Scroll type compressor

A scroll compressor comprising:

• a fixed scroll (2) and a movable scroll (4) for forming a compression chamber (16, 16a);
• a suction port (13) for sucking a fluid into said compression chamber (16, 16a);
• a discharge port (9) for discharging said fluid compressed in said compression chamber (16, 16a);
• an unloader part (11) for guiding said fluid from said compression chamber (16a) in the process of compression toward said suction port (13);
• control means (31) capable of operating said unloader part (11);
• and
• a first back pressure chamber (14) provided on the back surface of either said fixed scroll (2) or said movable scroll (4) for receiving said fluid, having a discharge pressure, discharged from said discharge port (9), wherein
• said control means (31) detects, calculates or predicts a suction pressure or said discharge pressure,
• compares separating force for separating said fixed scroll (2) and said movable scroll (4) from each other with pressing force for pressing one said scroll against another said scroll on the basis of detected, calculated or predicted said suction pressure and said discharge pressure, and
• operates said unloader part (11) when said pressing force is insufficient or to be insufficient with respect to said separating force for releasing said fluid from said compression chamber (16a) in the process of compression toward said suction port (13).