CA1230937A - Glow plug having a resistive surface film heater - Google Patents
Glow plug having a resistive surface film heaterInfo
- Publication number
- CA1230937A CA1230937A CA000456162A CA456162A CA1230937A CA 1230937 A CA1230937 A CA 1230937A CA 000456162 A CA000456162 A CA 000456162A CA 456162 A CA456162 A CA 456162A CA 1230937 A CA1230937 A CA 1230937A
- Authority
- CA
- Canada
- Prior art keywords
- glow plug
- shell
- heater element
- external
- surface film
- 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
-
- 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
Landscapes
- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Resistance Heating (AREA)
- Ignition Installations For Internal Combustion Engines (AREA)
- Combustion Methods Of Internal-Combustion Engines (AREA)
Abstract
Abstract:
AN IMPROVED GLOW PLUG HAVING
A RESISTIVE SURFACE FILM HEATER
A glow plug (10) having a hollow cylindrical metal shell (12), an axial electrical terminal (36), and a heater member (20) protruding externally from the shell. The heater member (20) has a surface film heater element (24) disposed on at least one surface of an electrically nonconductive cylindrical substrate (22).
Electrical connections between the heater element (24), the shell and the axial electrode are made by conductive surface films (56, 58). A first conductive surface film (56) disposed on the external surface of the cylindrical substrate (22) makes electrical contact with the shell (12). A second conductive surface film (58) disposed on the internal surface of the cylindrical substrate (22) makes electrical contact with the axial electrical terminal (36). The heating element (24) is preferably a transition metal surface film which catalytically reacts with the air/fuel mixture to enhance combustion at lower temperatures. The thermal response time of the surface film heater element (24) from ambient to an operating temperature exceeding 800 is less than 5 seconds.
(FIGURES 1 & 2)
AN IMPROVED GLOW PLUG HAVING
A RESISTIVE SURFACE FILM HEATER
A glow plug (10) having a hollow cylindrical metal shell (12), an axial electrical terminal (36), and a heater member (20) protruding externally from the shell. The heater member (20) has a surface film heater element (24) disposed on at least one surface of an electrically nonconductive cylindrical substrate (22).
Electrical connections between the heater element (24), the shell and the axial electrode are made by conductive surface films (56, 58). A first conductive surface film (56) disposed on the external surface of the cylindrical substrate (22) makes electrical contact with the shell (12). A second conductive surface film (58) disposed on the internal surface of the cylindrical substrate (22) makes electrical contact with the axial electrical terminal (36). The heating element (24) is preferably a transition metal surface film which catalytically reacts with the air/fuel mixture to enhance combustion at lower temperatures. The thermal response time of the surface film heater element (24) from ambient to an operating temperature exceeding 800 is less than 5 seconds.
(FIGURES 1 & 2)
Description
~.~3~
The invention is related to the field of electric heaters for the ignition of hydrocarbon fuels and in particular to glow plugs for assisting the start of Diesel type internal combustion engines.
The invention is an improved embodiment of the glow plug described in co-pending commonly-assigned patent application, Serlal Number 434,875 entitled "A Glow ~lug Having A Conductive Film Heater" filed August 18, 1983.
Electrically energized glow plugs are currently used in compression ignited or Diesel type internal combustion engines to assist in the ignition of the airJfuel mixture during cold starts. In particular glow plugs are essential in the northern states during the winter months when ambient temperatures fall below 10C.
Currently the glow plugs, such as disclosed by Mann in U.S. Patent 4,281,451, have a coil wire heater enclosed in a protective metal shield. The problem with these glow plugs is that they have a relatively low thermal ; response time, 15 to 30 seconds, and require relatively large currents, 15 to 25 amps, to bring them up to ,' ~ ~
mab/ f~) - 22~-83-0070 J ~3~3~33~
the required operating temperature. The prior art also teaches replacing the coiled wire heating element with a spiral wound flat tape type heating element as disclosed by Knowles in V.S. Pa~ent 41297,785. Alternatively 5 Yamamoto et al in U . S . Patent 4 ~ 357,526 and Sagawa et al in U.S. Patent 4,035,613 teach a discrete printed circuit heating element imbedded in a ceramic body. ~owever, all of these glow plugs still exhibit the same slow thermal response and relatively high electrical power requirement 5 .
In contrast to the glow plugs described above, Knoll et al in British Patent ~pplication 2,092,670-A published August 18, 1982, disclose a glow plug having a layered platinum-rhodium alloy surface film heater element applied to the base of a closed end ceramic tube.
~ he Applicant in co-pending commonly assigned Patent Application Serial No. 430,909, filed September 30, 19~2 disclosed a similar glow plug having a transition metal surface film heater element circumfrentially coated on a surface of a cylindrical ceramic substrate adjacent to it's end. Tests of the glow plug disclosed in Patent Applica~ion 430,909 exhibited improved performance, however, contact oorrosion at the opposite ends of ~he surface film heater element where electrical contac~ was 25 made to the outer shell and axial electrical terminal were encountered during life tests. The invention is an improved embodiment of the surface film heater type glow plug which is more efficient than the glow plug disclosed by Rnoll et al, is easier to make, and solves the contact 30 problems encountered in the former design.
Summary of_the Invention The invention is a glow plu~ for an internal combustion 35 engine having a cylindrical metal shell, an axial 223-~3-0070 ~.~3~37' electrical terminal located concentrically in said shell and electrically insul ted therefrom and a surface film heater member electrically connected between the metal shell and the axial electrode. The hea er member comprises a cylindrical nonconductive substrate having one end internally captivated between one end of the shell and the axial electrical terminal, and the other end of the heater member protruding externally from the shell. A concen~ric bore passes through said subs~rate.
A resistive surface film heater element is coated on at least one surface of the substrate adjacent to ~he external end. A first conductive surface film coated on the external surface of the substrate connects one end of the heater element to the shell. A second conductive surface film coated on at least the internal surface of the substrate connects the other end of the heater element with the axial electricaI terminal. Preferably the heater element is a ransition metal of the platinum family.
One advantage of the glow plug is that the cylin-drical heating element forms a hot cul-de-sac region isolated from the cooling effects of impringing air/fuel mixture and enhances ignition.
Another advantage of the glow plug is that both 25 connections between the heater element, the shell and the axial electrical terminal are made internal to the shell and not exposed to the high temperature and corrosive atmosphere of the engine. Still another advantage of the glow plug is that the heater element is located at the tip of the ceramic substrate minimizing the protrusion needed into the engine ~ s ignition chamber reducing interference of the glow plug with the ignition chamber's air flow pattern. These and other advantages of the improved glow plug will become more apparent from a 223~~3-007 0 ~.~3~3~
reading of the specification in conjunction with the drawingsv Brief DescriPtion of the Fiqures FIGURÆ 1 is a cross section of the improved embodiment of the glow plug.
FIGUR~ 2 is an enlarged cross-section showing the de~ails of ~he heater member.
10FIGURE 3 is an enlarged cross-section of a second embodiment of the heater member.
FIGURE 4 is an enlarged cross-section of a third embodiment of the heater member.
FIGURE 5 is a cross-section showing the glow plug mounted in the swirl chamber of a diesel type internal combustion engine.
Detailed Description of the Invention 20A cross-sectional view of the glow plug is shown in FIGURE 1. The glow plug 10 comp~ises a cylindrîcal metal shell 12 having an internal bore 14. Formed at one end of the shell 12 is a contact seat 16 ~efining a heater aperture 18. Located in the internal bore 14 is a heater 25 member 20 having a resistive surface film heater element 24 coated or disposed on at least one surface of a non-conductive substrate 22 adjacent to one end thereof ~sshall be described hereinafter. The nonconductive substrate ~2 is preferably a high temperature ceramic, but may be quartz, a high temperature glass, or metal sleeve coated with an insulating material. The substrate has an internal bore 2Ç, a base or internal portion 28 disposed in shell 12 and a smaller dlameter external portion 30 protruding external to the shell 12 through the heater aperture 18. Heater aperture 18 has a ~36~
diameter smaller than the diameter of internal portion 28 of the æubstrate 22 and larger than the diameter of external portion 30.
An axial electrical terminal 36 has a radial flange 38 and guide 40 formed at one end. The guide 40 is received into the internal bore 26 of substrate 22 wi~h one face of the radial flange 38 abutting the internal end face 42 of the substrate 22 with a orce sufficient to deform an electrically conductive gasket 32 interposed between a shoulder 34 of the substrate 22 and the shell contact seat 16. The conduc~ive gasket 32 may be copper, gold or any other maleable metal or alloy.
