JPH0992441A - Manufacture of side electrode for spark plug - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent formation of bridges in and unevenly curved heights of side electrodes and to prevent the electrode surfaces from being torn and flawed by manufacturing the side electrodes through the processes of applying oil to the electrode surfaces, curving the surfaces, and removing the oil. SOLUTION: Two side electrodes 11 welded to the end face 4a of a main metal fitting 4 have their ends dipped in a sponge 14 containing a low-viscosity lubricating oil so as to apply the lubricating oil to the ends by a certain amount. Next, using an automatic press molding machine 20 provided with a bending die 21 having a molding surface whose configuration is reverse with respect to a predetermined curved configuration of the electrode 11 and a bending punch 23, the end of each electrode 11 is curved into an approximately L shape as it is pointed to the axis of the metal fitting 4. Then using an automatic press molding machine 30 provided with a punch 33 for punching the ends of the two electrodes 11 from the inside of the metal fitting 4 and a die 31, each end is punched into an approximately bowl shape to form discharge end faces. The dimensional accuracy of the end faces is thus enhanced, and the oil applied can be removed with good productivity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a side electrode for a spark plug, in which a side electrode forming a discharge gap with a center electrode is joined to a tip surface of a metal shell, The present invention relates to a method for manufacturing a lateral electrode for a multipolar spark plug, which is formed by joining a multipolar lateral electrode having two or more electrodes to a tip surface of a metal shell.

[0002]

2. Description of the Related Art Conventionally, the front end surface of a tubular metal shell and two
The electrode and the electrode on the side of the electrode are joined by resistance welding, and after plating, the electrode of the electrode on the side of the electrode is pressed against the curved surface of the bending die by an automatic press molding machine. For bending the electrode into a substantially L shape, and performing a punching process for punching the tip of the two-electrode side electrode to form a discharge end face. There is known a method for manufacturing a polar side electrode.

[0003]

However, in the conventional method for manufacturing the bipolar electrode for the multipolar spark plug, the frictional resistance between the bipolar electrode and the bending die is very large in the bending step. As indicated by the arrow in 6, there is a possibility that the tip portion of the bipolar side electrode 101 may curl up.
If this amount of roll-up is large, as shown in FIG.
Even if a two-dot chain line portion (punched portion 102) in the drawing is removed by performing a punching process of punching the tip of the pole-side electrode 101, the burred portion 103 remains.

Further, as shown in FIG. 8, the center electrode 10 is placed in the metallic shell 104 to which the bipolar electrode 101 is joined.
When the insulator 106 having the built-in 5 is assembled by caulking or the like, the remaining portion of the burr (the portion that cannot be removed by punching) rises and peels off in the form of a mustache, and adheres to the center electrode 105 to form the bridge 107. Is occurring.

[0005] Here, when the oil adheres to the jig or the two-electrode side electrode due to some cause during bending, the friction resistance between the two-electrode side electrode and the bending die fluctuates, so that the two-electrode side electrode. The bending height of each of them becomes uneven. For example, the frictional resistance changes due to the oil content of the hand and the bending height of the bipolar side electrode changes even by simply touching the jig or the bipolar side electrode with the hand. Therefore, it is necessary to degrease the jig with a cleaning liquid when replacing the jig, and assemble the jig without touching it. If there is a problem with the supply of the metal shell in the supply section of the automatic press molding machine (for example, the metal shell is caught), 2
It was necessary to supply the metal shell to a predetermined place without touching the pole side electrodes, which was a factor of poor workability and reduced productivity.

If oil adheres to the metal shell for some reason, the caulking conditions change during the subsequent step, that is, the step of assembling the insulator by caulking the metal shell, and the tightening force of the insulator by the metal shell changes. This causes a problem that the insulator cannot be properly assembled to the metal shell due to the change. Therefore, when cleaning the oil attached to the metal shell, if many metal shells are attempted to be cleaned together, the metal shell and the two-electrode side electrodes joined thereto collide with each other, and The problem of being deformed arises. For this reason, the lubricating oil for reducing the frictional resistance between the bipolar side electrode and the bending die has not been applied to the bipolar side electrode.

Further, it is remarkable in the conventional method for manufacturing the bipolar two-side electrode for the multipolar spark plug, particularly in the case of a material having a relatively high hardness such as Inconel (trademark) material. When the bipolar side electrode 101 is bent into a substantially L-shape, a bending die causes peeling scratches 108 on the side surface of the bipolar side electrode 101 as shown in FIG. There is.

