CA1252830A - Glow plug having a metallic silicide resistive film heater - Google Patents
Glow plug having a metallic silicide resistive film heaterInfo
- Publication number
- CA1252830A CA1252830A CA000503183A CA503183A CA1252830A CA 1252830 A CA1252830 A CA 1252830A CA 000503183 A CA000503183 A CA 000503183A CA 503183 A CA503183 A CA 503183A CA 1252830 A CA1252830 A CA 1252830A
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- Canada
- Prior art keywords
- resistive layer
- internal
- metallic
- external
- substrate
- 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
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Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23Q—IGNITION; EXTINGUISHING-DEVICES
- F23Q7/00—Incandescent ignition; Igniters using electrically-produced heat, e.g. lighters for cigarettes; Electrically-heated glowing plugs
- F23Q7/001—Glowing plugs for internal-combustion engines
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- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Resistance Heating (AREA)
Abstract
21JRI0285/0216m 600-84-0040 Abstract:
A GLOW PLUG HAVING A METAL SILICIDE
RESISTIVE FILM HEATER
A glow plug having a heater member formed by depositing a metallic-silicide layer on the internal and external surfaces of a cylindrical ceramic substrate.
The metallic-silicide layer deposited on the external surface of the substrate is electrically connnected to a metal shell which supports one end of the heater member. An axial electrode disposed in the shell is electrically connected to the metallic-silicide layer disposed on the internal surface of the substrate and further serves to lock the heater member in the shell.
A GLOW PLUG HAVING A METAL SILICIDE
RESISTIVE FILM HEATER
A glow plug having a heater member formed by depositing a metallic-silicide layer on the internal and external surfaces of a cylindrical ceramic substrate.
The metallic-silicide layer deposited on the external surface of the substrate is electrically connnected to a metal shell which supports one end of the heater member. An axial electrode disposed in the shell is electrically connected to the metallic-silicide layer disposed on the internal surface of the substrate and further serves to lock the heater member in the shell.
Description
The invention i3 related to the field of electric heaters for the ignition of hydrocarbon fuels and in particular to a glow plug for internal combustion engines havirlg a metallic silicide resistive film heater.
The invention is related to the glow plug described in applicant's U.S. Patent No. 4,582,981, issued April 15, 1986 entitled "Glow Plug Having a Resistive Surface Film Heater".
Prior Art Electrically energized glow plugs are currently used in compression ignited or Diesel type internal combustion engines to assist in the ignition of compressed air/fuel mixtures during cold starts. In particular glow plugs are essential in the Northern states during the winter months when the ambient temperature falls below 10C.
In U.S. Patent No. 4,582,981 a novel heater con~iguration was disclosed in which a noble metal resistive film was dis-posed along the external and internal surfaces of a cylindrical ceramic substrate. Although this type of glow plug has ~ S
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.
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The invention is related to the glow plug described in applicant's U.S. Patent No. 4,582,981, issued April 15, 1986 entitled "Glow Plug Having a Resistive Surface Film Heater".
Prior Art Electrically energized glow plugs are currently used in compression ignited or Diesel type internal combustion engines to assist in the ignition of compressed air/fuel mixtures during cold starts. In particular glow plugs are essential in the Northern states during the winter months when the ambient temperature falls below 10C.
In U.S. Patent No. 4,582,981 a novel heater con~iguration was disclosed in which a noble metal resistive film was dis-posed along the external and internal surfaces of a cylindrical ceramic substrate. Although this type of glow plug has ~ S
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.
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excellent performance characteristics which are superior to glow plugs currently used in automotive vehicles, difficulties have been experienced in the deposition of satisfactory noble metal resistive films due to micro-irregularities on the surfaces of the ceramic substrate and the thinness of the noble metal films required to achieve the desired resistivity. The ob~ect of the invention is the substitution of a metallic-silicide film for the noble metal film which ln because of the higher resistivity of the metallic silicides permits the use of thicker resistive films which are less sensitive to the micro-irregularities of the ceramic structure, have a higher melting temperature which permits the glow plug to be operated at higher temperatures, and have a larger positive coefficient of resistance potentially making the glow plug self-limiting reducing the requirements of the attendant controller.
The use of metallic-silicides for heater elements is well-known in the art. The Kanthal Corporation of Bethel, Connecticut makes a variety of heater elements using metal silicides as the resistive element. These heater elements take the form of a metallic silicide as were disclosed by Giler in U.S. Patent No. 3,912,905 or a layer of metallic-silicide formed over an insulating or ceramic layer disposed over a metal wire for \~J; //5a n structural strength as disclosed by Wilson in U.S.
Patent No. 3,810,734. Suzuki et al in U.S. Patent No.
~,437,440 discloses a glow plug having a tubular 30~ molybdenum disilicide (MoSi2) element in which electrical contact is made between the shell and an axial electrode contacting the closed end of the tubular heatlng element.
