CA1046369A - Internal combustion engine spark plug having composite electrode structure - Google Patents
Internal combustion engine spark plug having composite electrode structureInfo
- Publication number
- CA1046369A CA1046369A CA235,536A CA235536A CA1046369A CA 1046369 A CA1046369 A CA 1046369A CA 235536 A CA235536 A CA 235536A CA 1046369 A CA1046369 A CA 1046369A
- Authority
- CA
- Canada
- Prior art keywords
- spark plug
- plug according
- jacket
- strands
- matrix
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- 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
Landscapes
- Spark Plugs (AREA)
- Ropes Or Cables (AREA)
- Manufacture Of Alloys Or Alloy Compounds (AREA)
Abstract
"INTERNAL COMBUSTION ENGINE SPARK
PLUG HAVING COMPOSITE ELECTRODE
STRUCTURE"
ABSTRACT OF THE DISCLOSURE
The electrode has a tip formed of an outer jacket of corrosion-resistant material, such as essentially nickel, which surrounds a composite core formed of up to half, by volume, copper as a matrix in which filaments or strands essentially containing nickel are embedded, to provide an electrode made of readily available, inexpensive material and permitting a long insulator tip.
PLUG HAVING COMPOSITE ELECTRODE
STRUCTURE"
ABSTRACT OF THE DISCLOSURE
The electrode has a tip formed of an outer jacket of corrosion-resistant material, such as essentially nickel, which surrounds a composite core formed of up to half, by volume, copper as a matrix in which filaments or strands essentially containing nickel are embedded, to provide an electrode made of readily available, inexpensive material and permitting a long insulator tip.
Description
~o46369 The present invention relates to spark plugs for u~e in internal combustion engines, and more particularly to the cente~ electrode used in such spark plugs, and especially to a composite electrode structure for such spark plugs which has high conductivity with respect to heat and electricity, and is resistant to corrosion and burning.
Various types of internal combustion engine~ used in automotive power plants, to provide power forvarious types of appliances, and the like, require different types of spark plugs. It is difficult to provide a single type of spark plug for different motors, and even for motors which are of essentially similar construction, in view of~the different power loading on the motor, different operatian, compression ratio, speed, cooling, carburation, and type of fuel supply. If a single type of spark plug would be used for various engines, or for an engine subject to different operating conditions, then such a spark plug might, under some operating conditions, become too hot ~` while, under other operating conditions, or with different motors, would have too low an average temperature. If the spark plug becomes too hot, then the fuel-air mixture can self-ignite on the elements of the spark plugs extending into the combustion space of the engine, resulting in ignition due to glow of the spark plug, and in misfires.
If the spark plug operates too cool, then the insulator tip ~ ourrounding the center electrode, extending into the i !
:` ` . I
., i combustion ~pace of the engine, would rapidly become contaminated by combustion residues. Misfires, in the sense of failure of sparking, would result due to spurious electrical paths through combustion residues or deposits.
Thus, the spark plug to be used in the internal combustion engine ~ust be matched to the engine, so that the plug, in a specific motor, does not become too hot, nor remain too cold. This requires spark plugs with different load characteristics. These different load characteristic~ are evaluated by designation by a heat number, associated with each spark plug. The heat number~ or heat value of a spark plug, expressed as an arbitrary number, characterizes the resistance of the spark plug with respect to overheating: ;
a higher heat number permits higher loading of the spark plug without danger of spurious ignition due to glowing of the spark plug but, on the other hand, it has a higher tendency to become contaminated, since the self-cleaning temperature is not reached as rapidly upon starting of a c~ld engine and is easily passed in downward direction upon throttling of the motor.
Spark plugs can be designed to have various heat numbers by suitably shaping the insulator surface which has '' to accept the heat to which the spark plug is subjected.
Assuming an egual diameter for a specific spark plug, that 25~ is, the same diameter of the spark plug housing, the length of the inculator tip adjacent tho electrode tip has a ~ ~ ..................................................... I
. , . ~ . .
definite bearing on the heat number. Spark plugs with a high heat value have short insulator tips; spark plugs with a low heat ~wmber have long insulator tips. The spark plug must reach a temperature of about 500C in order to be self-cleaning, that is, to spontaneously burn off deposits such as soot, oil, carbonized oil,or the like, which may deposit on the insulator of the spark plug. The burning of these deposits should be sufficiently effective to prevent short circuits for the spark current being supplied to the electrode. To permit such burn-off, the spark plug must have an insulator tip with a large surface, that is, the spark plug must have a long insulator tip. It is difficult, however, to find a suitable compr~mise since the use of longer insulating tips can be realized only if the heat generated upon ignition in the ignition space of the engine can also be conducted away since, otherwise, the longer tips may tend to cause self-ignition due to the glow of the t~p, or deposits thereon. It has already been proposed to conduct heat away rapidly and effectively over the center electrode by so c~nstructing the center ~:, ' I .
electrode that it is easily heat conductive, that is, I
I
consists of a material having a high heat conductivity.
