JP2011069550A - Glow plug and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To maintain insulating powder at an intended filling density only by pressurization in the axial direction after the insulating powder is filled within a sheath tube having a built-in resistance heating element, in manufacturing a sheath heater for a glow plug by filling the insulating powder within the sheath tube. <P>SOLUTION: The resistance heating element 30 has a spiral structure formed by spirally winding a metal plate while maintaining the gap between respective wound plates within the sheath tube 21 so as to form a spiral shape when viewed from the rear end side. One end 33 of the resistance heating element 30 positioned on the most outer peripheral side of the spiral structure is welded to the inner face 27 of the sheath tube 21. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

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

  Such a glow plug has the structure shown in FIG. 12 (Patent Document 1). The glow plug 1 has a cylindrical shape, and a cylindrical metal fitting body (hereinafter also simply referred to as a main body) 10 provided with a screw 13 on the outer peripheral surface so as to be fixed to an engine head (not shown) by a screwing method. And a sheath heater (electrically heated sheath heater) 20 fixed inside thereof and the like. The sheath heater 20 is fixed in such a manner that the distal end 22 side (about half of the distal end side in FIG. 12) of the sheath tube 21 forming the sheath heater 20 protrudes from the distal end 11 of the main body 10. As will be described in detail later, the sheath heater 20 has a coil-like resistance heating element 30 that generates heat when energized in the sheath tube 21 with the tip 22 closed, and has one end (tip) 33 welded to the tip 22 of the tube. Built in shape. On the other hand, on the inner side (hollow part) of the metal fitting body 10, a terminal shaft (metal shaft) 40 for energization is fixed, with the distal end being inserted and fixed near the rear end 23 of the sheath tube 21. . The terminal shaft 40 is electrically connected to the resistance heating element 30 via its tip 41, and the rear end thereof is fixed while maintaining insulation at the rear end of the main body 10. That is, the rear end of the terminal shaft 40 protrudes from the rear end of the main body 10, and an O-ring packing 51 and an insulating ring 53 are fitted on the rear end portion, and these are attached to the rear end of the main body 10. It arrange | positions at the inner peripheral side of the polygon part 15 for screwing. In this arrangement state, the cylindrical portion 57 of the energizing terminal 55 is fitted on the rear end portion of the shaft 40 and the outer ring is pressed against the insulating ring 53 by the flange on the front end side. The glow plug 1 is assembled by crimping the surface to a reduced diameter. In addition, in this application document, regarding the glow plug 1, the sheath heater 20 constituting the glow plug 1, and the other components, the front end refers to the lower end in FIG. 12, and the rear end is the opposite end (upper). Say.

  By the way, the detailed configuration of the sheath heater 20 itself constituting the glow plug 1 is as follows. That is, the heater 20 includes a sheath tube 21 made of stainless steel or a Ni-base heat-resistant alloy and a resistance heating element (coil) 30 disposed with the tip 33 welded therein as described above, as follows. It is configured. That is, the sheath tube 21 has a bottomed cylindrical shape formed in a substantially hemispherical shape having a convex end 22. The resistance heating element (heating coil) 30 is made of iron-chromium alloy, nichrome, or the like. In the figure, the metal wire (the wire having a circular cross section) is cylindrical, and the vine winding has a predetermined length. (Helix) coil spring structure. In the sheath heater 20 shown in the figure, a resistance coil for current control made of a metal (for example, cobalt iron alloy) having a positive and large resistance temperature coefficient at the rear end of the resistance heating element 30 (opposite to the coil of the resistance heating element). 32 are connected (welded) in series. Thus, in the same figure, the tip 41 of the terminal shaft 40 inserted from the opening at the rear end in the sheath tube 21 is connected to the rear end of the current control resistance coil 32 by welding. The resistance heating element 30 is heated by energizing between the terminal shaft 40 and the metal fitting body 10. The sheath tube 21 may have the same diameter (straight) over the entire length, but the one shown in FIG. 12 has a cylindrical shape with a different diameter near the tip.

  The sheath tube 21 is actually filled with ceramic (for example, MgO) powder (insulating powder) that is electrically insulating and heat resistant, although not shown in order to avoid complication of the drawing. ing. As a result, prior and subsequent electrical insulation is ensured between the inner surface of the sheath tube 21 and a coil (hereinafter also simply referred to as a coil) or a terminal shaft 40 that forms a resistance heating element and between the windings that form the coil itself. In addition, these are stably fixed in the sheath tube 21. In order to secure such fixation, the insulating powder in the tube 21 is compressed to maintain a predetermined filling density. And between the inner peripheral surface near the rear end 23 of the sheath tube 21 and the outer peripheral surface of the terminal shaft 40, a cylindrical (or annular) sealing material (for example, an insulating material) (for example, A heat-resistant rubber tube) 65 is inserted, and the inside of the tube 21 (insulating powder) ahead of the sealing material 65 is sealed (sealed) while maintaining insulation therebetween.

  By the way, the sheath heater 20 having the above-described configuration is manufactured or assembled through the following steps. Description will be made based on the manufacturing process diagram schematically shown in FIG. That is, for the sheath tube 21, as shown in FIG. 13-A, a lower end (a portion serving as the tip of the sheath tube 21) is formed through a number of molding processes from a pipe (circular tube) having both ends opened. In addition to forming a hemispherical portion, the diameter of the hemispherical portion is reduced concentrically with the pipe at the center of the tip of the hemispherical portion, and a reduced diameter cylindrical portion 21s protruding toward the tip is formed to form a sheath tube work product 21a. Keep it. On the other hand, as shown in FIG. 13-B (left), the resistance heating element (heating coil) 30 is formed such that a part of its tip is formed as a small diameter portion 33b. Then, the current control resistor coil 32 is connected to the rear of the heat generating coil, and the tip of the terminal shaft 40 is welded to the rear end thereof to form a coil (resistance heat generating body) assembly with a terminal shaft. Keep it.

  Next, as shown in FIGS. 13B and 13C, the coil assembly with the terminal shaft is inserted into the sheath tube work product (sheath tube before welding of the resistance heating element) 21a from the opening at the rear end thereof. The small diameter portion 33b at the tip is inserted into the reduced diameter cylindrical portion (hole) 21s (see FIG. 13-C). In this state, the small diameter portion 33b is melted and solidified by welding together with the reduced diameter cylindrical portion 21s. As a result, as shown in FIG. 13-D, the distal end of the sheath tube work product 21a is blocked by melting and solidification of the distal end portion, and the distal end 33 of the resistance heating element (coil) 30 is sheathed. A sheathed heater work 20a with a terminal shaft is welded to the tip 22 in the tube 21.

  The sheath heater work-in-process 20a thus obtained is the one shown in FIG. 14-A, and thereafter, as shown in FIG. 14-B, the rear end opening (inside the tube rear end 23 of the tube 21). A predetermined amount of the insulating powder 60 is poured into the tube 21 through a gap between the peripheral surface and the outer peripheral surface of the terminal shaft 40 and filled. Thereafter, as shown in FIG. 14C, the above-described cylindrical sealing material 65 is placed between the inner peripheral surface of the portion near the rear end of the sheath tube 21 in this state and the outer peripheral surface of the terminal shaft 40. Intervene.

  Next, in order to increase the packing density of the insulating powder 60 to a predetermined value, the sheath tube 21 is added in a reduced diameter (diameter direction) as indicated by a horizontal arrow in FIG. Perform tightening (swaging). In this way, the inner insulating powder 60 has a desired packing density. Thus, this is press-fitted into the above-described metal fitting body 10 and assembled as the glow plug 1 as described above.

  Incidentally, in the manufacturing process of the sheath heater 20 with the terminal shaft 40 described above, the sheath tube 21 is crimped in a reduced diameter, and this is filled with the insulating powder 60 from the opening of the rear end 23 into the sheath tube 21. Then, simply pressing (pressurizing) it in the direction of the axis G1 from the rear does not provide the insulating powder 60 with a uniform or desired filling density. This is due to the following reason. In the sheath heater 20 configured as described above, the built-in resistance heating element 30 and the like has a coiled coil structure, and the tip 41 of the terminal shaft 40 abuts or fits to the rear end (opening) of the coil. It is connected in a shape, and the rear end of the coil is closed. Therefore, if the insulating powder 60 is filled from the rear end side of the sheath tube 21 and pushed in from the rear side under such a coil structure and the arrangement condition of the terminal shaft 40 with respect to the coil structure, only the inside of the coil structure can be used. Since the same powder is difficult to enter even between the windings, the desired packing density cannot be obtained. Therefore, as shown in FIG. 14-C, the sheath tube 21 filled with the powder 60 is crimped to a reduced diameter so that the filling density is uniform and sophisticated.

JP 2001-330249 A

  Since the glow plug overheats the combustion chamber with the heat at the tip of the sheath tube, the temperature at the tip of the sheath tube is the most important. However, in the conventional sheath heater 20 as described above, even if the shape of the sheath tube 21 or the packing density of the insulating powder is improved, the resistance heating element 30 has a coil structure that extends later, so There is a limit to improving the heat generation efficiency because it becomes longer in the axial direction.

  As described above, in the configuration of the conventional sheath heater 20, in order to make the insulating powder 60 filled in the sheath tube 21 into a desired filling density due to its manufacturing method, after filling it, a separate process is performed separately. However, the process of crimping the insulating powder inside by crimping the sheath tube 21 into a reduced diameter is required. For this reason, there is a problem that the manufacturing process is increased and complicated for the process, resulting in an increase in manufacturing cost.

  Further, in the process of manufacturing such a sheath heater 20, the resistance heating element 30 is welded to the distal end 22 in the sheath tube 21, and the sheath provided with the reduced diameter cylindrical portion 21s at the distal end as described above from the pipe. The tube work 21a is formed in advance, and the tip wire portion 33b of the resistance heating element 30 is inserted into the reduced diameter cylindrical portion 21s, and is welded in such a manner that it is melted together with the reduced diameter cylindrical portion 21s. On the other hand, when forming the reduced-diameter cylindrical portion 21s at the tip of the sheath tube work-in-progress 21a, there is inevitably a variation in the length and other dimensions (an error in molding). To do. In addition, even in the subsequent welding process, the amount of melting (solidification amount) of the portion including the reduced diameter cylindrical portion 21s also varies. For this reason, after the solidification of the molten metal by the welding, an excessive variation may occur in the thickness of the tip (bottom) 22 of the sheath tube 21. On the other hand, in the glow plug sheath heater 20, the tip 22 of the sheath tube 21 plays an important role as a heat generating portion. Therefore, such a variation gives a variation in the heat generation performance as a glow plug.

The present invention has been made in view of the above-described structure of the sheath heater forming the glow plug and problems caused by the manufacturing process thereof, and the object thereof is as follows.
First, the heat generation efficiency at the tip of the sheath heater is increased.
Secondly, the insulating powder is filled into the sheath tube from the opening at the rear end thereof, and the insulating powder can be maintained at a desired filling density only by pressing in the axial direction. In other words, the sheath tube diameter reducing caulking step for securing the filling density can be omitted, and the sheath heater can be efficiently manufactured at low cost, resulting in low cost of the glow plug. Plan.
Third, the variation in the heat generation performance of the sheath heater is reduced. The above three points are the object of the present invention.

