Title of Invention

SHEATHED-ELEMENT GLOW PLUG

Abstract A sheathed-element glow plug with a tubular glow plug housing, in the longitudinal bore of which a sheathed element is secured at the combustion space end to a certain extent in a seal-forming way, is proposed, a connecting stud being attached to the glow plug housing at the end remote from the combustion space. Attached to the connecting stud which is arranged coaxially with respect to the bore of the glow plug housing is a tubular element (15) which acts as a seal- forming, insulating and centring element between the connecting stud and glow plug housing. The plug of the cable harness at the engine end is secured axially to the tubular element (15) by means of the positively locking element (23) on the outer casing.
Full Text

The invention is based on a sheathed-element glow plug for arrangement in the combustion space of air-compressing internal combustion engines of the generic type of the present invention. In such known sheathed-element glow plugs, the three components round plug (round nut), insulating disc and double seal in the upper region between the connecting stud and sheathed-element glow plug fulfill essentially different functions. The round plug forms the connecting element between the connecting stud of the sheathed-element glow plug and the plug of the cable harness at the engine end by virtue of a frictionally locking and/or positively locking connection. The metallic, and thus conductive, material of the round plug also serves to form a contact and conduct current between the cable harness and the connecting stud.
The insulating disc made of temperature-resistant and electrically non-conductive material serves to provide electrical insulation between the glow plug housing and round plug. The so-called double seal not only serves to provide electrical insulation between the glow plug housing and the round plug and to centre the connecting stud in the glow plug housing but also mainly to seal off the Interior of the glow plug housing from the surroundings. The double seal is characterized both by a seal-forming face which acts on the interior of the glow plug and a seal-forming fece which acts on the connecting stud. It is clear from this that three different components made of different material are necessary for this.
Advantages of the invention
In contrast with the above, the sheathed-element glow plug according to the invention, having the characterizing features of the present invention, has the advantage that only a single component - the so-called insulating sleeve - is required for the abovementioned functions and requirements. This component

may be composed of electrically insulating material or electrically conductive material with an electrically insulating coating.
Furthermore, this component can both ensure the seal-forming function with respect to the glow plug housing and the connecting stud and the centring function of the connecting stud with respect to the glow plug housing. The electrical contact between the plug of the cable harness at the engine and the sheathed-element glow plug can be brought about by means of a direct plug-type contact with the end of the metallic connecting stud which projects out of the sleeve-shaped insulating sleeve. In addition to the described frictional locking of the plug-type contact, the plug can be secured here to the outer casing of the insulating sleeve by means of an appropriately shaped positively locking element.
The reduction in the number of components from the previous three to a single component makes simpler and more cost-effective mounting possible by reducing the number of mounting operations and test steps. The replacement of the previous three components, round plug (round nut), insulating disc and double seal by a single component also makes it possible to reduce the cost of materials significantly.
Accordingly, the present invention also provides a sheathed-element glow plug arrangement in the combustion space of air-compressing internal combustion engines, having a tubular, metallic glow plug housing in whose longitudinal bore a sheathed element is secured by part of its length in a seal-forming way, and with a connecting stud which serves to conduct current, characterized in that the connecting stud is connected to the glow plug housing in a seal-forming way by means of a one-piece tubular element which has two

seal-forming faces at its end which is located at the glow plug housing, and a positively locking element on the external surface of its casing.
BRIEF DESCRIPTION OF THE DRAWINGS
With reference to the accompanying drawings in which :

Figure 1 of the drawing shows a partial longitudinal section through a sheathed-element glow plug, and Figure 2 shows a longitudinal half-section through the individual component according to the invention on an enlarged scale.
The sheathed-element glow plug 10 is composed, in a known manner, of a tubular glow plug housing 11 made of metallic, and thus electrically conductive material, A connecting stud 12 is inserted coaxially in the longitudinal bore llA of the glow plug housing 11, In addition, a sheathed element 13, which is usually pressed in, is located in the glow plug housing 11. The connecting stud projects with its upper end out of the glow plug housing and serves to form a contact between the engine-end plug and to conduct current.
The tubular element 15 according to the invention is introduced into the glow plug housing 11 by means of the connecting stud 12 in such a way that a contact area is formed both between the tubular element and the connecting stud and between the tubular element 15 and the inner contour of the longitudinal bore llA of the glow plug housing, The contact area can be produced by pressing, and subsequently securing axially, the inner and/or outer edge of the tubular element in the region of the end face which points into the interior of the glow plug housing against a cone on the inner bore of the glow plug housing and/or of the connecting stud.
These contact areas on the inner and outer " surfaces of the casing of the tubular element 15 serve to centre the upper part of the connecting stud with respect to the longitudinal bore llA and to seal off the interior of the glow plug housing from the surroundings. In this respect, reference is made to

Figure 2 in which an outer seal-forming face 18 and an inner seal-forming face 19 are shown at the bottom on the tubular element. The seal is therefore provided here directly by the tubular element, but also may be provided, depending on the type of joining method employed, by the use of a joining agent, for example adhesive. Figure 2 shows the tubular element 15 according to the exemplary embodiment in Figure 1 on an enlarged scale. This component may be fabricated from electrically insulating material or electrically conductive material with an electrically insulating coating- On the outer circumference of the part of the tubular element 15 which projects out of the glow plug housing 11, a circumferential bead 23, which has any desired geometry and which serves as a positively locking element for the plug of the cable harness at the engine end, is formed. The tubular element according to the exemplary embodiment in Figure 1 or Figure 2 has an internal thread 16 as a means of forming a connection to the connecting stud 12. Said thread 16 merges at the end of the tubular element which is directed into the interior of the glow plug housing with a bore which has an internal diameter which is greater than that of the diameter of the thread. The seal according to this exemplary embodiment is produced, as already mentioned, by means of the inner and outer seal-forming faces 18, 19 of the end of the tubular element which is directed into the interior of the glow plug housing.
The tubular element according to the exemplary embodiment 2 has two cylindrical faces on the inner diameter and outer diameter, which act as a means of forming a connection with a seal-forming function, either directly by means of interference fits or indirectly by means of joining agents from the methods mentioned above.



WE CLAIM :
1. A sheathed-element glow plug (10) arrangement in the combustion space of air-compressing internal combustion engines, having a tubular, metallic glow plug housing (11) in whose longitudinal bore (1 lA) a sheathed element (13) is secured by part of its length in a seal-forming way, and with a connecting stud which serves to conduct current, characterized in that the connecting stud (12) is connected to the glow plug housing in a seal-forming way by means of a one-piece tubular element (15) which has two seal-forming faces (18, 19) at its end which is located at the glow plug housing (II), and a positively locking element (23) on the external surface of its casing.
2. The sheathed-element glow plug as claimed in claim 1, wherein the seal-forming connection (16) between the connecting stud (12) and tubular element (15) is a thread.
3. The sheathed element glow plug as claimed in claim 1. wherein the connection (16) between he connecting stud (12) and tubular element (15) is a welded, bonded, press-in or caulked connection.
4. The sheathed element glow plug as claimed in any one of claims 1 to 3, wherein the positively locking element (23) is a bead (23) which has any desired geometry and which is formed on the outside of the tubular element (15), and is at the same time securing means for the plug of the cable harness at the engine end.

5. The sheathed element glow plug as claimed in any one of claims 1 to 4, wherein one external seal-forming face (18) and one internal seal-forming face (19) are formed on the internal end side of the tubular element (15).
6. The sheathed element glow plug as claimed in any one of claims 1 to 5, wherein the tubular element (15) also forms an electrical insulation between the connecting stud (12) and glow plug housing (11).
7. The sheathed element glow plug as claimed in any one of claims 1 to 6,
wherein the tubular element (15) is also a means for centring the connecting the
stud with respect to the glow plug housing.
8. A sheathed element glow plug, substantially as herein described with
reference to the accompanying drawings.


Documents:

0160-mas-1999-abstract.pdf

0160-mas-1999-claims filed.pdf

0160-mas-1999-claims granted.pdf

0160-mas-1999-correspondnece-others.pdf

0160-mas-1999-correspondnece-po.pdf

0160-mas-1999-description(complete)filed.pdf

0160-mas-1999-description(complete)granted.pdf

0160-mas-1999-drawings.pdf

0160-mas-1999-form 1.pdf

0160-mas-1999-form 26.pdf

0160-mas-1999-form 3.pdf

0160-mas-1999-other documents.pdf


Patent Number 213915
Indian Patent Application Number 160/MAS/1999
PG Journal Number 13/2008
Publication Date 31-Mar-2008
Grant Date 23-Jan-2008
Date of Filing 08-Feb-1999
Name of Patentee ROBERT BOSCH GMBH
Applicant Address POSTFACH 30 02 20, D-70442 STUTTGART,
Inventors:
# Inventor's Name Inventor's Address
1 JOHANNES LOCHER C.P.O. BOX 4703, ROK-1064 SEOUL,
2 WERNER TESCHNER BERNSTEINSTRASSE 24, 70619 STUTTGART,
3 STEFFEN SCHOTT STUTTGARTER STRASSE 69/2, 71701 SCHWIEBERDINGEN,
PCT International Classification Number F 23 Q 07/00
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA