JP2014137170A - Method of manufacturing glow plug, and glow plug - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress variation in a resistance value of a heating coil, and to improve the temperature rise performance of a heater.SOLUTION: A method of manufacturing a glow plug equipped with a heater having a tube molded in a cylindrical shape, and a heating coil provided in the inside of the tube and heating by energization, includes: a preparing step for preparing the heating coil and the tube; an inserting step for inserting the heating coil into the tube until a spiral tip end portion of the heating coil abuts on an inner peripheral surface of a tip end portion of the tube; a holding step for moving at least one of the heating coil and the tube in an axial direction by predetermined amount so as to separate the spiral tip end portion of the heating coil and the inner peripheral surface on the tip end side of the tube in the axial direction of the tube, after abutting, and holding the heating coil and the tube while moving those by the predetermined amount; and a welding step for welding a welded portion of the heating coil and the tip end portion of the tube in a held state.

Description

  The present invention relates to a method for manufacturing a glow plug and a glow plug.

  The heater of the glow plug includes a tube formed in a cylindrical shape, and a heating coil that is provided in the tube and whose end is welded to the tip of the inner peripheral surface of the tube. Generally, the heating coil has a spiral shape. In Patent Document 1, a hole is formed at the tip of the tube, and a small diameter portion having a diameter smaller than the inner diameter of the tube hole is formed at the end of the heating coil, and the small diameter portion is formed in the hole of the tube. And a method of melting the hole portion of the tube and the small diameter portion of the heating coil to close the hole portion and joining the tube and the heating coil. In Patent Document 1, welding is performed in a state where the inner peripheral surface of the tube and the small diameter portion of the heat generating coil are in contact with each other, and a melting portion (welded portion) is formed.

Japanese Patent No. 4288850

  However, in the method described in Patent Document 1, since the contact position and inclination of the heating coil inserted in the tube are not defined, the position of the heating coil is not stable in the tube. For this reason, at the time of welding the tube and the heating coil, the melting amount of the heating coil (the amount of melting of the heating coil with respect to the melted portion of the tube and the heating coil) becomes uneven, and the resistance value of the heating coil may vary. Variation in the resistance value of the heating coil becomes a factor of deteriorating the temperature raising performance of the heater. Therefore, in the glow plug, a technique for suppressing the variation in the resistance value of the heating coil and improving the temperature raising performance of the heater is desired.

  SUMMARY An advantage of some aspects of the invention is to solve some of the problems described above, and the invention can be implemented as the following forms.

(1) According to an aspect of the present invention, there is provided a method for manufacturing a glow plug including a heater having a tube formed in a cylindrical shape and a heating coil provided inside the tube and generating heat when energized. The According to this method for manufacturing a glow plug, a heat generating coil having a spiral portion formed in a spiral shape, and a welded portion formed on the distal end side of the spiral portion and welded to the tube, Preparing the tube; from the opening formed on the rear end side of the tube into the tube until the distal end of the spiral portion contacts the inner peripheral surface of the distal end of the tube; An insertion step of inserting the heat generating coil; and after the contact, the distal end portion of the spiral portion of the heat generating coil and the inner peripheral surface of the distal end side of the tube are separated along the axial direction of the tube. As described above, at least one of the heat generating coil and the tube is moved by a predetermined amount in the axial direction, and the heat generating coil and the tube are held in a state where the predetermined amount is moved. And lifting steps; in a state where the held, characterized in that it comprises a welding step of welding the said tip of the said welded portion of said heating coil tube. According to the method for manufacturing a glow plug of this embodiment, after the insertion step, the heating coil is arranged so that the distal end portion of the helical portion of the heating coil and the inner peripheral surface on the distal end side of the tube are separated along the axial direction of the tube. And a holding step of holding the heat generating coil and the tube while moving the predetermined amount in the axial direction and moving the predetermined amount in the axial direction, Are welded. Accordingly, the relative positional relationship between the heat generating coil and the tube can be made substantially constant, and the melting amount of the heat generating coil during welding (the amount of melting of the heat generating coil with respect to the molten portion of the tube and the heat generating coil) can be made substantially constant. can do. Therefore, variation in resistance value of the heating coil can be suppressed, and the temperature rise performance of the heater can be improved.

(2) In the method for manufacturing a glow plug according to the above aspect, the measurement step of measuring the resistance value of the heating coil in the held state; and the holding step and the measurement step are performed at least once, and the resistance A specifying step of specifying a relative position between the tube and the heating coil having a predetermined value; and the welding step includes the tube at the position where the resistance value is the predetermined value; It is a process of welding the heat generating coil. According to the method for manufacturing a glow plug of this embodiment, while adjusting the positional relationship between the heating coil and the tube, the resistance value of the heating coil is measured, and the heating coil and tube in which the resistance value of the heating coil becomes a desired value The relative position of is specified. Therefore, the relative positional relationship between the heating coil and the tube can be accurately adjusted to a position where the resistance value of the heating coil becomes a desired value, and variations in the resistance value of the heating coil can be suppressed. Therefore, a glow plug with stable temperature rise performance can be manufactured.

(3) According to an aspect of the present invention, there is provided a glow plug manufactured by the method for manufacturing a glow plug according to the above aspect; the inner surface of the distal end portion of the tube includes the covered portion of the heating coil. A welded portion and a melted portion in which the distal end portion of the tube is melt-bonded; the melted portion is formed in a projecting shape toward the rear end side of the tube, and with respect to the axis of the tube And having a uniform shape in the circumferential direction. According to the glow plug of this embodiment, the melted portion where the heating coil and the tube are melt-bonded is formed to have a uniform shape in the circumferential direction with respect to the axis of the tube. The variation in the temperature distribution of the heater can be suppressed, and the temperature raising performance of the heater can be improved.

  The present invention can be realized in various forms other than the apparatus. For example, the present invention can be realized in the form of a glow plug manufacturing method, a computer program for realizing the manufacturing method, a non-temporary recording medium on which the computer program is recorded, and the like.

Explanatory drawing which shows the glow plug 10 in 1st Embodiment. FIG. 3 is a cross-sectional view mainly showing a detailed configuration of a sheath heater 800 in the glow plug 10 according to the first embodiment. Explanatory drawing explaining the shape of the fusion | melting part 850 of the sheath heater 800 in 1st Embodiment. Explanatory drawing which compares the shape about the fusion | melting part 850 of the sheath heater 800 of 1st Embodiment, and the fusion | melting part 850a of the conventional sheathed heater 800a. The flowchart explaining the manufacturing process of the sheath heater 800 in 1st Embodiment. The schematic cross section explaining the manufacturing process of the sheath heater 800 in 1st Embodiment. Explanatory drawing which shows the relative positional relationship of the tube 810 and the heating coil 840 before the welding process of step S110.

A. First embodiment:
A1. Glow plug configuration:
FIG. 1 is an explanatory view showing a glow plug 10. The glow plug 10 includes a sheath heater 800 that generates heat, and functions as a heat source that assists ignition when starting an internal combustion engine (not shown) such as a diesel engine. The glow plug 10 includes a center shaft 200 and a metal shell 500 in addition to the sheath heater 800. These members constituting the glow plug 10 are assembled along the central axis SC of the glow plug 10. In FIG. 1, the glow plug 10 is divided by a central axis SC, an external configuration is illustrated on the right side of the drawing from the central axis SC, and a cross-sectional configuration is illustrated on the left side of the drawing from the central axis SC. In this specification, the sheath heater 800 side of the glow plug 10 is referred to as a “front end side”, and the engagement member 100 side is referred to as a “rear end side”.

  The metal shell 500 of the glow plug 10 is a member obtained by forming carbon steel into a cylindrical shape. The metal shell 500 holds the sheath heater 800 at the end on the front end side, holds the center shaft 200 via the insulating member 410 and the O (O) ring 460 at the end on the rear end side, and the sheath heater 800 from the insulating member 410. The part of the middle shaft 200 leading to is included. The metal shell 500 includes a shaft hole 510, a tool engaging portion 520, and a male screw portion 540. The shaft hole 510 of the metal shell 500 is a through-hole formed along the central axis SC and has a larger diameter than the middle shaft 200. In a state where the middle shaft 200 is positioned in the shaft hole 510, a gap is formed between the shaft hole 510 and the middle shaft 200 to electrically insulate them. A sheath heater 800 is press-fitted and joined to the distal end side of the shaft hole 510. The tool engaging portion 520 of the metal shell 500 is engaged with a tool (not shown) used for attaching and detaching the glow plug 10, and the male screw portion 540 of the metal shell 500 is formed in the internal combustion engine (not shown). Fits a female screw.

