JP4880532B2 - Manufacturing method of spark plug - Google Patents

Description

  The present invention relates to a method for manufacturing a spark plug (a spark plug) attached to an engine.

  FIG. 1 shows an example of a conventional spark plug 1 in a schematic half-sectional view. The spark plug 1 is made of a metal-made metallic shell 3 having a cylindrical shape, a cylindrical insulator 5 that is held in the metallic shell 3 and inserted into the metallic shell 3. The center electrode 7 and a ground electrode 33 attached to the tip (tip surface) 31 of the metal shell 3 by welding are also included. Such a spark plug 1 is connected to a cylinder head of an engine (not shown) via a mounting screw 35 formed on the outer peripheral surface of a portion (small-diameter cylindrical portion 3a) closer to the tip (lower end in the figure) of the metal shell 3 constituting the spark plug 1. It is screwed into the plug hole (screw hole) and is attached to the engine. In this screwing, screwing with a predetermined tightening torque is performed via a polygonal portion 40 that is a spiral portion provided at a portion (large-diameter cylindrical portion 3b) near the rear end (the upper end in the drawing) of the metal shell 3. Tightening is performed, and a predetermined amount is screwed in until the ring-shaped mounting flange 42 for positioning and sealing comes into contact with the mounting seat surface of the plug hole. In the present application, the term “tip” in the spark plug 1 or its components and parts (or portions) including the metal shell 3 refers to the lower ends thereof in FIG.

  By the way, the ground electrode 33 of the metal shell 3 is attached to the tip 31 of the metal shell 3 by welding. However, in order to form a spark discharge gap with the tip of the center electrode 7, the tip-side portion 33a is set sideways. It has a J (or L) shape formed by bending. For this reason, in a state where the spark plug 1 is attached to the engine, the spark discharge gap is behind the base end portion (vertical portion) 33b of the ground electrode 33 with respect to the swirl direction of the air-fuel mixture. The presence of the vertical portion (hereinafter also simply referred to as a ground electrode) 33b of the ground electrode in a direction that hinders the flame growth is not preferable in terms of the ignitability of the spark plug 1. That is, when the spark plug 1 is mounted in the plug hole of the cylinder head of the engine, the ground electrode 33b is set not to be in the shade of the swirl direction of the air-fuel mixture and to a position that does not exist in a direction that prevents flame growth. It is preferable to do this.

  For this purpose, when the threading start position of the plug hole on the engine side is constant, the mounting position of the ground electrode 33 with respect to the tip 31 of the metal shell 3 is set to the threading start position of the mounting screw 35 on the tip 31 side, for example. Therefore, when the spark plug 1 is theoretically screwed and attached to the plug hole with a predetermined torque (same torque) by setting it at a predetermined position around the axis G, the ground electrode 33b is connected to the mixture gas. It can exist in the position which does not prevent progress of a swirl, or the specific range on the basis of the position. That is, when the ground electrode 33 is attached (welded) to the tip 31 of the metal shell 3, the tip 31 of the metal shell 3 is related to the threading start position on the tip 31 side of the metal shell 3 among the mounting screws 35. The ground electrode 33 may be welded to a predetermined position around the axis G of the screw 35.

Therefore, conventionally, when manufacturing the metal shell 3 as described above, the mounting screw 35 is formed in advance, and when the ground electrode 33 is welded, the ground electrode at the tip 31 is welded by the following method. A predetermined position (a position for attaching a ground electrode) to be determined was determined. That is, the metal shell 3 is screwed from the front end side thereof with a predetermined torque (same set torque) into a female screw positioning jig (screw ring or screw gauge) made (as a model) assuming a plug hole (mounting screw hole), The ground electrode mounting position at the tip of the metal shell is indexed based on the position where the preset ground electrode is to be welded around the screw axis of the positioning jig with a female screw, and the indexed ground electrode mounting position is determined. The ground electrode is positioned and welded (Patent Documents 1 and 2).
JP 11-013613 A JP 2002-141156 A

  However, as in the technique described in the above-mentioned patent document, when the ground electrode mounting position at the tip of the metal shell is indexed and the ground electrode is positioned and welded to the indexed ground electrode mounting position, There were the following problems. This is because, in such an indexing method, first, it is necessary to screw the metal shell into the positioning jig with a female screw, but since the screwing depth is relatively long, a lot of time is required for the screwing. Cost. Second, in this method, it is necessary to separate (remove) the metal shell from the positioning jig with the female screw even after screwing and indexing the position for attaching the ground electrode. It is necessary to retire). Further, thirdly, there is a restriction that the ground electrode is usually welded after the metal shell is separated from the female jig positioning jig. This is because when welding is performed before separation, the occurrence of welding sag prevents the screw from being removed, and in this case, finishing (cutting, removing) of the sag portion is required before the separation. As described above, in the conventional method described above, there is a problem that it takes a lot of time to index the position for attaching the ground electrode at the tip of the metal shell. For this reason, the manufacturing efficiency of the metal shell and thus the spark plug is low. There was a problem.