In order to solve the above-mentioned problem, the invention described in claim 1 is as follows.
A sheath tube with a closed tip;
A terminal shaft for energization inserted in the sheath tube;
It is arranged in the sheath tube, and one end side of itself is welded to the distal end or a portion near the distal end in the sheath tube, while the other end side is electrically connected to the terminal shaft and generates heat when energized. A resistance heating element;
Insulating powder filled in the sheath tube;
In a glow plug having a sheath heater with
The resistance heating element is a spiral structure in which a metal plate is formed in a spiral shape while maintaining a space between the winding plates so as to form a spiral shape when viewed from the rear end side in the sheath tube. Wherein the one end side of the resistance heating element located on the outermost peripheral side of the spiral structure is welded to the distal end or a portion closer to the distal end in the sheath tube.

  According to a second aspect of the present invention, the other end side of the resistance heating element located on the innermost peripheral side of the spiral structure is electrically connected to a tip end or a portion closer to the tip end of the terminal shaft. The glow plug according to claim 1, wherein:

  The invention according to claim 3 is characterized in that the spiral structure is spirally wound around a virtual axis in a plane along a plane perpendicular to the virtual axis. A glow plug according to claim 1 or 2. According to a fourth aspect of the present invention, the spiral structure has a spiral shape in which the spiral plate portion is located at the rear side toward the other end side away from the one end side of the resistance heating element. A glow plug according to claim 1 or 2, wherein

  According to a fifth aspect of the present invention, the conduction cut-off of the winding plate portion where the welded portion energizing area at the welded portion between the one end side of the resistance heating element and the inside of the sheath tube is located on the inner peripheral side of the welded portion is provided. The glow plug according to claim 1, wherein the glow plug is held larger than an area.

  According to a sixth aspect of the present invention, in the resistance heating element, the resistance value per unit length of the winding plate portion located on the one end side is per unit length of the winding plate portion located on the inner peripheral side thereof. The glow plug according to claim 1, wherein the glow plug is formed so as to be larger than a resistance value of the glow plug.

  In the invention according to claim 7, the terminal shaft has a cross-sectional area of a portion near the tip including a portion where the other end side of the resistance heating element is electrically connected, and a cross-sectional area of a rear portion thereof. The glow plug according to any one of claims 1 to 6, wherein the glow plug is formed to be smaller than the glow plug.

  According to an eighth aspect of the present invention, the resistance heating element is positioned and arranged in the sheath tube in a state where the terminal shaft is joined to the other end side, and is disposed at a distal end or a portion closer to the distal end of the sheath tube. The one end side of the resistance heating element is formed in a spiral spring that is pressed against the inner surface of the sheath tube by a spring property before being welded. Is a glow plug.

  According to the ninth aspect of the present invention, the sheath heater is configured to provide a resistance heating element with a terminal shaft by electrically connecting a distal end of the terminal shaft or a portion closer to the distal end to the other end side of the resistance heating element. Placing the resistance heating element with the terminal shaft in the sheath tube, and welding the one end side of the resistance heating element to the distal end or a portion closer to the distal end in the sheath tube; and After filling the sheath tube with insulating powder from the opening at the rear end, the insulating powder is compressed toward the distal end side from the opening at the rear end of the sheath tube to maintain the insulating powder at a predetermined packing density. The method for manufacturing a glow plug according to claim 1, wherein the method is manufactured by including the step of:

  In the present invention, the resistance heating element is not a spiral coil structure that extends forward and backward as in the prior art, but a spiral structure as described above. And since it has the structure which welded the said one end side of the resistance heating element to the front-end | tip in a sheath tube or a site | part near a front-end | tip, it fills the sheath tube with insulating powder from a rear end, and has predetermined | prescribed axial direction. By compressing with a compressive force, the insulating powder can be maintained at a desired predetermined packing density, including between the winding plates of the resistance heating element forming the spiral structure. Therefore, there is no need for a caulking step with a reduced diameter of the sheath tube as in the manufacture of a conventional sheath heater. As a result, the manufacturing efficiency of the sheath heater can be improved, and the cost of the glow plug can be reduced.

  Moreover, in the conventional sheath heater, as described in the background art, in the manufacture, the tip of the resistance heating element having a coil structure is welded to the tip of the sheath tube. It was necessary to prepare a molded body having a reduced diameter cylindrical portion (hole) protruding toward the front at the center of the hemispherical portion. In the welding, it is necessary to insert a small diameter portion at the tip of the resistance heating element into the reduced diameter cylindrical portion, and to melt and solidify it together with the reduced diameter cylindrical portion. As a result of variations in the wall thickness at the tip (bottom) of the tube, the heat generation performance may vary. On the other hand, in the present invention, the sheath tube before the tip of the resistance heating element is welded can be used with the tip closed. And the sheath tube with such a closed end is deeply drawn from a metal plate material or extruded from a shaft member, so that the thickness of the tip (bottom) is high. It can be easily molded with precision. Therefore, after the resistance heating element forming the spiral structure is inserted and arranged in such a bottomed tube, one end side of the resistance heating element located on the outermost peripheral side is connected to the distal end in the sheath tube. Alternatively, it can be easily welded to the portion near the tip by welding. In addition, since the welding does not give variations to the wall thickness at the tip of the tube, it is possible to obtain a sheath heater with small variations in heat generation performance.