An object of the present invention is to reduce the frictional resistance between the side electrode and the bending die to suppress the amount of curling up, thereby preventing the formation of a bridge between the center electrode and the side electrode. It is to provide a manufacturing method of a lateral electrode for use. Another object of the present invention is to provide a method of manufacturing a side electrode for a spark plug, which can prevent unevenness in bending height of the side electrode. Furthermore, even when a material having a relatively high hardness such as Inconel material is used as the electrode base material of the side electrode, it is possible to prevent the formation of scratches on the surface of the side electrode. It is to provide a manufacturing method of a lateral electrode for use.

[0009]

According to a first aspect of the present invention, there is provided a method of manufacturing a lateral electrode, wherein the lateral electrode is joined to the front end surface of the metal shell for fixing the insulator holding the central electrode in a state of being abutted against each other. An oil application step of applying oil to reduce frictional resistance on the surface of the side electrode, and pressing the surface of the side electrode against the curved surface of the bending mold to form the side electrode into a predetermined bent shape. A technical means including a bending step for removing the oil and an oil removing step for removing the oil applied to the surface of the side electrode is adopted. Also, two or more side electrodes may be used as the side electrodes.

According to a second aspect of the present invention, there is provided a method of manufacturing a side electrode, which is joined in a state of abutting against a front end surface of a metal shell for fixing an insulator holding a center electrode, wherein the front end portion of the side electrode is provided. An oil applying step of applying oil for reducing frictional resistance, and a bending step of pressing the tip end surface of the side electrode against a curved surface of a bending die to form the side electrode into a predetermined bending shape. , A punching step of punching the tip of the side electrode. Also, two or more side electrodes may be used as the side electrodes.

[0011]

According to the invention as set forth in claim 1, the oil is applied to the surface of the side electrode to be joined in a state of being abutted against the tip surface of the metal shell, and then the bending step is performed, whereby Since the frictional resistance between the side electrode and the bending die becomes small, the amount of curling of the tip portion of the side electrode becomes small. Thereby, even if the metal shell, the insulator and the center electrode are combined, it is possible to suppress the formation of a bridge between the side electrode and the center electrode. Then, by applying a certain amount of oil to the surface of the side electrode in the oil applying step,
Since the variation in the frictional resistance between the side electrode and the bending die becomes small, it is possible to suppress the variation in the bending height and the bending shape of the side electrode in the bending process.

By removing the oil applied to the side electrodes in the removing step, the tightening force does not change when the metal shell is tightened on the outer circumference of the insulator. what if,
When a supply failure of the metal shell occurs in the supply section of the automatic press molding machine, even if the side electrodes are touched by hand, the oil content can be removed by the oil removal step, so workability is improved and productivity can be improved.

According to the second aspect of the present invention, by applying oil to the tip of the side electrode to be joined in a state of abutting against the tip surface of the metal shell, a bending step is performed to form the side electrode. Since the frictional resistance with the bending die is reduced, the amount of curling up of the tip portion of the side electrode is reduced. This allows
Even if the metal shell, the insulator and the center electrode are combined,
It is possible to suppress the formation of a bridge between the side electrode and the center electrode. Then, by applying a fixed amount of oil to the tip end surface of the side electrode in the oil applying step, fluctuations in the friction resistance between the side electrode and the bending die are reduced, so that the bending height and the bending height of the side electrode in the bending step are reduced. Variation in bending shape can be suppressed.

By punching out the tip of the side electrode in the punching step, the oil applied to the tip of the side electrode is removed, so that the tightening force when tightening the metal shell on the outer circumference of the insulator is improved. It does not change. Since the metal shell is not washed as an oil removing operation, the side electrodes can be prevented from being deformed by preventing the side electrodes from colliding with each other.

[0015]

【Example】

[Structure of Embodiment] Next, a method of manufacturing the side electrode for a spark plug of the present invention will be described based on the embodiment shown in FIGS. FIG. 1 is a diagram showing a method for manufacturing a two-pole side electrode, FIG. 2 is a diagram showing a two-pole spark plug for an internal combustion engine, FIG. 3 is a diagram showing a metal shell thereof, and FIGS. FIG. 4 is a diagram showing a tip portion of a metal shell.

The two-pole spark plug 1 for an internal combustion engine produces a strong spark in the spark discharge gap 12 accurately and surely at a predetermined ignition timing, and triggers the combustion of the air-fuel mixture sucked into the combustion chamber of the internal combustion engine. A spark plug for an internal combustion engine to be made, which includes a center electrode 2 to which a high voltage is applied, and the center electrode 2
And a cylindrical metal shell 4 for holding and fixing the insulator 3. The center electrode 2 is a composite electrode material in which copper or the like having excellent thermal conductivity is enclosed as a nickel alloy core material. The insulator 3 is an insulator made of an electrically insulating member (eg, alumina ceramics).

