Patent Description:
In the past, a refrigeration cycle apparatus including a cooling mechanism for a controller has been known. Patent Literature <NUM> discloses a refrigeration cycle apparatus in which after part of refrigerant is bypassed from a high-pressure side of a refrigerant circuit and is made to transfer heat in a precooling heat exchanger, the refrigerant is made to flow to a refrigerant cooler and is made to exchange heat with a controller, thereby cooling the controller. After cooling the controller in the refrigerant cooler, the part of refrigerant that has been bypassed from the high-pressure side of the refrigerant circuit passes through an expansion device for controlling the flow rate of the refrigerant in the refrigerant cooler and flows to a low-pressure side of the refrigerant circuit.

Patent Literature <NUM> relates to a heat pump cooling and heating device capable of effectively recovering a plate heat amount accompanying such cooling as a defrosting heat source while efficiently cooling an electric heating component. Furthermore, patent Literature <NUM> discloses a refrigeration cycle apparatus according to the preamble of claim <NUM>.

Patent Literature <NUM>, according to its abstract, states that a refrigeration cycle device equipped with: a refrigerant circuit through which a refrigerant flows, and equipped with a compressor, a heat-source-side heat exchanger, a first throttling device, and a load-side heat exchanger; a control device for controlling the refrigerant circuit; a bypass pipe that branches off from a high-pressure pipe extending from the compressor to the first throttling device, and is connected to a low-pressure pipe on the intake side of the compressor; a preliminary cooling heat exchanger that is provided in the bypass pipe, and cools the refrigerant which is bypassed to the bypass pipe; a second throttling device that is provided in the bypass pipe, and depressurizes the refrigerant which has been cooled by the preliminary cooling heat exchanger; and a refrigerant cooling device that is provided in the bypass pipe, and cools the control device by using the refrigerant which has been depressurized by the second throttling device.

Patent Literature <NUM>, according to its abstract, states that a refrigeration apparatus includes a refrigerant circuit having a main circuit performing a refrigeration cycle and a branch circuit which branches part of high-pressure liquid refrigerant flowing through the main circuit and leads the part of high-pressure liquid refrigerant from a high-pressure part of the main circuit to part of the main circuit having a pressure lower than that of the high-pressure part. The branch circuit is connected to a cooler configured to cool a power element(s) of a power supply device supplying power to drivers of components of the refrigerant circuit by refrigerant. In the refrigeration apparatus, an adjusting mechanism configured to adjust the state of refrigerant flowing through the branch circuit and adjust the temperature of refrigerant passing through the cooler to a target temperature is provided.

The refrigeration cycle apparatus disclosed in Patent Literature <NUM>, however, bypasses refrigerant from a high-pressure side between a discharge side of a compressor and a heat-source-side heat exchanger or a load-side heat exchanger, and returns the refrigerant to a low-pressure side. Therefore, the flow rate of refrigerant that flows in the heat-source-side heat exchanger or the load-side heat exchanger is reduced by the amount of the bypassed refrigerant. Accordingly, the heating and cooling capacity of the refrigeration cycle apparatus may be decreased.

The present invention is applied to solve the above problem, and relates to a refrigeration cycle apparatus that reduces a decrease in its heating and cooling capacity.

According to the present invention, a refrigeration cycle apparatus as defined in independent claim <NUM> is provided. Further embodiments of the claimed invention are defined in the dependent claims. Although the claimed invention is only defined by the claims, the below embodiments, examples, and aspects are present for aiding in understanding the background and advantages of the claimed invention.

According to the present invention , the bypass pipe, at which the refrigerant cooler configured to cool the controller is provided, extends from the liquid pipe between the first expansion device and the second expansion device toward the suction side of the compressor. Therefore, the refrigerant discharged from the compressor flows to the heat-source-side heat exchanger or the load-side heat exchanger without being bypassed. It is therefore possible to avoid a loss in the capacity that would occurs if the refrigerant discharged from the compressor were bypassed. Accordingly, it is possible to reduce a decrease in the heating and cooling capacity.

An embodiment of a refrigeration cycle apparatus according to the present invention is described below with reference to the drawings. The present invention is not limited to the embodiment described below. The relationships in size between components in figures including <FIG> that will be referred to below may differ from those of actual ones. In the following descriptions, in order that the present disclosure be easily understood, terms related to directions are used as appropriate. However, the terms are used only for explanation of the present disclosure, but do not limit the present disclosure. As examples of the terms, "upper", "lower", "right", "left", "front", "rear", etc., are present.

<FIG> is a circuit diagram illustrating a refrigeration cycle apparatus according to Embodiment <NUM>. Embodiment <NUM> will be described by referring to the case where a refrigeration cycle apparatus <NUM> is an air-conditioning apparatus. The refrigeration cycle apparatus <NUM> is installed, for example, in a building or a condominium, and performs a cooling operation or a heating operation with a heat pump cycle, which is a refrigeration cycle of a refrigeration cycle circuit in which refrigerant is circulated.

As illustrated in <FIG>, the refrigeration cycle apparatus <NUM> includes a heat-source-side unit <NUM> and load-side units <NUM>. In the refrigeration cycle apparatus <NUM>, the heat-source-side unit <NUM> and each of the load-side units <NUM> are connected by a gas pipe <NUM> and a liquid pipe <NUM>, whereby a refrigeration cycle circuit is formed. The gas pipe <NUM> includes a gas main pipe 401A and gas branch pipes 401a and 401b. The liquid pipe <NUM> includes a liquid main pipe 402A and liquid branch pipes 402a and 402b. Regarding Embodiment <NUM>, it is illustrated by way example that two load-side units 300a and 300b are provided as load-side units <NUM>. However, the number of load-side units <NUM> may be one, or may be three or more.

The heat-source-side unit <NUM> has a function of supplying cooling energy or heating energy to the load-side unit <NUM>.

The heat-source-side unit <NUM> includes a compressor <NUM>, a flow switching device <NUM>, a heat-source-side heat exchanger <NUM>, a first expansion device <NUM>, and an accumulator <NUM>. These components are connected in series to form part of a main refrigerant circuit. The heat-source-side unit <NUM> is provided with a heat-source-side fan <NUM>.

The compressor <NUM> sucks low-temperature and low-pressure gas refrigerant, compresses the low-temperature and low-pressure gas refrigerant to change it into high-temperature and high-pressure gas refrigerant, discharges the high-temperature and high-pressure gas refrigerant, causes the refrigerant to circulate in the refrigerant circuit to perform an operation related to air-conditioning. The compressor <NUM> may be, for example, an inverter compressor whose capacity can be controlled. The compressor <NUM> is not limited to such an inverter compressor whose capacity can be controlled. For example, the compressor <NUM> may be a fixed-speed compressor or a compressor obtained by combining an inverter compressor and a fixed-speed compressor. Any type of compressor may be used as the compressor <NUM> as long as it can compress sucked refrigerant to change it into high-pressure refrigerant; that is, the compressor <NUM> is not limited to a specific type compressor. As the compressor <NUM>, for example, one of the following various types of compressors may be used: a reciprocating compressor; rotary compressor; a scroll compressor; and a screw compressor.

The flow switching device <NUM> is provided on a discharge side of the compressor <NUM>, and switches a refrigerant flow passage between a refrigerant flow passage in the cooling operation and that in the heating operation. The flow switching device <NUM> controls the flow of the refrigerant depending on which of operation modes is set, such that the heat-source-side heat exchanger <NUM> operates as an evaporator or a condenser. In Embodiment <NUM>, the flow switching device <NUM> is, for example, a four-way valve. However, the flow switching device <NUM> may be a plurality of three-way valves, a plurality of two-way valves, or other elements.

The heat-source-side heat exchanger <NUM> causes heat exchange to be performed between refrigerant and a heat medium that is, for example, ambient air or water. In the heating operation, the heat-source-side heat exchanger <NUM> operates as the evaporator and causes the refrigerant to evaporate and gasify. In the cooling operation, the heat-source-side heat exchanger <NUM> operates as the condenser or a radiator and causes the refrigerant to condense and liquefy.

As in Embodiment <NUM>, in the case where the heat-source-side heat exchanger <NUM> is an air-cooled heat exchanger, the heat-source-side unit <NUM> includes a fan, such as the heat-source-side fan <NUM>. In order to control a condensing performance or an evaporating performance of the heat-source-side heat exchanger <NUM>, for example, a controller <NUM> may control the rotation speed of the heat-source-side fan <NUM>. In the case where the heat-source-side heat exchanger <NUM> is a water-cooled heat exchanger, the controller <NUM> controls the rotation speed of a water circulating pump (not illustrated), thereby controlling the condensing performance or the evaporating performance of the heat-source-side heat exchanger <NUM>.

The first expansion device <NUM> has the function of a pressure reducing valve or an expansion valve, and decompresses and expands the refrigerant. The first expansion device <NUM> may be formed as an expansion device whose opening degree is variably controllable, for example, an elaborate flow-rate control device that is an electronic expansion valve or an inexpensive refrigerant flow-rate adjusting unit, such as a capillary tube.

The first expansion device <NUM> controls a pressure on an upstream side of the first expansion device <NUM> that is an intermediate pressure in the heating operation. It should be noted that the first expansion device <NUM> adjusts the pressure of refrigerant that flows through a bypass pipe <NUM>, which will be described below. That is, the first expansion device <NUM> adjusts the difference between the pressure of refrigerant that has not yet passed through a third expansion device <NUM> provided at the bypass pipe <NUM> and the pressure of refrigerant that has passed through the third expansion device <NUM>. In the case where the third expansion device <NUM> is fully opened, when it is required to increase the flow rate of refrigerant to be bypassed, the first expansion device <NUM> is operated to increase the difference between the pressure of refrigerant that has not yet passed through the third expansion device <NUM> and the pressure of refrigerant that has passed through the third expansion device <NUM>, to thereby increase the flow rate of refrigerant to be bypassed.

The accumulator <NUM> is provided on a suction side of the compressor <NUM>, and has a function of separating liquid refrigerant and gas refrigerant and a function of accumulating surplus refrigerant.

The heat-source-side unit <NUM> includes a high-pressure sensor <NUM> that detects the pressure of high-pressure refrigerant discharged from the compressor <NUM>. Also, the heat-source-side unit <NUM> includes a low-pressure sensor <NUM> that detects the pressure of low-pressure refrigerant to be sucked into the compressor <NUM>. The heat-source-side unit <NUM> further includes an outside temperature sensor <NUM> that detects an outside air temperature, a control temperature detector <NUM> that detects the temperature of the controller <NUM>, and a suction-side temperature sensor <NUM> that detects the temperature of refrigerant to flow into the accumulator <NUM>. The heat-source-side unit <NUM> further includes an opening-degree detector 602a that detects the opening degree of the third expansion device <NUM>. Those sensors send signals related to the detected pressures and signals related to the detected temperatures to the controller <NUM>, which is configured to control operations of the refrigeration cycle apparatus <NUM>. The suction-side temperature sensor <NUM> and the low-pressure sensor <NUM> form a degree-of-superheat detector. It should be noted that any detector can be used as the degree-of-superheat detector as long as it can detect the degree of superheat at an outlet of a refrigerant cooler <NUM>, and a temperature sensor that detects the temperature of refrigerant at an inlet of the refrigerant cooler <NUM> may be used in place of the low-pressure sensor <NUM>.

Each of the load-side units <NUM> supplies cooling energy or heating energy from the heat-source-side unit <NUM> to a cooling load or a heating load. For example, referring to <FIG>, reference sings that denote the components included in the "load-side unit 300a" include the suffix a, and reference signs that denote the components included in the "load-side unit 300b" include the suffix b. In the following description, although the suffixes a and b may be omitted, the load-side units 300a and 300b include respective components.

The load-side units 300a and 300b are provided with load-side heat exchangers 312a and 312b and second expansion devices 311a and 311b, respectively. The load-side heat exchangers 312a and 312b and the second expansion devices 311a and 311b are connected in series, respectively, and form along with the heat-source-side unit <NUM> the refrigerant circuit. Furthermore, a fan (not illustrated) that supplies air to the load-side heat exchanger <NUM> may be provided. The load-side heat exchanger <NUM> may cause heat exchange to be performed between the refrigerant and a heat medium such as water, which is different from the refrigerant.

The load-side heat exchanger <NUM> causes heat exchange to be performed between the refrigerant and a heat medium, such as ambient air or water. In the heating operation, the load-side heat exchanger <NUM> operates as a condenser or a radiator to cause the refrigerant to condense and liquefy, and in the cooling operation, the load-side heat exchanger <NUM> operates as an evaporator to cause the refrigerant to evaporate and gasify. In general, the load-side heat exchanger <NUM> may be provided along with the fan (not illustrated), and the condensing performance or evaporating performance of the load-side heat exchanger <NUM> can be controlled by controlling the rotation speed of the fan. In Embodiment <NUM>, each of the load-side heat exchangers 312a and 312b is provided as the load-side heat exchanger <NUM>.

The second expansion device <NUM> has the function of a pressure reducing valve or an expansion valve, and decompresses and expands the refrigerant. The second expansion device <NUM> may be an expansion device whose opening degree is variably controllable, and for example, an elaborate flow rate control device such as an electronic expansion valve or an inexpensive refrigerant flow-rate adjusting unit, such as a capillary tube. In Embodiment <NUM>, each of the second expansion devices 311a and 311b is provided as the second expansion device <NUM>.

The load-side units <NUM> include respective low-temperature-side pipe temperature sensors 314a and 314b each of which detects the temperature of a refrigerant pipe between the second expansion device <NUM> and the load-side heat exchanger <NUM>. It should be noted that the low-temperature-side pipe temperature sensors 314a and 314b may be referred to as low-temperature-side pipe temperature sensors <NUM>. The load-side units <NUM> includes respective high-temperature-side pipe temperature sensors 313a and 313b each of which detects the temperature of a refrigerant pipe between the load-side heat exchanger <NUM> and the flow switching device <NUM>. It should be noted that the high-temperature-side pipe temperature sensors 313a and 313b may be referred to as high-temperature-side pipe temperature sensors <NUM>. Temperature information detected by the above sensors is sent to the controller <NUM>, which controls the operations of the refrigeration cycle apparatus <NUM>, and are used in control of various actuators. That is, in each of the load-side units <NUM>, temperature information from the high-temperature-side pipe temperature sensor <NUM> and the low-temperature-side pipe temperature sensor <NUM> is used in control of the opening degree of the second expansion device <NUM> included in the load-side unit <NUM>, the rotation speed of the fan (not illustrated), and other factors.

It should be noted that the kind of refrigerant for use in the refrigeration cycle apparatus <NUM> is not particularly limited. For example, as the refrigerant, one of the following kinds of refrigerants may be used: natural refrigerant such as carbon dioxide, hydrocarbon, or helium; alternative refrigerant that includes no chlorine, such as HFC410A, HFC407C, or HFC404A, and fluorocarbon refrigerant for use in an existing product, such as R22 or R134a.

<FIG> illustrates by way of example the case where the controller <NUM>, which controls the operations of the refrigeration cycle apparatus <NUM>, is provided in the heat-source-side unit <NUM>. However, the controller <NUM> may be provided in the load-side unit <NUM>. Alternatively, the controller <NUM> may be provided outside the heat-source-side unit <NUM> and the load-side units <NUM>. The controller <NUM> may be divided into a plurality of controllers <NUM> having respective functions, and the controllers <NUM> may be assigned to the heat-source-side unit <NUM> and the load-side units <NUM>; that is, the heat-source-side unit <NUM> and the load-side units <NUM> include respective controllers <NUM>. In this case, it is preferable that the controllers <NUM> be connected to each other wirelessly or by a cable such that they can communicate with each other.

The heat-source-side unit <NUM> further includes the bypass pipe <NUM>. The bypass pipe <NUM> branches off from the liquid pipe <NUM> between the first expansion device <NUM> and the second expansion device <NUM>, and is connected to a low-pressure pipe <NUM> on the suction side of the compressor <NUM>. Liquid refrigerant or two-phase gas-liquid refrigerant that flows in the liquid pipe <NUM> is bypassed; that is, the liquid refrigerant or two-phase gas-liquid refrigerant is made to flow into the bypass pipe <NUM>. At the bypass pipe <NUM>, the third expansion device <NUM> and the refrigerant cooler <NUM> are provided. The third expansion device <NUM> adjusts the flow rate of the bypassed refrigerant, and the refrigerant cooler <NUM> cools the controller <NUM>.

The third expansion device <NUM> has the function of a pressure reducing valve or an expansion valve, and decompresses and expands the refrigerant. The third expansion device <NUM> further decompresses the refrigerant that has been cooled in the heat-source-side heat exchanger <NUM> or the load-side heat exchanger <NUM> and that has been decompressed in the first expansion device <NUM> or the second expansion device <NUM>. The third expansion device <NUM> has a function of causing the refrigerant, with the temperature of the refrigerant further lowered, to flow into the refrigerant cooler <NUM>. The third expansion device <NUM> is an expansion device whose opening degree is variably controllable, such as an electronic expansion valve.

The refrigerant cooler <NUM> includes a refrigerant pipe that allows the refrigerant to pass therethrough and that is provided in contact with the controller <NUM>. The refrigerant that has flowed into the bypass pipe <NUM> flows into the refrigerant cooler <NUM> at a flow rate adjusted by the third expansion device <NUM>. The liquid refrigerant that has flowed into the refrigerant cooler <NUM> receives heat generated in the controller <NUM> to change into gas refrigerant. The gas refrigerant passes through a downstream-side pipe <NUM> located on a downstream side and flows into the accumulator <NUM> through the low-pressure pipe <NUM>.

<FIG> is a schematic sectional view illustrating a connection between the liquid pipe <NUM> and the bypass pipe <NUM> in the refrigeration cycle apparatus <NUM> according to Embodiment <NUM>. Next, the connection between the liquid pipe <NUM> and the bypass pipe <NUM> will be described. As illustrated in <FIG>, the bypass pipe <NUM> is connected to lower part of the liquid pipe <NUM>. Specifically, the bypass pipe <NUM> is located at a lower position than a horizontal plane in which the liquid pipe <NUM> is located.

In the case where the refrigerant that flows in the liquid pipe <NUM> is the two-phase gas-liquid refrigerant, it is a mixture of liquid refrigerant and gas refrigerant. In this case, as illustrated in <FIG>, refrigerant <NUM> that is the liquid refrigerant remains in the lower part of the liquid pipe <NUM>, and refrigerant <NUM> that is the gas refrigerant remains in upper part of the liquid pipe <NUM>. In order that the controller <NUM> be cooled by the refrigerant, it is necessary that the refrigerant be the liquid refrigerant. In Embodiment <NUM>, because the bypass pipe <NUM> is connected to the lower part of the liquid pipe <NUM>, refrigerant that is bypassed to flow into the bypass pipe <NUM> is the liquid refrigerant <NUM>. Thus, in Embodiment <NUM>, because the liquid refrigerant <NUM>, whose enthalpy is low, can be bypassed, even if the difference between the pressure of the refrigerant that has not yet passed through the third expansion device <NUM> and that of the refrigerant that has passed through the third expansion device <NUM> is small, and the flow rate of the refrigerant is low, it is possible to ensure the cooling performance required for cooling the controller <NUM>.

<FIG> is a hardware configuration diagram illustrating the controller <NUM> in the refrigeration cycle apparatus <NUM> according to Embodiment <NUM>. As illustrated in <FIG>, the controller <NUM> is a CPU 118c (central processing unit, also referred to as a processing unit, an arithmetic unit, a microprocessor, a microcomputer, or a processor) that executes a program input from an input section 118a and stored in dedicated hardware or a storage device 118b and drives an inverter circuit 118d. In the case where the controller <NUM> is the dedicated hardware, the controller <NUM> corresponds to, for example, a single circuit, a composite circuit, an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or combinations of these circuits. Each of the functions to be fulfilled the controller <NUM> may be fulfilled by respective hardware or may be fulfilled by single hardware.

In the case where the controller <NUM> is the CPU 118c, the functions to be fulfilled by the controller <NUM> are fulfilled by software, firmware, or a combination of software and firmware. The software and firmware are described as a program, and the program is stored in the storage device 118b. The CPU 118c reads the program from the storage device 118b and executes the program, thereby fulfilling the functions. Some functions of the controller <NUM> may be fulfilled by dedicated hardware, and other functions of the controller <NUM> may be fulfilled by software or firmware. The controller <NUM> may be formed as a hard disk, or may be formed as a volatile storage device, such as a random access memory (RAM), which can temporarily store data. The storage device 118b may be formed as a nonvolatile storage device, such as a flash memory, which can store data for a long time. It should be noted that in Embodiment <NUM>, the controller <NUM> is provided in the heat-source-side unit <NUM>; however, the controller <NUM> may be provided at any location as long as it can control components, etc..

The controller <NUM> controls, for example, the driving frequency of the compressor <NUM>, the rotation speed of the heat-source-side fan <NUM>, and a switching operation of the flow switching device <NUM> on the basis of a high pressure and a low pressure. The controller <NUM> decreases the opening degree of the first expansion device <NUM>, when the temperature detected by the control temperature detector <NUM> is higher than or equal to a temperature threshold, and the opening degree of the third expansion device <NUM> detected by the opening-degree detector 602a is higher than or equal to an opening-degree threshold. The controller <NUM> controls the third expansion device <NUM> on the basis of the pressure and temperature detected by the sensors.

The controller <NUM> decreases the opening degree of the first expansion device <NUM> when the degree of superheat that is detected by the degree-of-superheat detector is lower than or equal to a degree-of-superheat threshold.

Next, operations of the refrigeration cycle apparatus <NUM> will be described. The refrigeration cycle apparatus <NUM> receives a cooling request or a heating request from a remote controller or other components provided in, for example, an indoor space. In response to this request, the refrigeration cycle apparatus <NUM> performs one of air-conditioning operations corresponding to two operation modes. The two operation modes are a cooling operation mode and a heating operation mode.

<FIG> is a circuit diagram indicating the flow of the refrigerant in the cooling operation mode in the refrigeration cycle apparatus <NUM> according to Embodiment <NUM>. It will be described with reference to <FIG> how the refrigeration cycle apparatus <NUM> is operated in the cooling operation mode.

As illustrated in <FIG>, the compressor <NUM> compresses low-temperature and low-pressure refrigerant to change it into high-temperature and high-pressure gas refrigerant, and discharges the high-temperature and high-pressure gas refrigerant. The high-temperature and high-pressure gas refrigerant discharged from the compressor <NUM> flows through a high-pressure pipe <NUM> and the flow switching device <NUM> and flows into the heat-source-side heat exchanger <NUM>. Since the heat-source-side heat exchanger <NUM> operates as a condenser, the refrigerant exchanges heat with ambient air sent from the heat-source-side fan <NUM>, and condenses to change into liquid refrigerant. After flowing out of the heat-source-side heat exchanger <NUM>, the liquid refrigerant is decompressed by the first expansion device <NUM>. The decompressed refrigerant passes through the liquid main pipe 402A and flows out of the heat-source-side unit <NUM>.

The liquid refrigerant that has flowed out of the heat-source-side unit <NUM> flows through the liquid branch pipes 402a and 402b and flows into the load-side units 300a and 300b. The liquid refrigerant that has flowed into the load-side units 300a and 300b is decompressed in the second expansion devices 311a and 311b to change into low-temperature two-phase gas-liquid refrigerant. The low-temperature two-phase gas-liquid refrigerant flows into the load-side heat exchangers 312a and 312b. Since the load-side heat exchangers 312a and 312b operate as evaporators, the refrigerant exchanges heat with ambient air, and evaporates to change into gas refrigerant. At that time, the refrigerant receives heat from the surrounding areas, whereby air-conditioning target space, such as indoor space, is cooled. Then, after flowing out of the load-side heat exchangers 312a and 312b, the refrigerant passes through the gas branch pipes 401a and 401b and flows out of the load-side units 300a and 300b.

The refrigerant that has flowed out of the load-side units 300a and 300b passes through the gas main pipe 401A and returns to the heat-source-side unit <NUM>. The gas refrigerant that has returned to the heat-source-side unit <NUM> is re-sucked into the compressor <NUM> through the flow switching device <NUM> and the accumulator <NUM>. In the above flow, the refrigeration cycle apparatus <NUM> performs the cooling operation in the cooling operation mode.

<FIG> is a circuit diagram illustrating the flow of the refrigerant in the heating operation mode in the refrigeration cycle apparatus <NUM> according to Embodiment <NUM>. It will be described with reference to <FIG> how the refrigeration cycle apparatus <NUM> is operated in the heating operation mode.

As illustrated in <FIG>, the compressor <NUM> compresses low-temperature and low-pressure refrigerant to change it into high-temperature and high-pressure gas refrigerant and discharges the high-temperature and high-pressure gas refrigerant. The high-temperature and high-pressure gas refrigerant discharged from the compressor <NUM> flows through the high-pressure pipe <NUM> and the flow switching device <NUM> and flows into the gas pipe <NUM>. Thereafter, the high-temperature and high-pressure gas refrigerant flows out of the heat-source-side unit <NUM>. The high-temperature and high-pressure gas refrigerant that has flowed out of the heat-source-side unit <NUM> flows through the gas branch pipes 401a and 401b and flows into the load-side units 300a and 300b.

The gas refrigerant that has flowed into the load-side units 300a and 300b flows into the load-side heat exchangers 312a and 312b. Since the load-side heat exchangers 312a and 312b operate as condensers, the refrigerant exchanges heat with ambient air, and condenses to change into liquid refrigerant. At this time, the refrigerant transfers heat to the surrounding area, whereby the air-conditioning target space, such as the indoor space, is heated. After that, after flowing out of the load-side heat exchangers 312a and 312b, the liquid refrigerant is decompressed in the second expansion devices 311a and 311b, passes through the liquid branch pipes 402a and 402b, and flows out of the load-side units 300a and 300b.

The refrigerant that has flowed out of the load-side units 300a and 300b passes through the liquid main pipe 402A and returns to the heat-source-side unit <NUM>. The gas refrigerant that has returned to the heat-source-side unit <NUM> flows into the heat-source-side heat exchanger <NUM>. Since the heat-source-side heat exchanger <NUM> operates as an evaporator, the refrigerant exchanges heat with ambient air sent from the heat-source-side fan <NUM>, and evaporates to change into gas refrigerant. After that, after flowing out of the heat-source-side heat exchanger <NUM>, the refrigerant flows into the accumulator <NUM> through the flow switching device <NUM>. The refrigerant in the accumulator <NUM> is sucked by the compressor <NUM>, and is circulated in the refrigerant circuit, thereby achieving the refrigeration cycle. In the above flow, the refrigeration cycle apparatus <NUM> performs the heating operation in the heating operation mode.

Next, refrigerant cooling control of cooling the controller <NUM> using the refrigerant will be described.

The refrigerant cooling control is control of cooling the controller <NUM> using the refrigerant, and the refrigerant cooling control in the cooling operation mode is similar to that in the heating operation mode.

<FIG> is a circuit diagram indicating the flow of the refrigerant in the cooling operation mode in the refrigerant cooling control in the refrigeration cycle apparatus <NUM> according to Embodiment <NUM>. First of all, the refrigerant cooling control will be described with reference to the figure illustrating the flow of the refrigerant in the cooling operation mode.

As illustrated in <FIG>, in the refrigerant cooling control, the third expansion device <NUM> is opened, whereby part of the liquid refrigerant or the two-phase gas-liquid refrigerant that is decompressed by the first expansion device <NUM> and flows in the liquid pipe <NUM> is bypassed to flow into the bypass pipe <NUM>. The bypassed refrigerant is decompressed by the third expansion device <NUM> such that the pressure of the refrigerant is reduced to a lower pressure, and the refrigerant then flows into the refrigerant cooler <NUM>. The refrigerant that has flowed into the refrigerant cooler <NUM> exchanges heat with the controller <NUM> and evaporates. The refrigerant that has cooled the controller <NUM> changes into gas refrigerant or two-phase gas-liquid refrigerant, and the gas refrigerant or two-phase gas-liquid refrigerant flows into the downstream-side pipe <NUM> and the low-pressure pipe <NUM> and flows into the accumulator <NUM>.

<FIG> is a circuit diagram indicating the flow of the refrigerant in the heating operation mode in the refrigerant cooling control in the refrigeration cycle apparatus <NUM> according to Embodiment <NUM>. Next, the refrigerant cooling control will be described with reference to the figure indicating the flow of the refrigerant in the heating operation mode.

As illustrated in <FIG>, in the refrigerant cooling control, the third expansion device <NUM> is opened, whereby part of the liquid refrigerant or the two-phase gas-liquid refrigerant that is decompressed by the second expansion device <NUM> and flows through the liquid pipe <NUM> is bypassed to flow into the bypass pipe <NUM>. The bypassed refrigerant is decompressed by the third expansion device <NUM> such that the pressure of the refrigerant is lowered to a lower pressure, and the refrigerant then flows into the refrigerant cooler <NUM>. The refrigerant that has flowed into the refrigerant cooler <NUM> exchanges heat with the controller <NUM> and evaporates. The refrigerant that has cooled the controller <NUM> changes into gas refrigerant or two-phase gas-liquid refrigerant, and the gas refrigerant or two-phase gas-liquid refrigerant flows into the downstream-side pipe <NUM> and the low-pressure pipe <NUM> and flows into the accumulator <NUM>.

The flow rate of the refrigerant that flows in the refrigerant cooler <NUM> is adjusted by the third expansion device <NUM>. The third expansion device <NUM> is controlled by the controller <NUM> on the basis of information obtained from the low-pressure sensor <NUM>, the control temperature detector <NUM>, the suction-side temperature sensor <NUM>, and the outside temperature sensor <NUM>. Specific control of the third expansion device <NUM> will be described below.

<FIG> is a flowchart indicating control of the third expansion device <NUM> in the refrigerant cooling control in the refrigeration cycle apparatus <NUM> according to Embodiment <NUM>. <FIG> indicates a summary of operations of the third expansion device <NUM> based on the flowchart of <FIG>. In the following description, temperatures (A) to (D) satisfy (B) < (D) < (C) < (A).

As indicated in <FIG> and <FIG>, in an initial state, the third expansion device <NUM> is in a closed state. After an operation of the refrigeration cycle apparatus <NUM> starts, the controller <NUM> determines whether the temperature detected by the control temperature detector <NUM> is higher than or equal to a start temperature (A) determined in advance, for example, <NUM> degrees C (step S1). When the detected temperature is lower than the start temperature (A) (No in step S1), it is not necessary to cool the controller <NUM>, and the present opening degree of the third expansion device <NUM> is thus maintained, that is, the third expansion device <NUM> is kept in the closed state (step S2), thereby preventing the refrigerant from flowing into the refrigerant cooler <NUM>. By contrast, when the detected temperature by the control temperature detector <NUM> is higher than or equal to the start temperature (A) (Yes in step S1), the controller <NUM> opens the third expansion device <NUM> to a fixed opening degree determined in advance (step S3). Thus, the refrigerant flows into the refrigerant cooler <NUM>, and starts cooling the controller <NUM>, whereby the temperature of the controller <NUM> is lowered.

The controller <NUM> checks the temperature detected by the control temperature detector <NUM> and determines whether this detected temperature is lower than or equal to an end temperature (B) determined in advance, for example (step S4). When the temperature detected by the control temperature detector <NUM> is lower than or equal to the end temperature (B) (Yes at step S4), the controller <NUM> closes the third expansion device <NUM> and ends the cooling of the controller <NUM> (step S5), and the processing returns to step S1. By contrast, when the temperature detected by the control temperature detector <NUM> is higher than the end temperature (B) (No at step S4), it is necessary to continue the cooling, and the controller <NUM> thus determines whether the temperature detected by the control temperature detector <NUM> is lower than or equal to an outside air temperature (D) (step S6). This determination is made to prevent condensation from occurring at the controller <NUM>.

When the temperature detected by the control temperature detector <NUM> drops to the outside air temperature (D) or below (Yes in step S6), condensation will occur at the controller <NUM>, the controller <NUM> thus closes the third expansion device <NUM> and ends the cooling of the controller <NUM> (step S5), and the processing returns to step S1. By contrast, when the temperature detected by the control temperature detector <NUM> is higher than the outside air temperature (D) (No in step S6), the controller <NUM> determines whether the temperature detected by the control temperature detector <NUM> is lower than a temperature threshold (C) that is a target temperature determined in advance, for example, <NUM> degrees C (step S7).

When the temperature detected by the control temperature detector <NUM> is lower than the temperature threshold (C) (Yes at step S7), the controller <NUM> reduces the opening degree of the third expansion device <NUM> such that the temperature of the controller <NUM> reaches the temperature threshold (C) (step S8), and the processing returns to the determination at step S4. It should be noted that when the temperature detected by the control temperature detector <NUM> is equal to the temperature threshold (C), the present opening degree may be maintained. When the temperature detected by the control temperature detector <NUM> is higher than or equal to the temperature threshold (C) (No in step S7), in order that the cooling be continued, the controller <NUM> increases the opening degree of the third expansion device <NUM> such that the temperature detected by the control temperature detector <NUM> reaches the temperature threshold (C) (step S9). It should be noted that in the case where the present opening degree of the third expansion device <NUM> is maintained, when the temperature detected by the control temperature detector <NUM> tends to drop, the controller <NUM> maintains the present opening degree of the third expansion device <NUM>. The processing returns to step S4, and the same processes as described above are repeated.

Next, control of the first expansion device <NUM> will be described.

<FIG> is a flowchart indicating control of the first expansion device <NUM> in the refrigerant cooling control in the refrigeration cycle apparatus <NUM> according to Embodiment <NUM>. As indicated in <FIG>, in an initial state, the first expansion device <NUM> is in an opened state at an optional opening degree (step S20). The controller <NUM> first starts the operation of the refrigeration cycle apparatus <NUM> and then controls the third expansion device <NUM> according to the flowchart of <FIG>. In the flowchart of <FIG>, when the temperature detected by the control temperature detector <NUM> is higher than or equal to the temperature threshold (C) (No in step S7 in <FIG>), control of increasing the opening degree of the third expansion device <NUM> is performed (step S9 in <FIG>). In the case where the temperature detected by the control temperature detector <NUM> does not drop even when the opening degree of the third expansion device <NUM> is increased, the opening degree of the third expansion device <NUM> is continuously increased to the highest opening degree thereof.

When the third expansion device <NUM> is opened to the highest opening degree, it becomes impossible to adjust the flow rate of refrigerant bypassed, solely by adjusting the opening degree of the third expansion device <NUM>. Therefore, in Embodiment <NUM>, the flow rate of refrigerant to be bypassed is increased by controlling the first expansion device <NUM> such that the difference between the pressure of refrigerant that has not yet passed through the third expansion device <NUM> and that of refrigerant that has passed through the third expansion device <NUM> is increased.

The controller <NUM> determines whether the temperature detected by the control temperature detector <NUM> is higher than or equal to the temperature threshold, whether the opening degree of the third expansion device <NUM> is higher than or equal to the opening-degree threshold, for example, it is the highest, and whether the degree of superheat detected by the degree-of-superheat detector is smaller or lower than the degree-of-superheat threshold (step S21). When all the above conditions are satisfied (Yes at step S21), a reduction operation of reducing the opening degree of the first expansion device <NUM> from the present opening degree to a certain opening degree is performed (step S22). It should be noted that the degree of superheat is calculated based on the pressure detected by the low-pressure sensor <NUM> and the temperature detected by the suction-side temperature sensor <NUM>. The degree of superheat may be calculated based on the result of detection by another sensor. After that, the same determination control as described above is repeated at regular intervals. The condition for the opening degree of the third expansion device <NUM> is not limited to the condition that the opening degree is the highest and may be the condition that the opening degree is higher than or equal to the opening-degree threshold.

It will be described why the following condition is adopted: the degree of superheat calculated from the results of detection by the suction-side temperature sensor <NUM> and the low-pressure sensor <NUM> is lower than or equal to the degree-of-superheat threshold. The adoption of the above condition is intended to reduce the possibility that the heating capacity will become insufficient due to reduction of the opening degree of the first expansion device <NUM>. Generally, when the opening degree of the first expansion device <NUM> is reduced, the quality of the liquid pipe <NUM> from the load-side unit <NUM> to the first expansion device <NUM> is decreased and the pressure of the liquid pipe <NUM> is increased, whereby the refrigerant density in the liquid pipe <NUM> is increased, and in the system, refrigerant excessively concentratedly flows in the liquid pipe <NUM>.

When in the system, refrigerant excessively concentratedly flows in the liquid pipe <NUM> and the refrigerant that flows through the other pipes becomes insufficient, the heating capacity is reduced. Therefore, as an index for ensuring that the refrigerant flowing through the other pipes is not insufficient, the following condition is applied: the degree of superheat calculated from the results of detection by the suction-side temperature sensor <NUM> and the low-pressure sensor <NUM> is lower than or equal to the degree-of-superheat threshold. When the above condition is satisfied, the opening degree of the first expansion device <NUM> is reduced. It should be noted that when it is expected that refrigerant will not excessively concentratedly flow in the above manner, from the conditions for reducing the opening degree of the first expansion device <NUM>, the condition that the degree of superheat is lower than or equal to the degree-of-superheat threshold may be omitted.

When at least one of the above conditions is not satisfied (No at step S21), the controller <NUM> maintains the present opening degree of the first expansion device <NUM> (step S23). After that, the same determination control as described above are repeated at regular intervals.

By the above refrigerant cooling control, the controller <NUM> is cooled. The specific numerical values of the temperatures in the above description are examples and may be changed as appropriate depending on conditions in actual use or other factors.

According to Embodiment <NUM>, the bypass pipe <NUM>, at which the refrigerant cooler <NUM> configured to cool the controller <NUM> is provided, bypasses the liquid pipe <NUM> between the first expansion device <NUM> and the third expansion device <NUM> and the suction side of the compressor <NUM>. Thus, the refrigerant discharged from the compressor <NUM> flows to the heat-source-side heat exchanger <NUM> or the load-side heat exchanger <NUM> without being bypassed. Therefore, it is possible to avoid a loss in the capacity that would occur if the refrigerant discharged from the compressor <NUM> were bypassed. Accordingly, it is possible to reduce a decrease in the heating and cooling capacity.

In the heating operation, all the refrigerant discharged from the compressor <NUM> contributes to heating of air-conditioning target space. Furthermore, in the heating operation, because the evaporating performance of the refrigerant cooler <NUM> that is obtained from the cooling of the controller <NUM> can be added to the evaporating performance of the heat-source-side heat exchanger <NUM>, the heating capacity can be improved. This is remarkable in the case where the controller <NUM> uses a component that generates a large amount of heat, such as an inverter. In this case, because the amount of heat of the controller <NUM> is large, the refrigerant is correspondingly evaporated by the refrigerant cooler <NUM>.

Furthermore, since the bypass pipe <NUM> is connected to the liquid pipe <NUM>, refrigerant that flows through the bypass pipe <NUM> has already been condensed by the heat-source-side heat exchanger <NUM> or the load-side heat exchanger <NUM>. Therefore, it is not necessary to further provide an additional condenser at the bypass pipe <NUM>. Accordingly, it is not necessary to assign part of the heat-source-side heat exchanger <NUM> as a condenser for the bypass pipe <NUM>. Thus, the entire capacity of the heat-source-side heat exchanger <NUM> can be used in heating and cooling, and the refrigerant circuit can thus be simplified.

The refrigeration cycle apparatus <NUM> further includes the control temperature detector <NUM> that detects the temperature of the controller <NUM> and the opening-degree detector 602a that detects the opening degree of the third expansion device <NUM>. When the temperature detected by the control temperature detector <NUM> is higher than or equal to the temperature threshold, and the opening degree of the third expansion device <NUM> detected by the opening-degree detector 602a is higher than or equal to the opening-degree threshold, the controller <NUM> reduces the opening degree of the first expansion device <NUM>. Thus, even when it becomes hard for the third expansion device <NUM> to adjust the flow rate of the refrigerant that flows through the bypass pipe <NUM>, the first expansion device <NUM> can adjust the flow rate of the refrigerant that flows through the bypass pipe <NUM> in place of the third expansion device <NUM>.

The refrigeration cycle apparatus <NUM> further includes the degree-of-superheat detector that detects the degree of superheat on the suction side of the compressor <NUM>, and in addition, when the degree of superheat detected by the degree-of-superheat detector is equal to or less than the degree-of-superheat threshold, the controller <NUM> decreases the opening degree of the first expansion device <NUM>. By decreasing the opening degree of the first expansion device <NUM> after confirming that the refrigerant flowing through pipes other than the liquid pipe <NUM> is not insufficient, it is possible to reduce the decrease in the heating and cooling capacity.

Moreover, the bypass pipe <NUM> is connected to lower part of the liquid pipe <NUM>. Therefore, liquid refrigerant whose enthalpy is low can be bypassed. Accordingly, even when the difference between the pressure of refrigerant that has not yet passed through the third expansion device <NUM> and that of refrigerant that has passed through the third expansion device <NUM> is small and the flow rate of the refrigerant is low, it is possible to ensure a cooling performance required for cooling the controller <NUM>.

Regarding Embodiment <NUM>, the refrigeration cycle apparatus <NUM> including one heat-source-side unit <NUM> and two load-side units <NUM> is illustrated as an example; however, the number of heat-source-side units <NUM> and that of two load-side units <NUM> are not limited. Furthermore, the above description regarding Embodiment <NUM> refers to the refrigeration cycle apparatus <NUM> in which the operation of each of the load-side units <NUM> can be switched to one of the cooling operation and the heating operation. However, the apparatus to which the above control is applied is not limited to the above refrigeration cycle apparatus. As other apparatuses to which evaporation control is applicable, for example, the following apparatuses are present: the refrigeration cycle apparatus <NUM> in which a load is heated by supply of capacity; and an apparatus including a refrigerant circuit using a refrigeration cycle such as a refrigeration system.

In addition, regarding Embodiment <NUM>, it is described above that the refrigeration cycle apparatus <NUM> is an air-conditioning apparatus, but the refrigeration cycle apparatus <NUM> may be a cooling apparatus that cools a cold storage and refrigerated warehouse or other space.

Claim 1:
A refrigeration cycle apparatus comprising:
a refrigerant circuit in which a compressor (<NUM>), a heat-source-side heat exchanger (<NUM>), a first expansion device (<NUM>), a second expansion device (<NUM>), and a load-side heat exchanger (<NUM>) are sequentially connected by refrigerant pipes and in which refrigerant is circulated;
a controller (<NUM>) configured to control the refrigerant circuit;
a bypass pipe (<NUM>) extending from a liquid pipe (<NUM>) between the first expansion device (<NUM>) and the second expansion device (<NUM>) toward a suction side of the compressor (<NUM>);
a third expansion device (<NUM>) provided at the bypass pipe (<NUM>), and configured to decompress the refrigerant that flows through the bypass pipe (<NUM>); and
a refrigerant cooler (<NUM>) provided at the bypass pipe (<NUM>) and downstream of the third expansion device (<NUM>), and configured to cause heat exchange to be performed between the refrigerant decompressed by the third expansion device (<NUM>) and heat generated from the controller (<NUM>),
characterized in that the refrigeration cycle apparatus further comprises:
a control temperature detector (<NUM>) configured to detect a temperature of the controller (<NUM>); and
an opening-degree detector (602a) configured to detect an opening degree of the third expansion device (<NUM>),
wherein when the temperature detected by the control temperature detector (<NUM>) is higher than or equal to a temperature threshold, and the opening degree of the third expansion device (<NUM>) detected by the opening-degree detector (602a) is higher than or equal to an opening-degree threshold, the controller (<NUM>) decreases an opening degree of the first expansion device (<NUM>).