US20070091542A1 - Spark plug and method of manufacturing same - Google Patents
Spark plug and method of manufacturing same Download PDFInfo
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- US20070091542A1 US20070091542A1 US11/583,063 US58306306A US2007091542A1 US 20070091542 A1 US20070091542 A1 US 20070091542A1 US 58306306 A US58306306 A US 58306306A US 2007091542 A1 US2007091542 A1 US 2007091542A1
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- ground electrode
- housing
- plated layer
- spark plug
- melting point
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01T—SPARK GAPS; OVERVOLTAGE ARRESTERS USING SPARK GAPS; SPARKING PLUGS; CORONA DEVICES; GENERATING IONS TO BE INTRODUCED INTO NON-ENCLOSED GASES
- H01T21/00—Apparatus or processes specially adapted for the manufacture or maintenance of spark gaps or sparking plugs
- H01T21/02—Apparatus or processes specially adapted for the manufacture or maintenance of spark gaps or sparking plugs of sparking plugs
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01T—SPARK GAPS; OVERVOLTAGE ARRESTERS USING SPARK GAPS; SPARKING PLUGS; CORONA DEVICES; GENERATING IONS TO BE INTRODUCED INTO NON-ENCLOSED GASES
- H01T13/00—Sparking plugs
- H01T13/20—Sparking plugs characterised by features of the electrodes or insulation
- H01T13/32—Sparking plugs characterised by features of the electrodes or insulation characterised by features of the earthed electrode
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01T—SPARK GAPS; OVERVOLTAGE ARRESTERS USING SPARK GAPS; SPARKING PLUGS; CORONA DEVICES; GENERATING IONS TO BE INTRODUCED INTO NON-ENCLOSED GASES
- H01T13/00—Sparking plugs
- H01T13/20—Sparking plugs characterised by features of the electrodes or insulation
- H01T13/39—Selection of materials for electrodes
Definitions
- the present invention relates to a spark plug for use in an internal combustion engine of an automobile, cogeneration and so on, and to a method for manufacturing the same.
- a spark plug ignites a mixture gas of fuel and air by firing spark discharge.
- the spark plug has a center electrode, a ground electrode for forming spark discharge gap with the center electrode, and a housing welded to the end of the ground electrode.
- the ground electrode is made of a Ni-based alloy having excellent heat-resistance and acid-proof property such as Inconel 600TM.
- the housing that holds the center electrode is generally made of a low-carbon steel material.
- the surface of housing made of low-carbon steel material is plated for corrosion protection.
- Plating the surface of the housing is disclosed, for example, in U.S. Pat. No. 6,750,597 (Japanese Patent Laid-open Publication No. 2001-68250), which describes that after the housing is welded to the ground electrode, the side of the ground electrode is masked and then the surface of the housing is plated.
- ground electrode 93 is welded to the top surface 941 of the housing 94 that has plated layer 95, after removing a part of the plated layer.
- the removed plated layer portion 99 is desirably formed on only the junction boundary face portion between the ground electrode 93 and the housing 94.
- the plated layer 95 must be removed including an area outside of the junction boundary face to completely remove the plated layer 95 on the junction boundary face. Therefore, as shown FIG. 11, if the removed plated layer portion 99 that remains out side of the ground electrode 93 is not completely protected by the welding burr 96, rust will on gather that portion.
- welding burr 96 cannot completely cover the removed plated layer portion 99, or even if it can do, when adhesion strength is not enough, it may corrode on the housing 94 and, if worst comes to worst, the ground electrode may peel off.
- the plated layer 95 easily remains on the junction boundary face and described problem can easily occur.
- a spark plug comprising: a center electrode; a ground electrode forming a spark discharge gap with said center electrode; a housing welded to an end portion of said ground electrode; and a plated layer formed on a surface of said housing, said plated layer having a melting point lower than a melting point of said housing and a melting point of said ground electrode; substantially no plated layer exists on either of a junction boundary face between said housing and said ground electrode, or on a surface of said ground electrode; and constituents of said plated layer exists in a welding burr formed next to said junction boundary face.
- the method for manufacturing a spark plug including a center electrode; a ground electrode forming a spark gap with said center electrode; and a housing welded to an end portion of said ground electrode; the method including forming a plated layer on a surface of said housing, said plated layer having a melting point in lower than a melting point of the housing and lower than a melting point of the ground electrode, welding between said housing and said ground electrode by resistance welding while contacting an end portion of said ground electrode with a top surface of said housing via said plated layer; and extruding out said plated layer from a junction boundary face between said housing and said ground electrode during said welding.
- FIG. 1 is a cross-section of view of a top portion of a spark plug according to a first example embodiment of the present invention
- FIG. 2 is a side view of the spark plug of FIG. 1 ;
- FIGS. 3A, 3B , and 3 C illustrate a method of manufacturing a spark plug according to the first example embodiment of the present invention
- FIG. 4 illustrates resistance welding between the housing and the ground electrode according to the first example embodiment of the present invention
- FIG. 5 is cross-sectioned view of a junction boundary face between a housing and a ground electrode of spark plug according to the first example embodiment of the present invention
- FIG. 6 is a cross-sectioned view of a welding burr according to the first example embodiment of the present invention.
- FIGS. 7A, 7B , 7 C, and 7 D schematically illustrate a boundary between a welding burr and a housing according to a second example embodiment of the present invention
- FIGS. 8A, 8B , 8 C, and 8 D schematically illustrate a joint boundary between a ground electrode and a housing according to the second example embodiment of the present invention
- FIG. 9 is a cross-sectioned view of a top portion of a spark plug according to a third example embodiment of the present invention.
- FIG. 10 illustrates of resistance welding between a housing and a ground electrode according to the third example embodiment of the present invention
- FIG. 11 schematically illustrates, in cross section, view of the amount of sinking a housing into a ground electrode according to the third example embodiment of the present invention
- FIGS. 12A, 12B , and 12 C schematically illustrate, in cross section, the amount of welding burr at the time of weld between a housing and a ground electrode to fix according to the third example embodiment of the present invention
- FIG. 13 is a graph representing a relationship between the amount of sinking of a housing and a position of remaining phosphor according to the third example embodiment of the present invention.
- FIG. 14 schematically illustrates a method of manufacturing a spark plug according to a fourth example embodiment of the present invention.
- FIG. 15 schematically illustrates a method of manufacturing a spark plug according to a fifth example embodiment of the present invention.
- FIGS. 16A, 16B , 16 C, and 16 D illustrate a method of manufacturing a spark plug according to a comparative example
- FIG. 17 illustrates a method of manufacturing a spark plug according to a prior art
- FIG. 18 illustrates removing a portion according to a prior art
- FIG. 19 illustrates covering a removed plating portion with a welding burr according to a prior art
- FIG. 20A is a cross-sectioned view of an example of a ground electrode
- FIG. 20B is a cross-sectioned view taken along the line XXB-XXB in FIG. 20A ;
- FIG. 21A is a cross-sectioned view of another example of a ground electrode
- FIG. 21B is a cross-sectioned view taken along the line XXIB-XXIB in FIG. 21A .
- a spark plug 1 for an internal combustion engine defined a spark discharge gap G between a center electrode 2 and a ground electrode 3 .
- An end portion 31 of the ground electrode 3 is welded to a housing 4 .
- a plated layer 5 whose melting point is lower than the melting point of the housing 4 and the melting point of the ground electrode 3 is formed on the surface of the housing 4 .
- the plated layer 5 is absent from a junction boundary face 11 between the housing 4 and the ground electrode 3 and on the surface of the ground electrode 3 .
