JP2011075148A - Method of manufacturing glow plug - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent deformation such as crashing of a tip of a tube without complicating a pressure fitting device and a pressure fitting process, when a sheath tube configuring a sheath heater is pressure-fitted into a metal body in assembling and manufacturing a glow plug. <P>SOLUTION: The tip 22 of the sheath tube 21 configuring a sheath heater assembly 20 is relatively fitted into the metal body 11 from an opening of its rear end 15. A rear end face at a rear end 45 or a region near the rear end, of a shaft 41 for a terminal configuring the sheath heater assembly 20 is supported by a shaft-side supporting means 81, and under this state, the shaft-side supporting means 81 is relatively moved to be pressed forward with respect to the metal body 11, thus the sheath tube 21 is pressure-fitted into the body 11. As the tip 22 of the sheath tube 21 is not compressed, the deformation such as crashing does not occur. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a glow plug used for promoting start-up (preheating) of a diesel engine.

  Various types of such glow plugs are conventionally known (Patent Documents 1 and 2). FIG. 8 shows an example. The glow plug 201 includes a cylindrical metal fitting body (hereinafter, also simply referred to as a main body) 11 provided with a screw 18 on the outer peripheral surface near the rear end so as to be fixed to the plug hole of the engine head by a screwing method. The sheath tube 21 and the like fixed inside by a press-fitting method are mainly configured. Such a sheath tube (hereinafter also simply referred to as a tube) 21 has a structure in which a distal end (lower end in the drawing) 22 projects from the distal end 12 of the main body 11. The sheath tube 21 has a cylindrical shape with a closed end 22, and a coil-shaped resistance heating element (or a heating element and a control coil; hereinafter simply referred to as a coil) 30 generates heat when energized. The tip of the heating element is fixed to the tip 22 of the tube 21 by welding. Further, the rear end (or the rear end of the control coil) is electrically connected to the front end of the terminal shaft 41 inserted and fixed from the opening of the rear end 24 of the sheath tube 21 by welding or the like. . Such a sheath tube 21 constitutes a sheath heater assembly together with the heat generating coil and the terminal shaft 41 therein. Conventionally, in this assembly, the large-diameter portion 26 having a larger diameter than the others at the portion near the rear end of the sheath tube 21 is press-fitted into the small-diameter portion 13 having a smaller diameter than the other portions near the tip 12 of the metal fitting body 11. And the assembly was done. The press-fitting procedure will be described later. In addition, in this application document, regarding the glow plug 201 and the metal fitting body 11 and the sheath tube 21 and other components constituting the glow plug 201, the front end refers to the lower end in FIG. 8 and the reverse of the rear end. Say the upper edge.

  The sheath tube 21 configured as described above is filled with insulating powder (not shown) made of magnesia powder or the like, and is disposed on the inner peripheral surface of the rear end portion of the tube 21 and the outer peripheral surface of the terminal shaft 41. The inner insulating powder is sealed by crimping the rear end portion to a reduced diameter through a sealing material (for example, a rubber cylinder) 35 made of an insulating material, and the tube 21 is used for a terminal. The shaft 41 is fixed. Such a terminal shaft 41 is disposed in the metal fitting body 11 so as to be concentric and insulated (space), and its rear end protrudes from the rear end 15 of the main body 11 and protrudes therefrom. For example, a rubber seal ring packing 60 such as an O-ring packing and an insulating ring 65 are externally fitted to the rear end portion, and a lead wire connection for energization (voltage application) is connected to the rear end. A terminal 51 is fixed to constitute a glow plug 201. A screw-in polygon part 16 is formed on the outer periphery of the rear end 15 part of the main body 11 so as to have a larger diameter than that of the cylindrical part, and the ring packing 60 and the like are enlarged in diameter inside the polygon part. It is arrange | positioned at the formed arrangement | positioning part. Further, in the glow plug 201 shown in the figure, the external terminal 51 has a cap-shaped cylindrical portion 52 fitted on the rear end 45 of the shaft 41 and is insulated by a flange-shaped large-diameter portion 53 on the front end side. The ring packing 60 is compressed forward through the ring 65, and is crimped to a reduced diameter in this state, and is fixed to the shaft 41, and at the same time, the insulation between the rear end 15 of the main body 11 and the shaft 41 is maintained and sealed. is doing.

  In the manufacture of the glow plug 201 having the above configuration, conventionally, the sheath tube 21 constituting the sheath heater assembly with the terminal shaft 41 is press-fitted into the cylindrical metal fitting body 11 as follows. That is, as shown in FIG. 9, a sheath heater assembly (hereinafter also referred to as a sheath heater assembly or simply an assembly) 20 with a terminal shaft 41 is placed at a distal end 22 (lower end in the figure) of a sheath tube 21 constituting the sheath heater assembly. Standing in a supported state, a cylindrical metal fitting body 11 is externally fitted from the front end 12 side to the rear end (upper end in the figure) 45 side of the terminal shaft 41 located behind (upward in the figure). The rear end 45 of the terminal shaft 41 is inserted into the main body 11 (see FIGS. 9A and 9B). At this time, the distal end of the large-diameter portion (press-fit large-diameter portion 26) 26 of the sheath tube 21 and the tip of the small-diameter portion (press-fit small-diameter portion 13) 13 on the inner peripheral surface of the main body 11 are present in the press-fitting allowance. Based on the locked state. Therefore, from this state, the metal fitting body 11 is held coaxially with the sheath tube 21, the support 71 in the press-fitting device (press device) is applied to the distal end 22 of the sheath tube 21, and a predetermined force F is applied downward to the body 11. In addition to the above, a predetermined stroke is pushed in the axial direction.