  The present invention has been made in view of such problems. By screwing the metal shell into a positioning jig with a female thread, the ground electrode mounting position at the tip is indexed, and the grounded electrode mounting position is grounded. By manufacturing the metal shell by welding the electrodes, the time required for screwing (screwing) or separating (screwing) the metal shell into the positioning jig with a female screw can be shortened or omitted. , To increase its production efficiency.

According to the first aspect of the present invention, a metal shell, which is a spark plug component and has a mounting screw formed on the outer peripheral surface thereof, is screwed into a positioning jig with a female screw with a predetermined torque from the front end side thereof. Indexing a predetermined position corresponding to a reference position set in advance around the axis of the screw in the female screw positioning jig as a ground electrode mounting position, and attaching the ground electrode to the ground electrode mounting position In a method for manufacturing a spark plug, including
The female screw positioning jig is composed of a jig divided body divided into a plurality when viewed from the axial direction of the screw, and each jig divided body can be opened and closed in the radial direction of the screw and closed. Sometimes we have to configure a positioning jig with a female thread,
In the state where the plurality of jig divisions are opened,
The metal shell is held at a position where the mounting screw is surrounded by the plurality of jig divisions when viewed from the axial direction, and the metal fittings are closed when the plurality of jig divisions are closed. The mounting screw is in a state where it has not been screwed into the positioning jig with female screw, and at least a part of its thread is in a positional relationship to be screwed,
After this arrangement, the plurality of jig divisions are closed, and then the metal shell is screwed in with a predetermined torque from the unscrewed incomplete state to the completed state, and the female screw is attached to the tip of the metal shell. Indexing a predetermined position corresponding to the reference position of the positioning jig as a ground electrode mounting position,
Thereafter, the plurality of jig divisions are opened to separate the metal shell from which the position for attaching the ground electrode is indexed from the positioning jig with the female thread,
Thereafter, a step of attaching a ground electrode to the ground electrode mounting position at the tip of the metal shell is characterized.

According to the second aspect of the present invention, a metal shell, which is a spark plug component and has a mounting screw formed on the outer peripheral surface thereof, is screwed into a positioning jig with a female screw with a predetermined torque from the front end side of the metal shell. A step of indexing a predetermined position corresponding to a reference position set in advance around the axis of the screw in the female screw positioning jig among the tips as a ground electrode mounting position, and attaching the ground electrode to the ground electrode mounting position. Including a spark plug manufacturing method,
The female screw positioning jig is composed of a jig divided body divided into a plurality when viewed from the axial direction of the screw, and each jig divided body can be opened and closed in the radial direction of the screw and closed. Sometimes we have to configure a positioning jig with a female thread,
To the positioning jig with a female screw in the state where the plurality of jig divisions are closed,
Screwing the metal shell with a predetermined torque until the screwing is completed, and indexing a predetermined position corresponding to the reference position of the positioning jig with the female screw among the tips of the metal shell,
Thereafter, the plurality of jig divisions are opened to separate the metal shell from which the position for attaching the ground electrode is indexed from the positioning jig with the female thread,
Thereafter, a step of attaching a ground electrode to the ground electrode mounting position at the tip of the metal shell is characterized.

  According to a third aspect of the present invention, in the jig divided body according to the first or second aspect, in a state where the jig divided body is closed, at least a portion near the front end of the metallic shell on a screw-in opening side into which the metallic shell is screwed. Is provided with a positioning guide in which the mounting screw and the axis of the screw of the positioning jig with a female screw are coaxially positioned.

The present invention as defined in claim 4 is characterized in that in claims 1 to 3,
Indexing a predetermined position corresponding to the reference position of the female threaded positioning jig among the tips of the metal shell as a ground electrode mounting position,
Thereafter, the plurality of jig divisions are opened to separate the metal shell from which the position for attaching the ground electrode is indexed from the positioning jig with the female thread,
Thereafter, a ground electrode is attached to the ground electrode mounting position at the tip of the metal shell,
Instead,
Indexing a predetermined position corresponding to the reference position of the female threaded positioning jig among the tips of the metal shell as a ground electrode mounting position,
Under the indexed state, a ground electrode is attached to the ground electrode attachment position at the tip of the metal shell,
Thereafter, a plurality of the jig divided bodies are opened, and the metal shell to which the ground electrode is attached is separated from the female jig positioning jig.

  The present invention according to claim 5 is characterized in that the plurality of jig division bodies constituting the female screw positioning jig are divided into two when viewed from the axial direction of the screw. Item 5. The spark plug manufacturing method according to any one of Items 1 to 4. And as for this invention of Claim 6, as for the said jig | tool division | segmentation body, the screw is formed in the 1 or more thing in the plurality, The any one of Claims 1-5 characterized by the above-mentioned. A method for producing a spark plug as described in 1. above.