- a welding burr 12 lying next to the junction boundary face 11 includes the constituents of the plated layer 5 .
- the plated layer 5 has the melting point of 1000° C. or less. More specifically, according to one example embodiment, the plated layer 5 consists the electroless nickel plating having a melting point of 890° C.
- the housing 4 is made of an iron based metal and at least the outermost layer of the ground electrode 3 is made of heat-resistant nickel alloy. In one Example, the housing 4 is made of low-carbon steel and at least the outermost layer of the ground electrode 3 is made of Inconel 600TM.
- the spark plug 1 is mounted on an internal combustion engine, such as automobile engine or the like.
- the housing 4 is formed with a screw portion 44 to securing the spark plug 1 to the internal combustion engine, an insulator 13 is secured inside the housing 4 , the center electrode 2 is secured inside the insulator 13 , and the ground electrode 3 is welded to the top surface 41 of the housing 4 .
- a spark discharge gap is formed between the top portion of the center electrode 2 and the ground electrode 3 .
- Noble tips 22 , 32 such as Pt, Ir and so on are formed on the top portion of the center electrode 2 and on the center electrode facing surface of ground electrode.
- a plated layer 5 whose melting point is lower than the melting point of the housing 4 and the melting point of the ground electrode 3 , is formed on the surface of the housing 4 .
- the plated layer 5 made of electroless nickel plating whose melting point is 890° C. is formed on the surface of a housing 4 made of low carbon steel S25C whose melting point is 1589° C.
- the end portion 31 of the ground electrode 3 directly touches the top surface 41 of the housing 4 via a plated layer 5 and is welded there to by resistance welding. At this time, the housing 4 and the ground electrode 3 are joined while extruding out the constituents of the plated layer 5 from the junction boundary face 11 between the housing 4 and the ground electrode 3 .
- the ground electrode 3 is made of Inconel 600 whose melting point is 1425° C.
- the welding burr 12 that includes phosphor (P) as the constituents of the plated layer 5 is formed next to the junction boundary face 11 .
- the housing 4 is received on a lower electrode 61 and the ground electrode 3 is clamped by a pare of upper electrodes 62 .
- the end portion 31 of the clamped ground electrode 3 is directly contacted with the top surface 41 of the housing 4 and is pressed against the top surface 41 .
- the current and press conditions for the resistance welding are selected so that phosphor (P) can be extruded from the junction boundary face 11 alones with the other constituents of the plated layer.
- the ground electrode 3 whose shape of cross section is 1.6 ⁇ 4.1 mm of substantially rectangle is welded to the following condition; current 2.9 kA, cycle 20 , load applied between electrodes 45 kgf.
- the ground electrode 3 is bended and the center electrode 2 held by the insulator 13 is disposed through the inside of the housing 4 .
- the spark discharge gap G is formed between the center electrode 2 and the ground electrode 3 .
- the plated layer 5 is extruded from the junction boundary face 11 between the housing 4 and the ground electrode 3 . Therefore, crack caused by the impurities (phosphor) in plated layer 5 can be prevented in solidification. Thus, the ground electrode 3 can be prevented from separate and junction strength can be ensured.
- the surface of the ground electrode 3 has substantially no plated layer, so that flying sparks and lifted flame resulting from peeling the plated layer by a thermal stress can be prevented, and a fear of a resulting ignition failure can be reduced.
- the melting point of the plated layer 5 is also lower than the melting point of the housing 4 and the melting point of the ground electrode 3 , the plated layer 5 that is exited between the housing 4 and ground electrode 3 directly touching the top surface 41 of the housing is melted at the beginning of during in the resistance welding process. As a result, the plated layer 5 can be extruded out from the junction boundary face 11 . Jointing the housing 4 and the ground electrode 3 while the extruding out from the junction boundary face 11 ensures the junction strength between the housing 4 and the ground electrode 3 .
- the extruded constituents of the plated layer 5 remains in the welding burr formed on the next to the junction boundary face 12 . Even if the welding burr 12 includes the constituents of the plated layer 5 , it dose not influence to the junction strength between the housing and the ground electrode.
- the ground electrode 3 is welded to the housing 4 .
- the plating is easily prevented from adhering the plating on the ground electrode 3 without fail. Accordingly, lifted flame resulting from peeling the plated layer from the ground electrode 3 due to thermal stress can be prevented and then a spark plug that can reduce the likelihood of an ignition failure can be provided.
- the melting point of the plated layer 5 can be sufficiently to be lower than that of the housing 4 and that of the ground electrode 3 . Accordingly, the plated layer 5 can be easily extruded out from the junction boundary face 11 .
- the plated layer 5 that is made of electroless plated nickel has melting point that differs by 500° C. or more as compared to the ground electrode 3 and the housing 4 . For this reason, the plated layer 5 can be easily extruded out from the junction boundary face 11 .
- the plated layer 5 (melting point 890° C.) has a melting point that differs by 180° C. or more as compared to the ground electrode 3 and the housing 4 . For this reason, the plated layer 5 can be also easily extruded out from the junction boundary face 11 .
- an example of a ground electrode 200 has a structure constructed of two-layers of different materials.
- the ground electrode 200 includes a core 220 that is surrounded by an outermost layer portion 210 .
- the core 220 may be made of copper.
- the outermost layer portion 210 may be made of heat-resistant nickel alloy.
- the center portion of the ground electrode may be made of substantially single material such as copper.
- the ground electrode 300 has a structure constructed of three-layers of different materials.
- the ground electrode 300 includes a core 330 , a middle layer portion 320 , and an outermost layer portion 310 .
- the core 330 is surrounded by the middle layer portion 320 , which is further surrounded by the outermost layer portion 310 .
- the core 330 may be made of pure nickel.
- the middle layer portion 320 may be made of copper.
- the outermost layer portion 310 may be made of heat-resistant nickel alloy.
- the center portion of the ground electrode may be made of multiple materials.
- the spark plug 1 can be used for the internal combustion engine of automobile, cogeneration and so on.
- the melting point of the plated layer 5 is 1000° C. or less.
- the plated layer 5 can be easily extruded out from the junction boundary face 11 without fail.
- the plated layer 5 preferred to have a melting point that differs by 180° C. or more as compared to housing 4 and the ground electrode 3 . Furthermore, more preferred to be the difference by 400° C. or more.
- the plated layer 5 is made of electroless nickel plating.
- the plated layer 5 made of electroless nickel plating has a melting point difference of 500° C. or more from the ground electrode 3 and the housing 4 .
- the ground electrode 3 is made of copper (melting point 1083° C.)
- the plated layer 5 has a melting point difference from the housing 4 and the ground electrode 3 of 180° C. or more. For the reason, in the welding process, the plated layer 5 is melted before the housing 4 and the ground electrode 3 without fail, and the plated layer 5 can be easily extruded out from the junction boundary face 11 .
- the plated layer 5 is made of electroless nickel plating.
- the melting point of the plated layer 5 can is sufficiently lower than the melting point of the housing 4 and the ground electrode 3 , the plated layer 5 is easily extruded out from the junction boundary face 11 .
- the housing 4 is also made of low carbon steel such as a steel including iron, the ground electrode 3 is made of Inconel such as a heat resistant nickel alloy. Therefore, the housing 4 can have good formability and be low in price, and the ground electrode 3 can have a high resistance to heat and oxidization at the same time.
- the ground electrode 3 can be made of nickel base alloy for example, Inconel 600TM, Inconel 601 and so on.
