Refrigeration cycle device and control method for refrigeration cycle device

Abstract

To suppress deterioration of comfort of a user by securing a pressure difference of a non-azeotropic refrigerant mixture in particular at start of a compressor and performing an operation corresponding to required capacity even when the non-azeotropic refrigerant mixture is used and an intermediate heat exchanger is provided.SOLUTION: A refrigeration cycle device includes: a refrigerant circuit C in which a compressor 1, a condenser, decompression means 3 and an evaporator are connected sequentially by refrigerant piping and a non-azeotropic refrigerant mixture circulates; an intermediate heat exchanger 6; a bypass circuit B that bypasses the intermediate heat exchanger 6; a bypass valve B1 provided in the bypass circuit B; a condenser outlet temperature sensor 7; an evaporator outlet temperature sensor 8; and a control device 9. The control device 9 includes: a determination section 93 that determines whether or not a condenser outlet temperature is a condensation temperature specified value or higher; and a drive control section 94 that performs control so that the bypass valve B1 becomes fully opened at start of the compressor 1 and that performs control so that the bypass valve B1 becomes fully closed when the determination section 93 determines that the condenser outlet temperature is the condensation temperature specified value or higher.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

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

[0003] When the temperature gradient of a non-azeotropic refrigerant mixture is large, the temperature difference between the air and the refrigerant that exchanges heat in the refrigerant flow passage at the outlet side 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, so the degree of supercooling in the condensation process and the degree of suction superheat in the evaporation process become smaller, making it difficult to ensure the degree of supercooling 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 is provided with an intermediate heat exchanger. In this intermediate heat exchanger, heat exchange takes place between the refrigerant at the condenser outlet side (refrigerant after passing through the condenser) and the refrigerant at the evaporator outlet side (refrigerant after passing through the evaporator). By carrying out such heat exchange, it is possible to secure a greater enthalpy difference, and therefore it is possible to secure the degree of subcooling and the degree of suction superheat, and it is believed that this makes it possible to prevent a decrease in COP. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 08-075290 Summary of the Invention [Problem to be solved by the invention]

[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, in a refrigeration cycle device using a non-azeotropic refrigerant, it is necessary to provide the above-mentioned intermediate heat exchanger, but in the intermediate heat exchanger, heat exchange between the high-pressure non-azeotropic refrigerant and the low-pressure non-azeotropic refrigerant is more actively performed due to the pressure difference, which creates a situation in which the non-azeotropic refrigerant is easily condensed or evaporated, making it difficult for the high-pressure pressure of the non-azeotropic refrigerant in the refrigerant circuit to increase and the low-pressure pressure to decrease.

[0008] In particular, in the refrigerant circuit in the above-mentioned Patent Document 1, the circuit configuration is such that the non-azeotropic refrigerant on the high pressure side and the non-azeotropic refrigerant on the low pressure side are always exchanging heat while the refrigeration cycle device is in operation. Therefore, it is difficult to ensure a pressure difference of the non-azeotropic refrigerant in the refrigerant circuit while the refrigeration cycle device is in operation. Therefore, it is difficult to reach the condensation temperature or evaporation temperature required for the refrigeration cycle device, and operation according to the required capacity cannot be performed, which reduces comfort.

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

[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 reduction mechanism, and an evaporator are connected in sequence 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 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 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 comprises a control device that controls the compressor, the pressure reducing mechanism, and the bypass valve, and the control device comprises a judgment unit that judges whether the condenser outlet temperature detected by the condenser outlet temperature sensor is equal to or higher than a predetermined condensation temperature value, or judges whether the evaporator outlet temperature detected by the evaporator outlet temperature sensor is equal to or higher than a predetermined evaporation 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 judgment unit judges that the condenser outlet temperature is equal to or higher than the predetermined condensation temperature value, or when the judgment unit judges that the evaporator outlet temperature is equal to or higher than the predetermined evaporation 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 reduction mechanism, and an evaporator are connected in sequence by refrigerant piping, 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 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 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 a refrigerant flowing downstream of the evaporator. The control device includes an evaporator outlet temperature sensor that detects the temperature of the non-azeotropic refrigerant mixture, and a control device that controls the compressor, the pressure reduction mechanism, and the 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] Furthermore, a control method for a refrigeration cycle apparatus according to an aspect of the present invention includes a refrigerant circuit in which a compressor, a condenser, a pressure reduction mechanism, and an evaporator are sequentially connected 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 reduction 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 reduction 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, an evaporator outlet temperature sensor that detects the temperature of the non-azeotropic refrigerant flowing downstream of the evaporator, and a refrigerant circuit in which the non-azeotropic refrigerant flowing between the condenser and the pressure reduction mechanism is exchanged with the non-azeotropic refrigerant flowing between the evaporator and the compressor. The compressor includes 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 up, acquiring a condenser outlet temperature from a condenser outlet temperature sensor, or acquiring an evaporator outlet temperature from an evaporator outlet temperature sensor, 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 higher than a predetermined evaporation temperature value, and controlling the bypass valve to be fully closed when the condenser outlet temperature is equal to or higher than the predetermined condensation temperature value, or when the evaporator outlet temperature and the evaporator outlet temperature are equal to or higher than the predetermined evaporation 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 reduction mechanism, and an evaporator are sequentially connected by a refrigerant pipe, 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 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 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 a refrigerant circuit in which the non-azeotropic refrigerant flowing downstream of the evaporator is detected. The system includes an evaporator outlet temperature sensor that detects the temperature of the refrigerant, and a control device that controls a compressor, a pressure reducing mechanism, and 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 if the temperature difference is equal to or greater than the predetermined temperature difference value. Effect of the Invention

[0014] According to the present invention, even when a non-azeotropic refrigerant is used and an intermediate heat exchanger is provided, a decrease in user comfort can be suppressed by ensuring a pressure difference of the non-azeotropic refrigerant, particularly at the start-up of the compressor, and performing operation in accordance with the required capacity. [Brief description of the drawings]

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

[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 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 the embodiment of the present invention is a non-azeotropic refrigerant mixture. A non-azeotropic refrigerant mixture has a property that the temperature changes (temperature gradient) even in a two-phase state during a condensation process or evaporation process at equal pressures. An example of such a non-azeotropic refrigerant mixture is R454C (a mixed refrigerant of R32 refrigerant and R1234yf refrigerant). In the following description, such a non-azeotropic refrigerant mixture will also be referred to as "refrigerant" as appropriate.

[0018] The compressor 1 draws in the refrigerant that has circulated through the refrigerant circuit C, compresses it, and discharges it to 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, in the outdoor heat exchanger 2, heat exchange takes place between the refrigerant and the air (outdoor air) flowing into the outdoor unit, and the 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] An outdoor fan 21 is provided inside the outdoor unit. The outdoor fan 21 takes in outside air into the outdoor unit, and expels the air that has exchanged heat with the refrigerant to the outside.

[0021] In the refrigerant circuit C, a pressure reducing means 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 means 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 means 3. This is to allow high-pressure refrigerant to flow into the intermediate heat exchanger 6 regardless of whether the refrigeration cycle apparatus S is in cooling operation or heating operation.

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

[0024] On the other hand, when a 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 decompression means 3 is disposed downstream of the intermediate heat exchanger 6 and between the outdoor heat exchanger 2. That is, during the heating operation, the second decompression mechanism 32 functions as the decompression means 3. At this time, the opening degree of the first decompression mechanism 31 is controlled so as to be fully open.

