EP0648978A2 - Keramische Glühkerze - Google Patents

Keramische Glühkerze Download PDF

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Publication number
EP0648978A2
EP0648978A2 EP94307223A EP94307223A EP0648978A2 EP 0648978 A2 EP0648978 A2 EP 0648978A2 EP 94307223 A EP94307223 A EP 94307223A EP 94307223 A EP94307223 A EP 94307223A EP 0648978 A2 EP0648978 A2 EP 0648978A2
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EP
European Patent Office
Prior art keywords
ceramic
pipe
coil
glow plug
coil portion
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.)
Granted
Application number
EP94307223A
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English (en)
French (fr)
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EP0648978A3 (de
EP0648978B1 (de
Inventor
Hideo Kawamura
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Isuzu Ceramics Research Institute Co Ltd
Original Assignee
Isuzu Ceramics Research Institute Co Ltd
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Priority claimed from JP5269432A external-priority patent/JP3050264B2/ja
Priority claimed from JP26943193A external-priority patent/JPH07103480A/ja
Application filed by Isuzu Ceramics Research Institute Co Ltd filed Critical Isuzu Ceramics Research Institute Co Ltd
Publication of EP0648978A2 publication Critical patent/EP0648978A2/de
Publication of EP0648978A3 publication Critical patent/EP0648978A3/de
Application granted granted Critical
Publication of EP0648978B1 publication Critical patent/EP0648978B1/de
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23Q—IGNITION; EXTINGUISHING-DEVICES
    • F23Q7/00—Incandescent ignition; Igniters using electrically-produced heat, e.g. lighters for cigarettes; Electrically-heated glowing plugs
    • F23Q7/001—Glowing plugs for internal-combustion engines

