EP2208930A2 - Herstellungsverfahren einer Heizröhre einer Glühkerze sowie Glühkerze - Google Patents

Herstellungsverfahren einer Heizröhre einer Glühkerze sowie Glühkerze Download PDF

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Publication number
EP2208930A2
EP2208930A2 EP10250011A EP10250011A EP2208930A2 EP 2208930 A2 EP2208930 A2 EP 2208930A2 EP 10250011 A EP10250011 A EP 10250011A EP 10250011 A EP10250011 A EP 10250011A EP 2208930 A2 EP2208930 A2 EP 2208930A2
Authority
EP
European Patent Office
Prior art keywords
heater tube
forming
blank material
hole
heater
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP10250011A
Other languages
English (en)
French (fr)
Other versions
EP2208930A3 (de
Inventor
Masanori Hiraishi
Hiroshi Kato
Minoru Ando
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Niterra Co Ltd
Original Assignee
NGK Spark Plug Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by NGK Spark Plug Co Ltd filed Critical NGK Spark Plug Co Ltd
Publication of EP2208930A2 publication Critical patent/EP2208930A2/de
Publication of EP2208930A3 publication Critical patent/EP2208930A3/de
Withdrawn legal-status Critical Current

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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23Q—IGNITION; EXTINGUISHING-DEVICES
    • F23Q7/00—Incandescent ignition; Igniters using electrically-produced heat, e.g. lighters for cigarettes; Electrically-heated glowing plugs
    • F23Q7/001—Glowing plugs for internal-combustion engines
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23Q—IGNITION; EXTINGUISHING-DEVICES
    • F23Q7/00—Incandescent ignition; Igniters using electrically-produced heat, e.g. lighters for cigarettes; Electrically-heated glowing plugs
    • F23Q7/001—Glowing plugs for internal-combustion engines
    • F23Q2007/004—Manufacturing or assembling methods

Definitions

  • the present invention relates to a glow plug used for, for example, pre-heating for facilitating startup of a diesel engine, and more particularly to a method of manufacturing a heater tube (hereinafter may be simply referred to as a "tube"), which is a constituent part of such a glow plug, and to a glow plug.
  • a heater tube hereinafter may be simply referred to as a "tube"
  • FIG. 5 shows a heater element 11, which partially constitutes a glow plug 10, and also schematically shows the structure of the element 11 by a partially sectioned enlarged view thereof.
  • This heater element 11 is composed of a heater tube 31 having a cylindrical straight tube portion 21 and a closed hemispherical portion 30 provided at the front end of the straight tube portion 21; a heat generation coil (hereinafter may be simply referred to as a "coil”) 41 which is formed of metal having a high melting point and is disposed within the heater tube 31; and an unillustrated insulating filling material (e.g., MgO powder).
  • the heat generation coil 41 is welded to the hemispherical portion 30 at the front end (lower end in FIG. 5 ), and extends rearward (toward the upper end in FIG. 5 ).
  • a heater tube which partially constitutes the heater element 11 and in which the heat generation coil 41 is accommodated is manufactured from an iron-based metal tube (in general, a circular tube formed of low carbon steel; a blank tube) through a plurality of press steps (cold forging steps).
  • This production method through press working is a cold forging process, which is basically the same as that employed in a production method for forming a tubular glow plug body (housing) (see, for example, Patent Document 1).
  • a heater tube before the heat generation coil 41 is accommodated therein is formed as follows. As shown in the left-end drawing (1) of FIG.
  • a starting blank material (a straight circular tube having a constant transverse cross section; hereinafter may be simply referred to as a "blank material)) 20 having a predetermined length.
  • a front end (lower end in FIG. 6 ) of the blank material is drawn step by step in a plurality of press steps.
  • a heater tube post-forming product 20k shown in the right-end drawing (4) of FIG. 6 is obtained.
  • the heater tube post-forming product 20k has a tapered-off portion 33 at the front end thereof.
