EP0650020B1 - A ceramic heater and a method of manufacture thereof - Google Patents
A ceramic heater and a method of manufacture thereof Download PDFInfo
- Publication number
- EP0650020B1 EP0650020B1 EP19940307544 EP94307544A EP0650020B1 EP 0650020 B1 EP0650020 B1 EP 0650020B1 EP 19940307544 EP19940307544 EP 19940307544 EP 94307544 A EP94307544 A EP 94307544A EP 0650020 B1 EP0650020 B1 EP 0650020B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- enclosure
- ceramics
- coil
- ceramic heater
- ceramic
- 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 - Lifetime
Links
Images
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
-
- 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
- F23Q2007/004—Manufacturing or assembling methods
Definitions
- the present invention relates to a ceramic heater that forms a ceramic glow plug used with diesel engines and also to a method of manufacturing the ceramic heater.
- a ceramic glow plug conventionally has its heater portion consisting of a high-melting point metal such as tungsten and an Si 3 N 4 formed integral during a hot-press process.
- a conventional current self-control type glow plug is not satisfactory in terms of heat durability, strength against thermal shocks and high-temperature resistance when it is used in high-temperature combustion chambers in heat-insulated engines. Because the self-control type glow plug is made by connecting a heating coil made from a tungsten wire and a resistor coil made from a nickel wire, both with different resistance-temperature coefficients, there are drawbacks of complex structure, high cost and insufficient strength.
- the metal coil such as tungsten wire is embedded in ceramics and sintered during the forming process, so that the sintering requires application of pressure.
- a hot-press i.e., a single axis pressure sintering is usually performed.
- the metal coil embedded in the ceramics is therefore limited in the shape and takes a two-dimensional structure, giving rise to a problem that a gap is formed between the wall surface of the ceramic enclosure and the metal coil, reducing the heat conductivity and the quick-heating capability of the ceramic heater.
- a gap is formed in the boundary between the tungsten wire and the Si 3 N 4 , resulting in ingress of water or oxygen through the gap to cause corrosion.
- a glass sealing may be employed but this increases the number of steps in the manufacture process, lowering the reliability.
- the heater portion is formed of a sintered ceramics that consists of a heater coated with a ceramic coating layer applied by a vapor deposition method.
- a heating resistor wire formed of a high melting point metal such as tungsten (W), molybdenum (Mo) and rhenium (Re) or their alloys is embedded in an Si 3 N 4 sintered body and an intermediate layer, which is made from the same metal elements as the major constituent elements of the resistor wire or non-oxidized ceramics such as nitrides, carbides, silicides or silicified carbide of these metals, is formed over the surface of the resistor wire.
- a sheath type resistor having a greater positive resistance-temperature coefficient than the heater tungsten coil is used as a current control element and connected in series with the heater coil in the glow plug, with the heater coil embedded in a bar-shaped ceramics, to improve the heat conductivity and self-control the electricity supplied to the heating coil thereby improving the heating characteristics and preventing overheating of the heater portion.
- a self-control type glow plug disclosed in Japanese Patent Publication No. 34052/1992 has a current control resistor connected in series with a heating body to control the heating body temperature when a current is being supplied and the temperature is rising.
- the heating coil and the resistor coil are connected in series and embedded in a ceramic sintered material, thus forming an integral ceramic heater.
- the heating coil is made from a tungsten-rhenium alloy wire which has a positive resistance-temperature coefficient of less than four times, and the resistor coil is made of a pure tungsten wire or a pure molybdenum wire.
- a sheathed glow plug disclosed in Japanese Patent Publication No. 19404/1985 is a self-control type sheathed glow plug, in which a heating coil and a resistor coil are directly connected to each other between the inner bottom of a heat resisting, bottomed metal tube and a center electrode, with the winding pitch of the resistor coil made dense in an area close to a mounting fitting on the central electrode side and coarse in an area close to the heating body side.
- a glow plug for diesel engine disclosed in the Japanese Patent Laid-Open No. 141424/1987 has a cylindrical ceramic heater mounted at the front end portion of a hollow holder.
- the ceramic heater consists of a thin plate insulator made of insulating ceramics and a thin plate resistor made of conductive ceramics stacked over the side surfaces and one end portion of the thin plate insulator, these laminated thin plate insulator and resistor being bent widthwise to form a cylindrical body.
- a protective pipe of conductive ceramics is fitted over the outer circumference of the rear end of the cylindrical body. The protective pipe and the cylindrical body are then sintered to be formed as an integral one-piece structure.
- a primary aim of this invention is to solve the above-mentioned problems by providing a ceramic heater comprising the features of claim 1 and a method of manufacturing a ceramic heater according to claim 12.
- the ceramic heater according to the invention can improve the heat conductivity, prevent ingress of water or oxygen from the boundary between the metal coil and the enclosure ceramics in the heater portion, reduce manufacturing cost and assure a stable strength and improved reliability.
- the portion of the metal coil arranged in contact with the inner wall surface of the front end portion of the enclosure where the filler is disposed constitutes a heater coil
- the second portion of the metal coil spaced from the inner wall surface of the enclosure where the low heat conductivity ceramics is disposed constitutes a current control coil.
- the heat generated by the heater coil heats the enclosure and is dissipated outside.
- the heat generated by the current control coil is insulated by the low heat conductivity ceramics, raising the temperature of the current control coil.
- the temperature of the current control coil increases, its resistance also increases, limiting the current flowing through the current control coil or the whole metal coil. That is, an elevated temperature of the current control coil increases its resistance and reduces the current flowing through the metal coil, thus self-controlling the amount of heat dissipated from the enclosure to an optimum level.
- the enclosure is formed of Si 3 N 4 and its end surfaces are hermetically closed with sealing films to seal the interior of the enclosure.
- the sealing films are made from glass or the same kind of ceramics as that of the enclosure.
- the metal coil is made from a tungsten wire, whose surface is coated with a ceramic film formed by the chemical vapor deposition (CVD) or with an organic silicon polymer-converted ceramic film.
- CVD chemical vapor deposition
- the porous ceramics is a non-contracting ceramics that is made by sintering the material containing Si and Ti for reaction.
- the non-contracting ceramics contains Si 3 N 4 , TiN, TiO 2 , and TiON.
- the low heat conductivity ceramics is made from ceramic whiskers and/or ceramic powder and contains Si 3 N 4 and metal nitrides or metal oxides.
- the present invention also provides a method of manufacturing a ceramic heater including the steps according to claim 12.
- a preferred embodiments of the present invention are developped in the ceramic heater manufacturing methods according to claims 13 to 16.
- the enclosure is made of an Si 3 N 4 dense ceramics
- TiN is generated from the reaction of Si and Ti during the baking process. Because TiN expands during baking, the porous ceramics generated from baking and containing TiN slightly expands, causing the sintered Si 3 N 4 to adhere to the enclosure Si 3 N 4 . Further, if baking is performed without applying pressure, the expansion of TiN prevents formation of any gap in the boundary between the enclosure and the filler. Hence, the metal coil, even if formed in a three-dimensional shape, can be maintained in good contact with the enclosure, improving the heat conduction efficiency and permitting a fast temperature rise at the heater portion.