Definitions

  • the present invention relates to a ceramic glow plug used with diesel engines.
  • a glow plug conventionally used in diesel engines consists of a tungsten (W) wire embedded in a ceramics such as silicon nitride.
  • a tungsten (W) wire for example, has a resistance of 0.1 ⁇ at room temperature and a current of 120 A for a 12 V power supply.
  • the resistance of the tungsten wire is 0.4 ⁇ and its current is 30 A. Then as the glow plug is further heated, the resistance increases until it stabilizes at 1 ⁇ , at which time the current is 12 A.
  • the current value decreases from the initial value of 120 A with an increasing resistance, which increases with the temperature of a heater coil, until the current stabilizes when the resistance becomes 1 ⁇ .
  • the current is controlled by the controller so that the resistance of the heater coil of the glow plug is stabilized and held at 1 ⁇ .
  • the self-control type glow plug consists of a tungsten coil and a nickel coil connected in series, with the tungsten coil embedded in a ceramics such as Si3N4. That is, in the self-control type glow plug, a conductor with a small resistance is arranged in a heating body of the heater coil and is connected to the nickel coil with a large resistance installed on the upstream side of the conductor. When a current flows, the nickel coil of the self-control type glow plug is heated increasing the resistance, which in turn reduces the current thus controlling the amount of heat generated by the heating body of the heater coil.
  • the conventional self-control type glow plugs include those disclosed in Japanese Patent Publication Nos. 34052/1992 and 19404/1985, and Japanese Patent Laid-Open Nos. 157423/1984 and 106326/1983.
  • the self-control type glow plug disclosed in the 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 the 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.
  • ⁇ TX ⁇ TO [1+ ⁇ ( T X - T O )]
  • ⁇ TX is a resistance of the heater coil at a certain temperature T X
  • ⁇ TO is a resistance of the heater coil at room temperature T O
  • ⁇ is a resistance-temperature coefficient
  • the glow plug passes a saturation current at about 1 ⁇ for a 12 V supply voltage and is maintained at about 900°C.
  • a resistance of approximately 0.1 ⁇ is required at room temperature.
  • the tungsten wire used as a heating coil has a resistance-temperature coefficient of the order of 4 ⁇ 10 ⁇ 9, and thus it is not possible to saturate the current at 900°C.
  • a primary aim of this invention is to solve or at least partially alleviate the above-mentioned problems.
  • the present invention provides a ceramic glow plug which includes: a hollow body having a conductor, including an electrode, disposed in a hollow portion thereof; a ceramic pipe secured to and projecting from the hollow body to form a heater portion, the pipe being closed at a front end portion thereof; a first coil portion installed in the ceramic pipe; a second coil portion connected in series with the first coil portion and disposed in the ceramic pipe; and ceramic fillers sealing the ends of the ceramic pipe; said ceramics glow plug being characterized in: that the first coil portion is arranged in contact with an inner wall surface of the pipe; that the second coil portion is spaced from an inner wall of the pipe; and that when the first and second coil portions are supplied with electricity, the first coil portion constitutes a heater coil and the second coil portion constitutes a current control coil.
  • the present invention provides a ceramic glow plug of current self-control type, which comprises: a current control portion formed of a coiled tungsten wire installed in an area with high heat-insulation so that the amount of heat dissipated from the current control portion is small and a heater portion formed in an area with low heat-insulation so that the amount of heat dissipated from the heater portion is large, thereby forming a current self-control type glow plug that adjusts a current flowing through the heater portion and the current control portion to produce an optimum amount of heat; and more specifically and preferably comprises a tungsten wire installed in a hollow portion of the ceramic pipe and a conductive printed layer.
  • the inner diameter of a central portion of the ceramics pipe is made larger than the inner diameter of the front end portion, a tungsten wire having a coil outer diameter equal to the inner diameter of the front end portion of the pipe is installed in the pipe, and the front end portion of the pipe is made to serve as the heater portion and the central portion of the pipe is made to serve as the current control portion.
  • the ceramic glow plug with this configuration has high reliability and can reduce manufacturing cost and secure stable strength.
  • the present invention also provides a ceramic glow plug, which includes: a hollow body having a conductor, including an electrode, disposed in a hollow portion thereof; a ceramic pipe secured to and projecting from the hollow body to form a heater portion, the pipe being closed at the front end portion thereof; a conductive printed layer containing a tungsten powder and formed over the outer surface of the pipe and of the front end portion of the pipe; ceramic fillers sealing the ends of the pipe; a coiled tungsten wire having one end thereof connected to the conductive printed layer and the other end passing through the ceramic filler and connected to the electrode, the coiled tungsten wire also having a current control portion exposed in a hollow portion of the pipe; and a ceramic outer surface coating layer covering the conductive printed layer on the outer surface of the pipe.
  • the tungsten wire When a current is passed through the tungsten wire and the conductive printed layer, the tungsten wire becomes extremely hot compared with the conductive printed layer because the tungsten wire located in the hollow portion of the pipe is highly thermally insulated and the conductive printed layer is exposed to outside through the ceramic outer surface coating layer.
  • this ceramics glow plug as the tungsten wire is heated to high temperatures, its resistance increases reducing the current flowing through the tungsten.
  • the tungsten wire functions as a temperature control wire, self-controlling the amount of heat dissipated from the ceramic outer surface coating layer to an optimum value.
  • the outer surface of the pipe is formed with the conductive printed layer printed film.
  • this layer is heated causing the entire pipe to rise in temperature uniformly.
  • the end of the tungsten wire fitted into the through-hole of the pipe is firmly held connected to the conductive printed layer by the presence of a paste. In this condition, when the ceramic pipe and its associated components are sintered, the conductive printed layer and the tungsten wire are joined firmly with good electric conductivity at the connection.
  • the conductive printed layer is printed spirally or wholly over the outer surface of the pipe. If a Ni or Mo powder is added to the tungsten powder contained in the paste, the tungsten wire and the conductive printed layer, after being burned, are joined together more firmly because Ni and Mo has good reactivity.
  • the conductive printed layer may also contain a si3N4 powder in addition to the Ni or Mo powder.
  • this ceramic glow plug Another characteristic of this ceramic glow plug is that because a ceramic formed body that constitutes the pipe is sintered with one end of the tungsten wire installed in the ceramic formed body, with the paste containing the tungsten powder printed over the outer surface of the ceramic formed body, and with the ceramic slurry forming the ceramic fillers filled in one end portion of the ceramic formed body, the pipe, the tungsten wire, the conductive printed layer and the ceramic fillers are joined together in good condition.
  • a liquid polymer precursor that forms the ceramic outer surface coating layer may be applied over the outer circumferential surface of the ceramic formed body that constitutes the pipe and of the paste containing a tungsten powder that forms the conductive printed layer, and these components are sintered simultaneously, so that the conductive printed layer and the tungsten wire are firmly joined to the pipe and that the ceramic outer surface coating layer is joined to the pipe and the conductive printed layer. In this way, the stable construction of this ceramic glow plug can be obtained easily and reliably.
  • the tungsten wire has its coiled current control portion installed in the hollow portion formed at the intermediate part of the pipe, with only the ends of the wire connected to the ceramic filler and the conductive printed layer. This arrangement allows the current control portion of the tungsten wire to be easily heated to high temperatures by the conducting current, making the self-control more responsive and the current control easier.
  • the ceramic outer surface coating layer which is formed of silicon nitride excellent in heat resistance
  • the ceramic outer surface coating layer serves as a protective layer for the pipe, improving heat resistance and thermal shock resistance as well as high-temperature strength.
  • this ceramics glow plug is that the paste of tungsten powder is printed spirally over the outer surface of the silicon nitride formed body, that the tungsten wire is attached to the formed body, and that the slurry of silicon nitride is applied over the outside of the printed paste of tungsten powder.
  • This arrangement allows a heater coil to be easily formed over the outer circumferential surface of the pipe and also makes burning easy and assures reliable electric connections.
  • the paste of tungsten powder may be printed over the entire outer surface of the formed body.
  • the ceramics used to form the pipe and the ceramic fillers may use silicon nitride to improve heat resistance, high-temperature strength and durability.
  • the conductive printed layer may contain a Si3N4 powder so as to reinforce the strength of joint between the conductive printed layer and the ceramic outer surface coating layer.