  By doing so, the large-diameter portion 26 near the rear end of the sheath tube 21 is press-fitted into the small-diameter portion 13 near the tip 12 of the main body 11 (FIG. 9-C). After the press-fitting, as described above, the ring packing 60 and the insulating ring 65 are externally fitted to the portion near the rear end of the terminal shaft 41 protruding from the rear end 15 of the main body 11, and then the ring packing 60 is attached. While compressing, the external terminal 51 is fixed by caulking or the like to form a glow plug 201. 8 and 9 are simplified and exaggerated in thickness and the like. Conventionally, the reason for press-fitting into the metal fitting body 11 from the rear end side of the sheath tube 21 as described above is that the stroke during press-fitting can be reduced.

  Further, when the sheath tube 21 is press-fitted into the metal fitting body 11, the distal end 22 of the sheath tube 21 is exposed to the distal end side of the glow plug 201 instead of pushing the distal end 22 of the sheath tube 21 in this way. There is also known a manufacturing method in which the outer peripheral surface of a part or an intermediate part is chucked (held), and the sheath tube 21 is moved relatively rearward together with the chuck and is press-fitted inside the metal fitting body 11 (Patent Document 3). .

JP 2004-263918 A JP 2008-69986 A JP 2006-153363 A

  However, in the above-described conventional manufacturing method, in the glow plug 201 manufactured by a manufacturing method in which the distal end 22 of the sheath tube 21 forming the sheath heater assembly 20 is pressed into the main body 11, the distal end 22 of the sheath tube 21 is crushed. May occur. The cause is that when the sheath tube 21 is press-fitted into the main body 11, a large load is locally applied to the tip 22 of the tube 21, particularly when the tip 21 has a spherical shape with a convex tip. Because. Such a deformed product is basically handled as a defective appearance, but it also includes problems such as a possibility of reducing the interval between the windings at the tip of the coil in the sheath tube 21 or causing a short circuit. is doing.

  Further, when the manufacturing method of press-fitting the distal end 22 of the sheath tube 21 into the main body 11 is used, a portion of the sheath tube 21 that protrudes from the distal end 12 of the main body 11 in the press-fitting process is very small. However, there is a problem that the axis thereof is inclined with respect to the axis G of the main body 11 or a curve is generated (see the two-dot chain line in FIG. 9C). The cause of such a problem is considered as follows. The sheath tube 21 forming the glow plug 201 is assembled so that the rear end portion or about half of the rear end side is inserted into the main body 11 and the remaining front end 22 side protrudes from the front end 12 of the main body 11. On the other hand, in the conventional press-fitting method, when the sheath tube 21 is pressed into the sheath tube 21 to see how the force is applied when the distal end 22 of the sheath tube 21 is pushed and the rear end 24 side is inserted through the opening of the distal end 12 of the main body 11, At the start, a compressive force corresponding to the press-fitting resistance is applied in the axial direction between the distal end 22 of the tube 21 and the press-fitting large-diameter portion 26 to be press-fitted on the rear end 24 side. On the other hand, the sheath tube 21 is made of a Ni-based heat-resistant alloy or stainless steel, but the length from the front end 22 to the large-diameter portion 26 for press-fitting on the rear end side is considerably long (16 to 60 mm), and a thin thin pipe (outer diameter) 3.5-5.5 mm, thickness 0.5-1.0 mm).

  The portion of the sheath tube 21 that protrudes from the distal end 12 of the main body 11 is inclined or bent with respect to the axis. This is the condition and the slight inclination of the sheath tube 21 at the start of press-fitting, This is considered to be due to the inevitable non-uniformity of strength existing in the tube 21. The inclination and bending of the protruding portion of the sheath tube 21 are caused by external force such as vibration of the glow plug 201 attached to the engine head or vibration after the attachment, and the portion near the tip of the plug tube is attached to the plug hole. This can cause a serious problem of contact with the inner surface, and is positioned as a major drawback.

  In order to press-fit the sheath tube 21 into the main body 11, a portion near the distal end 22 (outer peripheral surface) of the sheath tube 21 exposed on the distal end side of the glow plug 201 is chucked and held, and this is held on the rear end side. Therefore, in the manufacturing method described in Patent Document 3 in which the body 11 is relatively press-fitted into the main body 11 from the distal end side, the occurrence of the inclination and bending of the sheath tube 21 as described above can be reduced. However, in the case of such a technique, a holding means (mechanism) for the sheath tube 21 including a chuck cylinder or the like is required, and there is a problem that the press-fitting device and the press-fitting process are complicated accordingly.

  The present invention has been made in view of the above problems in the assembly and manufacture of glow plugs, and a first object thereof is to provide a sheath tube that forms a sheath heater in a metal fitting body in the assembly and manufacture of glow plugs. When press-fitting, there is no complication of the press-fitting device and the press-fitting process, and there is no occurrence of deformation of the crushing party at the tip of the tube. And the 2nd objective is to prevent generation | occurrence | production of the inclination of the front end side of a sheath tube with respect to the axis line of a metal fitting main body, or bending. A third object is to press-fit a sheath tube that constitutes a sheath heater into the metal fitting body, and then externally fit a ring packing and an insulating ring to a portion near the rear end of the terminal shaft protruding from the rear end of the main body. It is intended to simplify the glow plug manufacturing process by simplifying another process of fixing the external terminal while compressing the ring packing.

In the invention according to claim 1 for solving the above-described problem, a resistance heating element that generates heat when energized is provided in a sheath tube whose tip is closed, and is fixed to the sheath tube and thereafter The sheath tube constituting the sheath heater assembly with the terminal shaft comprising a terminal shaft extending in the direction,
Relatively, the distal end of the sheath tube is press-fitted and fixed in a cylindrical metal fitting body with a predetermined amount protruding from the tip of the metal fitting body, and after the terminal shaft after the fitting. In a method of manufacturing a glow plug having a configuration in which an end protrudes a predetermined amount from the rear end of the metal fitting body,
The distal end of the sheath tube constituting the sheath heater assembly with the terminal shaft is relatively inserted into the metal fitting body from the opening at the rear end thereof,
The rear end facing surface at the rear end or the rear end portion of the terminal shaft constituting the sheath heater assembly with the terminal shaft is supported by the shaft side support means, and under this state, the metal body is attached to the metal fitting body. The shaft-side support means includes a press-fitting step of press-fitting the sheath tube into the metal fitting body by performing a relative movement in which the shaft-side support means is moved forward.

In the invention according to claim 2, in the state where the sheath tube is fixed to the metal fitting main body as a glow plug, at least a part of the longitudinal direction portion in the portion that is located inside the metal fitting main body, While the outer diameter has a large-diameter portion for press-fitting that is relatively larger than the other of the sheath tube itself,
The metal fitting body has a small diameter portion for press-fitting whose inner diameter is relatively smaller than that of the metal fitting itself so that the sheath tube can be press-fitted in the large-diameter portion for press fitting. Item 8. A method for manufacturing a glow plug according to Item 1.

  According to a third aspect of the present invention, in the press-fitting step, the sheath heater assembly has a distal end-facing surface at a rear end or a portion near the rear end of the terminal shaft with the distal end of the sheath tube up or down. The method of manufacturing a glow plug according to claim 1, wherein the glow plug is supported. According to a fourth aspect of the present invention, the shaft-side support means has a support hole for fitting a rear end or a rear end portion of the terminal shaft in a gap-fitted state, and the rear of the terminal shaft. The method for manufacturing a glow plug according to any one of claims 1 to 3, wherein the terminal shaft is supported by fitting an end or a portion near the rear end into the support hole.

  The invention according to claim 5 is characterized in that, in the press-fitting step, the metal fitting body is supported by a body-side support means that supports a tip-facing surface at the tip of the metal fitting body. It is a manufacturing method of the glow plug of description. According to a sixth aspect of the present invention, the metal fitting body has a screw-in polygonal portion having a relatively large diameter on the outer peripheral surface at a rear end or a portion near the rear end, and in the press-fitting step, The glow plug manufacturing method according to any one of claims 1 to 5, wherein the metal fitting body supports a tip-facing surface of the screw-in polygon portion.

In the invention according to claim 7, the terminal shaft constituting the sheath heater assembly is provided before the press-fitting step.
In the terminal shaft, a ring packing is placed on the front end side through an insulating ring in order to seal the rear end of the metal fitting body at the rear end portion that protrudes backward from the rear edge of the metal fitting body. A compression large-diameter portion to be compressed is integrally provided, and an external terminal for connecting a lead wire is provided behind the compression large-diameter portion, and further, from the compression large-diameter portion On the front end side, from the front end side toward the rear end side, a ring packing and an insulating ring are attached in an outer fitting shape,
In the press-fitting step,
The glow plug manufacturing method according to any one of claims 1 to 6, wherein the compression large-diameter portion compresses the ring packing through the insulating ring.

  In the present invention, when the sheath tube is press-fitted into the main body, since the distal end of the sheath tube is not supported, the distal end can be reliably prevented from being crushed (deformed). That is, in the present invention, the distal end of the sheath tube is relatively inserted into the main body from the opening at the rear end of the main body, and from this state, the rear end of the terminal shaft is moved forward, Since the relative movement of press-fitting the sheath tube on the side into the main body is performed, it is possible to reliably prevent the tip from being crushed (deformed).

  Further, as described in claim 2, by forming the sheath tube and the metal fitting body in advance, when the sheath tube is inserted into the metal fitting body from the opening at the rear end thereof relative to the tip, The distal end of the sheath tube can easily pass through the press-fitting small diameter portion of the metal fitting body without being press-fitted. Thereby, in the press-fitting process of the sheath tube, it is possible to prevent an excessive compressive force in the axial direction from being applied between the tip of the sheath tube and the front and rear of the large-diameter portion for press-fitting of the tube located behind the sheath tube. For this reason, it is possible to effectively prevent the inclination or bending from occurring on the distal end side of the sheath tube. Further, since it is not necessary to hold the outer peripheral surface of the sheath tube with a chuck, the press-fitting device and the press-fitting process are not complicated.

  In the present invention, the portion supported by the shaft side support means is the rear end facing surface at the rear end or the rear end portion of the terminal shaft for the following reason. Depending on the terminal shaft, in addition to the rear end (rear end surface), if there is a large-diameter portion, such as a large-diameter portion for compression, in the portion closer to the rear end, for example, the large-diameter portion for compression, The rearward facing surface can be supported. That is, the terminal shaft has a rear end or a portion near the rear end serving as an external terminal for connecting a lead wire. As the external terminal, a screw having a screw formed behind a large diameter portion for compression such as a flange for pressing the ring packing for sealing the opening at the rear end of the main body through the insulating ring. There is a terminal structure. Also, the large-diameter portion for engagement that forms an attachment means for engaging with the socket-shaped terminal of the other party (lead wire end portion) between the pin terminal behind the large-diameter portion for compression for pressing such an insulating ring. There are pin terminal structures having In this structure, not only the rear end (rear end surface) of the terminal shaft but also the rear end facing surface of the large diameter portion for compression and the rear end facing surface of the large diameter portion for engagement in the press-fitting process. Support can be provided. This is the reason for the rear end facing surface at the rear end or near the rear end.

