Refrigeration Cycle Equipment

Abstract

This ensures the reliability of the compressor when the air conditioner is started up and improves start-up capability. [Solution] The system comprises a refrigerant circuit C in which a compressor 1, a condenser 2, a pressure reducing mechanism 3, and an evaporator 4 are connected in sequence by refrigerant piping, and in which the refrigerant circulates, a condenser fan 21 that sends air to the condenser 2, a condensation temperature detection sensor 22 that detects the condensation temperature of the refrigerant at startup, a condenser intake air temperature detection sensor 23 that detects the temperature of the air sucked into the condenser 2, and a control device 6 that switches between startup control and normal control, wherein the control device 6 performs startup control at startup, and if the startup temperature difference, obtained by subtracting the air temperature detected by the condenser intake air temperature detection sensor 23 from the condensation temperature detected by the condenser temperature detection sensor 22, is greater than a preset temperature difference threshold, the control device 6 terminates the startup control and switches to normal control.

Description

[Technical Field]

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

[0002] In recent years, demand for air conditioners in cold regions has been increasing. Air conditioners used in cold regions are often operated in low outdoor temperatures, especially when heating. Generally, energy efficiency tends to decrease when operating in low outdoor temperatures, but even in such cases, improvements in energy efficiency are required.

[0003] Normally, when an air conditioner starts up (when the compressor starts operating), refrigerant is drawn into the compressor even though no refrigerant is circulating in the refrigerant circuit included in the refrigeration cycle device. Therefore, the amount of refrigerant on the low-pressure side tends to decrease during startup. Furthermore, when used in cold regions or other areas with low outdoor temperatures, not only the compressor but also the refrigerant is cold, so the refrigerant is drawn into the compressor in a condensed state.

[0004] Furthermore, if an air conditioner is stopped for a long period of time at low outdoor temperatures, refrigerant may accumulate in the compressor. When the air conditioner is started under these conditions, the refrigerant is compressed and condensed inside the compressor, resulting in a smaller amount of refrigerant being discharged than when the outdoor temperature is high. As a result, the amount of refrigerant circulating in the refrigeration cycle is insufficient, and the amount of refrigerant drawn into the compressor is also reduced. This may cause the suction pressure of the compressor to fall below the lower limit of its specifications, raising concerns about a decrease in compressor reliability.

[0005] For this reason, the invention disclosed in the following Patent Document 1 allows the refrigerant that has accumulated in the receiver while the air conditioner is stopped to flow into the refrigerant circuit when the air conditioning starts up. In this way, by increasing the amount of refrigerant circulating through the refrigerant circuit when the air conditioning starts up, the above-mentioned inconveniences are eliminated and the reliability of the compressor is ensured. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent Publication No. 2014-119144 Summary of the Invention [Problem to be solved by the invention]

[0007] However, the air conditioner disclosed in the aforementioned Patent Document 1 attempts to solve this problem by increasing the amount of refrigerant circulating within the refrigerant circuit. Therefore, the expansion valve is opened to a large degree, and the timing for ending startup control is set to the timing when the refrigeration cycle stabilizes. Generally, the appropriate opening of the expansion valve is set to, for example, an opening that allows the refrigerant drawn into the compressor to be in a gas phase, which is smaller than the opening during startup control. Therefore, the expansion valve is maintained at an unnecessarily large opening from the time when the suction pressure of the compressor is no longer at a risk of falling below the lower limit of the specifications until the refrigeration cycle stabilizes. This increases the time required to reach the appropriate opening, potentially resulting in a deterioration in startup performance.

[0008] An object of the present invention is to provide a refrigeration cycle device that can ensure the reliability of a compressor when starting an air conditioner and can improve start-up performance. [Means for solving the problem]

[0009] A refrigeration cycle device according to one aspect of the present invention comprises a refrigerant circuit in which a compressor, a condenser, a pressure reduction mechanism, and an evaporator are connected in sequence by refrigerant piping and through which a refrigerant circulates; a condenser fan that sends air to the condenser; a condensation temperature detection sensor that detects the condensation temperature of the refrigerant when the compressor is started; a condenser intake air temperature detection sensor that detects the temperature of the air drawn into the condenser by the condenser fan; and a control device that switches between startup control that controls the opening of the pressure reduction mechanism at the start of the compressor to fix it at a preset startup opening, and normal control that controls the opening of the pressure reduction mechanism to a normal opening depending on the state of the refrigerant circulating through the refrigerant circuit. The control device performs the startup control when the compressor is started, and terminates the startup control and switches to normal control when a startup temperature difference obtained by subtracting the air temperature detected by the condenser intake air temperature detection sensor from the condenser temperature detection sensor is greater than a preset temperature difference threshold. [Effects of the Invention]

[0010] According to the present invention, a refrigeration cycle device is provided that can ensure the reliability of the compressor when starting up an air conditioner and can improve the start-up performance. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a refrigerant circuit diagram of a refrigeration cycle device according to an embodiment of the present invention. [Figure 2] 2A and 2B are graphs showing a schematic representation of the relationship between the pressure reduction mechanism opening and the refrigerant pressure in the refrigerant circuit over time in relation to the control of a conventional refrigeration cycle device, where FIG. 2A shows the relationship between the pressure reduction mechanism opening and time, and FIG. 2B shows the relationship between the refrigerant pressure and time. [Figure 3] 1 is a block diagram showing an internal configuration of a control device for a refrigeration cycle device according to an embodiment of the present invention. [Figure 4]4A and 4B are graphs showing the relationship between the opening of the pressure reducing mechanism and the time of the refrigerant pressure in the refrigerant circuit in relation to the control of the refrigeration cycle device according to an embodiment of the present invention, where FIG. 4A shows the relationship between the opening of the pressure reducing mechanism and time, and FIG. 4B shows the relationship between the refrigerant pressure on the low-pressure side and time. [Figure 5] 5A and 5B are graphs showing the relationship between the opening of the pressure reducing mechanism and the time course of the refrigerant pressure in the refrigerant circuit in relation to the control of a refrigeration cycle device according to an embodiment of the present invention, where FIG. 5A shows the relationship between the opening of the pressure reducing mechanism and time, and FIG. 5B shows the relationship between the low-pressure side refrigerant pressure and time. [Figure 6] 4 is a flowchart showing a basic flow of control of the opening degree of the pressure reducing mechanism at the time of start-up of the refrigeration cycle apparatus according to the embodiment of the present invention. [Figure 7] 4 is a flowchart relating to control of the opening degree of the pressure reducing mechanism at the time of start-up of the refrigeration cycle apparatus according to the embodiment of the present invention. [Figure 8] 4 is a flowchart relating to control of the opening degree of the pressure reducing mechanism at the time of start-up of the refrigeration cycle apparatus according to the embodiment of the present invention. [Figure 9] 4 is a flowchart relating to control of the opening degree of a pressure reducing mechanism in normal control of the refrigeration cycle device according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0012] The structure of a refrigeration cycle apparatus S according to an embodiment of the present invention will be described with reference to Fig. 1. Fig. 1 is a refrigerant circuit diagram of the refrigeration cycle apparatus S according to the embodiment of the present invention. The refrigeration cycle apparatus S according to the embodiment of the present invention shown in Fig. 1 has a refrigerant circuit C in which a compressor 1, an indoor heat exchanger 2, a pressure reducing mechanism 3, and an outdoor heat exchanger 4 are connected in sequence by refrigerant piping, and in which a refrigerant circulates.

[0013] Furthermore, a four-way valve 5 is provided between the compressor 1 and the indoor heat exchanger 2, and between the compressor 1 and the outdoor heat exchanger 4. The four-way valve 5 switches whether the refrigerant discharged from the compressor flows to the indoor heat exchanger 2 side or the outdoor heat exchanger 4 side.

[0014] The compressor 1 draws in the refrigerant circulating through the refrigerant circuit C, compresses it, and discharges it into the refrigerant circuit C. In addition, a discharge temperature detection sensor 11 is provided on the discharge side of the compressor 1 to detect the temperature of the refrigerant discharged from the compressor 1.

[0015] The indoor heat exchanger 2 is disposed inside the indoor unit installed in the indoor space. For example, in heating operation, the indoor heat exchanger 2 exchanges heat between the refrigerant and the air flowing into the indoor unit, and supplies the heated air to the indoor space by absorbing heat from the refrigerant.

[0016] The indoor unit is also provided with an indoor fan 21. The indoor fan 21 takes in indoor air and supplies the air that has undergone heat exchange with the refrigerant into the room. A refrigerant temperature detection sensor 22 is also provided to detect the temperature of the two-phase refrigerant flowing through the indoor heat exchanger 2.

[0017] As the indoor fan 21 rotates in this manner, indoor air is drawn into the indoor unit (indoor heat exchanger 2). In the refrigeration cycle apparatus S according to the embodiment of the present invention, an intake air temperature detection sensor 23 is provided to detect the temperature of the air drawn into the indoor unit.

