Scroll expander

A scroll expander to which steam is supplied as a working medium, comprising:

• a driving scroll body that includes a pair of driving end plates and a driving wrap formed on each of the pair of driving end plates, and has a first axis line as a rotary shaft line;
• a driven scroll body that includes a driven end plate and a driven wrap formed on each of both surfaces of the driven end plate, is disposed between the pair of driving end plates, and has, as a rotary shaft line, a second axis line shifted with respect to the first axis line;
• a bearing plate that is disposed so as to interpose the driven scroll body, includes a pair of plates coupled to the driven scroll body, and has the second axis line as a rotary shaft line;
• a cylindrical driving pin that is attached to the driving scroll body, and protrudes from the driving end plate to the bearing plate;
• and
• a cylindrical guide ring that is attached to the bearing plate, and includes an inner diameter larger than an outer diameter of the driving pin, wherein
• a film including diamond-like carbon is formed on an outer circumferential surface of the driving pin in contact with an inner circumferential surface of the guide ring, and
• the inner circumferential surface of the guide ring includes a polymer resin material with self-lubricity.