Composite electrodes have been made in which silver is ` used as a matrix material and as the highly heat conductive ~-~ 25 substance, in which at least one filament or strand of ` nickel is embedded. The fi~mentsor strandæ of nickel ' ` ' .
~ ` ` ~4~
~0463ti9 ~
tend to reduce corrosion, and burn-off of the electrode, 80 that the distance between the center electrode and the counter electrode remains essentially constant. While the solution is technically good, the cost of such electrodes is high since sllver i8 expensive.
It ls an ob~ect of the present invention to provide a spark plug with a composite electrode which permits use of a long insulating tip, and which has the advantages of composite electrodes of high heat conductivity without, however, requiring the expensive metal of silver as a matrix material.
Sub~ect matter of the present invention: Briefly, the present invention provides a spark plug for use in internal combustion engines having a housing shaped for assembly in the engine, an insulator sleeve extending through the housing, an essentially cylindrical central electrode extending through the insulator, and a counter electrode secured to the housing, wherein the central electrode comprises an electrode tip located opposite the counter electrode to provide for spark discharge from an end face of the tip to the counter electrode and formed as a composite structure having an outer ~acket of corrosion re8i8tant materlal, at least one strand of corrosion resistant -- -electrically conductive material, and a matrix filler material fllling the ~acket and within which the at least one strand is embeddet; and wherein the matrix filler material comprises a material selected from the group consisting of copper; a corrosion resistant copper alloy, and forms between 5% and 50%, by volume, of the central electrode, and the ~acket is ~
: . .:
essentially a cylindrical cover extending around the outer circumference of the filler material leaving the end face exposed ;~
and facing the counter electrode and which end face comprises the matrix filler and the at least one strand.
' ~, .
-dap/~
B
~)46369 It has been found, surprisingly, that copper or corrosion resistant, slightly alloyed copper can be used as the matrix material although, without protection by a jacket, it could not be used due to the tendency to corrode when exposed to hot gases. The-copper, when mb/ d~ 5a - `
.~".
: -. , . , ~ . ~ ,- .,. - ,. .. .. ~ , . . . .
~04~369 I
jacketed and having the filaments or strands of corrosion resistant material embedded therein is eminently suitable to conduct heat away from the electrode tip, and from the insulator, while being highly electrically conductive, and permitting construction of an electrode which is at least half and usually less than half as expensive as a composite elect~ode including silver as the matrix material.
The number of filaments embedded in the matrix can vary widely. Up to 200 filaments or strands can be embedded in spark plugs of conventional size for automotive-type engines; as the number of strands increases beyond about 20 or so strands for the ordinary automotive-type -electrode, the corrosion tendency within the electrode, and the price of the electrode increase. In a preferred form, the strands or filaments are so located within the copper matrix material that the strands do not touch each other, and are essentially uniformly distributed over the cross-sectional area of the electrode. If the strands touch ¦
~ ~ .
` ~ ~ 20 each other, then the danger of corrosion is increased.
It has been found, desirably and surprisingly, that the ignition voltage necessary for a spark at the electrodes i8 lower than with spark plug electrodes without the filament or strand inserts, given a fixed electrode gap.
The invention will be described by way of example with reference to the accompanying drawings) wherein:
; , . .. !
.i: . I
.. , ..... ~ .. ...
.` . . . . . - , . . .. . :
Fig. l is a side view, partly perspective and partly in section, of a spark plug, to an enlarged scale;
Fig. ~ is a cross-sectional view along line I-I
of the center electrode of Fig. l, to a still greater scale;
Fig. 3 is a cross-sectional view along line I-I of Fig. l of a modiication of an electrode to essentially the same scale as Fig. 2;
and Fig. 4 is a longitudinal cross-sectional view along line III-III of the electrode of Fig. 3.
