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US20040222207A1 - Glow plug - Google Patents

Glow plug Download PDF

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Publication number
US20040222207A1
US20040222207A1 US10/828,169 US82816904A US2004222207A1 US 20040222207 A1 US20040222207 A1 US 20040222207A1 US 82816904 A US82816904 A US 82816904A US 2004222207 A1 US2004222207 A1 US 2004222207A1
Authority
US
United States
Prior art keywords
metallic tube
insulator
coil member
glow plug
insulating powder
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.)
Abandoned
Application number
US10/828,169
Other languages
English (en)
Inventor
Chiaki Kumada
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.)
Niterra Co Ltd
Original Assignee
NGK Spark Plug 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
Application filed by NGK Spark Plug Co Ltd filed Critical NGK Spark Plug Co Ltd
Assigned to NGK SPARK PLUG CO., LTD. reassignment NGK SPARK PLUG CO., LTD. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: KUMADA, CHIAKI
Publication of US20040222207A1 publication Critical patent/US20040222207A1/en
Abandoned legal-status Critical Current

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Classifications

    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23QIGNITION; EXTINGUISHING-DEVICES
    • F23Q7/00Incandescent ignition; Igniters using electrically-produced heat, e.g. lighters for cigarettes; Electrically-heated glowing plugs
    • F23Q7/001Glowing plugs for internal-combustion engines

Definitions

  • the present invention relates to a glow plug for preheating the interior of a cylinder of a diesel engine, as well as to a glow plug for preheating water.
  • a conventional glow plug includes a metallic tube having a closed distal end and extending axially; a rod-like insulator disposed within the metallic tube so as to form a clearance therebetween; a coil member disposed so as to encircle an outer circumferential surface of the insulator; and insulating powder charged into the metallic tube so as to fill the interior of the metallic tube.
  • the rod-like insulator is inserted into an internal space of the coil member. This prevents contact between the coil member and the metallic tube, which could otherwise result from bending of the coil member in the process of drawing the metallic tube. This also prevents variation in heating characteristics. among glow plugs, which could otherwise result from the occurrence of uneven pitch spacings between turns of the coil member. Also, when only insulating powder is used as a filler for the metallic tube, voids are formed between powder particles even after drawing. Insertion of the rod-like insulator lessens a space into which the insulating powder is charged, so as to enhance the effect of charging through reduction of void space.
  • the present invention has been accomplished in view of the above described problems of the prior art, and an object of the invention is to provide a glow plug in which heat generated by the coil member is effectively conducted to the metallic tube.
  • the present invention provides a glow plug comprising a metallic tube having a closed distal end and extending axially, a rod-like insulator disposed within the metallic tube so as to form a clearance between the insulator and the metallic tube, a coil member encircling an outer circumferential surface of the insulator, and insulating powder charged into the metallic tube which fills the interior of the metallic tube, wherein the insulator is formed of an insulating material having a thermal conductivity that is lower than that of the insulating powder.
  • the insulator to be inserted into the coil member is formed of an insulating material having a thermal conductivity that is lower than that of the insulating powder, which insulating powder is charged to fill the interior of the metallic tube.
  • a glow plug is maintained at a predetermined temperature.
  • a predetermined current must be continuously supplied to a coil member.
  • the coil member is susceptible to breakage.
  • the glow plug of the present invention is configured such that the insulator inserted into the coil member is formed of an insulating material having a thermal conductivity that is lower than that of the insulating powder, heat generated by the coil member is effectively conducted to the metallic tube. Consequently, the heat that the coil member must generate in order to maintain the glow plug at a predetermined temperature can be reduced as compared to a conventional glow plug. As a result, the predetermined current that needs to be supplied to the coil member decreases, whereby the durability of the coil member is enhanced.
  • the glow plug of the present invention is configured such that A ⁇ 0.6B, where A is the diameter of the insulator, and B is the inside diameter of the coil member.
  • A is the diameter of the insulator
  • B is the inside diameter of the coil member.
  • the glow plug of the present invention is configured such that the insulating powder comprises magnesium oxide, and the insulating material comprises alumina.
  • the insulating powder is magnesium oxide and the insulating material is alumina, heat can be more effectively conducted from the coil member to the metallic tube.
  • a further aspect of the present invention provides a glow plug comprising a metallic tube having a closed distal end and extending axially, a rod-like insulator formed of an insulating material and disposed within the metallic tube so as to form a clearance therebetween, a coil member disposed so as to encircle an outer circumferential surface of the insulator, and insulating powder charged into the metallic tube so as to fill the interior of the metallic tube, wherein, as viewed on a cross section taken perpendicularly to an axis, the insulating powder present in a clearance between the metallic tube and the coil member has a greater occupancy rate per unit area than the insulating material in the insulator.
  • the glow plug in this aspect of the present invention is configured such that the occupancy rate of the insulating powder in the clearance between the metallic tube and the coil member is greater than that of the insulating material in the insulator. Since void space in a region of the clearance between the metallic tube and the coil member becomes less than that in the insulator, the thermal conductivity of the insulating powder can be rendered higher than that of the insulator, so that heat generated by the coil member can be effectively conducted to the metallic tube. Notably, the occupancy rate is measured per unit area on a cross section taken perpendicularly to the axis of the glow plug.
  • the glow plug of the present invention is configured such that the occupancy rate of the insulating powder present in the clearance between the metallic tube and the coil member is greater than that of the insulating material in the insulator, heat generated by the coil member is effectively conducted to the metallic tube, so that the heat that the coil member must generate to maintain a predetermined temperature can be reduced as compared with a conventional glow plug. As a result, the predetermined current that needs to be supplied to the coil member decreases, whereby the durability of the coil member is enhanced.
  • the glow plug of the present invention is configured such that the insulating powder has an average particle size that is smaller than that of the insulating material. This feature enables the insulating powder present in the clearance between the metallic tube and the coil member to have an occupancy rate greater than that of the insulating material in the insulator, so that heat generated by the coil member can be effectively conducted to the metallic tube.
  • the insulating material has a thermal conductivity lower than that of the insulating powder.
  • the thermal conductivity within the coil member lower than the thermal conductivity in a region between the coil member and the metallic tube, conduction of heat generated by the coil member to the metallic tube increases, so that heat is effectively conducted to the metallic tube.
  • the glow plug can more effectively serve as a heat source.
  • FIG. 1 is a vertical sectional view of a glow plug 1 according to an embodiment of the present invention.
  • FIG. 2 is an enlarged sectional view of a distal end portion of the glow plug according to an embodiment of the present invention.
  • Embodiment 1 of the present invention will next be described in detail with reference to the drawings. However, the present invention should not be construed as being limited thereto.
  • FIG. 1 shows the internal structure of a glow plug 1 , which is an example of the present invention
  • FIG. 2 is an enlarged view showing the internal structure of a distal end portion of the glow plug 1
  • the glow plug 1 includes a tubular metallic shell 3 extending in the direction of an axis O; a metallic tube 2 fixedly attached to a distal end portion of the metallic shell 3 , extending in the direction of the axis O, and having a closed distal end; and center rod 4 , which serves as an electrode.
  • the metallic tube 2 is formed of stainless steel, such as SUS310S.
  • the center rod 4 extends along the axis of the metallic shell 3 and reaches the interior of the metallic tube 2 .
  • the bottom of the metallic tube 2 and a distal end portion of the center rod 4 are electrically connected together via a coil member 5 .
  • the coil member 5 consists of a front-end-side heating coil 51 , and a rear-end-side control coil 52 .
  • the heating coil 51 is formed of a material having a R20 (resistivity at 20° C. of) of 80 ⁇ cm to 200 ⁇ cm, and an R1000/R20 value of 0.8 to 3, where R1000 is resistivity at 1,000° C.
  • Specific examples of the material include an Fe—Cr—Al alloy, an Ni—Cr alloy, and an Fe-Cr alloy.
  • the control coil 52 is formed of a material having a R20 (resistivity at 20° C.
  • the center rod 4 and the heating coil 51 are indirectly connected via the control coil 52 .
  • the heating coil 51 and the center rod 4 may be directly connected together without provision of the control coil 52 .
  • Insulating powder 15 formed of magnesium oxide (magnesia) powder or the like is charged into the metallic tube 2 so as to fill the interior of the metallic tube 2 .
  • An elastic packing 16 is disposed between the metallic tube 2 and a front end portion of the center rod 4 so as to seal against the metallic tube 2 and the center rod 4 , and the elastic packing 16 closes the metallic tube 2 .
  • the insulator 14 is formed of an insulating material having a thermal conductivity lower than that of the insulating powder 15 .
  • the thermal conductivity within coil member 5 is rendered lower than the thermal conductivity in a region between the coil member 5 and the metallic tube 2 . Consequently, conduction of heat generated by the coil member 5 to the metallic tube 2 increases, and thus heat is effectively conducted to the metallic tube 2 . Therefore, the glow plug 1 can function as an efficient heat source.
  • the diameter A of the insulator 14 is substantially equal to the inside diameter B of the coil member 5 .
  • A is the diameter of the insulator 14
  • B is the inside diameter of the coil member 5 .
  • a stepped hole 7 is formed at the upper end of the metallic shell 3 .
  • a bush-like insulation ring 8 fitted into the stepped hole 7 supports an upper portion of the center rod 4 at the center of the metallic shell 3 , and electrically insulates the upper portion from the metallic shell 3 .
  • a clearance formed between the stepped hole 7 and the center rod 4 is filled with an O-ring 9 .
  • a hexagonal tool engagement portion 10 is externally formed on an upper end portion of the metallic shell 3 .
  • a male-threaded portion 11 is formed below the tool engagement portion 10 and used for connection to a diesel engine (not shown) or the like.
  • a male-threaded portion 12 is formed on an upper end portion of the center rod 4 .
  • a round nut 13 is screw-engaged with the male-threaded portion 12 and presses the insulation ring 8 .
  • the center rod 4 and a power cable are directly connected together so as to establish electrical connection therebetween.
  • a terminal electrode (not shown) connected to a power cable may be fixedly attached to the center rod 4 so as to cover a top portion of the center rod 4 .
  • the insulator 14 is inserted into the coil member 5 , which is formed by welding the control coil 52 and the heating coil 51 together.
  • a rear end portion (of the control coil 52 ) of the coil member 5 is joined to the center rod 4 by means of, for example, resistance welding.
  • the coil member 5 is inserted, from the heating coil 51 , into the metallic tube 2 .
  • a distal end portion of the heating coil 51 is joined to the distal end of the metallic tube 2 by means of, for example, arc welding.
  • the insulating powder 15 is charged into the metallic tube 2 so as to fill the interior of the metallic tube 2 .
  • the elastic packing 16 is inserted into a rear end portion of the metallic tube 2 .
  • a rear end portion of the metallic tube 2 is swaged so as to crimp the elastic packing 16 . Furthermore, the entire metallic tube 2 is subjected to swaging from its rear end side toward its distal end side so as to assume predetermined dimensions. Subsequently, the resultant assembly is inserted, from a rear end portion of the center rod 4 , into the metallic shell 3 on its distal end side. A rear end portion of the metallic tube 2 is interference-fitted; for example, press-fitted, into the metallic shell 3 . Then, a rear end portion of the metallic shell 3 is sealed with the O-ring 9 . Subsequently, the insulation ring 8 and the round nut 13 are sequentially fitted to the center rod 4 , thereby completing the glow plug 1 .
  • a glow plug 100 of embodiment 2 is similar to the above-described glow plug 1 except that the insulating powder 15 and the insulator 14 differ from each other in material and/or average particle size. Since the configuration of the glow plug 100 is identical with that of the glow plug 1 of embodiment 1, the insulating powder 15 and the insulator 14 are mainly described with reference to FIGS. 1 and 2 while identical structural features are denoted by common reference numerals.
  • the rod-like insulator 14 which is formed of an insulating material, such as magnesium oxide (magnesia), is inserted into the coil member 5 of the glow plug 100 of embodiment 2.
  • the insulating powder 15 which is formed of the same insulating material as that of the insulator 14 , such as a magnesium oxide (magnesia) powder, is charged into the metallic tube 2 so as to fill the interior of the metallic tube 2 .
  • the insulating powder 15 of the glow plug 100 has an average particle size of 75 ⁇ m, whereas the insulating material for the insulator 14 has an average particle size of 120 ⁇ m.
  • the occupancy rate of the insulating powder 15 present in the clearance between the metallic tube 2 and the coil member 5 becomes greater than that of the insulating material in the insulator 14 as observed in a cross section of the glow plug 100 taken perpendicular to the axis. Since void space in a region of the clearance between the metallic tube 2 and the coil member 5 becomes less than that in the insulator 14 , the thermal conductivity of the insulating powder 15 can be rendered higher than that of the insulator 14 . As a result, heat generated by the coil member 5 can be effectively conducted to the metallic tube 2 .
  • Samples of the glow plug 100 shown in FIG. 1 were fabricated.
  • the insulator material in Sample No. 6 and the insulating powder in Sample Nos. 6, 7 and 8 each had an occupancy rate of 96% and a particle size of 80 ⁇ m.
  • the insulator material in each of Sample Nos. 7 and 8 had an occupancy rate of 90% and a particle size of 120 ⁇ m.
  • the coil member 5 had a diameter of 0.35 mm and a length of 22 mm;
  • the metallic tube 2 had a length of 42 mm, a diameter of 4.5 mm as measured at its distal end portion and 5 mm as measured at its rear end portion, and a wall thickness of 0.75 mm; and magnesium oxide was used to form the insulator 14 and the insulating powder 15 .
  • a DC voltage of 11 V was applied to the samples, and the surface temperature of each metallic tube 2 and the generated heat were measured after an elapsed time of 60 seconds.
  • the surface temperature was the maximum temperature that the metallic tube 2 could generate; and the generated heat was calculated by measuring current and applied voltage 60 seconds after start of application of the voltage.
  • the number of voltage application cycles until the coil member 5 broke was measured, each voltage application cycle consisting of 5-minute application of 13 VDC and subsequent 1-minute suspension of voltage application.
  • Each of the samples was cut at a position located 5 mm rearward from its distal end so as to obtain a cross section at that position.
  • the present invention has been described with reference to certain embodiments, the present invention is not limited thereto, but may be embodied in various other forms without departing from the scope of the invention.
  • the above embodiments are described while mentioning the glow plug 100 ; however, the present invention may also be as a water heater for heating water.

Landscapes

  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Resistance Heating (AREA)
US10/828,169 2003-04-23 2004-04-21 Glow plug Abandoned US20040222207A1 (en)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
JP2003-118961 2003-04-23
JP2003118961 2003-04-23
JP2004010149A JP2004340562A (ja) 2003-04-23 2004-01-19 グロープラグ
JP2004-10149 2004-01-19

Publications (1)

Publication Number Publication Date
US20040222207A1 true US20040222207A1 (en) 2004-11-11

Family

ID=32964975

Family Applications (1)

Application Number Title Priority Date Filing Date
US10/828,169 Abandoned US20040222207A1 (en) 2003-04-23 2004-04-21 Glow plug

Country Status (4)

Country Link
US (1) US20040222207A1 (de)
EP (1) EP1471307B1 (de)
JP (1) JP2004340562A (de)
DE (1) DE602004004827T2 (de)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20090184101A1 (en) * 2007-12-17 2009-07-23 John Hoffman Sheathed glow plug
US20100133253A1 (en) * 2008-10-23 2010-06-03 Walker Jr William J Glow plug with improved seal, heater probe assembly therefor and method of construction thereof
US20100133252A1 (en) * 2007-03-08 2010-06-03 Haruhiko Abe Glow plug and method for manufacturing the same
US20100200392A1 (en) * 2007-06-01 2010-08-12 Microvast, Inc. Photodegradation Catalyst and Photodegradation Catalyst Precursor Comprising Metal Halide or Metal Oxyhalide
US20110023598A1 (en) * 2008-02-26 2011-02-03 Areva Np Gmbh Electrical heating element and method of measuring a filling level
US9702556B2 (en) 2012-04-16 2017-07-11 Ngk Spark Plug Co., Ltd. Glow plug
EP3208539A1 (de) * 2016-02-16 2017-08-23 NGK Spark Plug Co., Ltd. Glühkerze

Families Citing this family (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1717515A1 (de) * 2005-04-28 2006-11-02 Siemens Aktiengesellschaft Anschluss einer Verbrennungsanlage
JP4871193B2 (ja) * 2007-04-13 2012-02-08 日本特殊陶業株式会社 グロープラグ及びその製造方法
JP5319925B2 (ja) * 2008-01-15 2013-10-16 日本特殊陶業株式会社 グロープラグの製造方法
JP5639227B2 (ja) * 2013-06-13 2014-12-10 日本特殊陶業株式会社 グロープラグ
DE102014225908A1 (de) 2014-12-15 2016-06-16 Robert Bosch Gmbh Glühstiftkerze
JP6525616B2 (ja) * 2015-02-03 2019-06-05 日本特殊陶業株式会社 グロープラグ
JP2019045109A (ja) * 2017-09-06 2019-03-22 日本特殊陶業株式会社 グロープラグ

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4200077A (en) * 1977-10-15 1980-04-29 Robert Bosch Gmbh Glow plug structure
US4476378A (en) * 1981-04-30 1984-10-09 Jidosha Kiki Co., Ltd. Glow plug for use in diesel engine
US5304778A (en) * 1992-11-23 1994-04-19 Electrofuel Manufacturing Co. Glow plug with improved composite sintered silicon nitride ceramic heater

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB859659A (en) * 1958-06-07 1961-01-25 Bosch Gmbh Robert Improvements in glow plugs for internal combustion engines
JPS5758017A (en) * 1980-09-23 1982-04-07 Ngk Spark Plug Co Ltd Sheathed glow plug

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4200077A (en) * 1977-10-15 1980-04-29 Robert Bosch Gmbh Glow plug structure
US4476378A (en) * 1981-04-30 1984-10-09 Jidosha Kiki Co., Ltd. Glow plug for use in diesel engine
US5304778A (en) * 1992-11-23 1994-04-19 Electrofuel Manufacturing Co. Glow plug with improved composite sintered silicon nitride ceramic heater

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20100133252A1 (en) * 2007-03-08 2010-06-03 Haruhiko Abe Glow plug and method for manufacturing the same
US8399807B2 (en) * 2007-03-08 2013-03-19 Ngk Spark Plug Co., Ltd. Glow plug and method for manufacturing the same
US20100200392A1 (en) * 2007-06-01 2010-08-12 Microvast, Inc. Photodegradation Catalyst and Photodegradation Catalyst Precursor Comprising Metal Halide or Metal Oxyhalide
US20090184101A1 (en) * 2007-12-17 2009-07-23 John Hoffman Sheathed glow plug
US20110023598A1 (en) * 2008-02-26 2011-02-03 Areva Np Gmbh Electrical heating element and method of measuring a filling level
US8739621B2 (en) 2008-02-26 2014-06-03 Areva Gmbh Electrical heating element and method of measuring a filling level
US20100133253A1 (en) * 2008-10-23 2010-06-03 Walker Jr William J Glow plug with improved seal, heater probe assembly therefor and method of construction thereof
US8410403B2 (en) 2008-10-23 2013-04-02 Federal Mogul Ignition Company Glow plug with improved seal, heater probe assembly therefor and method of construction thereof
US9702556B2 (en) 2012-04-16 2017-07-11 Ngk Spark Plug Co., Ltd. Glow plug
EP3208539A1 (de) * 2016-02-16 2017-08-23 NGK Spark Plug Co., Ltd. Glühkerze

Also Published As

Publication number Publication date
EP1471307A1 (de) 2004-10-27
JP2004340562A (ja) 2004-12-02
DE602004004827T2 (de) 2007-10-31
DE602004004827D1 (de) 2007-04-05
EP1471307B1 (de) 2007-02-21

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Legal Events

Date Code Title Description
AS Assignment

Owner name: NGK SPARK PLUG CO., LTD., JAPAN

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:KUMADA, CHIAKI;REEL/FRAME:015563/0026

Effective date: 20040506

STCB Information on status: application discontinuation

Free format text: ABANDONED -- FAILURE TO RESPOND TO AN OFFICE ACTION