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 preheating spark plug with either ceramic or metal tube cartridge
• a preheating spark plug with either ceramic or metal tube cartridge comprising a tubular metal body provided with a thread for screwing into the engine cylinder head and carrying the heating element in the cartridge, the body being traversed by a central electrode connected to a terminal of the heating element whose other terminal is connected to the body making the connection to ground, the body carrying at its other end a primary connector receiving the connector of the manufacturer.
• This primary connector installed on the electrode is connected to it by being isolated from the body by an electrical insulation ring.
• the invention also relates to a method of manufacturing such a glow plug.
• the glow plug 200 is composed at the front, not shown, of a body provided with a heated front end, for example ceramic, containing a heating electric filament of which a connection is connected to the tubular body 210, conductive, him -even connected to the mass by its screwing (thread 212) in the motor and whose other connection is connected to a central electrode 220 through the bore 211 of the tubular body 210 while being isolated therefrom, to be connected its other end to the primary connector 240 itself receiving the connector of the manufacturer to thereby supply the heating element.
• the rear end of the central electrode 220 is provided with a knurled portion 221 and is housed in the blind hole 241 of the primary connector 240 to be fixed by the crimping 250.
• the rear end 213, which externally forms a tool socket for screwing the spark plug, has, at the outlet of the bore 21 1, a bearing cone 214 and a countersink 215 for receiving a gasket. sealing 230 and an insulating washer 235 both engaged on the central electrode 220 and thus separating it from the contact with the body 210 when these seals 230, 235 are compressed both against each other and against the bearing cone 214 and countersink 215.
• the primary connector 240 engaged on the end of the central electrode 220 is pressed towards the rear portion 213 of the body 210 is crimped 250 ( Figure 1B) against the knurling 221 .
• the very large temperature variations experienced by the glow plug 200 cause significant length variations of the components such as the central electrode 220 and the tubular body 210. These variations in the length of the central electrode 220 are much greater than those of the tubular body 210.
• the insulating washer 235 does not remain in contact with the countersink 215 of the tubular body 210 and the seal between the inside of the bore 21 1 and the external environment may be broken.
• the seal 230 which is a flexible, toric seal is interposed between the tubular body 210 and the insulating washer 235.
• the seal 230 is oversized at rest and is set permanent compression by the insulating washer 235 and the connector 240.
• the connector 240 is held in position on the central electrode 220 by its crimping 250 on the knurling 221.
• the seal being provided by the elasticity. This sealing is done on the three areas of contact of the seal with the support cone 214, the central electrode 220 and the front surface of the insulating washer 235.
• the seal undergoes an extension of its diameter during its passage on the knurling 221 of the central electrode 220.
• the outer diameter of the knurling 221 is indeed greater to the diameter of the smooth portion of the central electrode 220. This passage is made possible by the elasticity of the O-ring 230. Then put in compression by the thrust exerted by the end with the support flange 242 of the connector 240 on the isolation washer 235 which rests on the seal 230. This compression of the components is ensured permanently thanks to the crimping 250 of the connector 240 on the knurling 221 of the central electrode 220.
• the present invention aims to simplify the manufacture of the glow plug and improve its reliability and efficiency by reducing the number of components.
• the subject of the present invention is a glow plug of the type defined above, characterized in that the rear end of the body terminates in a bearing surface into which the bore opens, the central electrode comprises a knurling whose outer diameter is smaller than the diameter of the smooth portion of the central electrode, the seal is formed of a sleeve having a collar, the sleeve has a thickness greater than the size of the gap between the smooth surface of the the central electrode and the bore, this sleeve being inserted by force into the gap and the flange coming to bear against the bearing face of the rear part and the bearing flange of the connector, and the internal diameter of the sleeve is greater than the outside diameter of the knurling.
• the glow plug according to the invention achieves the sealing of the cavity through the seal whose sleeve which seals despite the relative movements between the body of the candle and the central electrode under the effect of temperature changes.
• the realization of the candle is simple since it sets up a single seal.
• the bearing surface of the rear end of the body comprises a counterbore receiving the collar of the seal.
• the collar of the seal can bear directly against the bearing surface of the rear part but preferably, this bearing surface comprises a counterbore so that a portion of the collar is locked in the counterbore leaving a portion of the thickness of the collar to protrude to allow support of the flange of the connector which ensures the tightening of the assembly.
• the seal is made of polyamide, in particular of PA6 / 6 copolymer of caprolactam PA6.
• This seal has the advantage of withstanding the temperature variations and aggressive agents to which it may be exposed during operation of the engine.
• Figure 1A is an axial sectional view of the rear end of a glow plug according to the invention after crimping.
• FIG. 2A is a view in axial section analogous to that of FIG. 1A but with the connector and the joint disassembled,
• FIG. 3A shows an axial sectional view showing the assembly of the rear end of the candle before crimping
• Figures 1B, 2B, 3B are sectional views of the rear end of a known glow plug, presented under the same conditions as the glow plug of the invention and highlighting the differences between the two candles.
• the drawings show only the rear end of the glow plug according to the invention (and also that of the known glow plug), that is to say the portion of the electrode provided with the primary connector, the front end, with ceramic cartridge, heating is not shown.
• the glow plug 1 of the invention consists of a tubular body 10 whose not shown front end is provided with a ceramic heating cartridge or metal tube housing a resistant filament, heating. This filament is connected at one end to the tubular body 10 forming a conductor for connection with the ground of the vehicle electrical circuit and its other end is connected to a central electrode 20 passing through the bore 11 of the tubular body 10 to receive at its end.
• a primary connector 40 with interposition of a seal 30 providing both sealing and electrical insulation between the central electrode 20 assembled to the connector 40 and the body 10.
• the conductive metal body has, in addition to its bore 11 which passes through it end-to-end, a thread 12 for screwing the spark plug into the engine cylinder head.
• the rear of the body 10 terminates in a rear portion 13 forming a tool socket for screwing the candle.
• This portion 13 internally has a smooth surface formed by the end 14 of the bore and the rear face 131 of the portion 13 to a recess 15 to receive the seal 30 in support.
• the central electrode 20, of which only the rear part is represented, is constituted by a smooth, cylindrical rod of diameter D0 which terminates at the rear end by a knurling 21 whose diameter D i is less than or at most equal to the diameter Do the smooth part.
• the seal 30 consists of a sleeve 31 whose outer diameter D2 is slightly greater than the inner diameter D3 of the bore 11 and the inner diameter D4 is substantially equal to the diameter D0 of the central electrode 20.
• the sleeve 31 is continued by a flange 32 made in one piece with the sleeve 31.
• the sleeve 31 is housed in the gap between the central electrode 20 and the end 14 of the bore by a tight fitting, the collar 32 coming into part in the counterbore 15. The assembly is clamped by the connector 40.
• the connector 40 is a solid piece provided with a piercing terminal 41 to receive the end of the central electrode 20 including its knurled portion 21.
• the connector 40 has a support flange 42 followed by a stop flange 43 defining the surface 44 receiving the connector of the manufacturer.
• the assembly ends by crimping 50 of the portion of the connector 40 between the two flanges 42, 43 on the knurled end 21 of the central electrode 20.
• the sealing of the interior of the spark plug is achieved by the tight contact of the sleeve 31 and its permanent compression between the smooth surface of the central electrode 20 and the bore 1 1 in its part 14.
• the thickness of the wall of the sleeve 31, that is to say greater than the dimension of the gap between the bore 1 1 in its portion 14 and the smooth wall of the central electrode 20 is (D3-Do) / 2.
• the internal diameter D 4 is equal to the diameter C 0 of the central electrode 20 so that the sleeve 31 is not likely to be blocked or damaged by the knurling 21 whose diameter Di is smaller than the diameter C d central electrode 20.
• the seal 30 is preferably obtained by injection of composite plastic under heat and pressure, polyamide PA6 or PA66.
• the seal is obtained by the force introduction of the sleeve 31 between the two surfaces defining the circular gap in the central electrode.
• the reduction in the thickness of the sleeve 31 resulting from its forced insertion into the gap applies the sleeve 31 to pressure evenly against the surface of the bore 1 1 and that of the central electrode 20. This pressure remains constant and ensures the seal between the cavity of the tubular body and the environment.
• Figure 1A shows the glow plug in the finished state after crimping.
• FIG. 2A shows the first step of mounting the rear end of the glow plug 1, the front end being already assembled, that is to say the heating cartridge being fixed to the body 10 and to the front end of the central electrode 20.
• the unassembled sectional view of FIG. 2A makes it possible to see more precisely the shape of the different elements at their junctions.
• Figure 3A shows the assembly of the rear end of the glow plug 1 before crimping and after crimping the glow plug 1 is in the completed state, shown in Figure 1A.

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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)

Applications Claiming Priority (2)

Publications (1)

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Family Applications (1)

Country Status (5)

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• 2014
  • 2014-05-13 FR FR1454232A patent/FR3021094A1/fr active Pending
• 2015
  • 2015-04-29 EP EP15718895.4A patent/EP3143332A1/de not_active Withdrawn
  • 2015-04-29 CN CN201580024816.0A patent/CN106461217A/zh active Pending
  • 2015-04-29 WO PCT/EP2015/059266 patent/WO2015173017A1/fr active Application Filing
  • 2015-04-29 JP JP2017503071A patent/JP2017510789A/ja active Pending

Non-Patent Citations (1)

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