A cylindrical insulator member 44, similar to the insulator commonly used in spark plugs, is inserted in bore 14 circumscribing axial electrical terminal 36 and abutting the opposite face of radial flange 38. The end of the shell 12 is crimped over to form a peripheral lip 46. The insulator member 44, axial electrical terminal 36 and heater member 20 are then locked tightly inside of shell 12 by a hot press operation which heats, then cools and undercut groove 9S while a compressive force is applied between peripheral lip 46 and the opposing end 96 of an external hexagonal portion 50. The shell 12 further includes an externally threaded portion 48 for 25 mounting the glow plug 10 in the engine. The external hexagonal portion 50 facilitates threading the glow plug into an appropriate threaded aperture of the engine.
One advantage of the glow plug shown in FIGURE 1 is that the electrical connections between the surface film 30 heater element 24, ~he shell 12, and the axial electrical terminal 36 are made internal to the shell 12 where they are protected from ~he high temperatures and corrosive atmosphere inside of the engine. This configuration eliminates the electrical terminal corrosion problems 35 encountered with the prior designs.
3~37 The details of the heater member 20 are illustrated in FIGURE 2. Referring to FIGURE 2, the heater member 20, as previously described, has a generally cylindrical substrate 22 having an internal bore ~6, an internal portion 28; a smaller diameter external portion 3~0 and a sloped shoulder 34 connecting the external surfaces of the internal portion 2~ and external portion 30. The edges a~ end face 52 of the substrate 22 are ground to form radii blending the end face 52 with the contiguous internal surface of bore 26 with the external surface of the substrate or may be ground to form a full radius as shown. In a similar manner a ground radius 54 is formed at the base of the substrate blending the end face 42 with the internal surface of bore 26.
A higbly conductive metal film 56 is circumferen-tially coated on the surface of shoulder 34 and a predetermined distance along the external surface of the ex~ernal portion 30 of the substrate .leaving a first uncoated portion 60 adjacent to end fice 42 and a second 20 uncoated portion 64 adjacent to end face 52. A similar highly conductive metal film 58, is coated on the internal surface of cylindrical substrate 22 and ex~ends around radius 54 onto end face 42 as shown. The metal film on the end face 42 has a diame~er smaller than the 25 diameter of the internal portion 28 leaving an uncoated peripheral portion 62. The highly conductive metal films 56 and 5B ~ay be transition metal films, gold films, alloys thereof or any other metal or metal alloy films.
A resistive metal surface film heater element 24, 30 having a resistance greater ~han 0.2 ohms is deposited on the uncoated portion 64 of the substrate and on end face 52. Preferably the resistance of heater element 24 is between 0~4 and 0.6 ohms. ~eater element 24 and the conductive metal films 56 and 58 overlap providing for electrical contact therebetween. Preferably the resis-223-~3-0070 ~ ~3C~3~7 tive metal of heater element 24 is of the platinum family consisting of pla~inum, rhodium, palladium, iridium and alloys thereof. Alloys having higher melting tempera-tures, such as alloys containing tungsten and at least one transition metal may be used ~o increase the operating temperature of ~he glow plu90 The primary advantage of the cylindrical configura-tion of the hea~er member is tha~ the bore 26 form a high temperature cul-de-sac adjacent to its open end which i5 isolated from the cooling effects of the swirling air/
fuel mixture in the en~ine's ignition chamber. The air/fuel misture ent~ring the high temperature cul-de-sac formed by bore 26 is more readily ignited than the air/fuel mixture impringing on the external surfaces of the heater member enhancing the ignition efficiency of the glow plug.
In the assembly of the glow plug one end of the heater element 24 is in electrical contact with the shell 12 through surface film 56 on shoulder 34 and 20 electrically conductive gasket 32 while other end of heater element is in electrical con~act with axial electrical ~erminal 36 through surface film 58 on the internal surface of bore 26 and radial flange 38 abutting the extention of surface film 58 onto the end face 42.
In an alternate embodiment of the heater member 20 shown in FIGURE 3, the bore 26 of the substrate 22 is tapered outwardly at end 52 to enhance the depth at which the heater element 24 may be coated into bore 26. This : . permi~s the heater element 24 to wrap around end face 52 and extend a short distance into bore 26 as shown. This further enhances the formation of the high temperature cul-de-sac as previously described.
In contrast to the arrangement shvwn on Figures and 3 the heater element 24 may be coated on the internal 35 surface of the ceramic substrate defined by bore 26 as 223-83~0070 .
~ Z3C~3~
shown on Figure 4. In this confiyuration the ~onductive metal film 56 extends along the external surface of the substrate adjacent ~o end face 52. ~he conductive metal film 58 extends along the internal surface of the sub-strate and onto end face 42 as in the prior embodiments.