   The effect of the invention of claim 1 is as follows. The main electrode is screwed into the positioning jig with a female screw at a predetermined torque, which is not divided like the screw ring used in the conventional manufacturing method (corresponding to the female jig positioning jig in the present invention), and the ground electrode with respect to the threading start position In the method of making the relative position of the screw constant, for example, when the screw of the positioning jig with a female screw is all screws, the metal shell is rotated by the length of the mounting screw, that is, by the number of screw threads. It will be necessary. Therefore, there is a problem that the screwing takes a lot of time. On the other hand, in the present invention, when the jig divided body constituting the female jig positioning jig is closed, for example, if one screw is in a screwed state where screwing is not completed, Requires only one rotation of the metal shell. Therefore, in the present invention, the time required for screwing the metal shell into the positioning jig with a female screw for the indexing of a predetermined position (ground electrode mounting position) where the ground electrode is to be mounted (the time required for setting the screw ring) Since the shortening is achieved, the manufacturing efficiency of the metal shell can be improved by the shortening, and as a result, the manufacturing efficiency of the spark plug can be improved.

  Moreover, in the case of the conventional non-divided screw ring, in order to separate the metal shell from the ground electrode mounting position after indexing, it is necessary to reversely rotate the metal fitting corresponding to the screwing amount. Separation also takes a lot of time. On the other hand, in the present invention, in the separation, the separation can be performed by opening a jig divided body forming a positioning jig with a female screw. Accordingly, the time for separating the metallic shell from the female-threaded positioning jig can be largely omitted, so that the manufacturing efficiency can be further improved accordingly. In the present invention, the “predetermined position corresponding to a reference position preset around the axis of the screw in the female screw positioning jig among the tips of the metal shell” is a plug of a cylinder head of an engine as a spark plug. When the screw is attached to the hole with a predetermined torque, the ground electrode is not shaded in the swirl direction of the air-fuel mixture and does not exist in a direction that prevents flame growth. It is a position set relatively in relation to the start position. Therefore, the predetermined position may be a position that matches the reference position set in the positioning jig with a female screw, or may be a position that is rotated by a predetermined angle around the axis of the screw with respect to the reference position. Further, the predetermined position may be determined as being within a predetermined angle range.

  The effect of the invention of claim 2 is as follows. According to the second aspect of the present invention, the metal shell is screwed into the positioning jig with the female screw in the state where the jig divided body is closed. Therefore, it takes a similar time to screw the metal shell into the positioning jig with the female screw. However, in the present invention, since the metal shell can be separated from the female screw positioning jig after indexing the position for attaching the ground electrode, as in the invention of claim 1, since the jig divided body can be opened, The separation is possible without rotation. Therefore, the time required for the separation can be shortened as compared with the prior art. Further, in the first aspect, when the jig divided body is closed, there is a possibility that the two threads of the screw and the mounting screw of the metal shell do not mesh smoothly or collide with each other. Therefore, in such a case, it is necessary to adjust so that the speed | rate which closes a jig | tool division | segmentation body may become slow, and to make it mesh | engage (screwing) so that both threads may become familiar in the process of closing it. Thus, in the first aspect of the invention, it may be necessary to adjust the speed at which the jig divided body is closed. On the other hand, in the invention of claim 2, there is no such problem, and the time required for separating the metal shell from the female jig positioning jig after indexing the position for attaching the ground electrode can be surely shortened. There is.

  According to the jig divided body according to the invention of claim 3, the positioning guide for positioning the mounting screw of the metal shell coaxially need not be prepared or installed as a separate part, and can be positioned. Or screwing starts smoothly.

  In the invention of claim 4, since the ground electrode is welded in the state where the position for attaching the ground electrode is indexed, that is, in the state where the metal shell is screwed into the positioning jig with the female thread, the welding process is separately performed. It becomes unnecessary to send. That is, since welding can be performed without requiring feeding to the welding process or repositioning in welding, an effect of simplifying the process can be obtained. When the metal fitting is screwed into the screw ring and the position for attaching the ground electrode is determined as in the conventional manufacturing method, the ground electrode cannot normally be welded in the screwed state as described above. . If it does so, before screwing out and separating, it is necessary to delete or excise the part which inhibits screwing, such as a deformation part and a bulging part by welding sagging, by grinding. On the other hand, in the present invention, when the metal shell is separated from the female jig positioning jig, the jig divided body is opened and separated, so it is possible to freely decide when to delete it. Thus, in the present invention, since the ground electrode can be welded even before separation, the degree of freedom in the process is increased.

