Abstract:
Method of joining a rod-shaped heating element with a tubular carrier element involving attaching a cylindrical carrier ring to the rod-shaped heating element using a magnetic forming process and inserting the carrier ring and the rod-shaped heating element into the tubular carrier element such that the outer circumferential surface of the carrier ring contacts the inner circumferential surface of the tubular carrier element.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The invention relates to a method for joining a rod-shaped heating element with a tubular carrier element, and a rod glow plug which includes a rod-shaped heating element in a tubular glow plug body.  
           [0003]    2. Description of Related Art  
           [0004]    Rod-shaped heating elements which are supported in tubular carrier elements are known. One of the best known examples of a rod-shaped heating element is a glow plug which includes a rod-shaped glow pencil is supported in a tubular glow plug body.  
           [0005]    When joining a glow pencil and a glow plug body, the glow pencil is pressed or inserted into the glow plug body. In such a case, only materials which exhibit sufficient deformability and non-deformability for such a pressing-in operation can be used. For pressing-in the heating element, certain component lengths, especially of the glow pencil, should not be exceeded in order to avoid buckling of this component during the pressing-in operation. Furthermore, grooves can arise during pressing-in, which lead to looseness between the glow pencil and the glow plug body.  
         SUMMARY OF THE INVENTION  
         [0006]    The object of the present invention is to provide a method of joining a rod-shaped heating element with a tubular carrier element so as to overcome the aforementioned disadvantageous effects that occur with the pressing-in of the heating element into the carrier element. At the same time, the method in accordance with the present invention does not require a certain component length in order to avoid the buckling of the component. In this regard, a ceramic rod-shaped heating element may be used in order to be easily joined with metal carrier elements without the aforementioned groove formation occurring.  
           [0007]    The aforementioned problems are solved in accordance with the present invention by providing a method of joining a rod-shaped heating element with a tubular carrier element whereby a cylindrical carrier ring is connected to the rod-shaped heating element using magnetic forming technology, and the rod-shaped heating element and carrier element are subsequently inserted into the tubular carrier element.  
           [0008]    An advantageous feature in accordance with the present invention is the attaching or forming of the rod-shaped heating element with a carrier ring using magnetic forming technology. The magnetic forming technology may be providing using “MagnetoPuls” from Magnet-Physik Dr. Steingroever GmbH of Cologne, Germany.  
           [0009]    The present invention will be explained in greater detail with a preferred example of a glow plug with rod-shaped heating element and tubular carrier element according to the following figures, which show: 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    [0010]FIG. 1 shows a diagrammatic side view of a glow pencil with a cylindrical carrier ring and a connection pole;  
         [0011]    [0011]FIG. 2 shows a glow pencil provided with a carrier ring and a connection pole, each of which is fitted into a glow plug casing;  
         [0012]    [0012]FIG. 3 shows a glow pencil with a cylindrical carrier ring, a contact sleeve and a connection pole;  
         [0013]    [0013]FIG. 4 shows the glow pencil shown in FIG. 3 with a carrier ring, a contact sleeve and a connection pole in a glow plug body with a transfer ring lying adjacent on the outside; and  
         [0014]    [0014]FIG. 5 shows another embodiment of a glow plug in accordance with FIGS. 3 and 4 with the transfer ring removed and a sealing and fixing cylindrical necked-down portion of a glow plug body.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0015]    [0015]FIG. 1 shows a diagrammatic side view of a glow pencil  1  made of an electrically conductive ceramic, on which a carrier ring  2  is formed or attached using magnetic forming technology. The material of carrier ring  2  is electrically conductive and deformable using magnetic forming technology. A connection pole  5  used as a positive pole is connected to the glow pencil  1 .  
         [0016]    As shown in FIG. 2, a single-pole glow plug as shown FIG. 1 is inserted into the glow plug body  3 , the glow plug body serving as an earth or negative pole. The insertion of the glow pencil and the carrier ring  2  is such that the pressing-in or inserting force is brought to bear on the carrier ring  2 , so that the risk of buckling the glow pencil  1  and the connection pole  5  is prevented. Such a design permits the use of very thin glow pencils  1  and glow pencils that are composed of a brittle material, such as ceramics. Preferably, the glow plug body  3  is attached to the carrier ring  2  using magnetic forming technology, as will be described in detail somewhat later in the description of FIGS. 4 and 5.  
         [0017]    Alternatively, instead of composing the glow pencil  1  of a ceramic material, the glow pencil  3  may be composed of an electrically conductive metal. The method in accordance with the present invention is advantageous since the electrically conductive metal glow pencil  1  does not have to have the thickness and stability of conventional glow pencils, and thus, permits the production and joining, connecting or attaching of very thin-walled glow pencils  1  and glow-pencil casings or bodies  3 .  
         [0018]    [0018]FIG. 3 shows, in a second embodiment of the invention, a glow plug including a glow pencil  1 , a carrier ring  4  and a connection pole  5 . The glow pencil  1 , preferably composed of a ceramic, is connected to an internal pole  5  which axially projects on a connection side. Also provided on the connection side so as to axially surround the glow pencil  1  and the connection pole  5  is a contact sleeve  6  that is connected thereto using magnetic forming technology. The carrier ring  4  is preferably composed of a material that is deformable when using magnetic forming technology. However, the surface of the carrier ring  4 , at least the outer circumferential surface, may be made to become electrically insulating by coating it with an electrically insulating ceramic layer. Furthermore, the carrier ring  4  is attached or connected to the glow pencil  1  using magnetic forming technology. Alternatively, the glow pencil  1  can also be composed of steel, whereby it is then electrically insulated by depositing a ceramic layer thereon.  
         [0019]    If the contact sleeve  6  has an identical external diameter to the carrier ring  4 , outer circumferential surface is designed so as to be insulated by providing an electrically insulating ceramic coating. Preferably, however, the external diameter of the carrier ring  4  is greater than the external diameter of the contact sleeve  6  so that the glow plug body  3  does not physically contact the contact sleeve  6 . The carrier ring  4  is preferably composed of copper or an aluminum alloy, and may be insulated with an anodized layer or a lacquer layer.  
         [0020]    As shown in FIG. 4, the glow plug in accordance with FIG. 3 is inserted into the glow plug body  3  using magnetic forming technology. Surrounding the glow plug body  3  and the carrier ring  4  is a transfer ring  7 , through which the magnetic forming of the components occurs.  
         [0021]    As shown in FIG. 5, the glow plug body  3 , after removal of transfer ring  7 , has a cylindrical necked-down portion  8  which is formed over the internal carrier ring  4 , thereby firmly joining the arrangement shown in FIG. 3 in the glow plug body  3 . The contact sleeve  6 , which projects from the glow plug body  3 , is designed as a negative-contact connection while the glow plug casing  3  is potential-free. Preferably, the contact sleeve  6 , the carrier rings  2 ,  4  and the transfer ring  7  are respectively composed of copper, aluminum or light-metal alloys.