This configuration further enhances the high temperature cul-de-sac formed in the bore 26 of ceramic subs~ra~e adjacen~ to the external end face 52.
Because the heater element 24 is located adjacent to the tip of the glow plug, it is no longer required for the glow plug to pro~rude fully into the ignition chamber of the engine. Referring to FIGURE 5 there is illustrated a typical swirl chamber 68 of a diesel type engine having an aperture 70 communicating with the corresponding engine cylinder. As is known in the art, air is pumped in and out of the swirl chamber 68 with the reciprocation of the cylinder's piston as indicated by dashed double headed arrrow 72. Fuel ~rom a Fuel Injector 74 is injected into the swirl chamber where it is mixed with the swirling air to form a combustible air/fuel mix~ure. Because the heater element 24 of the improved glow plug 10 is formed at the tip of the substrate 22, only the ~ip of the glow plug need to pro-trude into the swirl chamber 68 as shown. In this way 25 the glow plug 10 produces minimal in~erference with the swirling air pattern inside of chamber 68. In fact, tests conducted to date indicate efficient ignition of the air fuel mixture can be obtained with the glow plug mounted in the glow plug well 76 with the tip disposed 30 flush with the internal walls of the swirl chamber 68.
The advantages of the improved glow plug are ~s follows:
1. The low mass of the surface film heater element 24 permits the glow plug to reach an vperational 35 temperature above 800C in less than 5 seconds, ~3C~3~
20 The ~att density of the surface film heater element 24 exceeds ~hat of bulk material giving rise to current requirements averaging in the range from 3 to 7 amps at operating temperatures.
53. The transition me~al heater ~element 24 exhibits catalytic action enhancing the ignition of the air/fuel - mixture at lower temperatures.
4. The internal surface of the heater member 20 adjacent to external end face 52 remains at the ignition temperature of the air/fuel mixture regardless of the cooling from fuel or air in the ignition chamber.
5. Because the heater element 24 is located at the tip of the glow plug~ only the tip of the glow plug needs to protrude into the ignition chamber producing only minimum interference with the ignition chamber's fluid flow pattern.
6. The electrical ~ontacts ~o the conductive sur-face films 56 and 58 are made within the shell 12 reducin~ their exposure to the higher engine temperatures reducing their oxidation and corrosion.
7. The components of the glow plug are applicable to standard spark plug manufacturing techniques and therefore are potentially less costly than glow plugs using spiral wound wire heaters.
25It is recognized that the conf iyuration of the various elements of the glow plug may be changed from those shown on the drawings withou~ departing from the spirit o~ the inven~ion as described herein and se~ forth in the appended claims.
The invention is related to the field of electric heaters for the ignition of hydrocarbon fuels and in particular to glow plugs for assisting the start of Diesel type internal combustion engines.
The invention is an improved embodiment of the glow plug described in co-pending commonly-assigned patent application, Serlal Number 434,875 entitled "A Glow ~lug Having A Conductive Film Heater" filed August 18, 1983.
Electrically energized glow plugs are currently used in compression ignited or Diesel type internal combustion engines to assist in the ignition of the airJfuel mixture during cold starts. In particular glow plugs are essential in the northern states during the winter months when ambient temperatures fall below 10C.
Currently the glow plugs, such as disclosed by Mann in U.S. Patent 4,281,451, have a coil wire heater enclosed in a protective metal shield. The problem with these glow plugs is that they have a relatively low thermal ; response time, 15 to 30 seconds, and require relatively large currents, 15 to 25 amps, to bring them up to ,' ~ ~
mab/ f~) - 22~-83-0070 J ~3~3~33~
the required operating temperature. The prior art also teaches replacing the coiled wire heating element with a spiral wound flat tape type heating element as disclosed by Knowles in V.S. Pa~ent 41297,785. Alternatively 5 Yamamoto et al in U . S . Patent 4 ~ 357,526 and Sagawa et al in U.S. Patent 4,035,613 teach a discrete printed circuit heating element imbedded in a ceramic body. ~owever, all of these glow plugs still exhibit the same slow thermal response and relatively high electrical power requirement 5 .
In contrast to the glow plugs described above, Knoll et al in British Patent ~pplication 2,092,670-A published August 18, 1982, disclose a glow plug having a layered platinum-rhodium alloy surface film heater element applied to the base of a closed end ceramic tube.
