WO2013001883A1 - セラミックスヒータ型グロープラグ - Google Patents
セラミックスヒータ型グロープラグ Download PDFInfo
- Publication number
- WO2013001883A1 WO2013001883A1 PCT/JP2012/059165 JP2012059165W WO2013001883A1 WO 2013001883 A1 WO2013001883 A1 WO 2013001883A1 JP 2012059165 W JP2012059165 W JP 2012059165W WO 2013001883 A1 WO2013001883 A1 WO 2013001883A1
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- WO
- WIPO (PCT)
- Prior art keywords
- ceramic heater
- glow plug
- insulator
- metal outer
- outer cylinder
- Prior art date
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Classifications
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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
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02P—IGNITION, OTHER THAN COMPRESSION IGNITION, FOR INTERNAL-COMBUSTION ENGINES; TESTING OF IGNITION TIMING IN COMPRESSION-IGNITION ENGINES
- F02P19/00—Incandescent ignition, e.g. during starting of internal combustion engines; Combination of incandescent and spark ignition
- F02P19/02—Incandescent ignition, e.g. during starting of internal combustion engines; Combination of incandescent and spark ignition electric, e.g. layout of circuits of apparatus having glowing plugs
- F02P19/026—Glow plug actuation during engine operation
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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
- F23Q2007/004—Manufacturing or assembling methods
Definitions
- the present invention relates to a ceramic heater type glow plug used as a starting aid for a diesel engine.
- the present invention relates to a ceramic heater type glow plug having a configuration in which a heat-resistant insulator powder is sealed as a sealing material inside a metal outer cylinder holding a ceramic heater.
- Ceramic heater type glow plugs used for diesel engine start-up assistance generally have a structure in which the heat generating part on the front end side of the ceramic heater protrudes outside and the rear end side is held in a metal outer cylinder. Have. In such a ceramic heater type glow plug, the rear end side of the metal outer cylinder is inserted and fixed into the front end portion of a cylindrical housing which is a fitting for mounting on the cylinder head of the engine.
- one electrode (negative electrode) of the ceramic heater is taken out to the outer surface of the heater body and electrically connected to the inner surface of the metal outer cylinder, and the other electrode (positive electrode) is connected to the rear end. It is taken out from the part side through the electrode extraction fitting.
- the electrode extracted to the outside by the electrode extraction fitting is electrically connected to an external connection terminal fixed to the rear end portion side of the housing via an insulating member.
- the rear end of the ceramic heater is ground to form a small diameter portion, or the rear end of the ceramic heater. Or a taper is formed.
- the heat-resistant insulator particles sealed in the metal outer cylinder have a relatively high rigidity, and when the deformation of the metal outer cylinder occurs due to swaging, the ceramic heater is interposed via the heat-resistant insulator particles. Stress may propagate to the connecting portion between the positive electrode and the electrode extraction fitting, and the rear end portion of the ceramic heater or the electrode extraction fitting may be damaged.
- the inventor of the present invention mixes a lubricity improver with the heat-resistant insulating particles around at least the connection portion between one electrode of the ceramic heater and the electrode take-out member. And the present invention has been completed. That is, the present invention reduces the stress propagated to the connecting portion between the one electrode of the ceramic heater and the electrode extraction member even when the metal outer cylinder is deformed, and the ceramic heater and the electrode extraction member It is an object of the present invention to provide a ceramic heater type glow plug that can prevent damage to the ceramic heater.
- a ceramic heater a metal outer cylinder in which the ceramic heater is held at one end and the other end is inserted and fixed in an inner hole of the housing, and the metal outer cylinder in the metal outer cylinder
- An electrode extraction member connected to one electrode of the ceramic heater, and in a ceramic heater type glow plug in which heat-resistant insulating particles are sealed as a sealing material in the metal outer cylinder, at least the one electrode and the electrode
- a ceramic heater type glow plug characterized in that an insulator mixed powder mixed with a lubricity improving material for improving the lubricity between the heat-resistant insulator particles is filled around a connection portion with an electrode extraction member.
- the ceramic heater type glow plug according to the present invention fills at least the periphery of the connection portion between one electrode of the ceramic heater and the electrode extraction member with the insulator mixed powder mixed with the lubricity improving material. Even when deformation or the like of the metal outer cylinder occurs, it is possible to relieve the stress propagated to the connecting portion due to slippage between the heat-resistant insulator particles. Therefore, damage to the ceramic heater and the electrode extraction member can be reduced.
