EP3736493B1 - Glühkerze - Google Patents

Glühkerze Download PDF

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Publication number
EP3736493B1
EP3736493B1 EP18880219.3A EP18880219A EP3736493B1 EP 3736493 B1 EP3736493 B1 EP 3736493B1 EP 18880219 A EP18880219 A EP 18880219A EP 3736493 B1 EP3736493 B1 EP 3736493B1
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Prior art keywords
ceramic
heat generating
generating section
tip
length
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French (fr)
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EP3736493A4 (de
EP3736493A1 (de
Inventor
Kan CHO
Andreas Reissner
Dietmar Hahn
Yasuo Toyoshima
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Robert Bosch GmbH
Bosch Corp
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Robert Bosch GmbH
Bosch Corp
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    • 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 glow plug that is used to aid starting an internal combustion engine such as a diesel engine.
  • a glow plug of a ceramic heater type As a glow plug used to aid starting a diesel engine, a glow plug of a ceramic heater type has been known.
  • a glow plug of the ceramic heater type includes: a ceramic heater; and an outer cylinder that accommodates a part of the ceramic heater such that at least a tip of the ceramic heater is exposed.
  • the ceramic heater has: a heat generating section arranged at the tip of the heater; and a lead connected to a rear end of the heat generating section and having lower resistivity than the heat generating section. These heat generating section and lead are covered with an insulating ceramic.
  • an outer circumferential surface of the ceramic heater and an inner circumferential surface of the outer cylinder are electrically connected via a joint section such as brazing (for example, see JP-A-2002-334768 ).
  • Document JP 2002-203665A discloses a glow plug with a ceramic heater with a ceramic heating resistor embedded in an insulating ceramic, wherein the resistor includes straight portions having a semi-circular cross-section, and wherein a maximum cross-sectional dimension of the straight portions of the heating resistor is limited to 40% of the outer diameter of the insulating ceramic.
  • a thickness of the insulating ceramic between an outer circumferential surface of the insulating ceramic and a conductive ceramic embedded in the insulating ceramic is not concerned for purposes of a rapid temperature increase of the ceramic heater and a reduction in power consumption. It is considered that thinning of the insulating ceramic is effective for the rapid temperature increase. However, aging deterioration of the insulating ceramic possibly accelerates exposure of the heat generating section inside. Thus, simple thinning of the insulating ceramic is not sufficient.
  • the joint section between the ceramic heater and the outer cylinder is formed of a high thermal conducting brazing material, for example.
  • heat is easily transferred from the ceramic heater to the outer cylinder. That is, the heat is likely to be released from the ceramic heater via the joint section.
  • a position of the heat generating section in the ceramic heater, a joint range between the ceramic heater and the outer cylinder, and the like are not concerned from perspectives of the rapid temperature increase and the reduction in the power consumption.
  • the present invention has been made in view of the above problem and therefore has a purpose of providing a glow plug capable of achieving a rapid temperature increase while suppressing power consumption.
  • the present invention provides a ceramic heater in accordance with claim 1.
  • the ceramic heater that has a conductive ceramic and an insulating ceramic covering the conductive ceramic.
  • the conductive ceramic has: a heat generating section that is arranged at a tip; and a lead that is connected to a rear end of the heat generating section.
  • the insulating ceramic has a thinnest portion, where an outer circumferential surface thereof and the heat generating section are closest to each other, in a thickness of 0.57 to 0.66 mm.
  • the outer circumferential surface of the insulating ceramic is preferably in a cylindrical shape that has a diameter of 2.9 to 3.1 mm.
  • a length in an axial direction from a tip of the insulating ceramic to the rear end of the heat generating section is equal to or shorter than 4.5 mm.
  • the present invention provides a ceramic heater in accordance with claim 3.
  • the ceramic heater has a conductive ceramic and an insulating ceramic covering the conductive ceramic; and an outer cylinder that accommodates a part of the ceramic heater such that at least a tip is exposed and an inner circumferential surface of which is joined to an outer circumferential surface of the ceramic heater via a joint section.
  • the conductive ceramic has: a heat generating section that is arranged at a tip; and a lead that is connected to a rear end of the heat generating section.
  • the joint section is a section of the outer circumferential surface of the insulating ceramic metalized with a brazing material, wherein the joint section is formed from a tip of the outer cylinder to a position where a rear end side of the insulating ceramic contacts the inner circumferential surface of the outer cylinder.
  • the first length A is equal to or shorter than 4.5 mm.
  • Fig. 1 is a cross-sectional view for illustrating a configuration of a glow plug.
  • Fig. 2 is a cross-sectional view that is taken along line II-II in Fig. 1 .
  • Fig. 3 is a cross-sectional view that is taken along line III-III in Fig. 1 .
  • a glow plug 1 is a glow plug of a ceramic heater type, for example, and includes, as illustrated in Fig. 1 : a ceramic heater 10; a metallic outer cylinder 20 that accommodates a part of the ceramic heater 10 such that at least a tip thereof is exposed and an inner circumferential surface of which is joined to an outer circumferential surface of the ceramic heater 10 via a joint section 21; and a housing 30.
  • the ceramic heater 10 aids starting an internal combustion engine, has the tip that is inserted in a combustion chamber (a pre-combustion chamber in the case of the internal combustion engine of a pre-combustion type or the combustion chamber of the internal combustion engine in the case of the internal combustion engine of a direct-injection type), and is fixed to the housing 30 via the outer cylinder 20.
  • the ceramic heater 10 is formed of a ceramic.
  • the ceramic heater 10 has a conductive ceramic 11 and an insulating ceramic 16 that covers the conductive ceramic 11.
  • the conductive ceramic 11 is heated by energization in the glow plug 1, and has: a heat generating section 12 that is arranged at a tip and is molded in a U-shape; and a lead 14 that is connected to a rear end of the heat generating section 12.
  • the heat generating section 12 is not limited to have a particular shape but can have any one of various shapes such as a circle, an oval, an elongated circle, and a polygon.
  • the heat generating section 12 has: a pair of extending sections 12a, 12b that extend in parallel with each other along the axis x of the ceramic heater 10; and a curved section 12c that couples the extending sections 12a, 12b.
  • the heat generating section 12 is located within a range of 4.5 mm from a tip of the insulating ceramic 16, and is dimensioned to have a length l 1 of 3.5 mm along the axis x of the ceramic heater 10.
  • the heat generating section 12 is a heat generating resistance element having high resistivity against the lead 14, and is formed of the conductive ceramic.
  • the heat generating section 12 is formed of a material that has, as a primary component, a carbide, a nitride, or a silicide containing tungsten (W), molybdenum (Mo), titanium (Ti), or the like.
  • the heat generating section 12 is particularly preferred to have high thermal resistance and contain tungsten carbide (WC) that has inorganic conductivity from a point of having low specific resistance.
  • the heat generating section 12 contains silicon nitride (Si 3 N 4 ), and percentage of a silicon nitride (Si 3 N 4 ) content is preferably equal to or higher than 20% by mass.
  • silicon nitride (Si 3 N 4 ) in the insulating ceramic 16 that contains a silicon nitride ceramic a conductor component that serves as the heat generating section 12 has a high coefficient of thermal expansion, and thus is usually in a state of being applied with tensile stress.
  • silicon nitride (Si 3 N 4 ) to the heat generating section 12, the coefficient of thermal expansion is made to approximate the coefficient of thermal expansion of the insulating ceramic 16. In this way, it is possible to alleviate stress generated by a difference in the coefficient of thermal expansion at a time of a temperature increase and a time of a temperature decrease of the ceramic heater 10.
  • the percentage of the silicon nitride (Si 3 N 4 ) content contained in the heat generating section 12 is equal to or lower than 40% by mass, a resistance value of the heat generating section 12 can be reduced to be small and stabilized.
  • the percentage of the silicon nitride (Si 3 N 4 ) content in the heat generating section 12 is preferably 20 to 40% by mass.
  • the percentage of the silicon nitride (Si 3 N 4 ) content is further preferably 25 to 35% by mass.
  • the heat generating section 12 may contain at least one type of elements (titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), and iron (Fe)) in groups 4, 5, 6, 7, 8 of period 4 in a periodic table of elements.
  • percentage of a content of each of the elements including titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), and iron (Fe) in the heat generating section 12 is preferably equal to or lower than 0.5 mol%.
  • the tip of the lead 14 is connected to the rear end of the heat generating section 12, and a rear end thereof is exposed from the insulating ceramic 16.
  • the lead 14 includes a positive electrode-side lead 14a and a negative electrode-side lead 14b.
  • Each of the positive electrode-side lead 14a and the negative electrode-side lead 14b is formed of the conductive ceramic having low resistivity against the heat generating section 12.
  • the positive electrode-side lead 14a and the negative electrode-side lead 14b extend in parallel with each other along the axis x of the ceramic heater 10.
  • the positive electrode-side lead 14a and the negative electrode-side lead 14b are respectively connected to ends of the extending sections 12a, 12b of the heat generating section 12 extending in the U-shape.
  • a tip of the positive electrode-side lead 14a is connected to the extending section 12a of the heat generating section 12.
  • the positive electrode-side lead 14a extends to a rear end of the insulating ceramic 16.
  • the positive electrode-side lead 14a is exposed from the insulating ceramic 16 and is electrically connected to a lead wire 115 via a cap-shaped connection section 114.
  • a tip of the negative electrode-side lead 14b is connected to the extending section 12b of the heat generating section 12, and a rear end thereof has an exposed section 14c where a part of the negative electrode-side lead 14b is exposed to an outer circumferential surface of the insulating ceramic 16.
  • the exposed section 14c of the lead 14 is joined to an inner circumferential surface of the outer cylinder 20 via the joint section 21, which will be described later, by brazing or the like.
  • the lead 14 is electrically connected to the outer cylinder 20, which is formed of a metallic material having conductivity, via the exposed section 14c.
  • the exposed section 14c of the lead 14 functions as a negative electrode-side electrode.
  • the lead 14 contains, as a primary component, tungsten carbide (WC) that is an inorganic conductor, and silicon nitride (Si 3 N 4 ) is preferably added thereto such that percentage of the silicon nitride (Si 3 N 4 ) content becomes equal to or higher than 15% by mass. As the percentage of the silicon nitride (Si 3 N 4 ) content is increased, a coefficient of thermal expansion of each of the positive electrode-side lead 14a and the negative electrode-side lead 14b can approximate a coefficient of thermal expansion of silicon nitride (Si 3 N 4 ) that is contained in the insulating ceramic 16.
  • WC tungsten carbide
  • Si 3 N 4 silicon nitride
  • the percentage of the silicon nitride content is equal to or lower than 40% by mass, a resistance value of each of the positive electrode-side lead 14a and the negative electrode-side lead 14b is reduced to be small and stabilized.
  • the percentage of the silicon nitride (Si 3 N 4 ) content is preferably 15 to 40% by mass.
  • the percentage of the silicon nitride (Si 3 N 4 ) content is further preferably 20 to 35% by mass.
  • the lead 14 may contain an oxide and/or a nitride containing at least one type of elements (titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), and iron (Fe)) in groups 4, 5, 6, 7, 8 of period 4 in the periodic table of elements.
  • the percentage of the content of each of the elements including titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), and iron (Fe) in the lead 14 is preferably equal to or lower than 0.5 mol%.
  • the lead 14 is preferably a mixture that contains a rare earth element compound such as chromium oxide (Cr 2 O 3 ) of about several tens of ppm, and is a sintered body formed by sintering.
  • a rare earth element compound such as chromium oxide (Cr 2 O 3 ) of about several tens of ppm
  • the lead 14 is formed of the same material as that for the heat generating section 12, but contains a larger amount of the forming material than the heat generating section 12 and has a larger cross-sectional area than the heat generating section 12, for example. In this way, the lead 14 has the smaller resistance value per unit length than the heat generating section 12.
  • the insulating ceramic 16 is a sintered body which is formed by sintering and the outer circumferential surface of which has a cylindrical shape, for example.
  • the insulating ceramic 16 covers the conductive ceramic 11. More specifically, the insulating ceramic 16 covers the heat generating section 12 and the lead 14. In other words, the heat generating section 12 and the lead 14 are embedded in the insulating ceramic 16.
  • the insulating ceramic 16 has a diameter d of 2.9 to 3.1 mm and the outer circumferential surface is in a cylindrical shape.
  • the diameter d is preferably 2.9 mm.
  • the "diameter d of the insulating ceramic 16" is not a diameter of a dome-shaped portion but is a diameter of a cylindrical portion of the outer circumferential surface.
  • a distance (length) l 2 between a tip of the curved section 12c of the heat generating section 12 and the tip of the insulating ceramic 16 is about 0.97 mm.
  • a thickness t 1 of a thin portion (the thinnest portion) 16a where the outer circumferential surface of the insulating ceramic 16 is closest to each of the extending sections 12a, 12b of the heat generating section 12 falls within a range from 0.5 to 0.7 mm.
  • the thickness t 1 of the thin portion 16a is 0.57 to 0.66 mm.
  • the "closest” in this embodiment means that the thickness t 1 of the thin portion 16a of the insulating ceramic 16 between the outer circumferential surface of the insulating ceramic 16 and each of the extending sections 12a, 12b of the heat generating section 12 (here, each of outer circumferential surfaces of the extending sections 12a, 12b) falls within the range from 0.5 to 0.7 mm.
  • the thin portion 16a in the cross section that is perpendicular to the axis x, the thin portion 16a is a portion whose thickness t 1 that is the shortest distance from the outer circumferential surface of the insulating ceramic 16 to the outer circumferential surface of the heat generating section 12 is 0.5 to 0.7 mm.
  • a portion other than the thin portion 16a may be 0.5 to 0.7 mm in thickness.
  • the insulating ceramic 16 has a thin portion 16b in a region covering the lead 14.
  • a thickness t 2 of insulating ceramic 16 between each of the positive electrode-side lead 14a and the negative electrode-side lead 14b and the outer circumferential surface of the insulating ceramic 16 falls within a range from 0.25 to 0.4 mm.
  • the thin portion 16b is preferably 0.25 to 0.35 mm in thickness.
  • the thin portion 16b is a portion whose thickness t 2 that is the shortest distance from the outer circumferential surface of the insulating ceramic 16 to the outer circumferential surface of the lead 14 is 0.25 to 0.4 mm.
  • a length (a first length) A in an axis x direction from the tip of the insulating ceramic 16 to the rear end of the heat generating section 12, more specifically, to the rear end of each of the extending sections 12a, 12b of the heat generating section 12 is equal to or shorter than 4.5 mm.
  • a length (a second length) B in the axis x direction from the tip of the insulating ceramic 16 to a tip of the joint section 21, which will be described later, is 12 to 20 mm
  • a length (a third length) C in the axis x direction of the joint section 21 is 2.8 to 10.8 mm.
  • the length A with respect to the length B of the insulating ceramic 16 satisfies the following formula (Formula 1) .
  • the length A with respect to the length B of the insulating ceramic 16 preferably satisfies the following formula (Formula 3).
  • the length C with respect to a total length (B + C) of the length B and the length C of the insulating ceramic 16 satisfies the following formula (Formula 2).
  • the length C with respect to the total length (B + C) of the length B and the length C of the insulating ceramic 16 preferably satisfies the following formula (Formula 4).
  • the entire heat generating section 12 is located within the range of 4.5 mm from the tip of the insulating ceramic 16 along the axis x.
  • the ceramic heater 10 With the insulating ceramic 16 that is formed of the ceramic, it is possible to provide the ceramic heater 10 with high reliability during a rapid temperature increase.
  • ceramics are ceramics having electric insulation properties such as an oxide ceramic, a nitrogen ceramic, and a carbide ceramic.
  • silicon nitride as the primary component of the silicon nitride ceramic is superior in terms of high strength, high toughness, the high insulation property, and thermal resistance.
  • This silicon nitride ceramic is obtained by mixing, as sintering additives, a rare earth oxide, an aluminum oxide (Al 2 O 3 ), a content of which is 0.5 to 3% by mass, and a silicon dioxide (SiO 2 ) with silicon nitride and by hot pressing, for example.
  • the rare earth oxide are an yttrium oxide (Y 2 O 3 ), an ytterbium oxide (Yb 2 O 3 ), and an erbium oxide (Er 2 O 3 ), a content of each of which is 3 to 120 by mass.
  • Silicon dioxide (SiO 2 ) is contained in such an amount that the sintered body contains 1.5 to 5% of a silicon dioxide (SiO 2 ) content by mass.
  • the insulating ceramic 16 that is formed of the silicon nitride ceramic is used, molybdenum disilicide (MoSi 2 ), tungsten disilicide (WSi 2 ), and the like are preferably mixed and dispersed.
  • MoSi 2 molybdenum disilicide
  • WSi 2 tungsten disilicide
  • a coefficient of thermal expansion of the silicon nitride ceramic as a base material can approximate the coefficient of thermal expansion of the heat generating section 12. In this way, durability of the ceramic heater 10 can be improved.
  • the outer cylinder 20 is formed of stainless steel such as SUS 430 in a cylindrical shape, for example. As illustrated in Fig. 1 , the outer cylinder 20 accommodates the ceramic heater 10 in a state where a tip portion of the ceramic heater 10 is exposed. In the state of accommodating the ceramic heater 10, the inner circumferential surface of the outer cylinder 20 is formed with the joint section 21 for a specified length along the axis x of the ceramic heater 10. For example, in the joint section 21, the ceramic heater 10 and the outer cylinder 20 are joined by brazing using a brazing material such as a silver filler.
  • a brazing material such as a silver filler.
  • the joint section 21 is formed by metalizing the outer circumferential surface of the insulating ceramic 16 with the brazing material such as the silver filler, and is formed for the specified length (corresponding to the length C.) between the outer circumferential surface of the ceramic heater 10 and the inner circumferential surface of the outer cylinder 20 along the axis x of the ceramic heater 10.
  • the joint section 21 is formed from a tip of the outer cylinder 20 to a position where the rear end side of the insulating ceramic 16 contacts an inner circumferential surface of a tip portion 22 of the outer cylinder 20.
  • a tip of the joint section 21 may be located in front of the outer cylinder 20 or inside the outer cylinder 20.
  • the housing 30 is an attachment jig to a cylinder head of the engine, which is not illustrated, and, as illustrated in Fig. 1 , accommodates the ceramic heater 10 and the outer cylinder 20.
  • the housing 30 is formed of a thermally conductive metallic material with a superior heat dissipation property.
  • the housing 30 is formed in a cylindrical shape, for example.
  • a rear end side of the ceramic heater 10 is partially supported by the outer cylinder 20, and the outer cylinder 20 is arranged in the housing 30. In this state, the tip side of the ceramic heater 10 is projected to the outside from a tip of the housing 30.
  • Table 1 shows various specifications and various simulation results of Examples 1, 2 and Comparative Example 1.
  • the diameter d (mm) of the insulating ceramic 16, the thickness t 1 (mm) of the thin portion 16a between the heat generating section 12 and the outer circumferential surface of the insulating ceramic 16, and the thickness t 2 (mm) of the thin portion 16b between the lead 14 and the outer circumferential surface of the insulating ceramic 16 are within the numerical ranges in the above embodiment.
  • the numerical values do not fall within the numerical ranges in the above embodiment.
  • Example 2 in which the diameter d of the ceramic heater 10 was smaller than 3.2 mm and the thickness t 1 of the thin portion 16a was less than 0.7 mm, temperature increase duration up to 1000 °C was shorter than that in Comparative Example 1 in which the diameter d was larger than 3.2 mm and the thickness t 1 of the thin portion 16a exceeded 0.7 mm.
  • Example 2 in which the diameter d was 2.9 mm and the thickness t 1 was 0.57 mm, the temperature increase duration up to 1000 °C was shorter than 1 second, and thus a superior temperature increase property was exhibited.
  • Example 2 Furthermore, it was found that the temperature of the heat generating section 12 after energization for two seconds in each of Examples 1, 2 was higher than the temperature in Comparative Example 1, the temperature exceeds 1500 °C in Example 2, and thus the superior temperature increase property was exhibited in Example 2.
  • the diameter d further preferably satisfies a condition of 2.9 to 3.1 mm.
  • the heat generating section 12 is possibly exposed early.
  • tungsten (W) contained in the material for the heat generating section 12 is oxidized, which possibly destroys the heat generating section 12.
  • the early exposure of the heat generating section 12 is avoided to achieve a long life span of the glow plug 1 and also to achieve the rapid temperature increase and the reduced power consumption.
  • Table 2 shows various specifications and various simulation results of Examples 3 to 5 and Comparative Examples 2, 3.
  • the diameter d (mm) of the insulating ceramic 16, the thickness t 1 (mm) of the thin portion 16a between the heat generating section 12 and the outer circumferential surface of the insulating ceramic 16, and the thickness t 2 (mm) of the thin portion 16b between the lead 14 and the outer circumferential surface of the insulating ceramic 16 are the same as those in Example 2 but the length B in the axial direction from the tip of the insulating ceramic 16 to the tip of the joint section 21 and the length C in the axial direction of the joint section 21 differ.
  • the temperature of the ceramic heater 10 satisfying conditions that a ratio (A/B) of the length A to the length B in the insulating ceramic 16 was 0.2 to 0.4 and that a ratio (C/B + C) of the length C to the length B + C in the insulating ceramic 16 was 0.1 to 0.5 after 60 seconds reached about 1200 °C.
  • Example 3 a value of A/B was 0.375, and a value of C/B + C was about 0.474. In Example 4, the value of A/B was about 0.321, and the value of C/B + C was about 0.386. In Example 5, the value of A/B was 0.225, and the value of C/B + C was about 0.123. In the case where Comparative Examples 2,3 in which none of the conditions of the ratios was satisfied were compared to Examples 3 to 5, it was found that the superior temperature increase property was exhibited in Examples 3 to 5 .
  • the consumed power after 60 seconds from the initiation of the simulations was equal to or lower than 29 W in the case where the above conditions of the ratios were satisfied as in Examples 3 to 5 and that the consumed power in Examples 3 to 5 was lower than the consumed power in Comparative Examples 2, 3.
  • a joint area between the joint section 21, which is formed by the silver filler with high thermal conductivity, and the ceramic heater 10 is suppressed to be small. In this way, it is configured that heat from the ceramic heater 10 is unlikely to be released. Thus, a superior heat retaining property can be exhibited near the heat generating section 12.
  • Example 3 to 5 the temperature near the heat generating section 12 could be kept high.
  • a temperature of the joint section 21 between the negative electrode-side lead 14b and the outer cylinder 20, that is, a temperature of the exposed section 14c of the lead 14 could be suppressed below 450 °C.
  • Comparative Examples 2, 3 the temperature of the exposed section of the lead was equal to or higher than 450 °C. From what have been described so far, it was found that, in Examples 3 to 5, a negative impact on the brazing material for the joint section 21 by heat could be suppressed to be small.
  • Table 3 shows various specifications and various simulation results of Example 6 and Comparative Example 4 in which the diameter d (mm) of the insulating ceramic 16, the thickness t 1 (mm) of the thin portion between the heat generating section 12 and the outer circumferential surface of the insulating ceramic 16, and the thickness t 2 (mm) of the thin portion 16a between the lead 14 and the outer circumferential surface of the insulating ceramic 16 are the same as those in Example 2 but the length l 1 of the heat generating section 12 differs and Comparative Example 5 in which the diameter d (mm), the thickness t 1 (mm), and the thickness t 2 (mm) are the same as those in Comparative Example 1 and the length l 1 of the heat generating section 12 is the same as that in Example 6.
  • Example 6 in which the length A in the axis x direction from the tip of the insulating ceramic 16 to the rear end of the heat generating section 12 became equal to or shorter than 4.5 mm (A ⁇ 4.5 (mm)), the temperature increase duration up to 1000 °C was 0.98 second and thus was shorter than 1 second.
  • the thickness t 1 of the thin portion 16a where the outer circumferential surface of the insulating ceramic 16 is adjacent to the heat generating section 12 falls within the range from 0.5 to 0.7 mm.
  • the thickness t 1 of the thin portion 16a is 0.57 to 0.66 mm, and the diameter d of the insulating ceramic 16 is further preferably 2.9 to 3.1 mm.
  • the entire heat generating section 12 is located within the range of 4.5 mm from the tip of the insulating ceramic 16, it is possible to shorten the duration until reaching 1000 °C in comparison with the case where the length A in the axis x direction from the tip of the insulating ceramic 16 to the rear ends of the extending sections 12a, 12b of the heat generating section 12 exceeds 4.5 mm.
  • a cross-sectional shape of the ceramic heater 10 that is perpendicular to the axis x is not limited to a circular shape but may be another shape such as an oval shape or a polygonal shape.
  • a cross-sectional shape of each of the heat generating section 12 and the lead 14 is not limited to the oval shape as illustrated in FIGs. 2, 3 but may be another shape such as the circular shape or the polygonal shape including a rectangular shape.

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Claims (4)

  1. Glühkerze (1), Folgendes umfassend:
    ein keramisches Heizelement (10), das eine leitfähige Keramik (11) und eine isolierende Keramik (16), welche die leitfähige Keramik (11) bedeckt, aufweist, wobei
    die leitfähige Keramik (11) einen Wärmeerzeugungsabschnitt (12), der an einer Spitze angeordnet ist, und eine Leitung (14), die mit einem hinteren Ende des Wärmeerzeugungsabschnitts (12) verbunden ist, aufweist und
    in einem Querschnitt, der senkrecht zu einer Achse (X) des keramischen Heizelements (10) ist, die isolierende Keramik (16) einen dünnsten Teilbereich (16a), wo eine äußere Umfangsfläche der isolierenden Keramik (16) und der Wärmeerzeugungsabschnitt (12) einander am nächsten sind, mit einer Dicke (t1) von 0,57 bis 0,66 mm aufweist und
    eine Länge (A) in einer axialen Richtung von einer Spitze der isolierenden Keramik (16) bis zu einem hinteren Ende des Wärmeerzeugungsabschnitts (12) gleich oder kürzer als 4,5 mm ist.
  2. Glühkerze (1) nach Anspruch 1, wobei
    die äußere Umfangsfläche der isolierenden Keramik (16) in einer zylindrischen Form vorliegt, die einen Durchmesser (d) von 2,9 bis 3,1 mm aufweist.
  3. Glühkerze (1), Folgendes umfassend:
    ein keramisches Heizelement (10), das eine leitfähige Keramik (11) und eine isolierende Keramik (16), welche die leitfähige Keramik (11) bedeckt, aufweist; und
    einen äußeren Zylinder (20), der einen Teil des keramischen Heizelements (10) derart aufnimmt, dass wenigstens eine Spitze freiliegt und eine innere Umfangsfläche des äußeren Zylinders (20) mit einer äußeren Umfangsfläche des keramischen Heizelements (10) über einen Verbindungsabschnitt (21) verbunden ist, der ein mit einem Lötmaterial metallisierter Abschnitt der äußeren Umfangsfläche der isolierenden Keramik (16) ist, wobei der Verbindungsabschnitt (21) von einer Spitze des äußeren Zylinders (20) bis zu einer Stelle, wo eine hintere Endseite der isolierenden Keramik (16) mit einer inneren Umfangsfläche des äußeren Zylinders (20) in Kontakt steht, ausgebildet ist, wobei die leitfähige Keramik (11) einen Wärmeerzeugungsabschnitt (12),
    der an der Spitze des keramischen Heizelements (10) angeordnet ist, und eine Leitung (14), die mit einem hinteren Ende des Wärmeerzeugungsabschnitts (12) verbunden ist, aufweist und
    wenn eine Länge in einer axialen Richtung von einer Spitze der isolierenden Keramik (16) bis zu dem hinteren Ende des Wärmeerzeugungsabschnitts (12) als eine erste Länge A festgelegt ist,
    eine Länge in der axialen Richtung von der Spitze der isolierenden Keramik (16) bis zu einer Spitze des Verbindungsabschnitts (21) als eine zweite Länge B festgelegt ist und
    eine Länge in der axialen Richtung des Verbindungsabschnitts (21) als eine dritte Länge C festgelegt ist,
    die folgende Formel 1 und Formel 2 erfüllt sind: A B < 0,55
    Figure imgb0017
     C B + C < 0,55
    Figure imgb0018
    und wobei die erste Länge A gleich oder kürzer als 4,5 mm ist.
  4. Glühkerze nach Anspruch 3, welche die
    folgende Formel 3 und Formel 4 erfüllt. A B < 0 , 5
    Figure imgb0019
     C B + C < 0 , 5
    Figure imgb0020
EP18880219.3A 2017-11-21 2018-09-26 Glühkerze Active EP3736493B1 (de)

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JPS62731A (ja) * 1985-06-27 1987-01-06 Jidosha Kiki Co Ltd デイ−ゼルエンジン用グロ−プラグ
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