  The middle shaft 200 of the glow plug 10 is a member formed of a conductive material into a cylindrical shape, and is assembled on the central axis SC in a state of being inserted into the shaft hole 510 of the metal shell 500. The middle shaft 200 includes a front end portion 210 formed on the front end side and a male screw portion 290 provided on the rear end side. The distal end portion 210 of the middle shaft 200 is inserted into the sheath heater 800. On the other hand, the male thread portion 290 of the middle shaft 200 protrudes from the metal shell 500 and fits into the engaging member 100. The engaging member 100 holds the insulating member 410 via the ring 300. In this embodiment, power is supplied to the sheath heater 800 from the outside of the glow plug 10 through the male screw portion 290 of the central shaft 200.

  FIG. 2 is a cross-sectional view mainly showing a detailed configuration of the sheath heater 800 in the glow plug 10. The sheath heater 800 of the glow plug 10 is provided on the distal end side of the metallic shell 500. In this embodiment, the sheath heater 800 is press-fitted into the shaft hole 510 of the metallic shell 500 with the distal end portion 210 of the middle shaft 200 inserted into the sheath heater 800. It is joined. The sheath heater 800 includes a tube 810, a heating coil 840, insulating powder 860, and a melting part 850. The heat generating coil 840 has a heat generating portion 820 formed in a spiral shape and a control portion 830 formed in a spiral shape.

  The tube 810 of the sheath heater 800 is a member formed of a nickel (Ni) alloy, which is a conductive material, and is formed in a cylindrical shape with a distal end portion 811 that is an end portion on the distal end side closed, and includes a heating coil 840 and an insulating powder 860. Contain. The tube 810 includes a rear end portion (not shown) that is an end portion opened to the side opposite to the front end portion 811, and the front end portion 210 of the central shaft 200 is inserted into the tube 810 from the rear end portion. . The tube 810 is electrically insulated from the center shaft 200 by the packing 600 and the insulating powder 860, while being in contact with and electrically connected to the metal shell 500.

  The heat generating portion 820 of the sheath heater 800 is a coil formed of an iron (Fe) -chromium (Cr) -aluminum (Al) alloy that is a conductive material, and is provided inside the tube 810 and generates heat when energized. The heat generating portion 820 includes a front end portion 821 that is a coil end portion on the front end side, and a rear end portion 829 that is a coil end portion on the rear end side. The distal end portion 821 of the heat generating portion 820 is electrically connected to the tube 810 by being welded inside the distal end portion 811 of the tube 810, and the rear end portion 829 of the heat generating portion 820 is welded to the control portion 830. Is electrically connected to the control unit 830.

  The control unit 830 of the sheath heater 800 is a coil formed of a conductive material (for example, an alloy containing cobalt or nickel as a main component) having a higher temperature coefficient of electrical specific resistance than the material forming the heat generating unit 820, and the tube 810. The power supplied to the heat generating unit 820 is controlled. The control unit 830 includes a front end 831 that is a coil end on the front end side, and a rear end 839 that is a coil end on the rear end side. The front end 831 of the control unit 830 is electrically connected to the heat generating unit 820 by welding to the rear end 829 of the heat generating unit 820, and the rear end 839 of the control unit 830 is connected to the front end 210 of the middle shaft 200. By being joined, the center shaft 200 is electrically connected.

  The insulating powder 860 of the sheath heater 800 is a powder of an insulating material having an electrical insulating property, is filled inside the tube 810, and electrically insulates the gaps between the tube 810, the heat generating unit 820, the control unit 830, and the central shaft 200. . In this embodiment, the insulating powder 860 is a magnesium oxide (MgO) powder.

  The melted portion 850 of the sheath heater 800 is a joint portion between the tube 810 and the heat generating portion 820. The melting part 850 is formed by melting and solidifying the tube 810 and the heat generating part 820 by welding. The fusion | melting part 850 is demonstrated with reference to FIG. 3 and FIG.