Next, the structure of the metal shell 4 will be described in detail with reference to FIG. A hexagonal portion 5 in the shape of a bolt head that engages with a tool (not shown) is formed on the outer periphery of the metal shell 4 on the rear end side with respect to the central portion. A male screw portion 6 for screwing into an engine block (not shown) of the internal combustion engine is formed on the outer periphery of the metal shell 4 closer to the tip side than the central portion.
An annular collar-shaped portion (body) 7 having an outer diameter smaller than that of the hexagonal portion 5 is formed between the hexagonal portion 5 and the male screw portion 6, that is, in the central portion of the metal shell 4.

Inside the metal shell 4, the insulator 3
Is formed with an axial hole 8 for inserting. A taper-shaped locking portion 9 for locking the insulator 3 projects inward in the axial hole 8. Reference numeral 10 denotes an annular caulking portion for locking the insulator 3 by caulking, which is integrally formed with the rear end portion of the metal shell 4.

The leading end surface 4a of the metal shell 4 is, as shown in FIGS. 2 to 5, two sides bent in a substantially L shape toward the axis of the metal shell 4 in the middle. The side electrodes 11 are joined together by a joining means such as resistance welding in a state where they are butted. The two side electrodes 11 are a multi-pole (two-pole) outer electrode, a multi-pole (two-pole) ground electrode, a multi-pole (two-pole) side electrode, and two.
It is also called a pole facing outer electrode, a pole facing ground electrode, a pole facing side electrode, and a spark plug electrode provided on the ground (ground) side. Discharge end faces 13 are formed at the tips of the two side electrodes 11 to form a spark discharge gap 12 having a predetermined gap length with the tips of the center electrodes 2.

As shown in FIG. 4, the two side electrodes 11 are formed so that they have the same predetermined bending height h. Further, as shown in FIG. 5, the two side electrodes 11 have a predetermined punching between the discharge end faces 13 to form a spark discharge gap 12 coaxially with the outer periphery of the center electrode 2. It is formed to have a diameter φ.

[Manufacturing Method of Embodiment] Next, a manufacturing method of the two lateral electrodes 11 will be briefly described with reference to FIGS. 1 to 5.

First, a metal shell 4 is obtained by forming a conductive metal material such as low carbon steel containing iron with a carbon content of several% or less into a predetermined shape by cold extrusion. Note that the metal shell 4 may be used by cutting a cylindrical or hexagonal bar without cutting the metal shell 4 by cold extrusion.

Next, the metal shell 4 is thread-rolled. That is, a round die or a flat die having a chevron shape of the male screw portion 6 (neither is shown) is pressed against the outer periphery of the metal shell 4 and rolled, so that the outer periphery of the metal shell 4 closer to the tip side than the flange portion 7 is located. The male screw portion 6 including a plurality of peaks and a plurality of valleys is formed. The length of the male screw portion 6 is determined by the thickness of the cylinder head of the internal combustion engine and the like.

Next, two side electrodes 11 made of nickel alloy mainly composed of nickel are joined to the opposite positions on the front end surface 4a of the metal shell 4 by using a joining means such as resistance welding. . As a base material of the two lateral electrodes 11, a nickel alloy in which Cr, Mn, and Si are added to nickel, Inconel (Cr-Fe-Ni) is used, and thermal conductivity as a core material in the nickel alloy is used. Alternatively, a material in which copper or the like having excellent conductivity is sealed may be used. Here, the order of joining the two side electrodes 11 and thread rolling may be reversed.

Next, the metal shell 4 is pickled. That is, the metal shell 4 is dipped in hydrochloric acid having a capacity of 10% to 20% to remove rust, oxides, chips generated by cutting, etc., and washed with water. The two lateral electrodes 11 are plated with zinc and chromated (see FIG. 1A).

FIG. 1 (b) is a diagram showing an oil application process for the two side electrodes 11. The tip portions of the two side electrodes 11 welded to the tip surface 4a of the metal shell 4 are attached to a sponge 14 containing a low-viscosity lubricating oil to attach the two side electrodes 1 to each other.
Apply a fixed amount of lubricating oil only to the tip surface of No. 1 [Fig. 1 (b)]
reference〕. In addition to this, a certain amount of lubricating oil may be applied to only the tip surfaces of the two lateral electrodes 11 with a brush so that the lubricating oil is soaked in the brush.

