Scroll compressor with valve for controlling fluid to flow from an outer wall to an inner wall of a fixed or a movable spiral wrap

A scroll-type refrigeration compressor comprising:

• a fixed scroll;
• and
• a movable scroll, whereby the movable scroll describes an orbital movement relative to the fixed scroll, the fixed and movable scrolls each being equipped with a spiral wrap, the two spiral wraps engaging each other and delimiting variable-volume compression chambers, only the spiral wrap of the movable scroll having a stepped portion extending over at least a portion of its length,
• wherein at least one of the scrolls has at least one passage designed to provide communication, during orbital movement of the movable scroll, between two compression chambers disposed symmetrically relative to the center of the orbital movement of the movable scroll, with the ends of the passage terminating on either side respectively of the outer and inner walls of the spiral wrap of the scroll with the passage or inside the outer and inner walls of the spiral wrap of the scroll with the passage, and
• wherein the passage has a check valve designed to allow fluid to flow only from the outer wall of the spiral wrap of the scroll with the passage to the inner wall thereof.