Check valve for compressor

A check valve for a compressor, comprising:

• a valve seat arranged on a refrigerant flow path of a compressor and having a valve hole through which a refrigerant passes;
• a valve element that is movable in a direction contacting with and leaving from said valve seat;
• a biasing member for biasing said valve element in a direction in which said valve element comes close to said valve seat;
• a valve housing in which a valve chamber in communication with said valve hole is formed and in which said valve element and said biasing member are accommodated;
• and
• a communicating window formed in a circumferential wall of said valve housing and forming a part of said refrigerant flow path, wherein
• said valve hole includes a small-diameter portion and a large-diameter portion provided more downstream than said small-diameter portion and having a flow path cross-sectional area larger than that of said small-diameter portion,
• said valve element includes an abutting surface for closing said large-diameter portion of said valve hole when said valve element is seated at said valve seat, and an outer circumferential surface guided by said circumferential wall and interrupting communication through said communicating window,
• said communicating window has such a shape that an opening area thereof gradually becomes larger with increasing distance from said valve seat,
• the check valve has an open state, a fully closed state, and a buffering state,
• when said abutting surface separates from said large-diameter portion of said valve hole and said outer circumferential surface opens said communicating window, the open state is defined,
• when said abutting surface closes said large-diameter portion of said valve hole and said outer circumferential surface interrupts communication through said communicating window, the fully closed state is defined, and
• when said abutting surface separates from said large-diameter portion of said valve hole and said outer circumferential surface interrupts communication through said communicating window, the buffering state is defined, wherein
• in the buffering state, a substantially closed space is formed by a part of an inner circumferential surface of said valve chamber, said valve element, and said valve seat, wherein said part of said inner circumferential surface of said valve chamber is devoid of apertures,
• said substantially closed space having a diameter that is larger than a diameter of said large-diameter portion,
• a first step surface is formed between said small-diameter portion and said large-diameter portion,
• a second step surface is formed between said large diameter portion and said substantially closed space,
• said substantially closed space being continuous with said large-diameter portion, and
• said substantially closed space and an interior space defined by said large-diameter portion together form a damper space.