Refrigeration cycle device

Abstract

In this refrigeration cycle device (1), a heat exchanger (4) includes a first passage (41) provided between a condenser (3) and a branch point (40) in a first flow passage (70), and a second passage (42) provided between a second expansion valve (7) and an injection port (24) in a second flow passage (90). Heat is exchanged between a refrigerant flowing through the first passage (41) and a refrigerant flowing through the second passage (42). The injection port (24) is provided in a compressor (2) in a portion where the internal pressure is compressed to an intermediate value between a discharge pressure and a suction pressure, and the intermediate value is set to a pressure value such that the differential pressure between the suction pressure and the intermediate value is less than half the differential pressure between the suction pressure and the discharge pressure.

Description

Refrigeration cycle equipment

[0001] The present invention relates to a refrigeration cycle device.

[0002] International Publication No. 2015 / 173848 (Patent Document 1) discloses a refrigeration cycle device in which a refrigerant branched from a branching point of a refrigerant flow path between a condenser and an expansion valve is decompressed and then supplied to an injection port of a compressor via an injection flow path, and the refrigerant is merged with an intermediate-pressure refrigerant in the compressor.

[0003] In a conventional refrigeration cycle device having such a configuration, a portion of the refrigerant leaving the condenser is merged with the intermediate-pressure refrigerant in the compressor, thereby increasing the flow rate of refrigerant supplied from the compressor to the condenser, thereby improving the condensing capacity of the condenser.

[0004] In such a conventional refrigeration cycle device, an internal heat exchanger is provided to exchange heat between the refrigerant flow path between the condenser and the branch point and the injection flow path. The internal heat exchanger exchanges heat between the refrigerant that has left the condenser and the refrigerant that has been branched at the branch point and reduced in pressure to a lower temperature, thereby adjusting the temperature of the refrigerant supplied to the injection port of the compressor.

[0005] International Publication No. 2015 / 173848

[0006] However, in a refrigeration cycle apparatus equipped with an internal heat exchanger as described above, when a flammable natural refrigerant such as R290 or R600a is used as a refrigerant in order to reduce the burden on the environment, the following problems have arisen.

[0007] When a flammable refrigerant is used in a refrigeration cycle device, the amount of refrigerant sealed in the refrigeration cycle device is limited to a small amount, and the compressor discharge pressure and discharge temperature are limited to low levels, in order to improve the safety of the refrigeration cycle device compared to when a non-flammable refrigerant is used.

[0008] Due to such limitations on the amount of refrigerant and the limitations on the discharge pressure and discharge temperature of the compressor, there is a problem in refrigeration cycle devices where the condensing capacity of the condenser is lower when a flammable refrigerant is used than when a non-flammable refrigerant is used.

[0009] In order to improve the condensing capacity of the condenser when a flammable refrigerant is used, it is conceivable to increase the flow rate of the refrigerant supplied to the injection port of the compressor, thereby increasing the flow rate of the refrigerant supplied from the compressor to the condenser. However, when a flammable refrigerant is used, the compressor's discharge pressure and discharge temperature are limited, making it difficult to sufficiently ensure the temperature difference between the high-temperature side (the side between the condenser and the branch point) and the low-temperature side (the side of the injection flow path) in the internal heat exchanger.

[0010] Therefore, when a flammable refrigerant is used, increasing the flow rate of the refrigerant supplied to the compressor's injection port can result in a low-temperature refrigerant being supplied to the injection port due to insufficient heat exchange in the internal heat exchanger. In such a case, the compressor discharge temperature drops, resulting in a drop in the condensing temperature. A drop in the compressor discharge temperature can cause problems with the operation of devices that generate high-temperature water using the heat generated by the condenser, such as water heaters.

[0011] The present disclosure is intended to solve the above-mentioned problems, and its purpose is to suppress a decrease in the condensing capacity of a condenser and a decrease in the discharge temperature of a compressor when a flammable refrigerant is used in a refrigeration cycle device.

[0012] The present disclosure relates to a refrigeration cycle apparatus including a refrigerant circuit including a compressor, a condenser, a first expansion valve, and an evaporator, and in which a flammable refrigerant is sealed. The refrigeration cycle apparatus includes a first flow path in which a refrigerant circulates through the compressor, the condenser, the first expansion valve, and the evaporator in that order in the refrigerant circuit. A second flow path branches from a branch point of the first flow path between the condenser and the first expansion valve and returns refrigerant that has passed through the condenser to an injection port provided in the compressor. A second expansion valve and a heat exchanger are disposed in the second flow path in this order from the branch point. The heat exchanger includes a first passage provided in the first flow path between the condenser and the branch point, and a second passage provided in the second flow path between the second expansion valve and the injection port, and exchanges heat between the refrigerant flowing through the first passage and the refrigerant flowing through the second passage. The injection port is provided in a portion of the compressor where the internal pressure is compressed to an intermediate value between the discharge pressure and the suction pressure, and the intermediate value is set to a pressure value such that the differential pressure between the suction pressure and the intermediate value is less than half the differential pressure between the suction pressure and the discharge pressure.

[0013] According to the refrigeration cycle device of the present disclosure, when a flammable refrigerant is used, it is possible to suppress a decrease in the condensing capacity of the condenser and to suppress a decrease in the discharge temperature of the compressor.

[0014] FIG. 1 is an overall configuration diagram of a refrigeration cycle device in embodiment 1. FIG. 2 is a cross-sectional view of a compression mechanism part of a compressor in embodiment 1. FIG. 3 is a diagram showing pressure setting of a part where an injection port is provided in the compressor in embodiment 1. FIG. 4 is a block diagram showing a control configuration of a refrigeration cycle device in embodiment 1. FIG. 5 is a flowchart showing a first example of opening degree control of a second expansion valve in embodiment 1. FIG. 6 is a flowchart showing a second example of opening degree control of a second expansion valve in embodiment 1. FIG. 7 is an overall configuration diagram of a refrigeration cycle device in embodiment 2. FIG. 8 is a block diagram showing a control configuration of a refrigeration cycle device in embodiment 2.

[0015] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. While several embodiments will be described below, it is intended from the beginning of the application that the configurations described in each embodiment may be appropriately combined. Note that identical or corresponding parts in the drawings are designated by the same reference numerals, and their description will not be repeated.

[0016] Embodiment 1 (Overall configuration of refrigeration cycle apparatus 1) Fig. 1 is a diagram showing the overall configuration of a refrigeration cycle apparatus 1 in embodiment 1. Note that Fig. 1 functionally shows the connection relationships and arrangement of the devices in the refrigeration cycle apparatus 1, and does not necessarily show the physical spatial arrangement.

[0017] Referring to FIG. 1, the refrigeration cycle device 1 includes a compressor 2, a condenser 3, an internal heat exchanger 4, a first expansion valve 5, an evaporator 6, a second expansion valve 7, an intake temperature sensor 81, a discharge temperature sensor 82, and an outlet temperature sensor 83.

[0018] The refrigeration cycle device 1 is provided with a refrigerant circuit 10 and an injection path 11 as paths through which the refrigerant flows.

[0019] The refrigerant circuit 10 includes a compressor 2, a condenser 3, an internal heat exchanger 4, a first expansion valve 5, and an evaporator 6. The refrigerant circuit 10 is provided with a first flow path 70 through which the refrigerant circulates in the order of the compressor 2, the condenser 3, the internal heat exchanger 4, the first expansion valve 5, and the evaporator 6. A flammable refrigerant is sealed in the refrigerant circuit 10. The flammable refrigerant is a natural refrigerant such as R290 or R600a, for example.

[0020] The injection path 11 includes the second expansion valve 7 and the internal heat exchanger 4. The injection path 11 is provided with a second flow path 90 through which the refrigerant flows through the second expansion valve 7, the internal heat exchanger 4, and the injection port 24 in this order.

[0021] The second flow path 90 branches off from the branch point 40 of the first flow path 70 between the condenser 3 and the first expansion valve 5, and is a flow path that returns the refrigerant that has passed through the condenser 3 to the inside of the compressor 2 from the injection port 24. In the second flow path 90 between the branch point 40 and the injection port 24, the second expansion valve 7 and the internal heat exchanger 4 are provided in this order from the branch point 40.

[0022] The internal heat exchanger 4 is formed by a HIC (Heat Inter Changer). The internal heat exchanger 4 has a first passage 41 and a second passage 42, and is configured to exchange heat between the refrigerant flowing through the first passage 41 and the refrigerant flowing through the second passage 42. The first passage 41 is provided in the first flow path 70 between the condenser 3 and the branch point 40. The second passage 42 is provided in the second flow path 90 between the second expansion valve 7 and the injection port 24.

[0023] In the first passage 41, a high-temperature first refrigerant flows after leaving the condenser 3 in the first flow path 70 and before being expanded by the first expansion valve 5. On the other hand, in the second passage 42, a second refrigerant that is lower in temperature than the first refrigerant flows. This is because the refrigerant that leaves the condenser 3 in the first flow path 70 is expanded by the second expansion valve 7 in the second flow path 90 that branches off from the first flow path 70 at the branch point 40 before being expanded by the first expansion valve 5, thereby becoming the second refrigerant that is lower in temperature than the first refrigerant. In the internal heat exchanger 4, the second refrigerant flowing in the second passage 42 exchanges heat with the first refrigerant flowing in the first passage 41, and is then supplied to the injection port 24 of the compressor 2.

[0024] In the internal heat exchanger 4, heat is exchanged between the first refrigerant flowing through the first passage 41 and the second refrigerant flowing through the second passage 42, thereby allowing the second refrigerant to evaporate. As a result, the second refrigerant discharged from the second passage 42 of the internal heat exchanger 4 can be supplied to the injection port 24 of the compressor 2 as a refrigerant gas.

[0025] The compressor 2 is a compressor driven by a motor. The compressor 2 draws in and compresses the low-temperature, low-pressure gas refrigerant discharged from the evaporator 6, and discharges the high-temperature, high-pressure gas refrigerant. Various types of compressors can be used for the compressor 2, such as a scroll type, a rotary type, or a screw type. In the first embodiment, a scroll type compressor will be described as an example.

[0026] The drive frequency of the compressor 2 can be changed as desired by inverter control. The compressor 2 is configured to adjust its rotation speed in accordance with a control signal from a control device 50 shown in Fig. 4. The control device 50 shown in Fig. 4 controls the amount of refrigerant circulated by adjusting the rotation speed of the compressor 2. In this way, the control device 50 shown in Fig. 4 can adjust the capacity of the refrigeration cycle apparatus 1.

[0027] The condenser 3 is a heat exchanger in which the high-temperature, high-pressure gas refrigerant discharged from the compressor 2 exchanges heat (radiates heat) with outside air. In the condenser 3, the refrigerant is condensed and transformed into a liquid phase through this heat exchange. The refrigerant discharged from the compressor 2 is condensed and liquefied in the condenser 3 and flows out of the condenser 3. A fan (not shown) that blows outside air is attached to the condenser 3 to increase the efficiency of heat exchange.

[0028] The first expansion valve 5 reduces the pressure of the refrigerant by expanding the refrigerant condensed in the condenser 3. The refrigerant expands in the first expansion valve 5, becoming a low-pressure two-phase refrigerant. The evaporator 6 is a heat exchanger that exchanges heat (absorbs heat) between the refrigerant expanded in the first expansion valve 5 and air. In the evaporator 6, the two-phase refrigerant is evaporated by this heat exchange and changes into gas refrigerant. The evaporator 6 is configured to exchange heat between the refrigerant expanded in the first expansion valve 5 and air. A fan (not shown) is attached to the evaporator 6 to increase the efficiency of heat exchange. The refrigerant evaporated in the evaporator 6 and changed into gas refrigerant is sent to the compressor 2.

[0029] The internal heat exchanger 4 reduces the temperature of the first refrigerant by exchanging heat with a second refrigerant that is lower in temperature than the first refrigerant after it leaves the condenser 3 and before it is expanded by the first expansion valve 5. This increases the degree of subcooling of the first refrigerant before it is expanded by the first expansion valve 5, improving the coefficient of performance (COP) and enabling energy savings during operation of the refrigeration cycle apparatus 1.

[0030] The second flow path 90 is a flow path branching off from the branch point 40 of the first flow path 70 between the condenser 3 and the first expansion valve 5, and is a flow path that returns the refrigerant that has passed through the condenser 3 to the injection port 24 of the compressor 2.

[0031] The second expansion valve 7 is an electronic expansion valve that expands the high-pressure refrigerant that has left the condenser 3 and flowed through the branch point 40, thereby reducing the pressure of the refrigerant to an intermediate pressure. The second expansion valve 7 can change the flow rate and temperature of the refrigerant flowing through the second flow path 90 by changing the valve opening. The valve opening of the second expansion valve 7 is controlled by a control device 50 shown in FIG. 4.

[0032] An intake temperature sensor 81 that detects the intake temperature of the refrigerant is provided in the piping on the suction side of the compressor 2. A discharge temperature sensor 82 that detects the discharge temperature of the refrigerant is provided in the piping on the discharge side of the compressor 2. An outlet temperature sensor 83 that detects the outlet temperature of the refrigerant from the second passage 42 of the internal heat exchanger 4 is provided in the piping on the outlet side of the second passage 42 of the internal heat exchanger 4. Detection signals from the intake temperature sensor 81, the discharge temperature sensor 82, and the outlet temperature sensor 83 are sent to the control device 50 shown in FIG. 4 . In addition to these sensors, various other sensors are provided in the refrigeration cycle apparatus 1.

[0033] (Structure of Compressor 2) Fig. 2 is a cross-sectional view of the compression mechanism 200 of the compressor 2 in embodiment 1. The compression mechanism 200 includes an orbiting scroll 91 and a fixed scroll 92. The fixed scroll 92 is fixed to the sealed container 100 via a frame 77. The orbiting scroll 91 is oscillated by rotation of a rotating shaft (not shown) of the compressor 2.