- the ground electrode 3 can be made of high thermal conduction metal, such as copper (Cu) and so on that is covered over by a heat resistant nickel alloy.
- this Example can provide the spark plug 1 that has high junction strength between the housing 4 and the ground electrode 3 without the process of masking the ground electrode 3 while forming the plated layer 5 , and without the process of removing the plated later 5 at the only welding portion. Accordingly, the manufacturing cost of the spark plug c 1 an be reduced and, a low price spark plug can be provided.
- the ground electrode 3 can be welded to the housing 4 , and adherence of the plated layer 5 on the ground electrode 3 can be easily prevented without fail.
- FIG. 6 is cross-sectioned view of the welding burr 12 .
- FIG. 7A is enlarged view of dot-line frame A, namely, FIG. 7A is view of side of the boundary between the housing 4 and the vicinity of the end portion of far from side of the ground electrode 3 at welding burr 12 .
- FIGS. 7B, 7C , and 7 D are views mapping the amount of phosphor (P), nickel (Ni) and iron (Fe).
- FIG. 7 is pattern view of patterning a frame format of SEM's photograph and images of mapping in the dot-line frame A of FIG. 6 .
- FIGS. 7B, 7C , and 7 D are views indicating by hatching the relative density of each constituent (P, Ni, Fe) and the relative density represented by each hatching is shown in the explanatory note of FIG. 7E .
- FIG. 8A is an enlarged view of dot-frame B in FIG. 6 , namely, the junction boundary face 11 therefore.
- FIGS. 8B, 8C , and 8 D are views mapping the amount of phosphor (P), nickel (Ni) and iron (Fe).
- FIG. 8 is also pattern view of patterning a frame format of SEM's photograph and of mapping image in the dot-line frame B of FIG. 6 .
- the hatching portion of FIG. 8B , BC, and 8 D are also indicate the relative density of the represented by each hatching is shown in the explanatory note of FIG. 8E .
- phosphor (P) do not exist in the junction boundary face 11 between the ground electrode 3 and housing 4 .
- thin concentration of phosphor (p) can be showed inside of the boundary between the housing 4 and the vicinity of the end portion far from side of the ground electrode 3 , at welding burr 12 .
- FIG. 7B two phosphor (P) layers are distributed in the under and upper sides, the under side layer is shown in phosphor (p) in the plated layer 5 on the surface of the housing 4 , the thickness of the layer is 6 ⁇ 2 ⁇ m.
- Phosphor (p) that distributed in the upper side layer is phosphor (p) in the welding burr 12 .
- the welding burr is formed next to the junction boundary face 11 between the housing 4 and the ground electrode 3 and the resistance welding is carried out so that welding burr 12 includes all the constituents of said plated layer 5 .
- this spark plug is comprised of a projection top portion 43 that is formed on the partial portion of the top side of the housing 4 and, the ground electrode 3 that is jointed with the projection portion 43 in the state of setting down at right angle against the axis direction of the housing 4 .
- a top portion 431 having a smaller cross section is formed on the top of the projection portion 43 .
- the housing 4 is also sunk into the ground electrode 3 by about 0.3 mm or more, and welded to the ground electrode 3 .
- This amount of sinking H is defined as the amount from the standard position in a state of direct contact between the housing 4 and the ground electrode 3 before welding, to the position of the ground electrode 3 against the housing 4 after welding.
- the housing 4 is built in a lower electrode 61 and the ground electrode 5 is disposed on the projection top portion 43 of the housing 4 and pushed against the upper electrode 62 via the housing 4 and then, it is welded to the following condition of resistance welding; current 2.4 kA, cycle 20 , load applied between electrodes 45 kgf.
- Example 1 The other lengths are the same as Example 1.
- the plated layer 5 has been omitted. However, the plated layer is provided as in Example 1.
- the top portion 431 can reduce fluctuation of the junction strength between the housing 4 and the ground electrode 3 . More particularly, since the position of the top portion 431 is formed on the most loaded portion, the welding strength of the portion can be ensured, and the reliability of the welding can be improved.
- a projection portion can be formed on the end portion of the ground electrode 3 and, the projection portion of the ground electrode 3 contacts the top surface of the housing 4 while the ground electrode 3 is welded to the top surface of the housing 4 by resistance welding.
- the plated layer 5 can be easily extruded out from junction boundary face 11 .
- the plated layer 5 that exits on the top surface 41 of the housing 4 is extruded out with evolving welding burr 12 during the resistance welding process between the housing 4 and the ground electrode 3 .
- the welding burr 12 is extruded around the joint boundary burr 11 , the constituent (phosphor) of the plated layer 5 is distributed in the welding burr 12 .
- the plated layer 5 can be smoothly extruded out because the ground electrode 3 is disposed on the top portion 431 and welded by resistance welding. Namely, with reference to FIGS. 12A, 12B , the gap 15 between the housing 4 and the ground electrode 3 that is formed on the side of the top portion 431 forms the route of elimination of the welding burr 12 . And, the welding burr 12 is easily extruded out of the junction boundary face 11 via the gap 15 while the housing 4 sinks.
- the amount of sinking is prescribed by the distance from the situation of touching between the housing 4 before welding to the position of the ground electrode 3 against the housing 4 after welding.
- the constituent (Phosphor) of the plated layer 5 is prevented from remaining in the junction boundary face 11 , and the ground electrode 3 can be ensured to have sufficient junction strength.
- the amount of sinking of the ground electrode 3 into the top surface of the housing 4 is less than 0.3 mm, it may be difficult that the plated layer 5 is extruded out from the junction boundary face 11 .
- the plated layer 5 can be easily extruded out from the junction boundary face 11 between the housing 4 and the ground electrode 3 and, the junction strength between the housing 4 and the ground electrode 3 can be ensured.
- the projection 45 is formed on the top surface portion 41 of the housing 4 and the ground electrode 3 is welded to the housing 4 by resistance welding while directly contacting the end portion 31 of the ground electrode 3 on the projection 45 .
- the shape of projection portion 45 is a triangle shape.
- Example 1 The other shapes are the same as Example 1.
- this Example provides a shape such that the plated layer is easily extruded out, when the area of the junction boundary face between the housing 4 and the ground electrode 3 is large, this Example is particular helpful.
- the projection portion 45 can contribute to reduce fluctuation in the junction strength.
- the projection portion 45 can get an improved result.
- the projection portion 311 is formed on the end portion 31 of the ground electrode 3 .
- the projection portion 311 of the ground electrode 3 is directly contacted with the top surface 41 of the housing 4 and then the ground electrode 3 is welded to the housing by resistance welding.
- the shape of this example of the projection portion 311 is triangle shape, too.
- the ground electrode 3 that is made of Inconel 600 is welded to the housing 4 that is made of low carbon steel by resistance welding.
- the surface of the ground electrode 3 is masked by masking material 91 .
- the masking material 91 is peeled away.
- the ground electrode 3 is bent and the center electrode 2 held by the insulator is inserted inside of the housing 4 . Bending the ground electrode 3 forms the spark discharge G between the center electrode 2 and the ground electrode 3 .
- the spark plug of this comparative example is manufactured.
- the masking step involves provide multiple steps and leads to increase in cost.
- the plated layer may be adhered in the range of 1-2 mm from the end portion in the welded side end of the ground electrode 3 (the end portion 31 ).
- the adhered plated layer that is formed on the welded side end of the ground electrode 3 (the end portion 31 ) is peeled by thermal stress during the engine operation and the peeled plated layer may cause flying sparks or lifted flame and lead to a fear of an ignition.
- the ground electrode is welded to the housing. Therefore, the plated layer is adhered on the ground electrode. There is concern regarding flying sparks or lifted flame.
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Abstract
A spark plug and a method of manufacturing same is provided a spark plug for an internal combustion engine comprising, a center electrode 2, a ground electrode 3 is formed a spark discharge gap G with the center electrode 2, a housing welded to the end portion 31 of the ground electrode 3. The surface of the housing 4 is formed a plated layer 5 whose melting point is lower than the melting point of the housing 4 and is lower than the melting point of the ground electrode 3. There is substantially no the plated layer 5 on a junction boundary face between the housing 4 and the ground electrode 3. The burr including constituents of the plated layer 5 lies next to the junction boundary face 11.
Description
- This application is based on Japanese Patent Application No. 2005-305993 filed on Oct. 20, 2005, the disclosure of which is incorporated herein by reference.
- The present invention relates to a spark plug for use in an internal combustion engine of an automobile, cogeneration and so on, and to a method for manufacturing the same.
- In the combustion chamber of internal combustion engine for use in automobiles, cogeneration and so on, a spark plug ignites a mixture gas of fuel and air by firing spark discharge. The spark plug has a center electrode, a ground electrode for forming spark discharge gap with the center electrode, and a housing welded to the end of the ground electrode.
- Since spark plug is exposed to an environment that has severe heat load, the ground electrode is made of a Ni-based alloy having excellent heat-resistance and acid-proof property such as Inconel 600™. On the other hand, the housing that holds the center electrode is generally made of a low-carbon steel material.
- The surface of housing made of low-carbon steel material is plated for corrosion protection. Plating the surface of the housing is disclosed, for example, in U.S. Pat. No. 6,750,597 (Japanese Patent Laid-open Publication No. 2001-68250), which describes that after the housing is welded to the ground electrode, the side of the ground electrode is masked and then the surface of the housing is plated.
- However, in the case of this plating process, since the ground electrode is not completely covered by the masking material, there is a concern that a plated layer is adhered in the range of 1-2 mm from the end portion of the ground electrode on the welded side end of thereof. In such case, the adhered plated layer is peeled by thermal stress during engine operation and the peeled plated layer may cause flying sparks or lifted flame and causes a fear of an ignition at the end. Furthermore, as this process includes a masking process and multiple steps, this process also tends to increase costs.
- In case of using an electroless Ni plaiting process for forming the plated layer, when the phosphor as an impurely in the plated layer remains on the junction boundary face, it causes a concern that there will be cracks generated during the process of cooling the welding portion. There is the concern that the ground electrode will peel at the base point of cracks portion while using the spark plug and cause ignition failure.
- To solve these the problems, in U.S. Pat. No. 6,819,033 (Japanese Patent Laid-open Publication No. 2003-59617), as shown in FIG. 17 and FIG. 18, after the
plated layer 95 on the welding portion betweenground electrode 93 andhousing 94 is removed, theground electrode 93 is welded on the removed platedlayer portion 99. - Thus,
ground electrode 93 is welded to thetop surface 941 of thehousing 94 that has platedlayer 95, after removing a part of the plated layer. - The problem of this process is that there is an increase in cost because it has multiple steps, furthermore, there is a lack of connection reliability between
housing 94 andground electrode 93. - The latter point is described hereunder in detail.
- The removed plated
layer portion 99 is desirably formed on only the junction boundary face portion between theground electrode 93 and thehousing 94. In fact, as shown FIG. 18, theplated layer 95 must be removed including an area outside of the junction boundary face to completely remove theplated layer 95 on the junction boundary face. Therefore, as shown FIG. 11, if the removed platedlayer portion 99 that remains out side of theground electrode 93 is not completely protected by thewelding burr 96, rust will on gather that portion. Whenwelding burr 96 cannot completely cover the removed platedlayer portion 99, or even if it can do, when adhesion strength is not enough, it may corrode on thehousing 94 and, if worst comes to worst, the ground electrode may peel off. - On the other hand, if the amount of plated layer removed by grinding in advance is not enough, the junction strength is low and there is the concern that the
ground electrode 93 can easily separate from the junction boundary face. Especially, in the case of the electrolytic plating Ni-layer as using theplated layer 95, as the melting point of theplated layer 95 is high, theplated layer 95 easily remains on the junction boundary face and described problem can easily occur. - For this reason, since the accuracy of the plated layer removing process must be improved, this increases in cost too.
- In view of the above-described problems, it is an object of the present invention to provide a spark plug having an improved structure capable of having a weld that is superior in mechanical strength between the ground electrode and the housing and of capable of surely preventing flame-off and ignition failure.
- This object can be achieved by providing a spark plug comprising: a center electrode; a ground electrode forming a spark discharge gap with said center electrode; a housing welded to an end portion of said ground electrode; and a plated layer formed on a surface of said housing, said plated layer having a melting point lower than a melting point of said housing and a melting point of said ground electrode; substantially no plated layer exists on either of a junction boundary face between said housing and said ground electrode, or on a surface of said ground electrode; and constituents of said plated layer exists in a welding burr formed next to said junction boundary face.
- In another embodiment, the method is provided for manufacturing a spark plug including a center electrode; a ground electrode forming a spark gap with said center electrode; and a housing welded to an end portion of said ground electrode; the method including forming a plated layer on a surface of said housing, said plated layer having a melting point in lower than a melting point of the housing and lower than a melting point of the ground electrode, welding between said housing and said ground electrode by resistance welding while contacting an end portion of said ground electrode with a top surface of said housing via said plated layer; and extruding out said plated layer from a junction boundary face between said housing and said ground electrode during said welding.
- Other objects, features and advantages of the present invention will become more apparent from the following detailed description made with reference to the accompanying drawings, in which:
-
FIG. 1 is a cross-section of view of a top portion of a spark plug according to a first example embodiment of the present invention; -
FIG. 2 is a side view of the spark plug ofFIG. 1 ; -
FIGS. 3A, 3B , and 3C illustrate a method of manufacturing a spark plug according to the first example embodiment of the present invention; -
FIG. 4 illustrates resistance welding between the housing and the ground electrode according to the first example embodiment of the present invention; -
FIG. 5 is cross-sectioned view of a junction boundary face between a housing and a ground electrode of spark plug according to the first example embodiment of the present invention; -
FIG. 6 is a cross-sectioned view of a welding burr according to the first example embodiment of the present invention; -
FIGS. 7A, 7B , 7C, and 7D schematically illustrate a boundary between a welding burr and a housing according to a second example embodiment of the present invention; -
FIGS. 8A, 8B , 8C, and 8D schematically illustrate a joint boundary between a ground electrode and a housing according to the second example embodiment of the present invention; -
FIG. 9 is a cross-sectioned view of a top portion of a spark plug according to a third example embodiment of the present invention; -
FIG. 10 illustrates of resistance welding between a housing and a ground electrode according to the third example embodiment of the present invention; -
FIG. 11 schematically illustrates, in cross section, view of the amount of sinking a housing into a ground electrode according to the third example embodiment of the present invention; -
FIGS. 12A, 12B , and 12C schematically illustrate, in cross section, the amount of welding burr at the time of weld between a housing and a ground electrode to fix according to the third example embodiment of the present invention; -
FIG. 13 is a graph representing a relationship between the amount of sinking of a housing and a position of remaining phosphor according to the third example embodiment of the present invention; -
FIG. 14 schematically illustrates a method of manufacturing a spark plug according to a fourth example embodiment of the present invention; -
FIG. 15 schematically illustrates a method of manufacturing a spark plug according to a fifth example embodiment of the present invention; -
FIGS. 16A, 16B , 16C, and 16D illustrate a method of manufacturing a spark plug according to a comparative example; -
FIG. 17 illustrates a method of manufacturing a spark plug according to a prior art; -
FIG. 18 illustrates removing a portion according to a prior art; -
FIG. 19 illustrates covering a removed plating portion with a welding burr according to a prior art; -
FIG. 20A is a cross-sectioned view of an example of a ground electrode, andFIG. 20B is a cross-sectioned view taken along the line XXB-XXB inFIG. 20A ; and -
FIG. 21A is a cross-sectioned view of another example of a ground electrode, andFIG. 21B is a cross-sectioned view taken along the line XXIB-XXIB inFIG. 21A . - An example embodiment of the method of manufacturing of a spark plug for an internal combustion engine of the present invention will be described hereunder with reference to the accompanying drawings, such as from
FIG. 1 toFIG. 6 . - A
spark plug 1 for an internal combustion engine according to an example embodiment of this invention defined a spark discharge gap G between acenter electrode 2 and aground electrode 3. Anend portion 31 of theground electrode 3 is welded to ahousing 4. - A plated
layer 5 whose melting point is lower than the melting point of thehousing 4 and the melting point of theground electrode 3 is formed on the surface of thehousing 4. - The plated
layer 5 is absent from ajunction boundary face 11 between thehousing 4 and theground electrode 3 and on the surface of theground electrode 3. - A welding
burr 12 lying next to thejunction boundary face 11 includes the constituents of the platedlayer 5. - The plated
layer 5 has the melting point of 1000° C. or less. More specifically, according to one example embodiment, the platedlayer 5 consists the electroless nickel plating having a melting point of 890° C. - The
housing 4 is made of an iron based metal and at least the outermost layer of theground electrode 3 is made of heat-resistant nickel alloy. In one Example, thehousing 4 is made of low-carbon steel and at least the outermost layer of theground electrode 3 is made of Inconel 600™. - The
spark plug 1 is mounted on an internal combustion engine, such as automobile engine or the like. Thehousing 4 is formed with ascrew portion 44 to securing thespark plug 1 to the internal combustion engine, aninsulator 13 is secured inside thehousing 4, thecenter electrode 2 is secured inside theinsulator 13, and theground electrode 3 is welded to thetop surface 41 of thehousing 4. A spark discharge gap is formed between the top portion of thecenter electrode 2 and theground electrode 3.Noble tips center electrode 2 and on the center electrode facing surface of ground electrode. - The method of manufacturing of the
spark plug 1 for an internal combustion engine of this invention will be described hereunder with reference to drawings ofFIGS. 3A-3C . - As shown in
FIG. 3A , a platedlayer 5, whose melting point is lower than the melting point of thehousing 4 and the melting point of theground electrode 3, is formed on the surface of thehousing 4. In this Example, the platedlayer 5 made of electroless nickel plating whose melting point is 890° C. is formed on the surface of ahousing 4 made of low carbon steel S25C whose melting point is 1589° C. - After that, as shown in
FIG. 3B , theend portion 31 of theground electrode 3 directly touches thetop surface 41 of thehousing 4 via a platedlayer 5 and is welded there to by resistance welding. At this time, thehousing 4 and theground electrode 3 are joined while extruding out the constituents of the platedlayer 5 from thejunction boundary face 11 between thehousing 4 and theground electrode 3. In this example, theground electrode 3 is made of Inconel 600 whose melting point is 1425° C. - As shown in
FIGS. 5, 6 , the weldingburr 12 that includes phosphor (P) as the constituents of the platedlayer 5 is formed next to thejunction boundary face 11. - In welding process, as shown in
FIG. 4 , thehousing 4 is received on alower electrode 61 and theground electrode 3 is clamped by a pare ofupper electrodes 62. Theend portion 31 of the clampedground electrode 3 is directly contacted with thetop surface 41 of thehousing 4 and is pressed against thetop surface 41. - In this situation, the current and press conditions for the resistance welding are selected so that phosphor (P) can be extruded from the
junction boundary face 11 alones with the other constituents of the plated layer. In this Example, theground electrode 3 whose shape of cross section is 1.6×4.1 mm of substantially rectangle is welded to the following condition; current 2.9 kA, cycle 20, load applied betweenelectrodes 45 kgf. - As shown in
FIG. 3C , theground electrode 3 is bended and thecenter electrode 2 held by theinsulator 13 is disposed through the inside of thehousing 4. The spark discharge gap G is formed between thecenter electrode 2 and theground electrode 3. - The function and result of this Example will be described.
- In the above method, the plated
layer 5 is extruded from thejunction boundary face 11 between thehousing 4 and theground electrode 3. Therefore, crack caused by the impurities (phosphor) in platedlayer 5 can be prevented in solidification. Thus, theground electrode 3 can be prevented from separate and junction strength can be ensured. - In addition, since the surface of the
ground electrode 3 has substantially no plated layer, so that flying sparks and lifted flame resulting from peeling the plated layer by a thermal stress can be prevented, and a fear of a resulting ignition failure can be reduced. - Thus after the plated
layer 5 is formed on the surface of thehousing 4, and without the need to eliminate a portion of the plated layer, resistance welding is performed while directly touching theend portion 31 of theground electrode 3 on thetop surface 41 of thehousing 4 via a platedlayer 5. For this reason, masking theground electrode 3 before forming the platedlayer 5 is not required, nor is the process of eliminating the plated layer at the welding portion. For this reason, the manufacturing cost is reduced so that aninexpensive spark plug 1 can be provided. - As the melting point of the plated
layer 5 is also lower than the melting point of thehousing 4 and the melting point of theground electrode 3, the platedlayer 5 that is exited between thehousing 4 andground electrode 3 directly touching thetop surface 41 of the housing is melted at the beginning of during in the resistance welding process. As a result, the platedlayer 5 can be extruded out from thejunction boundary face 11. Jointing thehousing 4 and theground electrode 3 while the extruding out from thejunction boundary face 11 ensures the junction strength between thehousing 4 and theground electrode 3. - The extruded constituents of the plated
