Refrigeration cycle device

Abstract

This refrigeration cycle device (1001) comprises a refrigerant circuit (C1) through which a refrigerant circulates and which includes a compressor (1), an outdoor heat exchange device (3), a first pressure reducing device (4), and an indoor heat exchange device (150), and provided in the refrigerant circuit (C1) are a first bypass channel (BP1) connected in parallel with the compressor (1), a second pressure reducing device (7) installed in the first bypass channel (BP1) and configured to have a changeable degree of opening, and a control device (100) that controls the refrigerant circuit (C1) and the second pressure reducing device (7). The control device (100) is configured to change the degree of opening of the second pressure reducing device (7) according to the heat exchange capacity of the indoor heat exchange device (150).

Description

Refrigeration cycle equipment

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

[0002] As homes become more highly insulated and airtight, the target minimum capacity per indoor unit is decreasing. As a result, the difference between the maximum and minimum capacity of an indoor unit is widening. In order to operate continuously with a lower target capacity per unit, some air conditioners not only minimize the frequency but also reduce capacity by installing a bypass circuit.

[0003] For example, the air conditioner disclosed in JP 2002-31387 A (Patent Document 1) has an electric valve between the compressor discharge pipe and the accumulator suction pipe to adjust the refrigerant flow rate, and controls the electric valve so that the compressor suction pressure during cooling operation is equal to or greater than a predetermined value.

[0004] Japanese Patent Application Laid-Open No. 2002-31387

[0005] In recent years, air conditioners have improved their energy-saving performance by improving their heat transfer performance, such as by increasing the size of the heat exchanger in the indoor unit, and by reducing the difference between the condensation temperature and the evaporation temperature.

[0006] However, when the indoor unit has a high capacity, the difference between the target temperature and the evaporation temperature can be small during cooling operation, which can result in the evaporation temperature being higher than before and even higher than the dew point of the indoor air. In this state, there is a problem that dehumidification becomes impossible.

[0007] In the air conditioner disclosed in JP 2002-31387 A (Patent Document 1), the motor-operated valve is controlled according to values ​​detected by a suction pressure sensor or the like, and the refrigerant flow rate during low load operation is adjusted to reduce the capacity of the indoor unit. However, pressure fluctuations during low load operation are small, making it prone to false detection. Also, controlling the motor-operated valve after pressure fluctuations occur causes the problem of slow response.

[0008] The present disclosure is intended to solve the above-mentioned problems, and has an object to provide a refrigeration cycle device that is capable of dehumidifying even during low-load operation.

[0009] The refrigeration cycle apparatus of the present disclosure includes a refrigerant circuit including a compressor, an outdoor heat exchanger, a first pressure reducing device, and an indoor heat exchanger, and includes a first bypass flow path connected in parallel to the compressor in the refrigerant circuit, a second pressure reducing device provided in the first bypass flow path and configured to have a variable opening, and a control device that controls the refrigerant circuit and the second pressure reducing device. The control device is configured to change the opening of the second pressure reducing device in accordance with the heat exchange capacity of the indoor heat exchanger.

[0010] According to the refrigeration cycle device of the present disclosure, dehumidification is possible even during low load operation.

[0011] FIG. 1 is a refrigerant circuit diagram showing the configuration of a refrigeration cycle apparatus of Embodiment 1. FIG. 1 is a diagram for explaining problems associated with high insulation and airtightness of a building. FIG. 2 is a flowchart for explaining the control of the aperture of the second pressure reducing device 7 executed in Embodiment 1. FIG. 3 is a diagram showing the relationship between the operating frequency of the compressor and the aperture of the second pressure reducing device 7 with respect to the number of operating indoor units in Modification 1 of Embodiment 1. FIG. 2 is a refrigerant circuit diagram showing the configuration of a refrigeration cycle apparatus of Modification 1 of Embodiment 1. FIG. 3 is a flowchart for explaining the control of the aperture of the second pressure reducing device 7 executed in Modification 1 of Embodiment 1. FIG. 4 is a diagram showing the relationship between the operating frequency of the compressor and the aperture of the second pressure reducing device 7 with respect to the number of operating indoor units in Modification 1 of Embodiment 1. FIG. 4 is a refrigerant circuit diagram showing the configuration of a refrigeration cycle apparatus of Modification 2 of Embodiment 1. FIG. 5 is a flowchart for explaining the control of the aperture of the second pressure reducing device 7 executed in Modification 2 of Embodiment 1. FIG. 6 is a diagram showing the relationship between the operating frequency of the compressor and the aperture of the second pressure reducing device 7 with respect to the number of operating indoor units (or the rated capacity integrated value) in Modification 2 of Embodiment 1. FIG. 7 is a refrigerant circuit diagram showing the configuration of a refrigeration cycle apparatus of Modification 3 of Embodiment 1. 1 is a flowchart for explaining the control of the opening degree of the second pressure reducing device 7 performed in heating operation in a third modification of the first embodiment. FIG. 2 is a flowchart for explaining the control of the opening degree of the second pressure reducing device 7 performed in cooling operation in a third modification of the first embodiment. FIG. 3 is a refrigerant circuit diagram showing the configuration of a refrigeration cycle device of a second embodiment. FIG. 4 is a flowchart for explaining the control of a switching circuit performed in the second embodiment. FIG. 5 is a refrigerant circuit diagram showing the configuration of a refrigeration cycle device of a second modification of the second embodiment.

[0012] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Although several embodiments will be described below, it was originally intended that the configurations described in each embodiment be combined as appropriate. Note that the same or corresponding parts in the drawings will be designated by the same reference numerals, and their description will not be repeated.

[0013] Embodiment 1 In embodiment 1, a refrigeration cycle apparatus is described which is provided with a detection sensor (for example, one that detects an operation signal or an integrated rated capacity value of an indoor unit in operation) that detects the number of operating indoor units, and which is equipped with a control device that changes the opening degree of a pressure reducing device in accordance with the number of operating indoor units detected by the detection sensor.