[0034] The orbiting scroll 91 includes an orbiting scroll 91b that is a spiral protrusion. The fixed scroll 92 includes a fixed scroll 92b that is a spiral protrusion. The orbiting scroll 91b and the fixed scroll 92b are configured according to an involute curve. The orbiting scroll 91 and the fixed scroll 92 are arranged in a symmetrical spiral shape in which the orbiting scroll 91b and the fixed scroll 92b are combined in opposite phases with respect to the center of rotation of the rotation shaft of the compressor 2. Hereinafter, the symmetrical spiral-shaped structural portion of the compression mechanism 200 formed by the orbiting scroll 91 and the fixed scroll 92, in which the orbiting scroll 91b and the fixed scroll 92b are combined, will be referred to as the "volute structure."

[0035] As shown in Figure 2, the center of the base circle of the involute curve described by oscillating spiral body 91b is defined as base circle center 204a. The center of the base circle of the involute curve described by fixed spiral body 92b is defined as base circle center 204b. As base circle center 204a rotates around base circle center 204b, oscillating spiral body 91b performs an oscillating motion around fixed spiral body 92b.

[0036] When viewed along the spiral from the center to the end in the expanding direction of the spiral, multiple contact points are formed between the inward surface 205a of the oscillating spiral 91b and the outward surface 206b of the fixed spiral 92b, which divides the gap between the inward surface 205a of the oscillating spiral 91b and the outward surface 206b of the fixed spiral 92b, forming multiple compression chambers such as compression chamber 71a1 and compression chamber 71a2.

[0037] When viewed along the spiral from the center to the end in the expanding direction of the spiral, multiple contact points are formed between the inward surface 205b of the fixed spiral 92b and the outward surface 206a of the oscillating spiral 91b. As a result, the gap between the inward surface 205b of the fixed spiral 92b and the outward surface 206a of the oscillating spiral 91b is divided by multiple contact points, and multiple compression chambers such as compression chamber 71b1 and compression chamber 71b2 are formed.

[0038] In this way, in the compression mechanism section 200, the oscillating spiral body 91b provided on the oscillating base plate of the oscillating scroll 91 and the fixed spiral body 92b provided on the fixed base plate of the fixed scroll 92 are combined to form multiple compression chambers 71a1, 71a2, 71b1, and 71b2.

[0039] Spiral structure 93, which is a combination of oscillating spiral body 91b and fixed spiral body 92b, has a symmetrical spiral shape. As a result, as shown in Figure 2, multiple pairs of compression chambers 71a (71a1, 71a2) and compression chambers 71b (71b1, 71b2) are formed symmetrically about the center of rotation of the rotation shaft from the outside to the inside of the spiral within spiral structure 93. Hereinafter, compression chambers 71a and 71b will be collectively referred to as compression chambers 71.

[0040] The central portion of spiral structure 93 is an innermost chamber defined by a space surrounded by inward surfaces 205a of oscillating spiral body 91b and inward surfaces 205b of fixed spiral body 92b. Discharge port 201 for discharging compressed refrigerant is provided in the portion of fixed base plate 2a that forms the innermost chamber.

[0041] Refrigerant inlets 7 c and 7 d are provided on the outer periphery of the spiral structure 93 to guide the refrigerant drawn into the compressor 2 to the compression mechanism 200 .

[0042] The refrigerant drawn into compressor 2 is taken into suction chamber 74 of compression mechanism 200 through refrigerant inlet port 7c and refrigerant inlet port 7d. When oscillating scroll 91b rotates, the position where fixed scroll 92b and oscillating scroll 91b come into contact moves, changing the volume of compression chamber 71, thereby compressing the refrigerant in compression chamber 71. The compressed refrigerant is discharged from discharge port 201.

[0043] As described above, the compression mechanism 200 is provided with a plurality of compression chambers 71a1, 71a2, 71b1, and 71b2. The plurality of compression chambers 71a1, 71a2, 71b1, and 71b2 may be provided with injection ports 29, 28, 26, and 27 as shown in the figure. The injection ports 29, 28, 26, and 27 are refrigerant inlet ports for injecting the refrigerant supplied from the injection port 24 into the compressor into any one of the plurality of compression chambers 71a1, 71a2, 71b1, and 71b2.

[0044] In the compression mechanism section 200, by providing any one of the injection ports 29, 28, 26, and 27, it is possible to inject the refrigerant supplied to the inside of the compressor from the injection port 24 into any one of the multiple compression chambers 71a1, 71a2, 71b1, and 71b2.

[0045] FIG. 3 is a diagram illustrating the setting of pressure in a portion of the compressor 2 according to the first embodiment where the injection port 24 is provided. FIG. 3 shows the internal pressure P of the compressor 2. As described above, the compressor 2 is provided with an injection port in any of the multiple compression chambers 71a1, 71a2, 71b1, and 71b2, so that the injection port 24 can be provided in a compression chamber corresponding to a portion compressed to an intermediate value Pm between the suction pressure Ps and the discharge pressure Pd, as shown in FIG. 3 . The intermediate value Pm is set to a pressure value such that the pressure difference B between the suction pressure Ps of the compressor 2 and the intermediate value Pm is less than half (A / 2) of the pressure difference A between the suction pressure Ps and the discharge pressure Pd of the compressor 2.

[0046] One reason why the pressure at the portion where the injection port 24 is provided is set to the intermediate value Pm such that the pressure difference B between the suction pressure Ps of the compressor 2 and the intermediate value Pm is less than half (A / 2) of the pressure difference A between the suction pressure Ps and the discharge pressure Pd of the compressor 2 is as follows: In a refrigeration cycle apparatus configured like the refrigeration cycle apparatus 1, the intermediate value Pm that maximizes the COP can be calculated using the following equation (1):

[0047] Pm < (Ps × Pd)0.5 ...(1) The intermediate value Pm obtained by the above equation (1) is such that the differential pressure B between the suction pressure Ps of the compressor 2 and the intermediate value Pm is less than half (A / 2) of the differential pressure A between the suction pressure Ps and discharge pressure Pd of the compressor 2.

[0048] Generally, when the refrigerant discharged from the second passage 42 of the internal heat exchanger 4 is injected into the compressor 2, the pressure at the portion where the injection port is provided is set to half (A / 2) of the pressure difference A between the suction pressure Ps and discharge pressure Pd of the compressor 2. However, when injecting a refrigerant in this conventional manner, if a flammable refrigerant is used, the discharge pressure and discharge temperature of the compressor 2 are suppressed as described above, and therefore the temperature difference between the first refrigerant passing through the first passage 41 and the second refrigerant passing through the second passage 42 in the internal heat exchanger 4 is suppressed. As a result, evaporation of the second refrigerant through heat exchange in the internal heat exchanger 4 is not promoted, and a refrigerant with a temperature lower than that of the refrigerant at the portion where the injection port is provided is injected into the compressor 2, which may result in a drop in the discharge temperature of the compressor 2.

[0049] In the first embodiment, based on the above formula (1), the injection port 24 is provided so that the pressure difference B between the suction pressure Ps of the compressor 2 and the intermediate value Pm is the intermediate value Pm that is less than half (A / 2) of the pressure difference A between the suction pressure Ps and the discharge pressure Pd of the compressor 2. When the pressure in the portion of the compressor 2 where the injection port 24 is provided is set to the intermediate value Pm that is less than half (A / 2) of the pressure difference A between the suction pressure Ps and the discharge pressure Pd of the compressor 2, the saturation temperature at which the second refrigerant evaporates through heat exchange in the internal heat exchanger 4 is lower than when the intermediate value is set to half (A / 2) of the pressure difference A between the suction pressure Ps and the discharge pressure Pd of the compressor 2. Therefore, with regard to the temperature difference between the first refrigerant passing through the first passage 41 and the second refrigerant passing through the second passage 42 in the internal heat exchanger 4, it is possible to ensure a temperature difference that can promote evaporation of the second refrigerant through heat exchange.

[0050] Therefore, in the refrigeration cycle apparatus 1 of embodiment 1, when a flammable refrigerant is used, it is possible to suppress a decrease in the discharge temperature of the compressor 2. As a result, in the refrigeration cycle apparatus 1 of embodiment 1, when a flammable refrigerant is used, it is possible to suppress a decrease in the condensing capacity of the condenser 3 and to suppress a decrease in the discharge temperature of the compressor 2. Because such effects can be expected, in the refrigeration cycle apparatus 1 of embodiment 1, when a flammable refrigerant is used, it is possible to prevent problems from occurring in the operating state of equipment that obtains high-temperature water based on the heat generation amount of the condenser 3, such as a water heater.

[0051] Furthermore, when the pressure in the portion where the injection port 24 is provided is set to an intermediate value Pm that is less than half (A / 2) of the differential pressure A between the suction pressure Ps and discharge pressure Pd of the compressor 2, the period for heating the refrigerant after mixing the refrigerant injected from the injection port 24 in the compressor 2 with the refrigerant being compressed in the compressor 2 is longer than when the intermediate value is set to half (A / 2) of the differential pressure A between the suction pressure Ps and discharge pressure Pd of the compressor 2.

[0052] Therefore, in the refrigeration cycle apparatus 1 of the first embodiment, when a flammable refrigerant is used, it is possible to further suppress a decrease in the discharge temperature of the compressor 2. As a result, in the refrigeration cycle apparatus 1 of the first embodiment, when a flammable refrigerant is used, it is possible to further suppress a decrease in the condensing capacity of the condenser 3 and to further suppress a decrease in the discharge temperature of the compressor 2.

[0053] (Control Configuration of Refrigeration Cycle Apparatus 1) Next, a description will be given of the control configuration of the refrigeration cycle apparatus 1. Fig. 4 is a block diagram showing the control configuration of the refrigeration cycle apparatus 1 according to the first embodiment.

[0054] The control device 50 is configured to include a CPU (Central Processing Unit) 51, memory 52 (ROM (Read Only Memory) and RAM (Random Access Memory)), an input / output buffer (not shown) for inputting and outputting various signals, etc. The CPU 51 deploys a program stored in the ROM into the RAM, etc., and executes it. The program stored in the ROM is a program in which the processing procedures of the control device 50 are written. The control device 50 controls each device in the refrigeration cycle device 1 in accordance with these programs. This control is not limited to processing by software, but can also be processed by dedicated hardware (electronic circuitry).

[0055] The refrigeration cycle apparatus 1 is provided with various sensors capable of detecting conditions such as temperature, pressure, and rotation speed at predetermined locations. Detection signals from these various sensors are input to the control device 50. For example, the detection signals from the intake temperature sensor 81, the discharge temperature sensor 82, and the outlet temperature sensor 83 are input to the control device 50.

[0056] The control device 50 checks the state of the refrigeration cycle device 1 based on detection signals from various sensors, and sends control signals to various devices provided in the refrigeration cycle device 1 to control the various devices. For example, the control device 50 sends a control signal to the compressor 2 to control the rotation speed, etc. of the compressor 2. The control device 50 sends a control signal to the first expansion valve 5 to control the opening degree of the first expansion valve 5. The control device 50 sends a control signal to the second expansion valve 7 to control the opening degree of the second expansion valve 7.

[0057] (Example of Control of Second Expansion Valve 7) Next, a control example will be described in which the control device 50 controls the aperture of the second expansion valve 7 so that the outlet temperature of the second passage 42 of the internal heat exchanger 4 is equal to or higher than a set temperature that suppresses a decrease in the discharge temperature of the compressor 2. As such control examples, a first example and a second example will be described below.

[0058] (First Example of Control of Second Expansion Valve 7) First, a first example of control of the second expansion valve 7 will be described. The control device 50 controls the aperture of the second expansion valve 7 based on the suction temperature of the compressor 2 detected by the suction temperature sensor 81, the discharge temperature of the compressor 2 detected by the discharge temperature sensor 82, and the outlet temperature of the second passage 42 of the internal heat exchanger 4 detected by the outlet temperature sensor 83. Specifically, the control device 50 controls the aperture of the second expansion valve 7 so that the outlet temperature of the second passage 42 of the internal heat exchanger 4 detected by the outlet temperature sensor 83 is equal to or higher than a set temperature that suppresses a decrease in the discharge temperature of the compressor 2.

[0059] The injection port 24 is provided in a portion of the compressor 2 where the refrigerant is compressed to a pressure value where the differential pressure between the suction pressure and the intermediate value of the compressor 2 is less than half the differential pressure between the suction pressure and the discharge pressure of the compressor 2. Therefore, when the outlet temperature of the second passage 42 of the internal heat exchanger 4 becomes equal to or higher than the average value of the suction temperature and the discharge temperature, the temperature of the refrigerant supplied to the injection port 24 becomes higher than the temperature of the refrigerant in the compression chamber that receives the refrigerant. As a result, when the outlet temperature of the second passage 42 of the internal heat exchanger 4 becomes equal to or higher than the average value of the suction temperature and the discharge temperature, a decrease in the discharge temperature of the compressor 2 due to the temperature of the refrigerant supplied to the injection port 24 can be suppressed.

[0060] 5 is a flowchart showing a first example of the opening degree control of the second expansion valve 7 in Embodiment 1. In step S1, the control device 50 acquires data on the suction temperature of the compressor 2 detected by the suction temperature sensor 81, data on the discharge temperature of the compressor 2 detected by the discharge temperature sensor 82, and data on the outlet temperature of the second passage 42 of the internal heat exchanger 4 detected by the outlet temperature sensor 83.

[0061] In step S2, the control device 50 calculates the average value of the suction temperature and the discharge temperature based on the data of the suction temperature of the compressor 2 acquired in step S1 and the data of the discharge temperature of the compressor 2. By calculating the average value of the suction temperature and the discharge temperature in this manner, data of the intermediate value of the temperature between the suction temperature and the discharge temperature of the compressor 2 can be obtained.

[0062] In step S3, the control device 50 compares the data on the outlet temperature of the second passage 42 of the internal heat exchanger 4 obtained in step S1 with the average value of the intake temperature and discharge temperature obtained by the calculation in step S2, and determines whether the outlet temperature of the second passage 42 of the internal heat exchanger 4 is equal to or higher than the average value of the intake temperature and discharge temperature.

[0063] If the outlet temperature of the second passage 42 of the internal heat exchanger 4 is equal to or higher than the average value of the suction temperature and the discharge temperature in step S3, the control device 50 determines that a decrease in the discharge temperature of the compressor 2 can be suppressed, and ends the process. As a result, the aperture of the second expansion valve 7 is maintained at the current aperture.

[0064] On the other hand, if the outlet temperature of the second passage 42 of the internal heat exchanger 4 is not equal to or higher than the average value of the suction temperature and the discharge temperature in step S3, the control device 50 reduces the aperture of the second expansion valve 7 by a predetermined aperture in step S4. The aperture reduced in step S4 is a predetermined aperture that is one unit of the amount of reduction in aperture when the outlet temperature of the second passage 42 of the internal heat exchanger 4 is increased.

[0065] The control device 50 then returns to step S1 when a predetermined time has elapsed since step S4 was executed. The reason for returning to step S1 when a predetermined time has elapsed since step S4 was executed is to wait for the outlet temperature of the second passage 42 of the internal heat exchanger 4 to increase as a result of the opening of the second expansion valve 7 being reduced.

[0066] When returning from step S4 to step S1, new data as described above is acquired in step S1, and it is determined in step S2 whether the outlet temperature of the second passage 42 of the internal heat exchanger 4 is equal to or higher than the average value of the suction temperature and the discharge temperature. Then, in step S3, it is determined again whether the outlet temperature of the second passage 42 of the internal heat exchanger 4 is equal to or higher than the average value of the suction temperature and the discharge temperature. In this case, if the outlet temperature of the second passage 42 of the internal heat exchanger 4 is not equal to or higher than the average value of the suction temperature and the discharge temperature, the processing of step S4 and steps S1 to S3 described above is repeatedly executed until the outlet temperature of the second passage 42 of the internal heat exchanger 4 becomes equal to or higher than the average value of the suction temperature and the discharge temperature.

[0067] By performing the processes of steps S1 to S4, the outlet temperature of the second passage 42 of the internal heat exchanger 4 is controlled to be equal to or higher than the average value of the suction temperature and the discharge temperature. In the compressor 2, the injection port 24 is provided in a portion where the refrigerant is compressed to a pressure value such that the differential pressure between the suction pressure of the compressor 2 and the intermediate value is less than half the differential pressure between the suction pressure and the discharge pressure of the compressor 2. Therefore, when the outlet temperature of the second passage 42 of the internal heat exchanger 4 is equal to or higher than the average value of the suction temperature and the discharge temperature, the temperature of the refrigerant supplied to the injection port 24 becomes higher than the temperature of the refrigerant in the compression chamber that receives the refrigerant. This makes it possible to prevent the discharge temperature of the compressor 2 from decreasing due to the temperature of the refrigerant supplied to the injection port 24.

[0068] Therefore, the average value of the suction temperature and the discharge temperature is considered to be a set temperature that suppresses a decrease in the discharge temperature of the compressor 2.

[0069] As described above, in the first example of control of the second expansion valve 7, the control device 50 controls the opening of the second expansion valve 7 so that the temperature of the refrigerant detected by the outlet temperature sensor 83 is equal to or higher than the set temperature that suppresses a decrease in the discharge temperature of the compressor 2, and therefore becomes higher than the temperature of the refrigerant in the compression chamber that receives that refrigerant. This makes it possible to suppress a decrease in the discharge temperature of the compressor 2 due to the temperature of the refrigerant supplied to the injection port 24.

[0070] (Second Example of Control of Second Expansion Valve 7) Next, a description will be given of a second example of control of the second expansion valve 7. The control device 50 controls the opening degree of the second expansion valve 7 based on the outlet temperature of the second passage 42 of the internal heat exchanger 4 detected by the outlet temperature sensor 83.

[0071] Specifically, the control device 50 controls the opening degree of the second expansion valve 7 so that the outlet temperature of the second passage 42 of the internal heat exchanger 4 detected by the outlet temperature sensor 83 becomes equal to or higher than the theoretical value Td of the discharge temperature of the compression stage in which the injection port 24 is provided when adiabatic compression is performed in multiple stages as shown in the following equation (2).

[0072] In the following equation (2), Ts, Pd, Ps, m, and k are as follows: Ts is the suction temperature of the compressor 2. Pd is the discharge pressure of the compressor 2. Ps is the suction pressure of the compressor 2. m is the number of compression stages of the compressor 2. The number of compression stages is the number of compression stages in a configuration in which the refrigerant is compressed in multiple stages. For example, in a case in which multiple compression chambers are provided as shown in FIG. 2, the number of compression stages is the number of compression stages using the compression chambers when the refrigerant is compressed in stages in the multiple compression chambers. In a configuration in which the refrigerant is compressed in multiple stages, the theoretical value Td of the discharge temperature at each compression stage is calculated using the number of compression stages m corresponding to each compression stage. k is the specific heat ratio.

[0073] Td=Ts×(Pd / Ps) （ｋ－１／ｍｋ） ...(2) In the compressor 2, the injection port 24 is provided in a compression chamber that is compressed to a pressure value such that the differential pressure between the suction pressure of the compressor 2 and the intermediate value is less than half the differential pressure between the suction pressure and the discharge pressure of the compressor 2. Therefore, the outlet temperature of the second passage 42 of the internal heat exchanger 4 is controlled to be equal to or higher than the discharge temperature of the refrigerant at the compression stage corresponding to the compression chamber in which the injection port 24 is provided. As a result, when the outlet temperature of the second passage 42 of the internal heat exchanger 4 becomes equal to or higher than the discharge temperature (refrigerant temperature) at the compression stage in which the injection port 24 is provided, it is possible to prevent the discharge temperature of the compressor 2 from decreasing due to the temperature of the refrigerant supplied to the injection port 24.

[0074] Therefore, the theoretical value Td of the discharge temperature of the compression stage where the injection port 24 is provided is considered to be a set temperature that suppresses a decrease in the discharge temperature of the compressor 2.

[0075] As described above, in the second example of control of the second expansion valve 7, the control device 50 controls the opening of the second expansion valve 7 so that the temperature of the refrigerant detected by the outlet temperature sensor 83 is equal to or higher than the set temperature that suppresses a decrease in the discharge temperature of the compressor 2, and therefore becomes higher than the temperature of the refrigerant in the compression chamber that receives that refrigerant. This makes it possible to suppress a decrease in the discharge temperature of the compressor 2 due to the temperature of the refrigerant supplied to the injection port 24.

[0076] 6 is a flowchart showing a second example of the control of the opening degree of the second expansion valve 7 in Embodiment 1. In step S11, the control device 50 acquires data on the outlet temperature of the second passage 42 of the internal heat exchanger 4 detected by the outlet temperature sensor 83.

[0077] In step S12, the control device 50 reads from the memory 52 the theoretical value Td of the discharge temperature at the compression stage provided with the injection port 24 as described above. The data of the theoretical value Td of the discharge temperature read from the memory 52 in step S12 is calculated in advance based on the values ​​of the suction temperature Ts of the compressor 2, the discharge pressure Pd of the compressor 2, the suction pressure Ps of the compressor 2, and the number of compression stages m of the compressor 2, which were determined in the design stage of the refrigeration cycle apparatus 1, and is stored in the memory 52. ​​In step S12, the data of the theoretical value Td of the discharge temperature stored in the memory 52 in this manner is read.

[0078] In step S13, the control device 50 compares the data on the outlet temperature of the second passage 42 of the internal heat exchanger 4 obtained in step S11 with the data on the theoretical value Td of the discharge temperature read out in step S12, and determines whether the outlet temperature of the second passage 42 of the internal heat exchanger 4 is equal to or higher than the theoretical value Td of the discharge temperature.

[0079] If the outlet temperature of the second passage 42 of the internal heat exchanger 4 is equal to or higher than the theoretical value Td of the discharge temperature in step S13, the control device 50 determines that a decrease in the discharge temperature of the compressor 2 can be suppressed, and ends the process. As a result, the opening degree of the second expansion valve 7 is maintained at the current opening degree.

[0080] On the other hand, if the outlet temperature of the second passage 42 of the internal heat exchanger 4 is not equal to or higher than the theoretical discharge temperature Td in step S13, the control device 50 reduces the aperture of the second expansion valve 7 by a predetermined aperture in step S14. The aperture reduced in step S14 is a predetermined aperture that is one unit of the amount of reduction in aperture when the outlet temperature of the second passage 42 of the internal heat exchanger 4 is increased.

[0081] Then, when a predetermined time has elapsed since the execution of step S14, the control device 50 returns to step S11 and acquires data on the outlet temperature of the second passage 42 of the internal heat exchanger 4 detected by the outlet temperature sensor 83. The reason for acquiring the detected data of the outlet temperature sensor 83d when a predetermined time has elapsed since the execution of step S14 is to wait for the outlet temperature of the second passage 42 of the internal heat exchanger 4 to increase as the opening of the second expansion valve 7 is reduced.

[0082] When returning from step S14 to step S11, the control device 50 acquires new data as described above in step S11 and reads out the theoretical value Td of the discharge temperature in step S12. Then, in step S13, it newly determines whether the outlet temperature of the second passage 42 of the internal heat exchanger 4 is equal to or higher than the theoretical value Td of the discharge temperature. In this case, if the outlet temperature of the second passage 42 of the internal heat exchanger 4 is not equal to or higher than the theoretical value Td of the discharge temperature, the control device 50 repeatedly executes the processing of step S14 and steps S11 to S13 as described above until the outlet temperature of the second passage 42 of the internal heat exchanger 4 becomes equal to or higher than the average value of the compression stage suction temperature and the discharge temperature.

[0083] By executing the processes of steps S11 to S14, the outlet temperature of the second passage 42 of the internal heat exchanger 4 is controlled to be equal to or higher than the theoretical value Td of the discharge temperature. In the compressor 2, the injection port 24 is provided in a portion where the refrigerant is compressed to a pressure value such that the differential pressure between the suction pressure of the compressor 2 and the intermediate value is less than half the differential pressure between the suction pressure and the discharge pressure of the compressor 2. Therefore, when the outlet temperature of the second passage 42 of the internal heat exchanger 4 is equal to or higher than the theoretical value Td of the discharge temperature of the compression stage where the injection port 24 is provided, the temperature of the refrigerant supplied to the injection port 24 becomes higher than the temperature of the refrigerant in the compression chamber that receives that refrigerant. This makes it possible to prevent the discharge temperature of the compressor 2 from decreasing due to the temperature of the refrigerant supplied to the injection port 24.

[0084] Second Embodiment In a second embodiment, a configuration will be described in which a two-stage compressor 20 is used instead of the single-stage compressor 2 shown in the first embodiment.

[0085] (Overall configuration of refrigeration cycle apparatus 1A) Fig. 7 is a diagram showing the overall configuration of a refrigeration cycle apparatus 1A according to embodiment 2. The refrigeration cycle apparatus 1A in Fig. 7 differs from the refrigeration cycle apparatus 1 in Fig. 1 in that a two-stage compressor 20 is provided instead of the single-stage compressor 2.

[0086] The two-stage compressor 20 includes a first compressor 21 on the low stage side and a second compressor 22 on the high stage side, which are connected in series. In the compressor 20, the first compressor 21 sucks in and compresses the refrigerant discharged from the evaporator 6, and discharges it to an intermediate section between the first compressor 21 and the second compressor 22. In the compressor 20, the second compressor 22 sucks in and compresses the refrigerant discharged to the intermediate section, and discharges it toward the condenser 3.

[0087] The compressor 20 is provided with an injection port 24 in a refrigerant path provided in an intermediate portion between the discharge port of the first compressor 21 and the suction port of the second compressor 22. The refrigerant flowing in from the injection port 24 is mixed with the refrigerant discharged from the first compressor 21 and is then drawn into the second compressor 22.

[0088] In the compressor 20, the second compressor 22 has a larger capacity than the first compressor 21. More specifically, the second compressor 22 has a larger displacement than the first compressor 21.

[0089] In compressor 20, an injection port 24 is provided in a portion where the air is compressed to an intermediate value between the suction pressure and the discharge pressure. In compressor 20, since second compressor 22 has a larger capacity than first compressor 21, the intermediate value between the suction pressure and the discharge pressure is set to a pressure value such that the differential pressure between the suction pressure of first compressor 21 in compressor 20 and the intermediate value is less than half the differential pressure between the suction pressure of first compressor 21 in compressor 20 and the discharge pressure of second compressor 22 in compressor 20.

[0090] 3, in the refrigeration cycle apparatus 1A of the second embodiment, the injection port 24 is provided so that the pressure difference B between the suction pressure Ps of the compressor 20 (the suction pressure of the first compressor 21) and the intermediate value Pm is the intermediate value Pm that is less than half (A / 2) of the pressure difference A between the suction pressure Ps of the compressor 20 (the suction pressure of the first compressor 21) and the discharge pressure Pd (the discharge pressure of the second compressor 22). As a result, in the refrigeration cycle apparatus 1A of the second embodiment, when a flammable refrigerant is used, for the same reasons as in the refrigeration cycle apparatus 1 of the first embodiment, it is possible to suppress a decrease in the condensing capacity of the condenser 3 and a decrease in the discharge temperature of the compressor.

[0091] (Control Configuration of Refrigeration Cycle Apparatus 1A) Next, a control configuration of the refrigeration cycle apparatus 1A will be described. Fig. 8 is a block diagram showing the control configuration of the refrigeration cycle apparatus 1A according to the second embodiment.

[0092] The control configuration of the refrigeration cycle apparatus 1A shown in Fig. 7 differs from the control configuration of the refrigeration cycle apparatus 1 shown in Fig. 4 in that a compressor 20 is provided instead of the compressor 2. The first compressor 21 and the second compressor 22 included in the compressor 20 can be individually controlled by the control device 50.

[0093] (Control example of second expansion valve 7) In the refrigeration cycle apparatus 1A, it is possible to execute control similar to the first example of control of the second expansion valve 7 shown in Fig. 5. Furthermore, in the refrigeration cycle apparatus 1A, it is possible to execute control similar to the second example of control of the second expansion valve 7 shown in Fig. 6. By executing such control, in the refrigeration cycle apparatus 1A of embodiment 2, it is possible to suppress a decrease in the discharge temperature of the compressor 20 due to the temperature of the refrigerant supplied to the injection port 24, as in the refrigeration cycle apparatus 1 of embodiment 1.

[0094] Modifications Various modifications of the embodiment will be described below.

[0095] (1) In the first and second embodiments, the refrigeration cycle apparatus 1, 1A is described as an apparatus filled with a flammable refrigerant. As typical examples of the flammable refrigerant, R290 and R600a are described. However, the refrigeration cycle apparatus 1, 1A is not limited to these, and similar effects can be obtained even when other flammable refrigerants are used.

[0096] (2) In the first and second embodiments, scroll-type compressors are shown as representative examples of the compressors 2, 20 used in the refrigeration cycle apparatuses 1, 1A. However, as described above, a compressor other than a scroll-type compressor may be used as a compressor that can obtain the effects described in the first and second embodiments using a flammable refrigerant, as long as the compressor has a structure that allows the pressure at the portion of the compressor where the injection port is provided to be set to an intermediate value that is less than half the differential pressure between the suction pressure and the discharge pressure of the compressor.

[0097] (3) In the first and second embodiments, it has been described that the pressure at the portion of the compressor 2, 20 where the injection port 24 is provided is set to an intermediate value that is less than half the differential pressure between the suction pressure and the discharge pressure of the compressor 2, 20. The intermediate value set in this case may be a value that can ensure a compressor discharge temperature that does not impair the normal function of the condenser 3 in the refrigeration cycle apparatus. Furthermore, in cases where the refrigeration cycle apparatus is used as an apparatus that obtains high-temperature water based on the heat generation amount of the condenser 3, such as a water heater, the intermediate value set in this case may be a value that can ensure a compressor discharge temperature that does not cause problems in the operating state of such an apparatus.

[0098] (4) In the first and second embodiments, the case where a flammable refrigerant is charged into the refrigeration cycle apparatus 1, 1A has been described. To ensure safety, the amount of flammable refrigerant charged into the refrigeration cycle apparatus 1, 1A may differ depending on whether the flammable refrigerant is a highly flammable refrigerant or a flammable refrigerant other than a highly flammable refrigerant. In such a case, the intermediate value of the pressure at the portion where the injection port 24 is provided may be changed depending on the type of refrigerant charged into the refrigeration cycle apparatus 1, 1A, so that the pressure is less than half the differential pressure between the suction pressure and the discharge pressure of the compressor 2, 20.

[0099] (5) In the first and second embodiments, the aperture of the second expansion valve 7 is controlled so that the outlet temperature of the second passage 42 of the internal heat exchanger 4 is equal to or higher than the set temperature that suppresses a decrease in the discharge temperature of the compressor 2, 20. However, this is not limiting, and the aperture of the second expansion valve 7 may not be controlled so that the outlet temperature of the second passage 42 of the internal heat exchanger 4 is equal to or higher than the set temperature that suppresses a decrease in the discharge temperature of the compressor 2. Even if such control is not performed, the aperture of the second expansion valve 7 may not be controlled so that the outlet temperature of the second passage 42 of the internal heat exchanger 4 is equal to or higher than the set temperature that suppresses a decrease in the discharge temperature of the compressor 2. In this case, the pressure of the portion of the compressor 2, 20 where the injection port is provided is set to an intermediate value that is less than half the differential pressure between the suction pressure and the discharge pressure of the compressor 2, 20. This can sufficiently ensure a temperature difference between the first refrigerant passing through the first passage 41 and the second refrigerant passing through the second passage 42 in the internal heat exchanger 4 that promotes evaporation of the second refrigerant through heat exchange.

[0100] (Summary) Hereinafter, the embodiment will be summarized with reference to the drawings again.

[0101] (Section 1) The present disclosure relates to a refrigeration cycle device (refrigeration cycle device 1, 1A) that includes a refrigerant circuit (refrigerant circuit 10) that includes a compressor (compressor 2, 20), a condenser (condenser 3), a first expansion valve (first expansion valve 5), and an evaporator (evaporator 6), and in which a flammable refrigerant is sealed in the refrigerant circuit (refrigerant circuit 10). The refrigeration cycle apparatus (refrigeration cycle apparatus 1, 1A) includes, in the refrigerant circuit (refrigerant circuit 10), a first flow path (first flow path 70) through which refrigerant circulates in the order of the compressor (compressor 2, 20), the condenser (condenser 3), the first expansion valve (first expansion valve 5), and the evaporator (evaporator 6); a second flow path (second flow path 90) that branches off from a branch point (branch point 40) of the first flow path (first flow path 70) between the condenser (condenser 3) and the first expansion valve (first expansion valve 5) and returns the refrigerant that has passed through the condenser (condenser 3) to an injection port (injection port 24) provided in the compressor (compressor 2, 20); and a second expansion valve (second expansion valve 7) and a heat exchanger (internal heat exchanger 4) that are arranged in the second flow path in this order from the branch point (branch point 40). The heat exchanger (internal heat exchanger 4) includes a first passage (first passage 41) provided between the condenser (condenser 3) and the branch point (branch point 40) in the first flow path (first flow path 70), and a second passage (second passage 42) provided between the second expansion valve (second expansion valve 7) and the injection port (injection port 24) in the second flow path (second flow path 90), and a refrigerant flowing through the first passage (first passage 41) and a refrigerant flowing through the second passage (second passage 42) are mixed. The injection port (injection port 24) exchanges heat with the refrigerant flowing through the passage 42, and the injection port (injection port 24) is provided in a portion of the compressor (compressor 2) where the internal pressure is compressed to an intermediate value Pm between the discharge pressure Pd and the suction pressure Ps, and the intermediate value Pm is set to a pressure value (B<A / 2) such that the differential pressure B between the suction pressure Ps and the intermediate value Pm is less than half (A / 2) of the differential pressure A between the suction pressure Ps and the discharge pressure Pd.

[0102] With this configuration, the injection port is located in a portion of the compressor where the internal pressure is compressed to an intermediate value between the discharge pressure and the suction pressure, and this intermediate value is set so that the differential pressure between the suction pressure and the intermediate value is less than half the differential pressure between the suction pressure and the discharge pressure. This reduces the saturation temperature of the refrigerant flowing through the second passage when heat is exchanged in the heat exchanger. This makes it possible to suppress a reduction in the temperature difference between the refrigerant flowing through the first passage and the refrigerant flowing through the second passage in the heat exchanger, thereby promoting heat exchange. Therefore, with this configuration, when a flammable refrigerant is used, a reduction in the heat value of the refrigerant returned from the heat exchanger to the injection port is suppressed, thereby suppressing a reduction in the condensing capacity of the condenser and a reduction in the discharge temperature of the compressor.

[0103] (Item 2) The refrigeration cycle device (refrigeration cycle device 1, 1A) described in item 1 further includes a temperature sensor (outlet temperature sensor 83) that detects the temperature of the refrigerant flowing from the heat exchanger (internal heat exchanger 4) to the injection port (injection port 24), and a control device (control device 50), and the control device (control device 50) controls the opening degree of the second expansion valve (second expansion valve 7) so that the temperature of the refrigerant detected by the temperature sensor (outlet temperature sensor 83) is equal to or higher than a set temperature that suppresses a decrease in the discharge temperature of the compressor (compressor 2, 20) (steps S1 to S4, steps S11 to S14).

[0104] With this configuration, the control device controls the aperture of the second expansion valve so that the refrigerant temperature detected by the temperature sensor is equal to or higher than the set temperature that prevents a decrease in the compressor discharge temperature, and therefore the temperature is higher than the refrigerant temperature in the compression chamber that receives the refrigerant. This further prevents a decrease in the compressor discharge temperature due to the temperature of the refrigerant supplied to the injection port.

[0105] (Item 3) In the refrigeration cycle apparatus (refrigeration cycle apparatus 1, 1A) described in item 1 or 2, the compressor (compressor 2, 20) has a plurality of compression chambers (compression chambers 71a1, 71a2, 71b2, 71b2) therein, and the injection port (injection port 24) is arranged in the compressor (compressor 2, 20) so as to be able to receive refrigerant into the compression chamber in which the internal pressure becomes the intermediate value.

[0106] According to this configuration, in a compressor having multiple compression chambers inside, the injection port is arranged to be able to receive refrigerant into a compression chamber where the internal pressure is at an intermediate value, so that in a compressor having multiple compression chambers inside, it is possible to prevent the discharge temperature of the compressor from decreasing due to the temperature of the refrigerant supplied to the injection port.

[0107] (Item 4) In the refrigeration cycle apparatus (refrigeration cycle apparatus 1A) described in any one of Items 1 to 3, the compressor (compressor 20) includes a first compressor (first compressor 21) and a second compressor (second compressor 22) having a larger capacity than the first compressor (first compressor 21), and is a two-stage compressor (compressor 20) in which a refrigerant is compressed by the first compressor (first compressor 21) and then compressed by the second compressor (second compressor 22), and the injection port (injection port 24) is provided so as to be able to receive a refrigerant in a refrigerant path provided between the first compressor (first compressor 21) and the second compressor (second compressor 22).

[0108] According to this configuration, in a compressor including a first compressor and a second compressor having a larger capacity than the first compressor, an injection port is provided so as to be able to receive refrigerant into a refrigerant path provided between the first compressor and the second compressor, so that in a compressor including the first compressor and the second compressor, it is possible to prevent the discharge temperature of the compressor from decreasing due to the temperature of the refrigerant supplied to the injection port.

[0109] (5) In the refrigeration cycle device (refrigeration cycle device 1, 1A) described in any one of paragraphs 1 to 4, the intermediate value is set to a value in which the internal pressure in the compressor (compressor 2, 20) is smaller than the 0.5 power of the product of the discharge pressure and the suction pressure.

[0110] With this configuration, the intermediate value is set to a value where the internal pressure in the compressor is smaller than the 0.5th power of the product of the discharge pressure and the suction pressure, thereby preventing the discharge temperature of the compressor from decreasing due to the temperature of the refrigerant supplied to the injection port.

[0111] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the description of the above embodiments, and is intended to include all modifications within the meaning and scope of the claims.

[0112] 2, 20 Compressor, 3 Condenser, 5 First expansion valve, 6 Evaporator, 10 Refrigerant circuit, 1, 1A Refrigeration cycle device, 70 First flow path, 40 Branch point, 24 Injection port, 90 Second flow path, 7 Second expansion valve, 4 Internal heat exchanger, 41 First passage, 42 Second passage, 83 Outlet temperature sensor, 50 Control device, 71a1, 71a2, 71b2, 71b2 Compression chamber, 21 First compressor, 22 Second compressor.

Claims

1. A refrigeration cycle device comprising a refrigerant circuit including a compressor, a condenser, a first expansion valve, and an evaporator, with a flammable refrigerant sealed in the refrigerant circuit, wherein the refrigerant circuit comprises: a first flow path in which refrigerant circulates through the compressor, the condenser, the first expansion valve, and the evaporator in that order; a second flow path branching from a branch point of the first flow path between the condenser and the first expansion valve, and returning refrigerant that has passed through the condenser to an injection port provided in the compressor; and a second expansion valve and a heat exchanger disposed in the second flow path in this order from the branch point, wherein the heat exchanger includes: a first passage provided between the condenser and the branch point in the first flow path; and a second passage provided between the second expansion valve and the injection port in the second flow path, and exchanges heat between the refrigerant flowing through the first passage and the refrigerant flowing through the second passage, and the injection port is provided in a portion of the compressor where the internal pressure is compressed to an intermediate value between the discharge pressure and the suction pressure, The intermediate value is set to a pressure value such that the differential pressure between the suction pressure and the intermediate value is less than half the differential pressure between the suction pressure and the discharge pressure.

2. A refrigeration cycle device as described in claim 1, further comprising: a temperature sensor that detects the temperature of the refrigerant flowing from the heat exchanger to the injection port; and a control device, wherein the control device controls the opening of the second expansion valve so that the temperature of the refrigerant detected by the temperature sensor is equal to or higher than a set temperature that suppresses a decrease in the discharge temperature of the compressor.

3. A refrigeration cycle device according to claim 1 or claim 2, wherein the compressor has a plurality of compression chambers therein, and the injection port is provided in the compressor so as to be able to receive refrigerant into the compression chamber in which the internal pressure is at the intermediate value.

4. A refrigeration cycle device according to any one of claims 1 to 3, wherein the compressor is a two-stage compressor including a first compressor and a second compressor having a larger capacity than the first compressor, in which the refrigerant is compressed by the first compressor and then compressed by the second compressor, and the injection port is arranged to be able to receive the refrigerant into a refrigerant path arranged between the first compressor and the second compressor.

5. A refrigeration cycle device according to any one of claims 1 to 4, wherein the intermediate value is set to a value at which the internal pressure in the compressor is smaller than the 0.5 power of the product of the discharge pressure and the suction pressure.

Images