  Furthermore, since the resistance heating element of the present invention has a spiral structure as described above, the tip of the sheath tube or a portion close to the tip can be concentrated and efficiently arranged by placing it close to the tip of the sheath tube. Can be heated. That is, according to the present invention, the heat generation efficiency at the tip of the sheath heater can be increased. On the other hand, in the resistance heating element of the present invention, as described in claims 1 and 2, the metal plates are spaced apart from each other so as to form a spiral when viewed from the rear end side in the sheath tube. It is only necessary to form a spiral structure that is held and formed in a spiral shape. Accordingly, as described in claim 4, the spiral structure has a spiral structure (conical spiral structure) that is located rearward as it is located farther from the one end side toward the other end side. However, when formed in a spiral shape wound in a plane as described in claim 3, compared to the conventional coil shape, at the tip or near the tip in the sheath tube, Since the entire resistance heating element can be arranged in a concentrated manner, the temperature rise characteristic or heat generation efficiency at the tip can be effectively improved.

  When the resistance heating element is formed and arranged as described in claim 4, it is possible to secure a large distance from the distal end of the sheath tube at the distal end of the terminal shaft. Therefore, it is possible to avoid a high temperature at the joint between the tip of the terminal shaft and the other end of the resistance heating element. Thereby, even when this joining is performed by welding, it is effective for preventing breakage due to heating of the heater.

  Further, as described in claim 5, when the welded portion energization area is maintained larger than the conduction cross-sectional area of the wound plate portion located on the inner peripheral side of the welded portion, the resistance of the welded portion is determined. Since the increase can be prevented, fusing (disconnection) by remelting of the welded portion can be prevented.

  By forming the resistance heating element as described in claim 6, the outer peripheral side of the resistance heating element located on the inner peripheral surface side of the distal end portion of the sheath tube can be efficiently and rapidly heated. In order to increase the resistance value, the conduction cross-sectional area on one end side of the resistance heating element located on the outermost peripheral side of the spiral structure may be made smaller than that on the other end side. Therefore, when the resistance heating element forming the spiral structure is wound in a spiral shape with a certain thickness, the width of the strip at the outermost peripheral portion may be reduced. That is, the resistance heating element forming the spiral structure may be formed by winding a strip having a certain thickness and width in a spiral shape, and thus the resistance heating element positioned on the outermost peripheral side of the spiral structure in this way. By making the conduction cross-sectional area on one end side smaller than that on the other end side, the distal end portion of the sheath tube can be heated quickly and efficiently.

  By forming the terminal shaft as described in claim 7, the thermal conductivity from the resistance heating element to the rear side of the coaxial can be reduced. This is effective in preventing the deterioration of If the terminal shaft is a solid bar (solid bar), the outer diameter of the portion closer to the tip may be made thinner than the rear portion.

  In addition, when the resistance heating element is configured as described in claim 8 and the one end portion which is the outermost peripheral side is pressed against the inner surface of the sheath tube by a spring property, the one end side and the sheath tube Can be easily welded by laser welding. In the case of having such a configuration, when the laser beam is irradiated from the outside of the sheath tube and the outward surface on one end side and the inner surface of the sheath tube are welded, they are separately held so as to contact each other. This is because no means is required.

The longitudinal cross-sectional view of the glow plug of this invention, the enlarged view of the sheath heater part, and the further enlarged view of the principal part. FIG. 2 is a cross-sectional view taken along line AA in FIG. 1 (viewed from the rear end side). BB sectional drawing of FIG. The figure which filled the insulating powder in FIG. It is a development view for explanation which forms a resistance heating element in a spiral shape with respect to a shaft for terminals, A is a front view for explanation, and B is a plan view for explanation. The principal part front view and partial enlarged view of a shaft for terminals with a resistance heating element. Sectional drawing for description of the process of manufacturing a sheath heater. The principal part expanded sectional view of another example of a sheath heater. The development view for explanation of the resistance heating element of another example of the shaft for a terminal with a resistance heating element. The development view for explanation of the resistance heating element of another example of the shaft for a terminal with a resistance heating element. The development view for explanation of the resistance heating element of another example of the shaft for a terminal with a resistance heating element. Sectional drawing which shows an example of the conventional glow plug, and the enlarged view of the sheath heater part. The typical explanatory view of the manufacturing process (until resistance heating element welding) of the conventional sheath heater. Explanatory drawing of the manufacturing process (after welding of a resistance heating element) of the conventional sheathed heater.

  Embodiments of the present invention will be described in detail with reference to FIGS. However, the glow plug 1 of this embodiment has the same configuration as that shown in FIG. 12 except for the internal structure of the sheath heater 20. Details will be described below. This glow plug 1 includes a metal fitting body (housing) 10 having a cylindrical shape (cylindrical shape), a sheath heater (heating tube) 20, and the like. The sheath heater 20 is formed of a sheath tube 21 with a distal end 22 closed, a resistance heating element 30 and the like inside the sheath tube 21, and more than half of the sheath tube 21 on the distal end 22 side is placed inside the metal body 10. It is fixed by press-fitting or the like in a state of protruding from the tip 11. The metal fitting body 10 is provided with a screw 13 on the outer peripheral surface near the rear end so that it can be screwed into a screw hole (mounting screw hole) of an engine head (not shown). Is provided with a polygonal part (for example, hexagonal part) 15 for screwing. Further, in the tubular metal fitting body 10, a current-carrying terminal shaft 40 inserted from the rear end (rear end portion) 23 in the sheath tube 21 is coaxial with the inner peripheral surface of the main body 10. It is arranged with insulation (space) retained.

