JP3894221B1 - Air conditioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress generation of refrigerant passing sound in an expansion valve, a use side heat exchanger or a refrigerant pipe from an expansion valve to a use side heat exchanger in an air conditioner.
An air conditioner includes a main refrigerant circuit having a compressor, a heat source side heat exchanger, a use side heat exchanger, and an expansion valve, and a part of refrigerant sent from the heat source side heat exchanger to the expansion valve. A bypass refrigerant circuit branched from the main refrigerant circuit and returned to the suction side of the compressor, a cooler for cooling the refrigerant sent from the heat source side heat exchanger to the expansion valve by the refrigerant flowing through the bypass refrigerant circuit, and the bypass refrigerant circuit And a control unit that controls the bypass expansion valve of the bypass refrigerant circuit so that the degree of superheat at the refrigerant outlet of the refrigerant becomes a predetermined value. The control unit performs control to close the bypass expansion valve until a predetermined time elapses when the outside air temperature is smaller than a predetermined outside air temperature at the time of starting the compressor or changing the number of operating heat exchangers. Do.
[Selection] Figure 7

Description

  The present invention relates to an air conditioner, and in particular, bypasses a part of the refrigerant flowing through the vapor compression main refrigerant circuit so as to return to the suction side of the compressor, and uses the bypassed refrigerant to flow through the main refrigerant circuit. It is related with the air conditioning apparatus comprised so that it could be in a supercooled state.

  Conventionally, a part of the refrigerant flowing through the main refrigerant circuit is bypassed so as to return to the suction side of the compressor, and the refrigerant flowing through the main refrigerant circuit can be brought into a supercooled state using the bypassed refrigerant. There is a configured air conditioner. Such an air conditioner mainly includes a main refrigerant circuit having a compressor, a heat source side heat exchanger, a use side heat exchanger, and an expansion valve, and a part of the refrigerant sent from the heat source side heat exchanger to the expansion valve. The refrigerant sent from the heat source side heat exchanger to the expansion valve is cooled by the bypass refrigerant circuit connected to the main refrigerant circuit so as to be branched from the main refrigerant circuit and returned to the suction side of the compressor, and the refrigerant flowing through the bypass refrigerant circuit And a cooler. The bypass refrigerant circuit has a bypass expansion valve that adjusts the flow rate of the refrigerant branched from the main refrigerant circuit. The cooler is connected to the main refrigerant circuit and the bypass refrigerant circuit so as to cool the refrigerant sent from the heat source side heat exchanger to the expansion valve by the refrigerant returned from the outlet of the bypass expansion valve to the suction side of the compressor. ing. The bypass expansion valve has a degree of superheat (hereinafter referred to as bypass refrigerant circuit-side superheat degree) at a cooler outlet of the refrigerant flowing through the bypass refrigerant circuit by a control unit that performs operation control of the air conditioner. (Hereinafter, referred to as a target superheat degree).

  In such an air conditioner, when performing a refrigeration cycle operation such as a cooling operation in which the heat source side heat exchanger functions as a refrigerant condenser and the use side heat exchanger functions as a refrigerant evaporator, A part of the refrigerant sent from the heat source side heat exchanger of the refrigerant circuit to the expansion valve is branched from the main refrigerant circuit and returned to the intake side of the compressor through the bypass refrigerant circuit while adjusting the flow rate by the bypass expansion valve. be able to. The refrigerant flowing from the bypass expansion valve outlet of the bypass refrigerant circuit toward the suction side of the compressor passes through the cooler and exchanges heat with the refrigerant sent from the heat source side heat exchanger to the expansion valve. Here, since the refrigerant after passing through the bypass expansion valve is lower than the temperature of the refrigerant sent from the heat source side heat exchanger of the main refrigerant circuit to the expansion valve, the refrigerant flows from the heat source side heat exchanger of the main refrigerant circuit to the expansion valve. The refrigerant sent to is cooled and heated. Further, since the bypass expansion valve is controlled by the control unit so that the degree of superheat on the bypass refrigerant circuit side becomes the target superheat degree, the refrigerant flowing through the bypass refrigerant circuit passes through the cooler and reaches the target superheat degree. After being heated to the corresponding outlet temperature, it is returned to the suction side of the compressor. Further, the refrigerant flowing through the main refrigerant circuit cooled in the cooler is cooled to a supercooling state corresponding to the amount of heat exchanged with the refrigerant flowing through the bypass refrigerant circuit in the cooler (hereinafter referred to as refrigerant flowing through the main refrigerant circuit). The degree of supercooling at the outlet of the cooler is the main refrigerant circuit side supercooling degree). The refrigerant cooled by the cooler is expanded to the vicinity of the evaporation pressure of the use side heat exchanger functioning as an evaporator in the expansion valve, becomes a gas-liquid two-phase state, and is sent to the use side heat exchanger. Thus, in this air conditioner, it is possible to perform superheat degree control (hereinafter referred to as bypass refrigerant circuit superheat degree control) such that the refrigerant flowing through the main refrigerant circuit is in a supercooled state.

Further, like the air conditioner of Patent Document 1, the target superheat degree when performing bypass refrigerant circuit superheat degree control is set to a value at which the compressor does not perform wet operation based on the discharge temperature of the compressor, that is, The main refrigerant circuit side subcooling degree may be configured to be as large as possible by setting the compressor so as to be as small as possible within a range where the compressor does not operate in a wet state.
JP 2005-69566 A

  However, when performing the above-described bypass circuit superheat degree control, the flow rate of the refrigerant flowing through the bypass refrigerant circuit is controlled so that the bypass refrigerant circuit side superheat degree becomes the target superheat degree. The degree varies depending on the operating conditions of the air conditioner. For this reason, when the compressor is started under a condition where the outside air temperature is low, cooling of the refrigerant in the heat source side heat exchanger is promoted, and the degree of supercooling of the refrigerant at the outlet of the heat source side heat exchanger is increased. Thus, since the refrigerant sent from the heat source side heat exchanger to the expansion valve is further cooled in the cooler, the degree of subcooling on the main refrigerant circuit side increases, and the refrigerant pressure after expansion in the expansion valve (that is, as an evaporator) Even under the condition of the functioning use side heat exchanger (evaporation pressure), the refrigerant may be in a gas-liquid two-phase state or a liquid single-phase state with a low dryness. And when starting a compressor, if such a refrigerant | coolant with a large supercooling degree of the main refrigerant circuit side flows into an expansion valve and a utilization side heat exchanger, although it is temporary, an expansion valve or a utilization side heat exchanger Or in the refrigerant | coolant piping from an expansion valve to a utilization side heat exchanger, the problem that a big refrigerant | coolant passage sound generate | occur | produces has arisen.

  In addition, it has a plurality of use side heat exchangers and a plurality of expansion valves corresponding to each of the plurality of use side heat exchangers, and the number of use side heat exchangers can be changed as necessary. In the case of a so-called multi-type air conditioner, when changing the number of operating heat exchangers in a condition where the outside air temperature is low, as in the case of starting the compressor in a condition where the outside air temperature is low. Since the degree of subcooling on the main refrigerant circuit side becomes large and the refrigerant pressure conditions after expansion in the expansion valve may become a refrigerant in a gas-liquid two-phase state or a liquid single-phase state with a low dryness, Although there is a problem, there is a problem that a large refrigerant passing sound is generated in the expansion valve, the use side heat exchanger or the refrigerant pipe from the expansion valve to the use side heat exchanger.

  Moreover, like the air conditioner of patent document 1, when setting the target superheat degree at the time of performing bypass refrigerant circuit superheat degree control to the value which a compressor does not become a wet operation based on the discharge temperature of a compressor. Since the operation is performed to increase the degree of subcooling on the main refrigerant circuit side as much as possible, the number of operating side heat exchangers is changed when the compressor is started under a low outside air temperature or when the outside air temperature is low. In this case, the degree of subcooling on the main refrigerant circuit side is further increased, and the refrigerant pressure condition after expansion in the expansion valve tends to be a gas-liquid two-phase or liquid single-phase refrigerant with a low dryness. In the refrigerant piping from the expansion valve, the use side heat exchanger or the expansion valve to the use side heat exchanger, a large refrigerant passing sound is likely to occur.

  An object of the present invention is to bypass a part of the refrigerant flowing through the main refrigerant circuit so as to return to the suction side of the compressor, and to make the refrigerant flowing through the main refrigerant circuit into a supercooled state using the bypassed refrigerant. In the air conditioner configured to be able to do so, it is intended to suppress generation of refrigerant passing sound in the refrigerant pipe from the expansion valve, the use side heat exchanger, or the expansion valve to the use side heat exchanger.

  An air conditioner according to a first aspect includes a main refrigerant circuit, a bypass refrigerant circuit, a cooler, and a control unit. The main refrigerant circuit has a compressor, a heat source side heat exchanger, a use side heat exchanger, and an expansion mechanism, and circulates the refrigerant in the order of the compressor, the heat source side heat exchanger, the expansion mechanism, and the use side heat exchanger. Thus, a refrigeration cycle operation in which the heat source side heat exchanger functions as a refrigerant condenser and the use side heat exchanger functions as a refrigerant evaporator is configured. The bypass refrigerant circuit is connected to the main refrigerant circuit so that a part of the refrigerant sent from the heat source side heat exchanger to the expansion mechanism is branched from the main refrigerant circuit and returned to the suction side of the compressor. It has a bypass expansion valve that adjusts the flow rate of the branched refrigerant. The cooler cools the refrigerant sent from the heat source side heat exchanger to the expansion mechanism by the refrigerant returned from the outlet of the bypass expansion valve to the suction side of the compressor. The control unit performs bypass refrigerant circuit superheat control for controlling the bypass expansion valve so that the bypass refrigerant circuit side superheat degree, which is the superheat degree at the refrigerant outlet of the refrigerant flowing through the bypass refrigerant circuit, becomes a predetermined superheat value. Do. Then, the control unit performs control to close the bypass expansion valve until a predetermined time elapses when the outside air temperature is smaller than a predetermined outside air temperature value when the compressor is started.

In this air conditioner, when the outside air temperature is lower than a predetermined outside air temperature when the compressor is started, the degree of supercooling at the cooler outlet of the refrigerant flowing through the main refrigerant circuit (hereinafter referred to as main refrigerant circuit side subcooling). The refrigerant after being expanded in the expansion mechanism becomes a gas-liquid two-phase state or a liquid single-phase state with a low dryness due to the excessive increase in the expansion mechanism. It can be determined that the refrigerant passage sound is generated in the refrigerant pipe from the condenser or the expansion mechanism to the use side heat exchanger (hereinafter referred to as refrigerant passage sound generation condition). In this air conditioner, when it is determined that the refrigerant passage sound generation condition is satisfied, the bypass expansion valve is closed until a predetermined time elapses, whereby the heat source side heat exchanger in the cooler is sent to the expansion mechanism. The refrigerant after being expanded in the expansion mechanism is in a gas-liquid two-phase state with a high degree of dryness, while suppressing the cooling of the refrigerant generated so that the degree of subcooling on the main refrigerant circuit side does not become excessively large Can do.
As a result, when starting the compressor, the refrigerant after being expanded in the expansion mechanism becomes a gas-liquid two-phase state or a liquid single-phase state with a low dryness, an expansion mechanism, a use side heat exchanger or Generation | occurrence | production of the refrigerant | coolant passage sound in refrigerant | coolant piping from an expansion mechanism to a utilization side heat exchanger can be suppressed.

  An air conditioner according to a second invention includes a main refrigerant circuit, a bypass refrigerant circuit, a cooler, and a control unit. The main refrigerant circuit has a compressor, a heat source side heat exchanger, a use side heat exchanger, and an expansion mechanism, and circulates the refrigerant in the order of the compressor, the heat source side heat exchanger, the expansion mechanism, and the use side heat exchanger. Thus, a refrigeration cycle operation in which the heat source side heat exchanger functions as a refrigerant condenser and the use side heat exchanger functions as a refrigerant evaporator is configured. The bypass refrigerant circuit is connected to the main refrigerant circuit so that a part of the refrigerant sent from the heat source side heat exchanger to the expansion mechanism is branched from the main refrigerant circuit and returned to the suction side of the compressor. It has a bypass expansion valve that adjusts the flow rate of the branched refrigerant. The cooler cools the refrigerant sent from the heat source side heat exchanger to the expansion mechanism by the refrigerant returned from the outlet of the bypass expansion valve to the suction side of the compressor. The control unit performs bypass refrigerant circuit superheat control for controlling the bypass expansion valve so that the bypass refrigerant circuit side superheat degree, which is the superheat degree at the refrigerant outlet of the refrigerant flowing through the bypass refrigerant circuit, becomes a predetermined superheat value. Do. Then, at the time of starting the compressor, the control unit has a main refrigerant circuit side subcooling degree that is a degree of supercooling at the cooler outlet of the refrigerant flowing through the main refrigerant circuit larger than a value of the first predetermined subcooling degree. In this case, the bypass expansion valve is closed until a predetermined time has elapsed.

