| 主权项 |
1. An assembly comprising:
a main body of an engine having a spark plug-mounting bore formed therein, the main body also having a female-threaded portion that is formed in an inner surface of the spark plug-mounting bore and a seat surface that is formed around an open end of the spark plug-mounting bore; a spark plug having a longitudinal axis and a male-threaded portion that is formed on an outer surface of the spark plug so as to threadedly engage with the female-threaded portion of the main body of the engine, the spark plug also having a seating surface that is formed on one side of the male-threaded portion so as to face the seat surface of the main body of the engine; and a substantially annular gasket interposed between the seat surface of the main body of the engine and the seating surface of the spark plug so as to hermetically seal therebetween, wherein
the spark plug is mounted to the main body of the engine by tightening the male-threaded portion of the spark plug into the female-threaded portion of the main body with the gasket elastically deformed between the seat surface of the main body of the engine and the seating surface of the spark plug,the gasket is made of a metallic material whose yield stress or 0.2% proof stress is higher than or equal to 200 N/mm2,the gasket has a first contact surface that is in contact with the seating surface of the spark plug and a second contact surface that is in contact with the seat surface of the main body of the engine,the first and second contact surfaces of the gasket are each formed as a part of a curved surface that has a convex shape on a cross section of the gasket, the cross section being taken so as to lie in the same plane as the longitudinal axis of the spark plug,the first and second contact surfaces of the gasket are offset from each other in a radial direction of the spark plug, andthe amount of radial offset between the first and second contact surfaces of the gasket is greater than or equal to 0.6 mm. |