The spark plug of Fig. l has an electrical insulator body 12, made of ceramic material, through which a central electrode extendQ. The outer connecting portion 10 is -suitably shaped to receive an electrical connector, as well known in the art, and connects with a center elsctrode 11, which passes through the insulator 12. The insulator ~ 12 is sealed into a housing 13, made of metal, and formed ; ~ ~ with a screw thread 15 for insertion into the engine block of an internal combustion engine, not shown. The metal housing has an inner extension 14 forming the ground or ~ counter electrode. The portion of the insulator 12 which extends into the combustion area forms a tip 16. The insulator 12 is a unitary body and, including the insulator , tip 16, is made of a ceramic based on aluminum oxide, with additives of~glassy substance and fired to havo high ~ ` 25 ~ mechanical str~ngth in special furnaces at high -'`Sr~ ' ', temperatures~
- . , ~ 7-~046369 The center electrode, in accordance with the present invention, has a diameter of a~out 2.4 mm at the tip portion. The electrode 11 is essentially cylindrical has a jacket 17 of abbut 0.35 mm wall thickness. The jacket 17 is made of an alloy having (by weight) 96% nickel as corrosion resistant material to which such elements as chromium, manganese, or silicon have been added to improve the corrosion resistance. The jacket 17 may also be made of other corrosion resistant alloys having a nickel, chromium or cobalt base. This jacket 17, the thickness of which may vary between 0.2 and 0,5 mm, surrounds and protects the matrix material 18 but leaves the end face free Matrix material 18 is subject to attack by corrosion by hot gases and, in accordance with the present invention, is made of copper~ or a copper-base alloy. Seven strands l9 of a mat-erial which essentially may be the same material as the jacket 17 are embedded in the copper or copper-base alloy matrix 18, The diameter of the strands 19 is approximately 0,3 mm. The strands are so arranged in the matrix that they provide a center strand about which the other six strands are located with uniform spacing, The center strand extends axially in the electrode 11, The strands 19 are so spaced that they do not touch each other. This particular arrangement of the 8trands 19 has been found to be advantageous in operation.
Depending on the use to which the spark plug is to be put, a larger or lesser ~umber of strands can be used~; up to 200 ~rands mb/ ~ - 8 -. ~
. .
., .
~046369 can be embedded in the matrix 18. It has been found, however, that as the number of strands 19 increases, corrosion ~lso increases on the center electrode 11.
Additionally, the manufacturing cost of making the center electrode increases. It is, therefore, desirable to keep the number of strands 19 at or below twenty-one. The electrode 11 can have a copper content, in accordance with the invention, which is between ~and 50% by volume;
preferably, the copper content is about 30% by volume.
Corrosion resistant, low alloyed copper can be used as the matrix material 18, for example by the addition~of o.1%to 1.5% chromium,or zirconium (by weight). Such additions to the copper improve the effect of the strands 19 in the matrix material. The end surface 20 of the center electrode does not require any additional protection again~t corro~ion, thus permitting inexpensive mass production of the center electrodes 11, starting from a wire base.
Various modifications may be made; Figs. 3 and 4 illustrate a center electrode 11 ' which, instead of a ~1 20 central core and surrounding strands is formed with an!-enlarged single central wire 19' of nickel, embedded in a matrix 18' of copper or copper alloy. The center wire 19' has a diameter of about 0.9 mm and extends axially centrally within the electrode 11'. In all other respects, that is, .
- 25 dimensions of the electrode as such, the jacket,and the entire spark plug arrangement, reference is made to the .
. ~ ~ .
g_ .
.-, .. ..
: , -embodiments of Figs. 1 and 2.
The jacket 17 (Fig. 2), 17~ (Figs. 3, 4) as well as the str~nds 19, or the wire 19', may be made of nickel or other corrosionrasistant alloys based on nicke~ chromiwm, or cobalt. Examples: "Inconel 600" (trademark) which includes about 75% nickel, 15% chromium and 10% iron, a chromium-base corrosion resistant material may have 20%
chromium, 5% aluminum, and 75% iron; a cobalt-base material can be "Vakumelt ATS 115" (trademark) which has 70% cobalt, 20% chromium and 10% nickel.
In a preferred form, the center electrode has 20% to 40YO by volume copper, or copper-base alloy, although the range is not critical. ~he jacket and strands, or wire embedded in the matrix 18, for manufacturing reasons, preferably are of the same material, but this i5 not a requirement; in a suitable form, they contain at least 95%, by weight, nickel. ~he copper matrix material must be~
protected at the outer circumference due to the tendency to corrode when used as electrodes in spark plugs; without the insert of additional corrosion resistant material, however, the electrode is not suitable, and the combination of the jacket, and tha embedded strands (Fig. 2) or central wire (Figs. ~, 4) results in an electrode which is eminently suitable as a spark plug electrode, without corroding, but still providing the necessary heat and electrical conductivity, permitting rapid heating of the .
. . . .
: :
~0463~9 insulator tip 16 but not heating of the tip 16 to a temperature which might cause undesired ignition due to deposit of carbonized or glowing substances. Electrodes of the di~ensions given and having either seven strands (Fig. 2) or a central- strand, or wire (Figs. 3, 4) have been found to have excellent properties and long operating time, using jackets 17, 17' of about 0.3 to 0.4 mm,thick-ness, preferably about 0.35 mm thickness.