A2. Detailed configuration of melting section 850:
FIG. 3 is an explanatory diagram for explaining the shape of the melting portion 850 of the sheath heater 800 according to the first embodiment. Fig.3 (a) is sectional drawing cut | disconnected in the AA cross section of FIG. FIG. 3B is a cross-sectional view taken along the line B-B in FIG. 3A, and is an arbitrary cross section of the melting portion 850 including the axis OL of the sheath heater 800 and parallel to the axis OL. The axis OL of the sheath heater 800 is the same as the central axis SC of the glow plug 10. As shown in FIG. 3A, the melting part 850 is formed in a protruding shape so as to protrude toward the rear end side on the bottom surface 815 a of the inner peripheral surface 815 of the tube 810. Further, as shown in FIG. 3B, the melting part 850 has a uniform shape in the circumferential direction Y with respect to the axis OL of the tube 810. The circumferential direction Y is a circumferential direction with the axis OL as the central axis. The inner peripheral surface of the body portion 813 of the tube 810 is also referred to as a side surface 815b.

  Specifically, the circumferentially uniform shape is the shape of each of the half cross sections 855 and 856 divided by the axis OL in an arbitrary cross section of the melting portion 850 including the axis OL and parallel to the axis OL, and It is included that the thickness along the axis OL is substantially line symmetric with respect to the axis OL except for the coil connection portion 858. In FIG. 3B, only a cross section obtained by cutting the melted portion 850 from one direction is shown. However, in any cross section including the axis OL and parallel to the axis OL, the axis OL The shape of each half section to be divided and the thickness along the axis OL are substantially line symmetric with respect to the axis OL except for the coil connection portion 858.

  Further, the heating coil 840 may be welded to the side surface (portion excluding the top and bottom) of the melting portion 850. When the end of the heating coil 840 is welded to the bottom of the melting part 850, the vicinity of the bottom is raised, and the melting part 850 is unlikely to have a uniform shape in the circumferential direction Y. Therefore, the end portion of the heating coil 840 is welded to the side surface of the melting portion 850, so that the melting portion 850 has a uniform shape in the circumferential direction Y with high accuracy.

  FIG. 4 is an explanatory diagram showing a comparison of the shapes of the melting portion 850 of the sheath heater 800 of the first embodiment and the melting portion 850a of the conventional sheath heater 800a. FIG. 4A is a cross-sectional view of the melting portion 850 of the first embodiment that passes through the axis OL and is along the axis OL. FIG. 4B is a cross-sectional view along the axis OLa of the melting portion 850a of the conventional sheathed heater 800a as a comparative example while passing through the axis OLa. The tube 810a of the sheath heater 800a is the same as the sheath heater 800. In the first embodiment, the point that the melting portion 850 has a uniform shape in the circumferential direction Y with respect to the axis OL of the tube 810 will be described more specifically with reference to FIG.

  In the first embodiment, the melting part 850 has a uniform shape in the circumferential direction Y with respect to the axis OL of the tube 810. As shown in FIG. 4A, the melting part 850 is along the axis OL. In other words, the ratio of the maximum value Da to the minimum value Db of the thickness satisfies 1.0 or more and 1.2 or less.

  As shown in FIG. 4B, the melted portion 850a of the conventional sheath heater 800a has a relatively large difference between the minimum value Db ′ and the maximum value Da ′ along the axis OLa, and the minimum value Db ′. The ratio of the maximum value Da ′ with respect to was over 1.2. In addition, in an arbitrary cross section of the melted portion 850a including the axis line OLa and parallel to the axis line OLa, the shape of each half section divided by the axis line OLa was non-uniform. Thus, when the fusion | melting part 850a is formed in imbalance in the circumferential direction of a tube, the temperature rising performance in the circumferential direction of a tube changes with parts, and there exists a possibility of causing the fall of rapid temperature rising performance as the whole sheath heater.

  In the sheath heater 800 of the first embodiment, the melting part 850 has a uniform shape in the circumferential direction Y with respect to the axis OL of the tube 810, so that the temperature rise performance in the circumferential direction of the tube is substantially uniform in any part. Become. Therefore, the rapid temperature raising performance is improved as a whole of the sheath heater 800. A method for manufacturing the sheath heater 800 of the first embodiment will be described later.

