Refrigeration cycle device and refrigeration cycle device control device

Abstract

This refrigeration cycle device comprises a main circuit in which a refrigerant circulates and in which the following are connected in the given order by piping: a compressor that compresses and discharges the refrigerant; an indoor heat exchanger; a primary expansion valve; a power receiver mechanism that has at least a container for storing the refrigerant; a first internal heat exchanger; a secondary expansion valve; and an outdoor heat exchanger. The refrigeration cycle device also comprises: an injection circuit that has an injection / expansion valve and that injects, into the compressor via the injection expansion valve and the first internal heat exchanger, the refrigerant flowing between the power receiver mechanism and the first internal heat exchanger in the main circuit; and a control device that controls the degree of opening of the secondary expansion valve and that of the injection expansion valve. The compressor has an injection flow path that connects the injection circuit to an intermediate pressure unit. The power receiver mechanism has a configuration that combines: a second internal heat exchanger that exchanges heat between the refrigerant flowing between the primary expansion valve and the first internal heat exchanger and the refrigerant suctioned into the compressor; and a gas-liquid separator that is a container. Alternatively, the power receiver mechanism is a power receiver in which a section of piping through which the refrigerant suctioned into the compressor flows is accommodated inside a container. The control device calculates a virtual discharge temperature that has a negative correlation with low pressure that is the pressure on the suction side of the compressor and that has a positive correlation with high pressure that is the pressure on the discharge side of the compressor, and the control device controls the opening degree of the secondary expansion valve and the opening degree of the injection expansion valve so that as the vir

Description

Refrigeration cycle apparatus and control device for refrigeration cycle apparatus

[0001] The present disclosure relates to a refrigeration cycle apparatus having an injection circuit for injecting medium-pressure refrigerant into a compressor, and a control device therefor.

[0002] In a refrigeration cycle apparatus, an outdoor unit having a compressor, an outdoor heat exchanger, and an outdoor expansion valve, and an indoor unit having an indoor heat exchanger and an indoor expansion valve are connected, and an injection circuit having an injection expansion valve is connected to an intermediate pressure portion of the compressor (see, for example, Patent Document 1). In the refrigeration cycle apparatus of Patent Document 1, an intermediate pressure receiver, which is a refrigerant amount regulator, is provided on the side of the indoor expansion valve rather than the branch point with the injection circuit in the main circuit of the refrigerant circuit. Further, in the refrigeration cycle apparatus of Patent Document 1, the injection expansion valve and the outdoor expansion valve are configured to operate in conjunction with each other, and the control device calculates an opening ratio between the outdoor expansion valve and the injection expansion valve based on the suction superheat degree. The opening degree of the injection expansion valve is calculated by multiplying the calculated opening ratio and the opening degree of the outdoor expansion valve.

[0003] Japanese Patent Application Laid-Open No. 2004-324952

[0004] However, in the control for calculating the opening ratio based on the suction superheat degree as in the refrigeration cycle apparatus of Patent Document 1, when an internal heat exchange function with a low-pressure line is added to the intermediate pressure receiver in the refrigerant circuit and an internal heat exchanger for performing heat exchange between the injection circuit and the main circuit is provided, an appropriate opening ratio may not be obtained depending on the operating conditions. Therefore, depending on the operating conditions, the balance of the refrigerant amounts between the refrigerant injected into the compressor via the injection circuit and the refrigerant sucked into the compressor via the downstream side of the main circuit may not be optimal, resulting in a decrease in heating capacity or energy saving performance.

[0005] The present disclosure has been made in view of the above problems, and provides a refrigeration cycle apparatus and a control device for a refrigeration cycle apparatus that can calculate an appropriate opening ratio in a wider operating range than in the past and optimize heating capacity and energy saving performance.

[0006] The refrigeration cycle apparatus according to this disclosure comprises a compressor that compresses and discharges a refrigerant, an indoor heat exchanger, a primary expansion valve, a power receiver mechanism having at least a container for storing the refrigerant, a first internal heat exchanger, a secondary expansion valve, and an outdoor heat exchanger, all connected in order by piping to form a main circuit through which the refrigerant circulates, an injection circuit having an injection expansion valve that injects the refrigerant flowing between the power receiver mechanism and the first internal heat exchanger in the main circuit into the compressor via the injection expansion valve and the first internal heat exchanger, and a control device that controls the opening degrees of the secondary expansion valve and the injection expansion valve, wherein the compressor has an injection passage that connects the injection circuit to an intermediate pressure section. The power receiver mechanism is a mechanism that combines a second internal heat exchanger that performs heat exchange between the refrigerant flowing between the primary expansion valve and the first internal heat exchanger and the refrigerant drawn into the compressor, and a gas-liquid separator which is a container, or a power receiver in which a part of the piping through which the refrigerant drawn into the compressor flows is housed inside the container, and the control device calculates a virtual discharge temperature that has a negative correlation with the low pressure, which is the pressure on the suction side of the compressor, and a positive correlation with the high pressure, which is the pressure on the discharge side of the compressor, and controls the opening of the secondary expansion valve and the opening of the injection expansion valve so that the ratio of the opening of the injection expansion valve to the opening of the secondary expansion valve increases as the operating state with a higher virtual discharge temperature.

[0007] Furthermore, the control device for the refrigeration cycle system according to this disclosure comprises a compressor that compresses and discharges a refrigerant, an indoor heat exchanger, a primary expansion valve, a power receiver mechanism having at least a container for storing the refrigerant, a first internal heat exchanger, a secondary expansion valve, and an outdoor heat exchanger, all connected in order by piping, and an injection circuit having an injection expansion valve, which injects the refrigerant flowing between the power receiver mechanism and the first internal heat exchanger in the main circuit into the compressor via the injection expansion valve and the first internal heat exchanger, the compressor having an injection passage that connects the injection circuit to the intermediate pressure section, and the power receiver mechanism is the primary expansion valve A control device for a refrigeration cycle system, comprising a mechanism combining a second internal heat exchanger that performs heat exchange between the refrigerant flowing between a valve and the first internal heat exchanger and the refrigerant drawn into the compressor, and a gas-liquid separator which is a container, or a power receiver in which a part of the piping through which the refrigerant drawn into the compressor flows is housed inside the container, calculates a virtual discharge temperature that has a negative correlation with the low pressure, which is the pressure on the suction side of the compressor, and a positive correlation with the high pressure, which is the pressure on the discharge side of the compressor, and controls the opening of the secondary expansion valve and the opening of the injection expansion valve such that the ratio of the opening of the injection expansion valve to the opening of the secondary expansion valve increases as the operating state with a higher virtual discharge temperature.

[0008] In this disclosure, the main circuit includes a power receiver mechanism having an internal heat exchange function as a so-called intermediate pressure receiver, and a first internal heat exchanger provided between the power receiver mechanism and the secondary expansion valve, through which the injection circuit passes. The control device calculates a virtual discharge temperature that has a negative correlation with low pressure and a positive correlation with high pressure, and controls the opening so that the ratio of the opening of the injection expansion valve to the opening of the secondary expansion valve increases as the operating condition with a higher virtual discharge temperature. With this configuration, the opening ratio between the secondary expansion valve and the injection expansion valve is determined based on high and low pressure, and the opening ratio is calculated so that the injection amount increases under operating conditions where the discharge temperature tends to be high. Therefore, even with a circuit configuration that includes a power receiver mechanism and a first internal heat exchanger, an appropriate opening ratio can be calculated over a wider operating range than in conventional systems, and heating capacity and energy saving can be optimized.

[0009] This is a schematic diagram showing an example of the configuration of a refrigeration cycle device according to Embodiment 1. This is a schematic diagram showing another example of the configuration of the power receiver mechanism of the refrigeration cycle device shown in Figure 1. This is a functional block diagram showing the functions of the control device according to Embodiment 1. This is a p-h diagram showing the refrigerant state of the refrigeration cycle device shown in Figure 1. This is a block diagram showing an example of the configuration of the part that controls the secondary expansion valve and the injection expansion valve in the control device shown in Figure 1. This is a p-h diagram explaining the virtual discharge temperature calculated by the first function block shown in Figure 5. This is an image diagram showing the processing of the second function block shown in Figure 5. This is a block diagram showing an example of the configuration of the part that controls the secondary expansion valve and the injection expansion valve in the control device according to Embodiment 2. This is a block diagram showing an example of the configuration of the part that controls the secondary expansion valve and the injection expansion valve in the control device according to Embodiment 3.

[0010] The refrigeration cycle device 1 relating to this disclosure will be described below with reference to the drawings. This disclosure is not limited to the following embodiments and can be modified in various ways without departing from the spirit of this disclosure. Furthermore, this disclosure includes all possible combinations of the configurations shown in each of the following embodiments. In particular, the combinations of components are not limited to the combinations in each embodiment, and components described in one embodiment can be applied to another embodiment. Also, in each drawing, components denoted by the same reference numerals are the same or equivalent, and this is common throughout the entire specification. Note that the relative dimensions or shapes of each component in each drawing may differ from those of the actual components.

[0011] Embodiment 1. <Refrigeration Cycle Device 1> Figure 1 is a schematic diagram showing an example of the configuration of a refrigeration cycle device 1 according to Embodiment 1. In Figure 1, the dashed arrows indicate the direction of refrigerant flow during heating operation. As shown in Figure 1, the refrigeration cycle device 1 has an outdoor unit 1A and an indoor unit 1B connected to the outdoor unit 1A. The refrigeration cycle device 1 has a refrigerant circuit RC through which the refrigerant flows.

[0012] Specifically, the refrigeration cycle system 1 includes a compressor 11, a four-way valve 12, an indoor heat exchanger 13, a power receiver mechanism 15, an internal heat exchanger (hereinafter referred to as the first internal heat exchanger 16), two expansion valves (a primary expansion valve 14 and a secondary expansion valve 17, described later), an outdoor heat exchanger 19, an injection expansion valve 18, and the like. The refrigeration cycle system 1 also includes a control device 2 that controls the operation of the refrigeration cycle system 1. The following explanation will use the case where the refrigeration cycle system 1 is an air conditioning system as an example, but it is not limited to this.

[0013] This disclosure relates particularly to means for optimizing heating capacity at low outside temperatures; therefore, the following description will mainly focus on operation during heating. In other words, the four-way valve 12 may be omitted in the minimum configuration. In the following description, since the operation during heating will be mainly explained, the expansion valve provided on the condenser side of the indoor heat exchanger 13, which is one of the two expansion valves provided between the indoor heat exchanger 13 and the outdoor heat exchanger 19 in the refrigerant circuit RC, is defined as the primary expansion valve 14. The expansion valve provided on the evaporator side of the outdoor heat exchanger 19 is defined as the secondary expansion valve 17.

[0014] A compressor 11 that inhales, compresses, and discharges refrigerant, an indoor heat exchanger 13, a primary expansion valve 14, a power receiver mechanism 15 having at least a container for storing refrigerant, a first internal heat exchanger 16, a secondary expansion valve 17, and an outdoor heat exchanger 19 are connected in order by piping 10 m to form the main refrigerant circuit (hereinafter referred to as the main circuit RCm).

[0015] Hereinafter, among the piping 10 constituting the refrigerant circuit RC, the piping 10m constituting the main circuit RCm, specifically the portion of the piping between the indoor heat exchanger 13 and the outdoor heat exchanger 19, may be referred to as piping 10mm. Furthermore, among the piping 10mm constituting the main circuit RCm, the portion of the piping through which the refrigerant drawn into the compressor 11 flows may be referred to as piping 10ms, and the portion of the piping through which the refrigerant discharged from the compressor 11 flows may be referred to as piping 10md. Additionally, among the piping 10mm between the indoor heat exchanger 13 and the outdoor heat exchanger 19, the portion of the piping between the indoor heat exchanger 13 and the power receiver mechanism 15 may be referred to as piping 10mm1, and the portion of the piping between the power receiver mechanism 15 and the outdoor heat exchanger 19 may be referred to as piping 10mm2. In the configuration example shown in Figure 1, the power receiver mechanism 15 is a power receiver 150 in which a portion of the piping 10ms through which the refrigerant drawn into the compressor 11 flows is housed inside a container.

[0016] The refrigerant circuit RC has the main circuit RCm described above, and an injection circuit RCi that branches off from the downstream side of the power receiver mechanism 15 in the main circuit RCm and is connected to the injection passage 11i of the compressor 11. That is, the injection circuit RCi is a bypass circuit provided to bypass the secondary expansion valve 17 and the outdoor heat exchanger 19 with respect to the main circuit RCm. The injection expansion valve 18, the first internal heat exchanger 16, and the inlet of the injection passage 11i of the compressor 11 are connected in order by piping 10i to form the injection circuit RCi.

[0017] In the following, the branching point between the main circuit RCm and the injection circuit RCi will be referred to as branching point P. Furthermore, the piping 10i constituting the injection circuit RCi within the refrigerant circuit RC may be referred to as the injection piping.

[0018] In the example shown in Figure 1, the outdoor unit 1A includes a compressor 11, a four-way valve 12, a primary expansion valve 14, a power receiver mechanism 15, a first internal heat exchanger 16, a secondary expansion valve 17, an outdoor heat exchanger 19, and an injection expansion valve 18. The injection circuit RCi is located in the outdoor unit 1A. The indoor unit 1B includes an indoor heat exchanger 13. The primary expansion valve 14 may also be located in the indoor unit 1B.

[0019] <Main Circuit RCm> The compressor 11 draws in refrigerant, compresses it to a high temperature and high pressure state, and discharges it. It has a casing as its outer shell, which is provided with an intake port 11s and a discharge port 11d. The compressor 11 is also provided with an injection passage 11i formed as a through-hole in the casing and leading to a compression chamber (not shown). An injection port, which is the opening on the compression chamber side of the injection passage 11i, is provided in the intermediate pressure section of the compressor 11. The capacity of the compressor 11 (i.e., the amount of refrigerant discharged per unit time) can be changed by arbitrarily changing the drive frequency of the compressor 11, for example, by an inverter circuit (not shown).

[0020] The four-way valve 12 switches between cooling and heating, specifically switching between the refrigerant flow path during cooling operation and the refrigerant flow path during heating operation. However, since this explanation mainly deals with the operation during heating, the following explanation assumes that the four-way valve 12 is set to direct the refrigerant discharged from the compressor 11 to flow into the indoor heat exchanger 13. In other words, terms such as "upstream" and "downstream" below refer to the direction of refrigerant flow during heating operation.

[0021] The indoor heat exchanger 13 exchanges heat between the refrigerant and the air. During heating operation, the indoor heat exchanger 13 functions as a condenser. That is, during heating operation, the indoor heat exchanger 13 is connected to the refrigerant discharge side of the compressor 11 via a four-way valve 12, and condenses and liquefies the gaseous refrigerant discharged from the compressor 11, while also heating the air (indoor air). The indoor unit 1B has an indoor fan (not shown), and air is supplied to the indoor heat exchanger 13 by the indoor fan.

[0022] The power receiver 150 is a refrigerant container for storing refrigerant. The power receiver 150 is installed in the piping 10 mm between the indoor heat exchanger 13 and the outdoor heat exchanger 19 in the main circuit RCm, and stores excess liquid refrigerant (liquid refrigerant) during operation. In other words, the power receiver 150 is configured to store the liquid refrigerant that flows out from the indoor heat exchanger 13 during heating operation. Specifically, the power receiver 150 is installed in the piping section between the primary expansion valve 14 and the branching point P in the main circuit RCm.

[0023] Furthermore, the power receiver 150 has the function of exchanging heat with the low-pressure refrigerant drawn into the compressor 11. As described above, the power receiver 150 is configured such that a portion of the piping 10ms on the intake side of the compressor 11 in the main circuit RCm is located inside its container. Therefore, the power receiver 150 also performs heat exchange between the medium-pressure refrigerant in the container that flows in from the indoor heat exchanger 13 via the primary expansion valve 14 and the low-pressure refrigerant drawn into the compressor 11. In other words, the power receiver 150 has an internal heat exchange function and is configured to recover the enthalpy of the refrigerant that has flowed out from the evaporator (outdoor heat exchanger 19). In Figure 1, the U-shaped pipe portion of the piping 10ms between the four-way valve 12 and the intake port 11s of the compressor 11 is housed inside the power receiver 150.

[0024] The power receiver mechanism 15 has a gas-liquid separation function and an internal heat exchange function as described above, and any configuration that can realize these functions does not have to be the power receiver 150 described above. The internal heat exchange function of the power receiver mechanism 15 is the function of exchanging heat between the refrigerant flowing between the primary expansion valve 14 and the first internal heat exchanger 16 and the refrigerant drawn into the compressor 11.

[0025] Figure 2 is a schematic diagram showing another configuration example of the power receiver mechanism 15 of the refrigeration cycle device 1 described in Figure 1. As shown in Figure 2, for example, the power receiver mechanism 15 may be configured by combining a second internal heat exchanger 150b having an internal heat exchange function and a container section 150a having a gas-liquid separation function, such as a gas-liquid separator or a receiver that only allows liquid refrigerant to flow. In this configuration, heat exchange is performed between the medium-pressure refrigerant and the low-pressure refrigerant drawn into the compressor 11 in the second internal heat exchanger 150b, and only liquid refrigerant flows downstream (specifically to the branching point P) by the container section 150a, thus achieving the same functionality as the power receiver 150 described above.

[0026] As shown in Figure 1, the primary expansion valve 14 is installed in the piping 10 mm1 between the indoor heat exchanger 13 and the power receiver mechanism 15 in the main circuit RCm. The primary expansion valve 14 is composed of a variable-opening expansion valve, such as an electronic expansion valve, and adjusts the pressure and flow rate of the refrigerant.

[0027] The secondary expansion valve 17 is installed in the piping 10 mm² between the power receiver mechanism 15 and the outdoor heat exchanger 19 in the main circuit RCm. The secondary expansion valve 17 is composed of a variable-opening expansion valve, such as an electronic expansion valve, and adjusts the pressure and flow rate of the refrigerant.

[0028] The outdoor heat exchanger 19 performs heat exchange between the refrigerant and the air. In heating operation, the outdoor heat exchanger 19 functions as an evaporator. That is, during heating operation, the outdoor heat exchanger 19 is connected to the refrigerant intake side of the compressor 11 via the four-way valve 12, evaporating and vaporizing the refrigerant, and cooling the air (outside air). The outdoor unit 1A has an outdoor fan (not shown), and air is supplied to the outdoor heat exchanger 19 by the outdoor fan.

[0029] <Injection Circuit RCi> The injection expansion valve 18 is installed in the injection piping (piping 10i) in the refrigerant circuit RC. The injection expansion valve 18 is composed of a variable-opening expansion valve, such as an electronic expansion valve, and adjusts the pressure and flow rate of the refrigerant. The injection expansion valve 18 adjusts the amount of refrigerant injected into the intermediate pressure section of the compressor 11.

[0030] The first internal heat exchanger 16 is provided in the piping 10 mm² between the branching point P with the injection circuit RCi and the secondary expansion valve 17 in the main circuit RCm, and is provided downstream of the injection expansion valve 18 in the injection piping (piping 10i). The first internal heat exchanger 16 has two flow paths, one for the injection circuit RCi side and one for the main circuit RCm side. The first internal heat exchanger 16 has a double-pipe structure in which, for example, the refrigerant of the main circuit RCm flows inside the inner pipe, and the refrigerant of the injection circuit RCi flows in the space between the inner pipe and the outer pipe.

[0031] Thus, the injection circuit RCi is connected from the branching point P to the injection flow path 11i of the compressor 11 via the injection expansion valve 18 and the first internal heat exchanger 16. Therefore, when injection is performed during heating operation, a portion of the refrigerant discharged from the power receiver 150 flows to the injection circuit RCi, which is branched from the main circuit RCm, and is depressurized in the injection expansion valve 18. The refrigerant depressurized in the injection expansion valve 18 exchanges heat with the refrigerant in the main circuit RCm in the first internal heat exchanger 16, and is then injected into the intermediate pressure section of the compressor 11.

[0032] <Various Sensors> The refrigeration cycle device 1 also includes, for example, a discharge temperature sensor 51, a high-pressure sensor 52, an intake temperature sensor 55, and a low-pressure sensor 56. The discharge temperature sensor 51 and the high-pressure sensor 52 are each located in the discharge-side piping 10md of the compressor 11. The discharge temperature sensor 51 detects the temperature of the refrigerant discharged from the compressor 11, and the high-pressure sensor 52 detects the pressure of the refrigerant discharged from the compressor 11. The intake temperature sensor 55 and the low-pressure sensor 56 are each located in the suction-side piping 10ms of the compressor 11. The intake temperature sensor 55 detects the temperature of the refrigerant drawn into the compressor 11, and the low-pressure sensor 56 detects the pressure of the refrigerant drawn into the compressor 11.

[0033] It is not necessary to install all of the above sensors; only the necessary sensors should be installed as needed and in sufficient quantities as described below. This may include, for example, using temperature sensors (for example, the indoor heat exchanger temperature sensor 53 and the outdoor heat exchanger temperature sensor 54, described later) that are configured to detect the temperature of the two-phase refrigerant instead of the pressure sensor.

[0034] <Control device 2> The various sensors mentioned above are connected to the control device 2, and measured values ​​such as temperature or pressure are input from the various sensors. In addition, although not shown in the figure, user commands are input to the control device 2 via an operating unit (for example, a remote control). Based on the input data, the control device 2 controls the operation of each component of the refrigeration cycle device 1. The control device 2 controls the operating frequency (rotational speed) of the compressor 11, the switching of the four-way valve 12, the opening degrees of the primary expansion valve 14, secondary expansion valve 17 and injection expansion valve 18, and the rotational speeds of the outdoor fan and indoor fan (not shown).

[0035] As described above, the refrigerant circuit RC of this disclosure has an injection circuit RCi and a power receiver mechanism 15, as well as a primary expansion valve 14 and a secondary expansion valve 17 provided upstream and downstream of them. First, the power receiver mechanism 15, the primary expansion valve 14 and the secondary expansion valve 17 maximize the performance of the compressor 11 and enable improved operating efficiency at ambient temperature through control suitable for the operating frequency of the compressor 11 and the ambient temperature. Furthermore, the combination of this configuration and the injection circuit RCi suppresses the rise in discharge temperature even at low ambient temperatures and ensures the amount of refrigerant circulation, thereby suppressing the decrease in heating capacity and energy efficiency at low ambient temperatures.

[0036] Here, the refrigerant returned to the injection port of the compressor 11 is in a gas-liquid two-phase state. However, when the refrigerant is distributed to the main circuit RCm and the injection circuit RCi, i.e., at the branching point P, it is preferable for the refrigerant to be in a liquid state (liquid refrigerant) for more accurate distribution. In the refrigeration cycle device 1 of this disclosure, the intermediate pressure receiver is a power receiver mechanism 15 with an internal heat exchange function, and the main circuit RCm is provided with a first internal heat exchanger 16 that performs heat exchange with the injection circuit RCi. Therefore, compared to conventional refrigeration cycle devices that do not have these internal heat exchange functions, the refrigeration cycle device 1 of this disclosure can more reliably convert the refrigerant at the branching point P into liquid refrigerant. The ratio of refrigerant distributed to the downstream side of the main circuit RCm and the injection circuit RCi mainly depends on the ratio of the opening degree of the secondary expansion valve 17 to the opening degree of the injection expansion valve 18, and strictly speaking, the pressures before and after also have an influence.

[0037] The following briefly describes the control of the compressor 11, primary expansion valve 14, secondary expansion valve 17, and injection expansion valve 18 during heating operation. Detailed control of the opening degrees of the secondary expansion valve 17 and injection expansion valve 18 will be described later.

[0038] The compressor frequency is controlled to bring a variable primarily related to heating capacity to its target value. For example, if this variable is room temperature and its target value is the set room temperature, the control device 2 controls the compressor 11 so as to increase the compressor frequency when the room temperature is lower than the set room temperature, and decrease the compressor frequency when the room temperature is higher than the set room temperature. Also, for example, if the above variable is high pressure Pd, the control device 2 controls the compressor 11 so as to increase the compressor frequency when the high pressure Pd is lower than its target value, the high pressure target value, and decrease the compressor frequency when the high pressure Pd is higher than the high pressure target value.

[0039] The primary expansion valve 14 is primarily adjusted to control the degree of subcooling at the outlet of the condenser (indoor heat exchanger 13). The control device 2 controls the primary expansion valve 14 so that its opening increases when the degree of subcooling is greater than the target value, and decreases when the degree of subcooling is less than the target value. The degree of subcooling may also be determined by subtracting the value detected by a temperature sensor (not shown) located at the outlet of the condenser from the value obtained by converting the high pressure Pd detected by the high pressure sensor 52 to the saturation temperature (condensation temperature). Alternatively, the degree of subcooling may be determined by subtracting the value detected by a temperature sensor (not shown) located at the outlet of the condenser from the value detected by the indoor heat exchanger temperature sensor 53 (Figure 1) located in the two-phase refrigerant region of the condenser. The target value of the degree of subcooling may be a constant value or a variable value. If the target value for the degree of supercooling is a variable value, the control device 2 adjusts the target value for the degree of supercooling as needed, based on the condensation temperature, the condenser intake air temperature (room temperature), and the compressor frequency, etc., with the aim of maximizing the efficiency of the condenser.

[0040] During heating operation, the secondary expansion valve 17 controls, for example, the superheat level of the refrigerant discharged from the compressor 11 (hereinafter also referred to as the discharge superheat level), as described later, and adjusts its opening to reach a target discharge superheat level. When injection is performed, the secondary expansion valve 17 and the injection expansion valve 18 operate in conjunction, as described later.

[0041] Figure 3 is a functional block diagram showing the functions of the control device 2 according to Embodiment 1. As shown in Figure 3, the control device 2 includes a control processing device 21, a timing device 22, and a storage device 23. The control processing device 21 performs calculations and judgments based on the input data and controls each device such as the secondary expansion valve 17 and the injection expansion valve 18. In Figure 3, for the sake of clarity, only the secondary expansion valve 17 and the injection expansion valve 18 are shown as devices controlled by the control device 2, and other devices such as the compressor 11 and the primary expansion valve 14 are omitted from the illustration.

[0042] The memory device 23 is a device that stores data necessary for the control processing device 21 to perform processes such as calculation and determination. Although not shown, the memory device 23 includes a volatile memory device such as a random access memory (RAM) that can temporarily store data, a hard disk, and a non-volatile auxiliary storage device such as a flash memory that can store data long-term. The timing device 22 is composed of, for example, a timer or the like and performs timing. The timing device 22 is used for the determination of the control processing device 21 and the like.

[0043] The control processing device 21 can be composed of, for example, a microcomputer having a control arithmetic processing device such as a CPU (Central Processing Unit). The memory device 23 has data in which the processing procedure performed by the control processing device 21 is made into a program. The control arithmetic processing device executes processing based on the program data to realize control. Each device can be composed of dedicated equipment (hardware).

[0044] FIG. 4 is a p-h diagram showing the refrigerant state of the refrigeration cycle device 1 described in FIG. 1. The horizontal axis represents the specific enthalpy [kJ / kg], and the vertical axis represents the pressure [MPaA]. The points Sa, Sb, Sc, and Sd on the p-h diagram represent the states of the refrigerant in the intermediate pressure part of the compressor 11, the refrigerant injected from the injection circuit RCi to the intermediate pressure part, the refrigerant in which the refrigerant in the intermediate pressure part and the injection refrigerant merge, and the refrigerant discharged from the compressor 11, respectively.

[0045] Hereinafter, the operation of the refrigeration cycle device 1 during heating operation when injection is performed will be described with reference to FIGS. 1 and 4. Also, the opening control of the secondary expansion valve 17 and the injection expansion valve 18 at that time and the configuration for performing the control will be described in detail based on FIG. 5 described later.

[0046] <Operation of Refrigeration Cycle Device 1> As shown in FIGS. 1 and 4, the gaseous refrigerant that has become high-temperature and high-pressure by being compressed by the compressor 11 is discharged from the discharge port 11d of the compressor 11 and flows into the four-way valve 12. In the heating operation, the gaseous refrigerant passes through the four-way valve 12 and flows into the indoor heat exchanger 13. The gaseous refrigerant that has flowed into the indoor heat exchanger 13 radiates heat in the indoor heat exchanger 13 and liquefies under high pressure, and then flows out from the indoor heat exchanger 13. The refrigerant that has flowed out from the indoor heat exchanger 13 is decompressed by the first expansion valve 14 and becomes a medium-temperature and medium-pressure two-phase state, and then flows into the power receiver 150. In the power receiver 150, the refrigerant in the two-phase state that has flowed in radiates heat by heat exchange with the low-pressure line, that is, the pipe 10ms, and the low-pressure refrigerant flowing in the pipe 10ms. In the power receiver 150, the refrigerant in the two-phase state is separated into a gas phase and a liquid phase, and the liquid-phase refrigerant is discharged from the power receiver 150.

[0047] The liquid-phase refrigerant (liquid refrigerant) discharged from the power receiver 150 branches into two flows. One of the branched flows remains at a medium temperature, and the other flows into the injection circuit RCi, is decompressed by the injection expansion valve 18, and then flows into each flow path of the first internal heat exchanger 16 and exchanges heat with each other.

[0048] The refrigerant that has been decompressed by the injection expansion valve 18 and flows into the first internal heat exchanger 16 and exchanges heat in the first internal heat exchanger 16 becomes a medium-pressure (in FIG. 4 described later, medium pressure Pm1) gas-liquid two-phase refrigerant and flows into the intermediate pressure portion of the compressor 11.

[0049] On the other hand, the refrigerant that has flowed into the first internal heat exchanger 16 at a medium temperature in the main circuit RCm and exchanges heat is then decompressed by the second expansion valve 17 and becomes a low-temperature two-phase state, and then flows into the outdoor heat exchanger 19. The low-temperature two-phase state refrigerant that has flowed into the outdoor heat exchanger 19 absorbs heat in the outdoor heat exchanger 19 and vaporizes under low pressure, and then flows out from the outdoor heat exchanger 19. The refrigerant that has flowed out from the outdoor heat exchanger 19 flows through the suction-side pipe 10ms via the four-way valve 12, and absorbs heat in the power receiver mechanism 15 during the flow through the pipe 10ms. The refrigerant that has absorbed heat in the power receiver mechanism 15 is sucked into the compressor 11 and compressed again.

[0050] During the compression process, the enthalpy decreases at the intermediate pressure due to the injectable refrigerant flowing into the intermediate pressure section via the injection circuit RCi, after which the compression process resumes.

[0051] By repeating the above operations, the refrigeration cycle of the refrigeration cycle device 1 is realized.

[0052] In Figure 4, the pressure of the refrigerant discharged from the compressor 11 is high pressure Pd, the pressure of the refrigerant after being reduced by the primary expansion valve 14 is medium pressure Pm, and the pressure of the refrigerant after being reduced by the secondary expansion valve 17 is low pressure Ps. Also in Figure 4, the pressure of the refrigerant after being reduced by the injection expansion valve 18 is medium pressure Pm1, which is lower than medium pressure Pm.

[0053] The refrigerant circuit RC shown in Figure 1 is an example configuration for realizing the refrigeration cycle according to this disclosure, and may not include the primary expansion valve 14 and the four-way valve 12. Also, the condenser and evaporator, i.e., the indoor heat exchanger 13 and the outdoor heat exchanger 19, do not necessarily exchange heat between the refrigerant and air; for example, they may exchange heat between the refrigerant and water. Furthermore, as described above, the power receiver mechanism 15 of the refrigerant circuit RC does not necessarily have to be the power receiver 150 described above, and the function of the power receiver mechanism 15 may be replaced by combining the second internal heat exchanger 150b and the container section 150a for discharging liquid refrigerant.

[0054] Here, we will provide a supplementary explanation of the effectiveness of injection with reference to Figure 4. As shown in the p-h diagram, when the injected refrigerant (see point Sb) flows into the intermediate pressure section (see point Sa) of the compressor 11, the specific enthalpy decreases during the compression process (see point Sc). Therefore, the discharge temperature (see point Sd) can be reduced.

[0055] Normally, during heating operation at low ambient temperatures, the low pressure Ps, i.e., the pressure on the suction side of the compressor 11, decreases, and the discharge temperature becomes very high. If the discharge temperature exceeds a certain threshold, it can cause the compressor 11 to fail. Therefore, in the refrigerant circuit RC, which does not have an injection circuit RCi, the rotation speed of the compressor 11 is limited under low ambient temperature conditions to prevent excessive rise in discharge temperature. However, this reduces the amount of refrigerant circulated and limits the heating capacity.

[0056] In the refrigeration cycle system 1 equipped with the injection circuit RCi, the discharge temperature can be lowered by injection without reducing the rotational speed of the compressor 11. Therefore, even under low ambient temperature conditions, the amount of refrigerant circulated can be ensured while avoiding excessive rise in the discharge temperature. As a result, compared to the case without the injection circuit RCi, a higher heating capacity can be output even at low ambient temperatures.

[0057] Figure 5 is a block diagram showing an example of the configuration of the part of the control device 2 described in Figure 1 that controls the secondary expansion valve 17 and the injection expansion valve 18. The control device 2 includes a main control unit 101, a virtual discharge temperature calculation unit 102, an opening ratio calculation unit 103, and a multiplication unit 104.

[0058] The main control unit 101, shown in block C, controls the discharge superheat as a control output, for example. In other words, the control output deviation in this case is the discharge superheat deviation. The discharge superheat deviation is the difference between the discharge superheat (described later) and the target discharge superheat.

[0059] In this case, block C is a controller that calculates the opening degree of the secondary expansion valve 17 (hereinafter also referred to as the secondary expansion valve opening degree EV2) to converge the discharge superheat degree to the target discharge superheat degree, and is, for example, a controller that implements PI control. The target discharge superheat degree is given a value in advance, for example, 10 [°C] or 20 [°C]. The discharge superheat degree is calculated, for example, by the following procedure.

[0060] First, the control device 2 detects the high pressure Pd from the high pressure sensor 52 and calculates the saturation temperature at that pressure. Then, the control device 2 calculates the discharge superheating degree by subtracting the saturation temperature at high pressure Pd from the temperature detected by the discharge temperature sensor 51.

[0061] The procedure for calculating the discharge superheat is not limited to this procedure. For example, the saturation temperature at high pressure Pd may be obtained directly from the value detected by the indoor heat exchanger temperature sensor 53 located in the two-phase refrigerant region of the indoor heat exchanger 13, instead of obtaining it by converting the high pressure Pd detected by the high pressure sensor 52 to the saturation temperature.

[0062] Note that the discharge superheat level is just one example of a control target (control output); the control target could also be the discharge temperature or the suction superheat level.

[0063] The procedure for calculating the intake superheat is as follows. First, the control device 2 detects the low pressure Ps from the low pressure sensor 56 and calculates the saturation temperature at that pressure (i.e., the evaporation temperature Te, described later). Then, the control device 2 calculates the intake superheat by subtracting the saturation temperature at the low pressure Ps from the temperature detected by the intake temperature sensor 55. Note that the procedure for calculating the intake superheat is not limited to this procedure. For example, the saturation temperature at the low pressure Ps may be obtained directly from the temperature detected by the outdoor heat exchanger temperature sensor 54 located in the two-phase refrigerant region of the outdoor heat exchanger 19, instead of obtaining it by converting the low pressure Ps detected by the low pressure sensor 56 to the saturation temperature.

[0064] When the discharge temperature or suction superheat is the target of control, the target discharge temperature or target suction superheat, which is the target value of the control, can be set to a predetermined value, just as in the case above where the discharge superheat is the target of control.

[0065] The first function block F1 is a virtual discharge temperature calculation unit 102, which calculates the virtual discharge temperature from high and low pressures. The virtual discharge temperature is calculated by the following equation (1).

[0066]

[0067] Here, Tdimg is the virtual discharge temperature [°C], Te is the evaporation temperature [°C], x is a predetermined assumed value for suction superheat, Pd is the high pressure [MPa], Ps is the low pressure [MPa], and n is the polytropic index of the refrigerant used.

[0068] It should be noted that the formula (1) is not strictly correct; any formula or table that can estimate the discharge temperature when the injection expansion valve 18 is closed in the refrigeration cycle device 1, assuming a predetermined suction superheat, will suffice.

[0069] In other words, any derivation method that results in the virtual discharge temperature Tdimg having a negative correlation with the low pressure Ps and a positive correlation with the high pressure Pd is acceptable. The evaporation temperature Te may be obtained by converting the low pressure Ps detected by the low pressure sensor 56 to the saturation temperature, or alternatively, it may be obtained directly from the temperature detected by the outdoor heat exchanger temperature sensor 54 located in the two-phase refrigerant region of the outdoor heat exchanger 19.

[0070] Here, Te + x in equation (1) is defined as the sum of the evaporation temperature Te and the target intake superheat (assumed intake superheat value x) for efficient operation, and is different from the measured value of the intake temperature sensor 55 which is equivalent to the sum of the evaporation temperature and the current intake superheat. Note that the same values ​​may be used for both. The assumed intake superheat value x may be a constant (e.g., 5 [°C]), or it may be the intake superheat measured during actual operation, or a target intake superheat value desirable for control may be given as the assumed intake superheat value x.

[0071] The second function block F2 is the opening ratio calculation unit 103, which calculates the opening ratio k from the virtual discharge temperature Tdimg using the following equation (2).

[0072]

[0073] Here, a and b are constants. The values ​​of the constants a and b may be calculated by recording the opening ratio of the secondary expansion valve 17 and the injection expansion valve 18 in the operating state in which heating capacity is maximized under several conditions, and then performing regression analysis. Alternatively, the values ​​of the constants a and b may be calculated by desk calculations using simulations based on mathematical models. In Embodiment 1, the opening ratio k represents the ratio of the injection expansion valve opening EVinj to the secondary expansion valve opening EV2.

[0074] Furthermore, a and b may be changed according to the operating conditions. For example, when the control device 2 detects or estimates the convergence value or predicted convergence value of the discharge superheat and intake superheat, if the discharge superheat is greater than expected and the intake superheat is as expected or less, the control device 2 adjusts a and b so that the opening ratio k becomes larger even for the same virtual discharge temperature Tdimg. For example, if the discharge superheat is smaller than expected and the intake superheat is as expected or greater, the control device 2 adjusts a and b so that the opening ratio k becomes smaller even for the same virtual discharge temperature Tdimg. For example, if the discharge superheat is as expected or greater and the intake superheat is smaller than expected, the control device 2 adjusts a and b so that the opening ratio k becomes larger even for the same virtual discharge temperature Tdimg. For example, if the discharge superheat is as expected or greater and the intake superheat is greater than expected, the control device 2 adjusts a and b so that the opening ratio k becomes larger even for the same virtual discharge temperature Tdimg.

[0075] Note that the relationship between the opening ratio k and the virtual discharge temperature Tdimg is not limited to equation (2) above. It is sufficient that the opening ratio k has a positive correlation with the virtual discharge temperature Tdimg, and a configuration in which the opening ratio k can be obtained from a function or table other than equation (2) above is also acceptable.

[0076] The multiplication block M is the multiplication unit 104. The multiplication block M calculates the opening degree of the injection expansion valve 18 (hereinafter also referred to as the injection expansion valve opening degree EVinj) by multiplying the secondary expansion valve opening degree EV2 calculated by block C and the opening degree ratio k calculated by the second function block F2 as shown in the following equation (3).

[0077]

[0078] These calculations, namely the calculations of the secondary expansion valve opening EV2 and the injection expansion valve opening EVinj using the aforementioned block C, first function block F1, second function block F2, and multiplication block M, are performed at predetermined intervals. For example, by performing these calculations at 10-second intervals, the opening ratio k is updated in a timely manner, and the openings of the secondary expansion valve 17 and the injection expansion valve 18 are controlled to respond to changes in environmental conditions.

[0079] Furthermore, if the opening ratio k is 0 or less, injection will not be performed. That is, if the virtual discharge temperature Tdimg falls within the temperature range where injection is unnecessary, the injection expansion valve opening EVinj will be 0. In addition, the control device 2 may have a function to determine whether or not to perform injection by combining algorithms such as setting a threshold for the ambient temperature, performing injection if the ambient temperature is below the threshold, and not performing injection if the ambient temperature is above the threshold.

[0080] Figure 6 is a p-h diagram illustrating the virtual discharge temperature Tdimg calculated by the first function block F1 shown in Figure 5. In the p-h diagram of Figure 6, the refrigerant for the virtual discharge temperature Tdimg calculated by equation (1) is indicated by the white circle point Sdv. That is, the virtual discharge temperature Tdimg is the discharge temperature that would be achieved if injection were not performed, assuming the high and low pressures and predetermined intake superheat at that time during injection operation.

[0081] Figure 7 is an illustrative diagram showing the processing of the second function block F2 described in Figure 5. As shown in Figure 7, the design is such that the opening ratio k increases as the virtual discharge temperature Tdimg increases, and the injection amount increases. In other words, the secondary expansion valve 17 and the injection expansion valve 18 operate such that the ratio of the injection expansion valve opening EVinj to the secondary expansion valve opening EV2 increases as the operating state with a high virtual discharge temperature Tdimg.

[0082] This trend is consistent with the design, even considering the nature of the circuit design, which ensures heating capacity by injecting under conditions prone to excessive discharge temperature rise. By appropriately designing the constants a and b in equation (2), the injection amount can be controlled to the optimal level over a wide operating range, thereby maintaining appropriate heating capacity and energy efficiency.

[0083] As described above, the refrigeration cycle device 1 according to Embodiment 1 comprises a main circuit RCm, an injection circuit RCi, and a control device 2. The main circuit RCm consists of a compressor 11 that compresses and discharges refrigerant, an indoor heat exchanger 13, a primary expansion valve 14, a power receiver mechanism 15 having at least a container for storing refrigerant, a first internal heat exchanger 16, a secondary expansion valve 17, and an outdoor heat exchanger 19, all connected in order by piping 10m, through which the refrigerant circulates. The injection circuit RCi has an injection expansion valve 18, and injects the refrigerant flowing between the power receiver mechanism 15 and the first internal heat exchanger 16 in the main circuit RCm into the compressor 11 via the injection expansion valve 18 and the first internal heat exchanger 16. The control device 2 controls the opening degrees of the secondary expansion valve 17 and the injection expansion valve 18. The compressor 11 has an injection channel 11i connected to an injection circuit RCi in the intermediate pressure section. The power receiver mechanism 15 is a mechanism that combines a second internal heat exchanger 150b, which performs heat exchange between the refrigerant flowing between the primary expansion valve 14 and the first internal heat exchanger 16 and the refrigerant drawn into the compressor 11, and a gas-liquid separator (container section 150a) which is a container, or a power receiver 150 in which a part of the piping 10ms through which the refrigerant drawn into the compressor 11 flows is housed inside the container. The control device 2 calculates a virtual discharge temperature Tdimg that has a negative correlation with the low pressure Ps, which is the pressure on the suction side of the compressor 11, and a positive correlation with the high pressure Pd, which is the pressure on the discharge side of the compressor 11. The control device 2 controls the opening of the secondary expansion valve 17 and the opening of the injection expansion valve 18 so that the ratio of the opening of the injection expansion valve 18 to the opening of the secondary expansion valve 17 increases as the operating condition with a high virtual discharge temperature Tdimg.

[0084] In this way, the control device 2 calculates a virtual discharge temperature Tdimg that has a negative correlation with the low pressure Ps and a positive correlation with the high pressure Pd, and controls the opening so that the ratio of the opening of the injection expansion valve 18 to the opening of the secondary expansion valve 17 increases as the operating condition with a higher virtual discharge temperature Tdimg. With this configuration, the opening ratio k of the secondary expansion valve 17 and the injection expansion valve 18 is determined based on high and low pressure, and the opening ratio k is calculated so that the injection amount increases under operating conditions where the discharge temperature tends to be high (for example, low ambient temperature conditions). Therefore, even with a circuit configuration having a power receiver mechanism 15 and a first internal heat exchanger 16, an appropriate opening ratio k can be calculated over a wider operating range than in the conventional method, and the optimal amount of injection can be performed, thereby optimizing heating capacity and energy saving. Furthermore, the power receiver mechanism 15 with an internal heat exchange function and the first internal heat exchanger 16 allow the refrigerant to be injected into the compressor 11 in a two-phase state, while at the branching point P, the refrigerant is distributed in a sufficiently liquefied state, thus enabling precise control of the injection amount.

[0085] Furthermore, the control device 2 calculates the opening ratio k, which is the ratio of the opening degree of the injection expansion valve 18 to the opening degree of the secondary expansion valve 17, using a function or table in which the opening ratio k has a positive correlation with the virtual discharge temperature Tdimg, and controls the opening degrees of the secondary expansion valve 17 and the injection expansion valve 18 based on the calculated opening ratio k.

[0086] In this case, the control device 2 may have a configuration comprising a virtual discharge temperature calculation unit 102 that calculates a virtual discharge temperature Tdimg, a main control unit 101, and a multiplication unit 104. The main control unit 101 calculates the opening degree of the secondary expansion valve 17 to control the discharge superheating degree, discharge temperature, or suction superheating degree to a target value. The multiplication unit 104 calculates the opening degree of the injection expansion valve 18 by multiplying the opening degree of the secondary expansion valve 17 calculated by the main control unit 101 by the calculated opening degree ratio k.

[0087] With this configuration, the main control unit 101 that calculates the opening degree of the secondary expansion valve 17 can be configured with a controller (block C) that implements PI control, and the multiplication unit 104 that calculates the opening degree of the injection expansion valve 18 can be configured with a multiplication block (multiplication block M). Therefore, opening degree control can be realized using existing controllers that perform simple calculations, eliminating the need to create complex programs.

[0088] Furthermore, the virtual discharge temperature Tdimg can be defined as the discharge temperature that would be achieved if the refrigerant were not injected, assuming the low pressure Ps, high pressure Pd, and predetermined suction superheat level at the time of injection when the refrigerant is injected into the compressor 11 via the injection circuit RCi.

[0089] Furthermore, the control device 2 for the refrigeration cycle device 1 according to Embodiment 1 is a control device 2 for the refrigeration cycle device 1 equipped with a main circuit RCm and an injection circuit RCi. The main circuit RCm is connected in order by piping 10m to a compressor 11 that compresses and discharges refrigerant, an indoor heat exchanger 13, a primary expansion valve 14, a power receiver mechanism 15 having at least a container for storing refrigerant, a first internal heat exchanger 16, a secondary expansion valve 17, and an outdoor heat exchanger 19, and the refrigerant circulates. The injection circuit RCi has an injection expansion valve 18 and injects the refrigerant flowing between the power receiver mechanism 15 and the first internal heat exchanger 16 in the main circuit RCm into the compressor 11 via the injection expansion valve 18 and the first internal heat exchanger 16. The compressor 11 has an injection passage 11i that connects the injection circuit RCi to the intermediate pressure section. The power receiver mechanism 15 is a mechanism that combines a second internal heat exchanger 150b, which performs heat exchange between the refrigerant flowing between the primary expansion valve 14 and the first internal heat exchanger 16 and the refrigerant drawn into the compressor 11, and a gas-liquid separator (container section 150a), which is a container, or a power receiver 150 in which a part of the piping 10ms through which the refrigerant drawn into the compressor 11 flows is housed inside the container. The control device 2 of the refrigeration cycle device 1 calculates a virtual discharge temperature Tdimg that has a negative correlation with the low pressure Ps on the suction side of the compressor 11 and a positive correlation with the high pressure Pd on the discharge side of the compressor 11, and controls the opening of the secondary expansion valve 17 and the opening of the injection expansion valve 18 so that the ratio of the opening of the injection expansion valve 18 to the opening of the secondary expansion valve 17 increases as the operating state becomes higher for the virtual discharge temperature Tdimg.

[0090] In this way, the control device 2 of the refrigeration cycle device 1 calculates a virtual discharge temperature Tdimg that has a negative correlation with the low pressure Ps and a positive correlation with the high pressure Pd, and controls the opening so that the ratio of the opening of the injection expansion valve 18 to the opening of the secondary expansion valve 17 increases as the operating condition with a higher virtual discharge temperature Tdimg. With this configuration, the opening ratio k of the secondary expansion valve 17 and the injection expansion valve 18 is determined based on high and low pressure, and the opening ratio k is calculated so that the injection amount increases under operating conditions where the discharge temperature tends to be high (for example, low ambient temperature conditions). Therefore, even when applied to a refrigeration cycle device 1 having a power receiver mechanism 15 and a first internal heat exchanger 16, an appropriate opening ratio k can be calculated over a wider operating range than with conventional control. Thus, the heating capacity and energy saving of the refrigeration cycle device 1 controlled by the control device 2 can be optimized over a wider operating range.

[0091] Embodiment 2. Figure 8 is a block diagram showing an example of the configuration of the part of the control device 2 according to Embodiment 2 that controls the secondary expansion valve 17 and the injection expansion valve 18. As shown in Figure 8, in this embodiment, the main control unit 101 outputs the total opening degree EVt instead of the secondary expansion valve opening degree EV2. The control device 2 is configured to distribute the total opening degree EVt to the secondary expansion valve opening degree EV2 and the injection expansion valve opening degree EVinj based on the opening degree ratio k output from the opening degree ratio calculation unit 103. In this embodiment, the other configurations are the same as in Embodiment 1, so their explanation is omitted.

[0092] As shown in Figure 8, the control device 2 includes a main control unit 101, a virtual discharge temperature calculation unit 102, an opening ratio calculation unit 103, and a distribution unit 201.

[0093] Block C is the main control unit 101. Unlike Embodiment 1, the numerical value it outputs represents the total opening degree EVt, but its calculation method is the same as in Embodiment 1, and for example, PI control is implemented. In other words, when the control output is the discharge superheat degree, Block C is a controller that calculates the total opening degree EVt necessary to converge the discharge superheat degree to the target discharge superheat degree.

[0094] Block D is the distribution unit 201, and the secondary expansion valve opening EV2 and the injection expansion valve opening EVinj are calculated from the total opening EVt output by block C and the opening ratio k output by the second function block F2 using the following equations (4) and (5).

[0095]

[0096]

[0097] From equations (4) and (5) above, it is clear that EV2 + EVinj = EVt, and the sum of the openings of the secondary expansion valve 17 and the injection expansion valve 18 is equal to the total opening EVt. Also, from equations (4) and (5) above, it is clear that EVinj / EV2 = k, and the ratio of the openings of the secondary expansion valve 17 and the injection expansion valve 18 is equal to the opening ratio k.

[0098] In Embodiment 2, as in Embodiment 1, the control output (control target) of the main control unit 101 does not necessarily have to be the discharge superheat level, but may be the discharge temperature or the suction superheat level.

[0099] As described above, the refrigeration cycle device 1 according to Embodiment 2 is equipped with a refrigerant circuit RC similar to that of Embodiment 1, and the control device 2 calculates a virtual discharge temperature Tdimg that has a negative correlation with the low pressure Ps and a positive correlation with the high pressure Pd, similar to Embodiment 1, and controls the opening so that the ratio of the opening degree of the injection expansion valve 18 to the opening degree of the secondary expansion valve 17 increases as the operating state of this virtual discharge temperature Tdimg increases. Therefore, the refrigeration cycle device 1 according to Embodiment 2 also provides the same effect as Embodiment 1 in optimizing heating capacity and energy saving over a wider operating range.

[0100] Furthermore, the control device 2 calculates the opening ratio k, which is the ratio of the opening degree of the injection expansion valve 18 to the opening degree of the secondary expansion valve 17, using a function or table in which the opening ratio k has a positive correlation with the virtual discharge temperature Tdimg, and controls the opening degrees of the secondary expansion valve 17 and the injection expansion valve 18 based on the calculated opening ratio k.

[0101] In the second embodiment, the control device 2 may have a configuration comprising a virtual discharge temperature calculation unit 102 that calculates a virtual discharge temperature Tdimg, a main control unit 101, and a distribution unit 201. The main control unit 101 calculates the total opening degree EVt to control the discharge superheat degree, discharge temperature, or suction superheat degree to a target value. Based on the total opening degree EVt calculated by the main control unit 101 and the calculated opening degree ratio k, the distribution unit 201 calculates the opening degree of the secondary expansion valve 17 and the opening degree of the injection expansion valve 18 such that the sum of the opening degrees of the secondary expansion valve 17 and the opening degree of the injection expansion valve 18 equals the total opening degree EVt, and the ratio of the opening degree of the injection expansion valve 18 to the opening degree of the secondary expansion valve 17 equals the calculated opening degree ratio k.

[0102] By calculating the opening degrees of the secondary expansion valve 17 and the injection expansion valve 18 in this way, the sum of the opening degrees (i.e., EV2 + EVinj) becomes equal to the total opening degree EVt. Therefore, when one valve opens, the other valve closes. Consequently, it becomes easier to control the refrigerant flow rate of the entire refrigerant circuit RC, improving transient control performance such as responsiveness and tracking ability.

[0103] Furthermore, the main control unit 101, which calculates the opening degree of the total opening degree EVt, can be configured as a controller (block C) that implements PI control, and the distribution unit 201, which calculates the opening degree of the secondary expansion valve 17 and the opening degree of the injection expansion valve 18 from the total opening degree EVt and the opening degree ratio k, can be configured as a distribution block D. Therefore, opening degree control can be realized using existing controllers that perform simple calculations, eliminating the need to create complex programs.

[0104] Embodiment 3. Figure 9 is a block diagram showing an example of the configuration of the part of the control device 2 according to Embodiment 3 that controls the secondary expansion valve 17 and the injection expansion valve 18. The following describes a configuration that differs from Embodiment 1.

[0105] As shown in Figure 9, in this embodiment, the main control unit 101 outputs the injection expansion valve opening EVinj instead of the secondary expansion valve opening EV2. Block C, which is the main control unit 101, is a controller that calculates the injection expansion valve opening EVinj to converge the discharge superheat, which is the control output, to its target value, the target discharge superheat, and implements, for example, PI control.

[0106] The second function block F2, which is the opening ratio calculation unit 103, calculates the opening ratio k from the virtual discharge temperature Tdimg calculated by the first function block F1. In Embodiment 1, the opening ratio k represented the ratio of the injection expansion valve opening EVinj to the secondary expansion valve opening EV2, but in Embodiment 3, the opening ratio k represents the ratio of the secondary expansion valve opening EV2 to the injection expansion valve opening EVinj. In this case, in Embodiment 3, the opening ratio k can be replaced with the reciprocal of the opening ratio k in Embodiment 1 (1 / k). That is, in Embodiment 3, the opening ratio k calculated by the second function block F2, which is the opening ratio calculation unit 103, has a negative correlation with the virtual discharge temperature Tdimg.

[0107] The multiplication block M, which is the multiplication unit 104, calculates the secondary expansion valve opening EV2 by multiplying the injection expansion valve opening EVinj calculated by block C by the opening ratio k calculated by the second function block F2.

[0108] In Embodiment 3, as in Embodiments 1 and 2, the control target of the main control unit 101 may be the discharge superheat level, the discharge temperature, or the suction superheat level.

[0109] As described above, the refrigeration cycle device 1 according to Embodiment 3 is equipped with a refrigerant circuit RC similar to that of Embodiment 1, and the control device 2 calculates a virtual discharge temperature Tdimg that has a negative correlation with the low pressure Ps and a positive correlation with the high pressure Pd, similar to Embodiment 1, and controls the opening so that the ratio of the opening degree of the injection expansion valve 18 to the opening degree of the secondary expansion valve 17 increases as the operating state of this virtual discharge temperature Tdimg increases. Therefore, the refrigeration cycle device 1 according to Embodiment 3 also provides the same effect as Embodiment 1 in optimizing heating capacity and energy saving over a wider operating range.

[0110] Furthermore, in Embodiment 3, the control device 2 calculates the opening ratio k, which is the ratio of the opening degree of the secondary expansion valve 17 to the opening degree of the injection expansion valve 18, using a function or table in which the opening ratio k has a negative correlation with the virtual discharge temperature Tdimg, and controls the opening degree of the secondary expansion valve 17 and the opening degree of the injection expansion valve 18 based on the calculated opening ratio k.

[0111] In this case, the control device 2 may have a configuration comprising a virtual discharge temperature calculation unit 102 that calculates a virtual discharge temperature Tdimg, a main control unit 101, and a multiplication unit 104. The main control unit 101 calculates the opening degree of the injection expansion valve 18 to control the discharge superheating degree, discharge temperature, or intake superheating degree to a target value. The multiplication unit 104 calculates the opening degree of the secondary expansion valve 17 by multiplying the opening degree of the injection expansion valve 18 calculated by the main control unit 101 by the calculated opening degree ratio k.

[0112] With this configuration, the main control unit 101 that calculates the opening degree of the injection expansion valve 18 can be configured with a controller (block C) that implements PI control, and the multiplication unit 104 that calculates the opening degree of the secondary expansion valve 17 can be configured with a multiplication block (multiplication block M). Therefore, opening degree control can be realized using existing controllers that perform simple calculations, eliminating the need to create complex programs.

[0113] 1 Refrigeration cycle unit, 1A Outdoor unit, 1B Indoor unit, 2 Control device, 10 Piping, 10i Piping, 10m Piping, 10md Piping, 10mm Piping, 10mm1 Piping, 10mm2 Piping, 10ms Piping, 11 Compressor, 11d Discharge port, 11i Injection flow path, 11s Inlet port, 12 Four-way valve, 13 Indoor heat exchanger, 14 Primary expansion valve, 15 Power receiver mechanism, 16 First internal heat exchanger, 17 Secondary expansion valve, 18 Injection expansion valve, 19 Outdoor heat exchanger, 21 Control processing device, 22 Timing device, 23 Memory device, 51 Discharge temperature sensor, 52 High pressure sensor, 53 Indoor heat exchanger temperature sensor, 54 Outdoor heat exchanger temperature sensor, 55 Inlet temperature sensor, 56 Low pressure sensor, 101 Main control unit, 102 Virtual discharge temperature calculation unit, 103 Opening ratio calculation unit, 104 Multiplication unit, 150 Power receiver, 150a Container unit, 150b Second internal heat exchanger, 201 Distribution unit, C Block, D Block, EV2 Secondary expansion valve opening, EVinj Injection expansion valve opening, EVt Total opening, F1 First function block, F2 Second function block, M Multiplication block, P Branch point, Pd High pressure, Pm Intermediate pressure, Pm1 Intermediate pressure, Ps Low pressure, RC Refrigerant circuit, RCi Injection circuit, RCm Main circuit, Tdimg Virtual discharge temperature, Te Evaporation temperature, a Constant, b Constant, k Opening ratio, x Intake superheat assumption value.

Claims

1. A main circuit through which the refrigerant circulates, comprising: a compressor for compressing and discharging a refrigerant; an indoor heat exchanger; a primary expansion valve; a power receiver mechanism having at least a container for storing the refrigerant; a first internal heat exchanger; a secondary expansion valve; and an outdoor heat exchanger, all connected in order by piping; an injection circuit having an injection expansion valve, which injects the refrigerant flowing between the power receiver mechanism and the first internal heat exchanger in the main circuit into the compressor via the injection expansion valve and the first internal heat exchanger; and a control device for controlling the opening degrees of the secondary expansion valve and the injection expansion valve, wherein the compressor has an injection passage connecting the injection circuit to an intermediate pressure section. The power receiver mechanism is a mechanism that combines a second internal heat exchanger that performs heat exchange between the refrigerant flowing between the primary expansion valve and the first internal heat exchanger and the refrigerant drawn into the compressor, and a gas-liquid separator which is a container, or a power receiver in which a part of the piping through which the refrigerant drawn into the compressor flows is housed inside the container, and the control device calculates a virtual discharge temperature that has a negative correlation with the low pressure, which is the pressure on the suction side of the compressor, and a positive correlation with the high pressure, which is the pressure on the discharge side of the compressor, and controls the opening of the secondary expansion valve and the opening of the injection expansion valve such that the ratio of the opening of the injection expansion valve to the opening of the secondary expansion valve increases as the operating state with a higher virtual discharge temperature.

2. The refrigeration cycle apparatus according to claim 1, wherein the control device calculates the opening ratio, which is the ratio of the opening degree of the injection expansion valve to the opening degree of the secondary expansion valve, using a function or table in which the opening ratio has a positive correlation with the virtual discharge temperature, and controls the opening degree of the secondary expansion valve and the opening degree of the injection expansion valve based on the calculated opening ratio.

3. The refrigeration cycle apparatus according to claim 2, wherein the control device comprises a virtual discharge temperature calculation unit for calculating the virtual discharge temperature, a main control unit, and a multiplication unit, the main control unit calculates the opening degree of the secondary expansion valve for controlling the discharge superheat, discharge temperature, or suction superheat to a target value, and the multiplication unit calculates the opening degree of the injection expansion valve by multiplying the opening degree of the secondary expansion valve calculated by the main control unit by the calculated opening degree ratio.

4. The refrigeration cycle apparatus according to claim 2, wherein the control device comprises a virtual discharge temperature calculation unit for calculating the virtual discharge temperature, a main control unit, and a distribution unit, wherein the main control unit calculates a total opening degree for controlling the discharge superheat degree, discharge temperature, or suction superheat degree to a target value, and the distribution unit calculates the opening degree of the secondary expansion valve and the opening degree of the injection expansion valve based on the total opening degree calculated by the main control unit and the calculated opening degree ratio, such that the sum of the opening degree of the secondary expansion valve and the opening degree of the injection expansion valve equals the total opening degree, and the ratio of the opening degree of the injection expansion valve to the opening degree of the secondary expansion valve equals the calculated opening degree ratio.

5. The refrigeration cycle apparatus according to claim 1, wherein the control device calculates the opening ratio, which is the ratio of the opening degree of the secondary expansion valve to the opening degree of the injection expansion valve, using a function or table in which the opening ratio has a negative correlation with the virtual discharge temperature, and controls the opening degree of the secondary expansion valve and the opening degree of the injection expansion valve based on the calculated opening ratio.

6. The refrigeration cycle apparatus according to claim 5, wherein the control device comprises a virtual discharge temperature calculation unit for calculating the virtual discharge temperature, a main control unit, and a multiplication unit, the main control unit calculates the opening degree of the injection expansion valve for controlling the discharge superheat, discharge temperature, or suction superheat to a target value, and the multiplication unit calculates the opening degree of the secondary expansion valve by multiplying the opening degree of the injection expansion valve calculated by the main control unit by the calculated opening degree ratio.

7. The refrigeration cycle apparatus according to any one of claims 1 to 6, wherein the virtual discharge temperature is the discharge temperature that would be achieved if the refrigerant were not injected, assuming the low pressure, high pressure, and predetermined suction superheat at the time of injection into the compressor via the injection circuit.

8. A main circuit through which the refrigerant circulates, comprising a compressor that compresses and discharges a refrigerant, an indoor heat exchanger, a primary expansion valve, a power receiver mechanism having at least a container for storing the refrigerant, a first internal heat exchanger, a secondary expansion valve, and an outdoor heat exchanger, all connected in order by piping; and an injection circuit having an injection expansion valve, which injects the refrigerant flowing between the power receiver mechanism and the first internal heat exchanger in the main circuit into the compressor via the injection expansion valve and the first internal heat exchanger, wherein the compressor has an injection passage connecting the injection circuit to an intermediate pressure section. The power receiver mechanism is a mechanism that combines a second internal heat exchanger that performs heat exchange between the refrigerant flowing between the primary expansion valve and the first internal heat exchanger and the refrigerant drawn into the compressor, and a gas-liquid separator which is a container, or a power receiver in which a part of the piping through which the refrigerant drawn into the compressor flows is housed inside the container, and the control device for a refrigeration cycle system calculates a virtual discharge temperature that has a negative correlation with the low pressure which is the pressure on the suction side of the compressor and a positive correlation with the high pressure which is the pressure on the discharge side of the compressor, and controls the opening of the secondary expansion valve and the opening of the injection expansion valve such that the ratio of the opening of the injection expansion valve to the opening of the secondary expansion valve increases as the operating state with a higher virtual discharge temperature.

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