  • a coil 41 is disposed within the heater tube post-forming product 20k having the shape shown the left-end drawing (4) of FIG.
  • a typical method of manufacturing the above-described heater tube post-forming product 20k from the blank material 20 is to draw the front end of the blank material 20 step by step through a plurality of (e.g., 10) press working steps (drawing steps) as shown in FIG. 6 .
  • some intermediate formed products are omitted.
  • a die 101 as shown in FIG. 8 is used.
  • the left-hand drawing of FIG. 8 is a cross sectional view showing a die used in an intermediate press step (e.g., the fourth press step) and press working performed by use of the die.
  • each of such dies has a forming hole 121 in which a blank material (in-process product) can be loaded (inserted) and which has, on the front end side thereof (the lower end side in FIG 8 ), a forming surface (inner surface for drawing) 131 corresponding to the drawing amount (drawing step) of the front end of the heater tube.
  • a blank material 20 is loaded into the forming hole 121 of the die 101 from the rear side (the upper side in FIG. 8 ), and is pressed.
  • a mandrel (pin) 201 whose front end surface is formed in accordance with the drawing amount at the front end of the blank material is typically inserted into the interior (hole) of the blank material from the rear side.
  • a cylindrical tubular sleeve punch 301 which has a transverse cross section approximately the same as that of the blank material 20 and is fitted onto the mandrel 201, is coaxially inserted into the forming hole 121, so that the front end of the sleeve punch 301 moves the rear end of the blank material 20 frontward over a predetermined stroke to thereby press (apply pressure to) the blank material 20 frontward.
  • the front end of the blank material 20 undergoes a predetermined draw-forming in each press step. In this manner, the front end of the blank material 20 is drawn step by step through use of the dies fabricated for the respective press steps.
  • the blank material 20 is formed into the heater tube post-forming product 20k by use of a die 101 fabricated such that the heater tube post-forming product 20k has a desired front end shape.
  • the diameter of the straight hole portion of the forming hole 121 of each die 101 is set such that the blank material 20 to be pressed can be inserted into the straight hole portion in a substantially clearance-free state
  • the diameter of the mandrel 201 is set such that the mandrel 201 can be inserted into the blank material 20 in a substantially clearance-free state.
  • the front end of the forming hole 121 of the die 101 has a hemispherical forming surface 131 corresponding to the outer surface of the front end of the heater tube post-forming product 20k shown in the right-end drawing of FIG. 6 . Further, at the center of the front end of the forming hole 121, there is provided a cylindrical hole 141 whose diameter is smaller than the outer diameter of the straight tube portion 21 of the heater tube 31.
  • the cylindrical hole 141 extends frontward from the front end of the forming hole 121, and is used to form the projecting mouth portion 35 projecting frontward from the front end of the tapered-off portion 33 of the heater tube post-forming product 20k shown in the right-end drawing of FIG 6 . That is, as a result of forming the front end of the forming hole 121 into the above-described shape, the hemispherical, tapered-off portion 33, which is not closed, is formed at the front end of the finally formed heater tube post-forming product 20k as shown in the right-end drawing of FIG. 6 . Further, the projecting mouth portion 35, which projects frontward by a predetermined projection length L1, is formed at the front end of the tapered-off portion 33.
  • the distal end 42 of the coil 41 is inserted into the projecting mouth portion 35 at the front end of the tapered-off portion 33.
  • the distal end 42 of the coil 41 is then positioned and welded to the projecting mouth portion 35.
  • the front end of the heater tube post-forming product 20k has the above-mentioned projecting mouth portion 35.
  • the projecting mouth portion 35 is molten and solidified, whereby the opening thereof is closed, and the tapered-off portion 33 assumes a hemispherical shape.
  • Patent Document 1 Japanese Patent Publication ( kokoku ) No. H2-6412
  • the blank material (starting blank material) 20 used for the above-described press steps is one obtained through cutting a cylindrical tube to a predetermined length.
  • a cutting operation in some cases, only an upper-side dimensional tolerance is specified, with a lower-side dimensional tolerance fixed to 0.
  • the length of the blank material 20 varies within a range of 0.5 mm.
  • the blank material is compressed in the axial direction by an amount corresponding to the predetermined stroke set for each step.
  • the front end of the blank material 20 is pushed into the cylindrical hole 141 provided at the front end of the forming hole 121 of the die, whereby the projecting mouth portion 35 is finally formed at the front end of the blank material. Accordingly, in the case where the length of the blank material is longer than a reference dimension, the front end of the blank material is pushed into the cylindrical hole 141 at the front end of the forming hole 121 of the die 101 by a greater amount corresponding to the difference between the length of the blank material and the reference dimension.
  • the length L2 of the heater tube post-forming product 20k is maintained at a predetermined dimension (set dimension).
  • the projection length L1 of the projecting mouth portion 35 at the front end of the tapered-off portion 33 becomes longer than a reference dimension; and the greater the dimensional variation, the greater the projection length L1. That is, the heater tube post-forming product 20k formed through the final press step has a variation in the projection length L1 of the projecting mouth portion 35, which variation corresponds to a variation in the length of the blank material.
  • the blank material 20 is longer than the reference dimension and the projection length L1 of the projecting mouth portion 35 at the formed tapered-off portion 33 is excessively large, a problem of improper welding between the projecting mouth portion 35 and the distal end 42 of the coil 41 occurs.
  • the projection length L1 of the projecting mouth portion 35 at the tapered-off portion 33 is excessively large, the base material (a projecting wall portion of the projecting mouth portion 35) fails to be sufficiently melted, whereby the amount of molten metal (melt) becomes insufficient (excessively small), and welding failure occurs.
  • the hemispherical portion 30 of the heater element 11 has a wall thickness greater than a desired thickness, or fails to assume a desired hemispherical shape and accuracy. This leads to deterioration of the temperature performance of a glow plug finished product.
  • a first object of the present invention is to maintain at a predetermined amount the projection length of a projecting mouth portion projecting frontward from a tapered-off portion at the front end of a heater tube, to thereby prevent occurrence of welding failure, which would otherwise occur when a front end of a heat generation coil disposed within the heater tube is welded to the projecting mouth portion.
  • a second object of the present invention is to provide a heater tube which prevents generation of a variation in the temperature performance among glow plug finished products.
  • the present invention which achieves the above-described objects is as follows.
  • the invention described in claim 1 is a method of manufacturing a heater tube for a glow plug which includes a straight tube portion, a tapered-off portion provided at a front end of the straight tube portion, and a projecting mouth portion projecting frontward from a front end of the tapered-off portion, the method comprising a plurality of press steps in each of which a tubular blank material is loaded into a forming hole of a die, and is pressed frontward via a rear end of the blank material, the method being characterized in that at least a die used in the final press step is formed such that a straight hole portion of a forming hole of the die has a diameter greater than an outer diameter of a straight tube portion of a heater tube finished product; the die formed such that the straight hole portion of the forming hole of the die has a diameter greater than the outer diameter of the straight tube portion of the heater tube finished product is provided with a support member which is disposed on a front end side of
  • the invention described in claim 2 is a method of manufacturing a heater tube for a glow plug which includes a straight tube portion, a tapered-off portion provided at a front end of the straight tube portion, and a projecting mouth portion projecting frontward from a front end of the tapered-off portion, the method comprising a plurality of press steps in each of which a tubular blank material is loaded into a forming hole of a die, and is pressed frontward via a rear end of the blank material, the method being characterized in that each of dies used in a plurality of press steps including the final press step is formed such that a straight hole portion of a forming hole of the die has a diameter greater than an outer diameter of a straight tube portion of a heater tube finished product; each die formed such that the straight hole portion of the forming hole of the die has a diameter greater than the outer diameter of the straight tube portion of the heater tube finished product is provided with a support member which is disposed on a front end side of the forming hole so as to support a front
  • the invention described in claim 3, which depends from the invention described in claim 2, is characterized in that the plurality of press steps including the final press step are successive press steps which are performed continuously.