A3. Measurement result:
Tables 1 and 2 show measurement results obtained by measuring the temperature variation along the circumferential direction of the sheath heater. The measuring method is as follows. The rear end side of the tube of the sheath heater is fixed by a holding member, and is heated and held so that the temperature at the rear end position by 2 mm in the axial direction from the front end of the tube is 1000 ° C. In a state where the tube is heated and held, the temperature is measured by a radiation thermometer while rotating by 1 ° about the axis line OL as the central axis through the holding member. “Temperature variation width” in Tables 1 and 2 is the position of the rear end of the tube by 2 mm in the axial direction from the tip of the tube, and is the maximum and minimum values at the temperatures measured at different circumferential Y positions. The difference is shown. In Tables 1 and 2, the criteria are as follows.
OK: Temperature variation width is within ± 10 ° C NG: Temperature variation width exceeds ± 10 ° C

  Table 1 shows the measurement results for a sheath heater having a tube having a body (side surface) thickness of 0.4 mm. Examples 1 to 3 show the sheath heater 800 having the melting part 850 included in the first embodiment, and the melting part 850 has a maximum value (Da) with respect to the minimum value (Db) of the thickness along the axis OL. Has a shape satisfying a ratio of 1.0 to 1.2. Comparative Examples 1 to 6 show a conventional sheath heater 800a, and the ratio of the maximum value Da ′ to the minimum value (Db ′) of the melted portion 850a along the axis OLa exceeds 1.2. It has a shape.

  Table 2 shows the measurement results for a sheath heater having a tube having a body (side surface) thickness of 0.7 mm. Examples 4 to 6 show the sheath heater 800 having the melting part 850 included in the first embodiment, and the melting part 850 has a maximum value (Da) with respect to the minimum value (Db) of the thickness along the axis OL. Has a shape satisfying a ratio of 1.0 to 1.2. Comparative Examples 7 to 12 show a conventional sheathed heater 800a, and the ratio of the maximum value Da ′ to the minimum value (Db ′) of the melted portion 850a along the axis OLa exceeds 1.2. It has a shape.

  As shown in Tables 1 and 2, the melted portion 850 has a shape in which the ratio of the maximum value (Da) to the minimum value (Db) of the thickness along the axis OL satisfies 1.0 or more and 1.2 or less. The sheath heater 800 of the first embodiment having the above has a temperature variation width of 9 ° C. at the maximum, and the temperature variation width is relatively small. That is, it can be seen that the sheath heater 800 of the first embodiment has uniform temperature performance in the circumferential direction of the tube. On the other hand, in the sheath heater 800a of the comparative example, the temperature variation width may exceed 40 ° C., and the temperature variation width is large. That is, it can be seen that the temperature performance of the sheath heater 800a of the comparative example is not uniform in the circumferential direction of the tube.

B. Production method:
B1. Manufacturing process:
FIG. 5 is a flowchart for explaining a manufacturing process of the sheath heater 800 according to the first embodiment. FIG. 6 is a schematic cross-sectional view illustrating a manufacturing process of the sheath heater 800 in the first embodiment. In step S100, a preparation process for preparing the tube 810 and the heating coil 840 is performed. At this time, as shown in FIG. 6A, the tube 810 to be prepared is formed in a cylindrical shape, is formed on the body portion 813 and the front end side of the body portion 813, compared to the body portion 813. And a projecting opening 812 formed with a reduced diameter. The heating coil 840 includes a control unit 830 formed in a spiral shape, a heat generation unit 820 formed in a spiral shape, and a welded portion 845 formed on the distal end side of the heat generation unit 820 and welded to the tube 810. Have. The control unit 830 and the heat generation unit 820 are collectively referred to as a spiral portion 846.

  In step S102, an insertion step of inserting the heating coil 840 into the tube 810 is performed. Specifically, as shown in FIG. 6 (b), the distal end portion of the spiral portion 846, that is, the distal end portion 821 of the heat generating portion 820 contacts the inner peripheral surface 815 of the distal end portion of the body portion 813 of the tube 810. The heat generating coil 840 is inserted into the body portion 813 of the tube 810 from the opening 816 formed on the rear end side of the tube 810 until contact. At this time, since the heating coil 840 is not held, the heating unit 820 and the control unit 830 are contracted in the direction of the axis OL due to their own weight. Further, the welded portion 845 of the heating coil 840 is accommodated in the projecting opening 812 of the tube 810.

