Linear expander and cryogenic refrigeration system including the same

A linear expander comprising:

• a body portion comprising a suction hole through which a fluid having a first pressure flows in, a discharge hole through which the fluid flows out with a second pressure that is lower than the first pressure, and first and second holes connecting an expansion space formed between the suction hole and the discharge hole;
• a first linear generating portion and a second linear generating portion comprising pistons respectively provided in the first hole and the second hole, the pistons being capable of linearly reciprocating to generate an induced electromotive force with an expansion force generated when the fluid having the first pressure expands to the fluid having the second pressure;
• a suction valve opening and closing the suction hole;
• and
• a discharge valve opening and closing the discharge hole,
• wherein the suction valve and the discharge valve configured to be opened when no external force is applied and closed when a pressure force from a pressure difference becomes greater than a predetermined value, and
• wherein the suction valve and the discharge valve are passive valves and respectively formed as reed valves,
• wherein the suction valve is configured to close to prevent inflow of the fluid having the first pressure when a pressure in the expansion space is reduced and thus a pressure difference between the outside of the suction hole and the expansion space is greater than a predetermined value, and
• the discharge valve is configured to open to let the fluid in the expansion space to flow out when the pressure in the expansion space is reduced and thus a pressure difference between the outside of the discharge hole and the expansion space is lower than a predetermined value,
• wherein the body portion includes a body member having the expansion space and a discharge hole connection member combined with the body member to form a space between the expansion space and the discharge hole,
• wherein the discharge hole connection member has a through-hole that forms the discharge hole, and
• wherein the discharge valve is provided on the discharge hole connection member at an end of the through-hole.