WE CLAIM:
[Claim 1]
An outdoor unit, comprising:
a casing including an air passage;
an outdoor fan disposed in the air passage;
a compressor disposed in the casing;
an outdoor heat exchanger disposed in the casing, the outdoor heat exchanger including fins and a heat transfer tube connected to the fins;
a control board disposed in the casing, the control board including a control unit configured to control the compressor; and
a heat sink disposed in the air passage in the casing, the heat sink being in contact with the control board,
the heat transfer tube of the outdoor heat exchanger including a first region in which gas refrigerant or two-phase gas-liquid refrigerant flows when the outdoor heat exchanger is used as a condenser and a second region that is located downstream of the first region in a refrigerant flow direction and in which single-phase liquid refrigerant flows,
the heat sink being disposed downstream of the outdoor heat exchanger in an air flow direction in the air passage,
the heat sink being located at a first distance from the first region and being located at a second distance from the second region, the second distance being shorter than the first distance. [Claim 2]
The outdoor unit of claim 1,
wherein the heat transfer tube in the first region includes first horizontal parts extending parallel to a horizontal plane,
wherein the heat transfer tube in the second region includes second horizontal parts extending parallel to the horizontal plane, and
wherein the second horizontal parts are less in number than are the first horizontal parts.

[Claim 3]
The outdoor unit of claim 1 or 2, wherein the heat sink is disposed above a lower end of the second region and below an upper end of the second region. [Claim 4]
The outdoor unit of any one of claims 1 to 3, wherein the second region is located in uppermost part of the outdoor heat exchanger. [Claim 5]
The outdoor unit of any one of claims 1 to 3, wherein the heat sink is located at a level identical with a level of a boss of the outdoor fan. [Claim 6]
The outdoor unit of any one of claims 1 to 5, wherein an air flow resistance in the second region is less than an air flow resistance in the first region. [Claim 7]
The outdoor unit of any one of claims 1 to 6,
wherein the fins include first fins to which the heat transfer tube in the first region is fixed and second fins to which the heat transfer tube in the second region is fixed, and
wherein the second fins are arranged at a pitch greater than a pitch of the first fins. [Claim 8]
The outdoor unit of any one of claims 1 to 7, further comprising
a shield that is plate-shaped and disposed under the heat sink. [Claim 9]
The outdoor unit of claim 8, wherein the shield is disposed at a level identical with a level of a lower end of the second region. [Claim 10]
The outdoor unit of any one of claims 1 to 9, further comprising:
a temperature sensor disposed at the heat sink; and
a flow switching device connected to the heat transfer tube and an expansion device configured to reduce a pressure of refrigerant,

wherein the flow switching device includes an inflow port connected to a most downstream portion of the heat transfer tube in the first region, a first outflow port connected to a most upstream portion of the heat transfer tube in the second region, and a second outflow port connected to the expansion device, and
wherein the control unit of the control board is configured to adjust the flow switching device on a basis of a temperature of the heat sink. [Claim 11]
The outdoor unit of claim 10, wherein, when a temperature of the heat sink is above a first reference temperature, the control unit of the control board is configured to close the first outflow port and open the second outflow port. [Claim 12]
The outdoor unit of claim 11, wherein, when a temperature of the heat sink is at or below the first reference temperature and is above a second reference temperature that is lower than the first reference temperature, the control unit of the control board is configured to open the first outflow port and the second outflow port. [Claim 13]
The outdoor unit of claim 12, wherein, when a temperature of the heat sink is at or below the second reference temperature, the control unit of the control board is configured to open the first outflow port and close the second outflow port. [Claim 14]
The outdoor unit of claim 11, wherein, when a temperature of the heat sink is at or below a second reference temperature that is lower than the first reference temperature, the control unit of the control board is configured to open the first outflow port and close the second outflow port.