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

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

[0027] Further, an indoor fan 41 is provided inside the indoor unit. The indoor fan 41 takes in air into the indoor unit, and supplies the air that has undergone heat exchange with the refrigerant to 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 an outdoor heat exchanger 2 and an indoor heat exchanger 4. The intermediate heat exchanger 6 includes a high-pressure side flow path through which a refrigerant flows between the outdoor heat exchanger 2 and the indoor heat exchanger 4 passes, and a low-pressure side flow path through which a refrigerant flows between a four-way valve 5 and the compressor 1 passes. That is, in the intermediate heat exchanger 6, heat exchange is performed 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, and a temperature gradient is observed in the two-phase region in the evaporation / condensation process at equal pressure. With a refrigerant having a temperature gradient, the temperature difference between the refrigerant and the air gradually decreases in the evaporation and condensation processes, making it difficult to ensure an enthalpy difference, and therefore difficult to ensure the degree of subcooling and the degree of intake superheat required from the viewpoint of performance and reliability of the refrigeration cycle apparatus S. Therefore, in order to ensure an enthalpy difference and to ensure the degree of subcooling and the degree of intake superheat, an intermediate heat exchanger 6 is provided to exchange heat between the refrigerant after passing through the condenser and the refrigerant after passing through the evaporator.

[0031] Furthermore, in the refrigeration cycle apparatus S in 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 reducing means 3. That is, when the outdoor heat exchanger 2 serves as a condenser, the bypass circuit B is provided between the outdoor heat exchanger 2 and the first pressure reducing mechanism 31 that serves as the pressure reducing means 3, whereas when the indoor heat exchanger 4 serves as a condenser, the bypass circuit B is provided between the indoor heat exchanger 4 and the second pressure reducing mechanism 32 that serves as the pressure reducing means 3.

[0032] Further, the bypass circuit B is provided with a bypass valve B1. The bypass valve B1 is driven to be fully open or fully closed under the control of a control device 9 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 may be 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 not meeting the required capacity due to a large amount of refrigerant flowing out from 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 from 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 in 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] However, in the cooling operation, the outdoor heat exchanger 2 functions as a condenser, so 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, so 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] Further, an evaporator outlet temperature sensor 8 that detects the temperature of the refrigerant flowing out from the evaporator is provided downstream of the evaporator. As shown in the refrigerant circuit C of 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 flows out of the evaporator flows into the intermediate heat exchanger 6 via the four-way valve 5, and therefore, unlike the condenser outlet temperature sensor 7, the evaporator outlet temperature sensor 8 is provided only in one location, the above-mentioned position.

[0040] The control device 9 is provided in the refrigeration cycle apparatus S, and controls the pressure reducing means 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 contents described later, thereby ensuring a pressure difference of the non-azeotropic refrigerant mixture, particularly at the start of the compressor, and performing operation suited to the required capacity, thereby suppressing a decrease in comfort for the user.

[0041] In particular, for example, the control device 9 can control the opening degree of the bypass valve B1 to 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 embodiment of the present invention, with regard to the control device 9, only functions necessary for ensuring the pressure difference of the non-azeotropic refrigerant mixture at the start of the compressor 1 and operating in accordance with the required capacity will be described.

[0042] 2 is a block diagram showing an internal configuration of a control device 9 in a refrigeration cycle apparatus S according to an 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. Moreover, the input / output interface may be connected to each of the above-mentioned units, as well as each of the units 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 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 above-mentioned condenser outlet temperature sensor 7 or the evaporator outlet temperature sensor 8 to determine whether to cause the refrigerant to flow through the bypass circuit B or through 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 preset condensation temperature value, and judges whether the condenser outlet temperature is equal to or higher than the preset condensation temperature value.

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

[0050] In this way, the determination unit 93 executes the determination using any one or multiple conditions among the above-mentioned 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 is to be used is set in advance, and the determination process is executed at each of the above-mentioned preset timings.

[0051] The drive control unit 94 controls, for example, the opening degree of the pressure reducing means 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 manner, the drive control unit 94 controls the drive of each unit. With regard to control of the opening degree of the bypass valve B1, the drive control unit 94 controls the opening degree of the bypass valve B1 so that the bypass valve B1 is fully open when the compressor 1 is started.

[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 prevent a decrease in comfort for the user by operating the compressor in a state where the condensation temperature or evaporation temperature matching the required capacity is reached as soon as possible, it is necessary to ensure a refrigerant pressure difference as soon 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 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-up of the compressor 1, heat exchange will occur 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.

[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] In other words, when the bypass valve B1 is fully opened due to the difference in piping length or the pressure loss inside the intermediate heat exchanger 6, most of the refrigerant discharged from the compressor 1 and flowing out of the condenser when the compressor 1 is started 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 amount of 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 judgment unit 93 compares 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 to judge whether to flow the refrigerant into the bypass circuit B or into the intermediate heat exchanger 6.

[0059] Therefore, when 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 enable sufficient heat exchange in the intermediate heat exchanger 6. This can be considered as 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 viewpoint, the "predetermined condensation temperature value," the "predetermined evaporation temperature value," and the "predetermined temperature difference value" can be said to be any value that provides a sufficient pressure difference between the high-pressure side refrigerant and the low-pressure side refrigerant and allows the intermediate heat exchanger 6 to function effectively. These predetermined values ​​are determined in advance by experiments or the like from the above viewpoint, and are stored in the storage unit 92.

[0061] There is a slight time difference between the timing at which the pressure difference between the discharge side and the suction side at the start of the compressor 1 becomes a sufficient value to obtain the required capacity even if the intermediate heat exchanger 6 is operated, from a state in which there is no (small) pressure difference between the discharge side and the suction side, and the timing at which the intermediate heat exchanger starts to function effectively. Therefore, even if, for example, a predetermined condensation 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 condensation 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 performs the determination taking into consideration the following condition: In other words, the determination unit 93 performs the above-mentioned 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] When the condensation temperature drops, the temperature of the air supplied from the indoor heat exchanger 4 to the room drops. Particularly in the case of heating operation, the operation cannot be performed according to the required capacity, and the user feels cold air, which reduces comfort. In order to prevent such a decrease in comfort, the determination unit 93 determines whether the condenser outlet temperature has risen sufficiently, that is, 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, the condenser outlet temperature is in a sufficiently increased state. Therefore, even if the bypass valve B1 is fully closed and the refrigerant flows from the bypass circuit B to the intermediate heat exchanger 6, it is possible to prevent the user from feeling cold air even when heat exchange is performed in the intermediate heat exchanger 6, and thus it is possible to prevent a decrease in comfort.

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

[0068] Moreover, 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 as described above. The above-mentioned action 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 the impact of reducing comfort for the user is smaller than when the heating operation is performed.

[0069] In addition, when heating operation is performed in the refrigeration cycle apparatus S, if the above-mentioned judgment unit 93 judges whether the condenser outlet temperature has become equal to or higher than the threshold value and judges 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 would increase the amount of heat exchanged between the refrigerant and the indoor air in the indoor heat exchanger 4, lowering the condensation temperature, which could lead to 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 opening of the bypass valve B1 to be fully closed, and controls the rotation speed of the indoor fan 41 not to increase during the period from when the refrigerant flows through the bypass circuit B to when it flows 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 the storage unit 92 in advance.

[0073] Here, the flow of the refrigerant in the refrigerant circuit C when the refrigeration cycle apparatus S performs a 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 refrigerant, thereby supplying warmed air to the room. The high-temperature, high-pressure gas refrigerant releases heat through heat exchange 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 first pressure reduction mechanism 31, which is fully open, and then, at the start-up of the compressor 1, since the bypass valve B1 of the bypass circuit B is fully open, 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 flows into the second pressure reduction mechanism 32. The high-pressure liquid refrigerant is reduced in pressure as it passes through the second pressure reduction mechanism 32, becoming a low-pressure two-phase refrigerant. The low-pressure two-phase refrigerant flowing out of the second pressure reduction mechanism 32 flows into the outdoor heat exchanger 2. At this time, the opening degree of the second pressure reduction mechanism 32 is controlled by, for example, target discharge temperature control. Note that the target discharge temperature control is a control that controls the opening degree of the pressure reduction means to adjust the flow rate of the refrigerant so that the discharge temperature of the compressor 1 becomes the target discharge temperature.