  The terminal shaft 40 has a round bar (solid round bar) shape. In this example, from the tip (lower end in the drawing) 41 side, for example, a small diameter part 45 having an outer diameter of 1 mm, and a thicker medium diameter part. 46, and further toward the rear end portion 42, a thick large-diameter portion 47 and a round bar of different diameter concentrically increasing in thickness, and the rear end portion 42 protrudes rearward at the rear end of the main body 10. . A seal material (O-ring packing) is provided between the outer peripheral surface of the large-diameter portion 47 near the rear end of the shaft 40 and the inner peripheral surface expanded in the polygonal portion 15 at the rear end of the main body 10. 51, an insulating ring 53 is disposed, and an energizing terminal (terminal member) 55 externally fits the cylindrical portion 57 to a rear end portion (double hatched portion in the figure) 42 that protrudes rearward from the shaft. In addition, with the rear end of the insulating ring 53 being pressed forward, the cylindrical portion 57 is fixed by crimping to a reduced diameter.

  Next, the details of the sheath heater 20 constituting the glow plug 1 will be described. In this example, the sheath heater 21 made of stainless steel or Ni-base heat-resistant alloy, and the resistance heating element 30 disposed therein are used. From the above, it is configured as follows. That is, the sheath tube 21 has a cylindrical shape with a different diameter in which a portion near the tip is formed with a slightly small diameter, and has a bottomed cylindrical shape with the tip 22 closed. In this embodiment, the bottom forming the tip 22 is closed in a flat shape, and the small-diameter portion 24 near the tip is connected to the large-diameter portion 26 behind it via a tapered taper portion 25. Yes.

  The resistance heating element 30 is formed by spirally winding a thin strip (thickness 0.1 mm, width 1.0 mm) 31 made of a high melting point metal such as an iron chromium alloy or nichrome having a volume resistivity of 1 μΩ · m or more into a spiral spring shape. The formed spiral structure is formed (see FIGS. 2 to 5). That is, in this example, the resistance heating element 30 is formed in the above-described metal so as to form a spiral shape when viewed from the rear end 23 side (axis G1 direction) in the sheath tube 21, as shown in FIG. A strip made of steel is held between the winding plates, and a minute gap (0.05 to 0.2 mm) is held between the winding plates between the plate surfaces around the axis G1 of the sheath tube 21. Thus, it exhibits a spiral structure wound three to four times. However, when the resistance heating element 30 is in a free state, the resistance heating element 30 has a spiral shape that is wound in a plane around a virtual axis along a plane perpendicular to the virtual axis. The resistance heating element 30 is made of a single material having a temperature characteristic in which the resistance value at 1000 ° C. is in the range of 0.985 to 1.190 when the resistance value at 23 ° C. is 1. preferable.

  The resistance heating element 30 forming the spiral structure is disposed in the sheath tube 21 while maintaining insulation at a very small distance from the tip (bottom) 22 thereof. In this example, the plate surface of the one end 33 of the resistance heating element 30 located on the outermost peripheral side of the spiral structure is near the tip (bottom) 22 of the inner peripheral surface 27 in the sheath tube 21 ( 2 are overlapped with each other and welded at a position indicated by a thick line in FIG. 2, for example, by laser welding. The welded portion between the one end 33 and the sheath tube 21 may be the tip (bottom) 22 thereof. That is, one end 33 side of the resistance heating element 30 located on the outermost peripheral side of the spiral structure may be bent and welded so as to be in contact with the tip (bottom) 22. In this example, the other end 35 of the resistance heating element 30 located on the innermost peripheral side of the spiral structure is separated from the distal end (bottom) 22 in the sheath tube 21 as shown in FIGS. Is directly welded and electrically connected to the outer peripheral surface in the vicinity of the tip 41 of the terminal shaft 40 (a portion closer to the tip) without passing through a resistance coil for current control. Of the terminal shaft 40, the tip portion including the tip portion (the thick line portion in FIG. 2 and the broken line portion in FIG. 5) to which the other end 35 side of the resistance heating element 30 is welded is as described above. A small-diameter portion 45 that is thinner (diameter 1 mm) than the rear portion is formed. In the sheath tube 21 forming the sheath heater 20, although not shown in some drawings, as shown in FIGS. 1, 4, and 7, a heat-resistant insulating powder (MgO) 60 is filled at a predetermined packing density.

  Thus, the insulating powder 60 is filled between the inner surface including the inner peripheral surface 27 of the sheath tube 21 and the outer surface of the terminal shaft 40 and between the winding plates forming the resistance heating element 30. A cylindrical sealing material 65 made of an insulating rubber tube is disposed between the inner peripheral surface of the rear end portion 23 of the sheath tube 21 and the outer peripheral surface of the terminal shaft 40 (medium diameter portion). The outer circumference of the rear end portion 23 of the sheath tube 21 is crimped to a reduced diameter in this example (not shown), and the terminal shaft 40 with the resistance heating element 30 is fixed at the rear end portion 23. The inner insulating powder 60 is sealed. Then, the sheath heater 20 having such a configuration is press-fitted coaxially into the main body 10 through the portion near the rear end (large diameter portion 26) of the sheath tube 21 and fixed, and thereafter, as described above. In addition, the glow plug 1 is configured by disposing a sealing material 51 and an insulating ring 53 at the rear end portion of the coaxial 40 and caulking and fixing a current-carrying terminal 55 to the rear end portion 42 of the shaft protruding rearward therefrom. ing. The glow plug 1 having such a configuration is a resistor that forms a spiral structure in the sheath tube 21 by energizing between the rear end portion of the terminal shaft 40 (energization terminal 55) and the main body 10 (ground electrode). The heating element 30 is caused to generate heat so that the tip 22 portion of the tube 21 (sheath heater 20) is heated.

  In the glow plug 1 of the present embodiment, the sheath heater 20 that constitutes the glow plug 1 is configured as described above, but its manufacture and assembly are performed as follows. That is, as shown in FIG. 5, the band plate 31 is a resistive plate that forms a spiral structure on the outer peripheral surface in the vicinity of the tip 41 (portion near the tip) which is the small diameter portion 45 of the terminal shaft 40. The end part (end part side part) 35 used as the innermost circumference side of the body 30 is assigned (overlapping), for example, the part shown with the broken line is welded (FIG. 5-A). Then, as shown in FIG. 5B, the band plate 31 that forms the resistance heating element 30 around the terminal shaft 40 is wound around to form a spiral structure. Thus, the terminal shaft 40 with the resistance heating element 30 forming the spiral structure as shown in FIG. 6 is formed. Note that such a spiral structure may be separately formed before the end portion 35 is welded to the terminal shaft 40. In other words, after forming the spiral structure, the innermost end 35 may be welded to the outer peripheral surface in the vicinity of the tip 41 of the terminal shaft 40 (site closer to the tip). However, it is only necessary to be electrically connected. Therefore, it may be fixed by press-fitting, caulking or the like without depending on welding.

  Next, as shown in FIG. 7-A, the terminal shaft 40 with the resistance heating element 30 obtained in this way is pre-molded into a sheath tube 21 having a closed end (cylindrical cylindrical shape). Insert inside. Then, as shown in FIG. 7-B, the terminal shaft 40 is concentric and the tip 41 of the coaxial 40 is positioned so as to be separated from the tip 22 in the tube 21 by a predetermined amount. In this state, one end 33 on the outermost peripheral side of the resistance heating element 30 is in contact with the inner peripheral surface 27 of the sheath tube 21 (see FIGS. 2 and 3). The outer surface of the one end 33 that is a portion and the inner peripheral surface 27 of the portion near the tip of the sheath tube 21 are laser-welded from the outside. As is clear from this, the spiral structure is formed in a spiral spring structure so that the end 33 side of the resistance heating element 30 is pressed against the inner surface of the sheath tube 21 by its own spring property before welding. It is good to leave. That is, it is preferable that the outer diameter of the outermost peripheral side of the resistance heating element 30 be larger than the inner diameter of the portion closer to the distal end of the sheath tube 21 in a free state before being inserted into the sheath tube 21.

  Next, a predetermined amount of the insulating powder 60 is poured into the sheath tube 21 from the upper opening which is the rear end 23 with the tip 22 of the sheath tube 21 down, and the sheath tube 21 is filled (see FIG. 7C). At this time, since the resistance heating element 30 forms a spiral structure when viewed from the rear end side (see FIG. 2) in the sheath tube 21 as described above, the insulating powder 60 is not wound. While entering between the plates, it also enters the tip 22 in the sheath tube 21 beyond that (see FIG. 4). Therefore, thereafter, the rear end side of the insulating powder 60 is compressed with, for example, a cylindrical presser 70 from the rear end 23 side toward the front end 22 side so that the filled insulating powder 60 has a desired packing density. (See FIG. 7-C). By doing so, the insulating powder 60 is maintained at a desired packing density inside. The presser 70 used in this compression step has an inner diameter larger than the outer diameter of the terminal shaft 40 (in this example, the outer diameter of the medium diameter portion 46), and the outer diameter is the inner diameter of the portion near the rear end of the sheath tube 21. A smaller cylinder may be used. Thus, after the filling, the sealing heater 65 that seals the insulating powder 60 while maintaining insulation from the terminal shaft 40 is disposed by press-fitting or the like at the rear end portion 23 of the sheath tube 21, so that the sheath heater 20. (Assembly) is manufactured and assembled. When the large-diameter portion 47 of the terminal shaft 40 interferes with the compression of the insulating powder 60, the rear end portion including the large-diameter portion 47 has its tip at the rear end of the medium-diameter portion 46. What is necessary is just to butt-weld to a rear end.

  As described above, in the sheath heater 20 according to the present embodiment, the resistance heating element 30 has the spiral structure as described above. Therefore, in the manufacture and assembly, the insulating powder 60 filled in the sheath tube 21 is desired. In order to maintain the packing density, it is possible to compress it in the axial direction with a predetermined compressive force from the rear end side. That is, according to the manufacturing method of the present embodiment, since the resistance heating element 30 having the vine coil structure extending forward is not used, the sheath tube 21 is contracted in the longitudinal direction after the insulating powder 60 is filled. A process of caulking in a diameter can be omitted. Therefore, since the manufacturing process can be simplified because such a process is not required, the manufacturing cost of the sheath heater 20 can be reduced.

  Further, in the manufacturing process of the sheath heater 20 according to the present embodiment, the resistance heating element 30 is formed in the sheath tube 21 formed into a bottomed cylindrical shape in order to weld the resistance heating element 30 to the tip 22 in the sheath tube 21. After positioning and positioning, it is only necessary to perform laser welding. This is because, as in the prior art, a sheath tube work product having a reduced diameter cylindrical portion is formed at the tip, and the distal end portion of the resistance heating element (coil) is inserted into the reduced diameter cylindrical portion, It means that a welding process for melting together with the reduced diameter cylindrical portion is not required. Therefore, it is possible to eliminate the occurrence of variations in the thickness of the sheath tube work-in-process at the tip of the diameter-reduced cylindrical portion and the thickness of the sheath tube tip (bottom) due to the variation in the amount of molten (metal) during welding. be able to. That is, the sheath tube 21 used in the manufacture of the sheath heater 20 according to the present embodiment can be manufactured by deep drawing from a plate material or extrusion from a shaft material with a closed end, and the tube 21 by such a manufacturing method. Can be formed with high accuracy, including the thickness accuracy of the tip (bottom portion) 22. In addition, since welding with the resistance heating element 30 can also be performed by laser welding, there is no variation in the thickness of the tip of the sheath heater 20. Therefore, the sheath heater 20 with less variation in heat generation performance can be obtained.

  Furthermore, in this embodiment, the resistance heating element 30 is concentrated in the vicinity of the tip 22 without extending in the sheath tube 21. For this reason, as compared with the conventional coil structure that extends earlier and later, the distal end of the sheath tube 21 constituting the sheath heater 20 or a portion closer to the distal end can be heated intensively and efficiently. As a result, power consumption can be reduced.

  Moreover, in the said form, the site | part containing the front-end | tip part to which the other end 35 side of the resistance heating element 30 is welded among the shafts 40 for terminals has comprised the small diameter part 45 thinner than the site | part behind it. For this reason, the effect of preventing heat conduction to the rear of the terminal shaft 40 is high, and therefore the heat generation efficiency of the sheath heater 20 can be prevented from being reduced.

  Now, another example of the glow plug 1 of the present invention will be described with reference to FIG. However, since the thing of this example differs only in the structure of the resistance heating element 30 provided in the sheath tube 21 which makes the sheath heater 20, only the difference is demonstrated. In other words, the resistance heating element 30 forming the spiral structure in the present invention has a metal plate such as a band plate spaced between the winding plates so as to form a spiral when viewed from the rear end side in the sheath tube 21. And a spiral structure formed in a spiral shape may be formed. In the above embodiment, as a typical example, a spiral spring structure in which the strip 31 is spirally wound on a plane is used. That is, the one end 33 side and the other end 35 side of the resistance heating element 30 are in the same position or substantially the same position before and after the virtual axis, that is, one plane perpendicular to the virtual axis around the virtual axis. An example of a spiral shape wound in a plane along the shape of is shown.

  On the other hand, in this example, as shown in FIG. 8, the resistance heating element 30 that forms the spiral structure is positioned more backward in the winding plate part away from the one end 33 side toward the other end 35 side. It is assumed to have a spiral shape. In such a configuration, the other end 35 side that is the innermost peripheral side of the resistance heating element 30 can be moved away from the distal end 22 of the sheath tube 21 that becomes high temperature. For this reason, even when the terminal shaft 40 is joined to the other end 35 side by welding, fusing prevention (separation) due to remelting of the welded portion is achieved. Such a spiral structure is formed as a spiral spring structure in which the above-described strip 31 is spirally wound in a plane, and after welding one end 33 thereof to the inner peripheral surface of the sheath tube 21, Even if the other end 35 is moved backward by the terminal shaft 40 fixed by welding or the like, it can be configured.

  The resistance heating element 30 in each of the above examples illustrates a spiral structure in which a strip 31 having a constant width and a certain thickness is wound in a spiral shape, but the resistance heating element 30 of the present invention is like this. It is not limited to anything. For example, as shown in FIG. 9 in the unfolded state before the spiral is formed, the intermediate portion 38 that forms the wound plate of such a resistance heating element 30 is formed narrower than the other end 35 side. The resistance value of the part located outside the spiral structure can be made larger than the end 35 side. In this way, the intermediate portion 38 located relatively outside can be preferentially heated compared to the portion on the other end 35 side arranged inside, and the heat generation efficiency of the spiral structure can be easily improved. can do. Further, in the resistance heating element 30, a portion that is a welded portion with the inner surface of the sheath tube 21 on the one end 33 side is formed wider than the intermediate portion 38 that forms a winding plate, It is preferable that this wide end portion 33 side is overlapped and welded to the inner surface of the sheath tube 21. This is because a welded portion energizing area having a large conduction cross-sectional area can be obtained from the intermediate portion 38 forming the winding plate as indicated by a broken line in the drawing. That is, the one end 33 of the resistance heating element 30 serving as the outermost peripheral portion is a portion that should generate heat at the highest temperature. By forming in this way, the one end 33 and the inner surface of the sheath tube 21 This is because it is possible to prevent breakage and fusing (welding separation) due to excessive resistance value (conducting resistance) and high temperature at the welded part. In addition, since the same thing can be said also when welding the electrical connection of the other end 35 part with respect to the axis | shaft 40 for terminals by welding, the other end 35 in the strip 31 can also ensure a large welding part energization area. As shown in FIG. 4, it is preferable that the width of the band plate 31 is wider than that of the intermediate portion 38.

  In addition, although the resistance heating element 30 of each said example has illustrated what was made into the spiral structure formed by winding the strip 31 which has a fixed width | variety and fixed thickness except for both ends, it is constant. In the case of using a thick metal plate, the width of the winding plate portion located on the one end side (the outermost peripheral side of the spiral structure) is positioned on the inner peripheral side (terminal shaft 40 side). If it is formed so as to be substantially smaller than the width, the heat generation efficiency as a sheath heater is enhanced. If formed in this way, the resistance value per unit length of the winding plate portion located on the one end side becomes larger than the resistance value per unit length of the winding plate portion located on the inner peripheral side thereof. For this reason, the outer peripheral side of the resistance heating element, which is located in a portion close to the inner peripheral surface of the distal end portion of the sheath tube, can be quickly heated to a high temperature.