FIG. 1C is a view showing a bending process of the two side electrodes 11. The automatic press-molding machine 20 that performs this bending step includes a bending die 21 having a shaping surface having a shape opposite to the predetermined bending shape of the two side electrodes 11, a guide 22 for guiding the metal shell 4 to the bending die 21 side, And a bending punch 23 that moves from the inside to the outside of the metal shell 4 and the like.

The bending punch 23 penetrates the axial hole 8 of the metal shell 4 and presses the two side electrodes 11 against the molding surface of the bending die 21 to plastically deform the two side electrodes 11. . The bending punch 23 is formed in the axial hole 8 of the metal shell 4.
It has a shoulder portion 24 that abuts on the inner locking portion 9 and has a length of a leg portion 25 extending downward from the shoulder portion 24 to form two side electrodes 11.
The bending height (electrode height) of is determined.

Next, two side electrodes 1 coated with lubricating oil
By inserting the metal shell 4 into the guide 22 so that the front end surface of the bending die 21 contacts the molding surface of the bending die 21, the metal shell 4 is inserted from the middle by the front end surface of the leg portion 25 of the bending punch 23.
It is bent in a substantially L-shape toward the axis of (see FIG. 1 (c)). By this bending step, as shown in FIG. 4, the tip surfaces of the two side electrodes 11 are arranged so as to face each other, and the two side electrodes 11 are both formed to have a predetermined bending height h. .

FIG. 1D is a view showing a punching process of the two side electrodes 11. The automatic press molding machine 30 which performs this punching process has a punching die 31 having a discharge hole 34 for discharging the punching scraps 15 punched from the tips of the two side electrodes 11, and the metal shell 4 on the punching die 31 side. It comprises a guide 32 for guiding and a punching punch 33 that moves from the inside to the outside of the metal shell 4. The punching punch 33 punches the tip ends of the two side electrodes 11 of the metal shell 4 into a predetermined shape from the axial hole 8 of the metal shell 4 (see FIG. 1D).

Next, the side electrode 11 of the metallic shell 4 is inserted into the guide 32 so as to come into contact with the upper end surface of the punching die 31, and the two side electrodes 1 are inserted by the tip of the punching punch 33.
As shown in FIG. 5, by punching out the tip end portion of 1 into a substantially bowl shape, the punching diameter φ is obtained at the tip end portions of the two side electrodes 11.
Then, the discharge end surface 13 is formed. Two side electrodes (two-pole side electrodes) 11 are formed into a predetermined substantially L-shape by the above manufacturing process, and are attached to the metal shell 4 in the subsequent assembling process.
The insulator 3 including the center electrode 2 and the like are clamped and fixed to manufacture the two-pole spark plug 1 for an internal combustion engine shown in FIG.

[Effects of the Embodiment] As described above, the two-pole spark plug 1 for an internal combustion engine has the tip portions (bending die) of the two side electrodes (two-pole side electrodes) 11 in the preceding step of the bending step. Since the lubricating oil is applied to the portion (first contacting the molding surface of 21), the two lateral electrodes 11 and the bending die 2 are used in the bending process.
The frictional resistance with 1 becomes small. As a result, since the tip portions of the two side electrodes 11 are prevented from curling up, when the insulator 3 is assembled to the metal shell 4, the bridge between the center electrode 2 and the two side electrodes 11 is bridged. Are not formed.

Even when a metal material made of nickel alloy such as Inconel is used as the electrode base material of the two side electrodes 11, as described above, the two side electrodes 11 and the bending die 21 are connected to each other. Since the frictional resistance of the two side electrodes 11 becomes small, when the two side electrodes 11 are bent into a substantially L shape, the bending die 21 forms peeling scratches on either side surface of the two side electrodes 11. There is no such thing.

Since a fixed amount of lubricating oil is applied to the tips of the two side electrodes 11 in the step before the bending step, 2
Since the frictional resistance between the two lateral electrodes 11 and the bending die 21 is substantially the same each time, it is possible to suppress the variation in the bending shape and the bending height of the two lateral electrodes 11. That is,
Since the accuracy of the bending shape and the bending height of the two side electrodes 11 can be improved, the tips of the two side electrodes 11 are always fixed at a fixed position during the punching process of the two side electrodes 11. Since it can be punched out in a predetermined shape, the two side electrodes 11
The accuracy of the punching diameter φ can be improved.