  The main body support means for supporting the metal fitting body may be any means that supports the metal fitting body in the axial direction so that press fitting by relative movement as described above is possible. That is, in the present invention, when the sheath tube is press-fitted into the main body, the distal end of the sheath tube is inserted into the main body from the opening at the rear end of the main body, and is relatively positioned at the rear end or rear end portion of the terminal shaft. In this case, the terminal shaft is pushed forward, and the distal end side sheath tube is press-fitted into the main body so as to make a relative motion. Therefore, if the body support means is attached to the fixed plate (for example, bed) side of the press-fitting press device, the shaft-side support means is attached to the movable plate side of the device. However, the movement is not limited to such a movement. In addition, since the tip of the sheath tube is assembled so as to protrude from the tip of the main body by a predetermined amount, the main body support means for supporting the metal fitting main body may be configured not to prevent the protrusion.

  In the present invention, as described in claim 3, the sheath heater assembly preferably has the distal end of the sheath tube up or down and the terminal shaft supports the rear end thereof. The posture is not limited to this. However, as described in claim 4, the shaft-side support means has a support hole for fitting the rear end of the terminal shaft or a portion near the rear end in a gap-fitted state, and the rear end of the terminal shaft. Alternatively, it is preferable to fit the portion closer to the rear end into the support hole to support the terminal shaft because the fitting portion is restrained by the fitting, so that the posture becomes stable.

  In the present invention, as described in claim 5, in the press-fitting step, the metal fitting body may be supported by a body-side support means that supports a tip-facing surface at the tip. However, as in claim 6, the metal fitting body has a protruding polygonal portion having a relatively large diameter on the outer peripheral surface at the rear end or rear end portion. In the press-fitting step, the metal fitting main body may support the tip-facing surface of the screw-in polygon portion with the main body side support means. That is, the tip-facing surface that should support the metal fitting body depends on the shape or structure of the metal fitting body, and may be a portion that can support the relative movement of press-fitting the sheath tube into the main body.

  As described above, the configuration of the external terminal at the rear end or near the rear end of the terminal shaft varies depending on the terminal configuration of the counterpart (lead wire end), such as a screw terminal structure or a pin terminal structure. There is. On the other hand, in any of the external terminal configurations, a portion of the terminal shaft that protrudes rearward from the rear end of the metal fitting main body is directed from the front end side toward the rear end side. In order to seal the opening at the rear end of the metal fitting body, it is common to integrally provide a large diameter portion for compression that compresses an O-ring packing made of rubber or the like to the front end side through an insulating ring. According to the seventh aspect of the present invention, a great effect can be obtained when the external terminal at the rear end or near the rear end of the terminal shaft has such a configuration.

  In the invention according to claim 7, since the sealing ring packing can be compressed at the same time in the press-fitting step of the sheath tube into the main body, and the seal of the rear end of the main body can be secured, the caulking of the external terminal is separately provided. Since it is not necessary to perform compression when mounting by means of, for example, the assembly of the glow plug can be simplified. This effect in the present invention is extremely serious. That is, in the conventional method in which the distal end of the sheath tube is pushed and the rear end of the terminal shaft is press-fitted from the front end side of the main body, a ring packing or an insulating ring is attached before press-fitting as in the present invention. It can be said that it is impossible in that method to place or to integrally form a large diameter portion for compression that compresses the ring packing toward the tip side near the rear end portion of the terminal shaft. Therefore, conventionally, a process such as compression of the ring packing has to be performed separately after the press-fitting process of the sheath tube, leading to a decrease in manufacturing efficiency. On the other hand, the present invention can be said to be a remarkable effect in that these problems can be solved all at once. In addition, the attachment of the insulating ring and the ring packing is, for example, in the case where the large diameter portion for compression is formed integrally with the terminal shaft, the terminal shaft is configured to butt and connect two or more shaft parts, for example, What is necessary is just to butt-connect two or more shaft components, after attaching them to the shaft components with which the large diameter part for compression is integrally formed. The connection means may be each means such as welding, caulking, press-fitting, and screwing.

The longitudinal cross-sectional view of the glow plug manufactured by this invention, and the enlarged view of each part. The figure which showed the metal fitting main body before press-fit, and the sheathed heater assembly with a terminal shaft in manufacture of the glow plug of FIG. Explanatory drawing of the process of press-fitting the sheath tube which comprises the assembly of FIG. 2 in a metal fitting main body. FIG. 4 is an explanatory partial view of a press-fitting process for explaining another example in which the external terminal of the terminal shaft is changed in FIG. 3. FIG. 4 is an explanatory view of a press-fitting process for explaining another example in which the support means of the metal fitting body is changed in FIG. 3. The figure which showed the metal fitting main body before press-fit, and the sheath heater assembly with a terminal shaft in manufacture of the glow plug in which the external terminal is separate from the terminal shaft. Explanatory drawing of the process which press-fits the sheath tube which comprises an assembly in manufacture of the glow plug whose external terminal is a different body from the terminal shaft. The longitudinal cross-sectional view of an example of the conventional glow plug, and the enlarged view of the principal part. It is a figure explaining the conventional manufacturing method of the glow plug of FIG. 8, and is a figure explaining the press fit process of the sheath tube to a main body.

