Variable compression device and engine system

A variable compression device that is configured to change a compression ratio in a combustion chamber of an engine, the variable compression device comprising:

• a piston rod;
• a first fluid chamber which is configured to move the piston rod in a direction in which a compression ratio is increased by supplying a pressurized working fluid thereto;
• a regulation member which is configured to regulate movement of the piston rod in a direction in which a compression ratio is increased;
• a second fluid chamber which is provided between the piston rod and the regulation member and is configured to store the working fluid;
• a supply flow path which is configured to guide the working fluid supplied to the second fluid chamber;
• a discharge flow path which is configured to guide the working fluid discharged from the second fluid chamber, a portion of the discharge flow path being formed in the regulation member;
• and
• a flow rate regulation unit which is provided in the discharge flow path and is configured to regulate a flow of the working fluid when the piston rod approaches the regulation member.