In a fixed vane or rolling piston rotary compressor, the discharge port is in the motor end bearing. The discharge port is located such that about half of it overlies the piston bore and the remainder overlies the cylinder. The portion of the cylinder overlain by the discharge port is recessed to provide a fluid path from the cylinder bore to the discharge port. Accordingly, the discharge port faces the piston bore and recess. To provide a smooth flow path, the entrance to the discharge port is normally chamfered.
The discharge port is exposed to the compression chamber during the entire compression and discharge cycles. However, flow, other than that associated with the reduction in volume during the compression cycle, does not take place until the pressure in the compression chamber is sufficient to open the discharge valve against any bias and system pressure acting on the discharge valve and tending to keep it closed. It follows that there is normally a significant registration between the compression chamber and the discharge port at the time of opening of the discharge valve.