  The embodiment of the present invention will be described in detail with reference to FIGS. 1 to 3, but before that, the glow plug 101 manufactured in this embodiment will be described. However, this glow plug 101 is basically the same as that shown in FIG. 8 except for the external terminal portion, and has a cylindrical metal fitting body 11 extending in the direction of the axis G and the tip 12 side. The distal end 22 is fixed (fixed) to the tube, and the cylindrical sheath tube 21 extending in the direction of the axis G, the round shaft terminal shaft 41, and the like are configured as follows.

  The metal fitting body 11 has a cylindrical shape whose whole (cylindrical portion) has a substantially the same diameter and extends straight, and a cylindrical sheath tube closed by a spherical surface having a convex end 22 at a portion closer to the inner end. 21 is fixed. However, in this embodiment, the sheath tube 21 is formed so that its outer diameter is about 0.1 to 0.9 mm in diameter from the front end 22 side and the rear end 24 side at the intermediate portion in the axis G direction. The large-diameter portion (large-diameter portion for press fitting) 26 is provided over a predetermined length. On the other hand, the inner diameter of the metal fitting body 11 is the same over substantially the entire length, but the predetermined length portion of the portion corresponding to the large diameter portion 26 of the sheath tube 21 is smaller in diameter by about 0.1 mm than the others. It is formed in the small diameter portion (small diameter portion for press fitting) 13 so as to become. Then, the sheath tube 21 is press-fitted into the metal fitting main body 11 through the large-diameter portion 26 with respect to the small-diameter portion 13 of the main body 11, and the tip 22 protrudes from the tip 12 of the main body 11. Let it be fixed. The outer diameter of the large diameter portion 26 of the sheath tube 21 before press-fitting is, for example, φ4.4 mm, the inner diameter of the small-diameter portion 13 of the main body 11 is φ4.3 mm, and the design press-fitting allowance (tightening allowance) is 0. .1mm is set. Further, a heat generating coil (or a heat generating coil and a control coil connected in series with the rear end thereof, hereinafter referred to as a coil at the end; hereinafter also referred to as a coil at the end) 30 is formed at the front end of the sheath tube 21 toward the rear. Is arranged, and the tip is fixed to the tip in the sheath tube 21 by welding.

  On the other hand, a round bar (shaft) -like terminal shaft 41 arranged concentrically (coaxially) is provided in the main body 11, and the distal end side (lower side in FIG. 1) is the rear end of the sheath tube 21. It is inserted in 24 and fixed via a sealing material (insulating rubber) 35. The distal end 43 of the terminal shaft 41 is connected to the rear end of the coil 30 in the sheath tube 21. However, in this example, the terminal shaft 41 is a flange-like compression member that forms a part for compressing the rubber ring packing 60 via the insulating ring 65 at the rear end portion (upper end in the drawing) 43 protruding from the main body 11. A large-diameter portion 53 and an external terminal (round pin-shaped pin terminal) 51 having a circular cross section are integrally formed behind the large-diameter portion 53. The external terminal 51 is provided with a large-diameter portion 55 (engagement large-diameter portion) that constitutes an attachment means for engagement with the socket-shaped terminal of the other party (lead wire end portion). Although not shown, the sheath tube 21 is filled with an insulating material (magnesia powder or the like) to ensure insulation between the coil 30 and the inner surface of the sheath tube 21, and the terminal shaft 41 and the metal fitting body. The heat generating coil 30 is heated by resistance by energizing between 11 and the distal end portion of the sheath tube 21 generates heat. Note that the assembly including the sheath tube 21, the coil 30, and the terminal shaft 41 constitutes a sheath heater assembly in this example.

  Incidentally, in such an assembly, the coil 30 is connected to the tip 43 of the terminal shaft 41, and the tip 43 side of the terminal shaft 41 together with the coil 30 is inserted into the sheath tube 21, so that the tip of the coil 30 is connected. Swaging processing in which the outer periphery of the sheath tube 21 itself is compressed and compressed by interposing a sealing material inside the rear end of the tube 21 after welding to the tip of the tube 21 and filling the inside with an insulating material. And the terminal shaft 41 is fixed. However, in this example, since the flange-shaped compression large-diameter portion 53 and the external terminal (pin terminal) 51 are integrally formed behind the terminal shaft 41, the terminal shaft 41 is formed by abutting a thin shaft portion 47 positioned on the front end side and a thick shaft portion 48 positioned on the rear end side and connecting them by welding or the like at the butting surface 49. Before the connection, the ring packing 60 and the insulating ring 65 are fitted on the terminal shaft 41.

  Further, a screw-in polygonal portion 16 that forms the head of a polygonal bolt (hexagonal bolt) on the outer periphery of the rear end 15 of the metal fitting body 11 constituting the glow plug 101 of this embodiment is larger than the cylindrical portion. The ring packing 60 and the like are arranged as shown in FIG. 1 in the arrangement portion 17 formed in an enlarged diameter inside the polygonal portion 16. That is, the ring packing 60 that is externally fitted to the front end side of the flange-shaped compression large-diameter portion 53 in the rear end portion of the terminal shaft 41 protruding from the rear end 15 of the main body 11 in the arrangement portion 17. An insulating ring 65 is disposed. Under the state where the rear end portion of the terminal shaft 41 is held at the center of the main body 11, the front end surface of the flange-shaped large-diameter portion 53 for compression passes the ring packing 60 forward through the insulating ring 65. The main body 11 and the terminal shaft 41 are electrically insulated from each other through the insulating ring 65 while securing the seal in the main body 11. A screw 18 for mounting on a diesel engine (not shown) is formed around the axis G on the distal end side (lower side in the drawing 1) of the outer periphery of the main body 11 from the screw-in polygon portion 16. .

  Of the method for manufacturing such a glow plug 101, the first embodiment of the press-fitting process of relatively press-fitting the sheath tube 21 constituting the sheath heater assembly as described above into the metal fitting body 11 will be described. This will be described with reference to FIGS. 2 is a view showing the metal fitting body 11 before press-fitting and the sheath heater assembly 20 with a terminal shaft, and FIG. 3 is a view for explaining the press-fitting process. The sheath heater assembly 20 includes a sheath tube 21 containing a coil 30 and a terminal shaft 41. As described above, in this example, the terminal shaft 41 has a butt-welded structure and is located near the rear end. The flange-shaped compression large-diameter portion 53 and the external terminal (pin terminal) 51 are integrally formed, and the ring packing 60 and the insulating ring 65 are provided on the distal end side of the flange-shaped compression large-diameter portion 53. Are externally fitted.

  In this example, such an assembly 20 has a rear end 45 of the terminal shaft 41 facing down, and the rear end of the assembly 20 is attached to, for example, a bed of a press (compression) device (not shown). It supports by 81 (refer FIG. 2). At this time, the ring packing 60 may be positioned such that the insulating ring 65 is positioned on the distal end side of the flange-shaped large diameter portion 53 for compression. In this example, the shaft-side support means (also referred to as a shaft-side support) 81 has a block shape, and a support hole 85 penetrating vertically is provided at the center of the upper surface 83. The support hole 85 is formed so that the inner diameter of the support hole 85 can be inserted in a state where the shaft portion of the external terminal (pin terminal) 51 is fitted with a minute gap. Therefore, an external terminal (pin terminal) 51 is inserted here, and the assembly 20 is erected with the sheath tube 21 facing upward, and is a large attachment means for engaging with the socket-shaped terminal of the other party (lead wire end). The annular rear end facing surface 56 of the diameter portion (engagement large diameter portion 55) 55 is supported by the periphery of the support hole 85 in the upper surface 83 of the shaft side support 81. The support hole 85 may be a hole with a bottom, and the rear end (surface) 45 of the terminal shaft 41 may be supported by the bottom.

  Next, the metal fitting body 11 is fitted on the sheath tube 21 forming the sheath heater assembly 20 from the distal end 22 side so as to be coaxial with the rear end 15 of the body 11 facing down (see FIGS. 2 and 3). (See left figure). That is, the distal end 22 of the sheath tube 21 is relatively inserted into the metal fitting body 11 from the opening of the rear end 15. At this time, the metal fitting 11 is locked, although the rear end of the press-fitting small-diameter portion 13 in the portion closer to the inner tip of the metal fitting 11 is lowered to the tip of the press-fitting large-diameter portion 26 of the sheath tube 21 by its own weight (see FIG. (See left figure 3). In this state, the distal end 22 of the sheath tube 21 partially protrudes from the distal end 12 of the main body 11. That is, the large-diameter portion 26 for press-fitting of the sheath tube 21 is thinner than the portion other than the small-diameter portion 13 for press-fitting of the main body 11, and the distal end side of the large-diameter portion 26 for press-fitting is thinner than the small-diameter portion 13 for press-fitting. Each cross section is circular and concentrically formed.

  On the other hand, the press ram (not shown) located above the bed in the press apparatus has a main body having an annular bottom portion 93 formed so as to be able to press the front end 12 surface (front end facing surface) of the metal fitting body 11. Side support means (support body) 91 is attached coaxially to the sheath tube 21. However, the support means 91 is formed in a sleeve shape having a hole 95 penetrating vertically so that the distal end 22 portion of the sheath tube 21 can be received in a loosely inserted state. The support body (sleeve) 91 is a circular positioning having an inner wall surface that restrains the outer peripheral surface near the tip 12 of the metal fitting body 11 with a minute gap fit and can hold the posture correctly up and down. A structure having a hole 97 is provided, and a chamfered guide is formed at a corner between the lower surface 99 of the support means 91 and the inner peripheral surface of the hole 97.

  Then, the pressing ram in the pressing device is pushed down so that the distal end 22 portion of the sheath tube 21 is received in the support 91 in a loosely inserted state, and the distal end 12 surface of the metal fitting body 11 is pressed by the inner annular bottom portion 93. Like that. Then, as shown on the right side of FIG. 3, the support body 91 is pushed down by a predetermined stroke, and the sheath tube 21 is pressed into the set position in the main body 11 with the force F. By doing so, the sheath tube 21 constituting the sheath heater assembly 20 is press-fitted into a predetermined position in the metal fitting body 11. Further, in this example, since the flange-shaped compression large diameter portion 53 near the rear end 45 of the terminal shaft 41 compresses the insulating ring 65 and the ring packing 60, the seal at the opening of the rear end 15 of the main body 11 is also performed. The glow plug 101 secured at the same time is obtained simultaneously through this press-fitting process. As understood from this, in this example, the sheath tube 21 is set to be press-fitted into the metal fitting body 11 until the ring packing 60 is appropriately compressed.

