Two-stage rotary compressor

A rotary compressor comprising:

• a motor;
• a rotation shaft coupled to the motor;
• a first compression unit comprising:
• a first cylinder attached to the rotation shaft, the first cylinder including a first refrigerant receiving space defined therein;
• a first roller rotatingly disposed in the first refrigerant receiving space to rotate integrally with the rotation shaft;
• and
• a plurality of first vanes inserted into the first roller in a retractable or extendable manner, wherein rotation of the first roller allows the first vanes to extend out of the first roller to contact an inner circumferential face of the first cylinder to divide a first compression space into a first suction chamber and a first compression chamber, wherein a number of the first vanes is N+2 and
• a second compression unit comprising:
• a second cylinder attached to the rotation shaft, the second cylinder including a second refrigerant receiving space defined therein;
• a second roller rotatingly disposed in the second refrigerant receiving space to rotate integrally with the rotation shaft;
• and
• a plurality of second vanes inserted into the second roller in a retractable or extendable manner, wherein rotation of the second roller allows the second vanes to extend out of the second roller to contact an inner circumferential face of the second cylinder to divide a second compression space into a second suction chamber and a second compression chamber, wherein a number of the second vanes is N+1,
• wherein N in the N+1 and N+2 is a same natural number, and
• wherein refrigerant compressed in and discharged out of the first compression unit applies a back pressure to the second vanes of the second compression unit to extend out of the second roller of the second compression unit.