layer 5 remains in the welding burr formed on the next to thejunction boundary face 12. Even if the weldingburr 12 includes the constituents of the platedlayer 5, it dose not influence to the junction strength between the housing and the ground electrode. - As explained above, after the plated
layer 5 is formed on the whole surface of thehousing 4, theground electrode 3 is welded to thehousing 4. For this reasons the plating is easily prevented from adhering the plating on theground electrode 3 without fail. Accordingly, lifted flame resulting from peeling the plated layer from theground electrode 3 due to thermal stress can be prevented and then a spark plug that can reduce the likelihood of an ignition failure can be provided. - As the plated
layer 5 of this example consists of electroless nickel-plating, the melting point of the platedlayer 5 can be sufficiently to be lower than that of thehousing 4 and that of theground electrode 3. Accordingly, the platedlayer 5 can be easily extruded out from thejunction boundary face 11. - Namely, when the
housing 4 is made of low carbon steel (melting point 1539° C.) and theground electrode 3 is made of Inconel 600 (melting point 1425° C.), the platedlayer 5 that is made of electroless plated nickel has melting point that differs by 500° C. or more as compared to theground electrode 3 and thehousing 4. For this reason, the platedlayer 5 can be easily extruded out from thejunction boundary face 11. - For example, when the core of the
ground electrode 3 is made of copper (melting point 1083° C.) that has high coefficient of thermal conductivity material, the plated layer 5 (melting point 890° C.) has a melting point that differs by 180° C. or more as compared to theground electrode 3 and thehousing 4. For this reason, the platedlayer 5 can be also easily extruded out from thejunction boundary face 11. - As follows, examples of ground electrodes are described. As shown in
FIGS. 20A, 20B , an example of aground electrode 200 has a structure constructed of two-layers of different materials. For example, theground electrode 200 includes a core 220 that is surrounded by anoutermost layer portion 210. Thecore 220 may be made of copper. Theoutermost layer portion 210 may be made of heat-resistant nickel alloy. As shown in this example, the center portion of the ground electrode may be made of substantially single material such as copper. - Alternatively, as shown in
FIGS. 21A, 21B , another example of aground electrode 300 has a structure constructed of three-layers of different materials. For example, theground electrode 300 includes acore 330, amiddle layer portion 320, and anoutermost layer portion 310. Thecore 330 is surrounded by themiddle layer portion 320, which is further surrounded by theoutermost layer portion 310. Thecore 330 may be made of pure nickel. Themiddle layer portion 320 may be made of copper. Theoutermost layer portion 310 may be made of heat-resistant nickel alloy. As shown in this example, the center portion of the ground electrode may be made of multiple materials. - The
spark plug 1 can be used for the internal combustion engine of automobile, cogeneration and so on. - In a preferred embodiment of the above aspect, the melting point of the plated
layer 5 is 1000° C. or less. - In this case where, the plated
layer 5 can be easily extruded out from thejunction boundary face 11 without fail. - There is copper (melting point is 1083° C.), such as having low melting point that is generally used among the
housing 4 and theground electrode 3 for thespark plug 1. When the melting point of the platedlayer 5 is 1000° C. or less, even if theground electrode 3 is made of copper, since the platedlayer 5 is melted the beginning of welding process, the platedlayer 5 is easily extruded out from thejunction boundary face 11 and the platedlayer 5 can be prevented from remaining in thejunction boundary face 11. Especially, the platedlayer 5 preferred to have a melting point that differs by 180° C. or more as compared tohousing 4 and theground electrode 3. Furthermore, more preferred to be the difference by 400° C. or more. - In a preferred embodiment of the above aspect, the plated
layer 5 is made of electroless nickel plating. - Namely, when the
housing 4 is made of low-carbon steel (melting point 1539° C.) and theground electrode 3 is made of Inconel 600 alloy (melting point 1425° C.), the platedlayer 5 made of electroless nickel plating (melting point 890° C.) has a melting point difference of 500° C. or more from theground electrode 3 and thehousing 4. If, for example, theground electrode 3 is made of copper (melting point 1083° C.), the platedlayer 5 has a melting point difference from thehousing 4 and theground electrode 3 of 180° C. or more. For the reason, in the welding process, the platedlayer 5 is melted before thehousing 4 and theground electrode 3 without fail, and the platedlayer 5 can be easily extruded out from thejunction boundary face 11. - The plated
layer 5 is made of electroless nickel plating. - In this case, since the melting point of the plated
layer 5 can is sufficiently lower than the melting point of thehousing 4 and theground electrode 3, the platedlayer 5 is easily extruded out from thejunction boundary face 11. - The
housing 4 is also made of low carbon steel such as a steel including iron, theground electrode 3 is made of Inconel such as a heat resistant nickel alloy. Therefore, thehousing 4 can have good formability and be low in price, and theground electrode 3 can have a high resistance to heat and oxidization at the same time. - Furthermore, the steel including metal of the
housing 4, low-carbon steel, stainless and so on. Theground electrode 3 can be made of nickel base alloy for example, Inconel 600™, Inconel 601 and so on. Theground electrode 3 can be made of high thermal conduction metal, such as copper (Cu) and so on that is covered over by a heat resistant nickel alloy. - In this way, this Example can provide the
spark plug 1 that has high junction strength between thehousing 4 and theground electrode 3 without the process of masking theground electrode 3 while forming the platedlayer 5, and without the process of removing the plated later 5 at the only welding portion. Accordingly, the manufacturing cost of the spark plug c1 an be reduced and, a low price spark plug can be provided. - As aforementioned, after the plated
layer 5 is formed on the surface of the whole of thehousing 4, theground electrode 3 can be welded to thehousing 4, and adherence of the platedlayer 5 on theground electrode 3 can be easily prevented without fail. - As mentioned above, with this Example, an inexpensive method manufacturing of the
spark plug 1 for an internal combustion engine, that has a high junction strength between thehousing 4 and theground electrode 3 and, decreased ignition failure, can be provided. -
FIG. 6 is cross-sectioned view of the weldingburr 12.FIG. 7A is enlarged view of dot-line frame A, namely,FIG. 7A is view of side of the boundary between thehousing 4 and the vicinity of the end portion of far from side of theground electrode 3 at weldingburr 12.FIGS. 7B, 7C , and 7D are views mapping the amount of phosphor (P), nickel (Ni) and iron (Fe).FIG. 7 is pattern view of patterning a frame format of SEM's photograph and images of mapping in the dot-line frame A ofFIG. 6 . InFIGS. 7B, 7C , and 7D are views indicating by hatching the relative density of each constituent (P, Ni, Fe) and the relative density represented by each hatching is shown in the explanatory note ofFIG. 7E . -
FIG. 8A is an enlarged view of dot-frame B inFIG. 6 , namely, thejunction boundary face 11 therefore.FIGS. 8B, 8C , and 8D are views mapping the amount of phosphor (P), nickel (Ni) and iron (Fe).FIG. 8 is also pattern view of patterning a frame format of SEM's photograph and of mapping image in the dot-line frame B ofFIG. 6 . The hatching portion ofFIG. 8B , BC, and 8D are also indicate the relative density of the represented by each hatching is shown in the explanatory note ofFIG. 8E . - With reference to
FIG. 8B , phosphor (P) do not exist in thejunction boundary face 11 between theground electrode 3 andhousing 4. On the other hand, with reference toFIG. 7B , thin concentration of phosphor (p) can be showed inside of the boundary between thehousing 4 and the vicinity of the end portion far from side of theground electrode 3, at weldingburr 12. InFIG. 7B , two phosphor (P) layers are distributed in the under and upper sides, the under side layer is shown in phosphor (p) in the platedlayer 5 on the surface of thehousing 4, the thickness of the layer is 6±2 μm. Phosphor (p) that distributed in the upper side layer is phosphor (p) in the weldingburr 12. - The result of a quantity analysis of the area of 5×5 μm˜10×10μ which is enlarged of multiple portion of the portion, that Phosphor (p) is distributed in the upper side layer, was detected 5˜15 wt % of phosphor (p).
- On the other hand, the other portion of
FIG. 7B was detected. In the result, the result of the quantitative analysis was detected 0.01 wt % or less of phosphor (p). The result of the quantitative analysis of phosphor (p) inFIG. 8B was 0.01 wt % or less. - As mentioned above, in this Example, it can be confirmed that the plated
layer 5 in thejunction boundary face 11 is melted and concentrated in the vicinity of the top of the weldingburr 12 during formation of the weldingburr 12 and then extruded out. - In this Example, the welding burr is formed next to the
junction boundary face 11 between thehousing 4 and theground electrode 3 and the resistance welding is carried out so that weldingburr 12 includes all the constituents of said platedlayer 5. - In this cases where, the constituents of the plated
layer 5 that exit from between thehousing 4 and theground electrode 3 are extruded out from thejunction boundary face 11 with the weldingburr 12. Even though constituents of the platedlayer 5, exist in the weldingburr 12, including impurities such as phosphor, it dose not influence the junction strength between thehousing 4 and theground electrode 3. For this reason an inexpensive spark plug that has a high junction strength between thehousing 4 and theground electrode 3 and reduced ignition failure is easily provided. - In this Example, with reference to
FIGS. 9-13 , for example, this spark plug is comprised of aprojection top portion 43 that is formed on the partial portion of the top side of thehousing 4 and, theground electrode 3 that is jointed with theprojection portion 43 in the state of setting down at right angle against the axis direction of thehousing 4. - A
top portion 431 having a smaller cross section is formed on the top of theprojection portion 43. - With reference to
FIG. 11 , in this Example, thehousing 4 is also sunk into theground electrode 3 by about 0.3 mm or more, and welded to theground electrode 3. This amount of sinking H is defined as the amount from the standard position in a state of direct contact between thehousing 4 and theground electrode 3 before welding, to the position of theground electrode 3 against thehousing 4 after welding. - With reference to
FIG. 10 , in the welding process, thehousing 4 is built in alower electrode 61 and theground electrode 5 is disposed on theprojection top portion 43 of thehousing 4 and pushed against theupper electrode 62 via thehousing 4 and then, it is welded to the following condition of resistance welding; current 2.4 kA, cycle 20, load applied betweenelectrodes 45 kgf. - In one example, the shape of the
projection portion 431 of theprojection top portion 43 is as follows; width w=11.0 mm, amount of projection u=0.2 mm. Thickness t of theground electrode 5 is 1.6 mm, the distance s from the end surface of theground electrode 5 to theprojection potion 431 is 6.0 mm. - The other lengths are the same as Example 1. In
FIG. 9-12 , the platedlayer 5 has been omitted. However, the plated layer is provided as in Example 1. - In this Example, since welding current is constricted to the
top potion 431 of theprojection portion 43 formed in a small cross section, the current density increases, and the platedlayer 5 formed on thetop surface 41 of thehousing 4 is easily melted and can be extruded out. - Since it is heated at the certain point at first, the
top portion 431 can reduce fluctuation of the junction strength between thehousing 4 and theground electrode 3. More particularly, since the position of thetop portion 431 is formed on the most loaded portion, the welding strength of the portion can be ensured, and the reliability of the welding can be improved. - A projection portion can be formed on the end portion of the
ground electrode 3 and, the projection portion of theground electrode 3 contacts the top surface of thehousing 4 while theground electrode 3 is welded to the top surface of thehousing 4 by resistance welding. - Since low current can easily heat welding portion, the plated
layer 5 can be easily extruded out fromjunction boundary face 11. - By sinking the
housing 4 into theground electrode 3 by about 0.3 mm or more, since a sufficient amount of the platedlayer 5 can be easily extruded out fromjunction boundary face 11, the junction strength between thehousing 4 and theground electrode 3 can be ensured. - Namely, since the
top surface 41 of thehousing 4 is sunk into theground electrode 3 by about 0.3 mm or more, with reference toFIGS. 12A-12C , the platedlayer 5 that exits on thetop surface 41 of thehousing 4 is extruded out with evolving weldingburr 12 during the resistance welding process between thehousing 4 and theground electrode 3. With reference toFIG. 12C , the weldingburr 12 is extruded around thejoint boundary burr 11, the constituent (phosphor) of the platedlayer 5 is distributed in the weldingburr 12. - Also, the plated
layer 5 can be smoothly extruded out because theground electrode 3 is disposed on thetop portion 431 and welded by resistance welding. Namely, with reference toFIGS. 12A, 12B , thegap 15 between thehousing 4 and theground electrode 3 that is formed on the side of thetop portion 431 forms the route of elimination of the weldingburr 12. And, the weldingburr 12 is easily extruded out of thejunction boundary face 11 via thegap 15 while thehousing 4 sinks. - With reference to
FIG. 13 , in this Example, the relation between the amount of sinking of the housing H and the position of remaining Phosphor (p) as the constituent of the platedlayer 5 is confirmed. - With reference to
FIG. 13 , when the amount of sinking H is less than 0.3 mm, there is Phosphor (p) in thejunction boundary face 11. When the amount of sinking H is larger, the existing area is smaller. But when the amount of sinking H is 0.3 mm or more, there is no Phosphor (p) in thejunction boundary face 11. - The amount of sinking is prescribed by the distance from the situation of touching between the
housing 4 before welding to the position of theground electrode 3 against thehousing 4 after welding. - As mentioned above, when the amount of sinking is 0.3 mm or more, the constituent (Phosphor) of the plated
layer 5 is prevented from remaining in thejunction boundary face 11, and theground electrode 3 can be ensured to have sufficient junction strength. - Namely, when the amount of sinking of the
ground electrode 3 into the top surface of thehousing 4 is less than 0.3 mm, it may be difficult that the platedlayer 5 is extruded out from thejunction boundary face 11. - Since the plated
layer 5 can be easily extruded out from thejunction boundary face 11 between thehousing 4 and theground electrode 3 and, the junction strength between thehousing 4 and theground electrode 3 can be ensured. - The other of the effect and the result are the same as Example 1.
- With reference to
FIG. 14 , in this Example, theprojection 45 is formed on thetop surface portion 41 of thehousing 4 and theground electrode 3 is welded to thehousing 4 by resistance welding while directly contacting theend portion 31 of theground electrode 3 on theprojection 45. - The shape of
projection portion 45 is a triangle shape. - The other shapes are the same as Example 1.
- In this Example case, whereby the shape of the
projection portion 45 is a triangle shape, electroless nickel-plating that is melting along the slope of theprojection portion 45 is easily extruded out while the weldingburr 12 evolves. - As mentioned above, since this Example provides a shape such that the plated layer is easily extruded out, when the area of the junction boundary face between the
housing 4 and theground electrode 3 is large, this Example is particular helpful. - Since lower current than the case of no projection portion can heat the welding portion, the welding area of the
ground electrode 3 is prevented from expanding more than necessity. Accordingly, theprojection portion 45 can contribute to reduce fluctuation in the junction strength. - The other effects and the result are the same as Example 1.
- Even if the shape of the
projection portion 45 is, for example a semicircle, a rectangle and so on, theprojection portion 45 can get an improved result. - With reference to
FIG. 15 , in this Example, theprojection portion 311 is formed on theend portion 31 of theground electrode 3. Theprojection portion 311 of theground electrode 3 is directly contacted with thetop surface 41 of thehousing 4 and then theground electrode 3 is welded to the housing by resistance welding. - The shape of this example of the
projection portion 311 is triangle shape, too. - The composition, the effect and the result is otherwise the same as Example 4.
- With reference to
FIGS. 16A-16D , in this Example, according to the method of manufacturing a spark plug of the comparative example, after theground electrode 3 is welded to thehousing 4, the platedlayer 50 is formed on the surface of thehousing 4 by electrolytic nickel plating and the spark plug of this comparative can be obtained. - Namely, with reference to
FIG. 16A , theground electrode 3 that is made of Inconel 600 is welded to thehousing 4 that is made of low carbon steel by resistance welding. - Next, at first, with reference to
FIG. 16B , the surface of theground electrode 3 is masked by maskingmaterial 91. - Next, with reference to
FIG. 16C , after the platedlayer 50 is formed the surface of thehousing 4 by electrolytic nickel plating, the maskingmaterial 91 is peeled away. - Next, with reference to
FIG. 16D , theground electrode 3 is bent and thecenter electrode 2 held by the insulator is inserted inside of thehousing 4. Bending theground electrode 3 forms the spark discharge G between thecenter electrode 2 and theground electrode 3. - As mentioned above, the spark plug of this comparative example is manufactured.
- In the method of manufacturing a spark plug of this comparative example, as mentioned above, since masking
material 91 need to be required, the masking step involves provide multiple steps and leads to increase in cost. - Since the
ground electrode 3 is difficult to completely cover with maskingmaterial 91, the plated layer may be adhered in the range of 1-2 mm from the end portion in the welded side end of the ground electrode 3 (the end portion 31). In such case, the adhered plated layer that is formed on the welded side end of the ground electrode 3 (the end portion 31) is peeled by thermal stress during the engine operation and the peeled plated layer may cause flying sparks or lifted flame and lead to a fear of an ignition. - According to, this invention, as discussed previously, since there is not masking process, the manufacturing steps are reduced and an inexpensive spark plug can be provided.
- Accordingly, after the plated layer is formed on the surface of the housing, the ground electrode is welded to the housing. Therefore, the plated layer is adhered on the ground electrode. There is concern regarding flying sparks or lifted flame.
- Although the present invention has been fully described in connection with the preferred embodiments thereof with reference to the accompanying drawings, it is to be noted that various changes and modifications will become apparent to those skilled in the art.
Claims (11)
1. A spark plug comprising:
a center electrode;
a ground electrode forming a spark discharge gap with said center electrode;
a housing welded to an end portion of said ground electrode;
a plated layer formed on a surface of said housing, said plated layer having a melting point lower than a melting point of said housing and lower than a melting point of said ground electrode;
substantially no plated layer exists on either of a junction boundary face between said housing and said ground electrode, or on a surface of said ground electrode; and
constituents of said plated layer exists in a welding burr formed next to said junction boundary face.
2. A spark plug according to claim 1 , wherein said melting point of the plated layer is 1000° C. or less.
3. A spark plug according to claim 1 , wherein said plated layer is made of electroless nickel plating.
4. A spark plug according to claim 1 , wherein said housing is made of metal including iron and the outermost layer of the ground electrode is at least made of heat-resistant nickel alloy.
5. A spark plug according to claim 1 , wherein said housing is sunk into said ground electrode by about 0.3 mm or more, and welded to the housing.
6. A method of manufacturing a spark including a center electrode; a ground electrode forming a spark gap with said center electrode; and a housing welded to an end portion of said ground electrode; the method including:
forming a plated layer on a surface of said housing, said plated layer having a melting point in lower than a melting point of the housing and lower than a melting point of the ground electrode;
welding between said housing and said ground electrode by resistance welding while contacting an end portion of said ground electrode with a top surface of said housing via said plated layer; and
extruding out constituents said plated layer from a junction boundary face between said housing and said ground electrode during said welding.
7. A method for manufacturing a spark plug according to claim 6 , wherein the welding burr is formed next to the junction boundary face between the housing and the ground electrode and the resistance welding is carried out so that welding burr includes all the constituents of said plated layer.
8. A method for manufacturing a spark plug according to claim 6 , wherein a projecting portion is formed on said top surface of said housing and, said ground electrode is welded to said housing by resistance welding with said projection portion contacts said end portion of said ground electrode.
9. A method for manufacturing a spark plug according to claim 6 , wherein a projection portion is formed on said end portion of said ground electrode and, said projection portion of said ground electrode contacts said top surface of said housing while said ground electrode is welded to said top surface of said housing by resistance welding.
10. A method for manufacturing a spark plug according to claim 6 , wherein said plated layer is made of electroless nickel plating.
11. A method for manufacturing a spark plug according to claim 6 , wherein said housing is sunk into said ground electrode by about 0.3 mm or more, and welded to said housing.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
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JP2005-305993 | 2005-10-20 | ||
JP2005305993A JP2007115537A (en) | 2005-10-20 | 2005-10-20 | Spark plug for internal combustion engine and method of manufacturing the same |
Publications (1)
Publication Number | Publication Date |
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US20070091542A1 true US20070091542A1 (en) | 2007-04-26 |
Family
ID=37912963
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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US11/583,063 Abandoned US20070091542A1 (en) | 2005-10-20 | 2006-10-19 | Spark plug and method of manufacturing same |
Country Status (3)
Country | Link |
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US (1) | US20070091542A1 (en) |
JP (1) | JP2007115537A (en) |
DE (1) | DE102006035359A1 (en) |
Cited By (2)
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---|---|---|---|---|
EP2553780A1 (en) | 2010-03-31 | 2013-02-06 | Federal-Mogul Ignition Company | Spark ignition device and ground electrode therefor and methods of construction thereof |
CN103968416A (en) * | 2013-02-04 | 2014-08-06 | 气体产品与化学公司 | Retractable ignition system |
Families Citing this family (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP6342446B2 (en) * | 2016-05-18 | 2018-06-13 | 日本特殊陶業株式会社 | Method for manufacturing cylindrical metal shell with rod for ground side electrode for spark plug, and method for manufacturing spark plug |
JP6998667B2 (en) * | 2017-03-30 | 2022-01-18 | 古河電気工業株式会社 | Connection structure |
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US5073741A (en) * | 1989-12-29 | 1991-12-17 | Ngk Spark Plug Co., Ltd. | Igniter plug |
US6119667A (en) * | 1999-07-22 | 2000-09-19 | Delphi Technologies, Inc. | Integrated spark plug ignition coil with pressure sensor for an internal combustion engine |
US6750597B1 (en) * | 1999-08-26 | 2004-06-15 | Ngk Spark Plug, Co., Ltd. | Method for manufacturing spark plug and spark plug |
US6819033B2 (en) * | 2001-08-22 | 2004-11-16 | Denso Corporation | Spark plug and method of manufacturing same |
-
2005
- 2005-10-20 JP JP2005305993A patent/JP2007115537A/en not_active Withdrawn
-
2006
- 2006-10-19 DE DE102006035359A patent/DE102006035359A1/en not_active Withdrawn
- 2006-10-19 US US11/583,063 patent/US20070091542A1/en not_active Abandoned
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US5073741A (en) * | 1989-12-29 | 1991-12-17 | Ngk Spark Plug Co., Ltd. | Igniter plug |
US6119667A (en) * | 1999-07-22 | 2000-09-19 | Delphi Technologies, Inc. | Integrated spark plug ignition coil with pressure sensor for an internal combustion engine |
US6750597B1 (en) * | 1999-08-26 | 2004-06-15 | Ngk Spark Plug, Co., Ltd. | Method for manufacturing spark plug and spark plug |
US6819033B2 (en) * | 2001-08-22 | 2004-11-16 | Denso Corporation | Spark plug and method of manufacturing same |
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
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EP2553780A1 (en) | 2010-03-31 | 2013-02-06 | Federal-Mogul Ignition Company | Spark ignition device and ground electrode therefor and methods of construction thereof |
CN103968416A (en) * | 2013-02-04 | 2014-08-06 | 气体产品与化学公司 | Retractable ignition system |
US9273867B2 (en) | 2013-02-04 | 2016-03-01 | Air Products And Chemicals, Inc. | Retractable ignition system |
Also Published As
Publication number | Publication date |
---|---|
DE102006035359A1 (en) | 2007-05-03 |
JP2007115537A (en) | 2007-05-10 |
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