To provide a reciprocating engine that prevents deterioration in cleanliness of exhaust gas due to knocking by suppressing the knocking by changing the piston structure.
The reciprocating engine 1 includes: a cylinder 2; and a piston 4 forming a combustion chamber 3 together with the cylinder 2 and having a top surface 4a. The reciprocating engine also includes: a recess 9 provided on the top surface 4a side of the piston 4 and communicating with the combustion chamber 3; an operation part 12 that is air-tightly arranged between the top surface 4a side and the bottom surface 9a side of the recess 9 in the recess 9, provided slidably between the top surface 4a side and the bottom surface 9a side, forming a volume varying chamber 17, communicating with the combustion chamber 3, on the top surface 4a side, and forming an auxiliary chamber 18 on the bottom surface 9a side; a flow passage 19 of the piston 4 provided outside the recess 9 and communicating the combustion chamber 3 and the auxiliary chamber 18 with each other; and a valve 23 provided in the flow passage 19 in order to close the flow passage 19 when the pressure inside the combustion chamber 3 exceeds the preset set pressure and to open the flow passage 19 when the pressure in the combustion chamber 3 becomes less than the set pressure.
Masatake Shiga
Kazuya Nishi
Hisanori Takahashi