Heater plug having a metal finger

1. A heater plug comprising:

A tubular body ( 2 ),

A finger ( 4 ) mounted inside the tubular body ( 2 ) and protruding outside the body at one extremity of this body, and

A pressure sensor ( 8 ),

A membrane ( 28 ) extending between the body ( 2 ) and the finger ( 4 ) enabling a relative longitudinal movement between the finger ( 4 ) and the body ( 2 ),

the pressure sensor ( 8 ) being arranged between firstly a first bearing part ( 38 ) connected via a first tubular part ( 20 , 20 ′) to the finger ( 4 ) in the vicinity of the membrane ( 28 ) and a second bearing part ( 40 ) connected via a second tubular part ( 22 ) to the body ( 2 ), characterized in that the first tubular part ( 20 , 20 ′) extends into the second tubular part ( 22 ).

2. The heater plug as claimed in claim 1 , characterized in that the membrane ( 28 ) is rigidly connected to a first connection zone ( 30 ) enabling the membrane ( 28 ) to be fixed to the finger ( 4 ), and in that the first tubular part ( 20 , 20 ′) is rigidly connected to the finger ( 4 ) via a second connection zone ( 24 ) arranged less than 10 mm away from the first connection zone ( 30 ), preferably less than 7 mm away from the first connection zone ( 30 ).

3. The heater plug as claimed in claim 2 , characterized in that the first tubular part ( 20 , 20 ′) conducts heat less than the second tubular part ( 22 ).

4. The heater plug as claimed in claim 2 , characterized in that the first tubular part ( 20 ′) is blocked and welded to the finger ( 4 ) at a first extremity, and in that the second extremity thereof bears the first bearing part ( 38 ) mounted freely about an electrode ( 6 ) supplying the finger ( 4 ) with electricity.

5. The heater plug as claimed in claim 2 , characterized in that the second tubular part ( 22 ) is welded to the membrane ( 28 ) at a first extremity, and in that the second extremity thereof bears the second annular bearing part ( 40 ) mounted freely about an electrode ( 6 ) supplying the finger ( 4 ) with electricity.

6. The heater plug as claimed in claim 2 , characterized in that a filling of a material such as silicone gel ( 46 ) is added between the pressure sensor ( 8 ), the first bearing part ( 38 ), the second bearing part ( 40 ) on one hand and an electrode ( 6 ) supplying the finger ( 4 ) with electricity on the other hand.

7. The heater plug as claimed in claim 2 , characterized in that a filling ( 48 ) of a synthetic material is added to create the seal around an electrode ( 6 ) supplying the finger ( 4 ) with electricity and around other conductors coming out of the body ( 2 ).

8. The heater plug as claimed in claim 1 , characterized in that the first tubular part ( 20 , 20 ′) conducts heat less than the second tubular part ( 22 ).

9. The heater plug as claimed in claim 8 , characterized in that the two tubular parts ( 20 , 20 ′; 22 ) are metal circular cylindrical parts, in that the thickness of the wall of the first tubular part ( 20 , 20 ′) is between 0.05 mm and 0.2 mm while the thickness of the wall of the second tubular part ( 22 ) is between 0.4 mm and 1 mm.

10. The heater plug as claimed in claim 1 , characterized in that the first tubular part ( 20 ′) is blocked and welded to the finger ( 4 ) at a first extremity, and in that the second extremity thereof bears the first bearing part ( 38 ) mounted freely about an electrode ( 6 ) supplying the finger ( 4 ) with electricity.

11. The heater plug as claimed in claim 1 , characterized in that the second tubular part ( 22 ) is welded to the membrane ( 28 ) at a first extremity, and in that the second extremity thereof bears the second annular bearing part ( 40 ) mounted freely about an electrode ( 6 ) supplying the finger ( 4 ) with electricity.

12. The heater plug as claimed in claim 11 , characterized in that the second tubular part ( 22 ) is rigidly connected to the body ( 2 ) at the first extremity thereof.

13. The heater plug as claimed in claim 1 , characterized in that a filling of a material such as silicone gel ( 46 ) is added between the pressure sensor ( 8 ), the first bearing part ( 38 ), the second bearing part ( 40 ) on one hand and an electrode ( 6 ) supplying the finger ( 4 ) with electricity on the other hand.

14. The heater plug as claimed in claim 1 , characterized in that a filling ( 48 ) of a synthetic material is added to create the seal around an electrode ( 6 ) supplying the finger ( 4 ) with electricity and around other conductors coming out of the body ( 2 ).

15. A internal combustion engine, in particular a diesel engine, characterized in that it includes a heater plug according to claim 1 .