JP5357822B2 - Spark plug and method of manufacturing the spark plug - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a spark plug with excellent airtightness and a long life, and a method for manufacturing the spark plug. <P>SOLUTION: The spark plug 1 has an insulator 6 provided with a through hole 2 penetrating in an axial direction and having a center electrode 4 on one end thereof; a body metal fitting 3 provided with a clamping cover 11 on a rear end thereof and holding the insulator 6 when an end, at which the center electrode 4 is located, is designated as a tip side and the opposite side is designated as the rear end; and a buffer material filling part filled with a buffer material 9 in a cylindrical space 8 surrounded by an outer periphery of the insulator 6 and an inner periphery of the body metal fitting 3. The plug is provided with an annular pressurizing ring 10 mounted to the outer periphery of the insulator 6 by the clamping cover 11 while contacting the rear end of the buffer material filling part. At least one part of the pressurizing ring 10 is exposed to the outside. <P>COPYRIGHT: (C)2012,JPO&amp;INPIT

Description

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

Spark plugs are used to ignite fuel such as internal combustion engines and burners.
FIG. 8 is applicable to, for example, a gas burner of a fuel cell reformer (see Patent Document 1) for reforming a hydrocarbon-based raw fuel into a gas mainly composed of hydrogen gas. A spark plug 100 is shown.

  The spark plug 100 includes a metal shell 102 having a through-hole 101 penetrating in the axial direction, an insulator 104 having a center electrode 103 attached to the through-hole 101 of the metal shell 102, and a center electrode 103. Powder-like buffering in a cylindrical space 105 surrounded by the outer peripheral surface of the insulator 104 and the inner peripheral surface of the rear end of the metal shell 102 when the end side is the front end side and the opposite side is the rear end side. A caulking lid formed by inwardly caulking the material 106 and a shock-absorbing buffer material filling portion in which packings 107 and 107 are disposed above and below, and a short cylindrical portion 108 protruding from the rear end of the metal shell 102 109. The spark plug 100 generates a spark between the center electrode 103 and a ground electrode provided on the fuel cell reformer (not shown) side to ignite the gas burner.

The spark plug 100 is manufactured by the manufacturing method shown in the left half of FIG. 9, the right half of FIG. 9, the left half of FIG. 10, and the right half of FIG.
That is, as shown in the left half of FIG. 9, between the inner peripheral surface of the rear end of the metal shell 102 and the outer peripheral surface of the insulator 104 with the insulator 104 mounted in the through hole 101 of the metal shell 102. The lower packing 107 is loaded into the space 105, the powder 105 made of ceramic such as talc or kaolin is filled into the space 105, and finally the upper packing 107 is loaded into the space 105. .
Next, as shown in the right half of FIG. 9, a pipe-shaped pressurizing member 110 is fitted from the rear end of the insulator 104, and the upper packing 107 is pressed at the front end of the pressurizing member 110 to pressurize the powder 106. .
Next, as shown in the left half of FIG. 10, the pressure member 110 is removed from the insulator 104 and replaced with a caulking jig 111, and the caulking jig 111 is attached to the short tube portion 108 of the metal shell 102. Place on top of rear end.
Next, as shown in the right half of FIG. 10, an axial load is applied to the caulking jig 111, and the short cylindrical portion 108 of the metal shell 102 is caulked to form an inwardly curved caulking lid 109. To do. With the caulking lid 109, the buffer material 106 is sealed in a space 105 between the metal shell 102 and the insulator 104, and the lower packing 107 is brought into close contact with both the metal shell 102 and the insulator 104 by the pressure. Thus, the space 105 is kept airtight.

JP 2005-141931 A Japanese Patent Application Laid-Open No. 11-242982

Conventionally, in order to obtain a long-life spark plug 100, it has been known that means for improving the airtightness between the metal shell 102 and the insulator 104 is effective (see Patent Document 2: Paragraph [0004]). ).
From this point of view, when the manufacturing process of the spark plug 100 was reviewed to improve the airtightness between the metal shell 102 and the insulator 104, in the process of shifting from the right half of FIG. 9 to the left half of FIG. The pressure member 110 is replaced with the caulking jig 111 in the process of shifting from the step of pressurizing the buffer material 106 with the pressure member 110 to the step of caulking the short cylindrical portion 108 of the metal shell 102 with the caulking jig 111. Since the load applied to the buffer material 106 is once removed and the buffer material 106 is repressurized with the crimping lid 109 from that state, there is a possibility that a part of the initial pressure force is wasted. It turns out that there is.

  The present invention has been made in view of the above, and an object thereof is to provide a long-life spark plug excellent in airtightness and a method of manufacturing the spark plug.

According to a first aspect of the present invention, an insulator having a through-hole penetrating in the axial direction and having a center electrode at one end thereof, an end side where the center electrode is disposed as a front end side, and an opposite side as a rear end A cushioning material in a cylindrical space surrounded by a metal shell that holds the insulator by providing a caulking lid at a rear end thereof, and an outer peripheral surface of the insulator and an inner peripheral surface of the metal shell A spark plug having a buffer material filling portion filled with an annular pressure ring attached to an outer periphery of the insulator by the crimping lid in a state of being in contact with a rear end of the buffer material filling portion. together provided, the pressurized radial crushing provides a spark plug backward projecting amount Ru der than 0mm from a plane perpendicular to the axial direction including the at least partially exposed to the outside and the rearmost end of the crimp cap.

Further, as described in claim 2, provides a spark plug of claim 1 Symbol mounting projecting from the engagable protruding portions to the inside of the crimp cap to an outer periphery of the pressure compressive.

According to a third aspect of the present invention, there is provided the spark plug according to the second aspect , wherein the protruding amount of the convex portion is 0.5 mm or more.

Further, as described in claim 4 , the spark plug manufacturing method according to any one of claims 1 to 3 ,
A filling step of filling the buffer material into the space between the insulator and the metal shell;
A pressure ring mounting step for mounting the pressure ring;
A pressurizing step of applying a load to a rear end of the pressurizing ring and pressurizing the buffer material through the pressurizing ring;
A caulking step of caulking the rear end of the metal shell while applying a load to the pressure ring;
The manufacturing method of the spark plug which has this is provided.

Further, as described in claim 5 , the spark plug manufacturing method according to claim 4 , wherein a load applied in the pressurizing step is 1200 kgf or more.

Further, as described in claim 6, in the pressurizing step, the load applied, the spark plug of claim 4 or 5, wherein it is intended to be removed after crimping process by the caulking jig is completed A manufacturing method is provided.

  The spark plug of the present invention has a pressure ring on the outer periphery of the insulator, and pressurizes the buffer material through the pressure ring, so that the metal fitting is applied by a crimping jig while applying a load to the pressure ring. The short tube portion can be crimped. Therefore, since it is not necessary to interrupt the load which pressurizes the buffer material, the load can be efficiently transmitted to the buffer material filling portion, thereby improving the airtightness of the spark plug.

Further , by setting the amount of backward protrusion of the pressurizing ring from the caulking lid to 0 mm or more, it is possible to prevent the member that pressurizes the pressurizing ring from being caught in the caulking jig.

Further, as described in claim 2 , by providing a protrusion that can be engaged with the inside of the caulking lid on the outer periphery of the pressure ring, the strength of the pressure ring is increased by the rigidity of the protrusion, and the protrusion of the pressure ring. Since it is difficult to be pulled out by being caught inside the caulking lid, the bond strength between the metal shell and the insulator can be further increased.

In addition, as described in claim 3 , the coupling strength between the metal shell and the insulator can be remarkably increased by setting the protruding amount in the radial direction of the convex portion to 0.5 mm or more.

Moreover, according to the manufacturing method of Claim 4 , the spark plug of any one of Claims 1 thru | or 3 can be manufactured easily.

Moreover, the airtight performance of a spark plug can be effectively improved by making the load added in the said pressurization process into 1200 kgf or more like the manufacturing method of Claim 5 .

If the load applied in the pressurizing step is removed after the caulking step by the caulking jig is completed as in the manufacturing method of claim 6, the load applied to the cushioning material is applied from the beginning. Since there is no interruption until the tightening is completed, the load can be efficiently transmitted to the buffer material filling portion, and thereby higher airtightness performance can be obtained.

It is a perspective view of a spark plug shown by cutting out a part of the metal shell. It is the perspective view which made the cross section the part shown side by side in order from the top, a caulking jig, a pressurizing member, a pressurizing ring, and a spark plug. It is a longitudinal cross-sectional view explaining a manufacturing method divided into a left half part and a right half part. It is a longitudinal cross-sectional view explaining a manufacturing method divided into a left half part and a right half part. It is sectional drawing explaining the method of an airtightness evaluation test. It is sectional drawing explaining the joint strength test of a crimping lid and a pressure ring. It is a graph which shows the result of the joint strength test of a caulking lid and a pressure ring. It is a perspective view of the conventional spark plug shown by notching a part of the metal shell. It is a longitudinal cross-sectional view explaining the conventional manufacturing method divided into the left half part and the right half part. It is a longitudinal cross-sectional view explaining the conventional manufacturing method divided into the left half part and the right half part.

Embodiments of the present invention will be described below with reference to the drawings.
As shown in FIG. 1, the spark plug 1 includes a metal shell 3 having a through-hole 2 penetrating in the axial direction, and a center electrode 4 at one end and a terminal at the other end mounted in the through-hole 2 of the metal shell 3. 5 and an airtight holding comprising a ceramic cushioning material 9 such as talc or kaolin filled in the space 8 as well as the packing 7 loaded in the space 8 between the metal shell 3 and the insulator 6. Cushioning material filling portion, a ring-shaped pressure ring 10 that pressurizes the cushioning material 9 of the cushioning material filling portion, and a crimping lid 11 that is formed on the metal shell 3 and attaches the pressure ring 10 to the insulator 6. And.
For convenience of explanation, the direction in which the center electrode 4 is arranged is the front end, and the direction in which the terminal 5 is arranged is the rear end.

  The metal shell 3 is a cylindrical body made of, for example, austenitic stainless steel with a through hole 2 penetrating in the axial direction as a center, and is screwed into a plug mounting hole (not shown) such as a cylinder head or a combustion chamber. And a tool engaging portion 13 with which a plug wrench engages at the rear end. Further, at the rear end of the tool engaging portion 13, an opening of the through hole 2 is provided. A curved caulking lid 11 (see the right half of FIG. 4) is formed by caulking inwardly the short cylindrical portion 14 (see the left half of FIG. 4) protruding so as to surround the outside.

  The through hole 2 of the metal shell 3 is a stepped hole comprising a large diameter portion 2a substantially corresponding to the tool engaging portion 13 and a small diameter portion 2b reaching the tip of the metal shell 3 from the end of the large diameter portion 2a. And if the inside of the short cylinder part 14 before caulking is included in the through-hole 2, as shown in FIG. 3, it will reduce in diameter in three steps toward the front-end | tip from a rear end.

  The insulator 6 is a cylindrical body made of alumina, for example, having an axial hole (not shown) extending in the axial direction as a center, and bulges in a ring shape substantially at the center in the axial direction as shown in FIG. A hook-shaped locking portion 6a, a terminal-side shaft portion 6b extending from the hook-shaped locking portion 6a to the rear end side (upward in FIG. 3), and a distal end side (downward in FIG. 3). ) And the electrode-side shaft portion 6c, the hook-like locking portion 6a is fitted to the large-diameter portion 2a of the through-hole 2 with respect to the metal shell 3, and the electrode-side shaft portion 6c is the through-hole. 2, the terminal side shaft portion 6 b protrudes to the outside through the inside of the large diameter portion 2 a of the through hole 2 and the short tube portion 14. Therefore, there is a space 8 between a part of the insulator 6 above the hook-shaped locking portion 6a and the large diameter portion 2a of the through hole 2 of the metal shell 3 and the inner surface of the short cylindrical portion 14 before caulking. is there.

  As shown in FIG. 1, the pressure ring 10 is attached to the insulator 6 so as to be in contact with the buffer material 9 filled in the space 8, that is, in a state of pressing the buffer material 9. For example, as shown in FIG. 2, the pressure ring 10 has a ring shape in which a flange-like convex portion 10a is projected at the tip, and the crimping lid 11 of the metal shell 3 is folded on the rear surface of the convex portion 10a. So that it does n’t come out. The pressure ring 10 is set to an inner diameter that allows sliding in the axial direction while being fitted to the terminal-side shaft portion 6b of the insulator 6, and the outer diameter of the convex portion 10a that is the maximum outer diameter portion is the above-described caulking It is set to be substantially the same as or smaller than the inner diameter (see FIG. 3) of the lid 11 before caulking (short cylinder portion 14).

  The pressure ring 10 is formed of an insulating material such as ceramic (for example, alumina). Accordingly, since the caulking lid 11 that is integral with the metal shell 3 and has conductivity is positioned on the outer side by the thickness of the insulating pressure ring 10, the insulation surface distance between the terminal 5 and the metal shell 3 can be increased accordingly. it can. As apparent from the above description, the spark plug of the present invention is a non-shield type in which the periphery of the insulator 6 is not surrounded by a conductive material. Therefore, by increasing the insulating surface distance between the terminal 5 and the metal shell 3, The risk of flashover can be reduced.

  In addition, in FIG. 3, reference numeral 15 denotes an opposing portion of the boundary portion between the large-diameter portion 2 a and the small-diameter portion 2 b of the through hole 2 of the metal shell 3 and the boundary portion between the hook-shaped locking portion 6 a and the electrode side shaft portion 6 c. It is a known plate packing loaded.

  Since the spark plug 1 of the embodiment is configured as described above, for example, the screw shaft portion 12 of the metal shell 3 is screwed into a plug mounting hole of a combustion chamber or the like, and is installed facing the center electrode 4 and the combustion chamber side. A spark is discharged between the ground electrode and the fuel to ignite the fuel.

Next, a method for manufacturing the spark plug 1 will be described with reference to FIGS.
First, as shown in the left half of FIG. 3, with the insulator 6 mounted in the through hole 2 of the metal shell 3, the packing 7 is loaded into the space 8 between the metal shell 3 and the insulator 6. 3 is filled with a buffer material 9 such as talc or kaolin powder (packing step), and a pressure ring 10 is fitted on the terminal side shaft 6b of the insulator 6 and slid downward in FIG. The pressure ring 10 is placed on the buffer material 9 filled in the space 8 (pressure ring mounting step).

  Next, as shown in the right half of FIG. 3, a pipe-shaped pressurizing member 110 is fitted from the rear end of the insulator 6, and the front end of the pressurizing member 110 is applied to the rear end of the pressurizing ring 10. Then, a caulking jig 111 having a ring shape and having a mold recess 111 a on the inner lower surface is fitted into the pressure member 110 and is slid downward in FIG. 3 as it is, so that the mold recess 111 a is short tube portion 14 of the metal shell 3. Put it on the top of the rear end.

  Next, as shown in the left half of FIG. 4, for example, a load of 1200 kgf or more is applied to the pressure member 110 in the axial direction, and the cushioning material 9 is pressurized via the pressure ring 10 (pressure process).

  Next, as shown in the right half of FIG. 4, the caulking jig 111 fitted on the outer periphery of the pressure member 110 is moved downward in FIG. The short cylindrical portion 14 of the metal shell 3 is crimped in an inwardly curved shape along the mold recess 111a (a crimping step).

  And if the pressurization member 110 and the crimping jig | tool 111 are removed from the insulator 6 after completion | finish of a crimping process, the spark plug 1 shown in FIG. 1 will be made. Since the spark plug 1 made in this way does not interrupt the load for pressurizing the cushioning material 9 as described above, it can efficiently transmit the load to the packing 7 constituting the cushioning material filling portion. Since the surface pressure increases, the airtightness is improved.

  The metal shell 3 of the embodiment is manufactured from austenitic stainless steel [SUS310S] excellent in heat resistance, and the spark plug 1 is manufactured by the above manufacturing method by combining the metal shell 3, the insulator 6, and the pressure ring 10 made of alumina. Manufactured. At that time, the product applied to the pressurizing member 110 in the pressurizing step was set to 1100 kgf, and the product set to 1300 kgf was set to invention product 2 and the product set to 1300 kgf was set to invention product 3.

In order to evaluate the airtightness of the inventive products 1 to 3, while applying a pressure of 1.5 MPa to the tip side of the spark plug 1 and increasing the temperature of the seating surface 16 of the metal shell 3 as shown in FIG. The amount of gas leaking from the space 8 in one minute was measured with a collection tube 17 placed on the rear end side.
For comparison, the metal shell 102 shown in FIGS. 8 to 10 is manufactured from the same stainless steel as the inventive products 1 to 3, and the spark plug 100 having a conventional structure is manufactured by combining the metal shell 102 and the insulator 104. This was designated as Comparative Example 1. Further, the metal shell 102 is manufactured from ferritic stainless steel [SUS430] having a lower linear expansion coefficient than the comparative example 1, and the spark plug 100 having a conventional structure is manufactured by combining the metal shell 102 and the insulator 104. It was set as Comparative Example 2. Then, using the spark plug 100 of Comparative Examples 1 and 2, the same airtightness evaluation test as described above was performed. The results are shown in Table 1.

According to the results of this airtightness evaluation test, the inventive products 1 to 3 could be confirmed to have excellent airtightness by comparison with Comparative Example 1 having the same stainless steel metal shell 102. .
In addition, by comparing the results of Inventions 1 to 3, it can be confirmed that the greater the load applied to the pressure member 110 in the pressurization step, the more effective the improvement of the airtightness, and 1100 kgf of Invention 1 It was confirmed that the rate of change in the airtight performance was larger between the first and the second invention products of 1200 kgf. Therefore, it is more preferable that the load applied to the pressing member 110 in the pressurizing step is 1200 kgf or more.

By the way, when the comparative example 1 and the comparative example 2 are compared about the result of Table 1, it turns out that the direction of the comparative example 1 using the austenitic stainless steel excellent in heat resistance is inferior in airtightness. This is presumed that the magnitude of the thermal expansion of the austenitic stainless steel causes distortion, which causes the airtightness to decrease. Therefore, under the prior art, even if the metal shell 3 is manufactured from austenitic stainless steel and the heat resistance is improved as a whole, the hermeticity decreases as the temperature rises, and the benefit of the heat resistance is negated. As a result, the overall profit is small.
On the other hand, according to the results of Inventions 1 to 3, it was confirmed that even though it was the same stainless steel as Comparative Example 1, it exhibited excellent airtightness even in a high temperature environment. Therefore, according to the present invention, it is possible to provide a spark plug 1 that is excellent in both airtightness and heat resistance and can sufficiently withstand use at high temperatures.

Four types of pressure ring 10 are manufactured with alumina, and the amount of protrusion in the radial direction of the convex portion 10a at the tip is set to 0.2 mm, 0.5 mm, 0.7 mm, and 1.0 mm. A spark plug 1 of the form was manufactured.
In order to compare the bonding strength between the metal shell 3 and the insulator 6 for this spark plug 1, a pushback load is applied to the center electrode 4 of the spark plug 1 fixed as shown in FIG. The magnitude of the load when it was pushed by the pressure ring 10 and fractured was recorded. The result is shown in the graph of FIG.

  As is apparent from the graph of FIG. 7, the bonding strength between the metal shell 3 and the insulator 6 is practically sufficient in any case, but the protruding amount in the radial direction of the convex portion 10a is set to 0.5 mm or more. In this case, it was confirmed that the bond strength between the metal shell 3 and the insulator 6 was dramatically increased.

The embodiments of the present invention have been described above, but the present invention is of course not limited to the above embodiments. For example, in the embodiment, the type of spark plug 1 that does not have a ground electrode corresponding to the center electrode 4 is illustrated, but the present invention can be similarly applied to a type of spark plug in which a ground electrode is provided at the tip of the metal shell 3.
In the embodiment, the convex portion 10 a is provided at the tip of the pressure ring 10. However, the convex portion 10 a may be provided at a position shifted backward from the tip of the pressure ring 10. Moreover, the pressure ring 10 which does not provide the convex part 10a can also be used. In this case, although the bonding strength between the metal shell 3 and the insulator 6 is reduced to some extent, the benefit of improving the airtightness can be enjoyed.
Moreover, although the convex part 10a was formed so that the perimeter of the pressurization ring 10 might be enclosed in embodiment, you may make it like a gearwheel by interspersing a claw piece-like convex part on the outer periphery of the pressurization ring 10, for example.
In the embodiment, the rear end of the pressurizing ring 10 protrudes from the rear end of the caulking lid 11, but the rear end of the pressurizing ring 10 and the rear end of the caulking lid 11 are aligned on the same plane. May be. In this case, the backward protrusion amount of the pressure ring 10 from the caulking lid 11 is 0 mm.

DESCRIPTION OF SYMBOLS 1 ... Spark plug 2 ... Through-hole 3 ... Main metal fitting 4 ... Center electrode 6 ... Insulator 7 ... Packing 8 ... Space 9 ... Buffer material 10 ... Pressure ring 10a ... Convex part 11 ... Clamping lid 14 ... Short cylinder part 110 ... Pressurizing member 111 ... caulking jig

Claims (6)

An insulator having a through-hole penetrating in the axial direction and having a central electrode at one end thereof;
When the end side on which the center electrode is disposed is the front end side and the opposite side is the rear end side, a metal shell that holds the insulator by providing a caulking lid at the rear end portion;
A spark plug having a buffer material filled with a buffer material in a cylindrical space surrounded by an outer peripheral surface of the insulator and an inner peripheral surface of the metal shell,
The pressure ring includes an annular pressure ring attached to the outer periphery of the insulator by the caulking lid in a state of being in contact with a rear end of the buffer material filling portion, and at least a part of the pressure ring is exposed to the outside, and A spark plug characterized in that a rearward protruding amount from a plane perpendicular to the axial direction including the rear end of the crimping lid is 0 mm or more . Spark plug according to claim 1 Symbol mounting, characterized in that projecting from the engagable protruding portions to the inside of the crimp cap to an outer periphery of the pressure compressive. The spark plug according to claim 2, wherein the protruding amount of the convex portion is 0.5 mm or more. A spark plug manufacturing method according to any one of claims 1 to 3 ,
A filling step of filling the buffer material into the space between the insulator and the metal shell;
A pressure ring mounting step for mounting the pressure ring;
A pressurizing step of applying a load to a rear end of the pressurizing ring and pressurizing the buffer material through the pressurizing ring;
A caulking step of caulking the rear end of the metal shell while applying a load to the pressure ring;
A method of manufacturing a spark plug, comprising: The spark plug manufacturing method according to claim 4 , wherein a load applied in the pressurizing step is 1200 kgf or more. The spark plug manufacturing method according to claim 4 or 5 , wherein the load applied in the pressurizing step is removed after the caulking step by the caulking jig is completed.

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