Scroll compressor having a counterboring part communicating with an intermediate pressure chamber

A scroll compressor comprising:

• a fixed scroll disposed in a sealed vessel and provided with a plate-like spiral tooth on a base plate having a discharge port for a high-pressure refrigerant gas at a center;
• an orbiting scroll disposed in said sealed vessel and having a base plate provided with a plate-like spiral tooth engaging said plate-like spiral tooth of said fixed scroll for forming a compression space consisting of a high pressure chamber, an intermediate pressure chamber, and a low pressure chamber;
• and
• a counterboring part made in at least one of said base plates of said fixed and orbiting scrolls and having a cutaway part corresponding to a center of said plate-like spiral tooth of said base plate, and a portion of said counterboring part being formed into a shape of an involute curve, said involute curve substantially corresponding to a radially outer face of said plate like spiral tooth of the other of said base plates when the spiral tooth of the other of said base plates is at a position where said counterboring part begins to communicate with said intermediate pressure chamber, such that a communicating part of said counterboring part with said intermediate pressure chamber is formed over a wide range of said outer face.