- an N2 gas in the enclosure is sealed in the enclosure during the baking process by closing the end surfaces of the enclosure with sealing films such as ceramics. Since an N 2 gas can be sealed in the enclosure during the baking process, the number of manufacturing steps can be reduced, lowering the cost. Moreover, the sealed N 2 gas improves corrosion resistance and durability of the metal coil, which is made, for example, of a tungsten wire.
- the heater coil which forms the heater portion
- the temperature of the whole enclosure rises uniformly.
- This ceramic heater which is incorporated in a ceramic glow plug of current self-control type built into a diesel engine, consists of: a pipe-shaped enclosure 1 made from dense ceramic with open ends; fillers 2, 3 made from porous ceramics and filled inside the ends of the enclosure 1; a sealing film 4 attached to the ends of the enclosure 1 to seal the interior of the enclosure 1; a low heat conductivity ceramics 5 installed in the central portion of the enclosure 1 and sealing an N 2 gas; and a metal coil 10 installed inside the enclosure 1.
- the fillers 2, 3 are filled in the enclosure 1 in such a way as to contact the inner wall surfaces 7, 14 of the enclosure 1.
- the metal coil 10 is a resistor wire made from a high melting point metal such as tungsten and consists of a heater coil 6 and a current control coil 9.
- the heater coil 6 is installed in the front end part of the enclosure 1 where the filler 2 is filled, in such a way that the heater coil contacts the inner wall surface 7 of the enclosure 1.
- the current control coil 9 is installed in a part of the enclosure where the N 2 gas is sealed, in such a way that it is spaced from the inner wall surface 8 of the enclosure 1.
- the metal coil 10 also has a connecting wire 11 that connects one end of the heater coil 6 and one end of the current control coil 9; a connecting wire 12 that connects to the other end of the heater coil 6, extends through the interior of the enclosure 1 and projects from the porous ceramics filler 3; and a connecting wire 13 that connects to the other end of the current control coil 9, extends through the interior of the enclosure 1 and protrudes from the porous ceramics filler 3.
- the surface of the metal coil 10 is coated with a ceramic film.
- the porous ceramics forming the fillers 2, 3 contains Si and Ti which, when baked, are transformed into Si 3 N 4 and TiN, respectively. TiN is further transformed into more stable materials TiO 2 and TiON through oxidation.
- the sealing film 4 attached to the ends 15 of the enclosure 1 and to the end surface of the fillers 2, 3 are made from glass material such as polymer precursor or the same ceramics as that of the enclosure 1.
- the enclosure 1 is formed of a dense Si 3 N 4 ceramics.
- the low heat conductivity ceramics 5 is made of either SiC whisker, Si 3 N 4 whisker, Al 2 O 3 whisker, Al 2 O 3 -SiO 2 whisker, ceramic powder or Si 3 N 4 porous material.
- the ceramics around the current control coil 9 be made from a material having as low a heat conductivity as air. Further, during the baking process, an N 2 gas is sealed in a part of the enclosure 1 where the low heat conductivity ceramics 5 is located in order to prevent oxidation of the metal coil 10.
- One end of the enclosure 1 is secured to a hollow body that has an electrode mounted in a hollow portion thereof through an insulator such as insulating bushing.
- the hollow body is made from a metal such as heat resistant alloy and has a thread for mounting to other component.
- the end of the connecting wire 13 is connected to the electrode and the end of the connecting wire 12 is connected to the hollow body. Therefore, in this ceramic heater, electric current flows from the electrode to the connecting wire 13 to the current control coil 9 to the connecting wire 11 to the heater coil 6 to the connecting wire 12 to the hollow body.
- This ceramic heater can be manufactured as follows. First, the enclosure 1 is made from a dense ceramics and the surface of the metal coil 10 of, say, tungsten wire is covered by the chemical vapor deposition (CVD) with ceramics, such as SiC, that has a thermal expansion coefficient almost equal to that of the metal coil 10. Next, the ceramics-coated metal coil 10 of tungsten wire is installed inside the enclosure 1 so that it contacts the inner wall surface 7 of one end portion of the enclosure 1 but does not contact the inner wall surface 8 of the intermediate portion of the enclosure 1.
- CVD chemical vapor deposition
- a material containing Si and Ti is filled inside the end of the enclosure 1, a material containing a low thermal conductivity ceramics 9 such as SiC whisker and Si 3 N 4 porous material is filled inside the intermediate portion of the enclosure 1, and a material containing Si and Ti is filled inside the other end.
- the enclosure 1 filled with the Si/Ti-containing material and with the low heat conductivity ceramic material is baked for reaction in the presence of N 2 gas to transform the material containing Si and Ti into porous ceramics such as Si 3 N 4 , TiN, TiO 2 and TiON, thereby converting the materials into fillers 2, 3.
- this ceramic heater formed in a way mentioned above has improved adherence of the heater coil 6 and the filler 2 to the inner wall surface 7 of the enclosure 1, resulting in an improved heat conduction, which in turn allows for an immediate temperature rise.
- Another advantage of this ceramic heater is that the manufacturing process has a fewer number of fabrication steps and therefore is simple, reducing the cost and improving reliability of the ceramic heater built into the ceramic glow plug.
- tungsten (W) wire 0.2 mm in diameter was wound into a coil 3.5 mm in outer diameter.
- the coiled tungsten wire was then covered over its surface with SiC by the CVD.
- SiC-coated tungsten wire coil arranged in a porous mold such as plaster mold for slip cast, a 85:15 Si/Ti slurry was poured in a specified amount into the porous mold.
- an SiC whisker in a slurry state is poured onto the semi-solidified slurry in the porous mold.
- the above-mentioned Si/Ti slurry was poured in a specified amount onto the SiC whisker n the porous mold.
- the water in the slurry was absorbed through the porous mold until the slurry solidified completely.
- a molded body was obtained in which a material containing Si and Ti was put around the tungsten coil, with the SiC whisker disposed in the intermediate portion of the enclosure.
- the molded body was taken out of the porous mold and dried in the presence of N 2 gas.
- the dried molded body was inserted into the enclosure 1, a pipe-shaped cylinder made of dense Si 3 N 4 with a relative density of more than 99%.
- the outer diameter of the molded body and the inner diameter of the enclosure 1 were almost equal with virtually no gap between them.
- the molded body inserted into the enclosure 1 was baked in a furnace that contained 5 atm of N 2 gas heated up to 1,400°C to convert the Si and Ti components of the material into the baked nitrides such as Si 3 N 4 and TiN, i.e., porous ceramics fillers 2, 3.
- the SiC whisker was transformed into a low heat conductivity ceramics member 5 having N 2 gas sealed therein. No gap was formed in the boundary between the baked body and the enclosure 1 because of the TiN expansion of about 0.2% during the baking process.
- the end surfaces 15 of the enclosure 1 and the porous ceramics fillers 2, 3 are coated by the CVD with Si 3 N 4 to completely seal N 2 gas in the intermediate portion of the enclosure 1.
- the tungsten wire coil was immersed in a toluene solution of polycarbosilane, an organic silicon polymer, and was heated to a specified temperature in the presence of N 2 gas to convert the organic silicon polymer into Si 3 N 4 .
- the above process was repeated five times to form a ceramic film about 50 ⁇ m thick over the surface of the tungsten wire coil.
