Rotary compressor

1. A rotary compressor comprising:

a first cylinder;

a first piston that has a cylindrical shape, the first piston being configured to revolve along an inner wall surface of the first cylinder, and the first piston forming a first compression chamber configured to compress a fluid between the first piston and the inner wall surface of the first cylinder; and

a drive shaft that is rotatable, the drive shaft including:

a first eccentric portion that is eccentric in a first direction with respect to a rotational center axis and to which the first piston is fitted,

a first shaft portion that is rotatably supported by a first bearing formed on an end plate to close one end face of the first cylinder, and the first shaft portion having a cylindrical shape coaxial with the rotational center axis of the drive shaft,

a second shaft portion that is provided on a side opposite to the first shaft portion of the first eccentric portion in an axial direction, to which an electric motor that drives the drive shaft to rotate is coupled, and that has a cylindrical shape coaxial with the rotational center of the drive shaft, and

a first coupling portion that is formed radially within the end plate, when viewed in a direction perpendicular to the rotational center axis, and that couples the first shaft portion with the first eccentric portion,

the first shaft portion having a smaller diameter than the second shaft portion,

the drive shaft being configured to satisfy the following mathematical expression: R e1 −e 1 <R 1 , wherein R e1 is a radius of the first eccentric portion, R 1 is a radius of the first shaft portion, and e 1 is an eccentricity of the first eccentric portion, and

the first coupling portion being formed such that an outer surface thereof does not extend out of an outer surface of the first eccentric portion in a radial direction of the drive shaft, and the first coupling portion including a reinforcement portion with an outer surface thereof positioned outside an outer surface of the first shaft portion in the radial direction of the drive shaft.

2. The rotary compressor of claim 1 , further comprising:

a second cylinder; and

a second piston that has a cylindrical shape, the second piston being configured to revolve along an inner wall surface of the second cylinder, and the second piston forming a second compression chamber configured to compress a fluid between the second piston and the inner wall surface of the second cylinder,

a drive shaft that is rotatable, the drive shaft including

a second eccentric portion that is provided on a side opposite to the first coupling portion of the first eccentric portion in an axial direction, and the second eccentric portion being eccentric in a second direction opposite to the first direction with respect to the rotational center axis and to which the second piston is fitted, and

an intermediate coupling portion that couples the first eccentric portion with the second eccentric portion, and

the intermediate coupling portion including a first intermediate reinforcement portion that is formed in an area on the first direction side, disposed adjacent to the first eccentric portion, and the intermediate coupling portion having an outer surface positioned inside the outer surface of the first eccentric portion and positioned outside an outer surface of the second eccentric portion in the radial direction of the drive shaft.

3. The rotary compressor of claim 2 , wherein

the intermediate coupling portion further includes a second intermediate reinforcement portion that is formed in an area on the second direction side, disposed adjacent to the second eccentric portion, and the intermediate coupling portion has an outer surface positioned inside the outer surface of the second eccentric portion and positioned outside the outer surface of the first eccentric portion in the radial direction of the drive shaft.

4. The rotary compressor of claim 3 , wherein

in the intermediate coupling portion, the first intermediate reinforcement portion and the second intermediate reinforcement portion overlap with each other in the axial direction of the drive shaft, and

at least a part of the portion where the first intermediate reinforcement portion and the second intermediate reinforcement portion overlap with each other in the intermediate coupling portion in the axial direction of the drive shaft has a cylindrical shape coaxial with the rotational center axis of the drive shaft.

5. The rotary compressor of claim 2 , wherein

a second shaft portion continuously extends from a side of the second eccentric portion opposite to the intermediate coupling portion in the axial direction, and

the second shaft portion is rotationally supported by a second bearing formed on another end plate to close one end face of the second cylinder.

6. The rotary compressor of claim 5 , further comprising:

an intermediate end plate

that has a middle hole to allow the drive shaft to pass therethrough,

that blocks other ends of the first cylinder and the second cylinder between the first cylinder and the second cylinder, and

that is in sliding contact with other ends of the first piston and the second piston,

the first eccentric portion having a smaller diameter than the second eccentric portion.

7. The rotary compressor of claim 5 , wherein

the drive shaft is configured to satisfy the following mathematical expression: R e2 −e 2 ≥R 2 , wherein R e2 is a radius of the second eccentric portion, R 2 is a radius of the second shaft portion, and e 2 is an eccentricity of the second eccentric portion.