater element holding cylinder 81 so as to be pressed on its outer peripheral surface. Of the electrode terminals exposed on the outer peripheral surface of the element 11, the grounding electrode terminal 17 is in a state where the element 11 is press-fitted into the metal cylindrical body 21 and fixed in an interference fit state. It is pressed against the inner peripheral surface 86 of the heater element holding cylinder 81 disposed in the enlarged diameter portion 29. In this embodiment, the heater element holding cylinder 81 is made of stainless steel, and the ground electrode terminal 17 of the heater element 11 is electrically connected to the metal cylinder 21 via the heater element holding cylinder 81. It is connected to the. In this embodiment, the heater element holding cylinder 81 is made of stainless steel having a Vickers hardness (hardness) of Hv: 400, whereas the metal cylinder 21 is made of stainless steel having a Vickers hardness of Hv: 200. It is made up of.

  In the present embodiment, the heater element holding cylinder 81 arranged in the enlarged diameter portion 29 has a large diameter portion 83 that is enlarged toward the rear end 82 via a tapered portion 83a. A space is formed between the outer peripheral surface 85 of the portion (small diameter portion) 84 having a relatively small diameter except for the large diameter portion 83 and the inner peripheral surface 29a of the enlarged diameter portion 29. Has been. However, the cylindrical body 81 is press-fitted into the enlarged diameter portion 29 so that the rear end 82 of the larger diameter portion 83 is pressed against the inner peripheral surface 29a of the enlarged diameter portion 29. The fixing means or the joining means is not limited, for example, the rear end 82 may be fixed to the rear end of the enlarged diameter portion 29 by welding, or may be fixed by brazing.

  Note that such a heater element holding cylinder 81 is disposed or fixed in the enlarged diameter portion 29 in a state where the element 11 is held in an interference fit state in the metal cylinder 21. Just do it. However, such a heater element holding cylinder 81 is placed in the enlarged diameter portion 29 or fixed in the glow plug assembling step, as shown in FIG. It is preferable that the element 11 is press-fitted into the inner peripheral surface 86 and the ground electrode terminal 17 is pressed against the inner peripheral surface 86 to ensure the electrical connection. The outer diameter D1 of the large-diameter portion 83 of the heater element holding cylinder 81 is set to be larger than the inner diameter D0 of the inner peripheral surface 29a of the enlarged-diameter portion 29 in the free state and disposed in the enlarged-diameter portion 29. It is preferable to have an interference fit when it is done. Further, the inner diameter D <b> 2 of the small diameter portion 84 of the heater element holding cylinder 81 only needs to be large enough to allow the heater element 11 to be tightly fitted when placed in the enlarged diameter portion 29.

  In this embodiment, since the element 11 is press-fitted into the heater element holding cylinder 81, the outer peripheral surface 85 excluding the large diameter portion 83 of the rear end 82, the inner peripheral surface 29 a of the enlarged diameter portion 29, and A gap is set between the two. Thus, the element 11 is held in the heater element holding cylinder 81 with its own spring property (elastic deformation). In this holding state, the thickness of the holding cylinder 81 itself is the same as that in the case where the annular convex portion itself is directly tightened so that the force for tightening the outer peripheral surface of the element 11 does not become excessive tightening. It is smaller than the wall thickness, and the interference allowance is set smaller.

  In this embodiment, the heater element holding cylinder 81 has its tip 89 abutted against the annular shelf surface 30 located at the tip of the enlarged diameter portion 29 or slightly separated without being abutted. Yes. The rear end 82 is made to coincide with the rear end of the annular convex portion 22. In addition, in this embodiment, the heater element holding cylinder 81 is plated with copper, and further, a plated layer (for example, a gold plated layer) made of a noble metal is formed on the surface. Is prevented from oxidation.

Thus, in this embodiment, in the reference embodiment , before the heater element 11 is press-fitted into the metal tubular body 21 and held in an interference fit state, the inside of the enlarged diameter portion 29 of the metal tubular body 21 is increased. Then, the heater element holding cylinder 81 is press-fitted or fixed by welding as described above. The element 11 is held in an interference-fitted state by press-fitting a predetermined stroke from the heater element holding cylinder 81 side into the metal cylinder 21 toward the tip. By doing so, in this embodiment, the element 11 is held in an interference fit state in the metal cylindrical body 21, and at the same time, the grounding electrode terminal 17 and the outer peripheral surface (side surface) of the element 11 in the vicinity thereof are The electrode terminal 17 is electrically connected to the metal cylindrical body 21 by being pressed against the inner peripheral surface 86 of the heater element holding cylinder 81 disposed in the enlarged diameter portion 29.

  That is, in the present embodiment, the element 11 is also held by the heater element holding cylinder 81 disposed in the enlarged diameter portion 29 inside the annular convex portion 22 of the metal cylindrical body 21. 11 is stabilized. In addition, the ground electrode terminal 17 exposed and formed on the outer peripheral surface of the element 11 is electrically connected at a position corresponding to the inner peripheral surface of the annular protrusion 22 in the axis G direction. Therefore, since it is possible to secure the connection at the same position as the element that has conventionally held the electrical connection on the inner peripheral surface of the annular convex portion, the conventional element having such a configuration can be used as it is. .

  In addition, when it is set as the structure which hold | maintains the element 11 also by the heater element holding cylinder 81 arrange | positioned in the enlarged diameter part 29 like this form, the heater element holding cylinder 81 tightens the element 11 excessively. It is necessary not to become. For this, as described above, the interference allowance may be set so that the tightening can be performed only in consideration of securing the electrical connection with the electrode terminal 17. Such tightening can be easily obtained by changing the hardness (hardness), strength, etc. of the material because the thickness of the heater element holding cylinder 81 is thinner than the thickness of the annular protrusion 22. . In particular, in the present embodiment, since the heater element holding cylinder 81 is made of a material harder than the metal cylinder 21, it has a relatively thin wall thickness and has desired strength and springiness as described above. can get.

In the above, the electrode terminal 17 for grounding the element 11 is brought into pressure contact with the inner peripheral surface of the heater element holding cylinder 81 and electrically connected to the engine head via the metal cylinder 21. Although explained as a thing, the connection between the electrode terminal 17 for grounding of the element 11 and the metal cylindrical body 21 is a cylindrical part in which the element 11 is in an interference fit state as in the reference form of FIGS. In the case where the electrical connection is ensured by another path as in the case where the structure is secured by the inner peripheral surface 27 of 20, the element 11 is held in the heater element holding cylinder 81. Therefore, in this case, it is not necessary to consider the electrical connection via the heater element holding cylinder 81. However, when the electrical connection with the electrode terminal 17 is ensured by the heater element holding cylinder 81 as in this embodiment, the electrode terminal 17 is naturally provided on the inner peripheral surface of the heater element holding cylinder 81. And the insulating substrate forming the element 11 are in contact with each other (pressure contact). Since the interface between the electrode terminal 17 and the insulating base is a joint surface made of different materials, the strength is lower than that of other parts of the element 11. In order to make electrical connection, the inner peripheral surface of the heater element holding cylinder 81 is also pressed against this interface, but if this force is excessive, the heater element 11 may be damaged. . On the other hand, in the heater element holding cylinder 81 according to the present embodiment, the pressure contact force can be moderated moderately, so that the element 11 starting from this interface can be prevented from being broken.

  In other words, since the electrode terminal 17 and the insulating base constituting the element 11 are made of different materials (raw materials), if a force is applied, there is a possibility that cracking or the like will occur starting from the interface between the two. In the heater element holding cylinder 81, the force (holding force of the element) can be relaxed, which is particularly effective when the element 11 is likely to be cracked. The heater element holding cylinder 81 has a large-diameter portion 83 whose diameter is enlarged toward the rear end 82 via a tapered portion 83a. However, as shown in FIG. The entire large part 83 may be formed in a tapered shape or a trumpet shape.

  In the above embodiment, the heater element holding cylinder 81 has been described as having the large-diameter portion 83 on the rear end 82 side. However, from the viewpoint of holding the element 11 by the cylindrical body 81, it is not limited to this. A cylindrical shape is formed in the gap between the inner peripheral surface 29 a of the enlarged diameter portion 29 and the outer peripheral surface of the heater element 11, and the element 11 is inserted. At the same time, at least a part of its own outer peripheral surface is on the inner peripheral surface 29a of the enlarged diameter portion 29, and at least a part of its own inner peripheral surface 29a is on the outer peripheral surface of the element 11, at different positions in the axis G direction. It is sufficient if it is formed so as to hold the element 11 by being pressed with its own spring property. Therefore, as shown in FIG. 8, instead of the heater element holding cylinder 81 used in the glow plug shown in FIGS. ′, And the outer peripheral surfaces of both large diameter portions 83 and 83 ′ are pressed against the inner peripheral surface 29 a of the enlarged diameter portion 29. The element 11 may be held by pressing the inner peripheral surface 86 of the small diameter portion against the outer peripheral surface of the element 11 with its own spring property.

When the electrode terminal 17 for grounding the element 11 is pressed against the inner peripheral surface of the heater element holding cylinder 81 and is electrically connected to the engine head via the metal cylinder 21. In order to secure such a pressure contact, the heater element holding cylinder 81 may be formed.

  The present invention is not limited to the above-described embodiment, and can be embodied with appropriate design changes. In the above embodiment, the metal cylindrical body 21 and the metallic shell 31 are fixed and assembled by welding so that the rear end 25 of the metallic cylindrical body 21 is abutted against the tip 33 of the metallic shell 31. However, the present invention is not limited to such an assembly structure. As shown in FIG. 9, the cylindrical metal shell is formed on the cylindrical surface 26 that is the outer peripheral surface of the annular convex portion 22 at the rear end 25 of the metal cylindrical body 21 to which the heater element 11 is fixed. It can also be embodied as a structure in which a portion close to the tip 33 of 31 is externally fitted and fixed and assembled by welding or the like in that state.

DESCRIPTION OF SYMBOLS 1 Glow plug 11 Heater element 17 Electrode terminal 20 of the heater element on the ground side 20 Cylindrical portion 21 of the metal cylindrical body 22 Metal cylindrical body 22 Annular convex portion 23 of the metallic cylindrical body Ridge line 25 in the circumferential direction Rear end 26 of the cylindrical body made of metal Cylindrical surface 29 on the outer peripheral surface of the annular convex portion 29 Expanded portion 29a Inner peripheral surface of the expanded portion
31 Metal shell 33 Tip 37 of metal shell Male screw 81 formed on the outer peripheral surface of the metal shell Heater element holding cylinder 85 Heater element holding cylinder outer peripheral surface 86 Heater element holding cylinder inner peripheral surface 101 Engine head 103 Glow plug mounting hole 105 Seating surface K that forms a ring at the back of the glow plug mounting hole G Gap Axis of metal cylindrical body

Claims (7)

On the outer peripheral surface of its own cylindrical portion, a rod-like shape having a resistance heating element that generates heat when energized with respect to the inside of a metallic cylindrical body provided with an annular convex portion projecting outward and annular in the circumferential direction, or Fix the axial heater element as an interference fit,
A glow plug in which a cylindrical metal shell is assembled coaxially with the metal cylindrical body on the rear end side of the metal cylindrical body formed by fixing the heater element,
It is inserted into a glow plug mounting hole with a female screw in the engine head, and is configured to be mounted by a screw method using a male screw formed on the outer peripheral surface of the metal shell. In the mounting by the screwing, the tip of the annular convex portion In the glow plug configured such that the facing end surface is pressed against the annular seating surface behind the glow plug mounting hole,
Of the inner peripheral surface of the metallic cylindrical body, the inner diameter of the inner peripheral surface corresponding to the annular convex portion is larger than the inner diameter of the portion holding the outer peripheral surface of the heater element in an interference fit state. A large-diameter enlarged portion is provided, and a gap is formed between the inner peripheral surface of the enlarged-diameter portion and the outer peripheral surface of the heater element .
It has a cylindrical shape, and the heater element is inserted, a part of its outer peripheral surface is on the inner peripheral surface of the enlarged-diameter portion, and a part of its inner peripheral surface is on the outer peripheral surface of the heater element. A glow plug comprising: a heater element holding cylinder formed to hold the heater element by being pressed by its own spring property at a different position in the axial direction . On the outer peripheral surface of its own cylindrical portion, a rod-like shape having a resistance heating element that generates heat when energized with respect to the inside of a metallic cylindrical body provided with an annular convex portion projecting outward and annular in the circumferential direction, or Fix the axial heater element as an interference fit,
A glow plug in which a cylindrical metal shell is assembled coaxially with the metal cylindrical body on the rear end side of the metal cylindrical body formed by fixing the heater element,
It is inserted into a glow plug mounting hole with a female screw in the engine head, and is configured to be mounted by a screw method using a male screw formed on the outer peripheral surface of the metal shell. In the mounting by the screwing, the tip of the annular convex portion In the glow plug configured such that the facing end surface is pressed against the annular seating surface behind the glow plug mounting hole,
Of the inner peripheral surface of the metallic cylindrical body, the inner diameter of the inner peripheral surface corresponding to the annular convex portion is larger than the inner diameter of the portion holding the outer peripheral surface of the heater element in an interference fit state. A large-diameter enlarged portion is provided, and a gap is formed between the inner peripheral surface of the enlarged-diameter portion and the outer peripheral surface of the heater element.
While having a cylindrical shape, the heater element is inserted, and the outer peripheral surface of the rear end or the portion close to the rear end is pressed against the inner peripheral surface of the enlarged diameter portion by its own spring property. The inner peripheral surface closer to the tip than the portion pressed against the inner peripheral surface of the heater element by its own spring property is formed so as to hold the heater element by being pressed against the outer peripheral surface of the heater element by its own spring property. A glow plug comprising a heater element holding cylinder that is arranged . The heater element holding cylinder is made of metal, and an electrode terminal for energizing the resistance heating element is exposed on the outer peripheral surface of the heater element, and the heater element is tightly fitted in the metal cylinder. In the fixed state, the metal cylindrical body and the resistance heating element are electrically connected by the electrode terminal being pressed against the inner peripheral surface of the heater element holding cylinder. The glow plug according to claim 1, wherein the glow plug is provided. Instead of the heater element holding cylinder being pressed by its own spring property to the inner peripheral surface of the enlarged diameter portion in the metal cylindrical body,
The glow plug according to any one of claims 1 to 3, wherein the glow plug is welded to an inner peripheral surface or a rear end of the enlarged diameter portion. The glow plug according to any one of claims 1 to 4, wherein the heater element holding cylinder is made of a metal having a hardness higher than that of the metal cylinder. The glow plug according to claim 1, wherein a metal layer having an ionization tendency of Ni or less is formed on an inner peripheral surface of the heater element holding cylinder. The annular convex portion is formed so that an outer peripheral surface forms a cylindrical surface, and the end-facing end surface forms a tapered surface at the tip of the cylindrical surface,
The distal end of the diameter-expanded portion is present on the distal end side beyond a circumferential ridge line that forms a boundary between the cylindrical surface and the tapered tapered surface in the axial direction of the metal cylindrical body. The glow plug according to any one of 1 to 6 .

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