- This ceramics-coated tungsten wire coil was used to fabricate the ceramic heater in the same process as the first embodiment.
- a slurry of only Si instead of a Si/Ti mixture was used for filling the interior of the end portions of the enclosure 1 and, for the intermediate portion of the enclosure 1, the same SiC whisker slurry as in the first embodiment was used to manufacture the ceramic heater in the same process as the first embodiment.
- the porous ceramics that forms the fillers 2, 3 was a porous Si 3 N 4 .
- a further example used a 80:20 Si/Si 3 N 4 slurry instead of the Si/Ti slurry for filling the interior of the end portions of the enclosure 1.
- the same process as the first embodiment was followed to fabricate the ceramic heater.
- the porous ceramics forming the fillers 2, 3 was a porous Ni 3 N 4 .
- Still another example used an Si slurry instead of the Si/Ti slurry for filling the interior of the end portions of the enclosure 1.
- an Si slurry was also used instead of SiC whisker slurry.
- a ceramic heater was fabricated in the same process as the first embodiment.
- the porous ceramics forming the fillers 2, 3 was a porous Si 3 N 4 and the porous ceramics forming the low heat conductivity ceramic member 5 was an Si 3 N 4 porous material.
- the ceramic heater according to this invention can be fabricated in ways described in the above embodiments. Although there are slight variations in temperature vise time with respect to current supply time, almost similar effects can be produced.
- the ceramic heater is used with a ceramics glow plug built into a diesel engine and is formed as a two-layer structure consisting of an inner shell and an outer shell 21.
- the ceramics of the inner shell in which a metal coil 30 as a heater wire is embedded uses a ceramics that expands during baking.
- the outer shell 21 is formed into a pipe-shaped shell made from a dense ceramics which contains fillers 22, 23 of non-contracting ceramics in the end portions thereof. In the central portion of the outer shell 21 is installed a low heat conductivity ceramics member 25.
- the metal coil 30 is installed in the fillers 22, 23 and the low heat conductivity ceramic member 25 inside the outer shell 21.
- the outer shell 21 is made from a dense ceramics such as silicon nitride Si 3 N 4 and has one end thereof formed as a closed end 35 and the other end as an open end. Further, the outer shell 21 is formed with fine holes 36 such as slits piercing through the wall and running in the longitudinal direction or holes piercing through the wall. Through these fine holes gases present in the interior of the outer shell are evacuated to create a vacuum inside during the manufacture process. With the fine holes 36 formed in the outer shell 21, it is possible to sinter the Si and Ti materials installed in the outer shell 21 while applying pressure three-dimensionally during gas-pressure baking.
- the non-contracting ceramics that forms the fillers 22, 23 filling the interior of the end portions of the outer shell 21 is made by baking the material containing Si and Ti and transforming them into a porous ceramics containing Si 3 N 4 , TiN, TiO 2 and TiON.
- the volume of Si and Ti before backing is virtually equal to that of Si 3 N 4 , TiN, TiO 2 and TiON combined after baking.
- the material of the fillers does not contract when subjected to baking. Hence, no gap is formed in the boundary between the inner wall surfaces 27, 34 of the dense Si 3 N 4 outer shell 21 and the outer surfaces of the fillers 22, 23.
- the low heat conductivity ceramics 25 installed in the central portion inside the outer shell 21 is made from a ceramic powder, ceramic fibers or ceramic whiskers, all made of Si 3 N 4 and metal nitride or oxide. That is, the low heat conductivity ceramics 25 is made of such material as SiC whisker, Si 3 N 4 whisker, Al 2 O 3 whisker, Al 2 O 3 -SiO 2 whisker, ceramic powder or Si 3 N 4 porous material. It is desired from the standpoint of heat insulation that the ceramics around the current control coil 29 be formed of a material with a low heat conductivity almost equal to that of air.
- the metal coil 30 is made of a high-melting point metal wire such as a tungsten wire, which is formed into a three-dimensional coil. A portion of the coil arranged in contact with the inner wall surface 27 of the outer shell 21 constitutes a heater coil 6 and a portion of the coil spaced from the inner wall surface 34 of the outer shell 21 constitutes the current control coil 29.
- the metal coil 30 has a connecting wire 31 that connects one end of the heater coil 26 and one end of the current control coil 29; a connecting wire 32 that connects to the other end of the heater coil 26, extends along the inside of the outer shell 21 and projects from the filler 23 of the non-contracting ceramics; and a connecting wire 33 that connects to the other end of the current control coil 29, extends along the inside of the outer shell 21 and projects from the filler 23 of the non-contracting ceramics.
- This ceramic heater is assembled into a ceramic glow plug.
- One end of the outer shell 1 is secured to a hollow body that has an electrode mounted in a hollow portion thereof through an insulator such as insulating bushing.
- the hollow body is made from a metal such as heat resistant alloy and has a thread for mounting to other component.
- the end of the connecting wire 33 is connected to the electrode and the end of the connecting wire 32 is connected to the hollow body. Therefore, in this ceramic heater, electric current flows from the electrode to the connecting wire 33 to the current control coil 29 to the connecting wire 31 to the heater coil 26 to the connecting wire 32 to the hollow body.
- an outer shell 21 made of a dense ceramics is formed closed at one end 35 and open at the other end and, as shown in Figure 3, is formed with fine holes 36, such as slits that pierce through the wall and extend in the longitudinal direction and holes that pierce through the wall.
- a three-dimensionally wound metal coil 30 is made from, say, a tungsten wire.
- the tungsten wire coil 30 is installed inside the outer shell 21 in such a way that it contacts the inner wall surface 7 of one end portion of the outer shell 21 and is spaced from the inner wall surface 28 of the intermediate portion of the outer shell.
- a material containing Si and Ti is filled inside one end portion of the outer shell 21; a material containing a low heat conductivity ceramic member such as ceramic powder is filled inside the intermediate portion of the outer shell 21; and a material containing Si and Ti is filled inside the other end portion of the outer shell 21.
- the outer shell filled with the Si/Ti material and the low heat conductivity ceramics member 25 is sintered in an N 2 atmosphere at a gas pressure of less than 9.9 kgf/cm 2 to convert the Si/Ti material into a porous ceramics containing Si 3 N 4 , TiN, TiO 2 and TiON, i.e., into a non-contracting ceramics, to form the fillers 22, 23 and cause the non-contracting ceramics to adhere to the dense ceramics of the outer shell 21.
- the ceramics heater is then placed in a vacuum and, as shown in Figure 4, the fine holes 36 formed in the wall of the outer shell 21 are sealed with a sealing film 24 such as glass and brazing filler metal to hermetically enclose the interior of the outer shell 21, thus forming the ceramic heater.
- a sealing film 24 such as glass and brazing filler metal to hermetically enclose the interior of the outer shell 21, thus forming the ceramic heater.
- the heater coil 26 which constitutes a heater portion is in contact with the inner wall surface 27 of the outer shell 21 and is embedded in the non-contracting ceramic filler 22 that contacts the inner wall surface 27 of the outer shell 21.
- This construction allows the entire outer shell 21 to be heated uniformly and assures a very good heat conductivity of the heater portion, offering an improved heating performance that allows the heater portion to be heated quickly upon energization.
- Figure 5 shows a graph illustrating the relation between the temperature (°C) of the heater portion and the energizing time (second).
- the ceramic heater of this invention is represented by a broken line and the conventional glow plug by a solid line.
- Figure 5 shows that the heater of this invention can be heated to a specified temperature in a shorter energizing time than is required with the conventional heater, demonstrating the superior heating characteristic.
Description
- The present invention relates to a ceramic heater that forms a ceramic glow plug used with diesel engines and also to a method of manufacturing the ceramic heater.
- A ceramic glow plug conventionally has its heater portion consisting of a high-melting point metal such as tungsten and an Si3N4 formed integral during a hot-press process. A conventional current self-control type glow plug is not satisfactory in terms of heat durability, strength against thermal shocks and high-temperature resistance when it is used in high-temperature combustion chambers in heat-insulated engines. Because the self-control type glow plug is made by connecting a heating coil made from a tungsten wire and a resistor coil made from a nickel wire, both with different resistance-temperature coefficients, there are drawbacks of complex structure, high cost and insufficient strength.
- In the conventional current self-control type glow plug, the metal coil such as tungsten wire is embedded in ceramics and sintered during the forming process, so that the sintering requires application of pressure. Hence, a hot-press, i.e., a single axis pressure sintering is usually performed. The metal coil embedded in the ceramics is therefore limited in the shape and takes a two-dimensional structure, giving rise to a problem that a gap is formed between the wall surface of the ceramic enclosure and the metal coil, reducing the heat conductivity and the quick-heating capability of the ceramic heater.
- In the ceramics glow plug whose heater portion consists of a tungsten wire and an Si3N4 formed integral during the hot-press process, a gap is formed in the boundary between the tungsten wire and the Si3N4, resulting in ingress of water or oxygen through the gap to cause corrosion. To prevent entry of water or oxygen from the gap between the tungsten wire and the Si3N4 requires that the gap be sealed. For this purpose, a glass sealing may be employed but this increases the number of steps in the manufacture process, lowering the reliability.
- In a glow plug disclosed in Japanese Utility Model No. 15077/1989, the heater portion is formed of a sintered ceramics that consists of a heater coated with a ceramic coating layer applied by a vapor deposition method.
- In a ceramics heater disclosed in JP-A-1157084/1989, a heating resistor wire formed of a high melting point metal such as tungsten (W), molybdenum (Mo) and rhenium (Re) or their alloys is embedded in an Si3N4 sintered body and an intermediate layer, which is made from the same metal elements as the major constituent elements of the resistor wire or non-oxidized ceramics such as nitrides, carbides, silicides or silicified carbide of these metals, is formed over the surface of the resistor wire.
- Among the conventional current self-control type glow plugs is one disclosed by Japanese Patent Publication 59157423/1984. This uses two kinds of material, that is, a sheath type resistor having a greater positive resistance-temperature coefficient than the heater tungsten coil is used as a current control element and connected in series with the heater coil in the glow plug, with the heater coil embedded in a bar-shaped ceramics, to improve the heat conductivity and self-control the electricity supplied to the heating coil thereby improving the heating characteristics and preventing overheating of the heater portion.
- A self-control type glow plug disclosed in Japanese Patent Publication No. 34052/1992, for example, has a current control resistor connected in series with a heating body to control the heating body temperature when a current is being supplied and the temperature is rising. In this glow plug, the heating coil and the resistor coil are connected in series and embedded in a ceramic sintered material, thus forming an integral ceramic heater. The heating coil is made from a tungsten-rhenium alloy wire which has a positive resistance-temperature coefficient of less than four times, and the resistor coil is made of a pure tungsten wire or a pure molybdenum wire.
- A sheathed glow plug disclosed in Japanese Patent Publication No. 19404/1985 is a self-control type sheathed glow plug, in which a heating coil and a resistor coil are directly connected to each other between the inner bottom of a heat resisting, bottomed metal tube and a center electrode, with the winding pitch of the resistor coil made dense in an area close to a mounting fitting on the central electrode side and coarse in an area close to the heating body side.
- A glow plug for diesel engine disclosed in the Japanese Patent Laid-Open No. 141424/1987 has a cylindrical ceramic heater mounted at the front end portion of a hollow holder. The ceramic heater consists of a thin plate insulator made of insulating ceramics and a thin plate resistor made of conductive ceramics stacked over the side surfaces and one end portion of the thin plate insulator, these laminated thin plate insulator and resistor being bent widthwise to form a cylindrical body. A protective pipe of conductive ceramics is fitted over the outer circumference of the rear end of the cylindrical body. The protective pipe and the cylindrical body are then sintered to be formed as an integral one-piece structure.
- A primary aim of this invention is to solve the above-mentioned problems by providing a ceramic heater comprising the features of
claim 1 and a method of manufacturing a ceramic heater according toclaim 12. - The ceramic heater according to the invention can improve the heat conductivity, prevent ingress of water or oxygen from the boundary between the metal coil and the enclosure ceramics in the heater portion, reduce manufacturing cost and assure a stable strength and improved reliability.
- In this ceramic heater, the portion of the metal coil arranged in contact with the inner wall surface of the front end portion of the enclosure where the filler is disposed constitutes a heater coil, and the second portion of the metal coil spaced from the inner wall surface of the enclosure where the low heat conductivity ceramics is disposed constitutes a current control coil. Because the heater coil and the current control coil are formed of a single, continuous metal coil of, say, a tungsten wire, the metal coil can easily be made at low cost by using a ceramic coil making jig, which has a through-hole in the center and spiral grooves on its outer circumferential surface. The metal coil has improved electrical reliability and durability as there are no joints or connections in the coil.
- When a current is supplied to the metal coil, the heat generated by the heater coil heats the enclosure and is dissipated outside. On the other hand, the heat generated by the current control coil is insulated by the low heat conductivity ceramics, raising the temperature of the current control coil. As the temperature of the current control coil increases, its resistance also increases, limiting the current flowing through the current control coil or the whole metal coil. That is, an elevated temperature of the current control coil increases its resistance and reduces the current flowing through the metal coil, thus self-controlling the amount of heat dissipated from the enclosure to an optimum level.
- The enclosure is formed of Si3N4 and its end surfaces are hermetically closed with sealing films to seal the interior of the enclosure. The sealing films are made from glass or the same kind of ceramics as that of the enclosure.
- The metal coil is made from a tungsten wire, whose surface is coated with a ceramic film formed by the chemical vapor deposition (CVD) or with an organic silicon polymer-converted ceramic film.
- The porous ceramics is a non-contracting ceramics that is made by sintering the material containing Si and Ti for reaction. The non-contracting ceramics contains Si3N4, TiN, TiO2, and TiON.
- The low heat conductivity ceramics is made from ceramic whiskers and/or ceramic powder and contains Si3N4 and metal nitrides or metal oxides.
- The present invention also provides a method of manufacturing a ceramic heater including the steps according to
claim 12. - A preferred embodiments of the present invention are developped in the ceramic heater manufacturing methods according to
claims 13 to 16. - If the enclosure is made of an Si3N4 dense ceramics, TiN is generated from the reaction of Si and Ti during the baking process. Because TiN expands during baking, the porous ceramics generated from baking and containing TiN slightly expands, causing the sintered Si3N4 to adhere to the enclosure Si3N4. Further, if baking is performed without applying pressure, the expansion of TiN prevents formation of any gap in the boundary between the enclosure and the filler. Hence, the metal coil, even if formed in a three-dimensional shape, can be maintained in good contact with the enclosure, improving the heat conduction efficiency and permitting a fast temperature rise at the heater portion.
- Furthermore, because the ends of the enclosure are open, it is possible to easily seal an N2 gas in the enclosure, particularly in the intermediate portion of the enclosure, during the baking process by closing the end surfaces of the enclosure with sealing films such as ceramics. Since an N2 gas can be sealed in the enclosure during the baking process, the number of manufacturing steps can be reduced, lowering the cost. Moreover, the sealed N2 gas improves corrosion resistance and durability of the metal coil, which is made, for example, of a tungsten wire.
- In this ceramic heater, because the heater coil, which forms the heater portion, is placed in contact with the inner wall surface of the enclosure, the temperature of the whole enclosure rises uniformly. The construction of the heater portion, in which the heater coil is put in contact with the inner wall surface of the enclosure and embedded in the filler, offers a very good heat conduction, improving the fast-heating performance of the heater portion, that is, assuring a quick temperature rise upon energization.
- Rather than using the above-mentioned enclosure which is open at both ends, it is possible to employ a dense ceramic enclosure which is closed at one end and open at the other end and is formed with fine holes in the wall thereof. In this case, after the material containing Si and Ti is sintered and converted into a non-contracting ceramics, the fine holes in the enclosure need to be hermetically closed with sealing films in a vacuum.
- Preferred embodiments of the present invention will be described hereinbelow by way of example only with reference to the accompanying drawings, in which:
- Figure 1 is a cross section of a ceramic heater as one embodiment of this invention.
- Figure 2 is a cross section of a ceramic heater as another embodiment of this invention;
- Figure 3 is a plan view of one embodiment of an enclosure of the ceramic heater shown in Figure 2;
- Figure 4 is a plan view of the enclosure of Figure 3 with slits closed by a sealing film; and
- Figure 5 is a graph showing temperature rises of the ceramic heater of this invention and the conventional glow plug in connection with an energizing time.
-
- First, an embodiment of the ceramic heater according to this invention is explained by referring to Figure 1. This ceramic heater, which is incorporated in a ceramic glow plug of current self-control type built into a diesel engine, consists of: a pipe-
shaped enclosure 1 made from dense ceramic with open ends;fillers enclosure 1; asealing film 4 attached to the ends of theenclosure 1 to seal the interior of theenclosure 1; a lowheat conductivity ceramics 5 installed in the central portion of theenclosure 1 and sealing an N2 gas; and ametal coil 10 installed inside theenclosure 1. Thefillers enclosure 1 in such a way as to contact theinner wall surfaces enclosure 1. - The
metal coil 10 is a resistor wire made from a high melting point metal such as tungsten and consists of aheater coil 6 and acurrent control coil 9. Theheater coil 6 is installed in the front end part of theenclosure 1 where thefiller 2 is filled, in such a way that the heater coil contacts theinner wall surface 7 of theenclosure 1. Thecurrent control coil 9 is installed in a part of the enclosure where the N2 gas is sealed, in such a way that it is spaced from theinner wall surface 8 of theenclosure 1. Further, themetal coil 10 also has a connectingwire 11 that connects one end of theheater coil 6 and one end of thecurrent control coil 9; a connectingwire 12 that connects to the other end of theheater coil 6, extends through the interior of theenclosure 1 and projects from theporous ceramics filler 3; and a connectingwire 13 that connects to the other end of thecurrent control coil 9, extends through the interior of theenclosure 1 and protrudes from theporous ceramics filler 3. - The surface of the
metal coil 10 is coated with a ceramic film. The porous ceramics forming thefillers film 4 attached to theends 15 of theenclosure 1 and to the end surface of thefillers enclosure 1. Theenclosure 1 is formed of a dense Si3N4 ceramics. The lowheat conductivity ceramics 5 is made of either SiC whisker, Si3N4 whisker, Al2O3 whisker, Al2O3-SiO2 whisker, ceramic powder or Si3N4 porous material. It is preferred from the standpoint of heat insulation that the ceramics around thecurrent control coil 9 be made from a material having as low a heat conductivity as air. Further, during the baking process, an N2 gas is sealed in a part of theenclosure 1 where the lowheat conductivity ceramics 5 is located in order to prevent oxidation of themetal coil 10. - One end of the
enclosure 1 is secured to a hollow body that has an electrode mounted in a hollow portion thereof through an insulator such as insulating bushing. The hollow body is made from a metal such as heat resistant alloy and has a thread for mounting to other component. The end of the connectingwire 13 is connected to the electrode and the end of the connectingwire 12 is connected to the hollow body. Therefore, in this ceramic heater, electric current flows from the electrode to the connectingwire 13 to thecurrent control coil 9 to the connectingwire 11 to theheater coil 6 to the connectingwire 12 to the hollow body. - This ceramic heater can be manufactured as follows. First, the
enclosure 1 is made from a dense ceramics and the surface of themetal coil 10 of, say, tungsten wire is covered by the chemical vapor deposition (CVD) with ceramics, such as SiC, that has a thermal expansion coefficient almost equal to that of themetal coil 10. Next, the ceramics-coatedmetal coil 10 of tungsten wire is installed inside theenclosure 1 so that it contacts theinner wall surface 7 of one end portion of theenclosure 1 but does not contact theinner wall surface 8 of the intermediate portion of theenclosure 1. A material containing Si and Ti is filled inside the end of theenclosure 1, a material containing a lowthermal conductivity ceramics 9 such as SiC whisker and Si3N4 porous material is filled inside the intermediate portion of theenclosure 1, and a material containing Si and Ti is filled inside the other end. After this, theenclosure 1 filled with the Si/Ti-containing material and with the low heat conductivity ceramic material is baked for reaction in the presence of N2 gas to transform the material containing Si and Ti into porous ceramics such as Si3N4, TiN, TiO2 and TiON, thereby converting the materials intofillers enclosure 1 and particularly theheater coil 6 to adhere to theinner wall surface 7 of the enclosure. - Because the ends of the
enclosure 1 are open, N2 gas is sealed in theenclosure 1, particularly in the lowheat conductivity ceramics 5 filled in the intermediate portion of theenclosure 1 during baking. Further, the end surfaces 15 of theenclosure 1 are coated with the sealingfilms 4, made of the same kind of ceramics as that of theenclosure 1, to seal the interior of theenclosure 1. Therefore, compared with the conventional heaters, this ceramic heater formed in a way mentioned above has improved adherence of theheater coil 6 and thefiller 2 to theinner wall surface 7 of theenclosure 1, resulting in an improved heat conduction, which in turn allows for an immediate temperature rise. Another advantage of this ceramic heater is that the manufacturing process has a fewer number of fabrication steps and therefore is simple, reducing the cost and improving reliability of the ceramic heater built into the ceramic glow plug. - Next, an example embodiment of this ceramic heater is explained below.
- First, a tungsten (W) wire 0.2 mm in diameter was wound into a coil 3.5 mm in outer diameter. The coiled tungsten wire was then covered over its surface with SiC by the CVD. With the SiC-coated tungsten wire coil arranged in a porous mold such as plaster mold for slip cast, a 85:15 Si/Ti slurry was poured in a specified amount into the porous mold. Next, with the slurry solidified to a certain degree, an SiC whisker in a slurry state is poured onto the semi-solidified slurry in the porous mold. With the SiC whisker slurry solidified to a certain degree, the above-mentioned Si/Ti slurry was poured in a specified amount onto the SiC whisker n the porous mold. The water in the slurry was absorbed through the porous mold until the slurry solidified completely. With this process, a molded body was obtained in which a material containing Si and Ti was put around the tungsten coil, with the SiC whisker disposed in the intermediate portion of the enclosure.
- Then, the molded body was taken out of the porous mold and dried in the presence of N2 gas. The dried molded body was inserted into the
enclosure 1, a pipe-shaped cylinder made of dense Si3N4 with a relative density of more than 99%. The outer diameter of the molded body and the inner diameter of theenclosure 1 were almost equal with virtually no gap between them. The molded body inserted into theenclosure 1 was baked in a furnace that contained 5 atm of N2 gas heated up to 1,400°C to convert the Si and Ti components of the material into the baked nitrides such as Si3N4 and TiN, i.e.,porous ceramics fillers conductivity ceramics member 5 having N2 gas sealed therein. No gap was formed in the boundary between the baked body and theenclosure 1 because of the TiN expansion of about 0.2% during the baking process. Next, the end surfaces 15 of theenclosure 1 and theporous ceramics fillers enclosure 1. - In another example, rather than being coated with SiC by CVD, the tungsten wire coil was immersed in a toluene solution of polycarbosilane, an organic silicon polymer, and was heated to a specified temperature in the presence of N2 gas to convert the organic silicon polymer into Si3N4. The above process was repeated five times to form a ceramic film about 50 µm thick over the surface of the tungsten wire coil. This ceramics-coated tungsten wire coil was used to fabricate the ceramic heater in the same process as the first embodiment.
- In a further example, a slurry of only Si instead of a Si/Ti mixture was used for filling the interior of the end portions of the
enclosure 1 and, for the intermediate portion of theenclosure 1, the same SiC whisker slurry as in the first embodiment was used to manufacture the ceramic heater in the same process as the first embodiment. In this case, the porous ceramics that forms thefillers - A further example used a 80:20 Si/Si3N4 slurry instead of the Si/Ti slurry for filling the interior of the end portions of the
enclosure 1. The same process as the first embodiment was followed to fabricate the ceramic heater. In this case, the porous ceramics forming thefillers - Still another example used an Si slurry instead of the Si/Ti slurry for filling the interior of the end portions of the
enclosure 1. For filling the intermediate portion of theenclosure 1, an Si slurry was also used instead of SiC whisker slurry. A ceramic heater was fabricated in the same process as the first embodiment. In this case, the porous ceramics forming thefillers conductivity ceramic member 5 was an Si3N4 porous material. - The ceramic heater according to this invention can be fabricated in ways described in the above embodiments. Although there are slight variations in temperature vise time with respect to current supply time, almost similar effects can be produced.
- Next, by referring to Figure 2 through 5, another embodiment of the ceramic heater and its manufacturing method according to this invention will be described.
- The ceramic heater is used with a ceramics glow plug built into a diesel engine and is formed as a two-layer structure consisting of an inner shell and an
outer shell 21. The ceramics of the inner shell in which ametal coil 30 as a heater wire is embedded uses a ceramics that expands during baking. Theouter shell 21 is formed into a pipe-shaped shell made from a dense ceramics which containsfillers outer shell 21 is installed a low heatconductivity ceramics member 25. Themetal coil 30 is installed in thefillers conductivity ceramic member 25 inside theouter shell 21. - The
outer shell 21 is made from a dense ceramics such as silicon nitride Si3N4 and has one end thereof formed as aclosed end 35 and the other end as an open end. Further, theouter shell 21 is formed withfine holes 36 such as slits piercing through the wall and running in the longitudinal direction or holes piercing through the wall. Through these fine holes gases present in the interior of the outer shell are evacuated to create a vacuum inside during the manufacture process. With the fine holes 36 formed in theouter shell 21, it is possible to sinter the Si and Ti materials installed in theouter shell 21 while applying pressure three-dimensionally during gas-pressure baking. - The non-contracting ceramics that forms the
fillers outer shell 21 is made by baking the material containing Si and Ti and transforming them into a porous ceramics containing Si3N4, TiN, TiO2 and TiON. The volume of Si and Ti before backing is virtually equal to that of Si3N4, TiN, TiO2 and TiON combined after baking. In other words, the material of the fillers does not contract when subjected to baking. Hence, no gap is formed in the boundary between the inner wall surfaces 27, 34 of the dense Si3N4outer shell 21 and the outer surfaces of thefillers - Further, the low
heat conductivity ceramics 25 installed in the central portion inside theouter shell 21 is made from a ceramic powder, ceramic fibers or ceramic whiskers, all made of Si3N4 and metal nitride or oxide. That is, the lowheat conductivity ceramics 25 is made of such material as SiC whisker, Si3N4 whisker, Al2O3 whisker, Al2O3-SiO2 whisker, ceramic powder or Si3N4 porous material. It is desired from the standpoint of heat insulation that the ceramics around thecurrent control coil 29 be formed of a material with a low heat conductivity almost equal to that of air. - The
metal coil 30 is made of a high-melting point metal wire such as a tungsten wire, which is formed into a three-dimensional coil. A portion of the coil arranged in contact with theinner wall surface 27 of theouter shell 21 constitutes aheater coil 6 and a portion of the coil spaced from theinner wall surface 34 of theouter shell 21 constitutes thecurrent control coil 29. Further, themetal coil 30 has a connectingwire 31 that connects one end of theheater coil 26 and one end of thecurrent control coil 29; a connectingwire 32 that connects to the other end of theheater coil 26, extends along the inside of theouter shell 21 and projects from thefiller 23 of the non-contracting ceramics; and a connectingwire 33 that connects to the other end of thecurrent control coil 29, extends along the inside of theouter shell 21 and projects from thefiller 23 of the non-contracting ceramics. - This ceramic heater is assembled into a ceramic glow plug. One end of the
outer shell 1 is secured to a hollow body that has an electrode mounted in a hollow portion thereof through an insulator such as insulating bushing. The hollow body is made from a metal such as heat resistant alloy and has a thread for mounting to other component. The end of the connectingwire 33 is connected to the electrode and the end of the connectingwire 32 is connected to the hollow body. Therefore, in this ceramic heater, electric current flows from the electrode to the connectingwire 33 to thecurrent control coil 29 to the connectingwire 31 to theheater coil 26 to the connectingwire 32 to the hollow body. - Next, another embodiment of the ceramic heater manufacturing method is explained. First, an
outer shell 21 made of a dense ceramics is formed closed at oneend 35 and open at the other end and, as shown in Figure 3, is formed withfine holes 36, such as slits that pierce through the wall and extend in the longitudinal direction and holes that pierce through the wall. A three-dimensionallywound metal coil 30 is made from, say, a tungsten wire. Next, thetungsten wire coil 30 is installed inside theouter shell 21 in such a way that it contacts theinner wall surface 7 of one end portion of theouter shell 21 and is spaced from theinner wall surface 28 of the intermediate portion of the outer shell. A material containing Si and Ti is filled inside one end portion of theouter shell 21; a material containing a low heat conductivity ceramic member such as ceramic powder is filled inside the intermediate portion of theouter shell 21; and a material containing Si and Ti is filled inside the other end portion of theouter shell 21. Then, the outer shell filled with the Si/Ti material and the low heatconductivity ceramics member 25 is sintered in an N2 atmosphere at a gas pressure of less than 9.9 kgf/cm2 to convert the Si/Ti material into a porous ceramics containing Si3N4, TiN, TiO2 and TiON, i.e., into a non-contracting ceramics, to form thefillers outer shell 21. - The ceramics heater is then placed in a vacuum and, as shown in Figure 4, the fine holes 36 formed in the wall of the
outer shell 21 are sealed with a sealingfilm 24 such as glass and brazing filler metal to hermetically enclose the interior of theouter shell 21, thus forming the ceramic heater. Hence, compared with the conventional ceramic heaters, the ceramic heater of this invention that is incorporated into the ceramics glow plug can be manufactured easily at reduced cost and has higher reliability and stable characteristics. - In this ceramic heater, the
heater coil 26 which constitutes a heater portion is in contact with theinner wall surface 27 of theouter shell 21 and is embedded in the non-contractingceramic filler 22 that contacts theinner wall surface 27 of theouter shell 21. This construction allows the entireouter shell 21 to be heated uniformly and assures a very good heat conductivity of the heater portion, offering an improved heating performance that allows the heater portion to be heated quickly upon energization. Figure 5 shows a graph illustrating the relation between the temperature (°C) of the heater portion and the energizing time (second). In the graph, the ceramic heater of this invention is represented by a broken line and the conventional glow plug by a solid line. Figure 5 shows that the heater of this invention can be heated to a specified temperature in a shorter energizing time than is required with the conventional heater, demonstrating the superior heating characteristic.
Claims (16)
- A ceramic heater that includes:fillers (2, 3, 5, 22, 23, 25) disposed inside an enclosure (1, 21);a heater coil (6, 26) disposed inside a front end portion of the enclosure where one of the fillers is located; anda current control coil (9, 29) arranged inside a central portion of the enclosure;that the enclosure is made from a dense ceramics;that the fillers consist of porous ceramics (2, 3, 22, 23) contained in end portions of the enclosure and a low heat conductivity ceramics (5, 25) contained in a central portion of the enclosure;that the heater coil and the current control coil are formed of one and the same metal coil (10, 30);that the heater coil (6, 26) is arranged in contact with an inner wall surface of that portion of the enclosure where the fillers (2, 22) are contained; andthat the current control coil (9, 29) is spaced from an inner wall surface of that portion of the enclosure where the low heat conductivity ceramics (5, 25) is contained, so that the current control coil is heat-insulated.
- A ceramic heater according to claim 1, wherein the enclosure is formed of an Si3N4 ceramics, the fillers (2, 3, 22, 23) are porous ceramics containing Si and Ti, and the inner wall surface of the enclosure (1, 21) and the outer circumferential surfaces of the fillers (2, 3, 22, 23) closely adhere to each other with no gap therebetween.
- A ceramic heater according to claim 2, wherein an N2 gas is sealed in the central portion of the enclosure (1, 21) where the low heat conductivity ceramics (5, 25) is contained.
- A ceramic heater according to any one of claim 1 to 3, wherein the enclosure (1) is open at both ends, which are closed by sealing films (4) to seal the interior of the enclosure.
- A ceramic heater according to claim 4, wherein the sealing films (4) are formed of glass or the same kind of ceramics as that of the enclosure.
- A ceramic heater according to any one of claim 1 to 3, wherein the enclosure (21) is formed of a dense ceramics and is closed at one end and open at the other end, and the porous ceramics contained in the end portions of the enclosure (21) are a non-contracting ceramics.
- A ceramic heater according to any one of claim 1 to 6, wherein the metal coil is made from a tungsten wire.
- A ceramic heater according to any one of claim 1 to 7, wherein a surface of the metal coil is coated with a ceramic film deposited by the chemical vapor deposition or with an organic silicon polymer-converted ceramic film.
- A ceramic heater according to any one of claim 1 to 8, wherein the porous ceramics are a non-contracting ceramics made by sintering Si and Ti for reaction and the non-contracting ceramics contains Si3N4, TiN, TiO2 and TiON.
- A ceramic heater according to any one of claim 1 to 9, wherein the low heat conductivity ceramics (5, 25) is made from ceramic whiskers and/or ceramic powder.
- A ceramic heater according to any one of claim 1 to 10, wherein the low heat conductivity ceramics (5, 25) is made from Si3N4 and a metal nitride or a metal oxide.
- A method of manufacturing a ceramic heater including the steps of:making an enclosure (1, 21) and a metal coil (10, 30);installing the metal coil (10, 30) inside the enclosure; andfilling fillers inside the enclosure (1, 21);making the enclosure from a dense ceramics;making the metal coil (10, 30) from a high-melting point metal wire;installing the metal coil inside the enclosure in such a way that the metal coil is in contact with an inner wall surface of one end portion of the enclosure and is spaced from an inner wall surface of an intermediate portion of the enclosure;filling a material containing Si and Ti inside the one end portion of the enclosure; filling a low heat conductivity ceramics (5, 25) inside the intermediate portion of the enclosure and filling a material containing Si and Ti inside the other end portion of the enclosure;baking the enclosure together with the filling materials and the metal coil for reaction in an N2 atmosphere to convert the Si/Ti material into a porous ceramics containing Si3N4 and TiN; andmaking the porous ceramics adhere to the dense ceramics of the enclosure.
- A ceramic heater manufacturing method according to claim 12, wherein after the material containing Si and Ti is sintered for reaction, the end surfaces of the enclosure (1) are coated with sealing films (4) to seal the interior of the enclosure.
- A ceramic heater manufacturing method according to claim 12 or 13, wherein before the metal coil is installed inside the enclosure, the surface of the metal coil is coated with a ceramics having almost the same thermal expansion coefficient as the metal coil.
- A ceramic heater manufacturing method according to any one of claim 12 to 14, wherein the enclosure (21) is made of a dense ceramics, is closed at one end and open at the other end, and is formed with fine holes (36) passing through the wall thereof; wherein after the material containing Si and Ti is filled inside the enclosure (21) and is sintered for reaction and converted into a porous ceramics, i.e., a non-contracting ceramics, the fine holes (36) in the enclosure (21) are hermetically closed in a vacuum by the sealing films (24) and also the sealing films (24) that seals the one end surface of the enclosure (21).
- A ceramic heater manufacturing method according to claim 15, wherein the porous ceramics is a non-contracting ceramics containing Si3N4, TiN, TiO2 and TiON, the non-contracting ceramics adheres to the Si3N4 dense ceramics of the enclosure (21), and the fine holes (36) formed in the enclosure (21) are hermetically closed by the sealing films (24) made of Si3N4 in a vacuum.
Applications Claiming Priority (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP05284204A JP3075660B2 (en) | 1993-10-20 | 1993-10-20 | Ceramic heater and method of manufacturing the same |
JP284204/93 | 1993-10-20 | ||
JP5284203A JP3050266B2 (en) | 1993-10-20 | 1993-10-20 | Ceramic heating element and method of manufacturing the same |
JP284203/93 | 1993-10-20 |
Publications (3)
Publication Number | Publication Date |
---|---|
EP0650020A2 EP0650020A2 (en) | 1995-04-26 |
EP0650020A3 EP0650020A3 (en) | 1996-06-05 |
EP0650020B1 true EP0650020B1 (en) | 1999-04-07 |
Family
ID=26555368
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP19940307544 Expired - Lifetime EP0650020B1 (en) | 1993-10-20 | 1994-10-14 | A ceramic heater and a method of manufacture thereof |
Country Status (2)
Country | Link |
---|---|
EP (1) | EP0650020B1 (en) |
DE (2) | DE650020T1 (en) |
Families Citing this family (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH10169982A (en) * | 1996-12-11 | 1998-06-26 | Isuzu Ceramics Kenkyusho:Kk | Ceramic heater and its manufacture |
DE102004045815A1 (en) * | 2004-09-22 | 2006-03-23 | Robert Bosch Gmbh | Process for embedding a metallic wire in a ceramic element |
CN101953226B (en) | 2008-01-29 | 2014-01-01 | 株式会社东热 | Dip-type heater |
EP3163171B1 (en) * | 2015-10-30 | 2018-12-12 | NGK Spark Plug Co., Ltd. | Glow plug |
DE102016105069A1 (en) | 2016-03-18 | 2017-09-21 | Eberhard Karls Universität Tübingen Medizinische Fakultät | Antiviral immunotherapy by membrane receptor ligation |
Family Cites Families (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS5872821A (en) * | 1981-10-26 | 1983-04-30 | Ngk Spark Plug Co Ltd | Glow plug and its manufacturing method |
JP2720033B2 (en) * | 1987-10-28 | 1998-02-25 | 京セラ株式会社 | Self-control ceramic glow plug |
US5084606A (en) * | 1990-05-17 | 1992-01-28 | Caterpillar Inc. | Encapsulated heating filament for glow plug |
JPH1114622A (en) * | 1997-06-20 | 1999-01-22 | Matsushita Electric Ind Co Ltd | Excrement inspection device |
-
1994
- 1994-10-14 EP EP19940307544 patent/EP0650020B1/en not_active Expired - Lifetime
- 1994-10-14 DE DE1994307544 patent/DE650020T1/en active Pending
- 1994-10-14 DE DE1994617676 patent/DE69417676T2/en not_active Expired - Fee Related
Also Published As
Publication number | Publication date |
---|---|
EP0650020A3 (en) | 1996-06-05 |
DE650020T1 (en) | 1996-05-02 |
DE69417676D1 (en) | 1999-05-12 |
EP0650020A2 (en) | 1995-04-26 |
DE69417676T2 (en) | 1999-09-30 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US6130410A (en) | Ceramic heater and process for producing the same | |
US6881930B2 (en) | Glow plug and method of manufacturing the same | |
US4555358A (en) | Electrically conductive sintered ceramics and ceramic heaters | |
EP0771773B1 (en) | Ceramic sheath type part and method of manufacturing the same | |
US4874923A (en) | Glow plug for diesel engine with a U-shaped sialon ceramic heater | |
US4633064A (en) | Sintered ceramic electric heater with improved thermal shock resistance | |
US4931619A (en) | Glow plug for diesel engines | |
JP3658770B2 (en) | Ceramic glow plug | |
US4810853A (en) | Glow plug for diesel engines | |
US6040519A (en) | Unit sheath | |
EP0650020B1 (en) | A ceramic heater and a method of manufacture thereof | |
JP2010506754A (en) | Electric heating device for hot runner system | |
EP0648978A2 (en) | Ceramic glow plug | |
JP3050266B2 (en) | Ceramic heating element and method of manufacturing the same | |
JP5038575B2 (en) | Glow plug | |
JPH07119969A (en) | Ceramic heater and its manufacturing method | |
JP3050262B2 (en) | Ceramic glow plug | |
JPH07217886A (en) | Self-controlled type ceramic glow plug | |
JPH02183718A (en) | Glow plug | |
JP3075651B2 (en) | Ceramic glow plug | |
JPH01121626A (en) | Glow plug for diesel engine | |
JPS63285891A (en) | Silicon carbide heating body | |
JPS60217A (en) | Ceramic glow plug | |
JPH09196375A (en) | Ceramic heater | |
JPH07139737A (en) | Ceramic heater |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
PUAI | Public reference made under article 153(3) epc to a published international application that has entered the european phase |
Free format text: ORIGINAL CODE: 0009012 |
|
AK | Designated contracting states |
Kind code of ref document: A2 Designated state(s): DE FR GB |
|
EL | Fr: translation of claims filed | ||
PUAL | Search report despatched |
Free format text: ORIGINAL CODE: 0009013 |
|
DET | De: translation of patent claims | ||
AK | Designated contracting states |
Kind code of ref document: A3 Designated state(s): DE FR GB |
|
17P | Request for examination filed |
Effective date: 19961119 |
|
GRAG | Despatch of communication of intention to grant |
Free format text: ORIGINAL CODE: EPIDOS AGRA |
|
17Q | First examination report despatched |
Effective date: 19980803 |
|
GRAG | Despatch of communication of intention to grant |
Free format text: ORIGINAL CODE: EPIDOS AGRA |
|
GRAH | Despatch of communication of intention to grant a patent |
Free format text: ORIGINAL CODE: EPIDOS IGRA |
|
GRAH | Despatch of communication of intention to grant a patent |
Free format text: ORIGINAL CODE: EPIDOS IGRA |
|
GRAA | (expected) grant |
Free format text: ORIGINAL CODE: 0009210 |
|
AK | Designated contracting states |
Kind code of ref document: B1 Designated state(s): DE FR GB |
|
ET | Fr: translation filed | ||
REF | Corresponds to: |
Ref document number: 69417676 Country of ref document: DE Date of ref document: 19990512 |
|
PGFP | Annual fee paid to national office [announced via postgrant information from national office to epo] |
Ref country code: FR Payment date: 19990923 Year of fee payment: 6 |
|
PGFP | Annual fee paid to national office [announced via postgrant information from national office to epo] |
Ref country code: GB Payment date: 19991012 Year of fee payment: 6 |
|
PGFP | Annual fee paid to national office [announced via postgrant information from national office to epo] |
Ref country code: DE Payment date: 19991127 Year of fee payment: 6 |
|
PLBE | No opposition filed within time limit |
Free format text: ORIGINAL CODE: 0009261 |
|
STAA | Information on the status of an ep patent application or granted ep patent |
Free format text: STATUS: NO OPPOSITION FILED WITHIN TIME LIMIT |
|
26N | No opposition filed | ||
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: GB Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 20001014 |
|
GBPC | Gb: european patent ceased through non-payment of renewal fee |
Effective date: 20001014 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: FR Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 20010629 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: DE Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 20010703 |
|
REG | Reference to a national code |
Ref country code: FR Ref legal event code: ST |