[0014] Fig. 1 is a refrigerant circuit diagram showing the configuration of a refrigeration cycle apparatus according to Embodiment 1. As shown in Fig. 1, a refrigeration cycle apparatus 1001 includes a refrigerant circuit C1 and a first bypass flow path BP1.

[0015] The refrigerant circuit C1 includes a compressor 1, an outdoor heat exchange device 3, a first pressure reducing device 4, and an indoor heat exchange device 150, and refrigerant circulates through the refrigerant circuit C1. The first bypass flow path BP1 is connected in parallel to the compressor 1 in the refrigerant circuit C1. That is, a branching point 6 is provided between the discharge pipe side of the compressor 1 and the four-way valve 2, and a junction point 8 is provided between the suction pipe side of the compressor 1 and the four-way valve 2. The first bypass flow path BP1 is connected between the branching point 6 and the junction point 8, branches from the refrigerant circuit C1 at the branching point 6, and merges with the refrigerant circuit C1 at the junction point 8.

[0016] The refrigeration cycle apparatus 1001 further includes a second pressure reducing device 7 that is provided in the first bypass flow path BP1 and is configured to change its opening degree, and a control device 100 that controls the refrigerant circuit C1 and the second pressure reducing device 7. The control device 100 is configured to change the opening degree of the second pressure reducing device 7 in accordance with the heat exchange capacity of the indoor heat exchange device 150.

[0017] The refrigeration cycle apparatus 1001 includes an outdoor unit 61, extension pipes 64 and 65, a branching-merging section 62, and an indoor air conditioning unit 63. The components of the refrigerant circuit C1 are arranged separately in the outdoor unit 61, the extension pipes 64 and 65, the branching-merging section 62, and the indoor air conditioning unit 63.

[0018] The outdoor unit 61 includes a compressor 1, a first bypass flow path BP1, a four-way valve 2, an outdoor heat exchange device 3, a second pressure reducing device 7, and a control device 100.

[0019] The first pressure reducing device 4 is disposed at the branching-converging section 62. The first pressure reducing device 4 includes expansion valves 41-44.

[0020] The indoor air conditioner 63 is provided with an indoor heat exchanger 150. The indoor heat exchanger 150 includes a plurality of indoor units 151 to 154. Each of the plurality of indoor units 151 to 154 includes an indoor heat exchanger 5, an operation detection unit 50, and a fan 161. The indoor units 151 to 154 may be provided in different rooms or in the same room.

[0021] The control device 100 includes a CPU (Central Processing Unit) 101, a memory 102, an input / output buffer (not shown), etc., and controls the four-way valve 2, the compressor 1, the first pressure reducing device 4, the second pressure reducing device 7, the fan 161, etc. in the refrigeration cycle apparatus 1001. Note that this control is not limited to software processing, and can also be processed by dedicated hardware (electronic circuitry). The control device 100 may be distributed in the indoor units 151 to 154 and the outdoor unit 61, or may be located in a location other than the outdoor unit 61.

[0022] Figure 2 is a diagram illustrating the problems associated with highly insulated and airtight buildings. In the case of a multi-air conditioner with multiple indoor units, the difference in capacity per multi-air conditioner, that is, the difference in capacity between when there are a few operating indoor units and when there are a lot of operating indoor units, becomes significant.

[0023] In Figure 2, the vertical axis represents the compressor operating frequency (hereinafter referred to as the required frequency) or the corresponding refrigerant circulation amount required to achieve the target minimum capacity for air-conditioning a room when the number of operating indoor units out of five indoor units changes, and the horizontal axis represents the number of indoor units in operation. Line G0 is a graph showing the relationship between the number of operating indoor units and the required frequency when installed in a conventional home. Line G1 is a graph showing the relationship between the number of operating indoor units and the required frequency when installed in a modern home with advanced insulation and airtightness.

[0024] Here, the lower limit frequency fmin at which the compressor can operate is shown. In other words, the lower limit frequency fmin is the lower limit value of the operating frequency of the compressor set for that product. For each number of operating indoor units shown on the horizontal axis of Fig. 2, the vertical axis of Fig. 2 represents the frequency required to achieve the target minimum capacity, and if the required frequency is lower than the lower limit frequency fmin, it is considered that on / off operation will be performed.

[0025] In Figure 2, circles (◯) indicate continuous operation, while triangles (△) indicate cases where continuous operation would result in overly effective air conditioning, so the compressor switches to on-off operation, repeatedly turning on and off. In the case of line G0, on-off operation is performed only when there is only one indoor unit in operation, but in the case of line G1, on-off operation is performed when there are one, two, or three indoor units in operation due to a decrease in the air conditioning load in the room.

[0026] Since on-off operation reduces comfort, one possible way to avoid on-off operation is to flow refrigerant through the bypass flow path BP1 in Figure 1. However, if the bypass flow rate is fixed in an air conditioner equipped with multiple indoor units, the required frequency may fall below the lower limit frequency fmin depending on the number of operating indoor units, resulting in on-off operation as indicated by the triangles (△) in Figure 2.

[0027] In the case of a conventional building where high insulation and airtightness have not been advanced (line G0), the required frequency is lower than the lower limit frequency fmin only when one unit is operating, resulting in on / off operation, but since this was only when one unit was operating, control of the bypass flow rate was simple and a fixed value was sufficient.In contrast, in the case where the target minimum capacity has decreased due to high insulation and airtightness (line G1), the required frequency is lower than the lower limit frequency fmin when one, two, or three units are operating, making it difficult to achieve optimal capacity with a fixed bypass flow rate.

[0028] Therefore, in this embodiment, an operation detection unit 50 is installed that detects the number of operating indoor units based on, for example, an operation signal, the integrated rated capacity value of the operating indoor units, etc. The control device 100 is configured to control the second pressure reducing device 7 so that the opening degree decreases as the number of operating indoor units detected by the operation detection unit 50 increases.