- the average particle size of the lubricity improving material is smaller than the average particle size of the heat-resistant insulator particles.
- the lubricity improving material between the heat resistant insulator particles by mixing such a lubricity improving material with the heat resistant insulator particles. Further, by using such a lubricity improving material, the packing density of the insulator mixed powder can be increased, so that the electrode extraction member and other members inserted into the metal outer cylinder are firmly held. In addition, the heat generated from the electrode extraction member can be efficiently dissipated.
- the thermal conductivity of the lubricity improving material is larger than the thermal conductivity of the heat resistant insulator particles.
- the heat-resistant insulator particles and the lubricity improver are arranged so that the tapping density of the insulator mixed powder is larger than the tapping density of the heat-resistant insulator particles. It is preferable to determine the mixing ratio.
- the packing density of the insulator mixed powder can be increased and inserted into the electrode extraction member or other metal outer cylinder. Can be held more firmly, and heat generated from the electrode extraction member can be dissipated more efficiently.
- the heat-resistant insulator particles are magnesia (MgO) and the lubricity improving material is hexagonal boron nitride (h-BN).
- the insulator mixed powder By configuring the insulator mixed powder using such materials, the insulator mixed powder excellent in heat resistance, electrical insulation, thermal conductivity, and lubricity is filled, and the ceramic heater and electrode extraction member are damaged. Therefore, it is possible to obtain a ceramic heater type glow plug having a low heat generation efficiency and excellent heat generation efficiency.
- the ceramic heater type glow plug of the present invention it is preferable to enclose the insulator mixed powder in the entire metal outer cylinder.
- the heat-resistant insulator particles can be filled into the metal outer cylinder in one step, and the production efficiency of the ceramic heater type glow plug can be improved. Can do.
- FIG. 1 is a cross-sectional view of a diesel engine glow plug 10 according to a first embodiment of the present invention.
- a glow plug 10 shown in FIG. 1 is configured as a ceramic heater type glow plug including a ceramic heater assembly 20.
- the ceramic heater assembly 20 includes a ceramic heater 21, an electrode extraction fitting 23, an electrode extraction rod 27, a metal outer cylinder (sheath) 25, and the like as main components.
- the ceramic heater 21 has a U-shaped ceramic heating element 37 embedded in a ceramic insulating base 39 constituting the main body.
- a positive electrode 31 and a negative electrode 33 are provided on both ends of the ceramic heating element 37 via metal leads 35, respectively.
- the negative electrode 33 is taken out on the outer peripheral surface of the ceramic insulating base 39 and joined and electrically connected to the inner surface of the metal outer cylinder 25 by brazing or the like.
- the positive electrode 31 is exposed to the outer surface at the rear end opposite to the front end where the ceramic heating element 37 is embedded.
- a taper is formed at the rear end portion of the ceramic insulating base 39, and a cup-shaped head portion 23a formed on the front end side of the electrode extraction fitting 23 is fitted to the rear end portion, so that the positive electrode 31 and the electrode extraction are fitted.
- the metal fitting 23 is electrically connected.
- the head portion 23a of the electrode extraction fitting 23 and the rear end portion of the ceramic insulating base 39 are joined by brazing or the like.
- a coil portion 23b is formed on the rear end side of the electrode extraction fitting 23, and a distal end portion of an electrode extraction rod 27 made of a conductive metal rigid body is inserted into and electrically connected to the coil portion 23b.
- the rear end portion of the electrode extraction rod 27 is welded and electrically connected to the front end portion of the external connection terminal 15.
- the protective member 13 is disposed around the joint portion between the electrode lead-out rod 27 and the external connection terminal 15, and the joint state is firmly held.
- the ceramic heater 21 is joined in the metal outer cylinder 25 by brazing or the like.
- the metal outer cylinder 25 has a small-diameter portion 25a on the front end side to which the ceramic heater 21 is fixed, and a large-diameter portion 25b on the rear end side in which the electrode extraction fitting 23 and the electrode extraction rod 27 are mainly disposed.
- An electrode extraction fitting 23 and an electrode extraction rod 27 that are electrically connected to the positive electrode 31 of the ceramic heater 21 enclose an insulating mixed powder 29 in a metal outer cylinder 25 so that the large diameter portion 25b
- the metal outer cylinder 25 is fixed by swaging.
- the ceramic heater assembly 20 configured as described above is press-fitted and fixed in a cylindrical housing 11 which is a mounting bracket to a cylinder head of an engine (not shown).
- the insulator mixed powder 29 sealed in the metal outer cylinder 25 not only has a function of ensuring electrical insulation between the metal outer cylinder 25 and the electrode extraction fitting 23 and the electrode extraction rod 27 but also the electrode extraction rod 27. A function of fixing, and a function of reinforcing the metal outer cylinder 25 from the inside against the compressive force that the metal outer cylinder 25 receives from the housing 11 when the ceramic heater assembly 20 is press-fitted into the housing 11. Yes.
- the glow plug 10 having such a structure can reduce the size of the ceramic heater 21 and can be produced at a low cost as a welding point is not required.
- FIGS. 2A to 2E show a manufacturing process of the ceramic heater assembly 20 provided in the glow plug 10.
- the “front end side” indicates the right side of the drawing
- the “rear end side” indicates the left side of the drawing.
- the electrode is placed on the small diameter portion 25a on the front end side of the metal outer cylinder 25
- the rear end side of the extraction fitting 23 and the ceramic heater 21 is inserted and fixed by brazing or the like.
- the electrode extraction rod 27 is inserted into the large-diameter portion 25 b on the rear end side of the metal outer cylinder 25, and the tip portion is inserted into the coil portion 23 b of the electrode extraction fitting 23. To do.
- the electrode A seal ring 19 is inserted from the rear end side of the extraction rod 27 to seal the gap between the metal outer cylinder 25 and the electrode extraction rod 27. Thereby, the insulator mixed powder 29 is enclosed, and electrical insulation between the metal outer cylinder 25 and the electrode extraction rod 27 is ensured.
- the insulator mixed powder 29 enclosed in the metal outer cylinder 25 in the glow plug 10 according to the present embodiment will be described.
- the insulator mixed powder 29 firmly fixes the electrode extraction rod 27 and the electrode extraction fitting 23, and the electrode extraction fitting 23 and the ceramic heater 21, as well as the metal outer cylinder 25, the electrode extraction rod 27, and the electrode extraction fitting 23. It has a function to ensure electrical insulation. Further, the insulator mixed powder 29 has a function of conducting and dissipating heat generated when a large current flows through the electrode extraction fitting 23 during the operation of the ceramic heater 21 to the metal outer cylinder 25 and the housing 11. Yes.
- the insulator mixed powder 29 used in the present embodiment is prepared by mixing magnesia (MgO) powder as the heat-resistant insulator particles 29a and boron nitride (BN) powder as the lubricity improving material 29b. It has become. That is, by mixing boron nitride with magnesia, which has been conventionally used as an insulator powder, the lubricity is improved while maintaining heat resistance, electrical insulation and thermal conductivity.
- MgO magnesia
- BN boron nitride
- FIGS. 3A to 3B are schematic diagrams for explaining the difference in the way stress is transmitted due to the improved lubricity of the insulator powder.
- FIG. 3 (a) shows the state of stress transmission of the insulator powder 29 'consisting only of the heat-resistant insulator particles 29a not mixed with the lubricity improver
- FIG. 3 (b) shows the heat-resistant insulator particles 29a and The state of stress transmission of the insulator mixed powder 29 mixed with the lubricity improving material 29b is shown.
- the insulator powder 29 ' is composed only of the heat-resistant insulator particles 29a, the insulator powder 29' is less likely to slip between the heat-resistant insulator particles 29a.
- the stress is easily transmitted directly to the member 50 via the heat-resistant insulating particles 29a.
- FIG. 4 shows that when the insulator mixed powder 29 mixed with the lubricity improving material 29b is filled in the metal outer cylinder 25 and swaging is performed, the rear end portion of the ceramic heater 21 and the electrode extraction fitting 23 are shown. It is the figure which showed typically the stress distribution applied to the connection part with the head part 23a.
- the heat-resistant insulator particles 29a constituting the insulator mixed powder 29 can be suitably used as long as the powder is excellent in heat resistance, electrical insulation, and thermal conductivity.
- the heat-resistant insulator particles 29a may be a material conventionally used as an insulator powder.
- magnesia powder made of fine powder having primary particles of 5 ⁇ m or less, having a particle size of 30 to 200 ⁇ m and an average particle size of about 75 ⁇ m is used.
- the lubricity improving material 29b is required to be a material having particularly excellent lubricity, but is required to have electrical insulation and thermal conductivity as the insulator mixed powder 29, and a glow attached to the engine. Heat resistance up to about 500 ° C. that can withstand the use conditions as a plug is required. Any powder satisfying such conditions can be preferably used, but hexagonal boron nitride (h-BC) is more preferred because of its excellent stability in the air and easy handling. Since hexagonal boron nitride is bonded by van der Waals having a weak bonding force, slipping easily occurs between the layers forming the crystal structure, and is a material having solid lubricity.
- h-BC hexagonal boron nitride
- the average particle diameter of the lubricity improving material 29b is preferably smaller than the average particle diameter of the heat-resistant insulator particles 29a.
- the lubricity improving material 29b that satisfies this condition, it becomes easy to interpose the lubricity improving material 29b in the gap between the heat resistant insulator particles 29a.
- the thermal conductivity of the lubricity improving material 29b is larger than the thermal conductivity of the heat-resistant insulator particles 29a.
- the relative permittivity of the lubricity improving material 29b is smaller than the relative permittivity of the heat-resistant insulator particles 29a.
- the mixing ratio of the heat-resistant insulating particles 29a and the lubricity improving material 29b so that the tapping density of the insulating mixed powder 29 is maximized.
- the filling density of the insulating mixed powder 29 can be maximized, and the electrode extraction fitting 23 and the electrode extraction rod 27 can be removed. While being able to hold
- “Tapping density” is defined as the density measured according to JIS-Z-2504 (metal powder), JIS-K-5101 (pigment powder), and JIS-R-6126 (artificial abrasive). Can do.
- the glow plug 10 according to the present embodiment described above is a mixture of the heat-resistant insulating particles 29a and the lubricity improving material 29b as the insulating powder sealed in the metal outer cylinder 25. Insulator mixed powder 29 is used. Therefore, even when the metal outer cylinder 25 is reduced in diameter and stress is applied to the inside of the metal outer cylinder 25 when swaging is performed at the time of manufacture, the space between the heat-resistant insulator particles 29a. As a result of this slippage, the uneven load distribution in the metal outer cylinder 25 can be relaxed, and the stress propagated to the connection portion 30 between the electrode extraction fitting 23 and the ceramic heater 21 can be relaxed. This effect can also be obtained when the metal outer cylinder 25 is deformed such that stress is applied to the metal outer cylinder 25 regardless of the swaging process. Therefore, damage to the ceramic heater 21 and the electrode extraction fitting 23 can be reduced.
- the same insulator mixed powder 29 is enclosed throughout the metal outer cylinder 25. Therefore, the insulator powder filled around the connecting portion 30 between the electrode extraction fitting 23 and the rear end portion of the ceramic heater 21 is made different from the insulator powder filled in other regions, and is divided into two steps. There is no need to fill with powder. Therefore, according to the glow plug 10 according to the present embodiment, the glow plug 10 in which the possibility of damaging the ceramic heater 21 or the electrode extraction fitting 23 due to the stress generated by the deformation of the metal outer cylinder 25 is efficiently produced. can do.
- the glow plug 10 according to the present embodiment described above shows one aspect of the present invention and does not limit the present invention, and each embodiment is arbitrarily changed within the scope of the present invention. It is possible.
- the glow plug 10 according to the present embodiment can be modified as follows, for example.
- Each component which comprises the glow plug 10 demonstrated in this Embodiment is an example to the last, Comprising: It can change arbitrarily.
- the glow plug 10 according to this embodiment is configured so that the positive electrode is taken out by the electrode take-out fitting 23 and the electrode take-out rod 27. It is not limited.
- the positive electrode 31 of the ceramic heater 21 and the external connection terminal 15 may be connected by a single wire.
- the glow plug 10 encloses the same insulator mixed powder 29 throughout the inside of the metal outer cylinder 25, but at least the positive electrode 31 of the ceramic heater 21.
- the insulator mixed powder 29 mixed with the lubricity improving material 29b may be filled only on the tip side where the connection part 30 between the electrode extraction fitting 23 and the head part 23a is located. That is, the process of filling the insulator powder in the metal outer cylinder 25 is divided into two processes, and after first filling the insulator mixed powder 29 mixed with the lubricity improving material 29b, the heat resistant insulator particles 29a such as magnesia are filled. You may make it fill only. Even in such a configuration, it is possible to suppress the stress generated during the swaging process from propagating to the connection portion 30 between the positive electrode 31 of the ceramic heater 21 and the head portion 23a of the electrode extraction fitting 23. it can.
- an insulator mixed powder was prepared using magnesia (MgO) and hexagonal boron nitride (h-BN) shown in Table 1.
- Tapping density Insulation in which the total weight of the insulator mixed powder is 100% by weight, and the mixed amount of hexagonal boron nitride is 0% by weight, 5% by weight, 10% by weight, 13% by weight and 15% by weight, respectively.
- the body mixed powder was prepared, and the tapping density (g / ccm) of the insulator mixed powder was measured.
- 10 ccm of the insulator mixed powder was put into the graduated cylinder, and the volume after tapping 180 times manually was measured.
- FIG. 5 shows the result of measuring the tapping density (g / ccm) with respect to the mixing amount (% by weight) of hexagonal boron nitride.
- the tapping density was maximized when the mixed amount of hexagonal boron nitride was about 10% by weight. Therefore, it is understood that when the mixing amount of the hexagonal boron nitride is about 10% by weight, the electrode extraction fitting, the electrode extraction rod, and the connection portion thereof can be held more firmly by performing swaging. it can.
- the basic configuration of the ceramic heater assembly is as shown in FIG. 2, but in this embodiment, as shown in FIG. 6, in order to make it easier to determine the degree of damage to the electrode extraction fitting and ceramic heater due to swaging. Further, a small-diameter portion 39A is formed at the rear end of the ceramic heater 21A, and the head portion 23Aa of the electrode extraction fitting 23A is formed in a cylindrical shape to be fitted with the small-diameter portion 39A.
- the manufactured ceramic heater assembly was energized, and the resistance value of each ceramic heater assembly was measured.
- the resistance value was measured using a milliohm tester based on the four probe method.
- FIG. 7 shows the measurement results. As shown in FIG. 7, when using a magnesia-only insulator powder in which the mixing amount of hexagonal boron nitride is 0% by weight, a high resistance value is detected, while hexagonal boron nitride is mixed. When the insulator mixed powder was used, the resistance value was low and stable, and it was confirmed that the resistance value could be maintained.
- each ceramic heater assembly is extracted for each mixing amount of hexagonal boron nitride, and each ceramic heater assembly is energized to a position 2 mm from the tip.
- the power consumption of the ceramic heater was measured at temperatures of 1,100 ° C., 1,200 ° C., and 1,300 ° C., respectively.
- FIG. 9 shows the measurement results. As shown in FIG. 9, even when hexagonal boron nitride is mixed, the power consumption of the ceramic heater does not increase. There was also a tendency for power consumption to decrease.
- thermal conductivity of hexagonal boron nitride is higher than that of magnesia, and a glow plug is manufactured using the insulator mixed powder 29 mixed with hexagonal boron nitride. In this case, it can be understood that the thermal conductivity is higher than that when only magnesia is filled.
- the ceramic heater assembly 20A manufactured by enclosing the insulator mixed powder 29 mixed with hexagonal boron nitride in the metal outer cylinder 25 the heat resistance and heat of the insulator mixed powder 29 are increased. It is possible to firmly hold the electrode extraction fitting 23, the electrode extraction rod 27, and their connection parts without affecting the heater resistance, the surface temperature and the power consumption while improving the conductivity and electrical insulation.
- the ceramic heater assembly 20A can be obtained.
- the ceramic heater assembly 20A produced by sealing the insulator mixed powder 29 mixed with hexagonal boron nitride in the metal outer cylinder 25 is provided with lubricity to the insulator mixed powder 29. Even when swaging was performed, breakage of the rear end portion 39A of the ceramic heater 21A and the electrode extraction fitting 23A could be suppressed.
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Abstract
Description
なお、それぞれの図中において同じ符号が付されているものは、特に説明がない限り同一の構成要素を示しており、適宜説明が省略されている。
1.グロープラグの基本的構成
図1は、本発明の第1の実施の形態にかかるディーゼルエンジン用グロープラグ10の断面図である。
図1に示すグロープラグ10は、セラミックスヒータアセンブリ20を備えたセラミックスヒータ型グロープラグとして構成されている。セラミックスヒータアセンブリ20は、セラミックスヒータ21と、電極取出金具23と、電極取出ロッド27と、金属製外筒(シース)25等を主な構成要素として備えている。
図2(a)~(e)は、グロープラグ10に備えられるセラミックスヒータアセンブリ20の製造工程を示している。なお、図2(a)~(e)についての説明中、「先端側」は図の右側を指し、「後端側」は図の左側を指している。
次に、本実施の形態にかかるグロープラグ10において、金属製外筒25内に封入される絶縁体混合粉末29について説明する。
絶縁体混合粉末29は、電極取出ロッド27と電極取出金具23、及び、電極取出金具23とセラミックスヒータ21を強固に固定するとともに、金属製外筒25と電極取出ロッド27及び電極取出金具23との電気絶縁性を確保する機能を有している。また、絶縁体混合粉末29は、セラミックスヒータ21の動作時において、大電流が電極取出金具23に流れるときに発生する熱を金属製外筒25及びハウジング11に伝導させ散逸させる機能を有している。
以上説明した本実施の形態にかかるグロープラグ10は、金属製外筒25内に封入される絶縁体粉末として、耐熱絶縁体粒子29aと潤滑性向上材29bとを混合した絶縁体混合粉末29を用いることとしている。そのため、製造時においてスエージング加工を施した際に、金属製外筒25が細径化されて金属製外筒25の内部に応力が負荷された場合であっても、耐熱絶縁体粒子29a間のすべりが生じることで金属製外筒25内の偏加重分布を緩和して、電極取出金具23とセラミックスヒータ21の後端部との接続部30に伝播される応力を緩和させることができる。この効果は、スエージング加工時にかかわらず、金属製外筒25内に応力が負荷されるような金属製外筒25の変形が生じた場合にも得ることができる。したがって、セラミックスヒータ21及び電極取出金具23の破損を低減することができる。
以上説明した本実施の形態にかかるグロープラグ10は、本発明の一態様を示すものであってこの発明を限定するものではなく、それぞれの実施の形態は本発明の範囲内で任意に変更することが可能である。本実施の形態にかかるグロープラグ10は、例えば、以下のように変更することができる。
絶縁体混合粉末の総重量を100重量%として、六方晶系窒化ホウ素の混合量がそれぞれ0重量%、5重量%、10重量%、13重量%、15重量%である絶縁体混合粉末を作製し、絶縁体混合粉末のタッピング密度(g/ccm)を測定した。
タッピング密度は、メスシリンダー内に絶縁体混合粉末を10ccm投入するとともに、手作業にて180回タッピングした後の体積を測定した。
図5に示すように、表1に示すマグネシア及び六方晶系窒化ホウ素を用いた場合には、六方晶系窒化ホウ素の混合量が約10重量%のときにタッピング密度が最大となった。したがって、六方晶系窒化ホウ素の混合量を約10重量%とした場合には、スエージング加工を施すことによって、電極取出金具、電極取出ロッド、及びそれらの接続部をより強固に保持できることが理解できる。
次に、上述のとおりに作製した絶縁体混合粉末のうち、六方晶系窒化ホウ素の混合量が0重量%、10重量%、15重量%の絶縁体混合粉末を用いて、図2(a)~(e)に示す手順に沿ってセラミックスヒータアセンブリを作製した。すなわち、金属製外筒25内の全体にわたって同じ絶縁体混合粉末29を封入したセラミックスヒータアセンブリを作製した。六方晶系窒化ホウ素の混合量が異なる絶縁体混合粉末ごとに3つのセラミックスヒータアセンブリを作製した。
図7に示すように、六方晶系窒化ホウ素の混合量が0重量%であるマグネシアのみの絶縁体粉末を用いた場合には高い抵抗値が検出される一方、六方晶系窒化ホウ素を混合した絶縁体混合粉末を用いた場合には抵抗値が低く安定しており、抵抗値を維持できることが確認された。
次に、作製したセラミックスヒータアセンブリのうち、六方晶系窒化ホウ素の混合量ごとに1個のセラミックスヒータアセンブリを抜き出し、それぞれのセラミックスヒータアセンブリに通電した時のセラミックスヒータの表面温度を測定した。表面温度は、セラミックスヒータの先端から1mmごとに、放射温度計を用いて測定した。図8に測定結果を示す。
図8に示すように、六方晶系窒化ホウ素を混合した場合であっても、セラミックスヒータの表面温度にはほとんど影響がなかった。