  • a mandrel pin
  • a mandrel is desirably inserted into the tubular blank material when the blank material is loaded into the forming hole of the die, and is pressed frontward via the rear end of the blank material in the axial direction.
  • a mandrel is desirably inserted into the straight tube portion of the heater tube post-forming product when the heater tube post-forming product is ironed.
  • a heater tube in a process before being formed into the heater tube finished product will also be referred to as a "heater tube in-process product.”
  • the "heater tube post-forming product formed from the blank material through press forming in the final press step” means a heater tube in-process product which has undergone the plurality of press steps and is immediately before undergoing ironing work in the ironing step.
  • the forming holes of the dies which are used in the respective steps in order to obtain the heater tube post-forming product are formed such that the above-described heater tube; i.e., that having a tapered-off portion at the front end of a straight tube portion thereof, and a projecting mouth portion projecting frontward from the front end of the tapered-off portion, is finally obtained as a heater tube post-forming product. Therefore, the forming hole is made slightly different among the dies used in the plurality of press steps so that the straight tube portion is pressed in the axial direction so as to plastically deform the front end of the straight tube portion step by step, and the heater tube post-forming product is finally obtained.
  • this forming hole has a straight hole portion, and a forming surface which is formed at the front end of the straight hole portion and adapted to form the tapered-off portion and the projecting mouth portion in each forming step.
  • the forming hole is identical with the forming holes of dies used in the conventional manufacturing method. That is, the straight hole portions of the dies used in the present invention are identical with the forming holes of dies used in the conventional manufacturing method, except for the diameter of the straight hole portions.
  • the diameter of the straight hole portion of the forming hole of each die is made greater than the outer diameter of the straight tube portion of the heater tube finished product by an amount determined such that a tubular starting blank material obtained through cutting is allowed to expand radially outward so as to absorb an excessive volume of the blank material corresponding to a cutting tolerance (error) set for the entire length of the blank material.
  • means for removing an unnecessary portion in the present invention include end machining by means of a cutting tool (cutting), cutting-off by means of a cutting-off tool, and grinding by means of a grinding stone.
  • the invention described in Claim 4 is a glow plug which includes a heater element disposed such that a front end of the heater element projects from a front end of the glow plug, wherein the heater element is configured such that a heat generation coil is disposed in a heater tube manufactured by a manufacturing method according to any one of claims 1 to 3, a front end of the heat generation coil is inserted into the projecting mouth portion projecting frontward from the front end of the tapered-off portion of the heater tube, and the front end of the heat generation coil is welded to the projecting mouth portion.
  • the diameter of the straight hole portion of the forming hole of at least the die used in the final press step is made greater than the outer diameter of the straight tube portion of the heater tube finished product.
  • a support member is disposed so as to support the front end of the blank material.
  • the straight tube portion expands radially outward and has an outer diameter greater than the outer diameter of the straight tube portion of the heater tube finished product. Accordingly, in the present invention, even when a blank material whose overall length is greater than the reference dimension is contained in blank materials to be used, the projection length of the projecting mouth portion is prevented from becoming excessively large, whereby there can be obtained heater tube in-process products in which the projection length of the projecting mouth portion is maintained at the predetermined projection length.
  • the outer diameter of the straight tube portion is adjusted (corrected) to a predetermined dimension.
  • the overall length of the ironed heater tube is greater than the overall length as measured before the heater tube is ironed.
  • a rear-end unnecessary portion of the straight tube portion of the heater tube is removed, whereby the overall length is adjusted to the predetermined dimension.
  • the straight tube portion becomes thinner and longer as a result of ironing, the overall length of the heater tube in-process product in this stage is longer than the reference dimension.
  • the shapes and dimensions of the tapered-off portion and the projecting mouth portion projecting from the front end thereof are substantially free from the influence of the ironing work, and the accuracy attained before the ironing work is maintained as is. Accordingly, after the ironing work, while a front end portion of the heater tube in-process product is used as a reference, a rear end portion (unnecessary portion) of the straight tube portion, which is longer than the reference dimension, is cut (removed) by means of, for example, cutting, whereby heater tubes having a desired dimensional accuracy can be obtained.
  • the tip end of a coil is inserted into the projecting mouth portion at the front end of the tapered-off portion of a heater tube manufactured as described above, positioned, and welded to the projecting mouth portion, the amount of molten metal produced during the welding is prevented from becoming excessively small or excessively large, whereby occurrence of a failure associated with the welding can be prevented. Accordingly, there can be effectively prevented generation of a variation in temperature performance among glow plugs (finished products) each including a heater element composed of a heater tube manufactured by the method of the present invention and a heat generation coil welded thereto. Further, according to the present manufacturing method, since an unnecessary portion of the straight tube portion is removed, there can be attained an effect that the maximum allowable dimension set for the length of a straight tube (starting blank material) can be increased.
  • a glow plug including a heater element composed of a heater tube manufactured by the above-described method and a heat generation coil welded thereto has a consistent temperature performance.
  • a starting blank material (may be simply referred to as the "blank material"), and a tube formed through press steps are assumed to be identical with those shown at the left-hand and right-hand ends of FIG. 6 .
  • a heater tube post-forming product (a formed heater tube intermediate to be subjected to an ironing step) 20k is formed from the starting blank material through 11 press steps.
  • the starting blank material is assumed to have a length equal to a maximum allowable dimension.
  • dies similar to the conventional dies are used so as to draw the front end portion of the blank material 20 step by step in the first press step to the third press step; and a die 101 shown in FIGS. 1 and 2 and having a forming hole 121 peculiar to the present invention is used in the fourth press step to the eleventh press step (final press step).
  • a heater tube in-process product i.e., a blank material in the forming process
  • the dies 101 used in these steps have the same basic structure as the conventional dies 101 except for the following points.
  • a support member 151 is disposed on the front end side of the forming hole 121 of each die 101 so as to support, in the corresponding press step, the front end of the blank material (the blank material to be pressed in press steps other than the final press step) 20, to thereby maintain the projection length L1 of the projecting mouth portion 35 of the blank material 20 at a predetermined projection length.
  • the dies 101 slightly differ from each other in terms of the shape of the front end of the forming hole 121 in accordance with the drawing amount of the front end of the blank material. Therefore, here, the dies 101 used in the fourth press step shown in FIG.
  • each of these dies 101 includes a mandrel 201 which is inserted into the blank material 20, and a sleeve punch 301 which axially presses the blank material 20 via its rear end.
  • This die 101 has the forming hole 121 which further draws, by an adequate degree, the front end of the blank material (see FIG 6 (3)) 20 having undergone press forming in the third press step.
  • This forming hole 121 has a straight hole portion 123, and a forming surface having a tapered-off shape (hereinafter may be referred to as the "tapered-off forming surface) 131 which is provided at the front end of the straight hole portion 123 and has a shape corresponding to the degree of drawing in the fourth press step.
  • the diameter (bore diameter) D21 of the straight hole portion 123 is determined such that the blank material 20 having undergone the press working in the third press step can be loaded into the straight hole portion 123, and the diameter D21 is greater than the outer diameter D1 of a straight tube portion 21 of a heater tube finished product (see the right end of FIG. 4 ) 20fby, for example, 0.15 mm. Accordingly, this forming hole 121 is formed such that, when the blank material 20 is pressed in the axial direction, the outer diameter of the straight tube portion 21 of the blank material 20 can become greater than the outer diameter D1 of the straight tube portion 21 of the heater tube finished product 20f.
  • a cylindrical hole 141 whose diameter is smaller than the diameter D21 is formed such that it further extends frontward from the front end of the forming hole 121 so as to form, through press forming, the cylindrical projecting mouth portion 35, which projects frontward from the front end of the tapered-off portion 33 of the blank material 20.
  • the rod-shaped (circular columnar) support member 151 is inserted into the cylindrical hole 141 to be movable in the vertical direction. Notably, this support member 151 is inserted into the cylindrical hole 141 in a substantially clearance-free state.
  • the support member 151 is positioned in relation to the die 101 such that, when the blank material 20 is pressed in the present step, the front end of the support member 151 is maintained at a predetermined position so as to maintain the projection length L1 of the projecting mouth portion 35 at a predetermined length (stop the projecting mouth portion 35 at a predetermined position).
  • the dies and support members used in the fifth press step and subsequent steps are also configured in the same manner as the die 101 and the support member 151 shown in FIG. 1 .
  • the tapered-off shape of the front end of the straight hole portion of the forming hole of each die is determined in accordance with the degree of drawing in each step such that the shape and dimension of the tapered-off front end of the straight hole portion become closer to those of the tapered-off portion and the projecting mouth portion of the finished product step by step.
  • FIG. 2 is a pair of views showing the die 101 used in the eleventh press step (final step) and a press step performed by use of the die.
  • the die 101 and the support member 151 used in the eleventh press step are formed such that the tapered-off portion 33 at the front end of the blank material 20 having undergone the press forming in the tenth press step and the projecting mouth portion 35 projecting forward from the front end of the tapered-off portion 33 are formed to finally have a predetermined diameter and a predetermined projection length L1.
  • the diameter (bore diameter) D21 of the straight hole portion 123 of the die used in the eleventh press step is greater than the outer diameter D1 of the straight tube portion 21 of the heater tube finished product 20f.
  • the fourth press step in which the blank material 20 having undergone the press forming in the previous step is press-formed by use of the die 101 shown in FIG. 1 .
  • the mandrel 201 and the sleeve punch 301 of the die 101 shown in FIG. 1 are moved upward, and the blank material 20 is loaded into the forming hole 121 of the die 101 from the rear end side (the upper end side in FIG. 1 ) such that the front end of the blank material 20 is located on the front-end side of the forming hole 121 (see the right-hand drawing of FIG. 1 ).
  • the mandrel 201 is inserted into the blank material 20.
  • this mandrel 201 has a diameter which enables its insertion into the blank material 20 in a substantially clearance-free state, and the front end of the mandrel 201 is rounded in accordance with the drawing amount of the front end of the blank material 20.
  • a cylindrical tubular sleeve punch 301 which has a transverse cross section approximately the same as that of the blank material 20 and is fitted onto the mandrel 201, is coaxially inserted into the forming hole 121, so that a front-end portion of the sleeve punch 301 moves the rear end of the blank material 20 frontward over a predetermined stroke to thereby press (apply pressure to) the blank material 20 frontward.
  • the front end of the blank material 20 is drawn to follow the shape of the tapered-off forming surface 131 at the front end of the forming hole 121, whereby a predetermined drawn shape to be imparted in this step is imparted to the front end of the blank material 20.
  • the overall length of the used blank material 20 is longer than the reference dimension.
  • the rod-shaped support member 151 is disposed in the cylindrical hole 141 of the die 101 as described above, the projection length L1 of the projecting mouth portion 35 at the front end of the blank material 20 is maintained at a predetermined length set for this step.
  • the straight tube portion 21 of the blank material 20 is allowed to expand in the radial direction in the straight hole portion 123 during the pressing. Therefore, the straight tube portion 21 expands and deforms such that its outer diameter increases by an amount corresponding to the difference between the length of the starting blank material 20 and the reference dimension.
  • the blank material 20 having undergone the press forming in the fourth press step is similarly press-formed in the fifth press step and subsequent steps by use of the dies for the respective press steps.
  • the press forming is performed by use of the die 101 shown in FIG. 2 . That is, in this eleventh press step, the front end of the blank material 20 is drawn to follow the shape of the tapered-off forming surface 131 at the front end of the forming hole 121, whereby the front end of the blank material 20 is formed into a tapered-off portion 33 having a predetermined shape and dimensions.
  • the rod-shaped support member 151 is disposed in the cylindrical hole 141 of the die 101 as described above.
  • the projection length L1 of the projecting mouth portion 35 at the front end of the blank material (heater tube post-forming product) 20k having undergone this final press step is maintained at the predetermined projection length.
  • the straight tube portion 21 of the heater tube post-forming product 20k is allowed to expand in the radial direction within the straight hole portion 123 to thereby have an outer diameter greater than the outer diameter D1 of the heater tube finished product 20f.
  • the straight tube portion 21 of the heater tube post-forming product 20k having undergone the final press step has an outer diameter D3 (see FIG 3 and the left-end drawing of FIG 4 ), which is greater than the outer diameter D1 indicated by lines in FIG 3 having alternate long and two short dashes.
  • a different mandrel 212 is inserted into the straight tube portion 21 of the heater tube post-forming product 20k having undergone the press-forming in the final press step.
  • the heater tube post-forming product 20k with the mandrel 212 inserted thereinto is passed through an ironing hole 403 formed in an ironing die 401, starting from its front end.
  • This ironing hole 403 is a cylindrical hole having a diameter D24 which can reduce the diameter of the straight tube portion 21 of the heater tube post-forming product 20k to the outer diameter D1 of the final heater tube finished product 20f.
  • the diameter D24 is made equal to D1.
  • the straight tube portion 21 of the heater tube (ironed product) 20s having undergone the ironing step has an adjusted (corrected) outer diameter equal to the outer diameter D1 of the final heater tube finished product 20f.
  • FIG. 4 shows the heater tube post-forming product 20k which is to be ironed and which has an expanded straight tube portion 21; and the drawing on the right side thereof (the center drawing) shows the ironed heater tube 20s (a heater tube in-process product).
  • the ironing hole 403 of the ironing die 401 of FIG. 3 has a larger-diameter guide portion 404 formed at the inlet (an upper opening in FIG 3 ) of the ironing hole 403.
  • the heater tube (ironed product) 20s having undergone the above-described ironing step has an increased overall length and an adjusted outer diameter equal to the outer diameter D1 of the final heater tube finished product 20f. That is, as shown at the center of FIG. 4 , as a result of a slight reduction in the outer diameter D1 of the straight tube portion 21, the length L2 of the straight tube portion 21 is increased from the reference dimension by a small amount (crosshatched portion) S. Thus, the straight tube portion 21 has an unnecessary portion 25. Therefore, the unnecessary portion 25, which corresponds to the small amount S and is present at the rear end of the straight tube portion 21, is removed by means of, for example, turning. As a result, as shown on the right end of FIG.
  • a heater tube which has a desired dimensional accuracy not only in the outer diameter and the projection length L1 of the projecting mouth portion 35 at the front end of the tapered-off portion 33, but also in the length L2 of the straight tube portion 21 of the heater tube.
  • the inner surface of a rear end portion of the heater tube is machined simultaneously.
  • removal of the unnecessary portion can be performed in the same step. Since the removal of the unnecessary portion does not require a separate step, cost does not increase.
  • the projecting mouth portion 35 at the front end thereof has desired dimensions.
  • the heat generation coil 41 is welded to such a heater tube 20f. Specifically, as in the case shown in FIG. 7 , the distal end 42 of the heat generation coil 41 is inserted into the projecting mouth portion 35 at the front end of the tapered-off portion 33 of the heater tube 20f, positioned, and welded to the projecting mouth portion 35.
  • a heater element 11 having the same structure as that shown in the enlarged view of FIG. 5 is obtained.
  • the amount of molten metal produced at the time of welding is prevented from becoming excessively small or excessively large, occurrence of a failure associated with the welding; i.e., generation of an excessively large or small amount of molten metal, can be prevented. Accordingly, when a heater element 11 produced by mean of welding the heat generation coil 41 to the heater tube 20f manufactured as described above is used to assemble a glow plug (a finished product) 10 such that a front end portion of the element 11 projects from the front end of the glow plug 10 as shown in FIG. 5 , generation of a variation in temperature performance can be prevented.
  • the starting blank material has a length which is equal to the reference length or less than the maximum allowable dimension, even when the straight tube portion becomes thinner and longer in the ironing step, its length does not exceed the maximum allowable dimension. Therefore, in the case of such a heater tube, no unnecessary portion is produced at the rear end of the straight tube portion, and it is clear that a step of removing the unnecessary portion is not required.
  • all the dies 101 respectively used in the successive fourth to the eleventh (final) press steps are configured such that the diameter of the straight hole portion 123 of the forming hole 121 is larger than the outer diameter D1 of the straight tube portion 21 of the heater tube finished product, and the support member 151 is disposed in each of the dies 101. Therefore, the dimensional accuracy of the projecting mouth portion 35 at the front end of the tapered-off portion 33 can be maintained at a very high level.
  • use of such a die is not required in all the press steps, and the present invention is not limited to the case where such a die is used in all the process steps.
  • the dies excluding the die used in the final press step, may be formed such that the straight hole portions of the dies used in alternate press steps have diameters larger than the outer diameter of the straight tube portion of the heater tube finished product, and the straight hole portions of the remaining dies have smaller diameters, so long as the blank material can be loaded into the forming hole of each die.
  • only the die used in the final press step may be configured such that the diameter of the straight hole portion of the forming hole is larger than the outer diameter of the straight tube portion of the heater tube finished product, and the support member may be disposed in that die only.

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  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Resistance Heating (AREA)
  • Shaping Metal By Deep-Drawing, Or The Like (AREA)
EP10250011.3A 2009-01-15 2010-01-06 Herstellungsverfahren einer Heizröhre einer Glühkerze sowie Glühkerze Withdrawn EP2208930A3 (de)

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KR101253752B1 (ko) * 2011-02-21 2013-04-23 주식회사 봉일금속 글로우 플러그 제조장치 및 이를 이용한 글로우 플러그의 발열튜브 제조방법
WO2012160816A1 (ja) 2011-05-25 2012-11-29 日本特殊陶業株式会社 グロープラグ及びそのグロープラグの製造方法
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KR101237886B1 (ko) * 2011-09-20 2013-02-27 주식회사 유라테크 글로우플러그의 발열체 제조장치 및 이를 이용한 제조방법

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JPS6166018A (ja) * 1984-09-08 1986-04-04 Tsukiboshi Seisakusho:Kk デイゼルエンジン用グロ−プラグのハウジングの製造方法
JPH03267615A (ja) * 1990-03-16 1991-11-28 Watanabe Press Seisakusho:Yugen ディーゼルエンジン用加熱プラグに於ける加熱筒の製造方法
JPH06109248A (ja) * 1992-09-28 1994-04-19 Jidosha Kiki Co Ltd シース型グロープラグの製造方法
JP2853015B2 (ja) * 1995-04-14 1999-02-03 株式会社月星製作所 グロープラグ用ハウジングの製造方法
JP3737879B2 (ja) * 1998-04-15 2006-01-25 日本特殊陶業株式会社 グロープラグ
KR100358509B1 (ko) 1998-08-11 2002-10-30 보슈 브레이키 시스템 가부시키 가이샤 세라믹 히터형 그로우 플러그 및 그 제조방법
DE10134956A1 (de) * 2001-07-23 2003-02-20 Beru Ag Glühkerzen und Verfahren zu deren Herstellung
JP4087303B2 (ja) 2002-07-19 2008-05-21 日本特殊陶業株式会社 グロープラグの製造方法およびグロープラグの製造装置

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JP2010164242A (ja) 2010-07-29
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KR20100084129A (ko) 2010-07-23
KR101288224B1 (ko) 2013-07-18

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