  In step S104, after the distal end portion 821 of the heat generating portion 820 contacts the inner peripheral surface 815 of the distal end portion of the body portion 813 of the tube 810, the heat generating coil 840 is held in a state where it is moved by a predetermined amount in the direction of the axis OL. A holding step is performed. Specifically, as shown in FIG. 6C, the distal end portion 821 of the spiral portion 846 of the heating coil 840 and the inner peripheral surface 815 on the distal end side of the tube 810 extend along the axis OL direction of the tube 810. The heating coil 840 is moved by a predetermined amount in the direction of the axis OL so as to be separated from each other. In the first embodiment, the heating coil 840 is moved by a predetermined amount. However, by moving at least one of the heating coil 840 and the tube 810 by a predetermined amount in the axis OL direction, the tube 810 and the heating coil 840 are moved. It may be separated. With the heating coil 840 moved by a predetermined amount, the holding shaft 700 chucks the central shaft 200, whereby the heating coil 840 is held, and the relative positional relationship between the tube 810 and the heating coil 840 is held. The predetermined amount is appropriately selected depending on the shape and size of the tube 810 and the heating coil 840, but may be 0.2 mm to 0.4 mm, for example.

  In step S106, a measurement process for measuring the resistance value of the heating coil 840 is performed. For example, measuring means may be connected to the entire sheath heater 800 to measure the combined resistance value of the tube 810, the central shaft 200, and the heating coil 840, and the combined resistance value may be used as the resistance value of the heating coil 840.

  In step S108, the holding process (step S104) and the measurement process (step S106) are performed at least once, and the relative position between the tube 810 and the heat generating coil 840 is determined so that the resistance value of the heat generating coil 840 becomes a predetermined value. A specific process is performed. In the specific process, when the resistance value is a predetermined value (step S108: YES), the welding process of step S110 is performed. In the specific process, when the resistance value is not a predetermined value (step S108: NO), the process is repeated from the holding process (step S104).

  FIG. 7 is an explanatory diagram showing the relative positional relationship between the tube 810 and the heating coil 840 before the welding process in step S110. FIG. 7A shows the positional relationship between the tube 810 and the heating coil 840 of the sheath heater 800 in the first embodiment. FIG. 7B shows the positional relationship between the tube 810a and the heating coil 840a of the sheath heater 800a in the conventional example.

  The conventional sheath heater 800a does not include a step of moving at least one of the tube 810a and the heating coil 840a by a predetermined amount along the direction of the axis OLa after the insertion step. Therefore, as shown in FIG. 7B, the axis C of the heating coil 840a is inclined with respect to the axis OLa. Since the inclination of the heat generating coil 840a is not constant, the position of the heat generating coil 840a in the tube 810a is unstable, and the position where the heat generating coil 840a contacts the tube 810a and the contact amount (contact area) are manufactured. The sheath heater 800a is not uniform. If the position where the heat generating coil 840a contacts the tube 810a or the contact amount (contact area) is unstable, the amount of melting (melting amount) of the heat generating coil 840a is produced when the tube 810a and the heat generating coil 840a are welded. The temperature of the sheathed heater 800a varies depending on the sheathed heater 800a. As a result, the yield of the sheath heater 800a is reduced.

  In the sheath heater 800 of the first embodiment, since the holding process is performed after the insertion process, the axis C of the heating coil 840 is not excessively inclined with respect to the axis OL as shown in FIG. The inclination of the coil 840 is substantially constant. Since the dimension of the heat generating coil 840 is defined in advance, the amount of melting of the heat generating coil 840 (melting) is achieved by moving at least one of the tube 810 and the heat generating coil 840 to a specific position along the axis OL direction. Amount) can be controlled to be substantially constant. As a result, the volume of the melting part 850 can be controlled, and the shape of the melting part 850 can be made uniform in the circumferential direction Y with respect to the axis OL of the tube 810. In the first embodiment, in the holding step, the tube 810 and the heating coil 840 are separated from each other, but at least one of the tube 810 and the heating coil 840 is moved by a predetermined amount along the axis OL direction. The tube 810 and the heating coil 840 may be in contact with each other. By moving the predetermined amount, in the welding process described later, the amount of melting of the tube 810 and the heating coil 840 becomes substantially constant, so that the melting portion 850 is formed in a uniform shape in the circumferential direction Y as described above. Is done. That is, “so as to be separated” in the scope of the claims indicates the direction of movement, and includes both being separated and not separated after a predetermined amount of movement.

  In step S110, a welding process in which the tube 810 and the heating coil 840 are welded is performed. Specifically, as shown in FIG. 6D, in a state where the tube 810 and the heat generating coil 840 are held, the protrusions formed at the welded portion 845 of the heat generating coil 840 and the tip of the tube 810 are formed. The shaped opening 812 is welded. For welding, various known welding methods such as laser welding and resistance welding may be used.

  As described above, the tube 810 and the heat generating coil 840 are welded, and the melting portion 850 having a uniform shape in the circumferential direction Y with respect to the axis OL of the tube 810 is formed at the distal end portion of the inner peripheral surface 815 of the tube 810. Is formed.

The measurement results of measuring the resistance value of the heating coil welded to the tube will be described. The following two types of tubes were used for this measurement. The “conventional manufacturing process” described below refers to a manufacturing process that does not include a process in which at least one of the tube and the heating coil is moved by a predetermined amount along the axial direction of the tube after the insertion process (step S100). means.
<Sample 1>
Tube: Inconel heating coil: 0.4 mm diameter Fe-Cr-Al alloy <Sample 2>
Tube: Made of SUS
Heating coil: 0.3 mm diameter Fe-Cr-Al alloy

  The resistance value of the heating coil when the tube of sample 1 and the heating coil were welded by the manufacturing process of the first embodiment described above was 0.63 ± 0.01Ω. on the other hand. The resistance value of the heating coil when the tube of sample 1 and the heating coil were welded by the conventional manufacturing process was 0.60 ± 0.04Ω.

  The resistance value of the heating coil when the tube of sample 2 and the heating coil were welded by the manufacturing process of the first embodiment described above was 1.27 ± 0.03Ω. on the other hand. The resistance value of the heating coil when the tube of Sample 2 and the heating coil were welded by the conventional manufacturing process was 1.15 ± 0.15Ω.

  As described above, when the tube and the heating coil are welded by the manufacturing process of the first embodiment, variation in the resistance value of the heating coil is reduced. Further, as described above, since the volume and shape of the melting portion 850 can be controlled uniformly, the temperature performance of the sheath heater is stabilized.

  According to the glow plug 10 of the first embodiment described above, the melting portion 850 in which the heating coil 840 and the tube 810 are melt-bonded has a uniform shape in the circumferential direction Y with respect to the axis OL of the tube 810. In the circumferential direction of the tube 810, it is possible to suppress the occurrence of excessive variation in the temperature distribution, and the temperature raising performance of the sheath heater 800 can be improved.

  Further, according to the glow plug 10 of the first embodiment, the melted portion 850 is formed so that the ratio of the maximum value Da to the minimum value Db is 1.0 or more and 1.2 or less with respect to the thickness. Therefore, the temperature distribution width (temperature variation width) in the circumferential direction Y of the tube 810 can be further reduced. Therefore, in the circumferential direction Y of the tube 810, variations in temperature distribution can be further suppressed, and the temperature raising performance of the heater can be improved.

  Further, according to the method for manufacturing the glow plug 10 of the first embodiment, after the insertion step (step S102), the distal end portion 821 of the spiral portion 846 of the heating coil 840 and the bottom surface that is the inner peripheral surface of the distal end side of the tube 810. At least one of the heating coil 840 and the tube 810 is moved a predetermined amount in the axis OL direction so that it is separated from the tube 810 along the axis OL direction of the tube 810. The heating coil 840 and the tube 810 are welded in the holding state (step S104). Therefore, the relative positional relationship between the heat generating coil 840 and the tube 810 can be made substantially constant, and the melting amount of the heat generating coil 840 during welding (the melting of the heat generating coil 840 into the melted portion of the tube 810 and the heat generating coil 840). Amount) can be made substantially constant. Therefore, variation in the resistance value of the heating coil 840 can be suppressed, and the temperature rise performance of the sheath heater 800 can be improved.