~ he Applicant in co-pending commonly assigned Patent Application Serial No. 430,909, filed September 30, 19~2 disclosed a similar glow plug having a transition metal surface film heater element circumfrentially coated on a surface of a cylindrical ceramic substrate adjacent to it's end. Tests of the glow plug disclosed in Patent Applica~ion 430,909 exhibited improved performance, however, contact oorrosion at the opposite ends of ~he surface film heater element where electrical contac~ was 25 made to the outer shell and axial electrical terminal were encountered during life tests. The invention is an improved embodiment of the surface film heater type glow plug which is more efficient than the glow plug disclosed by Rnoll et al, is easier to make, and solves the contact 30 problems encountered in the former design.
Summary of_the Invention The invention is a glow plu~ for an internal combustion 35 engine having a cylindrical metal shell, an axial 223-~3-0070 ~.~3~37' electrical terminal located concentrically in said shell and electrically insul ted therefrom and a surface film heater member electrically connected between the metal shell and the axial electrode. The hea er member comprises a cylindrical nonconductive substrate having one end internally captivated between one end of the shell and the axial electrical terminal, and the other end of the heater member protruding externally from the shell. A concen~ric bore passes through said subs~rate.
A resistive surface film heater element is coated on at least one surface of the substrate adjacent to ~he external end. A first conductive surface film coated on the external surface of the substrate connects one end of the heater element to the shell. A second conductive surface film coated on at least the internal surface of the substrate connects the other end of the heater element with the axial electricaI terminal. Preferably the heater element is a ransition metal of the platinum family.
One advantage of the glow plug is that the cylin-drical heating element forms a hot cul-de-sac region isolated from the cooling effects of impringing air/fuel mixture and enhances ignition.
Another advantage of the glow plug is that both 25 connections between the heater element, the shell and the axial electrical terminal are made internal to the shell and not exposed to the high temperature and corrosive atmosphere of the engine. Still another advantage of the glow plug is that the heater element is located at the tip of the ceramic substrate minimizing the protrusion needed into the engine ~ s ignition chamber reducing interference of the glow plug with the ignition chamber's air flow pattern. These and other advantages of the improved glow plug will become more apparent from a 223~~3-007 0 ~.~3~3~
reading of the specification in conjunction with the drawingsv Brief DescriPtion of the Fiqures FIGURÆ 1 is a cross section of the improved embodiment of the glow plug.
FIGUR~ 2 is an enlarged cross-section showing the de~ails of ~he heater member.
10FIGURE 3 is an enlarged cross-section of a second embodiment of the heater member.
FIGURE 4 is an enlarged cross-section of a third embodiment of the heater member.
FIGURE 5 is a cross-section showing the glow plug mounted in the swirl chamber of a diesel type internal combustion engine.
Detailed Description of the Invention 20A cross-sectional view of the glow plug is shown in FIGURE 1. The glow plug 10 comp~ises a cylindrîcal metal shell 12 having an internal bore 14. Formed at one end of the shell 12 is a contact seat 16 ~efining a heater aperture 18. Located in the internal bore 14 is a heater 25 member 20 having a resistive surface film heater element 24 coated or disposed on at least one surface of a non-conductive substrate 22 adjacent to one end thereof ~sshall be described hereinafter. The nonconductive substrate ~2 is preferably a high temperature ceramic, but may be quartz, a high temperature glass, or metal sleeve coated with an insulating material. The substrate has an internal bore 2Ç, a base or internal portion 28 disposed in shell 12 and a smaller dlameter external portion 30 protruding external to the shell 12 through the heater aperture 18. Heater aperture 18 has a ~36~
diameter smaller than the diameter of internal portion 28 of the æubstrate 22 and larger than the diameter of external portion 30.
An axial electrical terminal 36 has a radial flange 38 and guide 40 formed at one end. The guide 40 is received into the internal bore 26 of substrate 22 wi~h one face of the radial flange 38 abutting the internal end face 42 of the substrate 22 with a orce sufficient to deform an electrically conductive gasket 32 interposed between a shoulder 34 of the substrate 22 and the shell contact seat 16. The conduc~ive gasket 32 may be copper, gold or any other maleable metal or alloy.
