Refrigeration Cycle Device

This application is a continuation of International Application No. PCT/JP2024/006544, filed on Feb. 22, 2024, which is based upon and claims the benefit of priority from Japanese Patent Application No. 2023-026487 filed on Feb. 22, 2023; the entire contents of which are incorporated herein by reference.

An embodiment of the present invention relates to a refrigeration cycle device.

A refrigeration cycle device capable of simultaneously performing cooling and heating operations in a plurality of indoor units is used. In a refrigeration cycle device, it is required to suppress generation of abnormal noise.

Hereinafter, a refrigeration cycle deviceof an embodiment will be described with reference to the drawings.

A refrigeration cycle device according to an embodiment includes an outdoor unit, a plurality of indoor units, a first pipe, a second pipe, a third pipe, a switching unit, and a control unit. The outdoor unit includes a compressor and an outdoor heat exchanger. A plurality of indoor units each include an indoor expansion valve and an indoor heat exchanger. The first pipe allows a refrigerant to flow between the outdoor heat exchanger and the indoor heat exchanger. The second pipe allows the refrigerant discharged from the compressor to flow into the indoor heat exchanger. The third pipe allows the refrigerant flowing out of the indoor heat exchanger to flow into the compressor. The switching unit switches connections of the second pipe and the third pipe with respect to the indoor heat exchanger. The control unit sets an upper-limit opening degree of the indoor expansion valve when a predetermined condition is satisfied in a state in which the indoor heat exchanger is connected to the third pipe in the switching unit.

According to the refrigeration cycle device according to the embodiment, in the above-described refrigeration cycle device, the upper-limit opening degree may be a value corresponding to at least one of capacity information and configuration information of the indoor unit.

According to the refrigeration cycle device according to the embodiment, in the above-described refrigeration cycle device, the predetermined condition may be a condition in which an instruction to set the upper-limit opening degree is input to the control unit.

According to the refrigeration cycle device according to the embodiment, in the above-described refrigeration cycle device, the predetermined condition may be a condition in which a predetermined time has not elapsed after the indoor unit started a cooling operation.

The above-described refrigeration cycle device according to the embodiment further includes a trunk pipe. Branch pipes corresponding to the plurality of indoor units and the third pipe may be connected to the trunk pipe. The indoor unit corresponding to the branch pipe positioned farthest from the third pipe in an axial direction of the trunk pipe may be defined as a first indoor unit. The control unit may set the upper-limit opening degree of the indoor expansion valve of the first indoor unit when the predetermined condition is satisfied in a state in which the indoor heat exchanger of the first indoor unit is connected to the third pipe in the switching unit.

is a circuit diagram showing the refrigeration cycle deviceof the embodiment. The refrigeration cycle deviceincludes an outdoor unit, a plurality of indoor units, and a pipe. The pipeallows a refrigerant to flow between the outdoor unitand the plurality of indoor units. The refrigeration cycle deviceis a heat recovery type air conditioning system capable of simultaneously performing cooling and heating operations in the plurality of indoor units. In the example shown in, the refrigeration cycle deviceincludes four indoor units, namely a first indoor unit, a second indoor unit, a third indoor unit, and a fourth indoor unit

The refrigeration cycle devicecontains a refrigerant such as R410A, R32, R1123, R454B, R466A, or carbon dioxide (CO). The refrigerant circulates through the refrigeration cycle devicewhile changing its phase. In the present embodiment, a downstream side in a flow direction of the refrigerant may be simply referred to as a “downstream side”, and an upstream side in the flow direction of the refrigerant may be simply referred to as an “upstream side”.

The outdoor unitincludes a compressor, a check valve, a four-way valve, an outdoor heat exchanger, and an outdoor expansion valve. The four-way valveincludes a first four-way valveand a second four-way valve. The first four-way valveswitches connections of the upstream side and the downstream side of the compressorwith respect to the outdoor heat exchanger. The second four-way valveswitches connections of the second pipeand the third pipewith respect to the compressor.

The plurality of indoor unitseach have an indoor expansion valveand an indoor heat exchanger. The indoor expansion valveis, for example, an electronically controlled valve (Pulse Motor Valve: PMV). The outdoor expansion valveand the indoor expansion valvefunction as an expansion device.

The pipeincludes a first pipe, a second pipe, and a third pipe.

The first pipe (liquid pipe)allows the refrigerant to flow between the outdoor heat exchangerand the indoor heat exchanger. The outdoor expansion valveis provided in the first pipe.

The second pipe (discharge gas pipe)allows the refrigerant discharged from the compressorto flow into the indoor heat exchanger.

The third pipe (suction gas pipe)allows the refrigerant flowing out of the indoor heat exchangerto flow into the compressor.

The refrigeration cycle deviceincludes a switching unit. The switching unitswitches connections of the second pipeand the third pipewith respect to the indoor heat exchangersof the plurality of indoor units. The switching unitincludes branch pipes,, and, trunk pipes,, and, and on-off valvesand.

As the branch pipes,, and, the switching unithas a first branch pipe, a second branch pipe, and a third branch pipe. The switching unithas a plurality of first branch pipes, a plurality of second branch pipes, and a plurality of third branch pipescorresponding to the plurality of indoor units. The first branch pipeis connected to one of an inlet and an outlet of the indoor heat exchangervia the indoor expansion valve. The second branch pipeand the third branch pipemerge into a connection pipe. The connection pipeis connected to the other of the inlet and the outlet of the indoor heat exchanger.

As the trunk pipes,,, the switching unithas a first trunk pipe, a second trunk pipe, and a third trunk pipe. The first pipeand the plurality of first branch pipesare connected to the first trunk pipe. The second pipeand the plurality of second branch pipesare connected to the second trunk pipe. The third pipeand the plurality of third branch pipesare connected to the third trunk pipe. The plurality of branch pipes are connected to the first to third trunk pipes (header pipes), thereby forming first to third headers.

is a cross-sectional view showing the third trunk pipeand the third branch pipe. The third pipeis connected to one end part of the third trunk pipe. The other end part of the third trunk pipeis closed. The plurality of third branch pipesare aligned in an axial direction of the third trunk pipeand connected to intermediate portions of the third trunk pipein the axial direction. A distance from the third pipein the axial direction of the third trunk pipeis greatest at the third branch pipecorresponding to the first indoor unit. Distal ends of the plurality of third branch pipesprotrude into the inside of the third trunk pipe. The first header of the first trunk pipeand the second header of the second trunk pipeshown inare configured similarly to the third header of the third trunk pipe.

The switching unitincludes a second on-off valveand a third on-off valvewhich serve as the on-off valvesand, respectively. The second on-off valveopens and closes the second branch pipe. The third on-off valveopens and closes the third branch pipe. Only one of the second branch pipeand the third on-off valveis opened. When only the second branch pipeis opened, the second pipeis connected to the indoor heat exchangervia the second trunk pipe. When only the third on-off valveis opened, the third pipeis connected to the indoor heat exchangervia the third trunk pipe.

An outer strainerand an inner strainerare provided inside the switching unit. The outer straineris provided in the pipes,, andon the side of the outdoor unitof the trunk pipes,, and. The inner straineris provided in the first branch pipeand the connection pipeon the side of the indoor unitof the trunk pipes,, and. The outer strainerand the inner strainercapture foreign matter contained in the refrigerant flowing through the pipes.

The refrigeration cycle deviceincludes a central processing unit (CPU), a memory, an auxiliary storage device, and the like. The CPU functions as a control unitby executing a program stored in the memory and the auxiliary storage device. The control unitcontrols an operation of each part of the refrigeration cycle device. The control unitcontrols an operation of the four-way valve. The control unitcontrols operations of the outdoor expansion valveand the indoor expansion valve. The control unitcontrols operations of the on-off valvesand.

A case in which all the indoor unitsperform a cooling operation (individual cooling) will be described.

The control unitsets all the four-way valvesto the state shown in. The downstream side of the compressoris connected to the outdoor heat exchanger. The control unitopens the third on-off valvesand closes the second on-off valvescorresponding to all the indoor units. The indoor heat exchangersof all the indoor unitsare connected to the third pipe.

The compressorcompresses a low-pressure gaseous refrigerant suctioned into the inside into a high-temperature and high-pressure gaseous refrigerant. The refrigerant discharged from the compressorflows into the first four-way valvevia an oil separatorand the check valve. The refrigerant flows into the outdoor heat exchangerof the outdoor unitfrom the first four-way valve

The outdoor heat exchangerfunctions as a condenser (heat radiator). The condenser dissipates heat from a high-temperature and high-pressure gaseous refrigerant flowing in from the compressorto convert the high-temperature and high-pressure gaseous refrigerant into a high-pressure liquid refrigerant.

The refrigerant flowing out of the outdoor heat exchangerpasses through the first pipeand flows into the outdoor expansion valveand the indoor expansion valvesof all the indoor units. The outdoor expansion valveand the indoor expansion valvereduce a pressure of the high-pressure liquid refrigerant supplied from the outdoor heat exchangerand convert the high-pressure liquid refrigerant into a low-temperature and low-pressure gas-liquid two-phase refrigerant. The refrigerant flowing out of the indoor expansion valveflows into the indoor heat exchanger.

The indoor heat exchangerfunctions as an evaporator (heat absorber). The evaporator converts the gas-liquid two-phase refrigerant flowing in from the indoor expansion valveinto a low-pressure gaseous refrigerant. The refrigerant flowing out from the indoor heat exchangersof all the indoor unitspasses through the third pipeand flows into the compressorvia an accumulator (gas-liquid separator)

A case in which all the indoor unitsperform a heating operation (single heating) will be described.

The control unitswitches all the four-way valvesfrom the state shown into a switched state. Therefore, the upstream side of the compressoris connected to the outdoor heat exchanger. The second pipeis connected to the downstream side of the compressor. The control unitopens the second on-off valvesand closes the third on-off valvescorresponding to all the indoor units. The indoor heat exchangersof all the indoor unitsare connected to the second pipe.

The refrigerant discharged from the compressorpasses through the second four-way valveand the second pipe, and flows into the indoor heat exchangersof all the indoor units. The indoor heat exchangerfunctions as a condenser (heat radiator). The refrigerant flowing out of the indoor heat exchangersof all the indoor unitspasses through the indoor expansion valve, the first pipe, and the outdoor expansion valve, and flows into the outdoor heat exchanger. The outdoor heat exchangerfunctions as an evaporator (heat absorber). The refrigerant flowing out of the outdoor heat exchangerpasses through the first four-way valveand flows into the compressor.

A case in which, among the plurality of indoor units, a heating operation of the first indoor unitand cooling operations of the other indoor unitstoare simultaneously performed will be described. The refrigeration cycle deviceperforms a simultaneous operation of cooling and heating (simultaneous cooling), with cooling as a main operation.

The control unitsets a state of the first four-way valveto the state shown in. The downstream side of the compressoris connected to the outdoor heat exchanger. The control unitswitches the second four-way valvefrom the state shown in. The second pipeis connected to the downstream side of the compressor.

The control unitopens the second on-off valveand closes the third on-off valvecorresponding to the first indoor unit. The indoor heat exchangerof the first indoor unitis connected to the second pipe. The control unitopens the third on-off valvesand closes the second on-off valvescorresponding to the other indoor units,, and. The indoor heat exchangersof the other indoor units,, andare connected to the third pipe.

The refrigerant discharged from the compressorpasses through the second four-way valveand the second pipe, and flows into the first indoor unit. The indoor heat exchangerof the first indoor unitfunctions as a condenser (heat radiator). The refrigerant flowing out of the indoor heat exchangerflows into the first trunk pipe.

The refrigerant discharged from the compressorpasses through the first four-way valve, the outdoor heat exchanger, and the first pipe, and flows into the first trunk pipe. The refrigerant in the first trunk pipeflows into the other indoor units,, and. The indoor heat exchangersof the other indoor units,, andfunction as evaporators (heat absorbers). The refrigerant flowing out of these indoor heat exchangerspasses through the third pipeand flows into the compressor.

A case in which, among the plurality of indoor units, a cooling operation of the first indoor unitand heating operations of the other indoor unitstoare simultaneously performed will be described. The refrigeration cycle deviceperforms a simultaneous operation of cooling and heating (simultaneous heating), with heating as a main operation.

The control unitswitches the first four-way valvefrom the state shown into a switched state. The upstream side of the compressoris connected to the outdoor heat exchanger. The control unitsets the second four-way valveto the state shown in.

The control unitopens the third on-off valveand closes the second on-off valvecorresponding to the first indoor unit. The indoor heat exchangerof the first indoor unitis connected to the third pipe. The control unitopens the second on-off valvesand closes the third on-off valvescorresponding to the other indoor units,, and. The indoor heat exchangersof the other indoor units,, andare connected to the second pipe.

The refrigerant discharged from the compressorpasses through the second four-way valveand the second pipe, and flows into the other indoor units,, and. The indoor heat exchangersof the other indoor units,, andfunction as condensers (heat radiators). The refrigerant flowing out of these indoor heat exchangersflows into the first trunk pipe. Some of the refrigerant in the first trunk pipepasses through the first pipeand the outdoor heat exchanger, and flows into the compressor.

A remaining portion of the refrigerant in the first trunk pipeflows into the first indoor unit. The indoor heat exchangerof the first indoor unitfunctions as an evaporator (heat absorber). The refrigerant flowing out of the indoor heat exchangerpasses through the third pipeand flows into the compressor.

An abnormal noise generated during the cooling operation of the indoor unitwill be described.

When the indoor unitperforms the cooling operation, the indoor heat exchangerfunctions as an evaporator (heat absorber). The indoor heat exchangerchanges the gas-liquid two-phase refrigerant into a low-pressure gaseous refrigerant. When the indoor unitperforms the cooling operation, the third on-off valveis opened and the second on-off valveis closed. The indoor heat exchangeris connected to the third pipe. The refrigerant flowing out of the indoor heat exchangerpasses through the connection pipe, the third branch pipe, the third trunk pipe, and the third pipe, and flows into the compressor.

There are cases in which the gas-liquid two-phase refrigerant flows out from the indoor heat exchanger. If the liquid refrigerant contained in the gas-liquid two-phase refrigerant flows into the compressor, the compressormay fail. The control unitsets a target value of a degree of superheat of the refrigerant flowing out of the indoor heat exchanger. The control unitcontrols an opening degree of the indoor expansion valveso that the degree of superheat exceeds the target value. When the degree of superheat exceeds the target value, an outflow of the liquid refrigerant from the indoor heat exchangeris suppressed.

When the operation of the indoor unitstarts or stops, when a rotation speed of the compressorchanges, or the like, the degree of superheat may fall below the target value. In this case, the gas-liquid two-phase refrigerant containing the liquid refrigerant flows out from the indoor heat exchanger. Abnormal noise is generated in a process in which the liquid refrigerant flows through the connection pipe, the third branch pipe, the third trunk pipe, and the third pipe. The abnormal noise is a keen sound of approximately 4 to 7 Hz. The abnormal noise is generated in the inner strainerprovided in the connection pipe, the third on-off valveprovided in the third branch pipe, inside the third trunk pipe, the outer strainerprovided in the third pipe, or the like. As shown in, a distal end of the third branch pipeprotrudes into the inside of the third trunk pipe. When the liquid refrigerant flows inside the third trunk pipe, if a vortex is generated at the distal end of the third branch pipe, a risk of abnormal noise generation increases.

When a predetermined condition is satisfied, the control unitperforms a refrigerant flow rate suppression operation of the indoor unitperforming the cooling operation. As the refrigerant flow rate suppression operation, the control unitsets an upper-limit opening degree (an upper-limit value of the opening degree) of the indoor expansion valveof the indoor unitperforming the cooling operation. The upper-limit opening degree is a predetermined constant value according to the refrigeration cycle device. The upper-limit opening degree is an opening degree of the indoor expansion valveat which the degree of superheat becomes greater than the target value when the indoor unitoperates under a rated cooling condition. For example, if the indoor expansion valvehas an opening control range of 0 to 500 pls, the upper-limit opening degree is set to 150 pls.

The control unitcontrols the opening degree of the indoor expansion valveto be lower than or equal to the upper-limit opening degree. A flow rate of the refrigerant flowing through the indoor heat exchangeris restricted. Since heat exchange in the indoor heat exchangeris performed on a small amount of refrigerant, a temperature of the refrigerant is likely to increase. The degree of superheat of the refrigerant flowing out of the indoor heat exchangerexceeds the target value. An outflow of the liquid refrigerant from the indoor heat exchangeris suppressed. Generation of abnormal noise associated with the flow of the liquid refrigerant is suppressed.

The upper-limit opening degree is a value corresponding to at least one of capacity information and configuration information of the indoor unit. Generally, a refrigerant circulation amount varies depending on the capacity and configuration of the indoor unit. The upper-limit opening degree is set to achieve a balance between performance of the indoor unitand suppression of abnormal noise.