  Although the number (number of divisions) of the jig divided bodies in the present invention is not particularly limited, it is preferable to divide into two as in the invention described in claim 5 without incurring the complexity of the structure. In addition, the jig divided body is a positioning jig with a female screw having a screw (female screw) when it is closed, and this female screw is arranged around its axis, that is, in the entire circumferential direction. It is not always necessary that the screws are continuous. Therefore, considering the high accuracy of the screw in the positioning jig with a female screw and the high cost of its formation and its wear, the female screw is provided only in at least one of the plurality of jig divided bodies. It may be formed.

  The embodiment which actualized the manufacturing method of the spark plug based on this invention is described in detail. First, the spark plug manufactured by this manufacturing method is demonstrated based on FIG. However, the spark plug 1 manufactured in this embodiment and the metal shell 3 that is a component of the spark plug 1 are the same as those conventionally known and have been partially described in the above, and will be appropriately omitted. I will briefly explain it. FIG. 1 is a half sectional view showing a schematic configuration of the spark plug.

  As shown in FIG. 1, the spark plug 1 includes a metal shell 3 having a cylindrical shape with a reduced diameter and a ground electrode 33 attached to a tip 31, and a packing 11, an O-ring 13, and a talc 14 inside the metal shell 3. Is provided with an insulator 5 fixed thereto. The insulator 5 has a cylindrical shape with a different diameter, and a center electrode 7 is fixed by a seal glass 16 so as to protrude from the tip (lower end in FIG. 1) in the central shaft hole. The terminal electrode 19 is fixed via the sealing glass 16 via the resistor 17. In such a spark plug 1, an insulator 5 having a center electrode 7 or the like fixed in a shaft hole is inserted inside the metal shell 3, and a tip-facing surface of a portion near the tip of the insulator 5 is disposed on the metal shell 3. The rear end of the fixing flange 9 on the outer periphery of the intermediate portion of the insulator 5 is pressed against the locking flange 36 formed on the inner peripheral surface of the inner tip portion (small diameter cylindrical portion 3a) via the packing 11. Further, the O-ring 13 and the talc 14 are interposed between the inside of the large-diameter cylindrical portion 3b of the metal shell 3, and the caulking thin cylindrical portion 38 at the rear end of the metal shell 3 is bent inward and toward the front end side. It is assembled by compressing and plastically deforming.

  Thus, such a spark plug 1 has a plug hole in a cylinder head of an engine (not shown) via a mounting screw 35 formed on the outer peripheral surface of the small-diameter cylindrical portion 3a near the tip of the metal shell 3 constituting the spark plug 1. Installed by screwing into (screw hole). In this screwing, the tool is screwed into the polygonal portion 40 for screwing formed on the outer peripheral surface of the large-diameter cylindrical portion 3b near the rear end of the metal shell 3. In this screw-in mounting, the tip-facing surface of the mounting flange 42 provided on the outer periphery of the tip of the large-diameter cylindrical portion 3b is pressed against the seat surface of the plug hole via a gasket (seal washer) not shown. It is set to be screwed in a predetermined amount. Note that the thin cylindrical portion 41 between the mounting flange 42 and the polygonal portion 40 in the large-diameter cylindrical portion 3b is deformed in a curved shape in the cross section. This is to ensure sealing-like fixing. Incidentally, the metal shell 3 is not deformed before being assembled as the spark plug 1 (see FIG. 3).

  Now, the manufacturing process of the metal shell 3 which is a component part of such a spark plug 1 will be described. Such a metal shell 3 uses, for example, a low-carbon steel round bar piece as a starting material (raw material), a plurality of cold forging processes, machining, and screw formation (rolling) on the outer peripheral surface of the small-diameter cylindrical portion 3a. 2), the work in progress before the ground electrode is attached (in this specification, including such work in progress is simply referred to as the metal shell 3) as shown in FIG. In FIG. 2 and subsequent figures, the metal shell 3 is illustrated with its tip 31 facing upward. After that, as shown in FIG. 3, a ground electrode (material) 33 is attached to the tip 31 of such a metal shell 3 by welding, and it has a predetermined shape as shown by a chain line in the figure. By being bent, it is completed as a part except for surface treatment. Thus, the ground electrode 33 is attached to the tip 31 of the metal shell 3 before the ground electrode is attached by screwing the metal shell 3 from the tip 31 side into a positioning jig with a female screw described below with a predetermined torque. After screwing, a predetermined position corresponding to a reference position set in advance around the axis G of the screw in the female jig positioning jig out of the tip 31 of the metal shell 3 is indexed as the ground electrode mounting position. The ground electrode 33 is attached to the ground electrode attachment position by welding. The details of this embodiment are as follows.

  FIGS. 4A and 4B are a plan view and a cross-sectional view showing a simplified configuration of the positioning jig 101 with a female screw used in this embodiment. 4 has a predetermined screw 103 (also referred to as a model screw) modeled on a female screw of a plug pole of a cylinder head to which a spark plug is attached, for example, a cuboid as a whole. It has a block shape. However, the positioning jig 101 with a female screw is divided into two by a plane passing through the axis G of the model screw 103, and is constituted by, for example, two jig divided bodies 101a and 101a. In this embodiment, the model screw 103 formed on the inner surface of the positioning jig 101 with a female screw, that is, on the surface near the axis G of the jig divided body 101a, is given only at the upper end portion as shown in the figure. The inner surface of the model screw 103 below the lower end 103a in the drawing (on the side of the screw-in port into which the metal shell 3 is screwed) has a diameter of a valley of the model screw 103 or a slightly larger diameter than that. Is formed. The cylindrical surface 105 surrounds the mounting screw 35 near the tip 31 of the metal shell 3 in a state where the two jig divided bodies 101a are closed, and coaxially arranges them inside the jig divided body 101a. A positioning guide 105 (hereinafter also referred to as a cylindrical surface 105) that can be positioned is formed. Further, for example, a fixed position around the axis G of the screw 103 on the upper surface 107 of the jig divided body 101a (right side in FIG. 4) constituting the positioning jig 101 with a female screw is a mark indicating a reference position (in the figure, a triangular mark). Hereinafter, the reference position 108 is provided by engraving or the like. In addition, the two jig division bodies 101a are set to be closed through a slight gap K in such a manner that a plurality of stoppers 109 provided on one closing surface are brought into contact with the other closing surface.

  As shown in FIG. 5, each jig divided body 101 a constituting the positioning jig 101 with the female screw is arranged on the linear track 201 via the linear motion bearing 205 and the cage 206 so as to sandwich the axis G. The two jig divided bodies 101a are driven and controlled by a driving means such as a cylinder (not shown) so as to slide in the arrow direction (left and right in FIG. 5) and close (close) or open (separate). It is configured. And when the two jig | tool division bodies 101a close, such a positioning jig | tool 101 with a female screw turns into a positioning jig | tool with a female screw which has the model screw 103 in an internal peripheral surface by them. Then, the metal shell 3 can be screwed upward from the tip 31 thereof via the mounting screw 35 to the model screw 103, and the metal shell 3 screwed into the screw 103 when the screw is opened is screwed. The jig division body 101 a slides on the linear track 201 via the linear motion bearing 205 so that it can be separated in the direction of the axis G.

  In this embodiment, the linear track 201 is fixed to the lower surface of the mounting plate 210, and the mounting plate 210 is attached to the frame 221 fixed to the upper part of the positioning device for mounting the ground electrode via, for example, a compression coil spring 225. When a compressive force is applied upward to the positioning jig 101 with a female screw, such as when the metal shell 3 is screwed, the compression coil spring 225 is compressed and moves upward by an appropriate amount. Is set to be absorbed.

  Thus, in this embodiment, the metal shell 3 is arranged as follows in a state where the plurality of jig divided bodies 101a are opened in the radial direction of the screw 103, and then screwed and attached to the ground electrode of the tip 31. The position for use is determined. That is, in this embodiment, as shown in FIG. 5, the mounting screw 35 of the metal shell 3 is surrounded by the jig divided body 101 a when viewed from the direction of the axis G of the model screw 103, and the tip 31 faces upward. Position coaxially. In FIG. 5, the positioning and holding is performed by moving the positioning holder 301 with the metal shell 3 fitted into the large-diameter cylindrical portion 3 b inside the annular positioning holder 301. ing.

  Next, as shown in FIG. 6, the metallic shell 3 is moved along the axis G by a predetermined stroke. In this upward movement, for example, the tip of the mounting screw 35 is set so that when the jig divided body 101a is closed, the metal shell 3 is not screwed into the positioning jig 101 with the female screw for several threads S. The metal shell 3 is moved up a predetermined stroke along the axis G so that several screws on the 31 side are in a positional relationship in which the screw is engaged with the model screw 103. In this example, the metal shell 3 is moved upward by a predetermined stroke in the state where the metal shell 3 is held coaxially. In this example, the mandrel 401 provided coaxially under the positioning holder 301 is shown in the figure. The collet chuck portion 403 at the tip of the metal shell 3 passes through the positioning holder 301 and is fitted into the large-diameter cylindrical portion 3b of the metal shell 3, and is further moved upward by a predetermined stroke.

  Next, after the metal shell 3 is moved up by a predetermined stroke along the axis G in this way, the jig divided body 101a is driven and closed as shown in FIG. At this time, with respect to the model screw 103 of the positioning jig 101 with the female screw, the metal shell 3 is in an incomplete screwed state, leaving several mounting screws 35 for S. Then, as shown in FIG. 8, such a metal shell 3 is screwed with a predetermined torque from a screwing incomplete state to a completed state. In this example, the mounting flange 42 of the metal shell 3 is set to be screwed in until it contacts the lower surface 110 of the female-threaded positioning jig 101 (the lower surface of the jig divided body 101a).

  As shown in FIG. 9, the metal shell 3 screwed in this way has a ground electrode mounting position 31a to which the ground electrode 33 at the tip 31 is to be mounted on the upper surface of the jig divided body 101a (positioning jig with female screw). It is determined as a position (a position in the circumferential direction) that matches the reference position 108 provided on the upper surface (101). In this embodiment, the screwing is movable in the radial direction within the window-like openings provided, for example, in three circumferential directions on the outer peripheral surface of the collet chuck portion 403 at the tip of the cylindrical mandrel 401. The fixing piece 405 disposed so as to protrude slightly outward from the outer peripheral surface is pushed outward, the metal shell 3 is chucked on the inner surface of the large-diameter cylindrical portion 3b, and the mandrel 401 is moved in this state. By rotating around the axis G with a predetermined torque. The fixing piece 405 is pushed out by moving the core rod 412 having a tapered portion 411 at the tip and performing the wedge action by the taper.

  Thus, after the position (circumferential position) matching the reference position 108 of the positioning jig 101 with the female screw in the tip 31 of the metal shell 3 is determined as the ground electrode mounting position 31a, two positions are determined. The state before the jig split body 101a is closed, that is, the open state as shown in FIG. 6, is separated from the positioning jig 101 with the female screw. In this case, in this embodiment, after opening the two jig divided bodies 101a, the core rod 412 in the mandrel 401 is moved downward, the collet chuck portion 403 is used as an unchuck, and the mandrel 401 is moved down without rotating. . Thus, the metal shell 3 is separated from the female-threaded positioning jig 101 without changing the position around the axis G so that the ground electrode mounting position 31a at the tip 31 of the metal shell 3 does not change.

  In such a separation, in this embodiment, as in the state before screwing shown in FIG. 5, the metal shell 3 is fitted inside the positioning holder 301 in which the large-diameter cylindrical portion 3 b forms an annular shape. . Thus, the metal shell 3 from which the ground electrode mounting position 31a has been indexed is sent to the welding station together with the positioning holder 301 in that state, and the ground electrode (the electrode forming the ground electrode) is sent to the ground electrode mounting position 31a. Bar) 33 is welded, and then welding sag is removed. By doing so, as shown in FIG. 3, the metal shell 3 in which the ground electrode 33 is attached to the desired ground electrode attachment position 31a is obtained. Then, by bending the ground electrode 33 into a predetermined shape, the metallic shell 3 is completed as a part except for the surface treatment. The spark plug 1 is obtained by using the metal shell 3 manufactured in this way and assembling the insulator 5 and the like on the inside as described above.

  In this embodiment, the time required for screwing the metal shell 3 into the positioning jig 101 with the female screw for indexing the ground electrode mounting position 31a to which the ground electrode 33 is to be mounted is an appropriate number of screws even before the screwing. Since the mountain is shortened by the screwed state, the manufacturing efficiency of the metal shell 3 can be improved by the shortening, and as a result, the manufacturing efficiency of the spark plug can be improved. In addition, in this example, even when the ground electrode mounting position 31a is separated after indexing, it can be taken out by opening the jig divided body 101a forming the positioning jig 101 with the female screw without rotating the metal shell 3 in the reverse direction. Further, the production efficiency can be improved.

  Now, another example will be described with reference to FIG. However, since the thing of this example is fundamentally in common with the above-mentioned form, only the difference is demonstrated. That is, in the manufacturing method, in the state where the two jig divided bodies 101a are opened in the radial direction of the screw, the metal shell 3 is positioned so as to be surrounded by the jig divided body 101a when viewed from the screw axis G direction. Moreover, when the jig divided body 101a is closed, the metal shell 3 is arranged so as to be in a positional relationship in which it is screwed into the female jig positioning jig in an incomplete state. The jig divided body 101a is closed, and the metal shell 3 is screwed with a predetermined torque until the metal fitting 3 is screwed from the incomplete state to the complete state. However, in this example, only this point is different. Specifically, it is as follows.

  That is, as shown in FIG. 10, the metal shell 3 is coaxial with the axis G of the two screws with respect to the positioning jig 101 with the female screw that is not in the opened state but in the closed state. Position it so that it has a shape. 11, the metal shell 3 is chucked and attached to the tip (collet chuck portion) 403 of the mandrel 401, and the mandrel 401 is moved upward to attach the metal shell 3 in the same manner as described above. The part close to the tip 31 of the screw 35 is inserted into a cylindrical surface 105 serving as a positioning guide below the model screw 103 of the positioning jig 101 with a female screw. Then, the mandrel 401 is moved upward while rotating at a predetermined torque, and the metal shell 3 is screwed into the positioning jig 101 with a female screw.

  Then, as shown in FIGS. 8 and 9, as shown in FIGS. 8 and 9, due to the screwing, the position that matches the reference position 108 of the female-threaded positioning jig 101 on the front end 31 of the metal shell 3 is grounded. It is indexed as an electrode mounting position 31a. Thereafter, in the same manner as in the above embodiment, the indexed metallic shell 3 may be separated from the female-threaded positioning jig 101 and sent to the welding process.

  In the form shown in FIG. 5 to FIG. 9, there is a problem that both screws (threads) 35 and 103 may collide with each other when the jig divided body 101a is closed due to the method. Such a problem does not occur in this example manufacturing method. That is, although the time required for screwing is the same as that of the prior art, the time for separating the metal shell 3 from the positioning jig 101 with the female thread after the indexing of the position for attaching the ground electrode can be surely shortened. In this example, since the cylindrical surface 105 provided under the model screw 103 of the positioning jig 101 with a female screw forms the guide 105, the screwing start can be facilitated without providing a separate or independent guide. Figured. In this embodiment, the diameter (inner diameter) of the cylindrical surface 105 formed in a state where the two jig divided bodies 101a are closed is set to be slightly larger than the outer diameter of the mounting screw 35 of the metal shell 3. The mounting screw 35 is inserted into the gap fitting state.

  In each of the above examples, the position of the ground electrode mounting position is indexed and the ground electrode is welded to that position at different stations. However, in each of the above examples, the metal shell 3 is a positioning jig with a female screw. After screwing into 101 and indexing the ground electrode mounting position 31a, before separating it from the female threaded positioning jig 101, that is, the metal shell 3 is screwed into the female threaded positioning jig 101 to mount the ground electrode. The ground electrode 33 may be welded to the ground electrode mounting position 31a at the tip 31 of the metal shell 3 in the state where the position 31a is indexed. That is, in this way, if welding is performed in the step of determining the ground electrode mounting position, the process can be simplified, that is, the need for a station for independent welding can be eliminated. In the present invention, the metal shell 3 is separated from the female screw positioning jig 101 by opening and separating the jig divided body 101a. Since there is no problem in what is to be done, there is a degree of freedom in the process that the welding process can be performed in the indexing process of the position for attaching the ground electrode.

  The present invention is not limited to the contents described above, and can be embodied with appropriate modifications without departing from the scope of the invention. As described above, the number of the jig divided bodies 101a may be divided into three or more. In addition, the model screw of the positioning jig with a female screw may be a screw that forms a screw (female screw) when the jig divided body is closed, but this screw is a complete screw that is continuous in the circumferential direction. It is obvious from the configuration of the positioning jig with a female screw shown in FIG. 4 that it is not always necessary. For example, as described above, when the jig divided body is divided into two parts, as shown as the positioning jig 501 with a female screw shown in FIG. 12, one of the jig divided bodies 101a (FIG. 12 (left), the inner surface of the other jig divided body 101a (right in FIG. 12) may be a cylindrical surface 105 over the entire length, assuming that there is a screw (model screw) 103 only on the inner surface. In FIG. 12, the same components as those in FIG. 4 are denoted by the same reference numerals. By doing so, the cost of forming the positioning screw 501 with the female screw is expected to be reduced as much as the cost of forming the model screw is reduced. Further, when the jig divided body is divided into four parts, a model screw may be provided on the inner peripheral surface of the two jig divided bodies that are arranged so as to jump one by one in the circumferential direction. Further, it is obvious that the number of thread of the model screw may be an appropriate number, and can be set regardless of the number of threads of the metal shell.

The schematic structure front half sectional view of the spark plug manufactured with the manufacturing method of this invention. Sectional drawing of the work-in-process of the metal shell for spark plugs manufactured with the manufacturing method of this invention. The front view of the metal shell for spark plugs manufactured with the manufacturing method of this invention. It is a figure explaining the positioning jig with a female screw used with the manufacturing method of this invention, Comprising: A is a schematic structure top view, B is sectional drawing. The principal part sectional drawing of the positioning apparatus for earthing electrode attachment provided with the jig | tool division body which makes the positioning jig with a female screw. FIG. 6 is a diagram for explaining a state in which the metal shell is moved up and inserted into a positioning jig with a female screw in FIG. 5. The figure explaining the state which closed the jig division body in FIG. The figure explaining the state which screwed the metal shell in the positioning jig with a female screw in FIG. The top view of FIG. It is a figure explaining another example of the manufacturing method of this invention, Comprising: The schematic structure sectional drawing for demonstrating the positioning jig with a female screw which closed the jig | tool division body, and the main metal fitting arrange | positioned coaxially with it. The figure explaining the state which inserted the metal shell in the positioning jig with a female screw in FIG. It is a figure explaining the positioning jig with a female screw used for another example of the manufacturing method of this invention, Comprising: A is a schematic structure top view, B is sectional drawing.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Spark plug 3 Main metal fitting 31 Tip 31a of main metal fitting Ground electrode attachment position 35 of main metal fitting 35 Fixing screw 101 of main metal fitting 101 Positioning jig with female screw 101a Jig division 103 Screw 105 in positioning jig with female screw With female screw Positioning guide for the positioning jig (cylindrical surface)
108 Mark indicating the reference position in the positioning jig with female thread
G Screw axis

Claims (6)

A metal shell, which is a spark plug component and has a mounting screw formed on the outer peripheral surface, is screwed into a positioning jig with a female screw from the front end side thereof with a predetermined torque. In a spark plug manufacturing method, comprising: indexing a predetermined position corresponding to a reference position preset around a screw axis in a tool as a ground electrode mounting position, and attaching the ground electrode to the ground electrode mounting position;
The female screw positioning jig is composed of a jig divided body divided into a plurality when viewed from the axial direction of the screw, and each jig divided body can be opened and closed in the radial direction of the screw and closed. Sometimes we have to configure a positioning jig with a female thread,
In the state where the plurality of jig divisions are opened,
The metal shell is held at a position where the mounting screw is surrounded by the plurality of jig divisions when viewed from the axial direction, and the metal fittings are closed when the plurality of jig divisions are closed. The mounting screw is in a state where it has not been screwed into the positioning jig with female screw, and at least a part of its thread is in a positional relationship to be screwed,
After this arrangement, the plurality of jig divisions are closed, and then the metal shell is screwed in with a predetermined torque from the unscrewed incomplete state to the completed state, and the female screw is attached to the tip of the metal shell. Indexing a predetermined position corresponding to the reference position of the positioning jig as a ground electrode mounting position,
Thereafter, the plurality of jig divisions are opened to separate the metal shell from which the position for attaching the ground electrode is indexed from the positioning jig with the female thread,
Thereafter, a method of manufacturing a spark plug, comprising a step of attaching a ground electrode to the ground electrode mounting position at the tip of the metal shell. A metal shell, which is a spark plug component and has a mounting screw formed on the outer peripheral surface, is screwed into a positioning jig with a female screw from the front end side thereof with a predetermined torque. In a spark plug manufacturing method, comprising: indexing a predetermined position corresponding to a reference position preset around a screw axis in a tool as a ground electrode mounting position, and attaching the ground electrode to the ground electrode mounting position;
The female screw positioning jig is composed of a jig divided body divided into a plurality when viewed from the axial direction of the screw, and each jig divided body can be opened and closed in the radial direction of the screw and closed. Sometimes we have to configure a positioning jig with a female thread,
To the positioning jig with a female screw in the state where the plurality of jig divisions are closed,
Screwing the metal shell with a predetermined torque until the screwing is completed, and indexing a predetermined position corresponding to the reference position of the positioning jig with the female screw among the tips of the metal shell,
Thereafter, the plurality of jig divisions are opened to separate the metal shell from which the position for attaching the ground electrode is indexed from the positioning jig with the female thread,
Thereafter, a method of manufacturing a spark plug, comprising a step of attaching a ground electrode to the ground electrode mounting position at the tip of the metal shell.   3. The jig divided body according to claim 1 or 2, wherein in the closed state, the jig divided body surrounds at least a portion near the tip of the metal shell on the screwing side into which the metal shell is screwed, and its mounting screw and female screw. A manufacturing method of a metal shell for a spark plug, comprising: a positioning guide for coaxially positioning an axis of a screw of an attached positioning jig. In Claims 1-3,
Indexing a predetermined position corresponding to the reference position of the female threaded positioning jig among the tips of the metal shell as a ground electrode mounting position,
Thereafter, the plurality of jig divisions are opened to separate the metal shell from which the position for attaching the ground electrode is indexed from the positioning jig with the female thread,
Thereafter, a ground electrode is attached to the ground electrode mounting position at the tip of the metal shell,
Instead,
Indexing a predetermined position corresponding to the reference position of the female threaded positioning jig among the tips of the metal shell as a ground electrode mounting position,
Under the indexed state, a ground electrode is attached to the ground electrode attachment position at the tip of the metal shell,
Thereafter, a plurality of the jig divided bodies are opened, and the metal shell, to which the ground electrode is attached, is separated from the positioning jig with a female screw.   The plurality of jig division bodies constituting the female screw positioning jig are divided into two when viewed from the axial direction of the screw, according to any one of claims 1 to 4. The manufacturing method of the spark plug of description.   The spark plug manufacturing method according to any one of claims 1 to 5, wherein a screw is formed on one or more of the plurality of jig divided bodies.

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