A cylindrical insulator member 44, similar to the insulator commonly used in spark plugs, is inserted in bore 14 circumscribing axial electrical terminal 36 and abutting the opposite face of radial flange 38. The end of the shell 12 is crimped over to form a peripheral lip 46. The insulator member 44, axial electrical terminal 36 and heater member 20 are then locked tightly inside of shell 12 by a hot press operation which heats, then cools and undercut groove 9S while a compressive force is applied between peripheral lip 46 and the opposing end 96 of an external hexagonal portion 50. The shell 12 further includes an externally threaded portion 48 for 25 mounting the glow plug 10 in the engine. The external hexagonal portion 50 facilitates threading the glow plug into an appropriate threaded aperture of the engine.
One advantage of the glow plug shown in FIGURE 1 is that the electrical connections between the surface film 30 heater element 24, ~he shell 12, and the axial electrical terminal 36 are made internal to the shell 12 where they are protected from ~he high temperatures and corrosive atmosphere inside of the engine. This configuration eliminates the electrical terminal corrosion problems 35 encountered with the prior designs.
3~37 The details of the heater member 20 are illustrated in FIGURE 2. Referring to FIGURE 2, the heater member 20, as previously described, has a generally cylindrical substrate 22 having an internal bore ~6, an internal portion 28; a smaller diameter external portion 3~0 and a sloped shoulder 34 connecting the external surfaces of the internal portion 2~ and external portion 30. The edges a~ end face 52 of the substrate 22 are ground to form radii blending the end face 52 with the contiguous internal surface of bore 26 with the external surface of the substrate or may be ground to form a full radius as shown. In a similar manner a ground radius 54 is formed at the base of the substrate blending the end face 42 with the internal surface of bore 26.
A higbly conductive metal film 56 is circumferen-tially coated on the surface of shoulder 34 and a predetermined distance along the external surface of the ex~ernal portion 30 of the substrate .leaving a first uncoated portion 60 adjacent to end fice 42 and a second 20 uncoated portion 64 adjacent to end face 52. A similar highly conductive metal film 58, is coated on the internal surface of cylindrical substrate 22 and ex~ends around radius 54 onto end face 42 as shown. The metal film on the end face 42 has a diame~er smaller than the 25 diameter of the internal portion 28 leaving an uncoated peripheral portion 62. The highly conductive metal films 56 and 5B ~ay be transition metal films, gold films, alloys thereof or any other metal or metal alloy films.
A resistive metal surface film heater element 24, 30 having a resistance greater ~han 0.2 ohms is deposited on the uncoated portion 64 of the substrate and on end face 52. Preferably the resistance of heater element 24 is between 0~4 and 0.6 ohms. ~eater element 24 and the conductive metal films 56 and 58 overlap providing for electrical contact therebetween. Preferably the resis-223-~3-0070 ~ ~3C~3~7 tive metal of heater element 24 is of the platinum family consisting of pla~inum, rhodium, palladium, iridium and alloys thereof. Alloys having higher melting tempera-tures, such as alloys containing tungsten and at least one transition metal may be used ~o increase the operating temperature of ~he glow plu90 The primary advantage of the cylindrical configura-tion of the hea~er member is tha~ the bore 26 form a high temperature cul-de-sac adjacent to its open end which i5 isolated from the cooling effects of the swirling air/
fuel mixture in the en~ine's ignition chamber. The air/fuel misture ent~ring the high temperature cul-de-sac formed by bore 26 is more readily ignited than the air/fuel mixture impringing on the external surfaces of the heater member enhancing the ignition efficiency of the glow plug.
In the assembly of the glow plug one end of the heater element 24 is in electrical contact with the shell 12 through surface film 56 on shoulder 34 and 20 electrically conductive gasket 32 while other end of heater element is in electrical con~act with axial electrical ~erminal 36 through surface film 58 on the internal surface of bore 26 and radial flange 38 abutting the extention of surface film 58 onto the end face 42.
In an alternate embodiment of the heater member 20 shown in FIGURE 3, the bore 26 of the substrate 22 is tapered outwardly at end 52 to enhance the depth at which the heater element 24 may be coated into bore 26. This : . permi~s the heater element 24 to wrap around end face 52 and extend a short distance into bore 26 as shown. This further enhances the formation of the high temperature cul-de-sac as previously described.
In contrast to the arrangement shvwn on Figures and 3 the heater element 24 may be coated on the internal 35 surface of the ceramic substrate defined by bore 26 as 223-83~0070 .
~ Z3C~3~
shown on Figure 4. In this confiyuration the ~onductive metal film 56 extends along the external surface of the substrate adjacent ~o end face 52. ~he conductive metal film 58 extends along the internal surface of the sub-strate and onto end face 42 as in the prior embodiments.
