Title of Invention

SHEATHED ELEMENT GLOW PLUG

Abstract

According to the invention, the sheathed-element glow plug (10) has a plug-and-caulk connection which is modified by comparison with the state of the art in such a way that it is possible for the centring turns (18A) of a glow filament (18) to be fed into a corresponding U-shaped bead (20) of the connecting bolt (17) both radially and axially. After the prepositioning of the glow filament in the bead, the glow filament and connecting bolt can be radially caulked, or the bead can be dispensed with entirely given an appropriate geometrical configuration. The opening on the circumference of the connecting bolt in the region of the bead (20) permits both radial and axial accessibility of the internal contour of the bead. It is possible as a result to ensure complete cleaning of organic lubricants and reliable checking of the cleaning. This reduces the rate of early failures of sheathed-element glow plugs caused by organic fouling.

Full Text

The invention proceeds from a sheathed-element glow plug according to the generic concept of the main claim. At present, with known sheathed-element glow plugs there are essentially two variants for fastening the glow filament to, or making contact between it and the connecting bolt. The first variant is a hot-staking connection, in which the glow filament is welded to the connecting bolt. The second variant, with which the invention is concerned, is a "plug-and-caulk connection". For this type of connection, a so-called plug-and-caulk bore is produced by machining on the lower end of the connecting bolt. During mounting, the centring turns of the glow filament are inserted into this bore and subsequently secured in their position by radial caulking. In the case of the known sheathed-element glow plugs producing the plug-and-caulk bore in the connecting bolt by machining causes fouling of the bore because of the use of lubricants which is required for this purpose. Owing to the poor accessibility for cleaning and checking this bore, this design is attended by a substantial risk of fouling which can lead to early failures in operating the sheathed-element glow plug. Advantages of the invention The sheathed-element glow plug according to the invention and having the characterizing features of the main claim has, by contrast, the advantage that the bore previously produced in the connecting bolt by machining is replaced by a recess of U-shaped cross section. The centring turns of the glow filament can thereby be inserted without difficulty. Accordingly, the present invention provides a sheathed-element glow plug for arrangement in the combustion chamber of air-compressing internal combustion engines, having a tubular, metallic plug housing in the longitudinal bore of which a sheathed-element is fixed in a sealing fashion with a part of its length, and having a connecting bolt which serves to conduct current and is situated partially in the sheathed-element and in which an axially running recess facing the tip of the sheathed element is formed in which a connection is made by means of a plug-and-caulk type connection between the connecting bolt and the centring turns of the glow filament, characterized in that there is formed in the end of the connecting bolt facing the tip of the sheathed element an elongated recess or bead which runs in the axial direction of the connecting bolt and is open towards one side, and whose clear width on the circumference of the connecting bolt corresponds approximately to that of the diameter of the centring turns of the glow filament. Further advantages of the invention follow from the subclaims, the following description and drawing. Drawing An exemplary embodiment of the invention is represented in the drawing, in which: Figure 1 shows a sheathed-element glow plug, partially in longitudinal section. Figure 2 shows a detail II in accordance with Figure 1. Figure 3 shows the lower end of the connecting bolt in partial section. Figure 4 shows a side view in partial section in accordance with Figure 3, and Figure 5 shows a section in accordance with V-V of Figure 3. The plug housing 11 of the sheathed-element glow plug 10 according to Figure 1 had a continuous longitudinal bore 12. A sheathed element 14 is pressed in in the lower part of the longitudinal bore of the plug housing. This sheathed element comprises a hot tube - 16, a connecting bolt 17, a glow filament 18 with filling powder 19 in the sheathed element as well as a seal 22 between the hot tube 16 and connecting bolt 17. In the detail Y in accordance with Figure 1, the connection between the connecting bolt 17 and the glow filament 18 is represented according to the presently-known plug-and-caulk technique. The connecting bolt 17 has a bore 22 at the lower end. The glow filament essentially comprises two cylindrical regions of different turn diameters. The smaller cylindrical region of the centring turn 18A of the glow filament 18 is inserted axially into the bore 23 of the connecting bolt 17. The axial positioning of the glow filament is ensured by stopping the region of the cylindrical glow filament turns 18B with the larger turn diameter against the end face 17A of the connecting bolt. During mounting, the glow filament prepositioned in this way is joined by simultaneous radial caulking to two or more mutually opposite positions of the bore in the connecting bolt. The plastic deformation of the bore caused thereby effects both a force-closed and a self-closed connection in the region of the caulking owing to the ellipsoidal formation of said bore. Figures 3 to 5 show different views of an example of the modification according to the invention of the plug-and-caulk connection. The configuration of the glow filament 18 remains unchanged by comparison with the representation in Figures 1 and 2. The plug-in bore in accordance with the presently current design according to the invention is designed in accordance with Figures 3 to 5. Formed in the lower end of the connecting bolt 17 is an elongated recess or bead 20, which runs along the same axis as the longitudinal axis of the connecting bolt. It has a U-shaped cross section, that is to say it has an opening 2 0A on one side and thereby ensures radial prepositioning during insertion of the centring turns 18A of the glow EIIament ±&. it is therefore optionally possible to select the mounting direction of the glow filament to be axial or radial to the longitudinal axis of the bead 20. The axial positioning of the glow filament is ensured by stopping the region of the cylindrical glow filament turns with the larger turn diameter 18B against the end face 17A of the connecting bolt 17, in a way similar to Figures 2 and 4. The centring turns 18A of the glow filament which are thereby prepositioned on the same axis as the longitudinal axis of the connecting bolt are joined to one another by means of two or more simultaneous radial caulkings 17B and 17C - see Figure 5 in this connection. The radial caulking movement, directed from outside into the centre, onto the outer contour of the U-shaped bead 20 causes plastic deformation of the two limbs 17B, 17C, thus producing both a force-closed and a self-closed connection between the connecting bolt 17 and centring turns 18A of the glow filament 18 in the region of the caulking. WE CLAIM: 1. A sheathed-element glow plug (10) for arrangement in the combustion chamber of air-compressing internal combustion egines, having a tubular, metallic plug housing (11) in the longitudinal bore (12) of which a sheathed-element (14) is fixed in a sealing fashion with a part of its length, and having a connecting bolt (17) which serves to conduct current and is situated partially in the sheathed-element and in which an axially running recess facing the tip of the sheathed element is formed in which a connection is made by means of a plug-and-caulk type connection between the connecting bolt (17) and the centring turns (18A) of the glow filament (18), characterized in that there is formed in the end of the connecting bolt (17) facing the tip of the sheathed element an elongated recess or bead (20) which runs in the axial direction of the connecting bolt and is open towards one side, and whose clear width on the circumference of the connecting bolt corresponds approximately to that of the diameter of the centring turns (18A) of the glow filament (18). 2. The sheathed-element glow plug as claimed in claim 1, wherein the recess or bead (20) has a U-shaped cross section and contains both on the end face and on the circumference of the connecting bolt (17) an opening (20A) which permits the mounting, cleaning and testing of the recess in the radial and/or axial direction. 3. The sheathed-element glow plug as claimed in claim 1 or 2, wherein the inner contour of the recess or bead (20), which inner contour has the same axis as the longitudinal axis of the connecting bolt (17) is produced by machining methods, such as, for example, milling, grinding inter alia, or forming methods such as, for example, rolling, cold-impact extrusion inter alia. has the same axis as the longitudinal axis of the connecting bolt (20), ensures the radial prepositioning of the centring turns (18A) of the glow filament (18). 5. The sheathed-element glow plug as claimed in any one of the claims 1 to 4, wherein during mounting the prepositioned glow filament (18) is joined by simultaneous radial caulking to a plurality of mutually opposite positions (17B, 17C) of the bead (20) in the connecting bolt in such a way that the plastic deformation of the bead thereby caused forms both a force-closed and a self- closed connection with the centring turns of the glow filament by virtue of the ellipsoidal formation of the bead. 6. The sheathed-element glow plug as claimed in any one of the claims 1 to 5, wherein the opening (20A) of the bead (20) tapers from inside outwards in the radial direction to a dimension which is smaller than that of the centring turn diameter of the glow filament, and in that the inner contour of the bead is formed such that pressing the centring turns of the glow filament radially into the opening (20) of the connecting bolt (17) produces, owing to the geometrically caused oversize, a snap-fit connection which dispenses with the need for the mounting operation of caulking. 7 A sheathed-element glow plug, substantially as herein described with reference to the accompanying drawings

Documents:

0017-mas-1999 complete specification as granted.pdf

17-mas-1999-abstract.jpg

17-mas-1999-abstract.pdf

17-mas-1999-claims.pdf

17-mas-1999-correspondence others.pdf

17-mas-1999-correspondence po.pdf

17-mas-1999-description complete.pdf

17-mas-1999-drawings.pdf

17-mas-1999-form 1.pdf

17-mas-1999-form 26.pdf

17-mas-1999-form 3.pdf

17-mas-1999-other documents.pdf

abs-17-mas-1999.jpg

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