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Summary of the Invention The invention i~ a glow plug for internal combustion engines of the type having a glow plug of the type having a cylindrical metal shell, and an axial electrode dispo~ed ;n the metal shell, in~ulator means supporting the axial electrode concentrically in ~he metal shell and electrically insulating it there~rom, and a heater member electrically connected between the metal shell and the axial electrode, the improvement wherein the heater member comprises: a hollow open-ended cylindrical ceramic substrate having an internal surface, and an external surface, the ~ub~trate having an internal portion ~ecured in the shell between one end of the ~hell and one end of the axial electrode and an external portion protruding externally from the shell, the ceramic substrate having micro-irregularities on the internal and external surfaces; and a continuous metallic-silicide resistive layer disposed along the internal and external surfaces of the cylindrical substrate and around the end of the external portion to form a hollow cylindrical heater element open at the end of the external portion, the portion of the resistive layer disposed along the external surface of the ~ub~trate being electrically connected to the metal shell and the portion of the resistive layer disposed along the internal surface of the substrate being electrically connected to the axial electrode, the metallic-silicide resistlve layer being substantially uneffected by the micro-irregularities on the internal and external surfaces to provide a cold resistance rm/
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of from 0.2 to 0.6 ohmg to the flow of electrical current, the resi3tive layer responding to five amperes of electrical current to develop a temperature of at least 800C within five seconds, the metallic silicide resistive layer having a positive coefficient of resistance to provide for ~elf limiting which reduces the operating requirements of a controller.
The advantages of the glow plug is that the interior of the cylindrically shaped heater member ~orms an extremely hot cul-de-sac which is not cooled by the impinging air/fuel mixture. Another advantage is that the metallic-silicide resistive layer iq relatively in~en~itive to oxidation and the corrosive atmosphere inside the engine. Another advantage i8 that the low mass of the heater member permits the glow plug to reach an operating temperature in less than 5 seconds with an applied power of less than 60 watts. These and other advantages of the glow plug will become more apparent from a reading of the specification in conjunction with the figures.
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~' 21JRI02~5/0216m 600-8~-0040 8rief Description of the Drawings FIGURE 1 is a cross-sectional view of the glow plug embodying the cylindrical ceramic heater member.
5FIGURE 2 is a cross-sectional view of a first embodiment of the cylindrical heater member.
FIGURE 3 is a cross-sectional view of a second embodiment of the cylindrical heater member.
FIGURE 4 is a cross-sectional view of an embodiment of the heater member having the interior of the ceramic filled with a metallic silicide.
FIGURE 5 is a cross-sectional view of an embodiment of the heater member having the cylindrical substrate formed around the axial electrode.
15FIGUR~ 6 is a cross-sectional view of an embodiment of the heater member having the interior of the cyllndrical substrate filled with alumina.
~etailed Description of the Invent on A cross-sectional view of the glow plug is shown in Figure 1. The glow plug comprises a cylindrical metal shell 12 having an internal bore 14. Formed at one end of the shell 12 is a contact seat 16 defining a heater aperture 18 . Located in the internal bore 14 is a heater member 20 having a resistive metallic-silicide surface~film heater element 24 coated or disposed on at least~ one surface of a non-conductive cylindrical substraté 22 as shall be described hereinafter. ~he 30 ;non-~conductive substrate 22 is preferably a high ~temperature ceramic, such as alumina, but may be quartz, a hi~h temperature glass or a metal sleeve coated ~with an insulating material. The cylindrical ,~ : :
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substrate 22 has an in~ernal bore 26 passing therethrough, a base or internal portion 28 dispo~ed in ~hell 12 and a - sma7ler diameter external portion 30 protruding externally from the shell 12 ~hrough the heater aperture 18. The heater aperture 18 has a diameter smaller than the diameter of the internal portion 28 of the substrate 22 and larger than the diameter of the external portion 30.
An axi`al electrode 36 having a radial flange 38 and guide finger 40 formed at one end i~ received in the internal bore 26 of the cylindrical substrate 22 with the radial flange abutting the internal end face of the cylindrical substrate 22. The axial electrode 36 produces a force on the end of the cylindrical substrate 22 sufficient to deform an electrically conductive gasket 32 interposed between shoulder 34 of the cylindrical substrate 22 and the shell contact seat 16. The conductive gasket 32 may be copper, gold or any other malleable metal or alloy.
A cylindrical in~ulator member 44, similar to the insulator commonly used in ~park plug~ in~erted in bore 14 circum-scribing axial electrode 36 and abutting the oppo~ite face of radial flange 38. The end of the shell 12 i9 crimped over to form a peripheral lip 46. The insula~or member 44, axial electrode 36 and hea.ter member 20 are then locked tightly in~ide of shell 12 by a hot pre~s operation which heats and then cool~ the undercut groove 95 while a compressive force i9 applied between peripheral lip 46 and the oppo~ing end 96 of an external hexagonal portion 50. The ~hell 12 further .
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includes an externally threaded portion 48 for mounting the glow plug in the engine. The external hexagonal portion 50 facilitates threading the glow plug 10 into an appropriate threaded aperture of the engine.