This configuration further enhances the high temperature cul-de-sac formed in the bore 26 of ceramic subs~ra~e adjacen~ to the external end face 52.
Because the heater element 24 is located adjacent to the tip of the glow plug, it is no longer required for the glow plug to pro~rude fully into the ignition chamber of the engine. Referring to FIGURE 5 there is illustrated a typical swirl chamber 68 of a diesel type engine having an aperture 70 communicating with the corresponding engine cylinder. As is known in the art, air is pumped in and out of the swirl chamber 68 with the reciprocation of the cylinder's piston as indicated by dashed double headed arrrow 72. Fuel ~rom a Fuel Injector 74 is injected into the swirl chamber where it is mixed with the swirling air to form a combustible air/fuel mix~ure. Because the heater element 24 of the improved glow plug 10 is formed at the tip of the substrate 22, only the ~ip of the glow plug need to pro-trude into the swirl chamber 68 as shown. In this way 25 the glow plug 10 produces minimal in~erference with the swirling air pattern inside of chamber 68. In fact, tests conducted to date indicate efficient ignition of the air fuel mixture can be obtained with the glow plug mounted in the glow plug well 76 with the tip disposed 30 flush with the internal walls of the swirl chamber 68.
The advantages of the improved glow plug are ~s follows:
1. The low mass of the surface film heater element 24 permits the glow plug to reach an vperational 35 temperature above 800C in less than 5 seconds, ~3C~3~
20 The ~att density of the surface film heater element 24 exceeds ~hat of bulk material giving rise to current requirements averaging in the range from 3 to 7 amps at operating temperatures.
53. The transition me~al heater ~element 24 exhibits catalytic action enhancing the ignition of the air/fuel - mixture at lower temperatures.
4. The internal surface of the heater member 20 adjacent to external end face 52 remains at the ignition temperature of the air/fuel mixture regardless of the cooling from fuel or air in the ignition chamber.
5. Because the heater element 24 is located at the tip of the glow plug~ only the tip of the glow plug needs to protrude into the ignition chamber producing only minimum interference with the ignition chamber's fluid flow pattern.
6. The electrical ~ontacts ~o the conductive sur-face films 56 and 58 are made within the shell 12 reducin~ their exposure to the higher engine temperatures reducing their oxidation and corrosion.
7. The components of the glow plug are applicable to standard spark plug manufacturing techniques and therefore are potentially less costly than glow plugs using spiral wound wire heaters.
25It is recognized that the conf iyuration of the various elements of the glow plug may be changed from those shown on the drawings withou~ departing from the spirit o~ the inven~ion as described herein and se~ forth in the appended claims.
Claims (9)
1. A glow plug having a hollow cylindrical metal shell (12), an axial electrical terminal (36) disposed concentrically in said shell and insulated therefrom, and a heater member (20) electrically connected between the metal shell (12) and the axial electrical terminal (36) characterized by:
an electrically nonconductive cylindrical substrate (22) having an internal portion (28) captivated between one end of the shell (12) and the electrical terminal (36), an external portion (30) protruding external from the shell (12) and the electrical terminal (36), an external portion (30) protruding external from the shell (12), and a concentric bore (26) passing through said substrate (22);
a resistive surface film heater element (24) disposed on at least one surface of said external portion (30) adjacent to the external end of said cylindrical substrate (22);
a first conductive surface film (56) disposed on the external surface of said cylindrical substrate (22) connecting one end of the heater element (24) with the shell (12); and a second conductive surface film (58) disposed on at least the internal surface of said concentric bore (26) connecting the other end of said heating element (24) with said electrical terminal (36).
an electrically nonconductive cylindrical substrate (22) having an internal portion (28) captivated between one end of the shell (12) and the electrical terminal (36), an external portion (30) protruding external from the shell (12) and the electrical terminal (36), an external portion (30) protruding external from the shell (12), and a concentric bore (26) passing through said substrate (22);
a resistive surface film heater element (24) disposed on at least one surface of said external portion (30) adjacent to the external end of said cylindrical substrate (22);
a first conductive surface film (56) disposed on the external surface of said cylindrical substrate (22) connecting one end of the heater element (24) with the shell (12); and a second conductive surface film (58) disposed on at least the internal surface of said concentric bore (26) connecting the other end of said heating element (24) with said electrical terminal (36).
2. The glow plug of Claim 1 wherein said heater element (24) is a metal film having a resistance greater than 0.2 ohms.
3. The glow plug of claim 2 wherein said heater element (24) is a transition metal film selected from the platinum family comprising platinum, palladium, iridium and rhodium.
4. The glow plug of claim 1 wherein said heater element (24) is a metal alloy film having a resistance greater than 0.2 ohms.
5. The glow plug of claim 4 wherein said metal alloy film has at least one constituent selected from the platinum family comprising platinum, palladium, iridium and rhodium.
6. The glow plug of claim 2 wherein said heater element (24) is a 4 to 8 millimeter wide band circumscribing said at least one surface of said cylindrical substrate (22) adjacent to the external end (52) of said cylindrical substrate (22).
7. The glow plug of claim 5 wherein said at least one surface is the external surface of said cylindrical substrate (22), said heater element (24) is further disposed a short distance along the internal surface of said concentric bore (26) adjacent to said external end (52).
8. The glow plug of claim 1 wherein said first and second conductive surface films (56 and 58) are metal films having a resistance of less than 0.2 ohms.
9. The glow plug of claim 1 wherein said cylindrical substrate (22) is a ceramic substrate.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US50725483A | 1983-06-23 | 1983-06-23 | |
| US507,254 | 1983-06-23 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1230937A true CA1230937A (en) | 1987-12-29 |
Family
ID=24017878
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000456162A Expired CA1230937A (en) | 1983-06-23 | 1984-06-08 | Glow plug having a resistive surface film heater |
Country Status (7)
| Country | Link |
|---|---|
| EP (1) | EP0129676B1 (en) |
| JP (1) | JPS6017632A (en) |
| AU (1) | AU2795084A (en) |
| BR (1) | BR8402891A (en) |
| CA (1) | CA1230937A (en) |
| DE (1) | DE3464660D1 (en) |
| ES (1) | ES533650A0 (en) |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4694145A (en) * | 1985-02-15 | 1987-09-15 | Allied Corporation | Electronic controller for predetermined temperature coefficient heater |
| US4816643A (en) * | 1985-03-15 | 1989-03-28 | Allied-Signal Inc. | Glow plug having a metal silicide resistive film heater |
| EP0194535A3 (en) * | 1985-03-15 | 1988-01-07 | Allied Corporation | Glow plug having a metallic silicide resistive film heater |
| US4682008A (en) * | 1985-03-22 | 1987-07-21 | Jidosha Kiki Co., Ltd. | Self-temperature control type glow plug |
| DE3614226A1 (en) * | 1986-04-26 | 1987-10-29 | Bosch Gmbh Robert | DEVICE FOR INJECTING FUEL IN THE COMBUSTION ROOM OF INTERNAL COMBUSTION ENGINES |
| JPS6361662U (en) * | 1986-10-09 | 1988-04-23 |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE1194201B (en) * | 1961-10-25 | 1965-06-03 | Maschf Augsburg Nuernberg Ag | Glow plug for internal combustion engines |
| DE2900984C2 (en) * | 1979-01-12 | 1983-01-05 | W.C. Heraeus Gmbh, 6450 Hanau | Glow plug for diesel engines |
| JPS55125363A (en) * | 1979-03-20 | 1980-09-27 | Toyota Central Res & Dev Lab Inc | Self-heating ignitor |
| US4418661A (en) * | 1981-02-07 | 1983-12-06 | Robert Bosch Gmbh | Glow plug, particularly for diesel engine |
-
1984
- 1984-05-02 EP EP84104882A patent/EP0129676B1/en not_active Expired
- 1984-05-02 DE DE8484104882T patent/DE3464660D1/en not_active Expired
- 1984-05-11 AU AU27950/84A patent/AU2795084A/en not_active Abandoned
- 1984-06-08 CA CA000456162A patent/CA1230937A/en not_active Expired
- 1984-06-13 BR BR8402891A patent/BR8402891A/en unknown
- 1984-06-22 ES ES533650A patent/ES533650A0/en active Granted
- 1984-06-22 JP JP12772684A patent/JPS6017632A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| JPS6017632A (en) | 1985-01-29 |
| ES8601581A1 (en) | 1985-10-16 |
| AU2795084A (en) | 1985-01-03 |
| BR8402891A (en) | 1985-05-21 |
| ES533650A0 (en) | 1985-10-16 |
| DE3464660D1 (en) | 1987-08-13 |
| EP0129676A1 (en) | 1985-01-02 |
| EP0129676B1 (en) | 1987-07-08 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |