Electrically-heated glowplug and method for production of an electrically-heated glowplug

Abstract

An electrically heatable glow plug and a method of manufacturing an electrically heatable glow plug allow better decoupling between a heating coil and a combustion-chamber-side end of a glow tube. The electrically heatable glow plug for internal combustion engines includes a metallic glow tube, sealed on the combustion-chamber side, into which an electrically conductive heating coil is introduced, the heating coil being connected in an electrically conductive manner to the glow tube in the region of the sealed combustion-chamber-side end of the glow tube. A sealing arrangement is provided which seals the glow tube on the combustion-chamber side and supports the heating coil and only protrudes into the heating coil if the heating coil is connected to the sealing arrangement via an inner side of the heating coil, for which purpose the sealing arrangement is in contact with the inner side of the heating coil essentially over the entire length protruding into the heating coil.

What is claimed is:  
     
         1 . An electrically heatable glow plug ( 1 ), in particular a sheathed-element glow plug, for internal combustion engines, having a metallic glow tube ( 10 ), which is closed on the combustion-chamber side, and into which an electrically conductive heating coil ( 15 ) is introduced, the heating coil ( 15 ) being connected in an electrically conductive way to the glow tube ( 10 ) in the region of the closed, combustion-chamber-side end ( 20 ) of the glow tube ( 10 ), 
 wherein a sealing means ( 25 ) is provided, which seals, on one hand, the glow tube ( 10 ) on the combustion-chamber side and supports, on the other hand, the heating coil ( 15 ), and only protrudes into the heating coil ( 15 ) if the heating coil ( 15 ) is connected to the sealing means ( 25 ) via an inner side ( 70 ) of the heating coil ( 15 ), for which purpose the sealing means ( 25 ) is, in this case, essentially in contact with the inner side ( 70 ) of the heating coil ( 15 ) over the entire length protruding into the heating coil ( 15 ).    
     
     
         2 . The glow plug ( 1 ) as recited in  claim 1 , wherein the heating coil ( 15 ) is connected to the sealing means ( 25 ) by at least one welded point, by a continuous welded seam, or a screw joint, or by crimping.  
     
     
         3 . The glow plug ( 1 ) as recited in  claim 1  or  2 , wherein the sealing means ( 25 ) is metallic, in particular of the same material as the glow tube ( 10 ).  
     
     
         4 . The glow plug ( 1 ) as recited in  claim 1 ,  2 , or  3 , wherein the sealing means ( 25 ) is welded to the glow tube ( 10 ).  
     
     
         5 . The glow plug ( 1 ) as recited in one of the preceding claims, wherein the sealing means ( 25 ) is designed as a cap, which covers the glow tube ( 10 ) on the combustion-chamber side and includes a glow-tube-side elevation ( 30 ), which receives the heating coil ( 15 ).  
     
     
         6 . The glow plug ( 1 ) as recited in one of claims  1  through  4 , wherein the sealing means ( 25 ) has a combustion-chamber side pin ( 50 ) which protrudes into a combustion-chamber side opening ( 55 ) of the glow tube ( 10 ) and seals it, and the sealing means ( 25 ) includes a glow-tube-side base ( 60 ), which receives the heating coil ( 15 ).  
     
     
         7 . The glow plug ( 1 ) as recited in  claim 6 , wherein the heating coil ( 15 ) rests on the base ( 60 ).  
     
     
         8 . The glow plug ( 1 ) as recited in  claim 6  or  7 , wherein the base ( 60 ) includes a first projection ( 65 ) on the glow-tube side, which protrudes into the heating coil ( 15 ) and is in contact with the inner side ( 70 ) of the heating coil ( 15 ) on the combustion-chamber-side end.  
     
     
         9 . The glow plug ( 1 ) as recited in  claim 6  or  7 , wherein the base ( 60 ) itself protrudes into the heating coil ( 15 ) and is in contact with the inner side ( 70 ) of the heating coil ( 15 ) on the combustion-chamber-side end.  
     
     
         10 . The glow plug ( 1 ) as recited in  claim 6  or  7 , wherein the base ( 60 ) includes a second projection ( 75 ) on the glow tube side, which encloses the outside ( 80 ) of the heating coil ( 15 ) on its combustion-chamber-side end.  
     
     
         11 . A method for manufacturing an electrically heatable glow plug ( 1 ) for internal combustion engines, in which an electrically conductive heating coil ( 15 ) is introduced into a glow tube ( 10 ), wherein, before introduction of the heating coil ( 15 ) into the glow tube ( 10 ), which is initially open on its combustion-chamber-side end ( 20 ), the heating coil ( 15 ) is first connected on its combustion-chamber-side end to a sealing means ( 25 ), the sealing means ( 25 ) only protruding into the heating coil ( 15 ) if the heating coil ( 15 ) is attached to the sealing means ( 25 ) via an inner side ( 70 ) of the heating coil ( 15 ), for which purpose the sealing means ( 25 ) is essentially in contact with the inner side ( 70 ) of the heating coil ( 15 ) over the entire length protruding into the heating coil ( 15 ); and after introduction of the heating coil ( 15 ), together with the sealing means ( 25 ) positioned on the combustion-chamber side, into the glow tube ( 10 ), the glow tube is sealed on its combustion-chamber-side end ( 20 ) by the sealing means ( 25 ).