One advantage of the glow plug 10 ~hown in Figure 1 is that the electrical connection~ between the ~urface film heater element 24, the ~hell 12 and the axial electrode 36 are made internally of shell 12 where they are pro~ected from the high temperatures and corrosive atmosphere inside the engine. This configuration eliminates the erosion problems of the electrical connections between the metallic ~ilicide film, the shell 12 and the axial electrode 36.
The details of the preferred embodiment of the heater members 20 are illu~trated in Figure 2. Referring to Figure 2, the heater member 20, as previously described, ha3 a generally cylindrical ceramic substrate 22 having an axial bore 26, an internal portion 28, a smaller diameter external portion 30 and a sloped shoulder 34 connecting the external surfaces of the internal portion 28 and external portion 30.
Radii are provided at the edges at the substrate's end face 52 to blend the end face 52 with the contiguous internal sur-face of bore 26 and the external surface 64 of the substrate or a full radius may be proYided a~ shown. In a ~imilar manner, a radius 54 i3 proYided at the ba~e of the ~ubstrate blending the end Pace 42 with the internal surface oP bore 26.
A continuous resistive metallic-~ilicide Pilm 24, such as molybdenum di~ilicide (MoSi2), tung~ten disilicide (WSi2), ~;, .
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- 6a -tantalum di~ilicide (TaSi2), or titanium disilicide ~TiSi2~, is deposited along the sloped shoulder 34, along the length of the external surface 64, around the end 52, then along the internal surface of bore 26 and terminate on end face 42 at a point intermediate the internal and external diameters of the substrate. The metallic-silicide layer 24 may also be extended a short distance along the length of the external surface 60 of substrate 22 as shown.
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The opposite ends of the metallic-silicide layer 24 are electrically isolated by the uncoated region 56 of the external surface 60 and an uncoated peripheral region 58 of the end face 42. The metallic-silicide coating or film 24 may be applied to the desired surfaces of the substrate 22 by chemical vapor deposition techniques or any other method known in the art. Since the deposition techinques for metallic-silicide films have been extensively developed for low-resistance contacts in the solid state industry, it is not necessary to describe in detail how the metallic-silicide films are deposited ror an understanding of the invention.
In practice, the uncoated areas may be protected by mechanical shields during the deposition process.
~Iowever, the entire substrate may be coated and the metallic-silicide layer removed from the insulator regions 56 and 58 by air abrasion. As shown in Figure 6, the interior of the cylindrical substrate after it has been coated with a metallic silicide may be filled with a dielectric material 65, such as alumina, to increase ~the structural strength of the ceramic substrate.
In the embodiment shown on Figure 3, highly conductive metal coating 66 and 68 may be applied over metallic silicide layer 24 disposed on the sloped shoulder 34 and the internal end face 42 respectively to assure good electrical contact hetween the metallic silicide~surface layer 24, the heater seat 16, and the axial electrode 26, respectively~
In the~embodiment ~hown on Figure 4, the length of the axial bore 26 is completely filled with metallic-silicide material or other suitable conductive material ~to form an internal conductor 70 and the ~' :
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re~istive metallic-silicide layer 24 i~ deposited along the length of the substrate~ ex~ernal ~urfaces 34 and 64 and over the end 52 to make electrical contact with the in~ernal con-ductor 70 filling external bore 26. The internal conductor 70 filling the bore 26 may have a recess 72 formed at the end face 42 of the substrate 22 to receive the guide finger 40 of the a~ial electrode 36 and may be sxtended onto the end face 42 to provide a contact region 74 for the axial electrodes radial flange 38. Alternatively, the ceramic substrate may be formed directly around an axial electrode 36A and the resi3tive metallic-silicide ~ilm 24 deposited along the external surfaces 34 and 60 of the substrate 22 and over the end surface 78 of the axial electrode 36A as shown in Figure 5. In this embodiment, the axial electrode 36 has a protrusion 76 adjacent to the interior portion 28 of the cylindrical substrate 22 to longitudinally lock the substrate 22 to the axial electrode 36A prevents any possible longitudinal shifting of the substrate 22 with respect to the axial electrode which would ~racture or cause any electrical discontinuities at the junction between the metallic-silicide film 24 and the end face 78 of the axial electrode 36A.: A highly conductive metal coating such as coating 66, shown in Figure 3, may be deposited over the sloped shoulder 34 to assure good electrical contact between the shell 12 and the resistive metal-silicide layer 24.
.
Preferably the cold resistance of the resistive metallic-silic1de heater element 24 i8 between 0.2 and 0.6 ohms, which permits the heater member 20 to achieve an operating temperature `::
rm/l-`9 of greater than 900C with a current flow of less than 5 amperes when using a 12 volt source of electrical power, such as an automotive battery.
The primary advantage of the cylindrical configuration of the heater member 20 ghown on Figure~ 2 and 3 is that the bore 26 forms a high temperature cul-de-sac adjacent to its external end which i9 isolated from the cooling effects of the swirling air/fuel mixture in the engine's ignition chamber~
Other advantages of the heater member 20 are:
1.) The low mass of the cylindrical substrate 22 and the metallic-silicide surface layer 24 permits the glow plug to reach an operating temperature, greater than 800C, in less than 5 seconds with an applied electrical power of approxi-mately 60 watts.
2.) When compared with a noble metal surface layer, the watt density of the metallic-silicide surface layer on the cylindrical substrate is less than that of a noble metal at any given temperature thereby reducing the current require-ments in the system.
excellent performance characteristics which are superior to glow plugs currently used in automotive vehicles, difficulties have been experienced in the deposition of satisfactory noble metal resistive films due to micro-irregularities on the surfaces of the ceramic substrate and the thinness of the noble metal films required to achieve the desired resistivity. The ob~ect of the invention is the substitution of a metallic-silicide film for the noble metal film which ln because of the higher resistivity of the metallic silicides permits the use of thicker resistive films which are less sensitive to the micro-irregularities of the ceramic structure, have a higher melting temperature which permits the glow plug to be operated at higher temperatures, and have a larger positive coefficient of resistance potentially making the glow plug self-limiting reducing the requirements of the attendant controller.
The use of metallic-silicides for heater elements is well-known in the art. The Kanthal Corporation of Bethel, Connecticut makes a variety of heater elements using metal silicides as the resistive element. These heater elements take the form of a metallic silicide as were disclosed by Giler in U.S. Patent No. 3,912,905 or a layer of metallic-silicide formed over an insulating or ceramic layer disposed over a metal wire for \~J; //5a n structural strength as disclosed by Wilson in U.S.
Patent No. 3,810,734. Suzuki et al in U.S. Patent No.
~,437,440 discloses a glow plug having a tubular 30~ molybdenum disilicide (MoSi2) element in which electrical contact is made between the shell and an axial electrode contacting the closed end of the tubular heatlng element.
\
Summary of the Invention The invention i~ a glow plug for internal combustion engines of the type having a glow plug of the type having a cylindrical metal shell, and an axial electrode dispo~ed ;n the metal shell, in~ulator means supporting the axial electrode concentrically in ~he metal shell and electrically insulating it there~rom, and a heater member electrically connected between the metal shell and the axial electrode, the improvement wherein the heater member comprises: a hollow open-ended cylindrical ceramic substrate having an internal surface, and an external surface, the ~ub~trate having an internal portion ~ecured in the shell between one end of the ~hell and one end of the axial electrode and an external portion protruding externally from the shell, the ceramic substrate having micro-irregularities on the internal and external surfaces; and a continuous metallic-silicide resistive layer disposed along the internal and external surfaces of the cylindrical substrate and around the end of the external portion to form a hollow cylindrical heater element open at the end of the external portion, the portion of the resistive layer disposed along the external surface of the ~ub~trate being electrically connected to the metal shell and the portion of the resistive layer disposed along the internal surface of the substrate being electrically connected to the axial electrode, the metallic-silicide resistlve layer being substantially uneffected by the micro-irregularities on the internal and external surfaces to provide a cold resistance rm/
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of from 0.2 to 0.6 ohmg to the flow of electrical current, the resi3tive layer responding to five amperes of electrical current to develop a temperature of at least 800C within five seconds, the metallic silicide resistive layer having a positive coefficient of resistance to provide for ~elf limiting which reduces the operating requirements of a controller.
The advantages of the glow plug is that the interior of the cylindrically shaped heater member ~orms an extremely hot cul-de-sac which is not cooled by the impinging air/fuel mixture. Another advantage is that the metallic-silicide resistive layer iq relatively in~en~itive to oxidation and the corrosive atmosphere inside the engine. Another advantage i8 that the low mass of the heater member permits the glow plug to reach an operating temperature in less than 5 seconds with an applied power of less than 60 watts. These and other advantages of the glow plug will become more apparent from a reading of the specification in conjunction with the figures.
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~' 21JRI02~5/0216m 600-8~-0040 8rief Description of the Drawings FIGURE 1 is a cross-sectional view of the glow plug embodying the cylindrical ceramic heater member.
5FIGURE 2 is a cross-sectional view of a first embodiment of the cylindrical heater member.
FIGURE 3 is a cross-sectional view of a second embodiment of the cylindrical heater member.
FIGURE 4 is a cross-sectional view of an embodiment of the heater member having the interior of the ceramic filled with a metallic silicide.
FIGURE 5 is a cross-sectional view of an embodiment of the heater member having the cylindrical substrate formed around the axial electrode.
15FIGUR~ 6 is a cross-sectional view of an embodiment of the heater member having the interior of the cyllndrical substrate filled with alumina.
~etailed Description of the Invent on A cross-sectional view of the glow plug is shown in Figure 1. The glow plug comprises a cylindrical metal shell 12 having an internal bore 14. Formed at one end of the shell 12 is a contact seat 16 defining a heater aperture 18 . Located in the internal bore 14 is a heater member 20 having a resistive metallic-silicide surface~film heater element 24 coated or disposed on at least~ one surface of a non-conductive cylindrical substraté 22 as shall be described hereinafter. ~he 30 ;non-~conductive substrate 22 is preferably a high ~temperature ceramic, such as alumina, but may be quartz, a hi~h temperature glass or a metal sleeve coated ~with an insulating material. The cylindrical ,~ : :
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substrate 22 has an in~ernal bore 26 passing therethrough, a base or internal portion 28 dispo~ed in ~hell 12 and a - sma7ler diameter external portion 30 protruding externally from the shell 12 ~hrough the heater aperture 18. The heater aperture 18 has a diameter smaller than the diameter of the internal portion 28 of the substrate 22 and larger than the diameter of the external portion 30.
An axi`al electrode 36 having a radial flange 38 and guide finger 40 formed at one end i~ received in the internal bore 26 of the cylindrical substrate 22 with the radial flange abutting the internal end face of the cylindrical substrate 22. The axial electrode 36 produces a force on the end of the cylindrical substrate 22 sufficient to deform an electrically conductive gasket 32 interposed between shoulder 34 of the cylindrical substrate 22 and the shell contact seat 16. The conductive gasket 32 may be copper, gold or any other malleable metal or alloy.
A cylindrical in~ulator member 44, similar to the insulator commonly used in ~park plug~ in~erted in bore 14 circum-scribing axial electrode 36 and abutting the oppo~ite face of radial flange 38. The end of the shell 12 i9 crimped over to form a peripheral lip 46. The insula~or member 44, axial electrode 36 and hea.ter member 20 are then locked tightly in~ide of shell 12 by a hot pre~s operation which heats and then cool~ the undercut groove 95 while a compressive force i9 applied between peripheral lip 46 and the oppo~ing end 96 of an external hexagonal portion 50. The ~hell 12 further .
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includes an externally threaded portion 48 for mounting the glow plug in the engine. The external hexagonal portion 50 facilitates threading the glow plug 10 into an appropriate threaded aperture of the engine.
One advantage of the glow plug 10 ~hown in Figure 1 is that the electrical connection~ between the ~urface film heater element 24, the ~hell 12 and the axial electrode 36 are made internally of shell 12 where they are pro~ected from the high temperatures and corrosive atmosphere inside the engine. This configuration eliminates the erosion problems of the electrical connections between the metallic ~ilicide film, the shell 12 and the axial electrode 36.
The details of the preferred embodiment of the heater members 20 are illu~trated in Figure 2. Referring to Figure 2, the heater member 20, as previously described, ha3 a generally cylindrical ceramic substrate 22 having an axial bore 26, an internal portion 28, a smaller diameter external portion 30 and a sloped shoulder 34 connecting the external surfaces of the internal portion 28 and external portion 30.
Radii are provided at the edges at the substrate's end face 52 to blend the end face 52 with the contiguous internal sur-face of bore 26 and the external surface 64 of the substrate or a full radius may be proYided a~ shown. In a ~imilar manner, a radius 54 i3 proYided at the ba~e of the ~ubstrate blending the end Pace 42 with the internal surface oP bore 26.
A continuous resistive metallic-~ilicide Pilm 24, such as molybdenum di~ilicide (MoSi2), tung~ten disilicide (WSi2), ~;, .
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- 6a -tantalum di~ilicide (TaSi2), or titanium disilicide ~TiSi2~, is deposited along the sloped shoulder 34, along the length of the external surface 64, around the end 52, then along the internal surface of bore 26 and terminate on end face 42 at a point intermediate the internal and external diameters of the substrate. The metallic-silicide layer 24 may also be extended a short distance along the length of the external surface 60 of substrate 22 as shown.
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The opposite ends of the metallic-silicide layer 24 are electrically isolated by the uncoated region 56 of the external surface 60 and an uncoated peripheral region 58 of the end face 42. The metallic-silicide coating or film 24 may be applied to the desired surfaces of the substrate 22 by chemical vapor deposition techniques or any other method known in the art. Since the deposition techinques for metallic-silicide films have been extensively developed for low-resistance contacts in the solid state industry, it is not necessary to describe in detail how the metallic-silicide films are deposited ror an understanding of the invention.
In practice, the uncoated areas may be protected by mechanical shields during the deposition process.
~Iowever, the entire substrate may be coated and the metallic-silicide layer removed from the insulator regions 56 and 58 by air abrasion. As shown in Figure 6, the interior of the cylindrical substrate after it has been coated with a metallic silicide may be filled with a dielectric material 65, such as alumina, to increase ~the structural strength of the ceramic substrate.