  In such a manufacturing method of the present example, the tip 22 of the sheath tube 21 is not supported in the press-fitting step, so that the tip 22 is not crushed (deformed). Further, in the press-fitting process, an excessive compressive force is not applied in the direction of the axis G even between the front and rear from the distal end 22 of the sheath tube 21 to the large-diameter portion 26 for press-fitting. Therefore, it is possible to effectively prevent the inclination or bending from occurring on the distal end 22 side of the sheath tube 21. In addition, in this example, the assembly as the glow plug 101 can be completed as described above by performing the press-fitting process of the sheath tube 21. Therefore, unlike the conventional method, after the press-fitting, there is no need to separately compress the ring packing 60, so that the productivity of the glow plug 101 can be increased.

  In the above example, the case where the external terminal 51 on the rear end 45 side of the terminal shaft 41 is a pin terminal integrated with the terminal shaft 41 has been described. However, as shown in FIG. 4, even when the external terminal 51 is a screw terminal integrated with the terminal shaft 41, it can be press-fitted in the same press-fitting process, and the same effect can be obtained. That is, as shown in FIG. 4, a flange-shaped large diameter portion 53 for compression formed so that the ring packing 60 can be compressed via the insulating ring 65 is provided on the base end side of the screw terminal. By forming it integrally, it can be embodied in the same manner as in the above example. In FIG. 4, since only the external terminal is different from the previous example, the same reference numerals are given to the same parts.

  Further, as shown in FIG. 8, the external terminal 51 is separate from the terminal shaft 41 and is attached to the rear end 45 of the terminal shaft 41 by a caulking method. If the sheath tube 21 is fixed in advance before the press fitting of the sheath tube 21 to the main body 11 together with 60, the same effect can be obtained. In addition, when the external terminal is a screw terminal, the flange-shaped compression large-diameter portion that compresses the ring packing through the insulating ring is separately fixed to the rear end of the terminal shaft. If the sheath tube is fixed in advance before the sheath tube is press-fitted into the main body, the same effect can be obtained.

  In the above embodiment, the case where the front end 12 of the main body 11 is pushed down and press-fitted has been described. However, it is obvious that the rear end 45 of the terminal shaft 41 may be pushed up. Further, it is obvious that the press-fitting may be performed with the front end 12 of the main body 11 facing down and the rear end 45 of the terminal shaft 41 facing up. In the present invention, the metal body 11 is supported by the shaft-side support means at the rear end or the rear end surface of the terminal shaft 41 constituting the sheath heater assembly 20 at the rear end portion. Thus, it is only necessary that the sheath tube 21 can be press-fitted into the main body 11 by causing the metal fitting main body 11 to perform a relative movement in which the shaft-side support means is pushed forward. As understood from these, the rear end of the terminal shaft or the front end of the main body may not be fitted into the hole as in the above example, but may be simply supported.

  In the above embodiment, the case where the main body 11 is supported at the distal end 12 of the main body 11 (the front end-facing surface) is illustrated, but the support is shown in FIG. Like the supporting means 91b, it is also possible to support the tip-facing surface 16b of the screw-in polygon part 16 formed in a protruding shape on the outer peripheral surface of the rear end 15 part of the main body 11 (see the left figure of FIG. 5). ). In this case, as shown in the right diagram of FIG. 5, after the support, the support means 91b is pushed down, so that press-fitting can be performed in the same manner as in the above example. Note that FIG. 5 differs from that of FIG. 3 only in this support means. Therefore, the same parts and corresponding parts are denoted by the same reference numerals, and only the support means 91b will be described. That is, the support means 91 b has an annular bottom portion 93 formed so as to be able to press the distal end facing surface 16 b of the screw-in polygon portion 16 of the metal fitting body 11, and is attached coaxially to the sheath tube 21. ing. However, the support means 91b is formed in a sleeve shape having a hole 95 penetrating vertically so as to be able to receive the portion of the screw 18 of the main body 11 in a loosely inserted state. The support 91b is a circular positioning hole having an inner wall surface that restrains the outer peripheral surface of the screw-in polygon portion 16 of the metal fitting body 11 in a minute gap fitting state so that the posture can be correctly held up and down. A chamfered guide is formed at the corner between the lower surface 99 of the support means 91 and the inner peripheral surface of the hole 97.

  Now, another example of the present invention will be described with reference to FIGS. However, what is manufactured in this example is the same configuration as the glow plug 201 shown in FIG. The sheath heater assembly 20 is also the same as that shown in FIG. 9 and extends rearward with the thick shaft portion 48 remaining behind the terminal shaft 41. That is, in this example, after the sheath tube 21 constituting the sheath heater assembly 20 with the terminal shaft 41 is pressed into the main body 11, the rear end 15 of the main body 11 is separately sealed and the external terminal 51 is fixed. In this case, a glow plug is manufactured. Therefore, the difference from the above example is that, as shown in FIGS. 6 and 7, in the step of press-fitting the sheath tube 21 constituting the sheath heater assembly 20 with the terminal shaft 41 into the main body 11, the terminal shaft 41 is provided. The rear end (part near the rear end) 45 is inserted into a support hole 85 with a bottom 86 provided in the terminal-side support body 81, the sheath heater assembly 20 is erected, and a predetermined stroke is press-fitted into the main body 11. It is only the point which is trying to do. Therefore, the same reference numerals are assigned to the same parts, and detailed description thereof is omitted. The depth of the support hole 85 is set so that the rear end 15 surface of the metal fitting body 11 to be press-fitted does not interfere with the upper surface 83 of the support means 81.

  In this example, the ring packing 60 is not compressed in the press-fitting process of the sheath tube 21 to the main body 11. For this reason, it is not necessary to attach the insulating ring 65 for compression in advance, and the press-fitting process can be performed without considering the compression of the ring packing 60. Therefore, it is easy to manage the dimensional accuracy of the press-fitting stroke and parts. Become. Since the attachment of the external terminal 51 is performed after the sheath tube 21 is press-fitted into the main body 11, it may be performed in the same manner as described in the glow plug shown in FIG.

  The method for manufacturing a glow plug of the present invention is not limited to the above-described example, and can be embodied with appropriate modifications within a range not departing from the gist thereof. As a matter of course, the glow plug to which the present manufacturing method is applied is not limited to the structure described above. For example, in the glow plug described above, the sheath tube used in the glow plug is embodied with a large-diameter portion for press-fitting with different diameters. However, in this case, it is preferable that the inner diameter of the metal fitting body, which is a press-fitting counterpart member, is set so that the press-fitted state is ensured only at the tip or a portion near the tip. However, if the sheath tube has a straight tube shape with the same diameter over the entire length, even if no compression force is applied to the tip surface itself at the start of press-fitting, a compression force is applied to the shaft portion from the tip to the rear. There is a possibility of occurrence of tilting and bending. Therefore, it is preferable that the distal end side of the sheath tube including the portion protruding from the distal end of the main body is formed thinner than others, and the outer diameter thereof is made smaller than the minimum inner diameter of the main body.

DESCRIPTION OF SYMBOLS 11 Metal fitting body 12 Tip of metal fitting body 13 Small diameter portion for press fitting of metal fitting body 15 Rear end of metal fitting body 16 Polygonal portion for screwing of metal fitting body 16b Front surface facing screwing polygonal portion 20 Sheath heater assembly with terminal shaft DESCRIPTION OF SYMBOLS 21 Sheath tube 22 End of sheath tube 26 Large diameter part for press fit of sheath tube 30 Resistance heating element 41 Terminal shaft 45 Rear end of terminal shaft 51 External terminal for lead wire connection 53 Large diameter part for compression 60 Ring packing 65 Insulating ring 81 Shaft side support means 85 Shaft side support means support hole 91 Main body side support means 101, 201 Glow plug

Claims (7)

A sheathed heater with a terminal shaft is provided with a resistance heating element that generates heat when energized in a sheath tube with a closed tip, and includes a terminal shaft that is fixed to the sheath tube and extends rearwardly. The sheath tube constituting the assembly includes
Relatively, the distal end of the sheath tube is press-fitted and fixed in a cylindrical metal fitting body with a predetermined amount protruding from the tip of the metal fitting body, and after the terminal shaft after the fitting. In a method of manufacturing a glow plug having a configuration in which an end protrudes a predetermined amount from the rear end of the metal fitting body,
The distal end of the sheath tube constituting the sheath heater assembly with the terminal shaft is relatively inserted into the metal fitting body from the opening at the rear end thereof,
The rear end facing surface at the rear end or the rear end portion of the terminal shaft constituting the sheath heater assembly with the terminal shaft is supported by the shaft side support means, and under this state, the metal body is attached to the metal fitting body. A glow plug manufacturing method comprising a press-fitting step of press-fitting the sheath tube into the metal fitting body by causing the shaft-side support means to perform a relative movement that is moved forward. In a state where the sheath tube is fixed to the metal fitting body as a glow plug, the outer diameter of the sheath tube is at least a part of the longitudinal portion of the portion that is to be located inside the metal fitting body than the sheath tube itself. While having a large-diameter portion for press-fitting that has a relatively large diameter,
The metal fitting body has a small diameter portion for press-fitting whose inner diameter is relatively smaller than that of the metal fitting itself so that the sheath tube can be press-fitted in the large-diameter portion for press fitting. Item 2. A method for manufacturing a glow plug according to Item 1.   In the press-fitting step, the sheath heater assembly supports a rear end-facing surface at a rear end of the terminal shaft or a portion near the rear end, with the front end of the sheath tube up or down. Item 3. A method for manufacturing a glow plug according to Item 1 or 2.   The shaft-side support means has a support hole for fitting the rear end or rear end portion of the terminal shaft with a clearance fit, and supports the rear end or rear end portion of the terminal shaft. The method for manufacturing a glow plug according to claim 1, wherein the terminal shaft is supported by being fitted into a hole.   5. The method for manufacturing a glow plug according to claim 1, wherein, in the press-fitting step, the metal fitting body is supported by a body-side support unit that supports a tip-facing surface at a tip thereof. The metal fitting body has a screw-in polygonal portion having a relatively large diameter on the outer peripheral surface at a rear end or a portion near the rear end,
The glow plug manufacturing method according to any one of claims 1 to 5, wherein in the press-fitting step, the metal fitting body supports a tip-facing surface of the screw-in polygonal portion. Before the press-fitting step, the terminal shaft constituting the sheath heater assembly is
In the terminal shaft, a ring packing is placed on the front end side through an insulating ring in order to seal the rear end of the metal fitting body at the rear end portion that protrudes backward from the rear edge of the metal fitting body. A compression large-diameter portion to be compressed is integrally provided, and an external terminal for connecting a lead wire is provided behind the compression large-diameter portion, and further, from the compression large-diameter portion On the front end side, from the front end side toward the rear end side, a ring packing and an insulating ring are attached in an outer fitting shape,
In the press-fitting step,
The method for manufacturing a glow plug according to claim 1, wherein the large-diameter portion for compression compresses the ring packing through the insulating ring.

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