[0018] In the refrigerant circuit C, a pressure reduction mechanism 3 is provided between the indoor heat exchanger 2 and the outdoor heat exchanger 4. The pressure reduction mechanism 3 is, for example, an expansion valve, and reduces the pressure of the high-pressure refrigerant that has passed through the indoor heat exchanger 2 or the outdoor heat exchanger 4. The pressure reduction mechanism 3 is controlled by a pressure reduction mechanism control unit 65, which will be described later.

[0019] The outdoor heat exchanger 4 is disposed inside an outdoor unit that is installed outdoors. For example, during heating operation, in the outdoor heat exchanger 4, heat is exchanged between the refrigerant and the air (outdoor air) flowing into the outdoor unit, and heat from the outdoor air is absorbed by the refrigerant.

[0020] The outdoor unit is provided with an outdoor fan 41. The outdoor fan 41 takes air into the outdoor unit and expels the air that has exchanged heat with the refrigerant to the outside. The outdoor unit is also provided with a refrigerant temperature detection sensor 42 that detects the temperature of the two-phase refrigerant flowing through the outdoor heat exchanger 4.

[0021] Furthermore, as described above, outdoor air is drawn into the outdoor unit (outdoor heat exchanger 4) by the rotation of outdoor fan 41, and an intake air temperature detection sensor 43 is provided to detect the temperature of the air drawn into the outdoor unit. The temperature of the air drawn into the outdoor unit, acquired by intake air temperature detection sensor 43, is the temperature outdoors where the outdoor unit is installed (outdoor air temperature).

[0022] The flow of refrigerant in the refrigerant circuit C when the refrigeration cycle device S is performing heating operation is as follows. When heating operation is performed, high-temperature, high-pressure gas refrigerant discharged from the compressor 1 flows into the indoor heat exchanger 2 via the four-way valve 5. In the indoor heat exchanger 2, heat is exchanged between the indoor air and the refrigerant, and heated air is supplied to the room. The high-temperature, high-pressure gas refrigerant releases heat through heat exchange as it passes through the indoor heat exchanger 2, and becomes high-pressure liquid refrigerant.

[0023] The high-pressure liquid refrigerant that flows out of the indoor heat exchanger 2 flows into the pressure reduction mechanism 3. The high-pressure liquid refrigerant is reduced in pressure as it passes through the pressure reduction mechanism 3, becoming a low-pressure two-phase refrigerant. The low-pressure two-phase refrigerant that flows out of the pressure reduction mechanism 3 then flows into the outdoor heat exchanger 4. In the outdoor heat exchanger 4, heat is exchanged with the outside air, causing the low-pressure two-phase refrigerant to absorb heat and become a low-pressure gas refrigerant, which is then drawn into the compressor 1 via the four-way valve 5.

[0024] On the other hand, when the refrigeration cycle device S performs cooling operation, the flow of refrigerant in the refrigerant circuit C is as follows: When cooling operation is performed, high-temperature, high-pressure gas refrigerant discharged from the compressor 1 flows into the outdoor heat exchanger 4 via the four-way valve 5. The refrigerant that has flowed into the outdoor heat exchanger 4 exchanges heat with the outside air, dissipating heat and becoming a high-pressure liquid refrigerant.

[0025] The high-pressure liquid refrigerant flowing out from the outdoor heat exchanger 4 flows into the pressure reducing mechanism 3, where it is reduced in pressure and becomes a low-pressure two-phase refrigerant. It then flows into the indoor heat exchanger 2, and exchanges heat with the indoor air as it passes through the indoor heat exchanger 2, causing the low-pressure two-phase refrigerant to absorb heat and become a low-pressure gas refrigerant. The cooled air is then supplied indoors. The low-pressure gas refrigerant flowing out from the indoor heat exchanger 2 is drawn into the compressor 1 via the four-way valve 5.

[0026] Next, the control at the time of startup in the refrigeration cycle apparatus S according to the embodiment of the present invention will be described below. The control content described below can be executed regardless of whether the refrigeration cycle apparatus S is performing heating operation or cooling operation. However, for convenience of explanation, the startup control when the refrigeration cycle apparatus S is performing heating operation will be described as an example.

[0027] The flow of the refrigerant when the refrigeration cycle apparatus S performs heating operation is as described above. During heating operation, the indoor heat exchanger 2 functions as a condenser, while the outdoor heat exchanger 4 functions as an evaporator.

[0028] Therefore, in the following description, the indoor fan 21 provided in the indoor unit will be referred to as the condenser fan 21. Similarly, the refrigerant temperature detection sensor 22 will be referred to as the condensation temperature detection sensor 22. Furthermore, the intake air temperature detection sensor 23 will be referred to as the condenser intake air temperature detection sensor 23.

[0029] As described above, particularly when the refrigeration cycle apparatus S is used in cold regions where the outside air temperature is low, when the operation of the refrigeration cycle apparatus S is started and the compressor 1 is activated, the amount of refrigerant discharged from the compressor 1 decreases. As a result, the amount of refrigerant circulating in the refrigerant circuit C becomes insufficient, and the amount of refrigerant drawn into the compressor 1 also decreases. To solve this problem, in the above-mentioned Patent Document 1, the opening degree of the pressure reducing mechanism 3 is maintained large, and the amount of refrigerant circulating in the refrigerant circuit C is increased.

[0030] However, when such control is performed and the operating mode transitions from startup control to normal control, there is a large discrepancy between the opening degree of the pressure reducing mechanism 3 in startup control and the opening degree of the pressure reducing mechanism 3 in normal control. Therefore, when feedback control in normal control is performed, the opening degree of the pressure reducing mechanism 3 gradually transitions from the opening degree of the pressure reducing mechanism 3 in startup control to the opening degree required in normal control, resulting in poor start-up performance.

[0031] Before describing the startup control in the embodiment of the present invention, the control content in the above-mentioned Patent Document 1 will be described for comparison. Figure 2 is a graph showing the relationship between the opening of the expansion valve (pressure reducing mechanism) and the refrigerant pressure in the refrigerant circuit over time. Figure 2(A) shows the relationship between the pressure reducing mechanism opening and time, and Figure 2(B) shows the relationship between the refrigerant pressure and time.

[0032] In Figure 2(A), the vertical axis represents the opening degree of the pressure reducing mechanism, and the horizontal axis represents time. On the other hand, in Figure 2(B), the vertical axis represents the refrigerant pressure, and the horizontal axis represents time. Note that in both Figures 2(A) and 2(B), the point M where the horizontal axis intersects with the vertical axis represents the start time of the air conditioner (compressor).

[0033] First, we will use Figure 2(B) to explain how the refrigerant pressure changes over time after the air conditioner starts operating. In Figure 2(B), the two-dot chain line shows the change in the high-pressure side refrigerant pressure, and the dashed line shows the change in the low-pressure side refrigerant pressure. When the air conditioner starts operating and the compressor starts, the high-pressure side refrigerant pressure gradually increases and becomes roughly constant at a certain point.

[0034] On the other hand, the refrigerant pressure on the low-pressure side is roughly equal to the refrigerant pressure on the high-pressure side at startup, but drops immediately after startup. This is because, as mentioned above, the amount of refrigerant flowing into the compressor decreases. In Figure 2(B), a dotted line is shown parallel to and close to the horizontal axis, which indicates the passage of time. This dotted line indicates the lower limit of the specified suction pressure of the compressor.

[0035] When the compressor starts, the refrigerant pressure on the low-pressure side drops to near the lower limit of the specifications, then begins to rise and remains roughly constant. After a certain amount of time has passed since the compressor started, both the high-pressure and low-pressure refrigerant pressures are maintained at roughly constant pressures.

[0036] The refrigeration cycle is stable when the refrigerant pressures on the high-pressure side and the low-pressure side are constant. In the above-mentioned Patent Document 1, startup control of the air conditioner is performed until the refrigeration cycle is stabilized, and after the refrigeration cycle is stabilized, the operation mode is switched from startup control to normal control.

[0037] In Figure 2, dotted lines parallel to the vertical axis are shown in both Figure 2(A) and Figure 2(B). These lines indicate the timing at which the operating mode of the air conditioner switches from startup control to normal control. As shown in Figure 2(B), at the timing indicated by the dotted line, both the high-pressure side refrigerant pressure and the low-pressure side refrigerant pressure are approximately constant, so to the right of the dotted line, the refrigeration cycle is in a stable state. Therefore, at the timing indicated by the dotted line, the operating mode switches from startup control to normal control.

[0038] Specifically, in the invention described in Patent Document 1, as shown in Fig. 2(A), the opening of the pressure reducing mechanism is set large during startup control, and after transitioning to normal control, the opening of the pressure reducing mechanism is gradually reduced. However, this type of control has the following problems.

[0039] That is, as indicated by the double-headed arrow denoted by the symbol X, the opening of the pressure reducing mechanism is fixed for a certain period of time after the compressor is started. Therefore, while startup control is being performed, the opening of the pressure reducing mechanism is maintained at a larger value than necessary, which lengthens the time it takes for the opening of the pressure reducing mechanism to reach the appropriate opening. This may result in a deterioration in start-up capability.

[0040] Furthermore, when startup control is terminated and normal control is initiated, feedback control is performed to adjust the discharge temperature to a target temperature, for example, to approach the user-specified air-conditioning operation temperature. The aperture of the pressure-reducing mechanism is controlled based on this feedback control. However, as indicated by the double-headed arrow Y in Figure 2A, there is a large difference between the aperture of the pressure-reducing mechanism during startup control and that during normal control. This is because the appropriate aperture of the pressure-reducing mechanism during normal control is set to, for example, a value that ensures that the refrigerant drawn into the compressor is in a gaseous state, which is smaller than the aperture during startup control. Performing this type of control during normal control increases the enthalpy difference between the evaporator inlet and outlet, thereby increasing air conditioning capacity without unnecessarily increasing the compressor rotation speed, resulting in favorable operation from an energy-saving perspective.

[0041] However, because there is a large difference between the opening degree of the pressure reduction mechanism in startup control and the opening degree of the pressure reduction mechanism in normal control, feedback control takes time to change the opening degree of the pressure reduction mechanism in startup control to the opening degree of the pressure reduction mechanism in normal control, which is required for energy-efficient operation. In other words, when the air conditioner performs heating operation, for example, it takes time for heated air to be supplied to the room, which results in a deterioration in the so-called start-up performance.

[0042] Next, a description will be given of the startup control performed in the embodiment of the present invention. In the embodiment of the present invention, by controlling the refrigeration cycle apparatus S as described below, the startup performance of the compressor 1 at the time of startup of the refrigeration cycle apparatus S is improved while ensuring the reliability of the compressor 1.

[0043] First, we will explain each part of the control device 6. The control device 6 switches between startup control, which controls the opening degree of the pressure reducing mechanism 3 at startup, and normal control, which controls the opening degree of the pressure reducing mechanism 3 after the startup control ends.

[0044] Here, when startup control is executed by the control device 6, the opening degree of the pressure reducing mechanism 3 is fixed to a preset startup opening degree. By fixing the opening degree of the pressure reducing mechanism 3, a large amount of refrigerant is circulated in the refrigerant circuit C when the refrigeration cycle apparatus S is started up.

[0045] In contrast, in normal control, the control device 6 performs feedback control using parameters indicating the state of various refrigerants depending on the state of the refrigerant circulating through the refrigerant circuit C, so that the opening degree of the pressure reducing mechanism 3 becomes the normal opening degree.

[0046] Furthermore, when the opening degree of the pressure reducing mechanism 3 at startup and normal opening is compared, the opening degree at startup is larger than the normal opening degree. That is, the opening degree of the pressure reducing mechanism 3 at normal control is set in consideration of energy saving, and is therefore smaller than the opening degree of the pressure reducing mechanism 3 at startup control.

[0047] Since the opening degree of the pressure reducing mechanism 3 during startup control differs from the opening degree of the pressure reducing mechanism 3 during normal control, the control device 6 controls the opening degree of the pressure reducing mechanism 3 during startup control of the refrigeration cycle device S, when transitioning the operating mode from startup control to normal control, and during normal control.

[0048] The specific control will be described later, but when it is determined that the temperature difference between the condensation temperature detected by the condensation temperature detection sensor 22 and the air temperature detected by the condenser intake air temperature detection sensor 23 (hereinafter, this temperature difference will be referred to as the "start-up temperature difference") is greater than a preset temperature difference threshold, the startup control is terminated and control is switched to normal control.

[0049] 3 is a block diagram showing the internal configuration of the control device 6 of the refrigeration cycle apparatus S according to the embodiment of the present invention. The control device 6 includes an information acquisition unit 61, a calculation unit 62, a comparison unit 63, a storage unit 64, and a pressure reduction mechanism control unit 65.

[0050] In addition, the control device 6 is equipped with various other functions for controlling the refrigeration cycle device S, but below, with regard to the control device 6, only the functions necessary for controlling the operation of the refrigeration cycle device S in this embodiment of the present invention will be explained.

[0051] That is, the control device 6 may have a configuration in which, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and an input / output interface are connected via a bus, which are not shown in Fig. 3. Furthermore, the input / output interface may be connected to the above-mentioned components as well as components such as a display unit, a communication control unit, or an input unit.

[0052] The information acquiring unit 61 acquires information necessary for the control device 6 to perform startup control of the refrigeration cycle apparatus S. Examples of the information acquired by the information acquiring unit 61 include information on the condensation temperature of the refrigerant at the time of startup of the refrigeration cycle apparatus S, which is detected by the condensation temperature detection sensor 22, and information on the temperature of air drawn into the indoor heat exchanger 2 serving as a condenser by the condenser fan 21, which is detected by the condenser intake air temperature detection sensor 23.

[0053] It should be noted that the information acquisition unit 61 may receive information transmitted from the condensation temperature detection sensor 22 or the condenser suction air temperature detection sensor 23 as appropriate. Alternatively, conversely, the information acquisition unit 61 may go to the condensation temperature detection sensor 22 or the condenser suction air temperature detection sensor 23 to acquire information.

[0054] The information acquiring unit 61 acquires the information on the condensation temperature from the condensation temperature detection sensor 22. However, for example, the information on the condensation temperature may be acquired as the condensation temperature information by the discharge temperature detection sensor 11 instead of the condensation temperature detection sensor 22. This is because, when the refrigeration cycle apparatus S is started, the refrigerant discharged from the compressor is in a two-phase state, and therefore the discharge temperature and the condensation temperature are approximately equal.

[0055] The calculation unit 62 calculates a value used to determine whether to shift from startup control to normal control of the refrigeration cycle apparatus S. Specifically, the calculation unit 62 calculates a startup temperature difference obtained by subtracting the air temperature detected by the condenser suction air temperature detection sensor 23 from the condensation temperature detected by the condensation temperature detection sensor 22.

[0056] The comparison unit 63 receives information about the temperature difference at startup, which is calculated by subtracting the air temperature from the condensation temperature calculated by the calculation unit 62, and compares the temperature difference at startup with a preset temperature difference threshold. Therefore, when the comparison unit 63 performs the comparison, it accesses the memory unit 64 to obtain information about the temperature difference threshold.

[0057] The storage unit 64 stores information related to the above-mentioned temperature difference threshold. Here, the "temperature difference threshold" stored in the storage unit 64 is set to a temperature difference at which the refrigerant can condense, such as 0 degrees. In addition, application programs and the like used when the control device 6 controls the refrigeration cycle apparatus S may be stored as appropriate.

[0058] If the comparison unit 63 compares the startup temperature difference with the temperature difference threshold and finds that the startup temperature difference is greater than the temperature difference threshold, the startup control is terminated and the control is switched to normal control. Specifically, the pressure reduction mechanism control unit 65 receives an instruction from the comparison unit 63 to set the opening degree of the pressure reduction mechanism 3 set when the startup control is performed to the opening degree of the pressure reduction mechanism 3 when normal control is performed.

[0059] The pressure reducing mechanism control unit 65 receives an instruction from the comparison unit 63 and controls the degree of opening of the pressure reducing mechanism 3. When controlling the pressure reducing mechanism 3, for example, the control is performed so that the degree of opening becomes a predetermined pulse, or so that the degree of opening becomes a predetermined opening area.

[0060] On the other hand, if the comparison by the comparison unit 63 shows that the temperature difference at startup is less than the temperature difference threshold, the above-mentioned processing is executed again based on the condensation temperature information and air temperature information acquired by the information acquisition unit 61.

[0061] The control by each part of the control device 6 explained above will be explained using graphs as follows. Fig. 4 is a graph that schematically shows the time course of the aperture of the pressure reducing mechanism 3 and the pressure of the refrigerant in the refrigerant circuit C in the control of the refrigeration cycle apparatus S according to an embodiment of the present invention. Fig. 4(A) shows the relationship between the aperture of the pressure reducing mechanism 3 and time, and Fig. 4(B) shows the relationship between the low-pressure side refrigerant pressure and time.

[0062] In the graph shown in Fig. 4, point M, which indicates the position (time) where the vertical axis and the horizontal axis intersect, indicates the timing of starting up the refrigeration cycle apparatus S. In addition, in the graph of Fig. 4, the dotted line (hereinafter referred to as "dotted line O") shown parallel to the opening degree of the pressure reducing mechanism (vertical axis) indicates the timing when the operating mode is switched in the embodiment of the present invention.

[0063] 4(A), immediately after the start-up of the refrigeration cycle apparatus S, the start-up control is executed by the control device 6, and the start-up control is switched to the normal control at the timing indicated by the dotted line O. After that, the normal control is executed.

[0064] The degree of opening of the pressure reducing mechanism 3 during startup control is preset. Therefore, the pressure reducing mechanism control unit 65 controls the pressure reducing mechanism 3 so that the degree of opening of the pressure reducing mechanism 3 during startup control is set to the preset degree. Furthermore, while startup control is being executed, the degree of opening remains fixed and is not changed.

[0065] In this way, during startup control, the opening degree of the pressure reducing mechanism 3 is adjusted to be larger than during normal control. This is because by opening the pressure reducing mechanism 3 to a larger degree, immediately after startup of the refrigeration cycle apparatus S, priority is given to start-up capability over energy saving performance, and a larger amount of refrigerant is circulated through the refrigerant circuit C.

[0066] The reason why the opening degree of the pressure reducing mechanism 3 is fixed during startup control is as follows: As shown in Fig. 2(B), the refrigerant pressure on the high-pressure side and the refrigerant pressure on the low-pressure side do not stabilize (become roughly constant) until a certain time has elapsed after the refrigeration cycle apparatus S is started. Also, it takes longer for the refrigerant pressure on the high-pressure side to stabilize than for the refrigerant pressure on the low-pressure side.

[0067] Furthermore, since feedback control in normal control involves adjusting the aperture of the pressure reducing mechanism 3 as needed so that the discharge temperature reaches a target temperature, for example, such feedback control cannot be performed when the refrigeration cycle is not stable. Therefore, the aperture of the pressure reducing mechanism 3 is fixed and not adjusted while startup control is being executed.

[0068] 4(A) also shows a dotted line indicated by the symbol P (hereinafter referred to as "dotted line P" where appropriate). The dotted line P indicates a change in the opening degree of the pressure reducing mechanism 3 accompanying a switch in the operating mode from startup control to normal control in the technology disclosed in Patent Document 1, which is shown in FIG. 2(A).

[0069] As can be seen from the dotted line P, in the prior art, when the control switches from startup control to normal control, the degree of opening of the pressure reducing mechanism 3 gradually decreases, and after a certain time has passed, the degree of opening of the pressure reducing mechanism 3 reaches the desired degree of opening. This is because, in normal control, feedback control is performed, and the degree of opening of the pressure reducing mechanism 3 does not immediately reach the desired degree of opening.

[0070] In other words, in the prior art, the opening degree of the pressure reducing mechanism 3 switches from startup control to normal control after the refrigeration cycle has stabilized, that is, after both the high-pressure side refrigerant pressure and the low-pressure side refrigerant pressure have reached approximately constant pressures, as shown in Fig. 2. That is, startup control is performed until the refrigeration cycle has stabilized and feedback control (normal control) can be performed, and during that time the opening degree of the pressure reducing mechanism 3 remains largely fixed.

[0071] 4(A) , the boundary where the opening degree of the pressure reducing mechanism 3 changes from a fixed opening degree is the timing at which the operating mode switches from startup control to normal control in the conventional technology. This switching timing is indicated by the dashed line indicated by the symbol Q (hereinafter referred to as "dashed line Q" where appropriate).

[0072] 4(B), which shows the change in refrigerant pressure over time after the start-up of the refrigeration cycle apparatus S in accordance with the embodiment of the present invention, the refrigerant pressure on the low-pressure side first drops to approximately the lower limit of the specifications of the compressor 1 when the refrigeration cycle apparatus S is started up. Thereafter, the refrigerant pressure starts to rise over time, and then stabilizes at a constant pressure. This point has been described with reference to FIG. 2.

[0073] It should be noted that the low-pressure side refrigerant pressure does not necessarily decrease to the lower limit of the specifications of the compressor 1 after startup, and is depicted in this manner merely for the convenience of explaining that the low-pressure side refrigerant pressure decreases immediately after startup of the refrigeration cycle device S (compressor 1). Also, Fig. 4(B) shows only the low-pressure side refrigerant pressure shown in Fig. 2(B), and does not depict the change in the high-pressure side refrigerant pressure.

[0074] That is, at startup, the refrigerant discharged from the compressor 1 is in a two-phase state. Furthermore, if the condensation temperature is lower than the condenser suction air temperature, the refrigerant cannot dissipate heat to the indoor air (for convenience, the temperature of the refrigerant in a heat exchanger that is to function as a condenser even when not condensed will hereinafter be referred to as the "condensation temperature"). Therefore, a low-density two-phase refrigerant flows into the pressure reducing mechanism 3. In this state, the refrigerant does not easily circulate inside the refrigerant circuit C (a state in which the refrigerant pressure on the low-pressure side, which is the pressure on the suction side of the compressor 1, drops).

[0075] Therefore, when the refrigeration cycle apparatus S is in this state, that is, immediately after the start-up of the refrigeration cycle apparatus S, it is necessary to increase the opening degree of the pressure reduction mechanism 3. Such an opening degree of the pressure reduction mechanism 3 is shown in Fig. 4(A), and the opening degree of the pressure reduction mechanism 3 is maintained large from the time of start-up until the dotted line O that separates the start-up control from the normal control.

[0076] On the other hand, if the condensation temperature becomes higher than the condenser intake air temperature, the refrigerant can dissipate heat to the indoor air. Therefore, the refrigerant in a liquid phase with a high density flows into the pressure reducing mechanism 3.

[0077] In this state, the refrigerant is more likely to circulate within the refrigeration cycle (the refrigerant pressure on the low-pressure side, which is the pressure on the suction side of the compressor 1, rises). Therefore, unlike immediately after startup, there is no need to circulate a large amount of refrigerant through the refrigerant circuit C. In this state, the refrigerant drawn into the compressor 1 is a two-phase refrigerant, and it is necessary to prevent damage to the compressor 1 due to the liquid-phase refrigerant being drawn into the compressor 1. Therefore, it is necessary to reduce (throttle) the opening of the pressure reducing mechanism 3 via the pressure reducing mechanism control unit 65.

[0078] Therefore, in the refrigeration cycle apparatus S according to an embodiment of the present invention, the startup temperature difference (condensing temperature minus air temperature) is compared with a temperature difference threshold, and if the startup temperature difference is greater than the temperature difference threshold, the system switches from startup control to normal control. The timing at which the startup temperature difference exceeds the temperature difference threshold is often the timing at which the low-pressure side refrigerant pressure, which had been decreasing immediately after startup, begins to increase (the timing at which the dotted line O intersects with the dashed line representing the low-pressure side refrigerant pressure in FIG. 4(B)). Even if the system switches from startup control to normal control using feedback control after this timing, the low-pressure side pressure is unlikely to decrease.

[0079] By executing such control, the timing of switching from startup control to normal control can be significantly accelerated. That is, the timing of switching from startup control to normal control in the prior art, indicated by the dashed line Q, is shortened to the timing of switching from startup control to normal control in the embodiment of the present invention, indicated by the dotted line O, as indicated by the large arrow indicated by the symbol N.

[0080] The change in the low-pressure side refrigerant pressure after the refrigeration cycle apparatus S starts and the startup control is initiated is as described above. Therefore, in the embodiment of the present invention, the switch from startup control to normal control is performed while the low-pressure side refrigerant pressure is changing. However, as described above, even if the startup control is switched to normal control at such a timing and feedback control is performed in the normal control, the low-pressure side refrigerant pressure will not drop any further and fall below the lower limit of the specifications of the compressor 1.

[0081] 4(A), when startup control is executed, the opening degree of the pressure reducing mechanism 3 is large. In contrast, in normal control, the opening degree of the pressure reducing mechanism 3 is controlled so that the refrigerant drawn into the compressor 1 is not in a two-phase state but in a gas phase state, for example, so that the quality fraction is 1. To perform such control, feedback control is executed as described above.

[0082] By executing feedback control in this manner, the amount of refrigerant circulating in the refrigerant circuit C can be optimized more effectively than startup control, while maintaining a small opening degree of the pressure reduction mechanism 3. Therefore, normal control is more energy-efficient than startup control.

[0083] In the embodiment of the present invention, the control of the aperture of the pressure reducing mechanism 3 when the operating mode is switched from startup control to normal control does not involve immediately controlling the aperture of the pressure reducing mechanism 3 by feedback control in normal control after the operating mode is switched from startup control to normal control. The aperture of the pressure reducing mechanism 3 in startup control is referred to as the "first startup aperture" as appropriate.

[0084] In the refrigeration cycle apparatus S according to the embodiment of the present invention, the opening degree of the pressure reducing mechanism 3 is controlled to follow the change indicated by the solid line in the graph of Fig. 4(A). During this period, from immediately after the start of the compressor 1 until the time indicated by the dotted line O, the opening degree of the pressure reducing mechanism 3 during the start-up control is controlled to be large. This is to allow a larger amount of refrigerant to flow through the refrigerant circuit C, as described above.

[0085] On the other hand, if the opening of the pressure reducing mechanism 3 is too large and the suction side of the compressor 1 enters a two-phase state, the enthalpy difference at the inlet and outlet of the evaporator will decrease, which may reduce the capacity of the refrigeration cycle device S. Therefore, in normal control, feedback control is performed to control the opening of the pressure reducing mechanism 3 so that the suction dryness fraction becomes 1, for example.

[0086] Therefore, the opening degree of the pressure reducing mechanism 3 under normal control is smaller than the first startup opening degree. In Fig. 4(A), the solid line drawn parallel to the horizontal axis, which represents the passage of time, at a position close to the horizontal axis, indicates the opening degree of the pressure reducing mechanism 3 adjusted as a result of feedback control under normal control.

[0087] However, there is a large difference between the first startup opening degree and the opening degree of the pressure reducing mechanism 3 under normal control. Because of this difference, when the opening degree of the pressure reducing mechanism 3 is changed by feedback control as the operating mode switches from startup control to normal control, it takes a long time to reach the opening degree of the pressure reducing mechanism 3 under normal control.

[0088] That is, as described above, in the conventional control of the opening degree of the pressure reducing mechanism 3 shown by the dotted line P in Fig. 4(A), feedback control is executed immediately after switching to normal control. When such control is performed, as shown by the dotted line P, it takes time for the opening degree of the pressure reducing mechanism 3 to change from the first startup opening degree to the desired opening degree under normal control due to the execution of feedback control.

[0089] Therefore, in controlling the opening degree of the pressure reduction mechanism 3 in the embodiment of the present invention, control is performed to reduce the opening degree of the pressure reduction mechanism 3 while adjusting the first startup opening degree to the opening degree of the pressure reduction mechanism 3 in normal control. However, the opening degree of the pressure reduction mechanism 3 is not immediately changed to the opening degree executed by feedback control in normal control, but is controlled to change from the first startup opening degree to an opening degree larger than the opening degree of the pressure reduction mechanism 3 in normal control (hereinafter, this opening degree will be referred to as the "second startup opening degree" as appropriate).

[0090] As described above, Figure 4(A) shows the change in the opening degree of the pressure reducing mechanism 3. Here, when the operating mode is switched from startup control to normal control, the opening degree of the pressure reducing mechanism 3 is controlled to change from a large opening degree to a small opening degree. The dotted line O in Figure 4(A) shows the timing when the operating mode is switched from startup control to normal control, and the solid line indicates the change in the opening degree of the pressure reducing mechanism 3 due to this control. In other words, the opening degree of the pressure reducing mechanism 3 is controlled from a first startup opening degree, which is the opening degree of the pressure reducing mechanism 3 while startup control is being performed immediately after startup of the compressor 1, to a second startup opening degree when switching from startup control to normal control.

[0091] The control for reducing the opening of the pressure reducing mechanism 3 when switching from the startup control to the normal control is performed by, for example, feedforward control rather than feedback control. Then, the opening of the pressure reducing mechanism 3 is gradually controlled to a desired opening from the second startup opening by feedback control.

[0092] By performing such control, the opening degree of the pressure reduction mechanism 3 can be adjusted more quickly from the opening degree of the pressure reduction mechanism 3 in the startup control to the opening degree of the pressure reduction mechanism 3 in the normal control. Therefore, in the normal control, the opening degree of the pressure reduction mechanism 3 can be set to an appropriate opening degree early, and the energy saving performance of the refrigeration cycle apparatus S can be improved.

[0093] In the above-described control, the degree to which the pressure reduction mechanism 3 is reduced from its opening degree during startup control is set in advance, and the pressure reduction mechanism control unit 65 reduces the opening degree of the pressure reduction mechanism 3 to the set opening degree (second startup opening degree).

[0094] That is, the second startup degree of opening is set to the smallest degree of opening that does not cause a new decrease in the refrigerant pressure on the low-pressure side immediately after switching from startup control to normal control. Therefore, if the second startup degree of opening is set to a degree larger than this degree of opening, it will take time to adjust the degree of opening of the pressure reducing mechanism 3 to the appropriate degree for normal control, as described above, which is insufficient from the perspective of improving the energy efficiency of the refrigeration cycle apparatus S. Furthermore, setting the second startup degree of opening to a degree smaller than this degree of opening is not feasible because there is a possibility that the refrigerant pressure on the low-pressure side will fall below the lower limit of the specifications.

[0095] As described above, the opening degree of the pressure reducing mechanism 3 when the startup control is executed can be set as the first startup opening degree. This assumes, for example, a situation in which the refrigeration cycle apparatus S is installed in a cold region or the like and has been stopped for a long time. In such a situation, when the compressor 1 is started after being stopped for a long time, the temperature of the refrigerant has also dropped, making it difficult for the refrigerant to circulate within the refrigerant circuit C. Therefore, the startup control is executed by setting the opening degree of the pressure reducing mechanism 3 to a large value, such as the first startup opening degree.

[0096] In contrast, for example, if the compressor 1 is stopped for a short time and the refrigeration cycle device S (compressor 1) is started again not long after it was stopped last time, the refrigerant tends to circulate within the refrigerant circuit C, so in such a case, there is no need to set the opening of the pressure reducing mechanism 3 to a large opening (first start-up opening) similar to that in the case where the device is started after being stopped for a long period of time as described above.

[0097] 5A and 5B are graphs schematically showing the relationship between the opening degree of the pressure reducing mechanism 3 and the time course of the refrigerant pressure in the refrigerant circuit C in the control of the refrigeration cycle apparatus S according to the embodiment of the present invention. Fig. 5A shows the relationship between the opening degree of the pressure reducing mechanism 3 and time, and Fig. 5B shows the relationship between the low-pressure side refrigerant pressure and time.

[0098] The graph showing the change in low-pressure side refrigerant pressure over time in Figure 5(B) is the same as Figure 4(B). On the other hand, Figure 5(A) is basically the same as Figure 4(A), except that the dotted line P and dashed line Q are not drawn and a solid line R is shown at the second startup opening. The second startup opening indicated by the solid line R is the opening set in startup control when the compressor 1 is stopped for a short time and is immediately started again.

[0099] 4(A), the solid line shows the change in the opening degree of the pressure-reducing mechanism 3 that occurs when the operating mode switches from startup control to normal control in the case where the opening degree of the pressure-reducing mechanism 3 is set to the first startup opening degree at the start of the compressor 1. However, in FIG. 5(A), the change in the opening degree of the pressure-reducing mechanism 3 that was shown by the solid line is shown by a dashed line.

[0100] That is, when the compressor 1 is stopped for a short time and then started again, the refrigerant tends to circulate within the refrigerant circuit C, and in such a case, it is not necessary to increase the opening of the pressure reducing mechanism 3 to the first startup opening. Therefore, in such a case, the opening of the pressure reducing mechanism 3 in the startup control is not set to the first startup opening, but is set to a second startup opening that is smaller than the first startup opening.

[0101] 3, in addition to the above-mentioned components, the control device 6 further includes a determination unit 66, a timing unit 67, and a setting unit 68. That is, the length of time that the compressor 1 is stopped is measured by the timing unit 67. The timing unit 67 starts measuring the time from the point in time that the compressor 1 is stopped, and measures the time until the compressor 1 is started up thereafter.

[0102] The determination unit 66 acquires information regarding the stop time of the compressor 1 measured by the timing unit 67. Then, the determination unit 66 compares the information regarding the stop time of the compressor 1 with the stop time threshold, and if the determination unit 66 determines that the stop time of the compressor 1 is equal to or greater than the stop time threshold, the determination unit 66 instructs the setting unit 68 to set the opening degree of the pressure reducing mechanism 3 to the first start-up opening degree. On the other hand, if the determination unit 66 determines that the stop time of the compressor 1 is less than the stop time threshold, the determination unit 66 instructs the setting unit 68 to set the opening degree of the pressure reducing mechanism 3 to the second start-up opening degree.

[0103] By changing the start-up opening of the pressure reducing mechanism 3 based on the stop time in this way, it is possible to prevent the start-up opening from being set smaller than necessary, causing the suction pressure of the compressor 1 to drop excessively and fall below the specified pressure range.

[0104] It is also possible to prevent the refrigerant drawn into the compressor 1 from becoming wet (liquid refrigerant being drawn in) due to the start-up opening being set larger than necessary. By preventing these situations from occurring, it is possible to ensure the reliability of the compressor 1. Furthermore, by setting the opening of the pressure reducing mechanism 3 to the second start-up opening, it is possible to further improve the start-up capability.

[0105] The above-mentioned stop time threshold, first start opening, and second start opening are stored in advance in the storage unit 64. The stop time threshold is a value obtained, for example, through an experiment, and can be set to, for example, 60 minutes.

[0106] The above describes setting the opening degree of the pressure reducing mechanism 3 during startup control based on the stop time of the compressor 1. However, when setting the opening degree of the pressure reducing mechanism 3 during startup control, the outside air temperature may also be used as the basis, instead of the stop time of the compressor 1.

[0107] That is, the temperature outdoors where the outdoor unit is installed (outdoor air temperature) is detected using the above-mentioned intake air temperature detection sensor 43. The determination unit 66 uses the detected outdoor air temperature to compare it with a preset outdoor air temperature threshold, and if the outdoor air temperature is lower than the outdoor air temperature threshold, for example, sets the opening degree of the pressure reducing mechanism 3 to the first startup opening degree.

[0108] This is because the lower the outside air temperature, the lower the refrigerant temperature, and so when the suction pressure of the refrigerant into the compressor 1 drops to the saturation pressure of the outside air temperature, the amount of refrigerant circulating in the refrigerant circuit C decreases. Also, when the outside air temperature is low, the refrigerant is more likely to stagnate in the compressor 1, which is known as stagnation.

[0109] On the other hand, when the outside air temperature is equal to or higher than the outside air temperature threshold, the refrigerant temperature is relatively high and the refrigerant easily circulates in the refrigerant circuit C. In such a case, the opening degree of the pressure reducing mechanism 3 is set to, for example, the second startup opening degree.

[0110] For example, if the refrigeration cycle apparatus S is installed in a cold region, it is necessary to more precisely control the opening degree of the pressure reducing mechanism 3 depending on the length of time that the refrigeration cycle apparatus S is not started. As an example of a method for doing so, when setting the opening degree of the pressure reducing mechanism 3, it is possible to combine the outside air temperature and the stop time of the compressor 1.

[0111] For example, if the degree of opening of the pressure reducing mechanism 3 is set to the first start-up degree of opening because the stop time of the compressor 1 is equal to or greater than the stop time threshold, and if the outside air temperature is lower than the outside air temperature threshold, the set first start-up degree of opening can be corrected to an even larger degree of opening. Conversely, if the degree of opening of the pressure reducing mechanism 3 is set to the second start-up degree of opening because the stop time of the compressor 1 is less than the stop time threshold, and if the outside air temperature is equal to or greater than the outside air temperature threshold, the second start-up degree of opening can be corrected to an even smaller degree of opening.

[0112] On the other hand, it is also possible to first set the opening degree of the pressure reducing mechanism 3 at the time of startup based on the outside air temperature, and then correct the set opening degree of the pressure reducing mechanism 3 using the stop time of the compressor 1. For example, if the opening degree of the pressure reducing mechanism 3 is set to the first startup opening degree because the outside air temperature is below the outside air temperature threshold, and the stop time of the compressor 1 is equal to or greater than the stop time threshold, it is also possible to correct the set first startup opening degree to an even larger opening degree.

[0113] In this case, for example, if the opening of the pressure reducing mechanism 3 is set to the second start-up opening because the outside air temperature is equal to or higher than the outside air temperature threshold, and the stop time of the compressor 1 is less than the stop time threshold, it is also possible to correct the set second start-up opening to an even smaller opening.

[0114] By setting the aperture of the pressure reducing mechanism 3 in this way, it is possible to set the aperture of the pressure reducing mechanism 3 in a way that is more suited to the state of the refrigerant when performing startup control. Additionally, the aperture of the pressure reducing mechanism 3 does not fall below the specified pressure, and it is possible to prevent liquid refrigerant from flowing into the compressor 1, thereby avoiding damage to the compressor 1.

[0115] Furthermore, after the operation mode is switched from startup control to normal control, the normal control method can also be controlled as described below. That is, the feedback control in the normal control performed after the refrigeration cycle has stabilized is performed based on two parameters: the temperature difference between the target value of the temperature (discharge temperature) of the refrigerant discharged from the compressor 1 detected by the discharge temperature detection sensor 11 and the current discharge temperature, and the change in the discharge temperature over time.

[0116] However, as explained above, in the startup control according to the embodiment of the present invention, the startup control is terminated and the control is switched to normal control when the refrigerant pressure on the low-pressure side starts to rise, as shown in Fig. 4(B). At this timing when the operation mode is switched, the refrigerant has not yet completely transitioned to a gas phase and is in a two-phase state.

[0117] In this way, if feedback control is executed as normal control when the refrigerant is in a two-phase state, an increase in discharge temperature due to operation of the compressor 1 is detected, and it may be determined that, of the two parameters described above, the discharge temperature in particular changes significantly over time. Therefore, although it would be desirable to control the opening of the pressure reducing mechanism 3 as small as possible in consideration of energy saving since this is normal control, there is a possibility that control will be executed to increase the opening of the pressure reducing mechanism 3 in order to make the change over time more gradual.

[0118] Therefore, in order to avoid such control from being executed, in the normal control of an embodiment of the present invention, if it is determined that the refrigerant state is in a two-phase state when transitioning from startup control to normal control, of the two parameters taken into consideration when executing normal control, the change in discharge temperature over time is not taken into consideration, and only the difference between the target value of the discharge temperature and the current discharge temperature is used as the control parameter.

[0119] That is, the control device 6 first estimates whether the refrigerant is in a two-phase state or a gas phase state. Specifically, the determination unit 66 determines whether the refrigerant is in a two-phase state or a gas phase state by determining whether the temperature difference obtained by subtracting the condensation temperature detected by the condensation temperature detection sensor 22 from the discharge temperature detected by the discharge temperature detection sensor 11 is equal to or greater than a predetermined value (for example, 0°C).

[0120] If the judgment unit 66 determines that the refrigerant is in a two-phase state, the judgment unit 66 instructs the setting unit 68 to set the opening degree of the pressure reducing mechanism 3 using the difference between the discharge temperature detected by the discharge temperature detection sensor 11 and the target discharge temperature.

[0121] On the other hand, if the judgment unit 66 judges that the refrigerant is in a gas phase state, the judgment unit 66 instructs the setting unit 68 to set the opening degree of the pressure reducing mechanism 3 using the difference between the discharge temperature detected by the discharge temperature detection sensor 11 and the target discharge temperature, and the change in the discharge temperature over time.

[0122] [Operation] Next, the control of the opening degree of the pressure reducing mechanism 3 in the above-mentioned startup control and normal control will be described with reference to the flowcharts shown in Fig. 6 to Fig. 9. Fig. 6 is a flowchart showing a basic flow of the control of the opening degree of the pressure reducing mechanism 3 at the time of startup of the refrigeration cycle apparatus S according to the embodiment of the present invention.

[0123] When the refrigeration cycle apparatus S (compressor 1) is started, the control device 6 starts the start-up control (ST1). Then, first, the opening degree of the pressure reducing mechanism 3 in the start-up control is set to a predetermined opening degree (ST2). Note that the setting of the opening degree of the pressure reducing mechanism 3 in the start-up control will be described separately with reference to FIG. 7 etc.

[0124] The information acquisition unit 61 acquires information on the condensation temperature from the condensation temperature detection sensor 22 (ST3) and also acquires information on the condenser suction air temperature from the condenser suction air temperature detection sensor 23 (ST4).

[0125] For convenience of explanation, the condensation temperature information and the condenser intake air temperature information have been described as being acquired in this order, but the order in which these pieces of information are acquired may vary, or they may be acquired simultaneously.

[0126] The calculation unit 62 calculates the startup temperature difference by subtracting the condenser intake air temperature from the condensation temperature information based on the condensation temperature information and the condenser intake air temperature information acquired by the information acquisition unit 61 (ST5). The calculation result is sent to the comparison unit 63 and compared with the temperature difference threshold value.

[0127] The comparison unit 63 accesses the memory unit 64 to obtain a temperature difference threshold, compares it with the startup temperature difference calculated by subtracting the condenser intake air temperature from the condensation temperature obtained from the calculation unit 62, and determines whether the startup temperature difference is greater than the temperature difference threshold (ST6).

[0128] If the temperature difference at startup is equal to or less than the temperature difference threshold value (NO in ST6), the pressure reduction mechanism 3 is in a state where the refrigerant is unlikely to circulate inside the refrigerant circuit C (a state where the refrigerant pressure on the low-pressure side, which is the pressure on the suction side of the compressor 1, is decreasing), and a low-density two-phase refrigerant flows in. In this case, the process returns to step ST3, and the processes of steps ST3 to ST6 described above are repeated.

[0129] On the other hand, if the comparison unit 63 determines that the temperature difference at startup is greater than the temperature difference threshold value (YES in ST6), the startup control is terminated and the control is switched to normal control (ST7). Specifically, the pressure reduction mechanism control unit 65 sets the opening of the pressure reduction mechanism 3 from the opening in the startup control up to now to the opening of the pressure reduction mechanism 3 in normal control (ST8).

[0130] The above is the basic control flow for the opening degree of the pressure reducing mechanism 3 at the time of startup of the refrigeration cycle apparatus S. Next, the flow for setting the opening degree of the pressure reducing mechanism 3 when startup control is initiated will be described with reference to Fig. 7. Fig. 7 is a flowchart relating to the control of the opening degree of the pressure reducing mechanism 3 at the time of startup of the refrigeration cycle apparatus S according to an embodiment of the present invention.

[0131] 7 illustrates a case where the stop time of the compressor 1 is taken into consideration when setting the opening degree of the pressure reducing mechanism 3. That is, when the start-up control is started (ST1), the determination unit 66 first checks the stop time of the compressor 1 measured by the timing unit 67 (ST21).

[0132] Then, the determination unit 66 acquires a stop time threshold stored in the memory unit 64, for example, and compares it with the stop time of the compressor 1 measured by the timer unit 67 (ST22). As a result, if the determination unit 66 determines that the stop time is equal to or greater than the stop time threshold (YES in ST22), the setting unit 68 sets the opening degree of the pressure reducing mechanism 3 to the first startup opening degree (ST23). Then, the pressure reducing mechanism control unit 65 controls the opening degree of the pressure reducing mechanism 3 to the first startup opening degree set by the setting unit 68.

[0133] On the other hand, if the determination unit 66 determines that the stop time is less than the stop time threshold value (NO in ST22), the setting unit 68 sets the opening degree of the pressure reducing mechanism 3 to the second startup opening degree (ST24). In this case, it can be considered that the refrigerant is in a state where it is easy for the refrigerant to circulate within the refrigerant circuit C, and therefore the opening degree of the pressure reducing mechanism 3 is set to the second startup opening degree, which is smaller than the first startup opening degree.

[0134] Thereafter, the control device 6 determines whether to switch the operation mode from startup control to normal control (ST3 to ST6). If the comparison unit 63 determines that the startup temperature difference is equal to or greater than the temperature difference threshold (YES in ST6), the operation mode is switched from startup control to normal control.

[0135] At this time, the determination unit 66 checks whether the opening of the pressure reducing mechanism 3 in the startup control has been set to the first startup opening (ST25). If it has been set to the first startup opening (YES in ST25), the determination unit 66 instructs the setting unit 68 to change the opening to the second startup opening, and the pressure reducing mechanism control unit 65 changes the opening of the pressure reducing mechanism 3 from the first startup opening to the second startup opening (ST26).

[0136] 4(A), there is a large difference between the opening degree of the pressure-reducing mechanism 3 in startup control and the opening degree of the pressure-reducing mechanism 3 targeted by performing feedback control in normal control. Therefore, if the opening degree of the pressure-reducing mechanism 3 in normal control is set by feedback control in conjunction with switching of the operation mode, it takes time to set the opening degree.

[0137] Therefore, by quickly changing the opening of the pressure reducing mechanism 3, which has been set to the first startup opening, to the second startup opening, and then controlling the opening of the pressure reducing mechanism 3 to that under normal control, the opening of the pressure reducing mechanism 3 can be quickly set to that under normal control, thereby ensuring start-up capacity.

[0138] Thereafter, the operating mode is switched from startup control to normal control (ST7), and the pressure reduction mechanism control unit 65 sets the opening degree of the pressure reduction mechanism 3 from the opening degree in the startup control up to that in normal control (ST8).

[0139] On the other hand, if the opening of the pressure reducing mechanism 3 in the startup control was originally set to the second startup opening (NO in ST25), the process of changing the first startup opening to the second startup opening as described above is not necessary, so the startup control is ended and normal control is started (ST7). Also, the pressure reducing mechanism control unit 65 sets the opening of the pressure reducing mechanism 3 to the opening in normal control (ST8).

[0140] Next, a control flow for another setting of the aperture of the pressure reducing mechanism 3 when startup control is initiated will be described with reference to Fig. 8. Fig. 8 is a flowchart relating to control of the aperture of the pressure reducing mechanism 3 at startup of the refrigeration cycle apparatus S according to an embodiment of the present invention. Here, a flow for setting the aperture of the pressure reducing mechanism 3 based on the stop time of the compressor 1 and then correcting the aperture of the pressure reducing mechanism 3 using the outside air temperature will be described.

[0141] First, the flow from when startup control is started until the aperture of the pressure reducing mechanism 3 is set using the stop time of the compressor 1 is as described using steps ST1 to ST24 shown in Fig. 7. Thereafter, the information acquiring unit 61 acquires information on the outside air temperature from the intake air temperature detection sensor 43 (ST31). Then, the determining unit 66 and the setting unit 68 correct the first startup aperture and the second startup aperture in accordance with the outside air temperature (ST32).

[0142] Specifically, when the stop time of the compressor 1 is equal to or greater than the stop time threshold and the opening of the pressure reducing mechanism 3 is set to the first start opening, and when the outside air temperature is lower than the outside air temperature threshold, the set first start opening can be corrected to an even larger opening.

[0143] Conversely, for example, if the opening of the pressure reducing mechanism 3 is set to the second start-up opening because the stop time of the compressor 1 is less than the stop time threshold, and if the outside air temperature is equal to or greater than the outside air temperature threshold, the second start-up opening can be corrected to an even smaller opening.

[0144] The subsequent processing flow (ST3 to ST8) is as explained using the flowchart shown in Fig. 7. Therefore, in Fig. 8, the processing flow from step ST3 onwards is partially omitted and is shown by dashed lines.

[0145] By carrying out the above-described process, the opening degree of the pressure reducing mechanism 3 can be set in full consideration of the state of the refrigerant in the environment in which the refrigeration cycle apparatus S is installed.

[0146] Next, the flow of normal control after the operation mode is switched from startup control to normal control will be described with reference to Fig. 9. Fig. 9 is a flowchart related to control of the opening degree of the pressure reducing mechanism 3 at the time of startup of the refrigeration cycle apparatus S according to the embodiment of the present invention.

[0147] First, the compressor 1 is started, and startup control is performed. After that, the process of setting the opening degree of the pressure reducing mechanism 3, which has been described so far, is performed, and the flow up to when the operating mode is switched from startup control to normal control is as described with reference to FIGS. 6 to 8.

[0148] 9 shows the state where the operation mode is switched from startup control to normal control and the degree of opening of the pressure-reducing mechanism 3 in normal control is set by the pressure-reducing mechanism control unit 65 (ST8). However, since the processing of step ST8 has already been explained, the content of this processing is indicated by dashed lines.

[0149] After transitioning to normal control, the control device 6 determines whether the refrigerant discharged from the compressor 1 is in a two-phase state (ST41). Specifically, as described above, the determination unit 66 determines whether the temperature difference obtained by subtracting the condensation temperature from the discharge temperature is equal to or greater than a predetermined value, thereby determining whether the refrigerant is in a two-phase state or a gas phase state.

[0150] If the judgment unit 66 judges that the discharged refrigerant is in a two-phase state (YES in ST41), the opening degree of the pressure reducing mechanism 3 is set (controlled) using the temperature difference between the target discharge temperature and the current discharge temperature (ST42).

[0151] On the other hand, if the judgment unit 66 judges that the discharged refrigerant is in a gas phase state (NO in ST41), the opening degree of the pressure reducing mechanism 3 is set (controlled) using the temperature difference between the target discharge temperature and the current discharge temperature, and the change in the discharge temperature over time (ST43).

[0152] Then, the determination unit 66 determines again whether the refrigerant discharged from the compressor 1 is in a two-phase state (ST44). If it is determined that the refrigerant is still in a two-phase state (YES in ST44), the process returns to step ST42 and the degree of opening of the pressure reducing mechanism 3 is set (controlled) using the temperature difference between the target discharge temperature and the current discharge temperature (ST42).

[0153] On the other hand, if the determination unit 66 determines that the refrigerant is in a gas phase state, similar to step ST43, the opening degree of the pressure reducing mechanism 3 is set (controlled) using the temperature difference between the target temperature of the discharge temperature and the current discharge temperature and the change in the discharge temperature over time (ST45).

[0154] By executing the startup control that begins when the compressor 1 starts up and the control of the opening degree of the pressure reducing mechanism 3 when the operating mode switches from startup control to normal control as described above, it is possible to ensure the reliability of the compressor when the refrigeration cycle device starts up and improve the start-up capability.

[0155] It should be noted that the present invention is not limited to the above-described embodiment, but is merely an example of the present invention. In the implementation stage, the components can be modified and embodied without departing from the spirit of the invention, and various changes and improvements can be made to the above-described embodiment. Furthermore, various inventions can be created by appropriately combining multiple components disclosed in the above-described embodiment.

[0156] For example, some components may be deleted from all of the components shown in the embodiments. Furthermore, components from different embodiments may be combined as appropriate, and such modified or improved forms may also be included in the present invention. Such embodiments and their modifications are included in the scope and spirit of the inventions, and are also included in the scope of the inventions and their equivalents as defined in the claims.

[0157] For example, in the above explanation, it has been assumed that if the startup temperature difference (condensation temperature minus condenser intake air temperature) is greater than the temperature difference threshold, the startup control will immediately transition to normal control. However, this type of control does not necessarily have to be performed.

[0158] That is, for example, even if the temperature difference at startup is greater than the temperature difference threshold, the startup control may be controlled to be executed for a preset minimum time. This is because, for example, when the compressor 1 starts, it is possible that the refrigerant is not circulating in the refrigerant circuit C even if the temperature difference at startup is greater than the temperature difference threshold. Therefore, for example, the minimum time is set to be the time until the refrigerant circulates through the refrigerant circuit C after the compressor 1 starts. Furthermore, this minimum time is obtained in advance through experimentation.

[0159] The techniques described in the embodiments of the present invention may also be configured as follows. (1) a refrigerant circuit in which a compressor, a condenser, a pressure reducing mechanism, and an evaporator are connected in sequence by refrigerant piping, and in which a refrigerant circulates; a condenser fan for blowing air into the condenser; a condensation temperature detection sensor that detects a condensation temperature of the refrigerant when the compressor is started; a condenser intake air temperature detection sensor that detects the temperature of the air drawn into the condenser by the condenser fan; a control device that switches between startup control that controls an opening degree of the pressure reducing mechanism at startup of the compressor to fix the opening degree to a preset startup opening degree, and normal control that controls the opening degree of the pressure reducing mechanism to a normal opening degree depending on a state of the refrigerant circulating through the refrigerant circuit, The control device The startup control is executed when the compressor is started. a refrigeration cycle device characterized in that, when a startup temperature difference obtained by subtracting the air temperature detected by the condenser intake air temperature detection sensor from the condensation temperature detected by the condenser temperature detection sensor is greater than a preset temperature difference threshold, the startup control is terminated and the control is switched to normal control. (2) The control device an information acquisition unit that acquires the condensation temperature and the air temperature; a calculation unit that calculates the startup temperature difference by subtracting the air temperature from the condensation temperature; a comparison unit that compares the startup temperature difference with a temperature difference threshold; The refrigeration cycle device described in (1) above is characterized in that it is provided with a pressure reduction mechanism control unit that changes the opening degree of the pressure reduction mechanism from the startup opening degree to the normal opening degree when the comparison result in the comparison unit shows that the startup temperature difference is greater than the temperature difference threshold value. (3) The refrigeration cycle device according to (1) or (2) above, wherein the condensation temperature detection sensor detects the temperature of the refrigerant discharged from the compressor. (4) The control device includes a timer that measures a stop time during which the compressor is stopped; a setting unit that sets the opening degree of the pressure reducing mechanism, The refrigeration cycle device according to any one of (1) to (3) above, wherein the setting unit sets the start-up opening degree of the pressure reducing mechanism based on the stop time measured by the timing unit. (5) When setting the starting opening, the setting unit: The refrigeration cycle device described in (4) above is characterized in that when the stop time is equal to or greater than a predetermined stop time threshold, a first start-up opening is set, and when the stop time is less than the stop time threshold, a second start-up opening which is smaller than the first start-up opening is set. (6) When switching from the startup control to the normal control, the control device The pressure reducing mechanism control unit The refrigeration cycle device described in (5) above is characterized in that when the startup opening is set to the first startup opening and it is determined that the startup temperature difference obtained by subtracting the air temperature from the condensation temperature is greater than the temperature difference threshold, the opening of the pressure reducing mechanism is changed so that the first startup opening becomes the second startup opening. (7) An outside air temperature detection sensor is provided to detect the outside air temperature. When setting the first start-up opening degree and the second start-up opening degree, the setting unit The refrigeration cycle device according to (6) above, wherein the first start-up opening and the second start-up opening are corrected based on the outside air temperature detected by the outside air temperature detection sensor. (8) The refrigeration cycle device described in (7) above, characterized in that the setting unit corrects the first startup opening and the second startup opening based on the outside air temperature, so that the lower the outside air temperature, the larger the first startup opening and the smaller the second startup opening. (9) A discharge temperature detection sensor is provided to detect the discharge temperature of the refrigerant discharged from the compressor, the control device controls the opening degree of the pressure reducing mechanism in the normal control so that the discharge temperature becomes a preset target discharge temperature; The control device estimates whether the refrigerant is in a two-phase state or a gas phase state; When it is determined that the refrigerant is in the gas phase state, the control device sets an opening degree of the pressure reducing mechanism using a difference between the discharge temperature detected by the discharge temperature sensor and the target discharge temperature and a change in the discharge temperature over time; The refrigeration cycle device described in (1) above is characterized in that when it is determined that the refrigerant is in the two-phase state, the opening degree of the pressure reducing mechanism is set using the difference between the discharge temperature detected by the discharge temperature sensor and the target discharge temperature. [Explanation of symbols]

[0160] 1 compressor, 11 discharge temperature detection sensor, 2 indoor heat exchanger, 21 indoor fan (condenser fan), 22 refrigerant temperature detection sensor (condensation temperature detection sensor), 23 intake air temperature detection sensor (condenser intake air temperature detection sensor), 3 pressure reduction mechanism, 4 outdoor heat exchanger, 41 outdoor fan, 42 refrigerant temperature detection sensor, 43 intake air temperature detection sensor, 5 four-way valve, 6 control device, 61 information acquisition unit, 62 calculation unit, 63 comparison unit, 64 memory unit, 65 pressure reduction mechanism control unit, 66 determination unit, 67 timing unit, 68 setting unit, C refrigerant circuit, S refrigeration cycle device

Claims

1. a refrigerant circuit in which a compressor, a condenser, a pressure reducing mechanism, and an evaporator are connected in sequence by refrigerant piping, and in which a refrigerant circulates; a condenser fan for blowing air into the condenser; a condensation temperature detection sensor that detects a condensation temperature of the refrigerant when the compressor is started; a condenser intake air temperature detection sensor that detects the temperature of the air drawn into the condenser by the condenser fan; a control device that switches between startup control that controls an opening degree of the pressure reducing mechanism at startup of the compressor to fix the opening degree to a preset startup opening degree, and normal control that controls the opening degree of the pressure reducing mechanism to a normal opening degree depending on a state of the refrigerant circulating through the refrigerant circuit, The control device The startup control is executed when the compressor is started. a refrigeration cycle device characterized in that, when a startup temperature difference obtained by subtracting the air temperature detected by the condenser intake air temperature detection sensor from the condensation temperature detected by the condenser temperature detection sensor is greater than a preset temperature difference threshold, the startup control is terminated and the control is switched to normal control.

2. The control device an information acquisition unit that acquires the condensation temperature and the air temperature; a calculation unit that calculates the startup temperature difference by subtracting the air temperature from the condensation temperature; a comparison unit that compares the startup temperature difference with a temperature difference threshold; 2. The refrigeration cycle device according to claim 1, further comprising: a pressure reducing mechanism control unit that changes an opening degree of the pressure reducing mechanism from the startup opening degree to the normal opening degree when the comparison result in the comparison unit indicates that the startup temperature difference is greater than the temperature difference threshold value.

3. 2. The refrigeration cycle apparatus according to claim 1, wherein the condensation temperature detection sensor detects the temperature of the refrigerant discharged from the compressor.

4. The control device includes a timer that measures a stop time during which the compressor is stopped; a setting unit that sets the opening degree of the pressure reducing mechanism, 4. The refrigeration cycle apparatus according to claim 1, wherein the setting unit sets the startup opening of the pressure reducing mechanism based on the stop time measured by the timer unit.

5. When setting the start opening, the setting unit 5. The refrigeration cycle device according to claim 4, wherein when the stop time is equal to or greater than a predetermined stop time threshold, a first start-up opening is set, and when the stop time is less than the stop time threshold, a second start-up opening that is smaller than the first start-up opening is set.

6. When switching from the startup control to the normal control, the control device The pressure reducing mechanism control unit 6. The refrigeration cycle device according to claim 5, wherein when the startup opening is set to the first startup opening and it is determined that a startup temperature difference obtained by subtracting the air temperature from the condensing temperature is greater than the temperature difference threshold, the opening of the pressure reducing mechanism is changed so that the first startup opening becomes the second startup opening.

7. An outside air temperature detection sensor is provided to detect the outside air temperature, When setting the first start-up opening degree and the second start-up opening degree, the setting unit 7. The refrigeration cycle device according to claim 6, wherein the first starting opening and the second starting opening are corrected based on the outside air temperature detected by the outside air temperature detection sensor.

8. The refrigeration cycle device according to claim 7, characterized in that the setting unit corrects the first startup opening and the second startup opening based on the outside air temperature such that the lower the outside air temperature, the larger the first startup opening and the smaller the second startup opening.

9. a discharge temperature detection sensor for detecting a discharge temperature of the refrigerant discharged from the compressor; the control device controls the opening degree of the pressure reducing mechanism in the normal control so that the discharge temperature becomes a preset target discharge temperature; The control device estimates whether the refrigerant is in a two-phase state or a gas phase state; When it is determined that the refrigerant is in the gas phase state, the control device sets an opening degree of the pressure reducing mechanism using a difference between the discharge temperature detected by the discharge temperature sensor and the target discharge temperature and a change in the discharge temperature over time; 2. The refrigeration cycle device according to claim 1, wherein when it is determined that the refrigerant is in the two-phase state, the opening degree of the pressure reducing mechanism is set using a difference between the discharge temperature detected by the discharge temperature sensor and the target discharge temperature.

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