Glow plug with a plug body formed of multiple tubes end to end

Abstract

A glow plug includes a heating rod ( 11 ), a plug body ( 13 ), a mounting device ( 48 ) for mounting the heating rod, permitting axial translation movements of the heating rod relative to the plug body and ensuring impermeability between the heating rod and the plug body, and a load sensor ( 17 ) which is interposed in a proximal zone between the heating rod and the plug body. The plug body is composed of multiple distinct metal tubes ( 45, 95 ) which are rigidly assembled and extend each other axially, including, around the mounting device and the load sensor, a metal distal tube ( 45 ) extending a metal proximal tube ( 95 ), the distal tube having a lesser thickness than that of the proximal tube.

1 - 12 . (canceled) 
     
     
         13 . Glow plug comprising:
 a heating rod ( 11 ,  11 ′) having an extremity, called the proximal extremity ( 38 ), which is equipped with an electrical power supply connection of the heating rod,   a plug body ( 13 ), forming a housing, called a receiving housing ( 14 ), receiving the heating rod, the latter having a distal portion which extends axially, projecting beyond the plug body,   a mounting device ( 48 ) for mounting the heating rod in said receiving housing ( 14 ),   a load sensor ( 17 ,  67 ) which is interposed in a proximal zone between the heating rod and the plug body, so that axial translation movements of the heating rod relative to the plug body generate axial compression and/or traction stresses in said load sensor,   the plug body ( 13 ) being composed of multiple distinct parts ( 45 ,  95 ) which are rigidly assembled and extend each other axially, characterized in that the plug body ( 13 ) is composed of multiple distinct metal tubes ( 45 ,  95 ) comprising, around said mounting device ( 48 ) and the load sensor ( 17 ,  67 ), a metal distal tube ( 45 ) extending a metal proximal tube ( 95 ), said distal tube having a lesser thickness than that of said proximal tube, at least at their joined ends, so as to increase the available internal space for forming said receiving housing ( 14 ), in that said distal tube ( 45 ) is formed of a first metal alloy, in that said proximal tube ( 95 ) is formed of a second metal alloy, and in that the first metal alloy forming said distal tube has mechanical properties which are superior to those of the second metal alloy forming said proximal tube.)   
     
     
         14 . Glow plug according to  claim 13 , characterized in that the first metal alloy forming said distal tube ( 45 ) is of stainless steel with high characteristics, and in that the second metal alloy forming said proximal tube ( 95 ) is a stainless steel for rapid machining. 
     
     
         15 . Glow plug according to  claim 13 , characterized in that the first metal alloy forming the distal tube ( 45 ) has a greater elastic limit than that of the second metal alloy forming the proximal tube ( 95 ). 
     
     
         16 . Glow plug according to  claim 13 , characterized in that the difference of thickness between the distal tube ( 45 ) and the proximal tube ( 95 ) is such that:
 Y 1 ×S 1 =Y 2 ×S 2 , where Y 1  is the elastic limit of the metal alloy forming the proximal tube, S 1  is the section formed by said thickness of the proximal tube ( 95 ), Y 2  is the elastic limit of the metal alloy forming the distal tube ( 45 ), and S 2  is the section formed by said thickness of the distal tube ( 45 ).   
     
     
         17 . Glow plug according to  claim 13 , characterized in that said proximal tube ( 95 ) and said distal tube ( 45 ) have the same external diameter. 
     
     
         18 . Glow plug according to  claim 13 , characterized in that the proximal tube ( 95 ) has, at its distal extremity, a constriction ( 96 ) of its external wall forming a recess to receive the proximal extremity of the distal tube ( 45 ). 
     
     
         19 . Glow plug according to  claim 13 , characterized in that the internal diameter of the proximal tube ( 95 ) is smaller than the internal diameter of the distal tube ( 45 ). 
     
     
         20 . Glow plug according to  claim 13 , characterized in that the plug body ( 13 ) includes only two tubes, said proximal tube ( 95 ) and said distal tube ( 45 ), which extend each other axially. 
     
     
         21 . Glow plug according to  claim 13 , characterized in that it includes a distal extremity washer ( 47 ), which extends the distal extremity of said distal tube ( 45 ) and forms the distal extremity of the plug body. 
     
     
         22 . Glow plug according to  claim 13 , characterized in that said proximal tube ( 95 ) has an external threaded portion ( 43 ) for fitting the plug onto an engine. 
     
     
         23 . Glow plug according to  claim 13 , characterized in that said load sensor ( 17 ,  67 ) is a tubular sleeve which extends around a portion, called the proximal portion ( 50 ,  63 ), of a peripheral metal tube ( 59 ,  61 ) of the heating rod ( 11 ,  11 ′), and in that the tubular load sensing sleeve ( 17 ,  67 ) adjoins the mounting device ( 48 ) directly and axially on the proximal side. 
     
     
         24 . Glow plug according to  claim 23 , characterized in that the load sensing sleeve ( 17 ,  63 ) is in the form of a tubular block, and in that the heating rod ( 11 ,  11 ′) passes axially through the mounting device ( 48 ) entirely, and at least partially through the load sensing sleeve ( 17 ,  67 ). 
     
     
         25 . Glow plug according to  claim 13 , characterized in that said mounting device includes a mounting bush ( 48 ) which is fixed in said receiving housing ( 14 ) and around said proximal portion ( 50 ,  63 ) of the peripheral metal tube ( 59 ,  61 ) of the heating rod, in that the load sensing sleeve ( 17 ,  67 ) is carried by said mounting bush ( 48 ), in that the mounting bush ( 48 ) has a first fixing face ( 19 ) which is fixed rigidly and impermeably to an internal wall ( 44 ) facing the receiving housing ( 14 ), and a second fixing face ( 22 ) which is fixed rigidly and impermeably around said proximal portion ( 50 ,  63 ) of the heating rod, in that said first ( 19 ) and second ( 22 ) fixing faces of the mounting bush at least partially face each other radially, in that said load sensing sleeve ( 17 ,  67 ) extends axially beyond said fixing faces ( 19 ,  22 ) of the mounting bush ( 48 ), towards the proximal extremity of the heating rod, and in that the mounting bush and the load sensing sleeve ( 17 ,  67 ) are contained in said distal tube. 
     
     
         26 . Glow plug according to  claim 24 , characterized in that the mounting bush ( 48 ) includes:
 a sleeve ( 16 ) for receiving the heating rod which forms said second fixing face ( 22 ), and a fixing ring ( 15 ) which forms said first fixing face ( 19 ), said receiving sleeve being guided in axial translation in the fixing ring, the receiving sleeve being connected to a distal extremity ( 25 ) of the fixing ring,   a linking tube ( 18 ) surrounding the load sensing sleeve ( 17 ,  67 ) and connecting said second axial extremity ( 37 ) of the load sensing sleeve to said first fixing face ( 19 ), and in that the linking tube ( 18 ) is connected to a proximal extremity ( 28 ) of the fixing ring.   
     
     
         27 . Glow plug according to  claim 14 , characterized in that the first metal alloy forming the distal tube ( 45 ) has a greater elastic limit than that of the second metal alloy forming the proximal tube ( 95 ). 
     
     
         28 . Glow plug according to  claim 14 , characterized in that the difference of thickness between the distal tube ( 45 ) and the proximal tube ( 95 ) is such that:
 Y 1 ×S 1 =Y 2 ×S 2 , where Y 1  is the elastic limit of the metal alloy forming the proximal tube, S 1  is the section formed by said thickness of the proximal tube ( 95 ), Y 2  is the elastic limit of the metal alloy forming the distal tube ( 45 ), and S 2  is the section formed by said thickness of the distal tube ( 45 ).   
     
     
         29 . Glow plug according to  claim 14 , characterized in that said proximal tube ( 95 ) and said distal tube ( 45 ) have the same external diameter. 
     
     
         30 . Glow plug according to  claim 14 , characterized in that the proximal tube ( 95 ) has, at its distal extremity, a constriction ( 96 ) of its external wall forming a recess to receive the proximal extremity of the distal tube ( 45 ). 
     
     
         31 . Glow plug according to  claim 25 , characterized in that the mounting bush ( 48 ) includes:
 a sleeve ( 16 ) for receiving the heating rod which forms said second fixing face ( 22 ), and a fixing ring ( 15 ) which forms said first fixing face ( 19 ), said receiving sleeve being guided in axial translation in the fixing ring, the receiving sleeve being connected to a distal extremity ( 25 ) of the fixing ring,   a linking tube ( 18 ) surrounding the load sensing sleeve ( 17 ,  67 ) and connecting said second axial extremity ( 37 ) of the load sensing sleeve to said first fixing face ( 19 ), and in that the linking tube ( 18 ) is connected to a proximal extremity ( 28 ) of the fixing ring.