Various chan~es and modifications may be made within the scope of the inventive concept. In the specifiacation and claims hereof, the term "copper" is deemed to include copper and minute quantities of alloying constituents, for example chromium or zirconium.
A preferred material for the jacket 17, or the filament or strands 19 contains 95 % nickel, 1,8 %
chromium, 2 % mangsnese snd 0,5 1 silioon (7y ~eight).
,~- 11 -' '^ ~: ' - .
.
.: . , .. . .. - I
~. ,. . ~, The center electrode 11 can be made as a separate tip to be inserted in a central conductor joined to the terminal 10 and extending through the length of the electrode, or the electrode, as such, can extend up to and inwardly Or a terminal element 10. If the electrode 11 is inserted into a central conductor, then the central conductor may consist of any suitable material, well-known in the art, and which can readily be sealed into the ceramic material 12 forming the insulator. The tip o~ the electr~de is then preferably inserted into the central conductor sealed through the insulator 12 before embedding the central conductor and the terminal 10 in the ceramic 12 and assembling the ceramic into the housing or metal holder 13.
However, in the pre~erred embodiment, the center electrode 11 is made as a separate tip to be connected by an electrically conducting gla~s seal twell-known in the art) to a central conductor which is joined to the terminal 10; also in this case the central conductor - .
may consist of any suitable material well-known in the art. The tip of the electrode is then inserted and : I
;i mechanically fixed in the insulator 12, the glass brought : . I
; as a powder upon the electrode tip part inside the ,-insulator 12, the insulator 12 with the electrode tip and the glas~ powder is`then heated to melt the glass powder and after that the central conductor is fed into llA-' ' ' I ` ' . . ' ` ' ' "' ' ' ': ' ' - ~
the molten glass; after cooling the electrode ti~
will be electricall~ connected with the central conductor and will be embedded gastight in the insulator 12 (see e.g. US-Patent 3 360 676).
- , I ..
, : - 11B -~':`.' j .
. i ~.~: . i .~ :
~ !
........... ~... . . . . . .
,.. . ,~ ` , . ' ' .: .
Various types of internal combustion engine~ used in automotive power plants, to provide power forvarious types of appliances, and the like, require different types of spark plugs. It is difficult to provide a single type of spark plug for different motors, and even for motors which are of essentially similar construction, in view of~the different power loading on the motor, different operatian, compression ratio, speed, cooling, carburation, and type of fuel supply. If a single type of spark plug would be used for various engines, or for an engine subject to different operating conditions, then such a spark plug might, under some operating conditions, become too hot ~` while, under other operating conditions, or with different motors, would have too low an average temperature. If the spark plug becomes too hot, then the fuel-air mixture can self-ignite on the elements of the spark plugs extending into the combustion space of the engine, resulting in ignition due to glow of the spark plug, and in misfires.
If the spark plug operates too cool, then the insulator tip ~ ourrounding the center electrode, extending into the i !
:` ` . I
., i combustion ~pace of the engine, would rapidly become contaminated by combustion residues. Misfires, in the sense of failure of sparking, would result due to spurious electrical paths through combustion residues or deposits.
Thus, the spark plug to be used in the internal combustion engine ~ust be matched to the engine, so that the plug, in a specific motor, does not become too hot, nor remain too cold. This requires spark plugs with different load characteristics. These different load characteristic~ are evaluated by designation by a heat number, associated with each spark plug. The heat number~ or heat value of a spark plug, expressed as an arbitrary number, characterizes the resistance of the spark plug with respect to overheating: ;
a higher heat number permits higher loading of the spark plug without danger of spurious ignition due to glowing of the spark plug but, on the other hand, it has a higher tendency to become contaminated, since the self-cleaning temperature is not reached as rapidly upon starting of a c~ld engine and is easily passed in downward direction upon throttling of the motor.
Spark plugs can be designed to have various heat numbers by suitably shaping the insulator surface which has '' to accept the heat to which the spark plug is subjected.
Assuming an egual diameter for a specific spark plug, that 25~ is, the same diameter of the spark plug housing, the length of the inculator tip adjacent tho electrode tip has a ~ ~ ..................................................... I
. , . ~ . .
definite bearing on the heat number. Spark plugs with a high heat value have short insulator tips; spark plugs with a low heat ~wmber have long insulator tips. The spark plug must reach a temperature of about 500C in order to be self-cleaning, that is, to spontaneously burn off deposits such as soot, oil, carbonized oil,or the like, which may deposit on the insulator of the spark plug. The burning of these deposits should be sufficiently effective to prevent short circuits for the spark current being supplied to the electrode. To permit such burn-off, the spark plug must have an insulator tip with a large surface, that is, the spark plug must have a long insulator tip. It is difficult, however, to find a suitable compr~mise since the use of longer insulating tips can be realized only if the heat generated upon ignition in the ignition space of the engine can also be conducted away since, otherwise, the longer tips may tend to cause self-ignition due to the glow of the t~p, or deposits thereon. It has already been proposed to conduct heat away rapidly and effectively over the center electrode by so c~nstructing the center ~:, ' I .
electrode that it is easily heat conductive, that is, I
I
consists of a material having a high heat conductivity.