In the embodiment shown on Figure 3, highly conductive metal coating 66 and 68 may be applied over metallic silicide layer 24 disposed on the sloped shoulder 34 and the internal end face 42 respectively to assure good electrical contact hetween the metallic silicide~surface layer 24, the heater seat 16, and the axial electrode 26, respectively~
In the~embodiment ~hown on Figure 4, the length of the axial bore 26 is completely filled with metallic-silicide material or other suitable conductive material ~to form an internal conductor 70 and the ~' :
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re~istive metallic-silicide layer 24 i~ deposited along the length of the substrate~ ex~ernal ~urfaces 34 and 64 and over the end 52 to make electrical contact with the in~ernal con-ductor 70 filling external bore 26. The internal conductor 70 filling the bore 26 may have a recess 72 formed at the end face 42 of the substrate 22 to receive the guide finger 40 of the a~ial electrode 36 and may be sxtended onto the end face 42 to provide a contact region 74 for the axial electrodes radial flange 38. Alternatively, the ceramic substrate may be formed directly around an axial electrode 36A and the resi3tive metallic-silicide ~ilm 24 deposited along the external surfaces 34 and 60 of the substrate 22 and over the end surface 78 of the axial electrode 36A as shown in Figure 5. In this embodiment, the axial electrode 36 has a protrusion 76 adjacent to the interior portion 28 of the cylindrical substrate 22 to longitudinally lock the substrate 22 to the axial electrode 36A prevents any possible longitudinal shifting of the substrate 22 with respect to the axial electrode which would ~racture or cause any electrical discontinuities at the junction between the metallic-silicide film 24 and the end face 78 of the axial electrode 36A.: A highly conductive metal coating such as coating 66, shown in Figure 3, may be deposited over the sloped shoulder 34 to assure good electrical contact between the shell 12 and the resistive metal-silicide layer 24.
.
Preferably the cold resistance of the resistive metallic-silic1de heater element 24 i8 between 0.2 and 0.6 ohms, which permits the heater member 20 to achieve an operating temperature `::
rm/l-`9 of greater than 900C with a current flow of less than 5 amperes when using a 12 volt source of electrical power, such as an automotive battery.
The primary advantage of the cylindrical configuration of the heater member 20 ghown on Figure~ 2 and 3 is that the bore 26 forms a high temperature cul-de-sac adjacent to its external end which i9 isolated from the cooling effects of the swirling air/fuel mixture in the engine's ignition chamber~
Other advantages of the heater member 20 are:
1.) The low mass of the cylindrical substrate 22 and the metallic-silicide surface layer 24 permits the glow plug to reach an operating temperature, greater than 800C, in less than 5 seconds with an applied electrical power of approxi-mately 60 watts.
2.) When compared with a noble metal surface layer, the watt density of the metallic-silicide surface layer on the cylindrical substrate is less than that of a noble metal at any given temperature thereby reducing the current require-ments in the system.
3.) The electrlcal connections to the metallic-silicide surface layer are made internally of the shell 12, reducing their exposure to the higher engine temperatures and thereby reducing their oxidation and/or corrosion.
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4.) The positive temperature coefficient of the metallic-silicide surface layer heater elemenk tends to make the glow plug less suscepti~le to variation3 in the applied voltage and easier to control.
S.) The metallic-silicide heater element is highly resistive to the corrosive atmosphere inside the engineO
6.) The components of the glow plug are applicable to standard spark plug manufacturing processe~ and therefore are potentially less costly than other type~ of glow plugs.
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, 21JRI0285/0216m 600-~4-0040 It is recognized that the configuration of the various elements of the glow plug ~a~ be changed from those shown in the drawings or discussed in the specification without departing from the spirit of the invention as described herein and set forth in the appended claims.
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S.) The metallic-silicide heater element is highly resistive to the corrosive atmosphere inside the engineO
6.) The components of the glow plug are applicable to standard spark plug manufacturing processe~ and therefore are potentially less costly than other type~ of glow plugs.
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, 21JRI0285/0216m 600-~4-0040 It is recognized that the configuration of the various elements of the glow plug ~a~ be changed from those shown in the drawings or discussed in the specification without departing from the spirit of the invention as described herein and set forth in the appended claims.
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Claims (16)
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. In a glow plug of the type having a cylindrical metal shell, and an axial electrode disposed in said metal shell, insulator means supporting said axial electrode concentrically in said metal shell and electrically insulating it therefrom, and a heater member electrically connected between the metal shell and the axial electrode, the improvement wherein said heater member comprises:
a hollow open-ended cylindrical ceramic substrate having an internal surface, and an external surface, said substrate having an internal portion secured in the shell between one end of the shell and one end of said axial electrode and an external portion protruding externally from the shell, said ceramic substrate having micro irregularities on said internal and external surfaces; and a continuous metallic-silicide resistive layer disposed along the internal and external surfaces of said cylindrical substrate and around the end of said external portion to form a hollow cylindrical heater element open at the end of said external portion, the portion of said resistive layer disposed along the external surface of said substrate being electrically connected to the metal shell and the portion of said resistive layer disposed along the internal surface of said substrate being electrically connected to the axial electrode, said metallic-silicide resistive layer being substantially uneffected by said micro-irregularities on said internal and external surfaces to provide a cold resistance of from 0.2 to 0.6 ohms to the flow of electrical current, said resistive layer res-ponding to five amperes of electrical current to develop a temperature of at least 800°C within five seconds, said metallic-silicide resistive layer having a positive coefficient of resistance to provide for self limiting which reduces the operating requirements of a controller.
a hollow open-ended cylindrical ceramic substrate having an internal surface, and an external surface, said substrate having an internal portion secured in the shell between one end of the shell and one end of said axial electrode and an external portion protruding externally from the shell, said ceramic substrate having micro irregularities on said internal and external surfaces; and a continuous metallic-silicide resistive layer disposed along the internal and external surfaces of said cylindrical substrate and around the end of said external portion to form a hollow cylindrical heater element open at the end of said external portion, the portion of said resistive layer disposed along the external surface of said substrate being electrically connected to the metal shell and the portion of said resistive layer disposed along the internal surface of said substrate being electrically connected to the axial electrode, said metallic-silicide resistive layer being substantially uneffected by said micro-irregularities on said internal and external surfaces to provide a cold resistance of from 0.2 to 0.6 ohms to the flow of electrical current, said resistive layer res-ponding to five amperes of electrical current to develop a temperature of at least 800°C within five seconds, said metallic-silicide resistive layer having a positive coefficient of resistance to provide for self limiting which reduces the operating requirements of a controller.