  Further, according to the method for manufacturing the glow plug 10 of the first embodiment, the resistance value of the heating coil 840 is measured while the positional relationship between the heating coil 840 and the tube 810 is adjusted, and the resistance value of the heating coil 840 is desired. The relative position of the heating coil 840 and the tube 810 having the value of is specified. Therefore, the relative positional relationship between the heating coil 840 and the tube 810 can be accurately adjusted to a position where the resistance value of the heating coil 840 becomes a desired value, and variations in the resistance value of the heating coil 840 can be suppressed. Therefore, the glow plug 10 with stable temperature rising performance can be manufactured.

C. Variations:
・ Modification 1:
Although the first embodiment includes a specific process that repeats the holding process and the measurement process, the movement distance between the heating coil 840 and the tube 810 may be defined in advance, and the measurement process and the specific process may be omitted.

・ Modification 2
In the first embodiment, the heat generating coil 840 is moved. However, even if the tube 810 is moved along the axis OL while the heat generating coil 840 is fixed so that the tube 810 is separated from the heat generating coil 840, the heat generating coil 840 is moved. Alternatively, both the heating coil 840 and the tube 810 may be moved away from each other along the axis OL.

  The present invention is not limited to the above-described embodiments, examples, and modifications, and can be realized with various configurations without departing from the spirit thereof. For example, the technical features in the embodiments, examples, and modifications corresponding to the technical features in each embodiment described in the summary section of the invention are to solve some or all of the above-described problems, or In order to achieve part or all of the above effects, replacement or combination can be performed as appropriate. Further, if the technical feature is not described as essential in the present specification, it can be deleted as appropriate.

DESCRIPTION OF SYMBOLS 10 ... Glow plug 100 ... Engagement member 200 ... Middle shaft 210 ... Tip part 290 ... Male screw part 300 ... Ring 410 ... Insulation member 460 ... Ring 500 ... Metallic metal body 510 ... Shaft hole 520 ... Tool engagement part 540 ... Male screw part DESCRIPTION OF SYMBOLS 600 ... Packing 700 ... Holding member 800 ... Sheath heater 800a ... Sheath heater 810 ... Tube 810a ... Tube 811 ... Tip part 812 ... Projection opening part 813 ... Body part 815 ... Inner peripheral surface 815a ... Bottom face 815b ... Side face 816 ... Opening part 820 ... Heat generation part 821 ... front end part 829 ... rear end part 830 ... control part 831 ... front end part 839 ... rear end part 840 ... heat generation coil 840a ... heat generation coil 845 ... welded part 846 ... helical part 850 ... melting part 850a ... melting part 855, 856 ... Half cross section 860 ... Insulating powder

Claims (3)

A glow plug manufacturing method comprising a heater having a tube formed in a cylindrical shape and a heating coil provided inside the tube and generating heat when energized,
A preparatory step of preparing a heat generating coil having a helical portion formed in a helical shape, a welded portion formed on the distal end side of the helical portion and welded to the tube, and the tube;
An insertion step of inserting the heating coil into the tube from the opening formed on the rear end side of the tube until the tip of the spiral portion contacts the inner peripheral surface of the tip of the tube;
After the abutment, the heating coil and the tube are arranged such that the distal end portion of the helical portion of the heating coil and the inner peripheral surface on the distal end side of the tube are separated from each other along the axial direction of the tube. A holding step of holding at least one of the heating coil and the tube while moving the predetermined amount in the axial direction and moving the predetermined amount;
A glow plug manufacturing method comprising: a welding step of welding the welded portion of the heating coil and the tip end portion of the tube in the held state. The method for manufacturing a glow plug according to claim 1, further comprising:
A measuring step of measuring a resistance value of the heating coil in the held state;
A step of performing the holding step and the measuring step at least once, and specifying a relative position of the tube and the heating coil at which the resistance value is a predetermined value,
The method for manufacturing a glow plug, wherein the welding step is a step of welding the tube and the heating coil at the position where the resistance value is the predetermined value. A glow plug manufactured by the method of manufacturing a glow plug according to claim 1 or 2,
On the inner peripheral surface of the tip portion of the tube, the welded portion of the heating coil and the tip portion of the tube are melted and joined,
The glow plug is characterized in that the melting portion is formed in a projecting shape toward the rear end side of the tube and has a uniform shape in the circumferential direction with respect to the axis of the tube.

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