次に、作製したセラミックスヒータアセンブリのうち、六方晶系窒化ホウ素の混合量ごとに1個のセラミックスヒータアセンブリを抜き出し、それぞれのセラミックスヒータアセンブリに通電して、先端から2mmの位置の温度が1,100℃、1,200℃、1,300℃それぞれのときのセラミックスヒータの消費電力を測定した。図9に測定結果を示す。
図9に示すように、六方晶系窒化ホウ素を混合した場合であっても、セラミックスヒータの消費電力が増大することはなく、六方晶系窒化ホウ素の混合量が多いほど、同じ温度であっても消費電力が小さくなる傾向が見られた。
表1に示すように、用いた六方晶系窒化ホウ素の大気中における耐熱温度はマグネシアと比較して低くなっているものの、グロープラグの使用時においても金属製外筒25内は500℃以上になる場合が無いことが確認されているため、耐熱性は確保される。
また、六方晶系窒化ホウ素の熱伝導率はマグネシアに比べても高い値を示しており、六方晶系窒化ホウ素を混合した絶縁体混合粉末29を用いてグロープラグを製造した場合には、マグネシアのみを充填した場合よりも高い熱伝導率を示すことが理解できる。
また、六方晶系窒化ホウ素の比誘電率はマグネシアに比べて小さい値を示しており、六方晶系窒化ホウ素を混合した絶縁体混合粉末29を用いてグロープラグを製造した場合には、マグネシアを充填した場合よりも電気絶縁性に優れていることが理解できる。
Claims (6)
- セラミックスヒータと、前記セラミックスヒータが一端側に保持されるとともに、他端側がハウジングの内部孔に挿入されて固定された金属製外筒と、前記金属製外筒内で前記セラミックスヒータの一方の電極に接続された電極取出部材と、を備え、
前記金属製外筒内に封止材として耐熱絶縁体粒子を封入したセラミックスヒータ型グロープラグにおいて、
少なくとも前記一方の電極と前記電極取出部材との接続部の周囲に、前記耐熱絶縁体粒子間の潤滑性を向上させるための潤滑性向上材を混合した絶縁体混合粉末を充填したことを特徴とするセラミックスヒータ型グロープラグ。 - 前記潤滑性向上材の平均粒径が前記耐熱絶縁体粒子の平均粒径よりも小さいことを特徴とする請求項1に記載のセラミックスヒータ型グロープラグ。
- 前記潤滑性向上材の熱伝導率が前記耐熱絶縁体粒子の熱伝導率よりも大きいことを特徴とする請求項1又は2に記載のセラミックスヒータ型グロープラグ。
- 前記絶縁体混合粉末のタッピング密度が、前記耐熱絶縁体粒子のタッピング密度よりも大きくなるように、前記耐熱絶縁体粒子と前記潤滑性向上材との混合比率を決定することを特徴とする請求項1~3のいずれか一項に記載のセラミックスヒータ型グロープラグ。
- 前記耐熱絶縁体粒子がマグネシア(MgO)であり、前記潤滑性向上材が六方晶系窒化ホウ素(h-BN)であることを特徴とする請求項1~4のいずれか一項に記載のセラミックスヒータ型グロープラグ。
- 前記金属製外筒内の全体に前記絶縁体混合粉末を封入することを特徴とする請求項1~5のいずれか一項に記載のセラミックスヒータ型グロープラグ。
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EP12804732.1A EP2700876B1 (en) | 2011-06-29 | 2012-04-04 | Ceramic-heater-type glow plug |
US14/129,870 US20140138373A1 (en) | 2011-06-29 | 2012-04-04 | Ceramic heater-type glow plug |
JP2013522495A JP5612208B2 (ja) | 2011-06-29 | 2012-04-04 | セラミックスヒータ型グロープラグ |
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JP2021021518A (ja) * | 2019-07-25 | 2021-02-18 | ボッシュ株式会社 | セラミックスヒータ型グロープラグおよびその製造方法 |
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KR20140142934A (ko) * | 2013-06-05 | 2014-12-15 | 우진공업주식회사 | 디젤 엔진용 글로우 플러그의 금구 및 그 제조 방법 |
DE102014220036A1 (de) * | 2014-10-02 | 2016-04-07 | Robert Bosch Gmbh | Glühstiftkerze |
JP6370663B2 (ja) * | 2014-10-09 | 2018-08-08 | 日本特殊陶業株式会社 | グロープラグ |
DE102016114929B4 (de) * | 2016-08-11 | 2018-05-09 | Borgwarner Ludwigsburg Gmbh | Druckmessglühkerze |
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