2. The heater member of Claim 1 wherein the metal shell has a peripheral seat defining a heater aperture at said one end thereof, said internal portion of said cylindrical substrate has a shoulder portion engaging said peripheral seat and said external portion passes through said heater aperture and wherein said resistive layer disposed along said external surface extends along the surface of said shoulder portion.
3. The heater member of Claim 2 wherein the axial electrode has a radial flange engaging the end of said internal portion of said cylindrical substrate, said resistive layer disposed along the internal surface of said substrate is extended along the surface of the end of said internal portion to form an electrical contact area having a diameter intermediate the internal and external diameters of said internal end portion, and wherein the radial flange of the axial electrode makes electrical contact with said contact area.
4. The heater member of Claim 3 having a metal film disposed on the surface of said resistive layer on said shoulder portion and on said contact area to lower the electrical contact resistance between the metal shell and the axial electrode and the resistive layer disposed along the external and internal surfaces of said cylindrical substrate.
5. The heater of Claim 4 having an electrically conductive gasket disposed between said should portion of the cylindrical substrate and said peripheral seat.
6. The heater member of Claim 1 wherein said metallic-silicide resistive layer is a molybdenum disilicide resistive layer.
7. The heater member of Claim 1 wherein said metallic-silicide resistive layer is a tungsten disilicide resistive layer.
8. The heater member of Claim 1 wherein said metallic-silicide resistive layer is a tantalum disilicide resistive layer.
9. The heater member of Claim 1 wherein said metallic-silicide resistive layer is a titanium disilicide resistive layer.
10. A glow plug comprising:
a metal shell defining a cylindrical internal chamber having a heater aperture at one end thereof;
a hollow open-ended cylindrical ceramic substrate having an external surface and an internal surface, said ceramic substrate having a first portion disposed in said internal chamber adjacent to said heater aperture and a second portion extending longitudinal through said heater aperture externally from said shell; said internal and external surfaces having micro-irregularities thereon;
a continuous metallic-silicide resistive layer deposited on said internal and external surfaces and around the end of said second portion to form a hollow cylindrical heater element open at both ends, said resistive layer having a cold resistance of from 0.2 to 0.6 ohms to the flow of electrical current, the portion of said resistive layer disposed along said external surface being in electrical contact with said shell;
an axial electrode disposed in said shell and having a radial flange and guide any of which engage the end of said first portion to secure said cylindrical substrate in said shell and electrically contacting said resistive layer disposed along said internal surface; and an insulator disposed in said shell for supporting said axial electrode in engagement with said cylindrical substrate and electrically insulating said axial electrode from said shell, said metallic silicide resistive layer being substantially uneffected by said micro-irregularities on said internal and external surfaces by responding to five amperes of electrical current to permit said glow plug to operate at temperatures above 800°C within five seconds, said metallic-silicide resistive layer having a positive coefficient of resistance to provide for self limiting which reduces the operating requirements of a controller.
a metal shell defining a cylindrical internal chamber having a heater aperture at one end thereof;
a hollow open-ended cylindrical ceramic substrate having an external surface and an internal surface, said ceramic substrate having a first portion disposed in said internal chamber adjacent to said heater aperture and a second portion extending longitudinal through said heater aperture externally from said shell; said internal and external surfaces having micro-irregularities thereon;
a continuous metallic-silicide resistive layer deposited on said internal and external surfaces and around the end of said second portion to form a hollow cylindrical heater element open at both ends, said resistive layer having a cold resistance of from 0.2 to 0.6 ohms to the flow of electrical current, the portion of said resistive layer disposed along said external surface being in electrical contact with said shell;
an axial electrode disposed in said shell and having a radial flange and guide any of which engage the end of said first portion to secure said cylindrical substrate in said shell and electrically contacting said resistive layer disposed along said internal surface; and an insulator disposed in said shell for supporting said axial electrode in engagement with said cylindrical substrate and electrically insulating said axial electrode from said shell, said metallic silicide resistive layer being substantially uneffected by said micro-irregularities on said internal and external surfaces by responding to five amperes of electrical current to permit said glow plug to operate at temperatures above 800°C within five seconds, said metallic-silicide resistive layer having a positive coefficient of resistance to provide for self limiting which reduces the operating requirements of a controller.
11. The glow plug of Claim 10 wherein said metallic-silicide resistive layer is a molybdenum disilicide resistive layer.
12. The glow plug of Claim 10 wherein said metallic-silicide resistive layer is a tungsten disilicide resistive layer.
13. The glow plug of Claim 10 wherein said shell has a peripheral seat defining said heater aperture and wherein said external surface of said first portion has a sloped shoulder engaging said peripheral seat, said resistive layer disposed along said external surface being also disposed along the surface of said sloped shoulder.
14. The glow plug of Claim 13 wherein said axial electrode has a radial flange engaging the end of said first portion, said resistive layers disposed along the internal surface of said substrate extending along the surface of the end of said first portion to form an electrical contact area having a diameter intermediate the internal and external diameters of said cylindrical substrate.
15. The glow plug of Claim 14 having a metal layer disposed along the surfaces of the resistive layer disposed on said sloped shoulder and said contact area.
16. A hollow cylindrical heater member comprising:
a hollow open-ended cylindrical ceramic substrate having an external surface, an internal surface and two end surfaces, one at each end of said cylindrical ceramic substrate, said ceramic substrate having micro-irregularities thereon;
and a metallic-silicide resistive surface layer disposed along said external and internal surfaces and around one of said end surface to form a continuous resistive layer extending from said external surface to said internal surface to provide a cold resistance of from 0.2 to 0.6 ohms to the flow of electrical current, said metallic-silicide resistive layer surface layer being substantially uneffected by said micro-irregularities in said ceramic substrate and responding to five amperes of electrical current to permit said glow plug to operate at temperatures above 800°C within five seconds, said metallic-silicide resistive surface layer having a positive coefficient of resistance to provide for self limiting which reduces the operating requirements of a controller.
a hollow open-ended cylindrical ceramic substrate having an external surface, an internal surface and two end surfaces, one at each end of said cylindrical ceramic substrate, said ceramic substrate having micro-irregularities thereon;
and a metallic-silicide resistive surface layer disposed along said external and internal surfaces and around one of said end surface to form a continuous resistive layer extending from said external surface to said internal surface to provide a cold resistance of from 0.2 to 0.6 ohms to the flow of electrical current, said metallic-silicide resistive layer surface layer being substantially uneffected by said micro-irregularities in said ceramic substrate and responding to five amperes of electrical current to permit said glow plug to operate at temperatures above 800°C within five seconds, said metallic-silicide resistive surface layer having a positive coefficient of resistance to provide for self limiting which reduces the operating requirements of a controller.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US71322485A | 1985-03-15 | 1985-03-15 | |
| US713,224 | 1985-03-15 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1252830A true CA1252830A (en) | 1989-04-18 |
Family
ID=24865294
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000503183A Expired CA1252830A (en) | 1985-03-15 | 1986-03-04 | Glow plug having a metallic silicide resistive film heater |
Country Status (6)
| Country | Link |
|---|---|
| EP (1) | EP0194535A3 (en) |
| JP (1) | JPS61213512A (en) |
| AU (1) | AU5436686A (en) |
| BR (1) | BR8601457A (en) |
| CA (1) | CA1252830A (en) |
| ES (1) | ES8701952A1 (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3843863A1 (en) * | 1988-12-24 | 1990-06-28 | Bosch Gmbh Robert | High-temperature heating element, method of producing it and use thereof |
| DE4335292A1 (en) * | 1993-10-15 | 1995-04-20 | Beru Werk Ruprecht Gmbh Co A | Glow plug |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3912905A (en) * | 1974-02-25 | 1975-10-14 | Kanthal Corp | Electric resistance heating device |
| US4418661A (en) * | 1981-02-07 | 1983-12-06 | Robert Bosch Gmbh | Glow plug, particularly for diesel engine |
| DE3237922A1 (en) * | 1982-10-13 | 1984-04-19 | Robert Bosch Gmbh, 7000 Stuttgart | GLOW PLUG FOR INTERNAL COMBUSTION ENGINES |
| DE3464660D1 (en) * | 1983-06-23 | 1987-08-13 | Allied Corp | An improved glow plug having a resistive surface film heater |
| JPS613922A (en) * | 1984-06-18 | 1986-01-09 | Jidosha Kiki Co Ltd | Glow plug for diesel engine |
-
1986
- 1986-03-01 EP EP86102681A patent/EP0194535A3/en not_active Withdrawn
- 1986-03-04 CA CA000503183A patent/CA1252830A/en not_active Expired
- 1986-03-06 AU AU54366/86A patent/AU5436686A/en not_active Abandoned
- 1986-03-14 BR BR8601457A patent/BR8601457A/en unknown
- 1986-03-14 ES ES553026A patent/ES8701952A1/en not_active Expired
- 1986-03-14 JP JP5514086A patent/JPS61213512A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| ES8701952A1 (en) | 1986-12-01 |
| EP0194535A3 (en) | 1988-01-07 |
| ES553026A0 (en) | 1986-12-01 |
| BR8601457A (en) | 1986-12-09 |
| EP0194535A2 (en) | 1986-09-17 |
| AU5436686A (en) | 1986-09-18 |
| JPS61213512A (en) | 1986-09-22 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |