Refrigeration cycle device, and refrigeration cycle device control method

Abstract

The objective of the present invention is to suppress a decrease in comfort for a user even if a non-azeotropic mixed refrigerant is used and an intermediate heat exchanger is provided, by ensuring a pressure difference of the non-azeotropic mixed refrigerant, in particular during startup of a compressor, to thereby perform operation suited to a required capacity. This refrigeration cycle device comprises a refrigerant circuit (C) in which a compressor (1), a condenser, a pressure reducing mechanism (3) and an evaporator are connected sequentially by means of refrigerant piping, and through which a non-azeotropic mixed refrigerant circulates, an intermediate heat exchanger (6), a bypass circuit (B) provided with a bypass valve (B1) that bypasses the intermediate heat exchanger (6), a condenser outlet temperature sensor (7), an evaporator outlet temperature sensor (8), and a control device (9), wherein the control device (9) comprises: a determining unit (93) which determines whether the condenser outlet temperature is equal to or greater than a prescribed condensation temperature value; and a drive control unit (94) that controls the bypass valve (B1) to be fully open during startup of the compressor (1), and controls the bypass valve (B1) to be fully closed if the determining unit (93) has determined that the condenser outlet temperature is equal to or greater than the prescribed condensation temperature value.

Description

Refrigeration cycle device and control method for refrigeration cycle device

[0001] FIELD An embodiment of the present invention relates to a refrigeration cycle device and a control method for a refrigeration cycle device.

[0002] For example, when a single refrigerant is used in a refrigeration cycle system, the temperature of the refrigerant remains constant in the condenser and evaporator as long as the refrigerant is in a two-phase state and the pressure is constant. In contrast, when a non-azeotropic refrigerant mixture is used as the refrigerant, the evaporation and condensation temperatures of the refrigerant change even in the two-phase region during the evaporation and condensation process at constant pressure, unlike when using a single refrigerant. A so-called temperature gradient (the difference between the temperature of the saturated liquid and the temperature of the saturated vapor) occurs. As a result, the temperature of the refrigerant downstream of the condenser may be lower than that upstream.

[0003] When a non-azeotropic refrigerant mixture has a large temperature gradient, the temperature difference between the air and the refrigerant that exchanges heat in the refrigerant flow path at the outlet of the condenser or evaporator becomes smaller than when a single refrigerant is used. As a result, the amount of heat exchange in the air conditioner decreases, which reduces the degree of subcooling during the condensation process and the degree of suction superheat during the evaporation process, making it difficult to maintain the degree of subcooling or suction superheat. This can lead to a decrease in the operating efficiency of the air conditioner.

[0004] For this reason, the invention disclosed in the following Patent Document 1 provides an intermediate heat exchanger. In this intermediate heat exchanger, heat is exchanged between the refrigerant on the condenser outlet side (refrigerant after passing through the condenser) and the refrigerant on the evaporator outlet side (refrigerant after passing through the evaporator). By performing such heat exchange, a greater enthalpy difference can be ensured, thereby ensuring the degree of subcooling and suction superheat, and preventing a decrease in COP.

[0005] Japanese Patent Application Publication No. 08-075290

[0006] When the compressor of the refrigeration cycle device starts, the pressure in the refrigerant circuit is uniform, so there is no pressure difference between the discharge side and the suction side of the compressor. When the compressor starts from this state, a pressure difference occurs, and the refrigerant gradually reaches the required condensation temperature or evaporation temperature.

[0007] On the other hand, a refrigeration cycle apparatus using a non-azeotropic refrigerant mixture needs to be provided with the intermediate heat exchanger. In this case, the pressure difference in the intermediate heat exchanger causes more active heat exchange between the high-pressure non-azeotropic refrigerant mixture and the low-pressure non-azeotropic refrigerant mixture. This creates a situation in which the non-azeotropic refrigerant mixture is prone to condensation or evaporation, making it difficult for the high-pressure pressure of the non-azeotropic refrigerant mixture in the refrigerant circuit to increase and the low-pressure pressure to decrease.

[0008] In particular, the refrigerant circuit disclosed in Patent Document 1 is designed such that heat exchange occurs between the high-pressure non-azeotropic refrigerant and the low-pressure non-azeotropic refrigerant while the refrigeration cycle device is in operation. This makes it difficult to maintain a pressure difference between the high-pressure and low-pressure non-azeotropic refrigerant in the refrigerant circuit during operation. This makes it difficult for the refrigeration cycle device to reach the required condensing and evaporating temperatures, preventing operation at the required capacity and reducing comfort.

[0009] An object of the present invention is to provide a refrigeration cycle device and a control method for a refrigeration cycle device that can suppress a decrease in user comfort by ensuring a pressure difference of the non-azeotropic refrigerant, particularly when starting up the compressor, and operating in accordance with the required capacity, even when an intermediate heat exchanger is provided using the non-azeotropic refrigerant.

[0010] A refrigeration cycle device according to one aspect of the present invention includes a refrigerant circuit in which a compressor, a condenser, a pressure reducing mechanism, and an evaporator are sequentially connected by refrigerant piping, and in which a non-azeotropic refrigerant circulates; an intermediate heat exchanger in which heat is exchanged between the non-azeotropic refrigerant flowing between the condenser and the pressure reducing mechanism and the non-azeotropic refrigerant flowing between the evaporator and the compressor; a bypass circuit in a path between the condenser and the pressure reducing mechanism that bypasses the intermediate heat exchanger; a bypass valve provided in the bypass circuit; a condenser outlet temperature sensor that detects the temperature of the non-azeotropic refrigerant flowing downstream of the condenser; and an evaporator outlet temperature sensor that detects the temperature of the non-azeotropic refrigerant flowing downstream of the evaporator. The control device includes a control device that controls the compressor, the pressure reducing mechanism, and the bypass valve. The control device includes a determination unit that determines whether the condenser outlet temperature detected by the condenser outlet temperature sensor is equal to or higher than a predetermined condensing temperature value, or whether the evaporator outlet temperature detected by the evaporator outlet temperature sensor is equal to or higher than a predetermined evaporating temperature value, and a drive control unit that controls the bypass valve to be fully open when the compressor is started, and controls the bypass valve to be fully closed when the determination unit determines that the condenser outlet temperature is equal to or higher than the predetermined condensing temperature value, or when the determination unit determines that the evaporator outlet temperature is equal to or higher than the predetermined evaporating temperature value.

[0011] A refrigeration cycle device according to one aspect of the present invention includes a refrigerant circuit in which a compressor, a condenser, a pressure reducing mechanism, and an evaporator are sequentially connected by refrigerant piping, and in which a non-azeotropic refrigerant circulates; an intermediate heat exchanger in which heat is exchanged between the non-azeotropic refrigerant flowing between the condenser and the pressure reducing mechanism and the non-azeotropic refrigerant flowing between the evaporator and the compressor; a bypass circuit in a path between the condenser and the pressure reducing mechanism that bypasses the intermediate heat exchanger; a bypass valve provided in the bypass circuit; a condenser outlet temperature sensor that detects the temperature of the non-azeotropic refrigerant flowing downstream of the condenser; The control device includes an evaporator outlet temperature sensor that detects the temperature of the non-azeotropic refrigerant mixture, a compressor, a pressure reducing mechanism, and a control device that controls a bypass valve. The control device includes a determination unit that determines whether the temperature difference between the condenser outlet temperature detected by the condenser outlet temperature sensor and the evaporator outlet temperature detected by the evaporator outlet temperature sensor is equal to or greater than a predetermined temperature difference value that is set in advance, and a drive control unit that controls the bypass valve to be fully open when the compressor is started, and controls the bypass valve to be fully closed when the determination unit determines that the temperature difference is equal to or greater than the predetermined temperature difference value.

[0012] A method for controlling a refrigeration cycle apparatus according to one aspect of the present invention includes a refrigerant circuit in which a compressor, a condenser, a pressure reducing mechanism, and an evaporator are sequentially connected by a refrigerant pipe and in which a non-azeotropic refrigerant mixture circulates, an intermediate heat exchanger in which heat exchange occurs between the non-azeotropic refrigerant mixture flowing between the condenser and the pressure reducing mechanism and the non-azeotropic refrigerant mixture flowing between the evaporator and the compressor, a bypass circuit in a path between the condenser and the pressure reducing mechanism that bypasses the intermediate heat exchanger, a bypass valve provided in the bypass circuit, a condenser outlet temperature sensor that detects the temperature of the non-azeotropic refrigerant mixture flowing downstream of the condenser, an evaporator outlet temperature sensor that detects the temperature of the non-azeotropic refrigerant mixture flowing downstream of the evaporator, and a compressor. and a control device that controls the compressor, the pressure reducing mechanism, and the bypass valve, and includes the steps of controlling the bypass valve to be fully open when the compressor is started, acquiring the condenser outlet temperature from a condenser outlet temperature sensor, or acquiring the evaporator outlet temperature from an evaporator outlet temperature sensor, determining whether the condenser outlet temperature is equal to or higher than a predetermined condensing temperature value, or determining whether the evaporator outlet temperature is equal to or higher than a predetermined evaporating temperature value, and controlling the bypass valve to be fully closed when the condenser outlet temperature is equal to or higher than the predetermined condensing temperature value, or when the evaporator outlet temperature and the evaporator outlet temperature are equal to or higher than the predetermined evaporating temperature value, as a result of the comparison.

[0013] A method for controlling a refrigeration cycle apparatus according to one aspect of the present invention includes a refrigerant circuit in which a compressor, a condenser, a pressure reducing mechanism, and an evaporator are sequentially connected by refrigerant piping and in which a non-azeotropic refrigerant mixture circulates, an intermediate heat exchanger in which heat is exchanged between the non-azeotropic refrigerant mixture flowing between the condenser and the pressure reducing mechanism and the non-azeotropic refrigerant mixture flowing between the evaporator and the compressor, a bypass circuit in a path between the condenser and the pressure reducing mechanism that bypasses the intermediate heat exchanger, a bypass valve provided in the bypass circuit, a condenser outlet temperature sensor that detects the temperature of the non-azeotropic refrigerant mixture flowing downstream of the condenser, and a refrigerant circuit in which heat is exchanged between the non-azeotropic refrigerant mixture flowing downstream of the evaporator. The system includes an evaporator outlet temperature sensor that detects the temperature of the refrigerant, a compressor, a pressure reducing mechanism, and a control device that controls a bypass valve, and includes the steps of controlling the bypass valve to be fully open when the compressor is started, acquiring the condenser outlet temperature from the condenser outlet temperature sensor and the evaporator outlet temperature from the evaporator outlet temperature sensor, calculating the temperature difference between the condenser outlet temperature and the evaporator outlet temperature, determining whether the temperature difference is equal to or greater than a predetermined temperature difference value, and controlling the bypass valve to be fully closed when the temperature difference is equal to or greater than the predetermined temperature difference value.

[0014] According to the present invention, even when a non-azeotropic refrigerant mixture is used and an intermediate heat exchanger is provided, a pressure difference of the non-azeotropic refrigerant mixture is ensured, particularly at the start of the compressor, and operation is performed in accordance with the required capacity, thereby suppressing a decrease in comfort for the user.

[0015] 1 is a refrigerant circuit diagram of a refrigeration cycle device according to an embodiment of the present invention; 2 is a block diagram showing the internal configuration of a control device in a refrigeration cycle device according to an embodiment of the present invention; 3 is a flowchart showing a basic control flow of a refrigeration cycle device according to an embodiment of the present invention; 4 is a flowchart showing another aspect of the control flow of a refrigeration cycle device according to an embodiment of the present invention; 5 is a flowchart illustrating the relationship between the control of an indoor fan provided in an indoor heat exchanger functioning as a condenser, in particular, in the control flow of a refrigeration cycle device according to an embodiment of the present invention; 6 is a flowchart showing a flow when a temperature difference between a condenser outlet temperature and an evaporator outlet temperature is used in the control flow of a refrigeration cycle device according to an embodiment of the present invention;

[0016] The structure of a refrigeration cycle apparatus S according to an embodiment of the present invention will be described with reference to Fig. 1. Fig. 1 is a refrigerant circuit diagram of the refrigeration cycle apparatus S according to the embodiment of the present invention. The refrigeration cycle apparatus S according to the embodiment of the present invention shown in Fig. 1 has a refrigerant circuit C in which a compressor 1, an outdoor heat exchanger 2, a pressure reducing mechanism 3, and an indoor heat exchanger 4 are connected in sequence by refrigerant piping, and in which a non-azeotropic refrigerant mixture circulates as the refrigerant.

[0017] As described above, the refrigerant circulating through the refrigerant circuit C of the refrigeration cycle apparatus S in this embodiment of the present invention is a non-azeotropic refrigerant mixture. A non-azeotropic refrigerant mixture has a property in which the temperature changes (temperature gradient) even in a two-phase state during the isobaric condensation or evaporation process. An example of such a non-azeotropic refrigerant mixture is R454C (a mixture of R32 refrigerant and R1234yf refrigerant). In the following description, such a non-azeotropic refrigerant mixture will also be referred to as the "refrigerant" where appropriate.

[0018] The compressor 1 draws in the refrigerant that has circulated through the refrigerant circuit C, compresses it, and discharges it into the refrigerant circuit C. The outdoor heat exchanger 2 is disposed inside an outdoor unit that is installed outdoors. The outdoor heat exchanger 2 exchanges heat between the refrigerant flowing therethrough and the outside air.

[0019] For example, in the case of heating operation described later, heat is exchanged between the refrigerant and the air (outdoor air) flowing into the outdoor unit in the outdoor heat exchanger 2, and heat of the outdoor air is absorbed by the refrigerant. Therefore, in the case of heating operation, the outdoor heat exchanger 2 functions as an evaporator.

[0020] The outdoor unit is provided with an outdoor fan 21. The outdoor fan 21 takes in outside air into the outdoor unit, and discharges the air that has exchanged heat with the refrigerant to the outside.

[0021] In the refrigerant circuit C, a pressure reducing mechanism 3 is provided between the outdoor heat exchanger 2 and an indoor heat exchanger 4 (described later), downstream of an intermediate heat exchanger 6 (described later). The pressure reducing mechanism 3 is, for example, an expansion valve, and reduces the pressure of the high-pressure refrigerant that has passed through the outdoor heat exchanger 2 or the indoor heat exchanger 4.

[0022] In the refrigeration cycle apparatus S according to the embodiment of the present invention, two pressure reduction mechanisms (a first pressure reduction mechanism 31 and a second pressure reduction mechanism 32) are provided in the refrigerant circuit C as the pressure reduction mechanism 3. This is to allow high-pressure refrigerant to flow into the intermediate heat exchanger 6 regardless of whether the refrigerant is in cooling operation or heating operation.

[0023] That is, when the cooling operation is performed, the outdoor heat exchanger 2 functions as a condenser, and therefore, in the case of the refrigeration cycle apparatus S shown in Fig. 1 , the pressure reduction mechanism 3 is disposed downstream of the intermediate heat exchanger 6 and between the outdoor heat exchanger 2 and the indoor heat exchanger 4. That is, during the cooling operation, the first pressure reduction mechanism 31 functions as the pressure reduction mechanism 3. At this time, the opening degree of the second pressure reduction mechanism 32 is controlled so that it is fully open.

[0024] On the other hand, when the heating operation is performed, the indoor heat exchanger 4 functions as a condenser, and therefore, in the case of the refrigeration cycle apparatus S shown in Fig. 1 , the pressure reduction mechanism 3 is disposed downstream of the intermediate heat exchanger 6 and between the outdoor heat exchanger 2. In other words, during the heating operation, the second pressure reduction mechanism 32 functions as the pressure reduction mechanism 3. At this time, the opening degree of the first pressure reduction mechanism 31 is controlled so as to be fully open.

[0025] In the following description, when there is no need to particularly distinguish between the first pressure reduction mechanism 31 and the second pressure reduction mechanism 32, they will be simply referred to as the "pressure reduction mechanism 3" as described above.

[0026] The indoor heat exchanger 4 is disposed inside the indoor unit installed in the indoor space. For example, in heating operation, the indoor heat exchanger 4 exchanges heat between the refrigerant and the indoor air flowing into the indoor unit, and supplies heated air to the indoor space by absorbing heat from the refrigerant. Therefore, in heating operation, the indoor heat exchanger 4 functions as a condenser.

[0027] An indoor fan 41 is provided inside the indoor unit. The indoor fan 41 takes air into the indoor unit and supplies the air that has exchanged heat with the refrigerant into the room.

[0028] A four-way valve 5 is provided between the compressor 1 and the indoor heat exchanger 4, or between the compressor 1 and the outdoor heat exchanger 2. The four-way valve 5 switches whether the refrigerant discharged from the compressor flows to the outdoor heat exchanger 2 side or the indoor heat exchanger 4 side.

[0029] 1 , in a refrigeration cycle apparatus S according to an embodiment of the present invention, an intermediate heat exchanger 6 is provided between the outdoor heat exchanger 2 and the indoor heat exchanger 4. The intermediate heat exchanger 6 includes a high-pressure side flow path through which refrigerant flows between the outdoor heat exchanger 2 and the indoor heat exchanger 4, and a low-pressure side flow path through which refrigerant flows between the four-way valve 5 and the compressor 1. That is, in the intermediate heat exchanger 6, heat is exchanged between the non-azeotropic refrigerant flowing between the condenser and the pressure reducing mechanism and the non-azeotropic refrigerant flowing between the evaporator and the compressor.

[0030] As described above, the refrigerant used in the refrigeration cycle apparatus S in the embodiment of the present invention is a non-azeotropic refrigerant mixture, which exhibits a temperature gradient in the two-phase region during the evaporation / condensation processes at equal pressures. With a refrigerant that exhibits a temperature gradient, the temperature difference between the refrigerant and the air gradually decreases during the evaporation and condensation processes, making it difficult to ensure an enthalpy difference and therefore difficult to ensure the degree of subcooling and suction superheat required from the perspective of performance and reliability of the refrigeration cycle apparatus S. Therefore, in order to ensure an enthalpy difference and the degree of subcooling and suction superheat, an intermediate heat exchanger 6 is provided to exchange heat between the refrigerant that has passed through the condenser and the refrigerant that has passed through the evaporator.

[0031] Furthermore, in the refrigeration cycle apparatus S according to the embodiment of the present invention, a bypass circuit B that bypasses the intermediate heat exchanger 6 is provided in the path between the condenser and the pressure reduction mechanism 3. That is, when the outdoor heat exchanger 2 serves as the condenser, the bypass circuit B is provided between the outdoor heat exchanger 2 and the first pressure reduction mechanism 31 that functions as the pressure reduction mechanism 3. On the other hand, when the indoor heat exchanger 4 serves as the condenser, the bypass circuit B is provided between the indoor heat exchanger 4 and the second pressure reduction mechanism 32 that functions as the pressure reduction mechanism 3.

[0032] A bypass valve B1 is provided in the bypass circuit B. The bypass valve B1 is driven to be fully open or fully closed under the control of a control device 9, which will be described later. Therefore, when the bypass valve B1 is fully open, most of the refrigerant flowing out from the condenser flows into the bypass circuit B, and when the bypass valve B1 is fully closed, the refrigerant flows into the intermediate heat exchanger 6.

[0033] Therefore, the bypass valve B1 may be an on-off valve provided in the bypass circuit B as shown in FIG. 1 , or any type of valve, such as a three-way valve, that can switch the flow path of the refrigerant flowing out of the condenser to the bypass circuit B or the intermediate heat exchanger 6.

[0034] The bypass circuit B is provided to prevent the operation from failing to meet the required capacity due to a large amount of refrigerant flowing out of the condenser (the outdoor heat exchanger 2 or the indoor heat exchanger 4) flowing into the intermediate heat exchanger 6. Therefore, when the bypass valve B1 provided in the bypass circuit B is open (fully open), most of the refrigerant flowing out of the condenser passes through the bypass circuit B and flows to the evaporator, making it possible to reduce the amount of refrigerant flowing into the intermediate heat exchanger 6.

[0035] On the other hand, when the bypass valve B1 is closed (fully closed), the refrigerant that has flowed out of the condenser does not flow into the bypass circuit B, and instead flows into the evaporator via the intermediate heat exchanger 6.

[0036] Furthermore, the refrigerant circuit C of the refrigeration cycle apparatus S according to the embodiment of the present invention is provided with a plurality of temperature sensors. One of them is a condenser outlet temperature sensor 7 that detects the temperature of the refrigerant flowing out from the condenser.

[0037] Here, in the cooling operation, the outdoor heat exchanger 2 functions as a condenser, and therefore a first condenser outlet temperature sensor 71 is provided between the outdoor heat exchanger 2 and the intermediate heat exchanger 6. On the other hand, in the heating operation, the indoor heat exchanger 4 functions as a condenser, and therefore a second condenser outlet temperature sensor 72 is provided between the indoor heat exchanger 4 and the intermediate heat exchanger 6.

[0038] In this way, the first condenser outlet temperature sensor 71 and the second condenser outlet temperature sensor 72 are provided downstream of the condenser. When it is not necessary to distinguish between the first condenser outlet temperature sensor 71 and the second condenser outlet temperature sensor 72, they will be referred to as the "condenser outlet temperature sensor 7" as appropriate.

[0039] Furthermore, an evaporator outlet temperature sensor 8 is provided downstream of the evaporator to detect the temperature of the refrigerant flowing out from the evaporator. As shown in the refrigerant circuit C in Fig. 1 , the evaporator outlet temperature sensor 8 is provided between the four-way valve 5 and the intermediate heat exchanger 6. Due to the configuration of the refrigerant circuit C, whether the evaporator is the outdoor heat exchanger 2 or the indoor heat exchanger 4, the refrigerant that has flowed out of the evaporator flows into the intermediate heat exchanger 6 via the four-way valve 5. Therefore, unlike the condenser outlet temperature sensor 7, the evaporator outlet temperature sensor 8 is provided in only one location, as described above.

[0040] The control device 9 is provided in the refrigeration cycle apparatus S and controls the pressure reducing mechanism 3 and the bypass valve B1. The control device 9 also controls the rotation speeds of the compressor 1, the outdoor fan 21, and the indoor fan 41. The control device 9 controls each part of the refrigeration cycle apparatus S based on the control content described below, thereby ensuring a pressure difference of the non-azeotropic refrigerant mixture, particularly when the compressor is started, and operating in accordance with the required capacity, thereby suppressing a decrease in comfort for the user.

[0041] In particular, for example, by controlling the opening degree of the bypass valve B1, the control device 9 can cause the refrigerant flowing through the refrigerant circuit C to flow into the intermediate heat exchanger 6, or cause most of the refrigerant to flow into the bypass circuit B. Note that in the following embodiments of the present invention, with regard to the control device 9, only the functions necessary for ensuring a pressure difference of the non-azeotropic refrigerant mixture at the start of the compressor 1 and performing operation that meets the required capacity will be described.

[0042] 2 is a block diagram showing the internal configuration of the control device 9 in the refrigeration cycle apparatus S according to the embodiment of the present invention. The control device 9 includes a temperature detection unit 91, a storage unit 92, a determination unit 93, and a drive control unit 94.

[0043] The control device 9 may have a configuration in which, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and an input / output interface are connected via a bus, which are not shown in Fig. 2. Furthermore, the input / output interface may be connected to the above-mentioned components as well as components such as a display unit, a communication control unit, or an input unit.

[0044] The temperature detection unit 91 acquires information on the refrigerant temperatures detected by the first condenser outlet temperature sensor 71, the second condenser outlet temperature sensor 72, and the evaporator outlet temperature sensor 8 described above.

[0045] The storage unit 92 stores various predetermined values ​​to be compared with the refrigerant temperature acquired by the temperature detection unit 91, which is used to control the opening and closing of the bypass valve B1. For example, information related to the refrigerant temperature acquired by the temperature detection unit 91 may also be stored. Furthermore, a determination program and the like used by the determination unit 93, which will be described later, when making a determination is also stored.

[0046] The determination unit 93 uses the condenser outlet temperature or the evaporator outlet temperature detected by the condenser outlet temperature sensor 7 or the evaporator outlet temperature sensor 8 described above to determine whether to cause the refrigerant to flow through the bypass circuit B or the intermediate heat exchanger 6. The timing of the determination may be set based on, for example, a predetermined time interval, and the predetermined time interval is stored in, for example, the storage unit 92.

[0047] Specifically, the judgment unit 93 compares the condenser outlet temperature detected by the condenser outlet temperature sensor 7 with a predetermined condensation temperature value set in advance, and judges whether the condenser outlet temperature is equal to or higher than the predetermined condensation temperature value.

[0048] Alternatively, the judgment unit 93 compares the evaporator outlet temperature detected by the evaporator outlet temperature sensor 8 with a predetermined evaporation temperature value set in advance, and judges whether the evaporator outlet temperature is below the predetermined evaporation temperature value.

[0049] Alternatively, the judgment unit 93 calculates the temperature difference between the condenser outlet temperature detected by the condenser outlet temperature sensor 7 and the evaporator outlet temperature detected by the evaporator outlet temperature sensor 8, and judges whether the calculated temperature difference is greater than or equal to a predetermined temperature difference value that has been set in advance.

[0050] In this way, the determination unit 93 performs the determination using any one or more of the above-described multiple conditions when determining whether to flow the refrigerant through the bypass circuit B or through the intermediate heat exchanger 6. Which of these multiple conditions to use is set in advance, and the determination process is performed at each of the above-described preset timings.

[0051] The drive control unit 94 controls, for example, the opening degree of the pressure reducing mechanism 3 or the opening and closing of the bypass valve B1 based on the determination result of the determination unit 93. In addition, the drive control unit 94 also controls the rotation speed of the compressor 1 and the rotation speeds of the outdoor fan 21 and the indoor fan 41.

[0052] In this way, the drive control unit 94 controls the drive of each unit. Regarding the control of the opening degree of the bypass valve B1, when the compressor 1 is started, the drive control unit 94 controls the opening degree of the bypass valve B1 so that the bypass valve B1 is fully opened.

[0053] As described above, when the compressor 1 of the refrigeration cycle apparatus S starts, the pressure in the refrigerant circuit C is equal and there is no pressure difference between the discharge side and the suction side of the compressor. Therefore, in order to operate the compressor in a state where the condensing temperature or evaporation temperature that matches the required capacity is reached as quickly as possible and to prevent a decrease in user comfort, it is necessary to ensure a refrigerant pressure difference as quickly as possible.

[0054] However, as explained above, the refrigeration cycle apparatus S in the embodiment of the present invention is provided with an intermediate heat exchanger 6, and this intermediate heat exchanger 6 is configured to exchange heat between the non-azeotropic refrigerant on the high-pressure side and the non-azeotropic refrigerant on the low-pressure side.

[0055] Therefore, if the refrigerant flows into the intermediate heat exchanger 6 when a pressure difference of the non-azeotropic refrigerant mixture must be ensured, particularly at the start of the compressor 1, heat exchange occurs in the intermediate heat exchanger 6, making it difficult to ensure a pressure difference of the non-azeotropic refrigerant mixture in the refrigerant circuit C.

[0056] Therefore, in the refrigeration cycle apparatus S according to the embodiment of the present invention, when the compressor 1 is started, the control device 9 (drive control unit 94) controls the opening of the bypass valve B1 to be fully open, thereby preventing a large amount of refrigerant from flowing into the intermediate heat exchanger 6.

[0057] That is, when the bypass valve B1 is fully opened due to the difference in piping length and the pressure loss inside the intermediate heat exchanger 6, most of the refrigerant discharged from the compressor 1 and flowing out of the condenser at the start of the compressor 1 flows into the bypass circuit B, and some of the refrigerant flows into the intermediate heat exchanger 6. In this way, even when the bypass valve B1 is fully opened, it does not mean that no refrigerant flows into the intermediate heat exchanger 6, but when the bypass valve B1 is fully opened, most of the refrigerant flows into the bypass circuit B, and it is possible to reduce the refrigerant flowing into the intermediate heat exchanger 6. In other words, it is possible to prevent the refrigerant from flowing into the intermediate heat exchanger 6.

[0058] In this way, the determination unit 93 determines whether to flow the refrigerant into the bypass circuit B or into the intermediate heat exchanger 6 by comparing the condenser outlet temperature with a predetermined condensation temperature value, the evaporator outlet temperature with a predetermined evaporation temperature value, or the temperature difference between the condenser outlet temperature and the evaporator outlet temperature with a predetermined temperature difference value.

[0059] Therefore, even if the refrigerant flows into the intermediate heat exchanger 6, a pressure difference between the high-pressure side refrigerant and the low-pressure side refrigerant must be ensured to a degree that allows sufficient heat exchange in the intermediate heat exchanger 6, which can be considered to be a condition for switching from a state in which the refrigerant flows through the bypass circuit B to a state in which the refrigerant flows through the intermediate heat exchanger 6.

[0060] From this perspective, the "predetermined condensing temperature value," the "predetermined evaporation temperature value," and the "predetermined temperature difference value" can all be said to be temperatures at which the pressure difference between the high-pressure refrigerant and the low-pressure refrigerant is sufficient and the intermediate heat exchanger 6 can function effectively. These predetermined values ​​are determined in advance by experiments or the like from the above perspective, and are stored in the storage unit 92.

[0061] There is a slight time lag between the timing at which the pressure difference between the discharge side and the suction side, which is zero (or small) at the start of the compressor 1, becomes a value sufficient to obtain the required capacity even if the intermediate heat exchanger 6 is operated, and the timing at which the intermediate heat exchanger starts to function effectively. Therefore, even if, for example, a predetermined condensing temperature value or the like is set and refrigerant is caused to flow into the intermediate heat exchanger 6 at the former timing, it is unlikely that effective heat exchange will actually be performed in the intermediate heat exchanger 6. Therefore, the predetermined condensing temperature value or the like is set to a temperature at which the intermediate heat exchanger 6 functions effectively, as described above.

[0062] However, particularly when the refrigeration cycle apparatus S performs heating operation, the determination unit 93 makes a determination taking the following condition into consideration: In other words, the determination unit 93 performs the above-described comparison process, and further performs a comparison process to determine whether the condenser outlet temperature is equal to or higher than a preset threshold value.

[0063] When the heating operation is performed in this manner, the determination unit 93 adds a further condition when determining whether to cause the refrigerant to flow through the bypass circuit B or through the intermediate heat exchanger 6 as described above, for the following reason.

[0064] When the refrigerant switches from flowing through the bypass circuit B to flowing through the intermediate heat exchanger 6, heat is exchanged between the refrigerant that has flowed out of the condenser (indoor heat exchanger 4) and the refrigerant that has flowed out of the evaporator (outdoor heat exchanger 2) in the intermediate heat exchanger 6. Therefore, when the intermediate heat exchanger 6 functions, the intermediate heat exchanger 6 also serves as a condenser, and the condensation temperature drops, albeit temporarily.

[0065] A drop in the condensing temperature will result in a drop in the temperature of the air supplied from the indoor heat exchanger 4 to the room. Particularly in the case of heating operation, the operation will not match the required capacity, causing the user to feel cold air, resulting in a decrease in comfort. Therefore, to prevent such a decrease in comfort, the determination unit 93 determines whether the condenser outlet temperature has risen sufficiently, i.e., whether the condenser outlet temperature is equal to or higher than a threshold value.

[0066] When the determination unit 93 determines that the condenser outlet temperature is equal to or higher than the threshold value, the condenser outlet temperature has risen sufficiently. Therefore, by fully closing the bypass valve B1 and switching the refrigerant from flowing through the bypass circuit B to flow through the intermediate heat exchanger 6, it is possible to avoid giving the user a feeling of cold air even when heat exchange is performed in the intermediate heat exchanger 6, and to prevent a decrease in comfort.

[0067] Note that the condenser outlet temperature at which user comfort decreases varies depending on the performance of each device, such as the indoor heat exchanger 4 and the intermediate heat exchanger 6, that constitute the refrigeration cycle apparatus S. Therefore, the threshold value is a value obtained by experiment, etc. The temperature indicated by the threshold value here is set to be at least higher than the predetermined condensation temperature.

[0068] As described above, the determination unit 93 executes the process of comparing the condenser outlet temperature with the threshold value when the refrigeration cycle apparatus S performs heating operation. The above-described effect also occurs when the refrigeration cycle apparatus S performs cooling operation, but in the case of cooling operation, the air supplied from the indoor heat exchanger 4 to the room is cold air to begin with, and therefore the impact of reducing user comfort is smaller than when the heating operation is performed.

[0069] Furthermore, when heating operation is performed in the refrigeration cycle device S, if the above-mentioned judgment unit 93 judges whether the condenser outlet temperature has reached or exceeded the threshold value and determines that the condenser outlet temperature is lower than the threshold value, the drive control unit 94 performs control to prohibit an increase in the rotation speed of the indoor fan 41.

[0070] This is because, in such a case, increasing the rotation speed of the indoor fan 41 increases the amount of heat exchanged between the refrigerant and the indoor air in the indoor heat exchanger 4, which reduces the condensation temperature and may result in a decrease in comfort.

[0071] Therefore, during heating operation, the judgment unit 93 judges that the condenser outlet temperature is equal to or higher than the threshold value, and the drive control unit 94 controls the bypass valve B1 to be fully closed, so that the rotation speed of the indoor fan 41 does not increase until the refrigerant changes from flowing through the bypass circuit B to flowing through the intermediate heat exchanger 6.

[0072] The drive control unit 94 controls the drive of the indoor fan 41 in accordance with the current rotation speed of the indoor fan 41 or a predetermined rotation speed stored in the storage unit 92 until the determination unit 93 determines that the refrigerant can flow from the bypass circuit B into the intermediate heat exchanger 6. Note that the predetermined rotation speed of the indoor fan 41 here is a value determined by an experiment or the like, and is stored in advance in the storage unit 92.

[0073] Here, the flow of the refrigerant in the refrigerant circuit C when the refrigeration cycle apparatus S performs heating operation is as follows: The direction of the refrigerant flow when the heating operation is performed is indicated by solid arrows in FIG.

[0074] The high-temperature, high-pressure gas refrigerant discharged from the compressor 1 flows into the indoor heat exchanger 4 via the four-way valve 5. The indoor heat exchanger 4 draws in indoor air and exchanges heat with the non-azeotropic refrigerant mixture, supplying the warmed air into the room. The high-temperature, high-pressure gas refrigerant releases heat as it passes through the indoor heat exchanger 4, becoming a high-pressure liquid refrigerant.

[0075] The high-pressure liquid refrigerant flowing out from the indoor heat exchanger 4 passes through the fully open first pressure reducing mechanism 31. Thereafter, when the compressor 1 is started, the bypass valve B1 of the bypass circuit B is fully opened, so most of the refrigerant flows into the bypass circuit B without flowing into the intermediate heat exchanger 6.

[0076] The refrigerant flowing into the bypass circuit B is a high-pressure liquid refrigerant, which flows out of the bypass circuit B and into the second pressure reducing mechanism 32. The high-pressure liquid refrigerant is reduced in pressure as it passes through the second pressure reducing mechanism 32, becoming a low-pressure two-phase refrigerant. The low-pressure two-phase refrigerant flowing out of the second pressure reducing mechanism 32 flows into the outdoor heat exchanger 2. At this time, the opening degree of the second pressure reducing mechanism 32 is controlled, for example, by target discharge temperature control. Note that the target discharge temperature control is control of the opening degree of the pressure reducing mechanism 3 to adjust the refrigerant flow rate so that the discharge temperature of the compressor 1 becomes the target discharge temperature.

[0077] In the outdoor heat exchanger 2, heat exchange occurs between the outdoor air and the low-pressure two-phase refrigerant, causing it to absorb heat and become a low-pressure gas refrigerant, which then passes through the four-way valve 5 and flows into the intermediate heat exchanger 6. However, here, the refrigerant that flows out of the indoor heat exchanger 4 does not basically flow into the intermediate heat exchanger 6 and is not subjected to heat exchange in the intermediate heat exchanger 6. The refrigerant that flows out of the intermediate heat exchanger 6 is then drawn into the compressor 1.

[0078] On the other hand, when the determination unit 93 determines that the condenser outlet temperature is equal to or higher than the predetermined condensing temperature value and further equal to or higher than the threshold value, that is, during stable operation, the bypass valve B1 of the bypass circuit B is controlled by the drive control unit 94 to change from fully open to fully closed. As a result, the refrigerant flowing out of the indoor heat exchanger 4 does not flow into the bypass circuit B but flows into the intermediate heat exchanger 6.

[0079] In the intermediate heat exchanger 6, heat is exchanged between the condensed high-pressure liquid refrigerant or two-phase refrigerant flowing in from the indoor heat exchanger 4 and the low-pressure gas refrigerant or two-phase refrigerant flowing out from the outdoor heat exchanger 2. The high-pressure liquid refrigerant or two-phase refrigerant flowing out from the intermediate heat exchanger 6 becomes a two-phase refrigerant via the second pressure reducing mechanism 32 and then flows into the outdoor heat exchanger 2. On the other hand, the gas refrigerant or two-phase refrigerant flowing into the intermediate heat exchanger 6 from the outdoor heat exchanger 2 undergoes heat exchange in the intermediate heat exchanger 6 to become a superheated gas refrigerant, and is then drawn into the compressor 1.

[0080] On the other hand, when the refrigeration cycle apparatus S performs a cooling operation, the flow of the refrigerant in the refrigerant circuit C is as follows: The direction of the refrigerant flow when the cooling operation is performed is indicated by the dashed arrow in FIG.

[0081] When cooling operation is performed, the high-temperature, high-pressure gas refrigerant discharged from the compressor 1 flows into the outdoor heat exchanger 2 via the four-way valve 5. The refrigerant that has flowed into the outdoor heat exchanger 2 exchanges heat with the outside air, dissipating heat and becoming a high-pressure liquid refrigerant.

[0082] Here, the high-pressure liquid refrigerant flowing out from the outdoor heat exchanger 2 passes through the fully open second pressure reduction mechanism 32. Thereafter, when the compressor 1 is started, the bypass valve B1 of the bypass circuit B is fully open, and therefore most of the refrigerant does not flow into the intermediate heat exchanger 6, but flows into the first pressure reduction mechanism 31 through the bypass circuit B. The refrigerant that has flowed into the first pressure reduction mechanism 31 is reduced in pressure to become a low-pressure two-phase refrigerant.

[0083] The refrigerant then flows into the indoor heat exchanger 4, and exchanges heat with the indoor air as it passes through the indoor heat exchanger 4, causing the low-pressure two-phase refrigerant to absorb heat and become gaseous refrigerant. The cooled air is then supplied to the room. The gaseous refrigerant that flows out of the indoor heat exchanger 4 passes through the four-way valve 5 and the intermediate heat exchanger 6 and is drawn into the compressor 1.

[0084] On the other hand, when the determination unit 93 determines that the condenser outlet temperature of the refrigerant flowing out from the outdoor heat exchanger 2 has become equal to or higher than the predetermined condensing temperature value, that is, in a stable state, the bypass valve B1 of the bypass circuit B is controlled by the drive control unit 94 to change from fully open to fully closed. As a result, the refrigerant flowing out from the outdoor heat exchanger 2 flows into the intermediate heat exchanger 6 without flowing into the bypass circuit B.

[0085] In the intermediate heat exchanger 6, heat exchange occurs between the high-pressure liquid refrigerant or two-phase refrigerant flowing out from the outdoor heat exchanger 2 and the low-pressure gas refrigerant or two-phase refrigerant flowing out from the indoor heat exchanger 4. The high-pressure liquid refrigerant or two-phase refrigerant flowing out from the intermediate heat exchanger 6 is decompressed by the first decompression mechanism 31 to become a two-phase refrigerant, and then flows into the indoor heat exchanger 4. The gas refrigerant or two-phase refrigerant after heat exchange in the indoor heat exchanger 4 flows from the indoor heat exchanger 4 into the intermediate heat exchanger 6, and after undergoing the above-mentioned heat exchange to become a superheated gas refrigerant, is sucked into the compressor 1.

[0086] [Operation] Next, the flow of the refrigerant from the condenser until it flows into the intermediate heat exchanger 6 after the compressor 1 is started will be described below using a flowchart.

[0087] First, as a basic flow, a case where the temperature to be determined by the determination unit 93 is either the condenser outlet temperature or the evaporator outlet temperature will be described. However, since the flow of processing such as determination in the control device 9 is the same regardless of whether the temperature is the condenser outlet temperature or the evaporator outlet temperature, a case where the temperature to be determined is the condenser outlet temperature will be taken as an example here. Furthermore, the operation of the refrigeration cycle apparatus S here may be either cooling operation or heating operation.

[0088] 3 is a flowchart showing a basic flow of control of the refrigeration cycle apparatus S according to the embodiment of the present invention. First, a user issues a command to the refrigeration cycle apparatus S to perform cooling or heating operation, thereby starting the compressor 1 of the refrigeration cycle apparatus S (ST1).

[0089] As described above, at the start of the compressor 1, the pressure is equal on both the discharge side and the suction side of the compressor 1. Therefore, if refrigerant flows into the intermediate heat exchanger 6 when a pressure difference of the non-azeotropic refrigerant mixture must be ensured, heat exchange occurs in the intermediate heat exchanger 6, making it difficult to ensure the pressure difference of the non-azeotropic refrigerant mixture in the refrigerant circuit C. As a result, operation that meets the capacity required by the user cannot be performed, which may result in a decrease in comfort.

[0090] Therefore, the drive control section 94 of the control device 9 controls the bypass valve B1 to be fully open (ST2). In this state, the refrigerant is discharged from the compressor 1 to the condenser. Most of the refrigerant that flows out of the condenser flows into the evaporator through the bypass circuit B without flowing into the intermediate heat exchanger 6. By circulating the refrigerant that has passed through the bypass circuit B in this way through the refrigerant circuit C, it becomes easier to ensure a pressure difference between the discharge side and the suction side of the compressor 1.

[0091] While the refrigerant is circulating through the refrigerant circuit C, the control device 9 uses the temperature detection unit 91 to acquire information about the condenser outlet temperature detected by the condenser outlet temperature sensor 7 provided on the refrigerant outlet side of the condenser (ST3). The information about the condenser outlet temperature acquired by the temperature detection unit 91 is sent to the determination unit 93.

[0092] The determination unit 93 compares (ST4) the acquired condenser outlet temperature with a predetermined condensation temperature value pre-stored in the storage unit 92. If the comparison result shows that the condenser outlet temperature is smaller than the predetermined condensation temperature value (NO in ST5), the process returns to step ST3, and the comparison of the condenser outlet temperature with the predetermined condensation temperature value is continued.

[0093] This is because the condenser outlet temperature has not yet reached or exceeded the predetermined condensing temperature value, and the refrigerant pressure difference has not yet been secured, so heat exchange cannot be performed by causing the refrigerant to flow into the intermediate heat exchanger 6. Therefore, the control of the opening degree of the bypass valve B1 by the drive control unit 94 is maintained at full open as before.

[0094] On the other hand, when the judgment unit 93 compares the acquired condenser outlet temperature with the predetermined condensation temperature value and determines that the condenser outlet temperature is equal to or higher than the predetermined condensation temperature value (YES in ST5), the judgment unit 93 instructs the drive control unit 94 to change the opening of the bypass valve B1 from fully open to fully closed.

[0095] The drive control unit 94 controls the bypass valve B1 to be fully closed (ST6) based on the instruction from the determination unit 93. By this control, the refrigerant flowing out of the condenser does not flow directly into the evaporator through the bypass circuit B, but flows from the condenser into the intermediate heat exchanger 6.

[0096] Then, in the intermediate heat exchanger 6, heat exchange occurs between the refrigerant flowing out from the condenser and the refrigerant flowing out from the evaporator. In this state, the condenser outlet temperature is equal to or higher than the predetermined condensation temperature value, and the refrigerant pressure difference is ensured, so even if heat exchange occurs in the intermediate heat exchanger 6, operation can be performed in accordance with the capacity required by the user, and a decrease in comfort can be avoided.

[0097] Next, a description will be given of the flow of the refrigerant from the start of the compressor 1 to the flow of the refrigerant flowing out of the condenser into the intermediate heat exchanger 6, particularly when the refrigeration cycle apparatus S is in heating operation. Fig. 4 is a flowchart showing another aspect of the control flow of the refrigeration cycle apparatus according to the embodiment of the present invention.

[0098] The basic flow is as explained using Fig. 3. However, in the case of heating operation, not only has the condenser outlet temperature reached or exceeded the predetermined condensation temperature value, but the determination unit 93 also determines whether the condenser outlet temperature has reached or exceeded a threshold value (ST11).

[0099] This is because, as described above, if heat exchange is performed in the intermediate heat exchanger 6 when the condenser outlet temperature is not equal to or higher than a preset threshold, the temperature of the air blown into the room from the indoor heat exchanger 4 may decrease. If the temperature of the air blown into the room decreases, it will lead to a decrease in comfort for the user.

[0100] Therefore, only when the condenser outlet temperature is equal to or higher than the predetermined condensation temperature value and further equal to or higher than the threshold value, the refrigerant is caused to flow into the intermediate heat exchanger 6 to perform heat exchange (ST6). Therefore, even if the condenser outlet temperature is equal to or higher than the predetermined condensation temperature value (YES in ST5), if the condenser outlet temperature is not equal to or higher than the threshold value (NO in ST11), the process returns to step ST3, and the determination unit 93 again performs processing such as comparing the condenser outlet temperature with the predetermined condensation temperature value.

[0101] Next, a control flow will be described in which the control flow of the indoor fan 41 is combined with the above-described flow from when the compressor 1 is started until the refrigerant flowing out of the condenser into the intermediate heat exchanger 6. Note that this case also applies to a case in which the refrigeration cycle apparatus S performs heating operation. Fig. 5 is a flowchart illustrating the relationship between the control flow of the refrigeration cycle apparatus S according to an embodiment of the present invention and the control of the indoor fan 41 provided in the indoor heat exchanger 4 that functions as a condenser.

[0102] First, a user issues a heating operation command to the refrigeration cycle apparatus S, thereby starting the compressor 1 of the refrigeration cycle apparatus S (ST1). Then, in conjunction with the start of the compressor 1, the indoor fan 41 of the indoor heat exchanger 4 also starts (ST21).

[0103] The rotation speed of the indoor fan 41 here is a low preset rotation speed because the compressor 1 has just started up. In addition, the drive control unit 94 prohibits the rotation speed of the indoor fan 41 from increasing (ST22).

[0104] As described above, when the compressor 1 is started, the refrigerant cannot yet flow into the intermediate heat exchanger 6, so the drive control unit 94 of the control device 9 controls the bypass valve B1 to be fully open (ST2).

[0105] In addition, the control device 9 compares the condenser outlet temperature with a predetermined condensation temperature value based on information about the condenser outlet temperature detected by the condenser outlet temperature sensor 7, and also determines whether the condenser outlet temperature has reached or exceeded a threshold value (ST3 to ST5).

[0106] If the judgment unit 93 determines that the condenser outlet temperature is lower than the predetermined condensation temperature (NO in ST5), or if the judgment unit 93 determines that the condenser outlet temperature is lower than the threshold value (NO in ST11), the process returns to step ST3.

[0107] On the other hand, if it is determined that the condenser outlet temperature is equal to or higher than the predetermined condensation temperature value and equal to or higher than the threshold value (YES in ST5, YES in ST11), the determination unit 93 controls the drive control unit 94 to fully close the bypass valve B1 (ST6).

[0108] By this control, the refrigerant flowing out from the condenser flows from the condenser into the intermediate heat exchanger 6, where heat exchange takes place. As described above, in this state, the pressure difference of the refrigerant is ensured, so that operation can be performed in accordance with the capacity required by the user, and a decrease in comfort can be avoided.

[0109] Therefore, the state in which control to increase the rotation speed of the indoor fan 41 has been prohibited is lifted (ST23). Then, the determination unit 93 determines whether control of the rotation speed of the indoor fan 41 is necessary (ST24). Regarding the necessity of control of the rotation speed of the indoor fan 41, when there is a request to change the rotation speed based on various controls such as a user instruction, the determination unit 93 determines that control of the rotation speed of the indoor fan 41 is necessary.

[0110] If the determination unit 93 determines that control of the rotation speed of the indoor fan 41 is necessary (YES in ST24), it issues an instruction to the drive control unit 94 to change the rotation speed of the indoor fan 41 so that the rotation speed meets the request. The drive control unit 94 controls the rotation speed of the indoor fan 41 so that the rotation speed meets the request (ST25).

[0111] On the other hand, if the determination unit 93 determines that there is no particular need to change the previous rotation speed as a result of checking the request regarding the rotation speed of the indoor fan 41 (NO in ST24), it issues an instruction to the drive control unit 94 to maintain the previous rotation speed. Based on this instruction, the drive control unit 94 performs control to maintain the rotation speed of the indoor fan 41 (ST26).

[0112] The above has described a case in which the determination unit 93 uses the condenser outlet temperature acquired by the condenser outlet temperature sensor 7 or the evaporator outlet temperature acquired by the evaporator outlet temperature sensor 8 as the criterion for determining whether to flow the refrigerant into the bypass circuit B or into the intermediate heat exchanger 6.

[0113] However, as a criterion for judgment, in addition to using either the condenser outlet temperature or the evaporator outlet temperature, the temperature difference between the two can also be used. Figure 6 is a flowchart showing a flow of control of the refrigeration cycle apparatus S according to an embodiment of the present invention when the temperature difference between the condenser outlet temperature and the evaporator outlet temperature is used.

[0114] First, a user issues a command to perform cooling or heating operation to the refrigeration cycle apparatus S, thereby starting the compressor 1 of the refrigeration cycle apparatus S (ST1). Then, the drive control unit 94 of the control device 9 controls the bypass valve B1 to be fully open (ST2).

[0115] The temperature detection unit 91 of the control device 9 acquires information on the condenser outlet temperature and the evaporator outlet temperature detected by the condenser outlet temperature sensor 7 and the evaporator outlet temperature sensor 8 (ST31). Using the acquired values ​​of the condenser outlet temperature and the evaporator outlet temperature, the determination unit 93 calculates the temperature difference between them (ST32).

[0116] Then, the judgment unit 93 acquires a predetermined temperature difference value between the two that is pre-set in the memory unit 92, and compares the temperature difference between the condenser outlet temperature value and the evaporator outlet temperature value with the predetermined temperature difference value (ST33).

[0117] If the comparison result shows that the temperature difference between the two is smaller than the predetermined temperature difference value (NO in ST34), the process returns to step ST31, where the temperature difference between the newly acquired condenser outlet temperature and evaporator outlet temperature is calculated and compared with the predetermined temperature difference value.

[0118] On the other hand, if the determination unit 93 determines that the temperature difference between the two is equal to or greater than the predetermined temperature difference value (YES in ST34), the determination unit 93 instructs the drive control unit 94 to control the bypass valve B1 to be fully closed. Based on this instruction, the drive control unit 94 fully closes the bypass valve B1 (ST6).

[0119] As described above, by providing a bypass circuit and a bypass valve to prevent the refrigerant from flowing to the intermediate heat exchanger provided between the condenser and the evaporator, it is possible to provide a refrigeration cycle apparatus S and a control method for the refrigeration cycle apparatus S that can suppress a decrease in user comfort by ensuring a pressure difference of the non-azeotropic refrigerant, particularly when the compressor is started, and performing operation that matches the required capacity, even when an intermediate heat exchanger is provided using a non-azeotropic refrigerant.

[0120] It should be noted that the present invention is not limited to the above-described embodiment, but is merely an example of the present invention. In the implementation stage, the components can be modified and embodied without departing from the spirit of the invention, and various changes and improvements can be made to the above-described embodiment. Furthermore, various inventions can be created by appropriately combining multiple components disclosed in the above-described embodiment.

[0121] For example, some components may be deleted from all of the components shown in the embodiments. Furthermore, components from different embodiments may be combined as appropriate, and such modified or improved forms may also be included in the present invention. Such embodiments and their modifications are included in the scope and spirit of the inventions, and are also included in the scope of the inventions and their equivalents as defined in the claims.

[0122] In the above description, the determination of whether the refrigerant flowing out of the condenser should be passed to the bypass circuit B or the intermediate heat exchanger 6 is based on temperature, such as whether the condenser outlet temperature is equal to or higher than a predetermined condensation temperature. However, instead of temperature, the determination may be based on, for example, the difference between the pressure of the refrigerant on the high-pressure side and the pressure of the refrigerant on the low-pressure side, as measured by a pressure sensor.

[0123] Furthermore, the specified condensation temperature value, specified evaporation temperature value, specified temperature difference value, and threshold value may be fixed values, or may be set each time a judgment is made based on the operating conditions of the refrigeration cycle device S, and then the judgment may be made.

[0124] REFRIGERATION CONTROL UNIT, 91 TEMPERATURE DETECTOR, 92 MEMORY UNIT, 93 DETERMINATION UNIT, 94 DRIVE CONTROL UNIT, B BYPASS CIRCUIT, 94 REFRIGERATION CYCLE UNIT, 95 REFRIGERATION CYCLE UNIT, 96 REFRIGERATION CYCLE UNIT, 97 REFRIGERATION CYCLE UNIT, 98 REFRIGERATION CYCLE UNIT, 99 REFRIGERATION CYCLE UNIT, 90 REFRIGERATION CYCLE UNIT, 91 TEMPERATURE DETECTOR, 92 MEMORY UNIT, 93 DETERMINATION UNIT, 94 DRIVE CONTROL UNIT, B BYPASS CIRCUIT, 96 REFRIGERATION CYCLE UNIT, 97 REFRIGERATION CYCLE UNIT, 98 REFRIGERATION CYCLE UNIT, 9 ...

Claims

a refrigerant circuit in which a non-azeotropic refrigerant mixture is circulated, the refrigerant circuit including a compressor, a condenser, a pressure reducing mechanism, and an evaporator connected in sequence by a refrigerant pipe; an intermediate heat exchanger for heat exchange between the non-azeotropic refrigerant mixture flowing between the condenser and the pressure reducing mechanism and the non-azeotropic refrigerant mixture flowing between the evaporator and the compressor; a bypass circuit for bypassing the intermediate heat exchanger in a path between the condenser and the pressure reducing mechanism; a bypass valve provided in the bypass circuit; a condenser outlet temperature sensor for detecting the temperature of the non-azeotropic refrigerant mixture flowing downstream of the condenser; an evaporator outlet temperature sensor for detecting the temperature of the non-azeotropic refrigerant mixture flowing downstream of the evaporator; and a control device for controlling the compressor, the pressure reducing mechanism, and the bypass valve, the control device comprising: a determination unit for determining whether the condenser outlet temperature detected by the condenser outlet temperature sensor is equal to or higher than a predetermined condensation temperature value, or for determining whether the evaporator outlet temperature detected by the evaporator outlet temperature sensor is equal to or lower than a predetermined evaporation temperature value; a drive control unit that controls the bypass valve to be fully opened when the compressor is started up, and controls the bypass valve to be fully closed when the determination unit determines that the condenser outlet temperature is equal to or higher than the predetermined condensation temperature value or when the determination unit determines that the evaporator outlet temperature is equal to or lower than the predetermined evaporation temperature value.

2. A refrigerant circuit in which a compressor, a condenser, a pressure reducing mechanism and an evaporator are connected in sequence by a refrigerant piping, and in which a non-azeotropic refrigerant circulates; an intermediate heat exchanger in which the non-azeotropic refrigerant flowing between the condenser and the pressure reducing mechanism and the non-azeotropic refrigerant flowing between the evaporator and the compressor exchange heat; a bypass circuit in a path between the condenser and the pressure reducing mechanism, bypassing the intermediate heat exchanger; a bypass valve provided in the bypass circuit; a condenser outlet temperature sensor detecting the temperature of the non-azeotropic refrigerant flowing downstream of the condenser; an evaporator outlet temperature sensor detecting the temperature of the non-azeotropic refrigerant flowing downstream of the evaporator; and a control device controlling the compressor, the pressure reducing mechanism and the bypass valve, wherein the control device comprises: a determination unit for determining whether a temperature difference between a condenser outlet temperature detected by the condenser outlet temperature sensor and an evaporator outlet temperature detected by the evaporator outlet temperature sensor is equal to or greater than a predetermined temperature difference value set in advance; a drive control unit that controls the bypass valve to be fully opened when the compressor is started, and controls the bypass valve to be fully closed when the determination unit determines that the temperature difference is equal to or greater than the predetermined temperature difference value.

3. A refrigeration cycle device as described in claim 1 or claim 2, characterized in that when an indoor heat exchanger that exchanges heat with indoor air functions as the condenser, when the judgment unit judges that the condenser outlet temperature is equal to or higher than a predetermined threshold value, the drive control unit controls the bypass valve to be fully closed.

4. The refrigeration cycle device according to claim 3, characterized in that the indoor heat exchanger is provided with an indoor fan that circulates air through the indoor heat exchanger, and the control device performs control to prohibit an increase in the rotation speed of the indoor fan until the bypass valve is fully closed by the drive control unit.

5. A refrigerant circuit in which a non-azeotropic refrigerant is circulated, in which a compressor, a condenser, a pressure reduction mechanism, and an evaporator are connected in sequence by a refrigerant piping; an intermediate heat exchanger in which heat is exchanged between the non-azeotropic refrigerant flowing between the condenser and the pressure reduction mechanism and the non-azeotropic refrigerant flowing between the evaporator and the compressor; a bypass circuit in a path between the condenser and the pressure reduction mechanism, bypassing the intermediate heat exchanger; a bypass valve provided in the bypass circuit; a condenser outlet temperature sensor detecting the temperature of the non-azeotropic refrigerant flowing downstream of the condenser; an evaporator outlet temperature sensor detecting the temperature of the non-azeotropic refrigerant flowing downstream of the evaporator; and a control device for controlling the compressor, the pressure reduction mechanism, and the bypass valve, a step of determining whether the condenser outlet temperature is equal to or higher than a predetermined condensation temperature value, or determining whether the evaporator outlet temperature is equal to or lower than a predetermined evaporation temperature value; and a step of controlling the bypass valve to be fully closed when a comparison result shows that the condenser outlet temperature is equal to or higher than the predetermined condensation temperature value, or when the evaporator outlet temperature is equal to or lower than the predetermined evaporation temperature value.

6. A refrigerant circuit in which a non-azeotropic refrigerant is circulated, in which a compressor, a condenser, a pressure reducing mechanism, and an evaporator are connected in sequence by a refrigerant piping; an intermediate heat exchanger in which heat is exchanged between the non-azeotropic refrigerant flowing between the condenser and the pressure reducing mechanism and the non-azeotropic refrigerant flowing between the evaporator and the compressor; a bypass circuit in a path between the condenser and the pressure reducing mechanism, bypassing the intermediate heat exchanger; a bypass valve provided in the bypass circuit; a condenser outlet temperature sensor for detecting the temperature of the non-azeotropic refrigerant flowing downstream of the condenser; an evaporator outlet temperature sensor for detecting the temperature of the non-azeotropic refrigerant flowing downstream of the evaporator; and a control device for controlling the compressor, the pressure reducing mechanism, and the bypass valve, a step of calculating a temperature difference between the condenser outlet temperature and the evaporator outlet temperature; a step of determining whether the temperature difference is equal to or greater than a predetermined temperature difference value; and a step of controlling the bypass valve to be fully closed when the temperature difference is equal to or greater than the predetermined temperature difference value.

7. A control method for a refrigeration cycle device as described in claim 5 or 6, characterized in that, when an indoor heat exchanger that exchanges heat with indoor air functions as the condenser, after a step of comparing the condenser outlet temperature with a predetermined condensation temperature value, or comparing the evaporator outlet temperature with a predetermined evaporation temperature value, or after the step of comparing the temperature difference with the predetermined temperature difference value, a step of determining whether the condenser outlet temperature is equal to or higher than a preset threshold value, is provided, and when, as a result of the comparison, the condenser outlet temperature is equal to or higher than the predetermined condensation temperature value, or the evaporator outlet temperature is equal to or lower than the predetermined evaporation temperature value, or the temperature difference is equal to or higher than the predetermined temperature difference value and the condenser outlet temperature is equal to or higher than the threshold value, the bypass valve is controlled to be fully closed.

8. A method for controlling a refrigeration cycle device as described in claim 7, characterized in that the indoor heat exchanger is provided with an indoor fan that circulates air through the indoor heat exchanger, and further comprising a step of prohibiting an increase in the rotation speed of the indoor fan until the bypass valve is fully closed by a drive control unit.

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