| 摘要 |
PROBLEM TO BE SOLVED: To detect a piston location by a simple constitution and to reduce top clearance by integrally connecting piston upper and lower parts by a connecting part and detecting a contact by an abnormality displacement detection means by abutting the abnormality displacement detection means on the piston lower part when a piston moves to a top dead center side by a set maximum range or more. SOLUTION: A first piston 7 is constituted of a piston upper part 71, a connecting part 73 and a piston lower part 72 into what is called a dumbbell shape. A conductive electrode part 21 as an abnormality displacement detection means is arranged so as to be opposed to a peripheral surface of the connecting part 73, the part 21 is abutted on the piston lower part 72 when the first piston 7 moves to the top dead center side by a set maximum range or more, and the part 21 is abutted on the piston upper part 71 when a second piston 10 moves to the top dead center side by the set maximum range or more. The conductive electrode member 21 is constituted so as to form an electrically closed circuit when the member 21 is abutted on the piston upper part 71 or the lower part 72 and detects that the first piston 7 or the second piston 10 moves to the top dead center side by the set maximum range or more.
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