  • the present invention also provides a ceramics glow plug, which includes: a hollow body having a conductor, including an electrode, projecting in a hollow portion thereof; a ceramics pipe secured to and protruding from the hollow body and forming a heater portion; a first hole portion with a small inner diameter, formed in a part of the pipe corresponding to the heater portion; a second hole portion with a large inner diameter, formed in another portion of the pipe on the electrode side; a coiled tungsten wire having a first coil portion that contacts the inner wall surface of the first hole portion and a second coil portion that does not contact the inner wall surface of the second hole portion, the tungsten wire having one end thereof connected to the electrode and the other end connected to the hollow body; a first ceramic filler filled in the first hole portion where the first coil portion is located to embed the first coil portion; and a second ceramics filler filled in an end of the second hole portion on the electrode side so as to leave hollow an area where the second coil portion is located.
  • first coil portion and the second coil portion are formed of a single continuous tungsten wire, simply arranging the tungsten wire in the center of the ceramic pipe and supplying an electric current to the coiled tungsten wire allow the first coil portion to serve as a heater portion and the second coil portion to serve as a current control portion.
  • the heat generated by the first coil portion heats the pipe and is dissipated to the outside but the heat generated by the second coil portion is insulated raising the temperature of the second coil portion.
  • the second coil portion suppresses current flow and thus works as a current control portion. That is, when the second coil portion is heated to high temperature, its resistance increases limiting the current flowing through the tungsten wire, thus self-controlling the amount of heat generated by the ceramic pipe to an optimum value.
  • the hollow portion of the pipe is sealed with N2 gas and SiC fiber, there is no need to take measures to prevent oxidation of the tungsten wire, such as coating the wire with SiC, thus simplifying the manufacture process, which in turn will lead to a reduction in the manufacturing cost.
  • This arrangement eliminates the possibility of the tungsten wire being broken from oxidation and improves durability of the wire.
  • the ceramics forming the first ceramic filler and the second ceramic filler should preferably use Si3N4. Because the ceramics forming the first and second ceramics fillers is Si3N4 containing TiO2, a good heat conductivity is maintained.
  • the first coil portion which forms the heater portion, is installed in the center of the pipe, the temperature of the whole pipe rises uniformly. Because the first coil portion is placed in contact with the inner wall surface of the pipe and the ceramic filler is filled with the first coil portion buried, the heat conductivity of the heater portion is extremely good.
  • first coil portion and the second coil portion have the same wire form and the same coil outer diameter and are formed of the single continuous tungsten wire, and that the ceramic pipe is formed with the small-diameter first hole portion and the large-diameter second hole portion. Because of this arrangement, simply placing the tungsten wire in the ceramics pipe allows the tungsten wire to be positioned at the center of the pipe, with the first coil portion working as the heater portion and the second coil portion working as the current control portion. It is therefore possible to provide an improved heat generating efficiency and to heat the heater portion uniformly. Furthermore, because the pitch of the first coil portion is smaller than that of the second coil portion, ideal heater portion and current control portion can be obtained.
  • Such a tungsten wire can be manufactured by using a ceramic coil making jig which has a through-hole in the center and spiral grooves on the outer circumferential surface thereof. Because there are no connections in the wire, the tungsten wire has high electrical reliability and durability and can be fabricated at low cost.
  • the ceramic glow plug consists mainly of a hollow body 1 having a terminal or electrode 10 mounted in a hollow portion 22 through an insulator 18 such as an insulating bushing, a ceramics pipe 2, a tungsten wire 3, a ceramic filler 4 filled in one end of the pipe 2, a ceramic outer surface coating layer 5 which is a protective member arranged on the outer surface of the pipe 2, and a conductive printed layer 8 joined to the outer surface of the pipe 2.
  • the hollow body 1 is made from a metal such as a heat resisting alloy and is formed with a thread 19 for mounting to other component.
  • the electrode 10 is formed with a positioning and fixing screw 21, over which a nut 20 is fitted to position and fix the electrode 10 with respect to the hollow body 1.
  • the ceramics pipe 2 has one part thereof secured to the inner wall surface 17 of the hollow body 1 through the conductive printed layer 8.
  • the ceramics pipe 2 can be joined to the hollow body 1 by metalizing the outer circumferential surface 13 of the ceramic pipe 2 before jointing. This results in a very firm electrical connection between the conductive printed layer 8 and the hollow body 1.
  • a heater portion 12 of the ceramic pipe 2 protrudes from the end 15 of the hollow body 1.
  • the tungsten wire 3 has one end 16 connected to the electrode 10 through a power supply connecting portion 11 and the other end 7 inserted into a through-hole 23 formed in a closed front end portion 14 of the ceramic pipe 2 and electrically connected to the conductive printed layer 8.
  • a conductor having the electrode 10 is projected into the hollow portion 22 of the hollow body 1, and the ceramic pipe 2 making up the heater portion 12 is fixed to and projected from the body 1.
  • An outer surface 24 of the ceramic pipe 2 is joined with the conductive printed layer 8 containing tungsten powder.
  • the end of the pipe 2 on the electrode side is filled with the ceramic filler 4, and at an intermediate portion of the pipe 2 is formed a hollow portion 9.
  • the coiled tungsten wire 3 has its end 7 attached to the conductive printed layer 8 and its other end 16 connected to the electrode 10, and has a coiled current control portion 6 exposed in the hollow portion 9 of the pipe 2 which constitutes a temperature control wire.
  • the ceramic outer surface coating layer 5 is applied over the outer circumferential surface of the pipe 2 and the conductive printed layer 8 formed on the outside of the pipe 2.
  • the ceramic outer surface coating layer 5 forms a protective layer for the heater portion 12.
  • the conductive printed layer 8 as shown in Figure 2, is formed as a spiral body 25 over the portion of the pipe 2 that forms the heater portion 12 and is also formed continuously over the entire surface of that portion of the pipe 2 that is connected to the body 1.
  • the ceramic powder forming the conductive printed layer 8 includes nickel and molybdenum powder in addition to tungsten powder. Nickel and molybdenum have good reactivity, so that the tungsten wire 3 and the conductive printed layer 8 are sintered together offering firm, good electrical connection.
  • the ceramics forming the pipe 2, ceramic filler 4 and the ceramic outer surface coating layer 5 employs silicon nitride Si3N4 excellent in heat resistance and high-temperature strength.
  • the tungsten wire 3 extends longitudinally uncontacted in the hollow portion 9 of the ceramic pipe 2.
  • the hollow portion 9 is sealed with N2 gas and SiC fiber for the prevention of oxidation of the tungsten wire 3.
  • the tungsten wire 3 may be coated with SiC or WC to prevent its oxidation for improved corrosion resistance and durability.
  • the ceramic layer forms a protective pipe, improving thermal shock and heat resistance and high-temperature strength.
  • the conductive printed layer 8 that extends spirally over the heater portion 12 to form a number of spiral grooves 26. With this arrangement, the ceramic outer surface coating layer 5 on the outer side of the conductive printed layer 8 bites into the grooves 26, reinforcing the joint between the ceramic pipe 2 and the ceramic outer surface coating layer 5.
  • the ceramic glow plug is manufactured in the following way.
  • the hollow body 1 is made from a metal such as a heat resisting alloy and is formed with a thread 19 for mounting to other component.
  • the terminal or electrode 10 is formed with a thread 21 for positioning and fixing with respect to the hollow body 1.
  • the electrode 10 is mounted to the hollow body 1 through the insulator 18 so that it rests in the hollow portion 22.
  • the nut 20 is screwed over the thread 21 to position and fix the electrode 10 with respect to the hollow body 1.
  • one end of the tungsten wire 3 is formed into a straight end 7 and the other end into a straight end 16, with the central portion formed as the coiled current control portion 6.
  • a cylindrical body with one end closed and the other end open is formed of a slurry of silicon nitride.
  • a paste containing a tungsten powder or, if necessary, a mixture of tungsten powder and Ti or Mo powder is printed on the outer circumferential surface of the cylindrical body and in the through-hole formed in its closed end. That is, the inner wall surface of the through-hole 23 formed in the front end portion of the cylindrical body and the outer circumferential surface of that portion of the pipe 2 that is inserted into the body 1 are wholly printed with the paste.
  • the paste is printed either spirally or wholly. Then, the end 7 of the tungsten wire 3 is inserted into the through-hole 23 at the front end of the cylindrical body and the other straight end 16 is held projected from the cylindrical body.
  • a ceramic slurry that forms the ceramic filler 4 is filled into the open end of the cylindrical body so that the end 16 of the tungsten wire 3 projects from the filled end.
  • a liquid material such as polymer precursor that forms the ceramic outer surface coating layer 5 is applied to the outer circumferential surface of the cylindrical body and the paste.
  • the tungsten wire 3 is fitted to the cylindrical body, the paste is printed on the outer surface of the cylindrical body, a ceramic slurry is filled into one end of the cylindrical body, and the ceramic slurry is applied to the outer circumferential surface of the cylindrical body.
  • a cylindrical body assembly is obtained.
  • the cylindrical body assembly thus formed is placed in a sintering furnace for sintering to produce a sintered body that forms the heater portion 12.
  • the end 16 of the tungsten 3 protruding from the end of the sintered body is connected to the power supply connecting portion 11 of the electrode 10.
  • the outer circumferential surface 13 of the end portion of the metalized sintered body is fitted into the hollow body 1 for jointing. In this way, the ceramic glow plug is completed.
  • the components of the cylindrical body assembly - including the tungsten wire 3 whose one end is fitted in the ceramic cylindrical body, the conductive paste applied to the cylindrical body, a ceramics slurry filled into one end of the cylindrical body and the ceramics slurry applied over the outer circumferential surface of the cylindrical body - are all burned at the same time, the conductive printed layer 8 is firmly and reliably joined to the pipe 2 and the tungsten wire 3, forming a good electrical connection. Furthermore, the ceramic outer surface coating layer 5 is also securely and reliably joined to the pipe 2.
  • the ceramic glow plug with the above construction works as follows.
  • a current is supplied from the electrode 10 to the tungsten wire 3, the conductive printed layer 8 and the body 1, the pipe 2 is heated by the heat of the conductive printed layer 8 because the conductive printed layer 8 is in contact with the pipe 2 and because the coiled current control portion 6 of the tungsten wire 3 is exposed in the hollow portion, which is defined by the closed end of the pipe 2 and the other end of the pipe 2 sealed by the ceramic filler 4.
  • the heat generated by the conductive printed layer 8 is dissipated through the ceramics outer surface coating layer 5. But the heat generated by the coiled current control portion 6 of the tungsten wire 3 is not dissipated and thus the coil 6 becomes extremely hot compared with the conductive printed layer 8.
  • the coiled current control portion 6 As the coiled current control portion 6 is heated to high temperature, its resistance increases suppressing the flow of current through the tungsten wire 3, thereby self-controlling the amount of heat generated by the heater portion 12.
  • the current flowing through the tungsten wire 3 increases heating the heater portion 12 by the conductive printed layer 8, thus keeping the amount of heat produced by the heater portion 12 at an optimum value.
  • the pipe 2 with the embedded conductive printed layer 8 since the pipe 2 with the embedded conductive printed layer 8 is exposed outside the combustion chamber, the pipe dissipates heat, maintaining the temperature of the heater portion 12 at 900°C, for example, which in turn sets the resistance of the conductive printed layer 8 to 0.4 ⁇ . Because the tungsten wire 3 is disposed in the sealed hollow portion 9 and thermally insulated, the temperature of the tungsten wire reaches 1800°C and its resistance becomes 0.6 ⁇ . Hence, in this ceramic glow plug, the total resistance of the tungsten wire 3 and the conductive printed layer 8 is 1 ⁇ , which stabilizes the current flow.
  • the ceramic glow plug of the second embodiment consists of a hollow body 31 having a terminal or electrode 40 mounted in a hollow portion 52 through an insulator 48 such as an insulating bushing, a ceramic pipe 32, a tungsten wire 33, and ceramic fillers 34, 44 filled in the ends of the pipe 32.
  • the hollow body 31 is made from a metal such as a heat resisting alloy and is formed with a thread 49 for mounting to other component.
  • the terminal or electrode 40 is fitted with a nut 50 for its positioning and fixing with respect to the hollow body 31.
  • the ceramic pipe 32 can be mounted to the hollow body 31 by metalizing an outer circumferential surface 47 of the ceramics pipe 32 and fitting it into an inner circumferential surface 54 of the hollow body 31.
  • a heater portion 42 of the ceramic pipe 32 protrudes from the end portion 45 of the hollow body 31.
  • the tungsten wire 33 has its one end 46 connected to the electrode 40 through a power supply connecting portion 41 and the other end 43 joined to the inner surface of the hollow body 31 for electrical connection.
  • the hollow body 31 has a conductor - including the electrode 40 - protruding into the hollow portion 52.
  • the ceramic pipe 32 forming the heater portion 42 projects from and is fixed to the hollow body 31.
  • the ends of the pipe 32 is sealed with the ceramic fillers 34, 44, forming a hollow portion 35 in an intermediate portion of the pipe 32.
  • the hollow portion 35 of the pipe 32 is sealed with N2 gas and SiC fiber for the prevention of oxidation of tungsten wire 33.
  • the ceramic pipe 32 is formed with a small-diameter first hole portion 38 at a location corresponding to the heater portion 42 and with a large-diameter second hole portion 39 on the electrode side.
  • the tungsten wire 33 is formed of a single wire and consists of a first coil portion 36 that contacts the inner wall surface of the first hole portion 38 and a second coil portion 37 that does not contact the inner wall surface of the second hole portion 39.
  • One end 46 of the tungsten wire 33 is connected to the electrode 40 while the other end 43 is connected to the hollow body 31.
  • the ceramic filler 34 is filled in the first hole portion 38 embedding the first coil portion 36, and the ceramic filler 44 is filled in the end part of the second hole portion 39 of the pipe 32 on the electrode side so as to leave the area where the second coil portion 37 is located hollow 35.
  • the end 46 of the tungsten wire 33 is fitted into a hole 55 formed in the end portion 41 of the electrode 40 and is metalized to provide a good electrical connection with the electrode 40.
  • the other end 43 of the tungsten wire 33 is fitted in a groove 51 formed at the end of the pipe 32 and is metalized for good electrical connection with the hollow body 31.
  • the first coil portion 36 and the second coil portion 37 of the tungsten wire 33 have the same wire shape and the same coil outer diameter and are made from a single continuous tungsten wire. Further, the first coil portion 36 has a pitch smaller than that of the second coil portion 37. Thus, the tungsten wire 33 can be manufactured very easily and accurately.
  • the first coil portion 36 is capable of generating enough heat to heat the heater portion 42 to elevated temperatures in short time and the second coil portion 37 is suited to controlling current.
  • the pipe 32 is preferably made from ceramics Si3N4 with good heat resistance and high strength.
  • the ceramic fillers 34, 44 are formed of Si3N4 having good heat resistance and high-temperature strength and preferably made of Si3N4 containing TiO2 because it improves heat conductivity.
  • the tungsten wire 33 needs to be covered with SiC or WC to guard against oxidation. This coating can prevent oxidation of the tungsten wire 33 and improve corrosion resistance as well as durability.
  • the ceramic glow plug with the above construction works as follows.
  • the heater portion 42 of the pipe 32 is heated by the heat of the first coil portion 36 because the first coil portion 36 of the tungsten wire 33 is in contact with the inner wall surface of the pipe 32 and the second coil portion 37 is exposed in the hollow portion 35.
  • the heat generated by the first coil portion 36 is dissipated through the pipe 32, the heat generated by the second coil portion 37 is not dissipated and thus the second coil portion 37 becomes extremely hot compared with the first coil portion 36.
  • the second coil portion 37 As the second coil portion 37 is heated to high temperature, it functions as a current control wire and its resistance increases suppressing the flow of current through the tungsten wire 33, thereby self-controlling the amount of heat generated by the heater portion 42.
  • the current flowing through the tungsten wire 33 increases heating the heater portion 42 by the first coil portion 36, thus keeping the amount of heat produced by the heater portion 42 at an optimum value.
  • the pipe 32 dissipates heat, maintaining the temperature of the heater portion 42 at, say, 900°C, which in turn sets the resistance of the first coil portion 36 to 0.4 ⁇ .
  • the second coil portion 37 is disposed in the sealed hollow portion 35 and thermally insulated, the temperature of the second coil portion 37 reaches 1800°C, for example, and its resistance becomes 0.6 ⁇ .
  • the total resistance of the first coil portion 36 and the second coil portion 37 amounts to 1 ⁇ , which stabilizes the current flow.
  • the ceramic coil making jig 53 is a circular cylinder body 56 made of ceramics with a through-hole 57, greater in diameter than the tungsten wire 33, formed in the center and with spiral grooves 58, 59 formed in the outer circumferential surface 60. At the end surface of the cylinder body 56 is formed a groove 61 that extends from the through-hole 57 to the outer circumferential surface 60.
  • the spiral groove 58 is smaller in pitch than the spiral groove 59 and is larger in number than the spiral groove 59.
  • the tungsten wire 33 is manufactured by using the coil making jig 53 as follows.
  • the tungsten wire is passed through the through-hole 57, bent at the groove 61 and then wound along the spiral grooves 58, 59 formed on the outer circumferential surface 60 of the cylinder body 56 Then, electricity is supplied to the ends of the tungsten wire wound on the coil making jig 53 to heat it. The heated tungsten wire is then cooled to obtain the desired form Qf the tungsten wire 33. To remove the tungsten wire 33 from the coil making jig 53, the jig 53 and the tungsten wire 33 are rotated relative to each other to make the inner coil diameter of the tungsten wire 33 larger than the diameter of the cylinder body 56. Now, the tungsten wire 33 can be easily removed from the coil making jig 53.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Resistance Heating (AREA)
  • Spark Plugs (AREA)
EP19940307223 1993-10-04 1994-10-03 Keramische Glühkerze Expired - Lifetime EP0648978B1 (de)