[0077] In the outdoor heat exchanger 2, heat exchange takes place between the outdoor air and the low-pressure two-phase refrigerant, which absorbs heat and becomes a low-pressure gas refrigerant, which passes through the four-way valve 5 and flows into the intermediate heat exchanger 6. However, here, the refrigerant flowing out of the indoor heat exchanger 4 basically does not flow into the intermediate heat exchanger 6, and is not subjected to heat exchange in the intermediate heat exchanger 6. The refrigerant flowing 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 condensation temperature value and further equal to or higher than the threshold value, that is, during a stable state, the bypass valve B1 of the bypass circuit B is changed from fully open to fully closed by the drive control unit 94. As a result, the refrigerant that flows 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 exchange occurs between the high-pressure liquid or two-phase refrigerant after condensation flowing in from the indoor heat exchanger 4 and the low-pressure gas or two-phase refrigerant flowing out from the outdoor heat exchanger 2. The high-pressure liquid 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 further flows into the outdoor heat exchanger 2. On the other hand, the gas 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 sucked 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 flow of the refrigerant 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 flows 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, and then, because the bypass valve B1 of the bypass circuit B is fully open at the start of the compressor 1, 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 flows 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 a gas refrigerant. The cooled air is then supplied to the room. The gas refrigerant that flows out of the indoor heat exchanger 4 is sucked into the compressor 1 via the four-way valve 5 and the intermediate heat exchanger 6.

[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 condensation temperature value, that is, during stable operation, the bypass valve B1 of the bypass circuit B is changed from fully open to fully closed by the drive control unit 94. 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 is performed between the high-pressure liquid or two-phase refrigerant flowing out from the outdoor heat exchanger 2 and the low-pressure gas or two-phase refrigerant flowing out from the indoor heat exchanger 4. The high-pressure liquid or two-phase refrigerant flowing out from the intermediate heat exchanger 6 is depressurized in the first depressurization mechanism 31 to become a two-phase refrigerant, and then flows into the indoor heat exchanger 4. In addition, the gas 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 performing 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 start of the compressor 1 until the refrigerant flows into the intermediate heat exchanger 6 will be described below with reference to a flowchart.

[0087] First, as a basic flow, a case where the temperature to be judged by the judgment unit 93 is either the condenser outlet temperature or the evaporator outlet temperature will be described. However, since the flow of processing such as judgment 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 judged is the condenser outlet temperature will be taken as an example here. Also, the operation of the refrigeration cycle apparatus S here may be either a cooling operation or a 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 an instruction for cooling operation or heating operation to the refrigeration cycle apparatus S, thereby starting up 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. This makes it impossible to operate the system in accordance with the capacity required by the user, 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. In this way, the refrigerant that has passed through the bypass circuit B circulates through the refrigerant circuit C, making it easier to ensure a pressure difference between the discharge side and the suction side of the compressor 1.

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

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

[0093] This is because the condenser outlet temperature has not reached or exceeded the predetermined condensation temperature value, and the refrigerant pressure difference has not yet been secured, so the refrigerant cannot be caused to flow into the intermediate heat exchanger 6 to perform heat exchange. 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 judges 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 degree 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 based on an instruction from the determination unit 93 (ST6). 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 takes place between the refrigerant flowing out of the condenser and the refrigerant flowing out of 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 that even if heat exchange takes place 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 a 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 a heating operation is performed in the refrigeration cycle apparatus S. 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. In the case of heating operation, not only has the condenser outlet temperature reached or exceeded a predetermined condensation temperature value, but the judgment unit 93 also judges whether or not 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 while the condenser outlet temperature is not equal to or higher than a preset threshold value, the temperature of air blown into the room from the indoor heat exchanger 4 may decrease. If the temperature of air blown into the room decreases, this leads 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. 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 the process of comparing the condenser outlet temperature with the predetermined condensation temperature value, etc.

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

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

[0103] The rotation speed of the indoor fan 41 here is a preset low 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] At the start-up of the compressor 1, as described above, 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 is above a threshold value (ST3 to ST5).

[0106] If the determination unit 93 determines that the condenser outlet temperature is lower than the predetermined condensation temperature (NO in ST5), or 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 judgment 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, and heat exchange is performed. As described above, in this state, the refrigerant pressure difference is secured, so that operation can be performed according to 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 or not it is necessary to control the rotation speed of the indoor fan 41 (ST24). Regarding the necessity of controlling 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 it is necessary to control the rotation speed of the indoor fan 41.

[0110] Then, when 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 corresponds to the request. The drive control unit 94 controls the rotation speed of the indoor fan 41 so that the rotation speed corresponds to the request (ST25).

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

[0112] The above describes a case in which the judgment 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 a criterion for determining whether to flow the refrigerant through the bypass circuit B or through 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. Fig. 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 up the compressor 1 of the refrigeration cycle apparatus S (ST1). Then, the drive control unit 94 of the control device 9 performs control to fully open the bypass valve B1 (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 the two (ST32).

[0116] Then, the judgment unit 93 acquires a predetermined temperature difference value between the two that is preset 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 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 comfort for the user by ensuring a pressure difference of the non-azeotropic refrigerant, particularly at the start-up of the compressor, and performing operation in accordance with 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 without departing from the gist of the invention, and various modifications and improvements can be made to the above-described embodiment. In addition, various inventions can be created by appropriately combining multiple components disclosed in the above-described embodiment.

[0121] For example, some of the components shown in the embodiment may be deleted. Furthermore, components from different embodiments may be appropriately combined, and such modified or improved forms may also be included in the present invention. Such embodiments and modifications are included in the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims.

[0122] In the above description, the determination as to whether the refrigerant flowing out of the condenser should be passed through the bypass circuit B or through 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, it is also possible to use, for example, the difference in pressure between the high-pressure side refrigerant and the low-pressure side refrigerant, measured using a pressure sensor, as the criterion for this determination.

[0123] In addition, the specified condensation temperature value, the specified evaporation temperature value, the specified temperature difference value, and the threshold value may be fixed values, or they may be set each time a judgment is made based on the operating conditions of the refrigeration cycle apparatus S. [Explanation of symbols]

[0124] REFERENCE SIGNS LIST 1 compressor, 2 outdoor heat exchanger, 21 outdoor fan, 3 pressure reducing means, 4 indoor heat exchanger, 41 indoor fan, 5 four-way valve, 6 intermediate heat exchanger, 7 condenser outlet temperature sensor, 71 first condenser outlet temperature sensor, 72 second condenser outlet temperature sensor, 8 evaporator outlet temperature sensor, 9 control device, 91 temperature detection unit, 92 memory unit, 93 determination unit, 94 drive control unit, B bypass circuit, B1 bypass valve, C refrigerant circuit, S refrigeration cycle device

Claims

1. a refrigerant circuit in which a compressor, a condenser, a pressure reducing means, and an evaporator are connected in sequence by a refrigerant pipe, and in which a non-azeotropic refrigerant mixture circulates; an intermediate heat exchanger in which heat is exchanged between the non-azeotropic refrigerant flowing between the condenser and the pressure reducing means and the non-azeotropic refrigerant flowing between the evaporator and the compressor; a bypass circuit that bypasses the intermediate heat exchanger in a path between the condenser and the pressure reducing means; 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; a control device that controls the compressor, the pressure reducing means, and the bypass valve, The control device includes: a determination unit that determines whether or not the condenser outlet temperature detected by the condenser outlet temperature sensor is equal to or higher than a predetermined condensation temperature value, or that determines whether or not 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; A refrigeration cycle device comprising:

2. a refrigerant circuit in which a compressor, a condenser, a pressure reducing means, and an evaporator are connected in sequence by a refrigerant pipe, and in which a non-azeotropic refrigerant mixture circulates; an intermediate heat exchanger in which heat is exchanged between the non-azeotropic refrigerant flowing between the condenser and the pressure reducing means and the non-azeotropic refrigerant flowing between the evaporator and the compressor; a bypass circuit that bypasses the intermediate heat exchanger in a path between the condenser and the pressure reducing means; 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; a control device that controls the compressor, the pressure reducing means, and the bypass valve, The control device includes: a determination unit that determines 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 that is 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; A refrigeration cycle device comprising:

3. When an indoor heat exchanger that exchanges heat with indoor air functions as the condenser, 3. The refrigeration cycle apparatus according to claim 1, wherein the drive control unit controls the bypass valve to be fully closed when the determination unit determines that the condenser outlet temperature is equal to or higher than a preset threshold value.

4. The indoor heat exchanger includes an indoor fan that circulates air through the indoor heat exchanger, 4. The refrigeration cycle apparatus according to claim 3, wherein 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 compressor, a condenser, a pressure reducing means, and an evaporator are connected in sequence by a refrigerant pipe, and in which a non-azeotropic refrigerant mixture circulates; an intermediate heat exchanger in which heat is exchanged between the non-azeotropic refrigerant flowing between the condenser and the pressure reducing means and the non-azeotropic refrigerant flowing between the evaporator and the compressor; a bypass circuit that bypasses the intermediate heat exchanger in a path between the condenser and the pressure reducing means; 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; a control device that controls the compressor, the pressure reducing means, and the bypass valve, controlling the bypass valve to be fully opened at the start of the compressor; acquiring a condenser outlet temperature from the condenser outlet temperature sensor, or acquiring an evaporator outlet temperature from the evaporator outlet temperature sensor; 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; a step of controlling the bypass valve to be fully closed when 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 as a result of the comparison; A method for controlling a refrigeration cycle device comprising:

6. a refrigerant circuit in which a compressor, a condenser, a pressure reducing means, and an evaporator are connected in sequence by a refrigerant pipe, and in which a non-azeotropic refrigerant mixture circulates; an intermediate heat exchanger in which heat is exchanged between the non-azeotropic refrigerant flowing between the condenser and the pressure reducing means and the non-azeotropic refrigerant flowing between the evaporator and the compressor; a bypass circuit that bypasses the intermediate heat exchanger in a path between the condenser and the pressure reducing means; 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; a control device that controls the compressor, the pressure reducing means, and the bypass valve, controlling the bypass valve to be fully opened at the start of the compressor; acquiring a condenser outlet temperature from the condenser outlet temperature sensor and an evaporator outlet temperature from the evaporator outlet temperature sensor; Calculating a 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; controlling the bypass valve to be fully closed when the temperature difference is equal to or greater than the predetermined temperature difference value; A method for controlling a refrigeration cycle device comprising:

7. When an indoor heat exchanger that exchanges heat with indoor air functions as the condenser, a step of determining whether or not the condenser outlet temperature is equal to or greater than a preset threshold value after the step of comparing the condenser outlet temperature with a predetermined condensation temperature value, or the step of comparing the evaporator outlet temperature with a predetermined evaporation temperature value, or the step of comparing the temperature difference with the predetermined temperature difference value, 7. The control method for a refrigeration cycle apparatus according to claim 5, wherein the bypass valve is controlled to be fully closed 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.

8. The indoor heat exchanger includes an indoor fan that circulates air through the indoor heat exchanger, 8. The method for controlling a refrigeration cycle apparatus according to claim 7, further comprising the 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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