  Incidentally, in order to increase the resistance value of the wound plate portion located on the one end side (outermost peripheral side) in this way, in the resistance heating element wound with a metal strip of a certain thickness, the outermost periphery in the spiral structure As shown in the developed view of FIG. 10, the width of the portion located on the side is substantially narrower than the width of the portion located on the innermost peripheral side (the winding plate portion located on the terminal shaft side). In addition, a plurality of holes (for example, square holes) 39 may be punched and formed over a predetermined range of the strip 31 from a portion closer to the innermost peripheral side to the innermost peripheral side. This is because a band plate can be used as a material for the resistance heating element. In addition, since it functions as a rib between the holes 39, it can play the role which stabilizes a spiral structure. Moreover, as shown in the development view of FIG. 11, a strip-shaped metal plate whose width is gradually narrowed toward a portion closer to one end 33 on the outermost periphery may be used as a material, and these may be wound to form a spiral structure. In this case as well, the portion that forms the one end 33 of the resistance heating element 30 and is the welded portion with the inner surface of the sheath tube 21 is formed so that the width of the band plate is wider than the intermediate portion that forms the wound plate, It is preferable that the welded part has a welded part energization area having a large conduction cross-sectional area as indicated by a broken line in the drawing.

  The present invention is not limited to the contents described above, and can be embodied with appropriate modifications. For example, the electrical connection between the other end of the resistance heating element forming the spiral structure and the terminal shaft may be performed by press fitting or caulking as described above. In addition, although it is preferable that the part of the terminal shaft to be electrically connected to the other end side of the resistance heating element is a part close to the tip, it may be separated from the tip. In addition, the position where one end (the outermost peripheral end) side of the resistance heating element is welded to the sheath tube is the inner peripheral surface (tube wall surface) near the distal end of the sheath tube in each of the above embodiments. Thus, it may be the tip (bottom) of the sheath tube, or it may straddle both. This is the reason why, in the present invention, the position where one end side of the resistance heating element is welded is the tip in the sheath tube or a portion near the tip.

DESCRIPTION OF SYMBOLS 1 Glow plug 20 Sheath heater 21 Sheath tube 22 Sheath tube tip 23 Sheath tube rear end 30 Resistance heating element 33 One end 35 of the resistance heating element located on the outermost circumference side of the spiral structure The innermost circumference side of the spiral structure The other end 40 of the resistance heating element located at the terminal 40 The terminal shaft 41 The terminal shaft tip 60

Claims (9)

A sheath tube with a closed tip;
A terminal shaft for energization inserted in the sheath tube;
It is arranged in the sheath tube, and one end side of itself is welded to the distal end or a portion near the distal end in the sheath tube, while the other end side is electrically connected to the terminal shaft and generates heat when energized. A resistance heating element;
Insulating powder filled in the sheath tube;
In a glow plug having a sheath heater with
The resistance heating element is a spiral structure in which a metal plate is formed in a spiral shape while maintaining a space between the winding plates so as to form a spiral shape when viewed from the rear end side in the sheath tube. A glow plug characterized in that one end side of the resistance heating element located on the outermost peripheral side of the spiral structure is welded to a distal end or a portion closer to the distal end in the sheath tube.   The other end side of the resistance heating element located on the innermost peripheral side of the spiral structure is electrically connected to a tip end or a portion closer to the tip end of the terminal shaft. Glow plug.   3. The glow according to claim 1, wherein the spiral structure has a spiral shape that is wound in a plane around a virtual axis along a plane perpendicular to the virtual axis. plug.   3. The spiral structure has a spiral shape in which the spiral plate portion is located at the rear side toward the other end side away from the one end side of the resistance heating element. Glow plug as described in.   The welding portion energization area in the welded portion between the one end side of the resistance heating element and the inside of the sheath tube is maintained larger than the conduction cross-sectional area of the winding plate portion located on the inner peripheral side than the welded portion. The glow plug according to any one of claims 1 to 4, characterized in that:   The resistance heating element is formed such that a resistance value per unit length of the wound plate portion located on the one end side is larger than a resistance value per unit length of the wound plate portion located on the inner peripheral side. The glow plug according to any one of claims 1 to 5, wherein the glow plug is provided.   The terminal shaft is formed such that a cross-sectional area of a tip side portion including a portion where the other end side of the resistance heating element is electrically connected is smaller than a cross-sectional area of a rear portion thereof. The glow plug according to any one of claims 1 to 6, wherein:   The resistance heating element is positioned in the sheath tube and welded to the distal end of the sheath tube or a portion close to the distal end with the terminal shaft joined to the other end. The glow plug according to any one of claims 1 to 7, wherein the one end side of the body is formed as a spiral spring pressed against the inner surface of the sheath tube by a spring property.   A step of obtaining a resistance heating element with a terminal shaft by electrically connecting a tip end or a portion near the tip of the terminal shaft to the other end side of the resistance heating element; The resistance heating element is disposed in the sheath tube, and the one end side of the resistance heating element is welded to the distal end or a portion closer to the distal end in the sheath tube, and then the rear end opening in the sheath tube. And after the insulating powder is filled, the insulating powder is compressed from the opening at the rear end of the sheath tube toward the distal end side to keep the insulating powder at a predetermined filling density. The method for manufacturing a glow plug according to claim 1, wherein:

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