[0029] 3 is a flowchart illustrating the control of the opening degree of the second pressure reducing device 7 executed in the first embodiment. First, in step S1, the control device 100 detects the operating frequency of the compressor 1. Then, in step S2, the control device 100 detects whether the operating frequency of the compressor 1 is at a specified value. The specified value in step S2 is a value corresponding to the lower limit frequency fmin in FIG. 2 .

[0030] If the operating frequency of the compressor 1 is not the specified value (NO in S2), the control of this flowchart is terminated because if the air conditioning load is small, the operating frequency of the compressor can be lowered with the second pressure reducing device 7 closed.

[0031] On the other hand, if the operating frequency of compressor 1 is not the specified value (NO in S2), compressor 1 will operate in on-off mode unless refrigerant is passed through bypass flow path BP1. For this reason, in step S3, control device 100 detects the number of operating indoor units using operation detection unit 50, and then in step S4, controls the opening degree of the second pressure reducing device based on the number of operating indoor units. For example, the control device 100 reduces the opening degree of the second pressure reducing device 7 as the number of operating indoor units increases. After the opening degree of second pressure reducing device 7 is set in step S4, the processing from step S1 is repeated again.

[0032] FIG. 4 is a diagram showing the relationship between the operating frequency of the compressor and the opening degree of the second pressure reducing device 7 relative to the number of operating indoor units (or the integrated value of the rated capacity).

[0033] FIG. 4 shows an example corresponding to graph G1 shown in FIG. 2. When the second pressure reducing device 7 is closed, the required frequency when five indoor units are operating is higher than the lower limit frequency fmin. In this case, the required frequency when four indoor units are operating is equal to the lower limit frequency fmin. Once the operating frequency reaches the lower limit frequency, the compressor frequency cannot be further reduced. Therefore, when fewer than four indoor units are operating, the required frequency remains at the lower limit frequency fmin. Instead, when fewer than four indoor units are operating, refrigerant flows through the first bypass flow path BP1 to prevent on / off operation. When four indoor units are operating, the required frequency = the lower limit frequency fmin, so the second pressure reducing device 7 is closed (opening degree is zero). When three indoor units are operating, the second pressure reducing device 7 is opened. As the number of operating indoor units decreases from two to one, the opening degree of the second pressure reducing device 7 increases to increase the amount of refrigerant flowing through the first bypass flow path BP1.

[0034] 4 shows a case where the horizontal axis represents the number of operating units, but it may also represent the integrated rated capacity value of the indoor units. For example, the integrated rated capacity value increases as the number of operating units increases and as the airflow rate of each indoor unit increases.

[0035] For example, the opening degree of the second pressure reducing device 7 can be expressed as a function f of the number of operating indoor units or the integrated rated capacity value, as shown in the following equation: Opening degree of the second pressure reducing device = f (number of operating indoor units or integrated rated capacity value) According to the air conditioner of the first embodiment described above, on / off operation can be suppressed when a large number of indoor units are installed, thereby improving user comfort. Furthermore, because control is performed based on changes in the number of operating indoor units, the response is faster than when the second pressure reducing device 7 is controlled by observing temperature changes, etc., and therefore a decrease in comfort can be suppressed.

[0036] Variation 1 of Embodiment 1. Variation 1 is characterized in that, in addition to the air conditioner of Embodiment 1, it further includes a control device that changes the opening degree of the second pressure reducing device 7 based on the indoor-outdoor temperature difference. In this case, the control device calculates the indoor-outdoor temperature difference of each heat exchanger from the ambient temperatures of the indoor and outdoor heat exchangers (for example, the intake temperature of each heat exchanger).

[0037] Fig. 5 is a refrigerant circuit diagram showing the configuration of a refrigeration cycle apparatus according to Modification 1 of Embodiment 1. As shown in Fig. 5, a refrigeration cycle apparatus 1001A includes an indoor heat exchanger 150A instead of the indoor heat exchanger 150 in the configuration of the refrigeration cycle apparatus 1001 shown in Fig. 1.

[0038] The indoor heat exchange device 150A includes a plurality of indoor units 151A to 154A. Each of the plurality of indoor units 151A to 154A includes an indoor heat exchanger 5 and a temperature sensor 51 that detects the indoor temperature. Each of the plurality of indoor units 151A to 154A includes a fan 161, as in the case of Fig. 1, but this is not shown. The indoor units 151A to 154A may be placed in different rooms or in the same room.

[0039] The refrigeration cycle apparatus 1001A further includes a temperature sensor 52 for detecting an outdoor temperature in addition to the configuration of the refrigeration cycle apparatus 1001 shown in FIG.

[0040] Other configurations of the refrigeration cycle apparatus 1001A are similar to those in FIG. 1, and therefore description thereof will not be repeated.

[0041] In the first modification of the first embodiment, the control device 100 calculates the indoor-outdoor temperature difference from the difference between the temperatures detected by the temperature sensors 51 and 52. The control device 100 is configured to compare the indoor-outdoor temperature difference with a reference value and change the degree of opening of the second pressure reducing device.

[0042] If there are multiple indoor heat exchangers, the control device 100 uses the average temperature detected by each temperature sensor 51 as the indoor temperature. Alternatively, the control device uses the detected temperature at which the indoor-outdoor temperature difference is at its maximum as the indoor temperature. The indoor-outdoor temperature difference is an index that indicates the magnitude of the air conditioning load, and is calculated by subtracting the indoor temperature from the outdoor temperature during cooling operation, and by subtracting the outdoor temperature from the indoor temperature during heating operation.

[0043] 6 is a flowchart illustrating the control of the opening degree of the second pressure reducing device 7 executed in the first modification of the first embodiment. First, in step S11, the control device 100 detects the operating frequency of the compressor 1. Then, in step S12, the control device 100 detects whether the operating frequency of the compressor 1 is at a specified value. The specified value in step S12 is a value corresponding to the lower limit frequency fmin in FIG. 2 .

[0044] If the operating frequency of compressor 1 is not the specified value (NO in S12), and if the air conditioning load is small, the operating frequency of the compressor can be lowered with the second pressure reducing device 7 closed, eliminating the need for on / off operation, and the control of this flowchart is terminated.

[0045] On the other hand, if the operating frequency of the compressor 1 is at the specified value (YES in S12), the compressor 1 will operate in an on-off state unless the refrigerant is passed through the bypass flow path BP1. Therefore, in step S13, the control device 100 detects the ambient temperatures of each heat exchanger and calculates the indoor-outdoor temperature difference. Then, in step S14, it is determined whether the indoor-outdoor temperature difference is greater than a reference value.

[0046] If the indoor-outdoor temperature difference is greater than the reference value (YES in S14), the control device 100 reduces the opening degree of the second pressure reducing device 7 from the current value in step S15. On the other hand, if the indoor-outdoor temperature difference is not greater than the reference value (NO in S14), the control device 100 increases the opening degree of the second pressure reducing device 7 from the current value in step S16.

[0047] After the opening degree of the second pressure reducing device 7 is set in step S15 or S16, the process is repeated from step S11.

[0048] FIG. 7 is a diagram showing the relationship between the compressor operating frequency and the aperture of the second pressure-reducing device 7 with respect to the number of operating indoor units (or the integrated rated capacity value) in Variation 1 of Embodiment 1. The vertical and horizontal axes and required frequency in FIG. 7 are the same as those in FIG. 4. Regarding the required aperture of the second pressure-reducing device 7, a solid line represents graph DE (the same graph as in FIG. 4) in which the indoor-outdoor temperature difference is equal to the reference value. Above that, a coarse dashed line represents graph DS, which represents a case in which the indoor-outdoor temperature difference is smaller than the reference value. Below that, a fine dashed line represents graph DL, which represents a case in which the indoor-outdoor temperature difference is larger than the reference value. While the required aperture is an illustration and not accurate, the ½ power of the pressure difference (temperature difference) affects the required aperture. It can be seen that the required aperture of the second pressure-reducing device 7 increases as the indoor-outdoor temperature difference decreases when the number of operating indoor units is one, two, or three.

[0049] As described above, in the first modification of the first embodiment, the amount of refrigerant flowing through the bypass flow path BP1 can be adjusted to an appropriate amount by correcting the opening based on the indoor-outdoor temperature difference. Furthermore, by determining the opening based on the ambient temperature, responsiveness can be improved and a decrease in comfort can be suppressed.

[0050] Variation 2 of Embodiment 1 Variation 2 is characterized in that, compared to the air conditioner of Embodiment 1, it further includes a control device that calculates the suction density of the refrigerant when the low-pressure section pressure changes, and changes the aperture of the second pressure reducing device 7 based on the change in suction density. When the low-pressure section pressure drops, the suction density also drops, and in this case the control device reduces the aperture of the second pressure reducing device 7 in response to the decrease in suction density.

[0051] Fig. 8 is a refrigerant circuit diagram showing the configuration of a refrigeration cycle apparatus according to Modification 2 of Embodiment 1. As shown in Fig. 8, a refrigeration cycle apparatus 1001B includes an indoor heat exchanger 150B instead of the indoor heat exchanger 150 in the configuration of the refrigeration cycle apparatus 1001 shown in Fig. 1.

[0052] The indoor heat exchange device 150B includes a plurality of indoor units 151B to 154B. Each of the plurality of indoor units 151B to 154B includes an indoor heat exchanger 5 and a temperature sensor 51 that detects the indoor temperature. Each of the plurality of indoor units 151B to 154B includes a fan 161, as in the case of Fig. 1, but this is not shown. The indoor units 151B to 154B may be placed in different rooms or in the same room.

[0053] The refrigeration cycle apparatus 1001B further includes a temperature sensor 52 for detecting an outdoor temperature and a sensor 53 in the configuration of the refrigeration cycle apparatus 1001 shown in FIG. 1 . The sensor 53 is configured to detect the pressure on the low-pressure side. The sensor 53 may be, for example, a sensor for detecting the suction pressure of the compressor 1. Also, for example, the sensor 53 may be a sensor for detecting the pressure or suction temperature of the indoor unit heat exchanger during cooling operation, and a sensor for detecting the pressure or outdoor air temperature of the outdoor unit heat exchanger during heating operation.

[0054] Other configurations of the refrigeration cycle apparatus 1001B are the same as those in FIG. 1, and therefore description thereof will not be repeated.

[0055] In the second modification of the first embodiment, the control device 100 is configured to calculate the suction density of the refrigerant from the value detected by the sensor 53, compare the suction density with a second reference value, and change the opening degree of the second pressure reducing device 7. The control device 100 can predict the suction density from the pressure or temperature detected by the sensor 53 and the ph diagram. For example, an equation corresponding to the function f, such as suction density ρ=f (pressure or temperature), may be set.

[0056] 9 is a flowchart illustrating the control of the opening degree of the second pressure reducing device 7 executed in the second modification of the first embodiment. First, in step S21, the control device 100 detects the operating frequency of the compressor 1. Then, in step S22, the control device 100 detects whether the operating frequency of the compressor 1 is at a specified value. The specified value in step S22 is a value corresponding to the lower limit frequency fmin in FIG. 2 .

[0057] If the operating frequency of compressor 1 is not the specified value (NO in S22), and if the air conditioning load is small, the operating frequency of the compressor can be lowered with the second pressure reducing device 7 closed, eliminating the need for on / off operation, and the control of this flowchart is terminated.

[0058] On the other hand, if the operating frequency of the compressor 1 is the specified value (YES in S22), the compressor 1 will undergo on-off operation unless the refrigerant is passed through the bypass flow path BP1. Therefore, in step S23, the control device 100 detects the pressure on the low-pressure side with the sensor 53 and calculates the suction density of the refrigerant based on the detected value. Then, in step S24, it is determined whether the suction density is greater than a second reference value.

[0059] If the suction density is greater than the second reference value (YES in S24), the control device 100 increases the opening degree of the second pressure reducing device 7 from the current value in step S25. On the other hand, if the suction density is not greater than the second reference value (NO in S24), the control device 100 decreases the opening degree of the second pressure reducing device 7 from the current value in step S26.

[0060] After the opening degree of the second pressure reducing device 7 is set in step S25 or S26, the process from step S21 is repeated again.

[0061] FIG. 10 is a diagram showing the relationship between the operating frequency of the compressor and the aperture of the second pressure-reducing device 7 relative to the number of operating indoor units (or the integrated value of the rated capacity) in Modification 2 of Embodiment 1. The vertical and horizontal axes and the required frequency in FIG. 10 are the same as those in FIGS. 4 and 7. Regarding the required aperture of the second pressure-reducing device 7, graph DE2 (the same graph as in FIG. 4) in which the indoor-outdoor temperature difference is equal to the reference value is shown in the center as a solid line. Above it is shown graph DL2 in a coarse dashed line, which represents a case in which the suction density is higher than the reference value. Below that is shown graph DS2 in a fine dashed line, which represents a case in which the suction density is lower than the reference value. It can be seen that the required aperture of the second pressure-reducing device 7 increases as the suction density increases when the number of operating indoor units is one, two, or three.

[0062] As described above, in the second modification of the first embodiment, the amount of refrigerant flowing through the bypass passage BP1 can be adjusted to an appropriate amount by correcting the opening based on the suction density. Furthermore, by determining the opening based on the suction density, responsiveness can be improved and a decrease in comfort can be suppressed.

[0063] Modification 3 of Embodiment 1 Fig. 11 is a refrigerant circuit diagram showing the configuration of a refrigeration cycle apparatus according to Modification 3 of Embodiment 1. As shown in Fig. 11, a refrigeration cycle apparatus 1001C includes an indoor heat exchanger 150C instead of the indoor heat exchanger 150 in the configuration of the refrigeration cycle apparatus 1001 shown in Fig. 1.

[0064] The indoor heat exchange device 150C includes multiple indoor units 151C to 154C. Each of the multiple indoor units 151C to 154C includes an indoor heat exchanger 5 and a sensor 54. Each of the multiple indoor units 151C to 154C includes a fan 161, similar to the case of Fig. 1, but this is not shown. The indoor units 151C to 154C may be placed in different rooms or in the same room.

[0065] The sensor 54 is a sensor for directly or indirectly detecting the pressure of the indoor heat exchanger 5. The sensor 54 may be a pressure sensor that directly detects the pressure of the indoor heat exchanger 5, or may be a sensor that detects the suction temperature or two-phase pipe temperature for calculating the pressure.

[0066] The refrigeration cycle apparatus 1001C further includes a temperature sensor 52 for detecting an outdoor temperature and a sensor 53 in the configuration of the refrigeration cycle apparatus 1001 shown in FIG. 1 . The sensor 53 is configured to detect the pressure on the low-pressure side. The sensor 53 may be, for example, a sensor for detecting the suction pressure of the compressor 1. Also, for example, the sensor 53 may be a sensor for detecting the pressure or suction temperature of the indoor unit heat exchanger during cooling operation, and a sensor for detecting the pressure or outdoor air temperature of the outdoor unit heat exchanger during heating operation.

[0067] Other configurations of the refrigeration cycle apparatus 1001C are the same as those in FIG. 1, and therefore description thereof will not be repeated.

[0068] The control device 100 of variant example 3 is characterized in that, when the second pressure reducing device 7 is open, the pressure of the indoor unit side heat exchanger is detected, the pressure difference is calculated from the detected pressure and the target pressure, and the compressor frequency is increased or decreased according to the pressure.

[0069] 12 is a flowchart illustrating the control of the opening degree of the second pressure reducing device 7 executed during heating operation in the third modification of the first embodiment. First, in step S31, the control device 100 detects the operating frequency of the compressor 1. Then, in step S32, the control device 100 detects the opening degree of the second pressure reducing device 7. Then, in step S33, the control device 100 determines whether the second pressure reducing device 7 is in the open state.

[0070] If the second pressure reducing device 7 is open (YES in S33), in step S34, the pressure of the indoor heat exchanger 5 is detected based on the detection value of the sensor 54, and the pressure difference between the detected pressure and the target pressure is calculated. If the bypass flow path BP1 is open and the bypass flow rate is higher than expected, the capacity may be insufficient relative to the load on the indoor side.

[0071] When the capacity is somewhat insufficient like this, the pressure on the indoor unit side drops during heating operation, so the detected value becomes smaller than the target pressure and the pressure difference becomes a positive (+) value.

[0072] In step S35, the control device 100 determines whether the absolute value of the pressure difference is greater than the third reference value. If |pressure difference|>third reference value is true (YES in S35), the control device 100 determines in step S36 whether the pressure difference is a positive (+) value.

[0073] If the pressure difference > 0 holds (YES in S36), the heating operation is in progress and the capacity is insufficient. If the pressure difference > 0 does not hold (NO in S36), the heating operation is in progress and the capacity is excessive.

[0074] For example, during heating operation, if the pressure difference is a positive value and the absolute value of the pressure difference is greater than the third reference value (YES in S35 and YES in S36), the control device 100 increases the frequency of the compressor 1 in step S37. This improves the capacity deficiency.

[0075] Furthermore, for example, during heating operation, if the pressure difference is negative and the absolute value of the pressure difference is greater than the third reference value (YES in S35 and NO in S36), the control device 100 increases the opening of the second pressure reducing device 7 in step S38. This eliminates the excess capacity.

[0076] After the opening degree of the second pressure reducing device 7 is set in step S37 or S38, the process from step S31 is repeated again.

[0077] On the other hand, if the second pressure reducing device 7 is in the closed state (NO in S33) or the absolute value of the pressure difference is equal to or less than the third reference value (NO in S45), and the air conditioning load is small, the on / off operation can be avoided by lowering the operating frequency of the compressor with the second pressure reducing device 7 in the closed state. Therefore, the control of this flowchart is exited.

[0078] 13 is a flowchart for illustrating the control of the opening degree of the second pressure reducing device 7 executed during cooling operation in the third modification of the first embodiment. Here, the processes in steps S41 to S45 are the same as those in steps S31 to S35 in FIG. 12, and therefore description thereof will not be repeated.

[0079] In cooling operation, if the capacity is insufficient, the pressure on the indoor unit side will rise. As a result, the detected pressure will be higher than the target pressure, and the pressure difference will be a negative (-) value. This relationship has the opposite sign to that in heating operation.

[0080] Therefore, during cooling operation, YES and NO in step S36 in Fig. 12 are interchanged. That is, in Fig. 13, if the absolute value of the pressure difference is greater than the third reference value and the pressure difference is a negative value (YES in S45 and YES in S46), the control device 100 increases the frequency of the compressor 1 in step S47. On the other hand, if the absolute value of the pressure difference is greater than the third reference value and the pressure difference is a positive value (YES in S45 and NO in S46), the control device 100 increases the opening degree of the second pressure reducing device 7 in step S48.

[0081] 12 and 13, if the indoor unit has insufficient capacity, increasing the frequency in step S37 or S47 (the frequency can be increased because it was at its minimum value) will supply an appropriate capacity that matches the load. Conversely, if the indoor unit has excessive capacity compared to the load, the opposite behavior will occur. In that case, the compressor frequency is already at its lower limit, so in step S38 or S48, control is performed to further increase the opening of the second pressure reducing device 7, thereby supplying an appropriate capacity that matches the load.

[0082] As described above, in the third modification of the first embodiment, the opening degree of the second pressure reducing device 7 and the frequency of the compressor 1 are adjusted in accordance with the load, and the operating state is stabilized, thereby making it possible to suppress a decrease in comfort.

[0083] Second Embodiment In a second embodiment, an example in which the indoor unit heat exchanger is divided in the flow direction will be described.

[0084] Fig. 14 is a refrigerant circuit diagram showing the configuration of a refrigeration cycle apparatus of embodiment 2. As shown in Fig. 14, a refrigeration cycle apparatus 1002 includes an indoor heat exchanger 250 instead of the indoor heat exchanger 150 in the configuration of the refrigeration cycle apparatus 1001 shown in Fig. 1.

[0085] The indoor heat exchange device 250 includes multiple indoor units 251-254. Each of the multiple indoor units 251-254 includes a first heat exchange unit 5A and a second heat exchange unit 5B connected in series, a second bypass flow path BP2 that bypasses the first heat exchange unit 5A, and a switching circuit 9 that changes the distribution of refrigerant flowing through the first heat exchange unit 5A and the second bypass flow path BP2. The control device 100 is configured to control the switching circuit 9 to bypass the first heat exchange unit when refrigerant is circulated through the second pressure reducing device 7. Each of the multiple indoor units 251-254 includes a fan 161, as in the case of FIG. 1, but this is not shown. The indoor units 251-254 may be located in different rooms or in the same room.

[0086] In each of the indoor units 251 to 254, the heat exchanger is divided into a first heat exchange unit 5A and a second heat exchange unit 5B in the flow direction. The switching circuit 9 is installed in a bypass flow path BP2 connected to the inlet / outlet of one of the divided heat exchangers. In Fig. 14, the bypass flow path BP2 is provided to bypass the first heat exchange unit 5A, but the bypass flow path BP2 may also be provided to bypass the second heat exchange unit 5B.

[0087] The second pressure reducing device 7 is controlled to open when the operating frequency of the compressor 1 reaches a specified value (for example, a lower limit frequency).

[0088] A sensor 55 that detects the operation mode is installed in the outdoor unit 61. The control device 100 detects whether the operation mode is cooling operation or heating operation based on the output of the sensor 55. The control device 100 is configured to control the switching circuit 9 so that the refrigerant flows through the bypass flow path BP2 when the operation mode is cooling operation and the second pressure reducing device 7 is open.

[0089] In addition, when the control device 100 mainly controls the four-way valve 2 based on the operation mode, the control device 100 may detect the operation mode without using the sensor 55.

[0090] 15 is a flowchart illustrating the control of the switching circuit executed in the second embodiment. First, in step S51, the control device 100 detects the operating frequency of the compressor 1. Then, in step S52, the control device 100 detects whether the operating frequency of the compressor 1 is at a specified value. The specified value in step S52 is a value corresponding to the lower limit frequency fmin in FIG. 2.

[0091] If the operating frequency of the compressor 1 is not the specified value (NO in S52), the control of this flowchart is terminated because if the air conditioning load is small, the operating frequency of the compressor can be lowered with the second pressure reducing device 7 closed.

[0092] On the other hand, if the operating frequency of the compressor 1 is at the specified value (YES in S52), the compressor 1 will undergo on-off operation unless the refrigerant is passed through the bypass flow path BP1. Therefore, in step S23, the control device 100 detects the number of operating indoor units using the operation detection unit 50, and then in step S54, the control device 100 detects the operation mode of the refrigeration cycle device based on the output of the sensor 55.

[0093] Next, in step S55, the control device 100 controls the opening degree of the second pressure reducing device based on the number of operating indoor units. For example, the control device 100 reduces the opening degree of the second pressure reducing device as the number of operating indoor units increases.

[0094] Thereafter, in step S56, the control device 100 determines whether the operation mode detected in step S54 is cooling operation. If the operation mode is cooling operation (YES in S56), the control device 100 controls the switching circuit 9 in step S57 to cause refrigerant to flow through the bypass flow path BP2. On the other hand, if the operation mode is not cooling operation (NO in S56), the control device 100 does not operate the switching circuit 9, and returns the process to step S51 with the bypass flow path BP2 kept blocked. Note that in step S56, it may be determined whether the operation mode is dehumidifying operation instead of cooling operation.

[0095] Generally, when the heat transfer performance of the indoor heat exchanger is high, the evaporation temperature becomes high in order to save energy, and dehumidification may not be possible. On the other hand, since it is necessary to demonstrate the rated capacity, the indoor heat exchanger needs to have a reasonably high heat transfer performance.

[0096] In contrast to this, in the second embodiment, the heat exchanger is divided, and during low capacity operation, the refrigerant is prevented from flowing through part of the heat exchanger by the switching circuit 9, which is equivalent to simply reducing the size of the heat exchanger. Because the heat transfer area of ​​the heat exchanger is reduced, it is possible to operate with a lower evaporation temperature even during low capacity operation, and the amount of dehumidification can be secured.

[0097] Modification of Second Embodiment In a modification of the second embodiment, a refrigeration cycle apparatus in which the indoor unit side heat exchanger is divided into parallel sections will be described.

[0098] Fig. 16 is a refrigerant circuit diagram showing the configuration of a refrigeration cycle apparatus according to a modification of Embodiment 2. As shown in Fig. 16, a refrigeration cycle apparatus 1002A includes an indoor heat exchanger 250A instead of the indoor heat exchanger 250 in the configuration of the refrigeration cycle apparatus 1002 shown in Fig. 14.

[0099] The indoor heat exchange device 250A includes multiple indoor units 251A to 254A. Each of the multiple indoor units 251A to 254A includes a first heat exchange unit 5X and a second heat exchange unit 5Y connected in parallel, and a switching circuit 9A that switches the state of the indoor heat exchange device 250 between a first state in which refrigerant flows through the first heat exchange unit 5X and the second heat exchange unit 5Y in parallel, and a second state in which refrigerant flows through the second heat exchange unit 5Y but not through the first heat exchange unit 5X. The control device 100 is configured to control the switching circuit 9A so that the indoor heat exchange device 250 is in the second state when refrigerant is circulated through the second pressure reducing device 7. Specifically, the switching circuit 9A is an on-off valve or a flow rate adjustment valve provided in the flow path in which the first heat exchange unit 5X is located, of two branched flow paths that branch at a branch point and merge at a junction point in the indoor unit 251A.

[0100] Each of the multiple indoor units 251A to 254A includes a fan 161, similar to the case of Fig. 1, but this is not shown. The indoor units 251A to 254A may be placed in different rooms or in the same room.

[0101] The second pressure reducing device 7 is controlled to open when the operating frequency of the compressor 1 reaches a specified value (for example, a lower limit frequency).

[0102] A sensor 55 that detects the operation mode is installed in the outdoor unit 61. The control device 100 detects whether the operation mode is cooling operation or heating operation based on the output of the sensor 55. When the operation mode is cooling operation (or dehumidifying operation) and the second pressure reducing device 7 is open, the control device 100 is configured to control the switching circuit 9A to achieve a second state in which refrigerant does not flow through the first heat exchange unit 5X but flows through the second heat exchange unit 5Y.

[0103] In addition, when the control device 100 mainly controls the four-way valve 2 based on the operation mode, the control device 100 may detect the operation mode without using the sensor 55.

[0104] The details of the control of second pressure reducing device 7 and switching circuit 9A are substantially the same as those in FIG. 15, and therefore will not be described again here.

[0105] In the modified example of the second embodiment, the heat exchanger is divided, and during low-capacity operation, the switching circuit 9A prevents refrigerant from flowing through part of the heat exchanger, thus simply reducing the size of the heat exchanger. Because the heat transfer area of ​​the heat exchanger is reduced, it is possible to operate with a lower evaporation temperature even during low-capacity operation, ensuring a sufficient dehumidification amount.

[0106] (Summary) (1) The refrigeration cycle apparatus of the present disclosure includes a refrigerant circuit C1 including a compressor 1, an outdoor heat exchange device 3, a first pressure reducing device 4, and an indoor heat exchange device 150, through which a refrigerant circulates, a first bypass flow path BP1 connected in parallel to the compressor 1 in the refrigerant circuit C1, a second pressure reducing device 7 provided in the first bypass flow path BP1 and configured to have a changeable opening degree, and a control device 100 that controls the refrigerant circuit C1 and the second pressure reducing device 7. The control device 100 is configured to change the opening degree of the second pressure reducing device 7 in accordance with the heat exchange capacity of the indoor heat exchange device 150.

[0107] (2) In the refrigeration cycle apparatus of paragraph 1, each of the indoor units 151 to 154 of the indoor heat exchanger 150 includes a plurality of indoor heat exchangers 5 connected in parallel. Each of the plurality of indoor heat exchangers 5 is configured to be able to switch between an operating state and a stopped state. As shown in Fig. 3 , the control device 100 is configured to change the opening degree of the second pressure reducing device 7 based on the number of operating heat exchangers among the plurality of indoor heat exchangers 5.

[0108] (3) The refrigeration cycle apparatus of paragraph 1 further includes a fan 161 that blows indoor air to the indoor heat exchanger 150. The control device 100 is configured to change the opening degree of the second pressure reducing device 7 based on the air volume of the fan 161.

[0109] (4) In the refrigeration cycle device of paragraph 1, the control device 100 is configured to change the opening degree of the second pressure reducing device 7 based on the temperature difference between the ambient temperature of the indoor heat exchange device 150 and the ambient temperature of the outdoor heat exchange device 3, as shown in FIG. 6 .

[0110] (5) In the refrigeration cycle apparatus of the first aspect, the control device 100 is configured to change the opening degree of the second pressure reducing device 7 in response to a change in the density of the refrigerant sucked into the compressor 1, as shown in FIG.

[0111] (6) The refrigeration cycle apparatus of paragraph 1 further includes a sensor 53 for detecting the refrigerant pressure of the indoor heat exchanger 150C, as shown in Fig. 11. The control device 100 is configured to calculate the pressure difference between the pressure detected by the sensor 53 and the target pressure when the second pressure reducing device 7 is open, and to increase or decrease the frequency of the compressor 1 based on the pressure difference.

[0112] (7) In the refrigeration cycle apparatus of paragraph 1, as shown in Fig. 14, each of the indoor units 251 to 254 in the indoor heat exchanger 250 includes a first heat exchanger unit 5A and a second heat exchanger unit 5B connected in series, a second bypass flow path BP2 that bypasses the first heat exchanger unit 5A, and a switching circuit 9 that changes the distribution of refrigerant flowing through the first heat exchanger unit 5A and the second bypass flow path BP2. The control device 100 is configured to control the switching circuit 9 to bypass the first heat exchanger unit 5A when refrigerant is circulated through the second pressure reducing device 7.

[0113] (8) In the refrigeration cycle apparatus of paragraph 1, as shown in Fig. 16, each of the indoor units 251A to 254A in the indoor heat exchanger 250A includes a first heat exchanger unit 5X and a second heat exchanger unit 5Y connected in parallel, and a switching circuit 9A that switches the state of the indoor heat exchanger 250 between a first state in which a refrigerant flows through the first heat exchanger unit 5X and the second heat exchanger unit 5Y in parallel, and a second state in which a refrigerant flows through the second heat exchanger unit 5Y without flowing through the first heat exchanger unit 5X. The control device 100 is configured to control the switching circuit 9A so that the indoor heat exchanger 250 is in the second state when a refrigerant is circulated through the second pressure reducing device 7.

[0114] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the description of the above embodiments, and is intended to include all modifications within the meaning and scope of the claims.

[0115] 1 Compressor, 2 Four-way valve, 3 Outdoor heat exchange device, 4 First pressure reducing device, 5 Indoor heat exchanger, 5A, 5X First heat exchange unit, 5B, 5Y Second heat exchange unit, 6 Branching section, 7 Second pressure reducing device, 8 Junction section, 9, 9A Switching circuit, 41, 44 Expansion valve, 50 Operation detection unit, 51, 52 Temperature sensor, 53, 54, 55 Sensor, 61 Outdoor unit, 62 Branching-junction section, 63 Indoor air conditioner, 64, 65 Extension piping, 100 Control device, 101 CPU, 102 Memory, 150, 150A, 150B, 150C, 250, 250A Indoor heat exchanger, 151, 151A, 151B, 151C, 154, 154A, 154B, 154C, 251, 251A, 254, 254A indoor unit, 161 fan, 1001, 1001A, 1001B, 1001C, 1002, 1002A refrigeration cycle device, BP1, BP2 bypass flow path, C1 refrigerant circuit.

Claims

1. A refrigeration cycle apparatus comprising: a refrigerant circuit including a compressor, an outdoor heat exchange device, a first pressure reducing device, and an indoor heat exchange device, through which a refrigerant circulates; a first bypass flow path in the refrigerant circuit connected in parallel to the compressor; a second pressure reducing device provided in the first bypass flow path and configured to change its opening; and a control device that controls the refrigerant circuit and the second pressure reducing device, wherein the control device is configured to change the opening of the second pressure reducing device in accordance with the heat exchange capacity of the indoor heat exchange device.

2. The refrigeration cycle apparatus of claim 1, wherein the indoor heat exchange device includes a plurality of indoor heat exchangers connected in parallel, each of the plurality of indoor heat exchangers is configured to be able to switch its state between an operating state and a stopped state, and the control device is configured to change the opening degree of the second pressure reducing device based on the number of heat exchangers that are in an operating state among the plurality of indoor heat exchangers.

3. A refrigeration cycle apparatus as described in claim 1, further comprising a fan for blowing indoor air to the indoor heat exchange device, and the control device is configured to change the opening degree of the second pressure reducing device based on the air volume of the fan.

4. A refrigeration cycle apparatus as described in claim 1, wherein the control device is configured to change the opening degree of the second pressure reducing device based on the temperature difference between the ambient temperature of the indoor heat exchange device and the ambient temperature of the outdoor heat exchange device.

5. The refrigeration cycle apparatus according to claim 1, wherein the control device is configured to change the opening degree of the second pressure reducing device in response to a change in density of the refrigerant sucked into the compressor.

6. A refrigeration cycle apparatus as described in claim 1, further comprising a sensor for detecting a refrigerant pressure of the indoor heat exchanger, wherein the control device is configured to calculate a pressure difference between the pressure detected by the sensor and a target pressure when the second pressure reducing device is open, and to increase or decrease the frequency of the compressor based on the pressure difference.

7. The refrigeration cycle apparatus of claim 1, wherein the indoor heat exchange device comprises a first heat exchange unit and a second heat exchange unit connected in series, a second bypass flow path that bypasses the first heat exchange unit, and a switching circuit that changes the distribution of refrigerant flowing through the first heat exchange unit and the second bypass flow path, and the control device is configured to control the switching circuit so as to bypass the first heat exchange unit when refrigerant is circulated through the second pressure reducing device.

8. The refrigeration cycle apparatus of claim 1, wherein the indoor heat exchange device comprises a first heat exchange unit and a second heat exchange unit connected in parallel, and a switching circuit that switches the state of the indoor heat exchange device between a first state in which a refrigerant flows in parallel through the first heat exchange unit and the second heat exchange unit, and a second state in which a refrigerant flows through the second heat exchange unit without flowing through the first heat exchange unit, and the control device is configured to control the switching circuit so that the indoor heat exchange device is in the second state when a refrigerant is circulated through the second pressure reducing device.

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