Composite electrodes have been made in which silver is ` used as a matrix material and as the highly heat conductive ~-~ 25 substance, in which at least one filament or strand of ` nickel is embedded. The fi~mentsor strandæ of nickel ' ` ' .
~ ` ` ~4~
~0463ti9 ~
tend to reduce corrosion, and burn-off of the electrode, 80 that the distance between the center electrode and the counter electrode remains essentially constant. While the solution is technically good, the cost of such electrodes is high since sllver i8 expensive.
It ls an ob~ect of the present invention to provide a spark plug with a composite electrode which permits use of a long insulating tip, and which has the advantages of composite electrodes of high heat conductivity without, however, requiring the expensive metal of silver as a matrix material.
Sub~ect matter of the present invention: Briefly, the present invention provides a spark plug for use in internal combustion engines having a housing shaped for assembly in the engine, an insulator sleeve extending through the housing, an essentially cylindrical central electrode extending through the insulator, and a counter electrode secured to the housing, wherein the central electrode comprises an electrode tip located opposite the counter electrode to provide for spark discharge from an end face of the tip to the counter electrode and formed as a composite structure having an outer ~acket of corrosion re8i8tant materlal, at least one strand of corrosion resistant -- -electrically conductive material, and a matrix filler material fllling the ~acket and within which the at least one strand is embeddet; and wherein the matrix filler material comprises a material selected from the group consisting of copper; a corrosion resistant copper alloy, and forms between 5% and 50%, by volume, of the central electrode, and the ~acket is ~
: . .:
essentially a cylindrical cover extending around the outer circumference of the filler material leaving the end face exposed ;~
and facing the counter electrode and which end face comprises the matrix filler and the at least one strand.
' ~, .
-dap/~
B
~)46369 It has been found, surprisingly, that copper or corrosion resistant, slightly alloyed copper can be used as the matrix material although, without protection by a jacket, it could not be used due to the tendency to corrode when exposed to hot gases. The-copper, when mb/ d~ 5a - `
.~".
: -. , . , ~ . ~ ,- .,. - ,. .. .. ~ , . . . .
~04~369 I
jacketed and having the filaments or strands of corrosion resistant material embedded therein is eminently suitable to conduct heat away from the electrode tip, and from the insulator, while being highly electrically conductive, and permitting construction of an electrode which is at least half and usually less than half as expensive as a composite elect~ode including silver as the matrix material.
The number of filaments embedded in the matrix can vary widely. Up to 200 filaments or strands can be embedded in spark plugs of conventional size for automotive-type engines; as the number of strands increases beyond about 20 or so strands for the ordinary automotive-type -electrode, the corrosion tendency within the electrode, and the price of the electrode increase. In a preferred form, the strands or filaments are so located within the copper matrix material that the strands do not touch each other, and are essentially uniformly distributed over the cross-sectional area of the electrode. If the strands touch ¦
~ ~ .
` ~ ~ 20 each other, then the danger of corrosion is increased.
It has been found, desirably and surprisingly, that the ignition voltage necessary for a spark at the electrodes i8 lower than with spark plug electrodes without the filament or strand inserts, given a fixed electrode gap.
The invention will be described by way of example with reference to the accompanying drawings) wherein:
; , . .. !
.i: . I
.. , ..... ~ .. ...
.` . . . . . - , . . .. . :
Fig. l is a side view, partly perspective and partly in section, of a spark plug, to an enlarged scale;
Fig. ~ is a cross-sectional view along line I-I
of the center electrode of Fig. l, to a still greater scale;
Fig. 3 is a cross-sectional view along line I-I of Fig. l of a modiication of an electrode to essentially the same scale as Fig. 2;
and Fig. 4 is a longitudinal cross-sectional view along line III-III of the electrode of Fig. 3.
The spark plug of Fig. l has an electrical insulator body 12, made of ceramic material, through which a central electrode extendQ. The outer connecting portion 10 is -suitably shaped to receive an electrical connector, as well known in the art, and connects with a center elsctrode 11, which passes through the insulator 12. The insulator ~ 12 is sealed into a housing 13, made of metal, and formed ; ~ ~ with a screw thread 15 for insertion into the engine block of an internal combustion engine, not shown. The metal housing has an inner extension 14 forming the ground or ~ counter electrode. The portion of the insulator 12 which extends into the combustion area forms a tip 16. The insulator 12 is a unitary body and, including the insulator , tip 16, is made of a ceramic based on aluminum oxide, with additives of~glassy substance and fired to havo high ~ ` 25 ~ mechanical str~ngth in special furnaces at high -'`Sr~ ' ', temperatures~
- . , ~ 7-~046369 The center electrode, in accordance with the present invention, has a diameter of a~out 2.4 mm at the tip portion. The electrode 11 is essentially cylindrical has a jacket 17 of abbut 0.35 mm wall thickness. The jacket 17 is made of an alloy having (by weight) 96% nickel as corrosion resistant material to which such elements as chromium, manganese, or silicon have been added to improve the corrosion resistance. The jacket 17 may also be made of other corrosion resistant alloys having a nickel, chromium or cobalt base. This jacket 17, the thickness of which may vary between 0.2 and 0,5 mm, surrounds and protects the matrix material 18 but leaves the end face free Matrix material 18 is subject to attack by corrosion by hot gases and, in accordance with the present invention, is made of copper~ or a copper-base alloy. Seven strands l9 of a mat-erial which essentially may be the same material as the jacket 17 are embedded in the copper or copper-base alloy matrix 18, The diameter of the strands 19 is approximately 0,3 mm. The strands are so arranged in the matrix that they provide a center strand about which the other six strands are located with uniform spacing, The center strand extends axially in the electrode 11, The strands 19 are so spaced that they do not touch each other. This particular arrangement of the 8trands 19 has been found to be advantageous in operation.
Depending on the use to which the spark plug is to be put, a larger or lesser ~umber of strands can be used~; up to 200 ~rands mb/ ~ - 8 -. ~
. .
., .
~046369 can be embedded in the matrix 18. It has been found, however, that as the number of strands 19 increases, corrosion ~lso increases on the center electrode 11.
Additionally, the manufacturing cost of making the center electrode increases. It is, therefore, desirable to keep the number of strands 19 at or below twenty-one. The electrode 11 can have a copper content, in accordance with the invention, which is between ~and 50% by volume;
preferably, the copper content is about 30% by volume.
Corrosion resistant, low alloyed copper can be used as the matrix material 18, for example by the addition~of o.1%to 1.5% chromium,or zirconium (by weight). Such additions to the copper improve the effect of the strands 19 in the matrix material. The end surface 20 of the center electrode does not require any additional protection again~t corro~ion, thus permitting inexpensive mass production of the center electrodes 11, starting from a wire base.
Various modifications may be made; Figs. 3 and 4 illustrate a center electrode 11 ' which, instead of a ~1 20 central core and surrounding strands is formed with an!-enlarged single central wire 19' of nickel, embedded in a matrix 18' of copper or copper alloy. The center wire 19' has a diameter of about 0.9 mm and extends axially centrally within the electrode 11'. In all other respects, that is, .
- 25 dimensions of the electrode as such, the jacket,and the entire spark plug arrangement, reference is made to the .
. ~ ~ .
g_ .
.-, .. ..
: , -embodiments of Figs. 1 and 2.
The jacket 17 (Fig. 2), 17~ (Figs. 3, 4) as well as the str~nds 19, or the wire 19', may be made of nickel or other corrosionrasistant alloys based on nicke~ chromiwm, or cobalt. Examples: "Inconel 600" (trademark) which includes about 75% nickel, 15% chromium and 10% iron, a chromium-base corrosion resistant material may have 20%
chromium, 5% aluminum, and 75% iron; a cobalt-base material can be "Vakumelt ATS 115" (trademark) which has 70% cobalt, 20% chromium and 10% nickel.
In a preferred form, the center electrode has 20% to 40YO by volume copper, or copper-base alloy, although the range is not critical. ~he jacket and strands, or wire embedded in the matrix 18, for manufacturing reasons, preferably are of the same material, but this i5 not a requirement; in a suitable form, they contain at least 95%, by weight, nickel. ~he copper matrix material must be~
protected at the outer circumference due to the tendency to corrode when used as electrodes in spark plugs; without the insert of additional corrosion resistant material, however, the electrode is not suitable, and the combination of the jacket, and tha embedded strands (Fig. 2) or central wire (Figs. ~, 4) results in an electrode which is eminently suitable as a spark plug electrode, without corroding, but still providing the necessary heat and electrical conductivity, permitting rapid heating of the .
. . . .
: :
~0463~9 insulator tip 16 but not heating of the tip 16 to a temperature which might cause undesired ignition due to deposit of carbonized or glowing substances. Electrodes of the di~ensions given and having either seven strands (Fig. 2) or a central- strand, or wire (Figs. 3, 4) have been found to have excellent properties and long operating time, using jackets 17, 17' of about 0.3 to 0.4 mm,thick-ness, preferably about 0.35 mm thickness.
Various chan~es and modifications may be made within the scope of the inventive concept. In the specifiacation and claims hereof, the term "copper" is deemed to include copper and minute quantities of alloying constituents, for example chromium or zirconium.
A preferred material for the jacket 17, or the filament or strands 19 contains 95 % nickel, 1,8 %
chromium, 2 % mangsnese snd 0,5 1 silioon (7y ~eight).
,~- 11 -' '^ ~: ' - .
.
.: . , .. . .. - I
~. ,. . ~, The center electrode 11 can be made as a separate tip to be inserted in a central conductor joined to the terminal 10 and extending through the length of the electrode, or the electrode, as such, can extend up to and inwardly Or a terminal element 10. If the electrode 11 is inserted into a central conductor, then the central conductor may consist of any suitable material, well-known in the art, and which can readily be sealed into the ceramic material 12 forming the insulator. The tip o~ the electr~de is then preferably inserted into the central conductor sealed through the insulator 12 before embedding the central conductor and the terminal 10 in the ceramic 12 and assembling the ceramic into the housing or metal holder 13.
However, in the pre~erred embodiment, the center electrode 11 is made as a separate tip to be connected by an electrically conducting gla~s seal twell-known in the art) to a central conductor which is joined to the terminal 10; also in this case the central conductor - .
may consist of any suitable material well-known in the art. The tip of the electrode is then inserted and : I
;i mechanically fixed in the insulator 12, the glass brought : . I
; as a powder upon the electrode tip part inside the ,-insulator 12, the insulator 12 with the electrode tip and the glas~ powder is`then heated to melt the glass powder and after that the central conductor is fed into llA-' ' ' I ` ' . . ' ` ' ' "' ' ' ': ' ' - ~
the molten glass; after cooling the electrode ti~
will be electricall~ connected with the central conductor and will be embedded gastight in the insulator 12 (see e.g. US-Patent 3 360 676).
- , I ..
, : - 11B -~':`.' j .
. i ~.~: . i .~ :
~ !
........... ~... . . . . . .
,.. . ,~ ` , . ' ' .: .
Claims (16)
ROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. Spark plug for use in internal combustion engines having a housing shaped for assembly in the engine, an insulator sleeve extending through the housing, an essentially cylindrical central electrode extending through the insulator, and a counter electrode secured to the housing, wherein said central electrode comprises an electrode tip located opposite said counter electrode to provide for spark discharge from an end face of the tip to the counter electrode and formed as a composite structure having an outer jacket of corrosion resistant material, at least one strand of corrosion resistant electrically conductive material, and a matrix filler material filling said jacket and within which said at least one strand is embedded; and wherein said matrix filler material comprises a material selected from the group consisting of copper; a corrosion resistant copper alloy, and forms between 5X and 50%, by volume, of the central electrode, and the jacket is essentially a cylindrical cover extending around the outer circumference of the filler material leaving said end face ` exposed and facing the counter electrode and which end face comprises said matrix filler and said at least one strand.
2. Spark plug according to claim 1, wherein up to about two hundred strands are embedded in the matrix material.
3. Spark plug according to claim 1, wherein the jacket comprises a corrosion resistant alloy having a base selected from the group consisting of nickel, chromium, and cobalt.
4. Spark plug according to claim 1, wherein the strands embedded in the matrix material are essentially uniformly distributed throughout the cross-section of the matrix material and are located therein spaced from each other so that they will not contact each other within the matrix.
5. Spark plug according to claim 1, wherein the central electrode comprises 20% to 40%, per volume, of copper as matrix material.
6. Spark plug according to claim 1, wherein the jacket comprises a material having at least 95%, by weight, of nickel.
7. Spark plug according to claim 1, wherein the strands comprise a material of at least 95% nickel.
8. Spark plug according to claim 1, wherein the material of the jacket and of the strands is similar.
9. Spark plug according to claim 1, wherein the central electrode comprises approximately 30% copper, by volume, as material for the matrix.
10. Spark plug according to claim 1, wherein the central electrode comprises a center strand and a plurality of strands located circumferentially around the center, all said strands being embedded in the matrix material, the number of said strands not exceeding twenty-one.
11. Spark plug according to claim 10, wherein seven strands are provided.
12. Spark plug according to claim 1, wherein a strand extends axially centrally through the central electrode, embedded in said matrix filler material.
13. Spark plug according to claim 1, wherein the wall thickness of the jacket is about 0.3 to 0.4 mm.
14. Spark plug according to claim 1, wherein said corrosion resistant material forming at least one of said jacket or the strand comprises: about 75% nickel, 15% chromium, 10%
iron.
iron.
15. Spark plug according to claim 11 wherein said corrosion resistant material forming at least one of said jacket or the strand comprises: about 20% chromium, 5% aluminum, 75%
iron.
iron.
16. Spark plug according to claim 1, wherein said corrosion resistant material forming at least one of said jacket or the strand comprises: about 70% cobalt, 20% chromium, 10%
nickel.
nickel.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19742444509 DE2444509A1 (en) | 1974-09-18 | 1974-09-18 | Centre electrode of sparking plug for IC engine - consists of bundle of nickel alloy based fibres encased in nickel alloy sheath |
| DE19752516727 DE2516727C3 (en) | 1975-04-16 | 1975-04-16 | Spark plug electrode |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1046369A true CA1046369A (en) | 1979-01-16 |
Family
ID=25767714
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA235,536A Expired CA1046369A (en) | 1974-09-18 | 1975-09-16 | Internal combustion engine spark plug having composite electrode structure |
Country Status (11)
| Country | Link |
|---|---|
| JP (2) | JPS5155832A (en) |
| AR (1) | AR203975A1 (en) |
| BR (1) | BR7505989A (en) |
| CA (1) | CA1046369A (en) |
| DD (1) | DD120570A5 (en) |
| ES (1) | ES441028A1 (en) |
| FR (1) | FR2285735A1 (en) |
| GB (1) | GB1514195A (en) |
| IT (1) | IT1042580B (en) |
| SE (1) | SE401061B (en) |
| SU (1) | SU673208A3 (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2451648A1 (en) * | 1979-03-13 | 1980-10-10 | Texas Instruments Inc | Spar plug middle electrode has corrosion and erosion resistant core - with sheath of higher thermal conductivity |
| US6533629B1 (en) | 1999-07-13 | 2003-03-18 | Alliedsignal Inc. | Spark plug including a wear-resistant electrode tip made from a co-extruded composite material, and method of making same |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR570141A (en) * | 1923-08-25 | 1924-04-24 | Improvements to spark plugs for internal combustion engines | |
| US2261436A (en) * | 1940-05-24 | 1941-11-04 | Edmund R Week Jr | Spark plug and method of making the same |
| GB588197A (en) * | 1944-02-01 | 1947-05-16 | Mallory Metallurg Prod Ltd | Improvements in and relating to sparking plugs |
| US2470033A (en) * | 1945-11-27 | 1949-05-10 | Mallory & Co Inc P R | Spark plug |
| US2942135A (en) * | 1958-01-31 | 1960-06-21 | Eli Ladenheim | Spark plug |
| JPS56920B2 (en) * | 1972-04-04 | 1981-01-10 |
-
1975
- 1975-05-19 GB GB21132/75A patent/GB1514195A/en not_active Expired
- 1975-08-22 FR FR7526067A patent/FR2285735A1/en active Granted
- 1975-09-08 AR AR260299A patent/AR203975A1/en active
- 1975-09-16 CA CA235,536A patent/CA1046369A/en not_active Expired
- 1975-09-16 DD DD188372A patent/DD120570A5/xx unknown
- 1975-09-16 IT IT27272/75A patent/IT1042580B/en active
- 1975-09-17 ES ES441028A patent/ES441028A1/en not_active Expired
- 1975-09-17 SE SE7510391A patent/SE401061B/en unknown
- 1975-09-17 SU SU752172435A patent/SU673208A3/en active
- 1975-09-17 JP JP50112509A patent/JPS5155832A/en active Pending
- 1975-09-17 BR BR7505989*A patent/BR7505989A/en unknown
-
1983
- 1983-09-26 JP JP1983147740U patent/JPS5984785U/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| ES441028A1 (en) | 1977-07-01 |
| GB1514195A (en) | 1978-06-14 |
| FR2285735B1 (en) | 1979-05-18 |
| AU8320975A (en) | 1977-01-20 |
| BR7505989A (en) | 1976-08-03 |
| JPS5155832A (en) | 1976-05-17 |
| SE401061B (en) | 1978-04-17 |
| IT1042580B (en) | 1980-01-30 |
| AR203975A1 (en) | 1975-10-31 |
| SE7510391L (en) | 1976-03-19 |
| FR2285735A1 (en) | 1976-04-16 |
| DD120570A5 (en) | 1976-06-12 |
| SU673208A3 (en) | 1979-07-05 |
| JPS5984785U (en) | 1984-06-08 |
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