Electric heating – Heating devices – Resistive element: igniter type
Patent
1997-11-03
2000-04-25
Paschall, Mark
Electric heating
Heating devices
Resistive element: igniter type
219544, 123145A, F23Q 722
Patent
active
060546808
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a glow plug for diesel engines having a ceramic heating apparatus.
BACKGROUND INFORMATION
A conventional glow plug is described in German Patent Application No. 38 37 128, in which a ceramic heating apparatus is held by the tip of a cylindrical holder. The ceramic heating apparatus is electrically insulated with respect to the holder. Provided on the end of the cylindrical holder which is opposite to the ceramic heating apparatus is a connector apparatus which makes contact to supply voltage. The ceramic heating apparatus consists of a U-shaped heating segment. The two ends of the U-shaped heating segments each make contact with the connector apparatus. During a preheat operation, a voltage is applied to the ceramic heating apparatus so that a current flows through the ceramic heating segment, specifically from one end of the U-shaped heating segment via the tip on the heating segment in the combustion chamber to the other end of the U-shaped heating segment. Due to of the resistance of the ceramic, the current causes heating of the heating segment so that the latter glows and can ignite the fuel/air mixture.
SUMMARY OF THE INVENTION
The sheathed type glow plug according to the present invention has the advantage that the region of the heating apparatus which is most accessible to the combustible mixture reaches the required ignition temperature most quickly because its resistance is thereby greater. Shorter preheat times are thus possible. The increase in resistance resulting from a reduction in the cross section of the electrically conductive ceramic makes it possible to use a ceramic heating element with greater wall thickness, which then has a reduced cross section only at the desired points, which depend on the design of the engine. The mechanical strength of, in particular, the ceramic heating segment can thereby be increased. With the defined reduction in the wall thickness, it is possible for the point on the sheathed type glow plug which is struck by the combustible mixture to be exactly that point which becomes the hottest.
It is also advantageous that by reducing the wall thickness of the ceramic heating apparatus in the side wall, an increase in resistance and thus a faster attainment of operating temperature at that point can be implemented easily and with no change in the nature of the material. When the sheathed type glow plug is installed in the swirl chamber, the point on the heating apparatus which has the best mixture accessibility is exactly the point which becomes hottest, thus resulting in better ignition of the diesel mixture.
The reduction in the cross section of the current path through the ceramic can be effected in a further simple and cost-effective manner if a known U-shaped or sleeve-shaped ceramic heating apparatus is simply equipped, at the points of the reduction in cross section, with interruptions, for example holes. This requires no new correspondingly adapted fabrication, but rather, for example, an addition of a further working step, for example drilling. Filling the electrically conductive ceramic heating apparatus with electrically insulating material increases the mechanical strength of the ceramic heating apparatus.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a first embodiment of a sheathed type glow plug according to the present invention.
FIG. 2 shows a second embodiment of the sheathed type glow plug according to the present invention.
FIG. 3 shows a third embodiment of the sheathed type glow plug according to the present invention.
FIG. 4 shows a fourth embodiment of the sheathed type glow plug according to the present invention.
FIG. 5 shows two exemplary variant installations of the glow plug in a swirl chamber of an internal combustion engine.
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows a longitudinal section of a sheathed type glow plug according to a first embodiment of the present invention. The sheathed type glow plug includes a cylindrical metal tube 1. This cylindrical meta
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Boeder Horst
Geissinger Albrecht
Heussner Karl-Heinz
Locher Johannes
Oberle Juergen
Paschall Mark
Robert & Bosch GmbH
Van Quang
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