In this air conditioner, when the main refrigerant circuit side supercooling degree, which is the degree of supercooling at the cooler outlet of the refrigerant flowing through the main refrigerant circuit at the time of starting the compressor, becomes larger than the first predetermined supercooling degree value The main refrigerant circuit side supercooling degree becomes excessively large, so that the refrigerant after being expanded in the expansion mechanism becomes a gas-liquid two-phase state or a liquid single-phase state with a low dryness, which causes expansion. It can be determined that the refrigerant passage sound is generated in the refrigerant pipe from the mechanism, the use side heat exchanger or the expansion mechanism to the use side heat exchanger (hereinafter referred to as refrigerant passage sound generation condition). . In this air conditioner, when it is determined that the refrigerant passage sound generation condition is satisfied, the bypass expansion valve is closed until a predetermined time elapses, whereby the heat source side heat exchanger in the cooler is sent to the expansion mechanism. The refrigerant after being expanded in the expansion mechanism is in a gas-liquid two-phase state with a high degree of dryness, while suppressing the cooling of the refrigerant generated so that the degree of subcooling on the main refrigerant circuit side does not become excessively large Can do.
As a result, when starting the compressor, the refrigerant after being expanded in the expansion mechanism becomes a gas-liquid two-phase state or a liquid single-phase state with a low dryness, an expansion mechanism, a use side heat exchanger or Generation | occurrence | production of the refrigerant | coolant passage sound in refrigerant | coolant piping from an expansion mechanism to a utilization side heat exchanger can be suppressed.

  An air conditioner according to a third invention includes a main refrigerant circuit, a bypass refrigerant circuit, a cooler, and a control unit. The main refrigerant circuit has a compressor, a heat source side heat exchanger, a use side heat exchanger, and an expansion mechanism, and circulates the refrigerant in the order of the compressor, the heat source side heat exchanger, the expansion mechanism, and the use side heat exchanger. Thus, a refrigeration cycle operation in which the heat source side heat exchanger functions as a refrigerant condenser and the use side heat exchanger functions as a refrigerant evaporator is configured. The bypass refrigerant circuit is connected to the main refrigerant circuit so that a part of the refrigerant sent from the heat source side heat exchanger to the expansion mechanism is branched from the main refrigerant circuit and returned to the suction side of the compressor. It has a bypass expansion valve that adjusts the flow rate of the branched refrigerant. The cooler cools the refrigerant sent from the heat source side heat exchanger to the expansion mechanism by the refrigerant returned from the outlet of the bypass expansion valve to the suction side of the compressor. The control unit performs bypass refrigerant circuit superheat control for controlling the bypass expansion valve so that the bypass refrigerant circuit side superheat degree, which is the superheat degree at the refrigerant outlet of the refrigerant flowing through the bypass refrigerant circuit, becomes a predetermined superheat value. Do. Then, at the time of starting the compressor, the control unit has a main refrigerant circuit side subcooling degree that is a degree of supercooling at the cooler outlet of the refrigerant flowing through the main refrigerant circuit larger than a value of the first predetermined subcooling degree. In this case, the bypass expansion valve is controlled to be closed until the main refrigerant circuit side supercooling degree becomes equal to or less than the second predetermined supercooling degree.

In this air conditioner, when the main refrigerant circuit side supercooling degree, which is the degree of supercooling at the cooler outlet of the refrigerant flowing through the main refrigerant circuit at the time of starting the compressor, becomes larger than the first predetermined supercooling degree value The main refrigerant circuit side supercooling degree becomes excessively large, so that the refrigerant after being expanded in the expansion mechanism becomes a gas-liquid two-phase state or a liquid single-phase state with a low dryness, which causes expansion. It can be determined that the refrigerant passage sound is generated in the refrigerant pipe from the mechanism, the use side heat exchanger or the expansion mechanism to the use side heat exchanger (hereinafter referred to as refrigerant passage sound generation condition). . In this air conditioner, when it is determined that the refrigerant passage noise generation condition is satisfied, the bypass expansion valve is closed until the main refrigerant circuit side subcooling degree is equal to or lower than the second predetermined supercooling degree value. Thus, the cooling of the refrigerant sent from the heat source side heat exchanger in the cooler to the expansion mechanism is suppressed, and the refrigerant after being expanded in the expansion mechanism is dried so that the degree of subcooling on the main refrigerant circuit side is not excessively increased. It is possible to perform an operation that results in a gas-liquid two-phase state having a high degree.
As a result, when starting the compressor, the refrigerant after being expanded in the expansion mechanism becomes a gas-liquid two-phase state or a liquid single-phase state with a low dryness, an expansion mechanism, a use side heat exchanger or Generation | occurrence | production of the refrigerant | coolant passage sound in refrigerant | coolant piping from an expansion mechanism to a utilization side heat exchanger can be suppressed.

  An air conditioner according to a fourth aspect of the present invention includes a main refrigerant circuit, a bypass refrigerant circuit, a cooler, and a control unit. The main refrigerant circuit has a compressor, a heat source side heat exchanger, a plurality of usage side heat exchangers, and a plurality of expansion mechanisms corresponding to the plurality of usage side heat exchangers. Refrigeration cycle in which the heat source side heat exchanger functions as a refrigerant condenser and the usage side heat exchanger functions as a refrigerant evaporator by circulating the refrigerant in the order of the condenser, the expansion mechanism, and the usage side heat exchanger Operation is possible. The bypass refrigerant circuit is connected to the main refrigerant circuit so that a part of the refrigerant sent from the heat source side heat exchanger to the expansion mechanism is branched from the main refrigerant circuit and returned to the suction side of the compressor. It has a bypass expansion valve that adjusts the flow rate of the branched refrigerant. The cooler cools the refrigerant sent from the heat source side heat exchanger to the expansion mechanism by the refrigerant returned from the outlet of the bypass expansion valve to the suction side of the compressor. The control unit performs bypass refrigerant circuit superheat control for controlling the bypass expansion valve so that the bypass refrigerant circuit side superheat degree, which is the superheat degree at the refrigerant outlet of the refrigerant flowing through the bypass refrigerant circuit, becomes a predetermined superheat value. Do. And a control part performs control which closes a bypass expansion valve until predetermined time passes, when outside temperature is smaller than the value of predetermined outside air temperature at the time of change of the number of operation of a use side heat exchanger.

In this air conditioner, when the outside air temperature is smaller than a predetermined outside air temperature when the number of operating side heat exchangers is changed, the degree of supercooling (hereinafter, The refrigerant after being expanded in the expansion mechanism becomes a gas-liquid two-phase state or a liquid single-phase state with a low dryness due to an excessively large main refrigerant circuit side supercooling degree). It can be determined that the refrigerant passage sound is generated in the refrigerant pipe from the mechanism, the use side heat exchanger or the expansion mechanism to the use side heat exchanger (hereinafter referred to as refrigerant passage sound generation condition). . In this air conditioner, when it is determined that the refrigerant passage sound generation condition is satisfied, the bypass expansion valve is closed until a predetermined time elapses, whereby the heat source side heat exchanger in the cooler is sent to the expansion mechanism. The refrigerant after being expanded in the expansion mechanism is in a gas-liquid two-phase state with a high degree of dryness, while suppressing the cooling of the refrigerant generated so that the degree of subcooling on the main refrigerant circuit side does not become excessively large Can do.
Thereby, when changing the number of operating side heat exchangers, the expansion mechanism caused by the refrigerant after being expanded in the expansion mechanism becomes a gas-liquid two-phase state or a liquid single-phase state with a low dryness, Generation | occurrence | production of the refrigerant | coolant passage sound in refrigerant | coolant piping from a use side heat exchanger or an expansion mechanism to a use side heat exchanger can be suppressed.

  An air conditioner according to a fifth aspect of the present invention includes a main refrigerant circuit, a bypass refrigerant circuit, a cooler, and a control unit. The main refrigerant circuit has a compressor, a heat source side heat exchanger, a plurality of usage side heat exchangers, and a plurality of expansion mechanisms corresponding to the plurality of usage side heat exchangers. Refrigeration cycle in which the heat source side heat exchanger functions as a refrigerant condenser and the usage side heat exchanger functions as a refrigerant evaporator by circulating the refrigerant in the order of the condenser, the expansion mechanism, and the usage side heat exchanger Operation is possible. The bypass refrigerant circuit is connected to the main refrigerant circuit so that a part of the refrigerant sent from the heat source side heat exchanger to the expansion mechanism is branched from the main refrigerant circuit and returned to the suction side of the compressor. It has a bypass expansion valve that adjusts the flow rate of the branched refrigerant. The cooler cools the refrigerant sent from the heat source side heat exchanger to the expansion mechanism by the refrigerant returned from the outlet of the bypass expansion valve to the suction side of the compressor. The control unit performs bypass refrigerant circuit superheat control for controlling the bypass expansion valve so that the bypass refrigerant circuit side superheat degree, which is the superheat degree at the refrigerant outlet of the refrigerant flowing through the bypass refrigerant circuit, becomes a predetermined superheat value. Do. Then, when the number of operating side heat exchangers is changed, the control unit is configured such that the main refrigerant circuit side subcooling degree, which is the subcooling degree at the cooler outlet of the refrigerant flowing through the main refrigerant circuit, is the first predetermined subcooling degree. When the value is larger than the value, control for closing the bypass expansion valve is performed until a predetermined time elapses.

In this air conditioner, the main refrigerant circuit side subcooling degree, which is the degree of supercooling at the cooler outlet of the refrigerant flowing through the main refrigerant circuit when the number of operating side heat exchangers in operation is changed, is the first predetermined subcooling degree value. Is larger than the main refrigerant circuit side supercooling degree becomes excessively large, the refrigerant after being expanded in the expansion mechanism becomes a gas-liquid two-phase state or a liquid single-phase state with a low dryness, This is a condition that causes refrigerant passage sound in the expansion mechanism, the use side heat exchanger or the refrigerant pipe from the expansion mechanism to the use side heat exchanger (hereinafter referred to as refrigerant passage sound generation condition). Can be determined. In this air conditioner, when it is determined that the refrigerant passage sound generation condition is satisfied, the bypass expansion valve is closed until a predetermined time elapses, whereby the heat source side heat exchanger in the cooler is sent to the expansion mechanism. The refrigerant after being expanded in the expansion mechanism is in a gas-liquid two-phase state with a high degree of dryness, while suppressing the cooling of the refrigerant generated so that the degree of subcooling on the main refrigerant circuit side does not become excessively large Can do.
Thereby, when changing the number of operating side heat exchangers, the expansion mechanism caused by the refrigerant after being expanded in the expansion mechanism becomes a gas-liquid two-phase state or a liquid single-phase state with a low dryness, Generation | occurrence | production of the refrigerant | coolant passage sound in refrigerant | coolant piping from a use side heat exchanger or an expansion mechanism to a use side heat exchanger can be suppressed.

  An air conditioner according to a sixth aspect of the present invention includes a main refrigerant circuit, a bypass refrigerant circuit, a cooler, and a control unit. The main refrigerant circuit has a compressor, a heat source side heat exchanger, a plurality of usage side heat exchangers, and a plurality of expansion mechanisms corresponding to the plurality of usage side heat exchangers. Refrigeration cycle in which the heat source side heat exchanger functions as a refrigerant condenser and the usage side heat exchanger functions as a refrigerant evaporator by circulating the refrigerant in the order of the condenser, the expansion mechanism, and the usage side heat exchanger Operation is possible. The bypass refrigerant circuit is connected to the main refrigerant circuit so that a part of the refrigerant sent from the heat source side heat exchanger to the expansion mechanism is branched from the main refrigerant circuit and returned to the suction side of the compressor. It has a bypass expansion valve that adjusts the flow rate of the branched refrigerant. The cooler cools the refrigerant sent from the heat source side heat exchanger to the expansion mechanism by the refrigerant returned from the outlet of the bypass expansion valve to the suction side of the compressor. The control unit performs bypass refrigerant circuit superheat control for controlling the bypass expansion valve so that the bypass refrigerant circuit side superheat degree, which is the superheat degree at the refrigerant outlet of the refrigerant flowing through the bypass refrigerant circuit, becomes a predetermined superheat value. Do. Then, when the number of operating side heat exchangers is changed, the control unit is configured such that the main refrigerant circuit side subcooling degree, which is the subcooling degree at the cooler outlet of the refrigerant flowing through the main refrigerant circuit, is the first predetermined subcooling degree. When the value becomes larger than this value, the bypass expansion valve is controlled to be closed until the main refrigerant circuit side subcooling degree becomes equal to or less than the second predetermined supercooling degree value.

In this air conditioner, the main refrigerant circuit side subcooling degree, which is the degree of supercooling at the cooler outlet of the refrigerant flowing through the main refrigerant circuit when the number of operating side heat exchangers in operation is changed, is the first predetermined subcooling degree value. Is larger than the main refrigerant circuit side supercooling degree becomes excessively large, the refrigerant after being expanded in the expansion mechanism becomes a gas-liquid two-phase state or a liquid single-phase state with a low dryness, This is a condition that causes refrigerant passage sound in the expansion mechanism, the use side heat exchanger or the refrigerant pipe from the expansion mechanism to the use side heat exchanger (hereinafter referred to as refrigerant passage sound generation condition). Can be determined. In this air conditioner, when it is determined that the refrigerant passage noise generation condition is satisfied, the bypass expansion valve is closed until the main refrigerant circuit side subcooling degree is equal to or lower than the second predetermined supercooling degree value. Thus, the cooling of the refrigerant sent from the heat source side heat exchanger in the cooler to the expansion mechanism is suppressed, and the refrigerant after being expanded in the expansion mechanism is dried so that the degree of subcooling on the main refrigerant circuit side is not excessively increased. It is possible to perform an operation that results in a gas-liquid two-phase state having a high degree.
Thereby, when changing the number of operating side heat exchangers, the expansion mechanism caused by the refrigerant after being expanded in the expansion mechanism becomes a gas-liquid two-phase state or a liquid single-phase state with a low dryness, Generation | occurrence | production of the refrigerant | coolant passage sound in refrigerant | coolant piping from a use side heat exchanger or an expansion mechanism to a use side heat exchanger can be suppressed.

An air conditioner according to a seventh aspect is the air conditioner according to any of the second, third, fifth, and sixth aspects, wherein the first predetermined supercooling value is set as a function of the outside air temperature. The
In this air conditioner, it is possible to determine an appropriate refrigerant passing sound generation condition according to the outside air temperature condition.

  An air conditioner according to an eighth aspect of the present invention is the air conditioner according to any of the first to seventh aspects of the invention, wherein the predetermined superheat value is based on the discharge temperature of the compressor and the compressor is in a damp operation. Set to a value that must not be.

  In this air conditioner, by setting the value of the predetermined superheat degree, which is the target superheat degree when performing bypass refrigerant circuit superheat degree control, to a value at which the compressor does not perform wet operation based on the discharge temperature of the compressor, Since the operation is performed to increase the degree of supercooling on the main refrigerant circuit side as much as possible, it tends to become a gas-liquid two-phase state or a liquid single-phase state with a low dryness under the condition of the refrigerant pressure after expansion in the expansion valve. It is easy to become a condition for generating refrigerant passing sound.

  However, even in the case of performing such bypass refrigerant circuit superheat degree control, by performing determination of the refrigerant passing sound generation condition and control for closing the bypass expansion valve as in any of the first to seventh inventions. The refrigerant after being expanded in the expansion mechanism reaches the utilization side heat exchanger from the expansion mechanism, the utilization side heat exchanger or the expansion mechanism resulting from the gas-liquid two-phase state or the liquid single-phase state having a low dryness. Generation | occurrence | production of the refrigerant | coolant passage sound in the refrigerant | coolant piping until can be suppressed.

As described above, according to the present invention, the following effects can be obtained.
In 1st-3rd invention, when starting a compressor, the expansion mechanism resulting from the refrigerant | coolant after being expanded in an expansion mechanism being in the gas-liquid two-phase state or liquid single-phase state with small dryness Generation | occurrence | production of the refrigerant | coolant passage sound in refrigerant | coolant piping from a side heat exchanger or an expansion mechanism to a utilization side heat exchanger can be suppressed.

In the fourth to sixth inventions, when the number of operating side heat exchangers is changed, the refrigerant after being expanded in the expansion mechanism is in a gas-liquid two-phase state or a liquid single-phase state with a low dryness. It is possible to suppress the occurrence of refrigerant passing sound in the refrigerant piping from the expansion mechanism, the use side heat exchanger or the expansion mechanism to the use side heat exchanger.
In the seventh aspect of the invention, it is possible to determine an appropriate refrigerant passing sound generation condition according to the outside air temperature condition.

  In the eighth aspect of the invention, the refrigerant after being expanded in the expansion mechanism is in a gas-liquid two-phase state or liquid in which the degree of dryness is small even though the bypass refrigerant circuit superheat degree control that is likely to cause the refrigerant passing sound generation condition is performed. Generation | occurrence | production of the refrigerant | coolant passage sound in the refrigerant | coolant piping from the expansion mechanism resulting from becoming a single phase state to the utilization side heat exchanger from the expansion mechanism or utilization side heat exchanger can be suppressed.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of an air conditioner according to the present invention will be described with reference to the drawings.
(1) Configuration of Air Conditioner FIG. 1 is a schematic refrigerant circuit diagram of an air conditioner 1 as an embodiment of the present invention. The air conditioner 1 is a so-called multi-type air in which a plurality of (three in this embodiment) usage units 5a to 5c are connected to one or more (in this embodiment, one) heat source unit 2. It is a harmony device, and is used, for example, for cooling and heating a plurality of air-conditioned spaces in a building. The utilization units 5 a to 5 c are connected to the heat source unit 2 via the branch unit 6. More specifically, the utilization units 5a to 5c are connected to the branch unit 6 via the liquid refrigerant branch pipes 7a to 7c and the gas refrigerant branch pipes 8a to 8c, respectively. The branch unit 6 is connected to the heat source unit 2 via the liquid refrigerant communication pipe 7d and the gas refrigerant communication pipe 8d.

(2) Configuration of Usage Units Each usage unit 5a to 5c mainly includes usage-side heat exchangers 51a to 51c, and is installed in a building, for example. Each use side heat exchanger 51a-51c is a heat exchanger for exchanging heat with room air. In this embodiment, each utilization unit 5a-5c has indoor fans 52a-52c for taking in and sending out indoor air into the unit, and refrigerant flowing through the indoor air and utilization-side heat exchangers 51a-51c. It is possible to perform heat exchange.

(3) Configuration of the branch unit The branch unit 6 sends the refrigerant sent from the heat source unit 2 to each of the plurality of usage units 5a to 5c, and also joins the refrigerant sent from the usage units 5a to 5c. This is a unit for sending to 2. In the air conditioning apparatus 1, the three usage units 5 a to 5 c are connected to the branch unit 6, but more usage units or fewer usage units may be connected. A plurality of branch units may be connected to the heat source unit 2.

  The branch unit 6 mainly has a liquid side branch pipe 61 and a gas side branch pipe 62 in the present embodiment. The liquid side branch pipe 61 includes a liquid side junction 61d connected to the liquid refrigerant communication pipe 7d and a plurality (three in this embodiment) of liquid side branch 61a branched in parallel from the liquid side junction 61d. ~ 61c. Each liquid side branch part 61a-61c is connected to utilization unit 5a-5c via liquid refrigerant branch piping 7a-7c. Use side expansion valves 63a to 63c are provided in the liquid side branch portions 61a to 61c, respectively. Each of the usage-side expansion valves 63a to 63c is an electric expansion valve that functions as an expansion mechanism that adjusts the flow rate of the refrigerant flowing through the usage-side heat exchangers 51a to 51c of the usage units 5a to 5c. The gas side branch pipe 62 includes a gas side junction 62d connected to the gas refrigerant communication pipe 8d, and a plurality (three in this embodiment) of gas side branch 62a branched in parallel from the gas side junction 62d. ~ 62c. Each gas side branch part 62a-62c is connected to utilization unit 5a-5c via gas refrigerant branch piping 8a-8c.

(4) Configuration of Heat Source Unit The heat source unit 2 mainly includes a compressor 21, an oil separator 22, a four-way switching valve 23, a heat source side heat exchanger 24, a heat source side expansion valve 25, and a bridge circuit 26. A receiver 27, a cooler 28, a subcooling bypass refrigerant circuit 41, a liquid side closing valve 29, a gas side closing valve 30, and a refrigerant pipe connecting them, for example, a building It is installed outside.

The compressor 21 is a device for compressing the gas refrigerant. In this embodiment, the compressor 21 is a positive displacement compressor that is driven by a motor controlled by an inverter, and can vary the operating capacity. The compressor 21 is a so-called hermetic compressor in which the motor is built in the casing.
The oil separator 22 is a device for separating refrigeration oil accompanying the gas refrigerant compressed and discharged in the compressor 21, and is connected to the discharge side of the compressor 21. The oil separator 22 is provided with an oil return circuit 31 that returns the separated refrigeration oil to the suction side of the compressor 21. The oil return circuit 31 mainly includes an oil return pipe 31a and a capillary tube 31b provided in the oil return pipe 31a. The capillary tube 31b is a capillary tube for decompressing the refrigeration oil from the oil separator 22 toward the suction side of the compressor 21 via the oil return pipe 31a.

  The four-way switching valve 23 functions as a switching mechanism that switches the direction of the refrigerant flow when switching between cooling operation and heating operation. During the cooling operation, the four-way switching valve 23 is a discharge side (specifically, an oil separator). 22) and the gas side of the heat source side heat exchanger 24 and the suction side of the compressor 21 and the gas side shut-off valve 30 are connected (see the solid line of the four-way switching valve 23 in FIG. In the heating operation, the discharge side of the compressor 21 (specifically, the oil separator 22) and the gas side shut-off valve 30 are connected and the suction side and the heat source side heat exchanger of the compressor 21 are connected. It is possible to connect the gas side of 24 (refer to the broken line of the four-way switching valve 23 in FIG. 1, hereinafter referred to as the heating operation switching state).

The heat source side heat exchanger 24 is a device for exchanging heat with refrigerant using outdoor air as a heat source, and the gas side thereof is connected to the four-way switching valve 23. In the present embodiment, the heat source unit 2 includes an outdoor fan 32 for taking in and sending outdoor air into the unit, and heat exchange between the outdoor air and the refrigerant flowing through the heat source side heat exchanger 24 can be performed. Is possible.
The heat source side expansion valve 25 is a refrigerant that flows between the heat source side heat exchanger 24 and the branch unit 6 (specifically, the use side expansion valves 63a to 63c of the branch unit 6) via the liquid refrigerant communication pipe 7d. This is an electric expansion valve for adjusting the flow rate and the like, and is connected to the liquid side of the heat source side heat exchanger 24.

  The receiver 27 temporarily passes the refrigerant flowing between the heat source side heat exchanger 24 and the branch unit 6 (specifically, the use side expansion valves 63a to 63c of the branch unit 6) via the liquid refrigerant communication pipe 7d. It is a container for storing. The receiver 27 has an inlet at the upper part of the container and an outlet at the lower part of the container. The inlet of the receiver 27 is connected to the heat source side expansion valve 25 and the liquid side closing valve 29 via the bridge circuit 26. The outlet of the receiver 27 is connected to the heat source side expansion valve 25 and the liquid side closing valve 29 via the cooler 28 and the bridge circuit 26.

  The bridge circuit 26 is a circuit composed of four check valves 26a to 26d connected between the heat source side expansion valve 25 and the receiver 27, and the heat source side heat exchanger 24 via the liquid refrigerant communication pipe 7d. And the branch unit 6 (specifically, the use side expansion valves 63a to 63c of the branch unit 6) when the refrigerant flows into the receiver 27 from the heat source side heat exchanger 24 side and the receiver from the branch unit 6 side. In any case, the refrigerant flows into the receiver 27 from the inlet of the receiver 27, and the heat source side heat exchanger 24 and the branch unit 6 (specifically, the liquid is supplied from the outlet of the receiver 27). It has a function of returning the refrigerant to and from the side closing valve 29). Specifically, the check valve 26 a is connected to guide the refrigerant flowing from the branch unit 6 toward the heat source side heat exchanger 24 to the inlet of the receiver 27. The check valve 26 b is connected to guide the refrigerant flowing from the heat source side heat exchanger 24 toward the branch unit 6 to the inlet of the receiver 27. The check valve 26 c is connected so that the refrigerant flowing from the outlet of the receiver 27 through the cooler 28 can flow to the branch unit 6 side. The check valve 26d is connected so that the refrigerant flowing from the outlet of the receiver 27 through the cooler 28 can flow to the heat source side heat exchanger 24 side. Thereby, the refrigerant flowing between the heat source side heat exchanger 24 and the branch unit 6 (specifically, the use side expansion valves 63a to 63c of the branch unit 6) via the liquid refrigerant communication pipe 7d is always received by the receiver. 27 flows in from the inlet 27 and flows out from the outlet of the receiver 27 and is returned between the heat source side heat exchanger 24 and the branch unit 6 (specifically, the liquid side closing valve 29).

The liquid side closing valve 29 is connected to the liquid refrigerant communication pipe 7d. That is, the liquid refrigerant communication pipe 7 d connects between the branch unit 6 and the liquid side closing valve 29.
The gas side closing valve 30 is connected to the gas refrigerant communication pipe 8d. In other words, the gas refrigerant communication pipe 8 d connects between the branch unit 6 and the gas side shut-off valve 30.
The compressor 21, the oil separator 22, the four-way switching valve 23, the heat source side heat exchanger 24, the heat source side expansion valve 25, the bridge circuit 26, the receiver 27, the liquid side closing valve 29, and the use side expansion described above. The refrigerant circuit to which the valves 63 a to 63 c, the use side heat exchangers 51 a to 51 c and the gas side closing valve 30 are connected is referred to as the main refrigerant circuit 10 of the air conditioner 1.

Next, the cooler 28 and the subcooling bypass refrigerant circuit 41 will be described.
The cooler 28 is a device for cooling the refrigerant condensed in the heat source side heat exchanger 24 and sent to the branch unit 6 (specifically, the use side expansion valves 63a to 63c of the branch unit 6). In the embodiment, a double-tube heat exchanger. In the present embodiment, the cooler 28 is provided between the receiver 27 and the bridge circuit 26 (specifically, check valves 26c and 26d).

  The subcooling bypass refrigerant circuit 41 transfers a part of the refrigerant sent from the heat source side heat exchanger 24 to the branch unit 6 (specifically, the use side expansion valves 63a to 63c of the branch unit 6) from the main refrigerant circuit 10. The main refrigerant circuit 10 is connected so as to be branched and returned to the suction side of the compressor 21. Specifically, the subcooling bypass refrigerant circuit 41 mainly includes a cooler inlet pipe 41a and a cooler outlet pipe 41b. The cooler inlet pipe 41a is from a circuit portion that connects the outlet of the receiver 27 and the check valves 26c and 26d of the bridge circuit 26 (in this embodiment, a circuit portion that connects the outlet of the receiver 27 and the cooler 28). The refrigerant pipe is branched and connected to the cooler 28. The cooler outlet pipe 41 b is a refrigerant pipe connected to the suction pipe 33 of the compressor 21 in order to return from the cooler 28 to the suction side of the compressor 21. The cooler inlet pipe 41 a is provided with a bypass expansion valve 42 for adjusting the flow rate of the refrigerant flowing through the subcooling bypass refrigerant circuit 41. Here, the bypass expansion valve 42 is an electric expansion valve for adjusting the flow rate of the refrigerant flowing to the cooler 28. Accordingly, the refrigerant flowing between the heat source side heat exchanger 24 of the main refrigerant circuit 10 and the branch unit 6 (specifically, the use side expansion valves 63a to 63c of the branch unit 6) is bypassed in the cooler 28. The refrigerant is cooled by the refrigerant returned from the outlet of the expansion valve 42 to the suction side of the compressor 21.

The cooler 28 is a heat exchanger having a flow path that flows so that the refrigerant that flows on the main refrigerant circuit 10 side and the refrigerant that flows on the subcooling bypass refrigerant circuit 41 side face each other. Specifically, as shown in FIG. 2, the cooler 28 has a first end connected to the receiver 27 and the other end connected to the bridge circuit 26 so that the refrigerant flowing through the main refrigerant circuit 10 side passes through the first. The pipe part 28a and the first pipe part 28a are arranged so as to cover the outer periphery, one end is connected to the bypass expansion valve 42 and the other end is connected to the suction pipe 33 and flows through the subcooling bypass refrigerant circuit 41 side. And a second pipe portion 28b through which the refrigerant passes. The inlet side end portion 28c on the side connected to the receiver 27 of the first pipe portion 28a is disposed so as to correspond to the outlet side end portion 28d on the side connected to the suction pipe 33 of the second pipe portion 28b. ing. Further, the outlet side end portion 28e on the side connected to the bridge circuit 26 of the first pipe portion 28a corresponds to the inlet side end portion 28f on the side connected to the bypass expansion valve 42 of the second pipe portion 28b. Is arranged. As a result, the refrigerant flowing on the main refrigerant circuit 10 side (see arrow F _{1 in} FIG. 2) and the refrigerant flowing on the subcooling bypass refrigerant circuit 41 side (see arrow F _{2 in} FIG. 2) flow so as to face each other. Therefore, the refrigerant flowing through the main refrigerant circuit 10 can be cooled to a temperature lower than the outlet temperature of the refrigerant flowing through the subcooling bypass refrigerant circuit 41.

(5) Configuration of Sensors and Control Unit Furthermore, the air conditioning apparatus 1 controls each device based on sensors such as pressure sensors and temperature sensors provided in each unit and signals detected by these sensors. And a control unit 9 for performing a refrigeration cycle operation such as a cooling operation and a heating operation (see FIG. 3). Next, the sensors and the control unit 9 will be described.

  First, sensors such as a pressure sensor and a temperature sensor provided in the air conditioner 1 will be described with reference to FIG. The suction pipe 33 of the compressor 21 is provided with a low-pressure refrigerant pressure sensor LP as a pressure detection mechanism for detecting the pressure of the low-pressure gas refrigerant flowing on the suction side of the compressor 21. The discharge pipe 34 of the compressor 21 is provided with a high-pressure refrigerant pressure sensor HP as a pressure detection mechanism for detecting the pressure of the high-pressure gas refrigerant flowing on the discharge side of the compressor 21. The discharge pipe 34 of the compressor 21 is provided with a high pressure switch HPS for detecting an excessive increase in the pressure of the high pressure gas refrigerant.

  The discharge pipe 34 of the compressor 21 is provided with a high-pressure refrigerant temperature sensor Td as a temperature detection mechanism for detecting the discharge temperature of the refrigerant on the discharge side of the compressor 21. The suction pipe 33 of the compressor 21 is provided with a low-pressure refrigerant temperature sensor Ts as a temperature detection mechanism for detecting the suction temperature of the refrigerant on the suction side of the compressor 21. Further, an outdoor air temperature sensor Ta as a temperature detection mechanism for detecting the temperature of the outdoor air is provided at the air intake port of the outdoor fan 32 of the heat source unit 2. The heat source side heat exchanger 24 has a heat source side heat exchange temperature as a temperature detection mechanism for detecting the refrigerant temperature corresponding to the refrigerant condensation temperature during the cooling operation and the refrigerant evaporation temperature during the heating operation. A sensor Tb is provided. The cooler outlet pipe 41b of the supercooling bypass refrigerant circuit 41 has a cooler outlet bypass as a temperature detection mechanism for detecting the temperature of the refrigerant at the outlet of the cooler 28 flowing through the supercooling bypass refrigerant circuit 41. A refrigerant temperature sensor Tsh is provided.

  In addition, indoor air sensors Tra to Trc as temperature detecting mechanisms for detecting the temperature of the indoor air are provided at the air suction ports of the indoor fans 52a to 52c of the respective usage units 5a to 5c. Each of the use side heat exchangers 51a to 51c includes use side heat exchanger intermediate temperature sensors Tna to Tnc for detecting the refrigerant temperature corresponding to the evaporation temperature during the cooling operation and corresponding to the condensation temperature during the heating operation. Is provided.

  Further, the liquid side branch portions 61a to 61c of the branch unit 6 have temperature detection mechanisms for detecting the temperature of the refrigerant flowing between the use side expansion valves 63a to 63c and the use side heat exchangers 51a to 51c. Liquid tube temperature sensors Tfa to Tfc are provided. Gas pipe temperature sensors Tga to Tgc as temperature detection mechanisms for detecting the temperature of the refrigerant flowing through the gas side branch parts 62a to 62c are provided in the gas side branch parts 62a to 62c of the branch unit 6, respectively.

The temperature sensors Td, Ta, Tb, Tsh, Tra to Trc, Tna to Tnc, Tfa to Tfc, and Tga to Tgc described above are thermistors in the present embodiment.
Next, the control unit 9 will be described. The control unit 9 is mainly composed of a microcomputer and a memory. As shown in FIG. 3, the above-described pressure sensors LP and HP and temperature sensors Td, Ta, Tb, Tsh, Tra to Trc, Tna to Tnc, Tfa to It is connected so that it can receive input signals of Tfc, Tga-Tgc, and various devices and valves 21, 23, 25, 32, 42, 52a-52c, 63a-63c are connected based on these input signals. Connected so that it can be controlled. The control unit 9 controls various devices and valves to perform the cooling operation and the heating operation, and controls the bypass expansion valve 42 provided in the subcooling bypass refrigerant circuit 41. It also functions as a means. In FIG. 3, the indoor fans 52a to 52c and the use side expansion valves 63a to 63c are collectively displayed as one block, but each device or each valve can be controlled individually.

  And the control part 9 as an expansion valve control means for bypass uses the cooler 28 and the bypass refrigerant circuit 41 for supercooling, part of the refrigerant | coolant which flows through the main refrigerant circuit 10 is used for the bypass refrigerant circuit 41 for supercooling. The refrigerant is bypassed so as to return to the suction pipe 33 of the compressor 21, and heat exchange is performed between the bypassed refrigerant and the refrigerant flowing through the main refrigerant circuit 10 in the cooler 28, so that the refrigerant flowing through the main refrigerant circuit 10 is passed through. It has a function of controlling the degree of superheat of the bypass refrigerant circuit to be cooled. More specifically, when the control unit 9 performs bypass refrigerant circuit superheat degree control, the refrigerant that flows through the subcooling bypass refrigerant circuit 41 obtained from the refrigerant temperature detected by the cooler outlet bypass refrigerant temperature sensor Tsh. The bypass expansion valve 42 is opened so that the superheat degree value at the outlet of the cooler 28 (hereinafter referred to as bypass refrigerant circuit side superheat degree tSHa) becomes a predetermined superheat degree value (hereinafter referred to as target superheat degree tSHs). Control the degree. In the present embodiment, the bypass refrigerant circuit side superheat degree tSHA converts the pressure value of the low-pressure gas refrigerant detected by the low-pressure refrigerant pressure sensor LP from the refrigerant temperature value detected by the cooler outlet bypass refrigerant temperature sensor Tsh. This is a value obtained by subtracting the saturation temperature value of the refrigerant obtained. In the case where a cooler inlet bypass refrigerant temperature sensor is provided as a temperature detection mechanism for detecting the temperature of the refrigerant flowing between the bypass expansion valve 42 and the cooler 28 of the bypass cooling refrigerant circuit 41. The bypass refrigerant circuit side superheat degree tSHA is obtained by subtracting the refrigerant temperature value detected by the cooler inlet bypass refrigerant temperature sensor from the refrigerant temperature value detected by the cooler outlet bypass refrigerant temperature sensor Tsh. It may be. In the present embodiment, the target superheat degree tSHs is determined based on the discharge temperature value of the high-pressure gas refrigerant detected by the high-pressure refrigerant temperature sensor Td (hereinafter referred to as the actually measured discharge temperature td). The value is set such that the operation in which the liquid refrigerant is sucked (hereinafter referred to as wet operation) is not performed. That is, the value of the target superheat degree tSHs is varied in the present embodiment so that the actually measured discharge temperature td approaches a predetermined discharge temperature value (hereinafter referred to as a target discharge temperature tds). Specifically, the target superheat degree tSHs is varied so as to decrease when the measured discharge temperature td is higher than the target discharge temperature tds, and to increase when the measured discharge temperature td is lower than the target discharge temperature tds. The Note that the target discharge temperature tds is set to a temperature value that is slightly higher than the discharge temperature value at which the compressor 21 is in a damp operation (hereinafter referred to as the lower limit discharge temperature tdm). Thus, in the bypass refrigerant circuit superheat degree control of the present embodiment, the target superheat degree tSHs is varied so as to be as small as possible within a range where the compressor 21 does not operate in a wet state. The flow rate of the refrigerant flowing through the refrigerant 41 is increased, heat exchange in the cooler 28 is promoted, and the degree of supercooling of the refrigerant flowing through the main refrigerant circuit 10 at the outlet of the cooler 28 (hereinafter referred to as the main refrigerant circuit side subcooling degree tSCa) ) Can be increased.

  Moreover, the control part 9 as a bypass expansion valve control means uses the usage units 5a to 5c (that is, the usage-side heat exchangers 51a to 51a) when the compressor 21 is started under conditions where the outside air temperature is low or under conditions where the outside air temperature is low. 51c) When changing the number of operating units, the refrigerant piping from the use side expansion valves 63a to 63c, the use side heat exchangers 51a to 51c or the use side expansion valves 63a to 63c to the use side heat exchangers 51a to 51c Has a function of performing refrigerant passage sound suppression control for preventing the refrigerant passage noise from being generated. More specifically, when starting the compressor 21 or changing the number of operating units 5a to 5c, the control unit 9 detects the value of the outdoor air temperature detected by the outdoor air temperature sensor Ta (hereinafter, When the outside air temperature ta) is smaller than a predetermined outside air temperature value (hereinafter referred to as refrigerant passing sound generating outside air temperature tDOA), the main refrigerant circuit side subcooling degree tSCa becomes excessively large. The use side expansion valves 63a to 63c and the use side heat exchanger are caused by the fact that the refrigerant after being expanded in the use side expansion valves 63a to 63c becomes a gas-liquid two-phase state or a liquid single-phase state with a low dryness. It is determined that the conditions for generating refrigerant passing sound in the refrigerant piping from 51a to 51c or the usage side expansion valves 63a to 63c to the usage side heat exchangers 51a to 51c (hereinafter referred to as refrigerant passing sound generation conditions) are satisfied. When the refrigerant passage sound generation condition is determined, the bypass expansion valve 42 is closed until a predetermined time (hereinafter referred to as a bypass expansion valve closing time sTs) elapses. After the cooling of the refrigerant sent from the heat exchanger 24 to the use side expansion valves 63a to 63c is suppressed and the main side refrigerant circuit side subcooling degree tSCa is not excessively increased and is expanded in the use side expansion valves 63a to 63c. The refrigerant can be operated in a gas-liquid two-phase state with a high degree of dryness.

(6) Operation | movement of an air conditioning apparatus Next, operation | movement of the air conditioning apparatus 1 of this embodiment is demonstrated. Here, the operation of the cooling operation as the refrigeration cycle operation in which the heat source side heat exchanger 24 functions as a refrigerant condenser and the use side heat exchangers 51a to 51c function as refrigerant evaporators will be described. The description of the heating operation as a refrigeration cycle operation in which the heat source side heat exchanger 24 functions as a refrigerant evaporator and the use side heat exchangers 51a to 51c function as refrigerant condensers is omitted.

<Cooling operation>
First, the operation | movement at the time of air_conditionaing | cooling operation is demonstrated using FIG.1 and FIGS.3-6. Here, FIG. 4 is a Mollier diagram showing the refrigeration cycle of the air-conditioning apparatus 1 during the cooling operation. FIG. 5 is an exchange heat amount-temperature diagram showing a state of heat exchange between the refrigerant flowing on the main refrigerant circuit 10 side in the cooler 28 and the refrigerant flowing on the subcooling bypass refrigerant circuit 41 side. FIG. 6 is a graph showing the relationship between the flow rate of the refrigerant flowing through the subcooling bypass refrigerant circuit 41, the bypass refrigerant circuit side superheat degree tSHA, and the main refrigerant circuit side supercooling degree tSCa.

  In the cooling operation, the main refrigerant circuit 10 and the subcooling bypass circuit 41 are in a state in which the four-way switching valve 23 is indicated by a solid line in FIG. 1, that is, a cooling operation switching state. Moreover, the liquid side closing valve 29, the gas side closing valve 30, and the heat source side expansion valve 25 are opened. Here, assuming that only the usage unit 5a is operated among the usage units 5a to 5c, only the usage side expansion valve 63a of the branch unit 6 corresponding to the usage side heat exchanger 51a of the usage unit 5a is provided. It is assumed that the opening is adjusted. Further, the opening degree of the bypass expansion valve 42 is adjusted by the control of the bypass refrigerant circuit superheat degree by the control unit 9 as a bypass expansion valve control means.

  In the main refrigerant circuit 10 and the subcooling bypass circuit 41, when the outdoor fan 32, the compressor 21, and the indoor fan 52a of the usage unit 5a are operated, the low-pressure gas refrigerant flows from the suction pipe 33 to the compressor 21. And compressed from pressure ps (corresponding to the evaporation pressure of the refrigerant) to pressure pd (corresponding to the condensation pressure of the refrigerant) (see points A and B in FIG. 4). Thereafter, the compressed gas refrigerant is sent to the heat source side heat exchanger 24 via the oil separator 22 and the four-way switching valve 23, and is condensed by exchanging heat with the outdoor air. That is, it is cooled to a condensation temperature) or subcooled to a temperature slightly lower than the saturation temperature (see point C in FIG. 4). The condensed refrigerant flows into the receiver 27 through the heat source side expansion valve 25 and the check valve 26 b of the bridge circuit 26. Then, this liquid refrigerant is temporarily stored in the receiver 27, and then flows into the cooler 28, and is further cooled by exchanging heat with the refrigerant flowing on the subcooling bypass refrigerant circuit 41 side. (Refer to point D and supercooling degree tSCa in FIG. 4). Then, the refrigerant in the supercooled state is sent to the check valve 26c, the liquid side closing valve 29, the liquid refrigerant communication pipe 7d, and the branch unit 6 of the bridge circuit 26. And the refrigerant | coolant sent to the branch unit 6 is pressure-reduced by the utilization side expansion valve 63a (refer the point E of FIG. 4), and is sent to the utilization unit 5a via the liquid refrigerant branch piping 7a. And the refrigerant | coolant sent to the utilization unit 5a is evaporated by exchanging heat with room air by the utilization side heat exchanger 51a (refer the point A of FIG. 4). The evaporated gas refrigerant is again sucked into the compressor 21 via the gas refrigerant branch pipe 8 a, the branch unit 6, the gas refrigerant communication pipe 8, the gas side closing valve 30 and the four-way switching valve 23.

  At this time, a part of the refrigerant liquid stored in the receiver 27 is branched from the main refrigerant circuit 10 while the flow rate is adjusted by the bypass expansion valve 42, and is sucked into the compressor 21 through the subcooling bypass refrigerant circuit 41. Returned to tube 33. Here, a part of the refrigerant passing through the bypass expansion valve 42 is evaporated by being reduced to a pressure close to ps. Then, the refrigerant flowing from the outlet of the bypass expansion valve 42 of the subcooling bypass refrigerant circuit 41 toward the suction pipe 33 of the compressor 21 passes through the cooler 28, and the heat source side heat exchanger of the main refrigerant circuit 10. Heat exchange is performed with the liquid refrigerant sent from 24 to the use side expansion valve 63a of the branch unit 6. Here, the temperature of the refrigerant after passing through the bypass expansion valve 42 (see temperature tVi in FIG. 5) is the temperature of the refrigerant sent from the heat source side heat exchanger 24 of the main refrigerant circuit 10 to the use side expansion valve 63a ( 4 and FIG. 5), the liquid refrigerant sent from the heat source side heat exchanger 24 of the main refrigerant circuit 10 to the use side expansion valve 63a as shown in FIG. 4 and FIG. Is cooled to a temperature tMo and heated to a temperature tVo.

  Here, the bypass expansion valve 42 is based on the bypass refrigerant circuit side superheat degree tSHA obtained from the refrigerant temperature detected by the cooler outlet bypass refrigerant temperature sensor Tsh by the bypass refrigerant circuit superheat degree control by the control unit 9. The opening degree is controlled such that the bypass refrigerant circuit side superheat degree tSHa becomes the target superheat degree tSHs. For this reason, after the refrigerant flowing through the supercooling bypass refrigerant circuit 41 passes through the cooler 28 and is heated to the target superheat degree tSHs (here, the refrigerant detected by the cooler outlet bypass refrigerant temperature sensor Tsh). The temperature is the temperature tVo) and is returned to the suction pipe 33 of the compressor 21. Then, the value of the target superheat degree tSHs is varied based on the measured discharge temperature td of the high-pressure gas refrigerant detected by the high-pressure refrigerant temperature sensor Td so as to reach the target discharge temperature tds at which the compressor 21 is not in a damp operation. Yes. As a result, the refrigerant flowing through the suction pipe 33 of the compressor 21 of the main refrigerant circuit 10 is sufficiently overheated even after the refrigerant that has passed through the cooler 28 is returned from the supercooling bypass refrigerant circuit 41 and merged. If the measured discharge temperature td is higher than the target discharge temperature tds, the target superheat tSHs is decreased to increase the degree of opening of the bypass expansion valve 42 and perform supercooling. The flow rate of the refrigerant flowing through the bypass refrigerant circuit 41 can be increased. Then, as shown in FIG. 6, since the main refrigerant circuit side supercooling degree tSCa increases as the bypass refrigerant circuit side superheat degree tSHA decreases, the heat exchange in the cooler 28 is promoted and the main refrigerant circuit side is increased. The degree of supercooling tSCa is increased (see the degree of superheating tSHs1, the degree of supercooling tSCa1, and the flow rate f1 in FIG. 6). Conversely, when the measured discharge temperature td is lower than the target discharge temperature tds and there is a concern about wet operation, the bypass expansion valve 42 is opened by increasing the value of the bypass refrigerant circuit side superheat degree tSHs. The flow rate of the refrigerant flowing through the subcooling bypass refrigerant circuit 41 can be reduced by decreasing the degree. Then, as shown in FIG. 6, heat exchange in the cooler 28 is suppressed, and the main refrigerant circuit side subcooling degree tSCa becomes small (see the superheating degree tSHs2, the supercooling degree tSCa2, and the flow rate f2 in FIG. 6).

  In this way, during the cooling operation, by performing the bypass refrigerant circuit superheat degree control as described above, the flow rate of the refrigerant flowing through the subcooling bypass refrigerant circuit 41 is increased, and heat exchange in the cooler 28 is promoted. Thus, the main refrigerant circuit side supercooling degree tSCa can be increased. In the above description, the case where only the usage unit 5a is operated among the usage units 5a to 5c has been described as an example. However, when the other usage units 5b and 5c are operated, two of the usage units 5a to 5c are used. The same applies to the case of driving all.

<Starting the compressor>
Next, the operation | movement at the time of starting of the compressor 21 including refrigerant | coolant passage sound suppression control is demonstrated using FIG.1, FIG.3, FIG.7 and FIG. Here, FIG. 7 is a flowchart showing the refrigerant passing sound suppression control. FIG. 8 is a diagram showing the relationship between the main refrigerant circuit side subcooling degree tSCa, the refrigerant dryness at the outlets of the use side expansion valves 63a to 63c, and the refrigerant passing sound generation conditions.

In the main refrigerant circuit 10 and the subcooling bypass circuit 41, before the compressor 21 is started, the four-way switching valve 23 is in the state indicated by the solid line in FIG. Further, the liquid side closing valve 29 and the gas side closing valve 30 are opened, and the heat source side expansion valve 25, the use side expansion valves 63a to 63c and the bypass expansion valve 42 are closed.
Then, when an operation command for the usage units 5a to 5c (here, the operation command is given only to the usage unit 5a), the outdoor fan 32, the compressor 21, and the indoor fan 52a of the usage unit 5a are set. The heat source side expansion valve 25 and the use side expansion valve 63a are opened. At this time, if activation of the compressor 21 is detected in step S1, the process proceeds to step S2.

  Next, in step S2, it is determined whether or not the outside air temperature ta is lower than the refrigerant passing sound generating outside air temperature tDOA. If the outside air temperature ta is equal to or higher than the refrigerant passing sound generating outside air temperature tDOA, the refrigerant passing sound is not generated. And the process proceeds to bypass refrigerant circuit superheat degree control in step S5, and the above-described cooling operation is performed. On the other hand, when the outside air temperature ta is lower than the refrigerant passing sound generating outside air temperature tDOA, it is determined that the refrigerant passing sound is generated, and the process proceeds to step S3.

  Here, the refrigerant passage sound generation condition and the refrigerant passage sound generation outside air temperature tDOA will be described. First, when the compressor 21 is started under a condition where the outside air temperature ta is low, cooling of the refrigerant in the heat source side heat exchanger 24 is promoted, and the degree of subcooling of the refrigerant at the outlet of the heat source side heat exchanger 24 increases. In addition to (refer to point C ′ in FIG. 4), the refrigerant sent from the heat source side heat exchanger 24 to the use side expansion valve 63a is further cooled in the cooler 28, so that the main refrigerant circuit side subcooling degree tSCa is Increased (see point D ′ in FIG. 4). Then, the degree of dryness also under the condition of the refrigerant pressure ps after expansion in the use side expansion valve 63a (that is, near the evaporation pressure of the use side heat exchanger 51a functioning as an evaporator) (see point E ′ in FIG. 4). The gas-liquid two-phase state or the liquid single-phase state may be small. And when starting the compressor 21, if such a refrigerant | coolant with large main refrigerant circuit side supercooling degree tSCa flows in into the utilization side expansion valve 63a and the utilization side heat exchanger 51a, although it is temporary, utilization side A large refrigerant passing sound is generated in the refrigerant pipe from the expansion valve 63a, the use side heat exchanger 51a or the use side expansion valve 63a to the use side heat exchanger 51a. The region where the main refrigerant circuit side supercooling degree tSCa is large and the dryness of the refrigerant at the outlet of the use side expansion valve 63a is small (see the hatched portion in FIG. 8) is a refrigerant passing sound in which a large refrigerant passing sound is generated. It is an occurrence condition. When the value of the main refrigerant circuit side subcooling degree tSCa that can be the refrigerant passage noise generation condition is the refrigerant passage noise generation subcooling degree tSC1, the outside air temperature ta that can be the refrigerant passage noise generation subcooling degree tSC1. Is the refrigerant passing sound generation outside air temperature tDOA. That is, the refrigerant passing sound generation outside air temperature tDOA is a value used in place of the refrigerant passing sound generation subcooling degree tSC1 when determining the refrigerant passing sound generation condition when the compressor 21 is started. Note that the refrigerant passing sound generation outside air temperature tDOA is set to about 25 ° C., for example.

  Next, in step S3, control is performed to close the bypass expansion valve 42 of the subcooling bypass refrigerant circuit 41, and the bypass refrigerant circuit superheat control is not performed while maintaining the closed state before the compressor 21 is started. To do. As a result, the refrigerant heading from the heat source side heat exchanger 24 toward the use side expansion valve 63a is not cooled in the cooler 28 (see point C ′ in FIG. 4), so the main refrigerant circuit side subcooling degree tSCa is excessively large. Never become. For this reason, the refrigerant at the outlet of the use side expansion valve 63a does not enter a gas-liquid two-phase state or a liquid single-phase state with a low dryness (see point E ″ in FIG. 4). Generation | occurrence | production of the refrigerant | coolant passage sound in the refrigerant | coolant piping from the heat exchanger 51a or the utilization side expansion valve 63a to the utilization side heat exchanger 51a is suppressed.

  This step S3 is performed until the bypass expansion valve closing time sTs elapses in step S4. When the bypass expansion valve closing time sTs has elapsed in step S4, the process proceeds to the bypass refrigerant circuit superheat degree control in step S5, and the above-described cooling operation is performed. Here, the bypass expansion valve closing time sTs indicates that when the compressor 21 is started, the refrigerant passing sound is generated when the process proceeds to the bypass refrigerant circuit superheat degree control in step S5 without performing the process in step S3. It is set based on the duration. The bypass expansion valve closing time sTs is set to about 5 minutes, for example.

  Thus, in the air conditioning apparatus 1 of this embodiment, when starting the compressor 21, the refrigerant | coolant after being expanded in the utilization side expansion valves 63a-63c is a gas-liquid two-phase state with small dryness, or a liquid unit. Refrigerant passage in refrigerant piping from use side expansion valves 63a to 63c, use side heat exchangers 51a to 51c or use side expansion valves 63a to 63c to use side heat exchangers 51a to 51c due to the phase state Generation of sound can be suppressed. In the above description, the case where only the usage unit 5a is operated among the usage units 5a to 5c has been described as an example. However, when the other usage units 5b and 5c are operated, two of the usage units 5a to 5c are used. The same applies to the case of all driving.

<Changing the number of operating units used>
Next, the operation at the time of changing the number of operating units 5a to 5c including the refrigerant passing sound suppression control will be described using FIG. 1, FIG. 3, FIG. 7, and FIG.
Here, it is assumed that only the usage unit 5a among the usage units 5a to 5c is in the above-described cooling operation, and the case where the operation command for the usage unit 5b is issued from this state will be described.

  First, when an operation command is given to the usage unit 5b from the state where only the usage unit 5a is in the cooling operation, the indoor fan 52b of the usage unit 5b is activated and the usage-side expansion valve 63b is opened. At this time, if an operation command for the usage unit 5a (that is, a change in the number of operating units 5a to 5c) is detected in step S1, the process proceeds to step S2.

  Next, in step S2, it is determined whether or not the outside air temperature ta is lower than the refrigerant passing sound generating outside air temperature tDOA. If the outside air temperature ta is equal to or higher than the refrigerant passing sound generating outside air temperature tDOA, the refrigerant passing sound is not generated. And the process proceeds to bypass refrigerant circuit superheat degree control in step S5, and the above-described cooling operation is performed. On the other hand, when the outside air temperature ta is lower than the refrigerant passing sound generating outside air temperature tDOA, it is determined that the refrigerant passing sound is generated, and the process proceeds to step S3.

  Here, the refrigerant passage sound generation condition and the refrigerant passage sound generation outside air temperature tDOA will be described. First, when changing the number of operating units by operating the usage units 5b in addition to the usage units 5a under a condition where the outside air temperature ta is low, the degree of subcooling on the main refrigerant circuit side is the same as when the compressor 21 is started. tSCa increases (see point D ′ in FIG. 4). Then, under the condition of the refrigerant pressure ps after expansion in the use side expansion valves 63a and 63b (that is, near the evaporation pressure of the use side heat exchangers 51a and 51b functioning as an evaporator) (see point E ′ in FIG. 4). However, there may be a gas-liquid two-phase state or a liquid single-phase state with a low dryness. When the number of units to be operated is changed by operating the use unit 5b, such a refrigerant having a large main refrigerant circuit side supercooling degree tSCa is transferred to the use side expansion valves 63a and 63b and the use side heat exchangers 51a and 51b. When flowing, in the refrigerant piping from the use side expansion valves 63a, 63b and the use side heat exchangers 51a, 51b or the use side expansion valves 63a, 63b to the use side heat exchangers 51a, 51b, although temporarily. A large refrigerant passing sound is generated. The refrigerant in which the main refrigerant circuit side supercooling degree tSCa is large and the refrigerant dryness at the outlets of the use side expansion valves 63a and 63b is small (see the hatched portion in FIG. 8) generates a large refrigerant passing sound. This is a passing sound generation condition. When the value of the main refrigerant circuit side subcooling degree tSCa that can be the refrigerant passage noise generation condition is the refrigerant passage noise generation subcooling degree tSC1, the outside air temperature ta that can be the refrigerant passage noise generation subcooling degree tSC1. Is the refrigerant passing sound generation outside air temperature tDOA. That is, the refrigerant passing sound generation outside air temperature tDOA is a value used in place of the refrigerant passing sound generation subcooling degree tSC1 when determining the refrigerant passing sound generation condition when the compressor 21 is started. As described above, even when the number of operating units 5a to 5c is changed, the refrigerant passage sound generation condition exists and the corresponding refrigerant passage sound generation outside air temperature tDOA is present as in the case of starting the compressor 21. Exists. Note that the refrigerant passing sound generation outside air temperature tDOA when the number of operating units 5a to 5c is changed is set to about 25 ° C., for example.

  Next, in step S3, the bypass expansion valve 42 of the subcooling bypass refrigerant circuit 41 is controlled to be closed, and the bypass refrigerant circuit superheat degree control is not performed. As a result, the refrigerant from the heat source side heat exchanger 24 toward the use side expansion valves 63a and 63b is not cooled in the cooler 28 (see point C ′ in FIG. 4), so that the main refrigerant circuit side subcooling degree tSCa is excessive. It will never grow. Therefore, the refrigerant at the outlets of the use side expansion valves 63a and 63b does not enter a gas-liquid two-phase state or a liquid single-phase state with a low dryness (see point E ″ in FIG. 4). Generation | occurrence | production of the refrigerant | coolant passage sound in the refrigerant | coolant piping from 63b, utilization side heat exchanger 51a, 51b or utilization side expansion valve 63a, 63b to utilization side heat exchanger 51a, 51b is suppressed.

  This step S3 is performed until the bypass expansion valve closing time sTs elapses in step S4. When the bypass expansion valve closing time sTs has elapsed in step S4, the process proceeds to the bypass refrigerant circuit superheat degree control in step S5, and the above-described cooling operation is performed. Here, the bypass expansion valve closing time sTs is obtained when the operation number is changed by operating the use unit 5a and the process proceeds to the bypass refrigerant circuit superheat degree control in step S5 without performing the process in step S3. Further, it is set based on the time during which the generation of the refrigerant passing sound continues. The bypass expansion valve closing time sTs is set to about 2 minutes, for example.

  As described above, in the air conditioner 1 of the present embodiment, when the number of operating units 5a to 5c is changed, the refrigerant after being expanded in the usage side expansion valves 63a to 63c is a gas-liquid two having a low dryness. From the use-side expansion valves 63a to 63c, the use-side heat exchangers 51a to 51c or the use-side expansion valves 63a to 63c to the use-side heat exchangers 51a to 51c due to the phase state or the liquid single-phase state Generation | occurrence | production of the refrigerant | coolant passage sound in refrigerant | coolant piping can be suppressed. In the above description, the case where the number of units to be operated is changed by operating the usage units 5b from the state where only the usage units 5a among the usage units 5a to 5c are operated has been described as an example. When changing the number of operating units by changing the number of operating units by operating the usage unit 5a or the usage unit 5c from the state of operating only the usage unit 5b, the state of operating only the usage unit 5c When changing the number of operating units by operating the usage unit 5a or the usage unit 5b, or from the state in which two of the usage units 5a to 5c are operating, the remaining one of the usage units 5a to 5c The same applies to the case where the number of operating units is changed by driving.

(7) Features of the air conditioner The air conditioner 1 of the present embodiment has the following features.
(A)
In the air conditioner 1 of the present embodiment, the refrigerant whose outside air temperature ta is a predetermined outside air temperature when the compressor 21 is started or when the number of operating units 5a to 5c (that is, the use side heat exchangers 51a to 51c) is changed. When the condition is lower than the passing sound generation outside air temperature tDOA, the refrigerant after being expanded in the use side expansion valves 63a to 63c as the expansion mechanism by excessively increasing the main refrigerant circuit side supercooling degree tSCa. Becomes a gas-liquid two-phase state or a liquid single-phase state with a low dryness, and due to this, from the use side expansion valves 63a to 63c, the use side heat exchangers 51a to 51c or the use side expansion valves 63a to 63c, It can be determined that it is a condition (that is, a refrigerant passing sound generation condition) in which a refrigerant passing sound is generated in the refrigerant pipe up to the heat exchangers 51a to 51c. And in this air conditioning apparatus 1, when it determines with it being refrigerant | coolant passage sound generation | occurrence | production conditions, by closing the bypass expansion valve 42 until the bypass expansion valve closing time sTs as a predetermined time elapses, the cooler In the use side expansion valves 63a to 63c, the cooling of the refrigerant sent from the heat source side heat exchanger 24 to the use side expansion valves 63a to 63c is suppressed, and the main refrigerant circuit side subcooling degree tSCa is not excessively increased. It is possible to perform an operation such that the expanded refrigerant becomes a gas-liquid two-phase state with a high degree of dryness.

  Thereby, when starting the compressor 21 or changing the number of operating units 5a to 5c, the refrigerant after being expanded in the usage side expansion valves 63a to 63c is in a gas-liquid two-phase state where the dryness is small. In the refrigerant piping from the use side expansion valves 63a to 63c and the use side heat exchangers 51a to 51c or the use side expansion valves 63a to 63c to the use side heat exchangers 51a to 51c due to the liquid single phase state. Generation of refrigerant passing sound can be suppressed.

(B)
Moreover, in the air conditioning apparatus 1 of this embodiment, the target superheat degree tSHs at the time of performing bypass refrigerant circuit superheat degree control is set to a value at which the compressor 21 does not perform wet operation based on the measured discharge temperature td of the compressor 21. Thus, since the operation is performed to increase the main refrigerant circuit side subcooling degree tSCa as much as possible, the refrigerant pressure after expansion in the use side expansion valves 63a to 63c (that is, the use side heat exchange functioning as an evaporator). Under the condition of the evaporation pressure of the vessels 51a to 51c), the gas-liquid two-phase state or the liquid single-phase state with a small dryness is likely to occur, and the refrigerant passing sound generation condition is likely to occur.

  However, even when such bypass refrigerant circuit superheat degree control is performed, the refrigerant after being expanded in the use side expansion valves 63a to 63c has a low dryness by performing the above-described refrigerant passage sound suppression control. From the use side expansion valves 63a to 63c, the use side heat exchangers 51a to 51c or the use side expansion valves 63a to 63c resulting from the gas-liquid two-phase state or the liquid single phase state, to the use side heat exchangers 51a to 51c. Generation | occurrence | production of the refrigerant | coolant passage sound in the refrigerant | coolant piping until it can reach can be suppressed.

(8) Modification 1
In the above-described embodiment, the refrigerant passing sound generation condition is determined using the outside air temperature ta in the refrigerant passing sound suppression control. However, the refrigerant is not using the outside air temperature ta but using the main refrigerant circuit side subcooling degree tSCa. The determination of the passage sound generation condition may be performed.
Next, although this modification is demonstrated concretely, below, only the difference with the above-mentioned embodiment shall be demonstrated.

  In this modification, as shown in FIGS. 9 and 10, in addition to the configuration of the above-described embodiment, cooling as a temperature detection mechanism for detecting the temperature of the refrigerant at the outlet of the cooler 28 of the main refrigerant circuit 10. An outlet main refrigerant circuit refrigerant temperature sensor Tsc is provided. The refrigerant temperature value detected by the temperature sensor Tsc is obtained by converting the pressure value of the high-pressure gas refrigerant detected by the high-pressure refrigerant pressure sensor HP. By subtracting from the saturation temperature value of the refrigerant, the degree of supercooling tSCa on the main refrigerant circuit side can be obtained. The main refrigerant circuit side subcooling degree tSCa is obtained by subtracting the refrigerant temperature value detected by the cooler outlet main refrigerant circuit refrigerant temperature sensor Tsc from the refrigerant temperature value detected by the heat source side heat exchange temperature sensor Tb. You may make it obtain. In this modification, as shown in FIG. 11, the main refrigerant circuit side subcooling degree tSCa and the refrigerant obtained from the refrigerant temperature detected by the cooler outlet main refrigerant circuit refrigerant temperature sensor Tsc in step S2. It is determined whether or not the passage sound generation supercooling degree tSC1 (explained in the above-described embodiment) is larger. If the main refrigerant circuit side subcooling degree tSCa is equal to or lower than the refrigerant passage sound generation supercooling degree tSC1, the refrigerant passes. It is determined that the sound generation condition is not satisfied, and when the main refrigerant circuit side subcooling degree tSCa is larger than the refrigerant passing sound generation supercooling degree tSC1, only the refrigerant passing sound generation condition is determined. This is different from the refrigerant passing sound suppression control (see FIG. 7) in the above-described embodiment. That is, in the refrigerant passage noise suppression control in the above-described embodiment, the refrigerant passage noise generation condition in step S2 is determined using the refrigerant passage noise generation outside air temperature tDOA corresponding to the refrigerant passage noise generation supercooling degree tSC1. However, in the refrigerant passage noise suppression control in this modification, the refrigerant passage noise generation supercooling degree tSC1 is directly used as the first predetermined supercooling degree value for determining the refrigerant passage noise generation condition. is there.

  Thus, in this modification, the main refrigerant circuit side subcooling degree tSCa is the first when the compressor 21 is started or when the number of operating units 5a to 5c (that is, the usage side heat exchangers 51a to 51c) is changed. When the refrigerant passing sound generation supercooling degree tSC1 as the predetermined supercooling degree value becomes larger, the main refrigerant circuit side subcooling degree tSCa becomes excessively large, so that the use side expansion valve as the expansion mechanism The refrigerant after being expanded in 63a to 63c becomes a gas-liquid two-phase state or a liquid single-phase state with a low dryness, and as a result, the use side expansion valves 63a to 63c and the use side heat exchangers 51a to 51c or It can be determined that the refrigerant passage noise is generated in the refrigerant pipe from the usage side expansion valves 63a to 63c to the usage side heat exchangers 51a to 51c (that is, the refrigerant passage noise generation condition). . And in this air conditioning apparatus 1, when it determines with it being refrigerant | coolant passage sound generation | occurrence | production conditions, by closing the bypass expansion valve 42 until the bypass expansion valve closing time sTs as a predetermined time elapses, the cooler In the use side expansion valves 63a to 63c, the cooling of the refrigerant sent from the heat source side heat exchanger 24 to the use side expansion valves 63a to 63c is suppressed, and the main refrigerant circuit side subcooling degree tSCa is not excessively increased. It is possible to perform an operation such that the expanded refrigerant becomes a gas-liquid two-phase state with a high degree of dryness.

  Thereby, when starting the compressor 21 or changing the number of operating units 5a to 5c, the refrigerant after being expanded in the usage side expansion valves 63a to 63c is in a gas-liquid two-phase state where the dryness is small. In the refrigerant piping from the use side expansion valves 63a to 63c and the use side heat exchangers 51a to 51c or the use side expansion valves 63a to 63c to the use side heat exchangers 51a to 51c due to the liquid single phase state. Generation of refrigerant passing sound can be suppressed.

  Further, as shown in FIG. 12, the value of the refrigerant passing sound generation supercooling degree tSC1 tends to decrease when the outside air temperature ta is low and increases when the outside air temperature ta is high. In the refrigerant passing sound suppression control of the present modification, the refrigerant passing sound generation condition can be more appropriately determined by setting the value of the refrigerant passing sound generation supercooling degree tSC1 as a function of the outside air temperature ta.

(9) Modification 2
In the modified example 1, in step S4 of the refrigerant passing sound suppression control, the control for closing the bypass expansion valve 42 of the subcooling bypass refrigerant circuit 41 is performed until the bypass expansion valve closing time sTs elapses. The control for closing the bypass expansion valve 42 using the main refrigerant circuit side supercooling degree tSCa instead of the time may be released to shift to the bypass refrigerant circuit superheat degree control.

Next, although this modification is demonstrated concretely, below, only the difference with the above-mentioned modification 1 shall be demonstrated.
In this modification, as shown in FIG. 13, the control for closing the bypass expansion valve 42 of the subcooling bypass refrigerant circuit 41 in step S3 is performed. In step S4, the main refrigerant circuit side subcooling degree tSCa is expanded for bypassing. This is performed until the valve closing release supercooling degree tSC2. Here, the value of the bypass expansion valve closing release supercooling degree tSC2 is set to a value equal to or lower than the refrigerant passing sound generation supercooling degree tSC1, but it may adversely affect the determination of the refrigerant passing sound generation condition in step S2. It is desirable to set a value smaller than the refrigerant passing sound generation supercooling degree tSC1.

  Thus, in this modification, the main refrigerant circuit side subcooling degree tSCa is the first when the compressor 21 is started or when the number of operating units 5a to 5c (that is, the usage side heat exchangers 51a to 51c) is changed. When the refrigerant passing sound generation supercooling degree tSC1 as the predetermined supercooling degree value becomes larger, the main refrigerant circuit side subcooling degree tSCa becomes excessively large, so that the use side expansion valve as the expansion mechanism The refrigerant after being expanded in 63a to 63c becomes a gas-liquid two-phase state or a liquid single-phase state with a low dryness, and as a result, the use side expansion valves 63a to 63c and the use side heat exchangers 51a to 51c or It can be determined that the refrigerant passage noise is generated in the refrigerant pipe from the usage side expansion valves 63a to 63c to the usage side heat exchangers 51a to 51c (that is, the refrigerant passage noise generation condition). . In this air conditioner 1, when it is determined that the refrigerant passage sound generation condition is satisfied, the bypass refrigerant expansion valve closing release is performed with the main refrigerant circuit side subcooling degree tSCa as the second predetermined subcooling degree value. By closing the bypass expansion valve 42 until the degree of supercooling tSC2 or less, cooling of the refrigerant sent from the heat source side heat exchanger 24 to the use side expansion valves 63a to 63c in the cooler 28 is suppressed, and the main refrigerant circuit side It is possible to perform an operation such that the refrigerant after being expanded in the use side expansion valves 63a to 63c is in a gas-liquid two-phase state with a high dryness without excessively increasing the degree of supercooling tSCa.

  Thereby, when starting the compressor 21 or changing the number of operating units 5a to 5c, the refrigerant after being expanded in the usage side expansion valves 63a to 63c is in a gas-liquid two-phase state where the dryness is small. In the refrigerant piping from the use side expansion valves 63a to 63c and the use side heat exchangers 51a to 51c or the use side expansion valves 63a to 63c to the use side heat exchangers 51a to 51c due to the liquid single phase state. Generation of refrigerant passing sound can be suppressed.

Further, in the present modified example as well, as in the first modified example, the refrigerant passing sound generation condition is determined more appropriately by setting the value of the refrigerant passing sound generating supercooling degree tSC1 as a function of the outside air temperature ta. Can do.
Further, the value of the bypass expansion valve closing release supercooling degree tSC2 is small when the outside air temperature ta is low, and the value when the outside air temperature ta is high, similar to the value of the refrigerant passing sound generation supercooling degree tSC1. Therefore, by setting the value of the bypass expansion valve closure release subcooling degree tSC2 as a function of the outside air temperature ta in the refrigerant passing sound suppression control of this modification, the bypass The control for closing the expansion valve 42 can be released.

(10) Modification 3
In step S4 of the refrigerant passing sound suppression control of the first modification, the control for closing the bypass expansion valve 42 of the subcooling bypass refrigerant circuit 41 is performed until the bypass expansion valve closing time sTs elapses. In step S4 of the refrigerant passing sound suppression control of the example 2, the control for closing the bypass expansion valve 42 of the subcooling bypass refrigerant circuit 41 is controlled by the main refrigerant circuit side supercooling degree tSCa being the bypass expansion valve closing release supercooling degree tSC2. Although it is made to carry out until it becomes, you may use combining both.

Next, although this modification is demonstrated concretely, below, only the difference with the above-mentioned modification 1 and modification 2 shall be demonstrated.
In this modified example, as shown in FIG. 14, the control for closing the bypass expansion valve 42 of the subcooling bypass refrigerant circuit 41 in step S3 is performed. In step S4, the bypass expansion valve closing time sTs elapses. Alternatively, the process is performed until either of the conditions in which the main refrigerant circuit side supercooling degree tSCa becomes the bypass expansion valve closing release supercooling degree tSC2 is satisfied. As a result, when only one of the passage of the bypass expansion valve closing time sTs or the arrival of the bypass expansion valve closing release supercooling degree tSC2 is set as the release condition of the control for closing the bypass expansion valve 42. In comparison, the control for closing the bypass expansion valve 42 can be released at a more appropriate timing.

Also in the present modification, as in Modifications 1 and 2, the refrigerant passing sound generation supercooling degree tSC1 and the bypass expansion valve closing release supercooling degree tSC2 are set as functions of the outside air temperature ta. Also good.
(11) Other Embodiments Although the embodiments of the present invention have been described with reference to the drawings, the specific configuration is not limited to these embodiments and can be changed without departing from the gist of the invention. It is.

(A)
In this embodiment and its modification, the example which applied this invention to the air conditioning apparatus which can perform air_conditionaing | cooling operation and heating operation was demonstrated, but this air conditioning apparatus which can perform only air_conditionaing | cooling operation is this. The invention may be applied.
(B)
In the present embodiment and its modifications, the example in which the present invention is applied to a multi-type air conditioner in which a plurality of usage units are connected to a heat source unit via a branch unit having a usage side expansion valve has been described. The present invention may also be applied to a multi-type air conditioner in which a plurality of utilization units having a side expansion valve are directly connected to a heat source unit (that is, not via a branch unit).

(C)
In this embodiment and its modification, the example which applied this invention to the multi-type air conditioning apparatus was demonstrated, However, This invention is applied to the pair type air conditioning apparatus which connected one utilization unit to the heat-source unit. May be. However, in this case, since the number of operating units is not changed, only the refrigerant passing sound suppression control at the time of starting the compressor is applied.

  By using the present invention, a part of the refrigerant flowing through the main refrigerant circuit is bypassed so as to return to the suction side of the compressor, and the refrigerant flowing through the main refrigerant circuit is brought into a supercooled state using the bypassed refrigerant. In the air conditioner configured to be able to perform the above, it is possible to suppress the generation of refrigerant passing sound in the expansion valve, the use side heat exchanger, or the refrigerant pipe from the expansion valve to the use side heat exchanger.

It is a schematic refrigerant circuit diagram of the air conditioning apparatus as one embodiment of the present invention. It is sectional drawing which shows schematic structure of a cooler. It is a control block diagram of an air conditioning apparatus. It is a Mollier diagram which shows the refrigerating cycle of the air conditioning apparatus at the time of air_conditionaing | cooling operation. It is an exchange heat amount-temperature diagram which shows the state of heat exchange with the refrigerant | coolant which flows through the main refrigerant circuit side in the cooler, and the refrigerant which flows through the bypass refrigerant circuit side for supercooling. It is a diagram which shows the relationship between the flow volume of the refrigerant | coolant which flows through the bypass refrigerant circuit for supercooling, the bypass refrigerant circuit side superheat degree tSHA, and the main refrigerant circuit side supercooling degree tSCa. It is a flowchart which shows refrigerant | coolant passage sound suppression control. It is a figure which shows the relationship between the main refrigerant circuit side supercooling degree tSCa, the dryness of the refrigerant | coolant in a use side expansion valve exit, and refrigerant | coolant passage sound generation conditions. It is a schematic refrigerant circuit diagram of the air conditioning apparatus concerning the modifications 1-3. It is a control block diagram of the air conditioning apparatus concerning the modifications 1-3. 10 is a flowchart showing refrigerant passing sound suppression control according to Modification 1; It is a diagram which shows the relationship between outside temperature ta and refrigerant | coolant passage sound generation | occurrence | production supercooling degree tSC1. 10 is a flowchart showing refrigerant passing sound suppression control according to Modification 2. 10 is a flowchart showing refrigerant passage noise suppression control according to Modification 3.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Air conditioning apparatus 21 Compressor 24 Heat source side heat exchanger 51a-51c Use side heat exchanger 63a-63c Expansion mechanism 10 Main refrigerant circuit 42 Bypass expansion valve 41 Subcooling bypass refrigerant circuit (bypass refrigerant circuit)
28 Cooler tSHa Bypass refrigerant circuit side superheat degree tSHs Target superheat degree (predetermined superheat degree value)
9 Control unit ta outside air temperature tDOA Refrigerant passing sound generation outside air temperature (predetermined outside air temperature value)
sTs Bypass expansion valve closing time (predetermined time)
tSCa Main refrigerant circuit side supercooling degree tSC1 Refrigerant passing sound generation supercooling degree (first predetermined supercooling degree value)
tSC2 Bypass expansion valve closing release supercooling degree (second predetermined supercooling degree value)
td Actual discharge temperature (discharge temperature)

Claims (8)

A compressor (21), a heat source side heat exchanger (24), a use side heat exchanger (51a to 51c), and an expansion mechanism (63a to 63c), the compressor, the heat source side heat exchanger, Refrigeration that causes the heat source side heat exchanger to function as a refrigerant condenser by circulating the refrigerant in the order of the expansion mechanism and the usage side heat exchanger, and causes the usage side heat exchanger to function as an evaporator of the refrigerant. A main refrigerant circuit (10) configured to be capable of cycle operation;
The main refrigerant circuit is connected to the main refrigerant circuit so that a part of the refrigerant sent from the heat source side heat exchanger to the expansion mechanism is branched from the main refrigerant circuit and returned to the suction side of the compressor. A bypass refrigerant circuit (41) having a bypass expansion valve (42) for adjusting the flow rate of the refrigerant branched from
A cooler (28) for cooling the refrigerant sent from the heat source side heat exchanger to the expansion mechanism by the refrigerant returned from the outlet of the bypass expansion valve to the suction side of the compressor;
Bypass refrigerant for controlling the bypass expansion valve so that the bypass refrigerant circuit side superheat degree (tSHa), which is the degree of superheat of the refrigerant flowing in the bypass refrigerant circuit, at the cooler outlet becomes a predetermined superheat degree value (tSHs). A control unit (9) for performing circuit superheat control,
The controller closes the bypass expansion valve until a predetermined time (sTs) elapses when the outside air temperature (ta) is smaller than a predetermined outside air temperature value (tDOA) at the time of starting the compressor. Control,
Air conditioner (1). A compressor (21), a heat source side heat exchanger (24), a use side heat exchanger (51a to 51c), and an expansion mechanism (63a to 63c), the compressor, the heat source side heat exchanger, Refrigeration that causes the heat source side heat exchanger to function as a refrigerant condenser by circulating the refrigerant in the order of the expansion mechanism and the usage side heat exchanger, and causes the usage side heat exchanger to function as an evaporator of the refrigerant. A main refrigerant circuit (10) configured to be capable of cycle operation;
The main refrigerant circuit is connected to the main refrigerant circuit so that a part of the refrigerant sent from the heat source side heat exchanger to the expansion mechanism is branched from the main refrigerant circuit and returned to the suction side of the compressor. A bypass refrigerant circuit (41) having a bypass expansion valve (42) for adjusting the flow rate of the refrigerant branched from
A cooler (28) for cooling the refrigerant sent from the heat source side heat exchanger to the expansion mechanism by the refrigerant returned from the outlet of the bypass expansion valve to the suction side of the compressor;
Bypass refrigerant for controlling the bypass expansion valve so that the bypass refrigerant circuit side superheat degree (tSHa), which is the degree of superheat of the refrigerant flowing in the bypass refrigerant circuit, at the cooler outlet becomes a predetermined superheat degree value (tSHs). A control unit (9) for performing circuit superheat control,
When the compressor is started, the control unit has a first subcooling degree that is a main refrigerant circuit side subcooling degree (tSCa) that is a subcooling degree of the refrigerant flowing through the main refrigerant circuit at the cooler outlet. Control to close the bypass expansion valve until a predetermined time (sTs) elapses.
Air conditioner (1). A compressor (21), a heat source side heat exchanger (24), a use side heat exchanger (51a to 51c), and an expansion mechanism (63a to 63c), the compressor, the heat source side heat exchanger, Refrigeration that causes the heat source side heat exchanger to function as a refrigerant condenser by circulating the refrigerant in the order of the expansion mechanism and the usage side heat exchanger, and causes the usage side heat exchanger to function as an evaporator of the refrigerant. A main refrigerant circuit (10) configured to be capable of cycle operation;
The main refrigerant circuit is connected to the main refrigerant circuit so that a part of the refrigerant sent from the heat source side heat exchanger to the expansion mechanism is branched from the main refrigerant circuit and returned to the suction side of the compressor. A bypass refrigerant circuit (41) having a bypass expansion valve (42) for adjusting the flow rate of the refrigerant branched from
A cooler (28) for cooling the refrigerant sent from the heat source side heat exchanger to the expansion mechanism by the refrigerant returned from the outlet of the bypass expansion valve to the suction side of the compressor;
Bypass refrigerant for controlling the bypass expansion valve so that the bypass refrigerant circuit side superheat degree (tSHa), which is the degree of superheat of the refrigerant flowing in the bypass refrigerant circuit, at the cooler outlet becomes a predetermined superheat degree value (tSHs). A control unit (9) for performing circuit superheat control,
The control unit has a first predetermined supercooling degree that is a main refrigerant circuit side subcooling degree (tSCa) that is a supercooling degree at the outlet of the cooler of the refrigerant flowing through the main refrigerant circuit at the time of starting the compressor. When the main refrigerant circuit side subcooling degree is equal to or lower than a second predetermined supercooling degree value (tSC2), the bypass expansion valve is controlled to be less than (tSC1).
Air conditioner. A compressor (21), a heat source side heat exchanger (24), a plurality of usage side heat exchangers (51a to 51c), and a plurality of expansion mechanisms (63a to 63c) respectively corresponding to the plurality of usage side heat exchangers; And circulating the refrigerant in the order of the compressor, the heat source side heat exchanger, the expansion mechanism, and the use side heat exchanger, thereby causing the heat source side heat exchanger to function as a refrigerant condenser, and A main refrigerant circuit (10) configured to enable a refrigeration cycle operation in which the use side heat exchanger functions as a refrigerant evaporator;
The main refrigerant circuit is connected to the main refrigerant circuit so that a part of the refrigerant sent from the heat source side heat exchanger to the expansion mechanism is branched from the main refrigerant circuit and returned to the suction side of the compressor. A bypass refrigerant circuit (41) having a bypass expansion valve (42) for adjusting the flow rate of the refrigerant branched from
A cooler (28) for cooling the refrigerant sent from the heat source side heat exchanger to the expansion mechanism by the refrigerant returned from the outlet of the bypass expansion valve to the suction side of the compressor;
Bypass refrigerant for controlling the bypass expansion valve so that the bypass refrigerant circuit side superheat degree (tSHa), which is the degree of superheat of the refrigerant flowing in the bypass refrigerant circuit, at the cooler outlet becomes a predetermined superheat degree value (tSHs). A control unit (9) for performing circuit superheat control,
When the outside air temperature (ta) is smaller than a predetermined outside air temperature value (tDOA) when the number of operating side heat exchangers is changed, the control unit performs the bypass operation until a predetermined time (sTs) elapses. Control to close the expansion valve,
Air conditioner (1). A compressor (21), a heat source side heat exchanger (24), a plurality of usage side heat exchangers (51a to 51c), and a plurality of expansion mechanisms (63a to 63c) respectively corresponding to the plurality of usage side heat exchangers; And circulating the refrigerant in the order of the compressor, the heat source side heat exchanger, the expansion mechanism, and the use side heat exchanger, thereby causing the heat source side heat exchanger to function as a refrigerant condenser, and A main refrigerant circuit (10) configured to enable a refrigeration cycle operation in which the use side heat exchanger functions as a refrigerant evaporator;
The main refrigerant circuit is connected to the main refrigerant circuit so that a part of the refrigerant sent from the heat source side heat exchanger to the expansion mechanism is branched from the main refrigerant circuit and returned to the suction side of the compressor. A bypass refrigerant circuit (41) having a bypass expansion valve (42) for adjusting the flow rate of the refrigerant branched from
A cooler (28) for cooling the refrigerant sent from the heat source side heat exchanger to the expansion mechanism by the refrigerant returned from the outlet of the bypass expansion valve to the suction side of the compressor;
Bypass refrigerant for controlling the bypass expansion valve so that the bypass refrigerant circuit side superheat degree (tSHa), which is the degree of superheat of the refrigerant flowing in the bypass refrigerant circuit, at the cooler outlet becomes a predetermined superheat degree value (tSHs). A control unit (9) for performing circuit superheat control,
The control unit has a main refrigerant circuit side subcooling degree (tSCa) that is a degree of subcooling at the cooler outlet of the refrigerant flowing through the main refrigerant circuit when the number of operating side heat exchangers is changed. When the predetermined supercooling degree value (tSC1) is greater, control is performed to close the bypass expansion valve until a predetermined time (sTs) elapses.
Air conditioner (1). A compressor (21), a heat source side heat exchanger (24), a plurality of usage side heat exchangers (51a to 51c), and a plurality of expansion mechanisms (63a to 63c) respectively corresponding to the plurality of usage side heat exchangers; And circulating the refrigerant in the order of the compressor, the heat source side heat exchanger, the expansion mechanism, and the use side heat exchanger, thereby causing the heat source side heat exchanger to function as a refrigerant condenser, and A main refrigerant circuit (10) configured to enable a refrigeration cycle operation in which the use side heat exchanger functions as a refrigerant evaporator;
The main refrigerant circuit is connected to the main refrigerant circuit so that a part of the refrigerant sent from the heat source side heat exchanger to the expansion mechanism is branched from the main refrigerant circuit and returned to the suction side of the compressor. A bypass refrigerant circuit (41) having a bypass expansion valve (42) for adjusting the flow rate of the refrigerant branched from
A cooler (28) for cooling the refrigerant sent from the heat source side heat exchanger to the expansion mechanism by the refrigerant returned from the outlet of the bypass expansion valve to the suction side of the compressor;
Bypass refrigerant for controlling the bypass expansion valve so that the bypass refrigerant circuit side superheat degree (tSHa), which is the degree of superheat of the refrigerant flowing in the bypass refrigerant circuit, at the cooler outlet becomes a predetermined superheat degree value (tSHs). A control unit (9) for performing circuit superheat control,
The control unit has a main refrigerant circuit side subcooling degree (tSCa) that is a degree of subcooling at the cooler outlet of the refrigerant flowing through the main refrigerant circuit when the number of operating side heat exchangers is changed. When the predetermined supercooling degree value (tSC1) becomes larger, the bypass expansion valve is operated until the main refrigerant circuit side supercooling degree becomes equal to or lower than the second predetermined supercooling degree value (tSC2). Close control,
Air conditioner (1).   The air conditioner (1) according to any one of claims 2, 3, 5, and 6, wherein the first predetermined supercooling value (tSC1) is set as a function of an outside air temperature (ta).   The value of the predetermined superheat degree (tSHs) is set to a value at which the compressor does not operate in a wet state based on a discharge temperature (td) of the compressor (21). The air conditioning apparatus (1) described in 1.

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