Scroll compressor having injection passage containing muffler

A scroll compressor, comprising:

• a housing including a suction port into which refrigerant is drawn and a discharge port out of which the refrigerant is discharged;
• a rotary shaft accommodated in the housing and supported by the housing to be rotatable about a rotation axis;
• and
• a compression mechanism accommodated in the housing, the compression mechanism including a fixed scroll fixed to the housing and a movable scroll configured to orbit as the rotary shaft rotates, wherein
• the compression mechanism includes a compression chamber configured to compress the refrigerant drawn when the fixed scroll meshes with the movable scroll,
• the housing includes an intermediate pressure chamber into which refrigerant having an intermediate pressure is introduced from an external refrigerant circuit, the intermediate pressure being higher than a suction pressure of the refrigerant drawn into the compression chamber and lower than a discharge pressure of the refrigerant discharged from the compression chamber,
• the intermediate pressure chamber and the compression chamber in a process of compression are connected to each other by an injection passage, and
• the injection passage includes a muffler,
• wherein
• the injection passage includes:
• an upstream passage that opens in the intermediate pressure chamber;
• a downstream passage that opens in the compression chamber;
• and
• an intermediate passage that connects the upstream passage to the downstream passage, and
• the muffler is defined by the intermediate passage, wherein the intermediate passage has a larger cross-sectional area than the upstream passage and the downstream passage,
• wherein
• the intermediate passage includes:
• a first intermediate passage connected to the upstream passage;
• and
• a second intermediate passage connected to the downstream passage,
• the fixed scroll includes:
• a fixed base plate;
• and
• a fixed volute wall arranged upright from the fixed base plate,
• the housing includes a facing surface facing an outer end surface of the fixed base plate, the outer end surface being an end surface on a side opposite to the fixed volute wall,
• the housing includes the upstream passage and the first intermediate passage,
• the first intermediate passage opens in the facing surface,
• the fixed base plate includes the second intermediate passage and the downstream passage,
• the second intermediate passage opens in the outer end surface, and
• the intermediate passage is defined by arranging the housing and the fixed scroll to bring the facing surface into contact with the outer end surface and connecting the first intermediate passage to the second intermediate passage.