Applications Claiming Priority (6)

Application Number Priority Date Filing Date Title
JP269432/93 1993-10-04
JP26943193 1993-10-04
JP26943293 1993-10-04
JP269431/93 1993-10-04
JP5269432A JP3050264B2 (ja) 1993-10-04 1993-10-04 セラミック製グロープラグ
JP26943193A JPH07103480A (ja) 1993-10-04 1993-10-04 セラミック製グロープラグ

Publications (3)

Publication Number Publication Date
EP0648978A2 true EP0648978A2 (de) 1995-04-19
EP0648978A3 EP0648978A3 (de) 1996-07-24
EP0648978B1 EP0648978B1 (de) 2000-07-19

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Family Applications (1)

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EP19940307223 Expired - Lifetime EP0648978B1 (de) 1993-10-04 1994-10-03 Keramische Glühkerze

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EP (1) EP0648978B1 (de)
DE (2) DE648978T1 (de)

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0821200A1 (de) * 1996-07-26 1998-01-28 BERU Ruprecht GmbH & Co. KG Stabflammglühkerze
DE19756988C1 (de) * 1997-12-20 1999-09-02 Daimler Benz Ag Elektrisch beheizbare Glühkerze oder Glühstab für Verbrennungsmotoren
US6084212A (en) * 1999-06-16 2000-07-04 Le-Mark International Ltd Multi-layer ceramic heater element and method of making same
US6184497B1 (en) * 1999-06-16 2001-02-06 Le-Mark International Ltd. Multi-layer ceramic heater element and method of making same
DE10228077A1 (de) * 2002-06-20 2004-01-08 Friedrich-Schiller-Universität Jena Verfahren zur Herstellung einer mechanisch stabilen und elektrisch leitfähigen Verbindung zwischen einem metallischen Aufnahmeelement und einem vorzugsweise stiftförmigen keramischen Element, insbesondere bei Glühkerzen für Dieselmotoren
DE10228076A1 (de) * 2002-06-20 2004-01-08 Friedrich-Schiller-Universität Jena Verfahren zur Herstellung eines stabilen elektrischen Kontaktes an ein vorzugsweise stiftförmiges keramisches Element, insbesondere bei Glühkerzen für Dieselmotoren
EP2088373A1 (de) 2008-02-07 2009-08-12 Robert Bosch GmbH Metallische Glühstiftkerze mit Temperaturmessung
WO2014202265A1 (de) * 2013-06-21 2014-12-24 Robert Bosch Gmbh Glühstiftkerze für glühtemperaturregelung
EP2886960A1 (de) * 2013-12-23 2015-06-24 SIEVA d.o.o., PE Spodnja Idrija Heizstab mit keramischer Innenhülse, Glühkerze und Herstellungsverfahren dafür
US10993288B2 (en) 2015-08-21 2021-04-27 Chongqing Le-Mark Ceramic Technology Co Limited Ceramic electric heating element

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DE102005024622B4 (de) * 2005-05-30 2007-10-04 Beru Ag Stabglühkerze

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JPS5872821A (ja) * 1981-10-26 1983-04-30 Ngk Spark Plug Co Ltd グロ−プラグとその製法
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Cited By (15)

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Publication number Priority date Publication date Assignee Title
US5880433A (en) * 1996-07-26 1999-03-09 Beru Ruprecht Gmbh & Co. Kg Rod-type flame glow plug
EP0821200A1 (de) * 1996-07-26 1998-01-28 BERU Ruprecht GmbH & Co. KG Stabflammglühkerze
US6121577A (en) * 1997-12-20 2000-09-19 Daimlerchrysler Ag Electrically heatable glow plug with oxygen getter material
DE19756988C1 (de) * 1997-12-20 1999-09-02 Daimler Benz Ag Elektrisch beheizbare Glühkerze oder Glühstab für Verbrennungsmotoren
US6043459A (en) * 1997-12-20 2000-03-28 Daimlerchrysler Ag And Beru Ag Electrically heatable glow plug with oxygen getter material
US6184497B1 (en) * 1999-06-16 2001-02-06 Le-Mark International Ltd. Multi-layer ceramic heater element and method of making same
US6084212A (en) * 1999-06-16 2000-07-04 Le-Mark International Ltd Multi-layer ceramic heater element and method of making same
DE10228077A1 (de) * 2002-06-20 2004-01-08 Friedrich-Schiller-Universität Jena Verfahren zur Herstellung einer mechanisch stabilen und elektrisch leitfähigen Verbindung zwischen einem metallischen Aufnahmeelement und einem vorzugsweise stiftförmigen keramischen Element, insbesondere bei Glühkerzen für Dieselmotoren
DE10228076A1 (de) * 2002-06-20 2004-01-08 Friedrich-Schiller-Universität Jena Verfahren zur Herstellung eines stabilen elektrischen Kontaktes an ein vorzugsweise stiftförmiges keramisches Element, insbesondere bei Glühkerzen für Dieselmotoren
EP2088373A1 (de) 2008-02-07 2009-08-12 Robert Bosch GmbH Metallische Glühstiftkerze mit Temperaturmessung
WO2014202265A1 (de) * 2013-06-21 2014-12-24 Robert Bosch Gmbh Glühstiftkerze für glühtemperaturregelung
EP2886960A1 (de) * 2013-12-23 2015-06-24 SIEVA d.o.o., PE Spodnja Idrija Heizstab mit keramischer Innenhülse, Glühkerze und Herstellungsverfahren dafür
WO2015097044A1 (en) * 2013-12-23 2015-07-02 Sieva D.O.O.,Pe Spodnja Idrija Heating rod comprising a ceramic internal sleeve, glow plug and method for manufacturing the same
US10993288B2 (en) 2015-08-21 2021-04-27 Chongqing Le-Mark Ceramic Technology Co Limited Ceramic electric heating element
US11930564B2 (en) 2015-08-21 2024-03-12 Chongqing Le-Mark Technology Co Ceramic electric heating element

Also Published As

Publication number Publication date
EP0648978A3 (de) 1996-07-24
DE648978T1 (de) 1996-06-27
DE69425308D1 (de) 2000-08-24
EP0648978B1 (de) 2000-07-19

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