In the case where a supply failure of the metal shell 4 occurs in the supply section of the automatic press molding machines 20, 30, it is necessary to manually
Even if you touch the tip of the side electrode 11 of the book, the
By punching out the tips of the side electrodes 11 of the book, not only the applied lubricating oil but also the oil component that is erroneously attached is removed from the two side electrodes 11. Therefore, it is not necessary to degrease the jig with the cleaning liquid or to assemble the jig without touching it when the jig is replaced. This allows
The two side electrodes 11 were manufactured with great care, i.e. without touching either of the two side electrodes 11 by hand, but without paying such attention. Since the two side electrodes 11 can be manufactured, the workability is improved and the productivity of the metal shell 4 and the two side electrodes 11 can be improved.

Further, by removing the lubricating oil applied to the two side electrodes 11 in the punching step, it is possible to prevent the occurrence of defects in the subsequent steps. That is, since the lubricating oil is less likely to adhere to the metal shell 4, the caulking conditions do not change during the assembly process of assembling the metal insulator 4 by caulking or the like, and the metal shell 4 tightens the insulator 3. Since the forces are always the same, the insulator 3 can always be correctly assembled in the metal shell 4. Further, since the lubricating oil does not adhere to the metal shell 4, it is not necessary to wash the metal shell 4 and deformation of the metal shell 4 and the two side electrodes 11 can be prevented.

[Modification] In this embodiment, the present invention is applied to the method of manufacturing the side electrode 11 of the two-pole spark plug 1 for an internal combustion engine. However, the present invention is applied to the side electrode of a one-pole spark plug or two-pole. You may apply to the manufacturing method of the above-mentioned multipolar side electrode of a multipolar spark plug. Even if the metal shell 4 is washed instead of the punching step, the two side electrodes 11
Not only may the oil adhering to the entire metal shell 4 be removed.

In this embodiment, the hexagonal portion 5 is used as the metal shell.
The metal shell 4 having a shape smaller than the collar portion 7 was used,
As the metal shell, the metal shell 4 having a shape in which the flange portion 7 is smaller than the hexagonal portion 5 may be used. Further, as the base material of the center electrode 2, a nickel alloy in which Cr, Mn, and Si are added to nickel, Inconel (Cr-Fe-Ni) is used, and platinum, iridium or these is used as the discharge end face of these base materials. A noble metal material such as an alloy may be attached, and the discharge end surface 13 at the tip of the side electrode 11 is not limited to a circular arc surface and may be a flat surface.

[Brief description of drawings]

FIG. 1A to FIG. 1D are process drawings showing a method for manufacturing a bipolar side electrode (Example).

FIG. 2 is a side view showing a two-pole spark plug for an internal combustion engine (embodiment).

FIG. 3 is a cross-sectional view showing a metal shell (Example).

FIG. 4 is an enlarged view showing a front end portion of the metal shell of FIG. 3 (Example).

FIG. 5 is a front view showing a tip portion of the metal shell of FIG. 3 (Example).

6 (a) and 6 (b) are a side view and an enlarged view showing the state in which the bipolar side electrodes are rolled up when oil is not applied.

7 (a) and 7 (b) are side views showing the state in which the bipolar side electrodes are rolled up after the punching step.

8A and 8B are side views showing a bridge state of a spark discharge part.

FIG. 9 is a perspective view showing a state in which a peeling scratch is formed on the bipolar side electrode when oil is not applied.

[Explanation of symbols]

 1 Internal combustion engine 2-pole spark plug 2 Center electrode 3 Insulator 4 Metal shell 11 Side electrode 12 Spark discharge gap 13 Discharge end face 21 Bending die 23 Bending punch 31 Punching die 33 Punching punch

Claims (2)

[Claims] 1. A method of manufacturing a lateral electrode joined in a state of abutting against a front end surface of a metal shell for fixing an insulator holding a center electrode, wherein (a) a friction resistance is applied to a surface of the lateral electrode. An oil applying step of applying oil for reducing the size, (b) a bending step of pressing the surface of the side electrode against a curved surface of a bending die to form the side electrode into a predetermined bent shape, and (c) ) An oil removing step of removing oil applied to the surface of the side electrode, the method of manufacturing a side electrode for a spark plug. 2. A method of manufacturing a side electrode joined in a state in which it is abutted against a tip surface of a metal shell for fixing an insulator holding a center electrode, comprising: (a) a friction resistance at a tip portion of the side electrode. An oil applying step of applying an oil for reducing the pressure, and (b) a bending step of pressing the tip end surface of the side electrode against a curved surface of a bending die to form the side electrode into a predetermined bent shape. (C) A punching step of punching out the tip of the side electrode. A method of manufacturing a side electrode for a spark plug, comprising: