Air conditioner

Abstract

An air conditioner 1 that uses R32 as a refrigerant is provided with an outdoor unit (100), a dehumidification reheating indoor unit (200), a first connection pipe (P1), a second connection pipe (P2), and a third connection pipe (P3). The first connection pipe (P1) connects a refrigerant outlet of an outdoor heat exchanger (12) during the dehumidification operation and a first expansion valve (V5). The second connection pipe (P2) connects a refrigerant outlet of a first utilization heat exchanger (21) during the dehumidification operation and a suction pipe (P9). The third connection pipe (P3) connects a discharge pipe (P0) and a refrigerant inlet of a second utilization heat exchanger (22) in the dehumidification operation. In the dehumidification operation, the refrigerant that has flowed from the discharge pipe (P0) through the third connection pipe (P3) into the second utilization heat exchanger (22) is condensed in the second utilization heat exchanger (22), merges with the refrigerant that has been condensed by the outdoor heat exchanger (12) and has flowed through the first connection pipe (P1) to the dehumidification reheating indoor unit (200), and evaporates in the first utilization heat exchanger (21).

Description

air conditioner

[0001] This relates to an air conditioner that uses R32 as a refrigerant.

[0002] Air conditioners that use R32 as a refrigerant have been proposed. For example, Patent Document 1 (JP 2014-1917 A) discloses a multi-type air conditioner that uses R32 as a refrigerant, which has a lower global warming potential (GWP) than R410A. This multi-type air conditioner is a vapor compression air conditioner in which multiple utilization units are connected to a heat source unit, and it conditions the air of multiple spaces in a building such as an office building.

[0003] Some of the utilization units of the multi-type air conditioners for buildings mentioned above have not only a mode for heating and cooling the indoor space, but also a dry mode for dehumidifying the indoor space. The dehumidification method generally involves lowering the evaporation temperature of the utilization heat exchanger below the dew point of the air to remove moisture from the air.

[0004] However, the more the evaporation temperature of the heat exchanger is lowered to increase the dehumidification effect, the lower the indoor air temperature becomes, so dehumidification operation reduces the comfort of the indoor space.For this reason, dehumidification operation is currently performed at a reduced capacity to prevent the indoor temperature from dropping too much, and the dehumidification capacity of multi-type air conditioners for buildings in dry mode is small.

[0005] On the other hand, when considering installing a multi-type air conditioner in a home, it is expected that a small dehumidification capacity will not be enough. In homes, there are spaces such as bathrooms and kitchens where humidity levels are high due to the use of hot water, and since residents use these high-humidity spaces every day, an air conditioner with high dehumidification capacity is required. Furthermore, in spaces such as bathrooms, it is necessary not only to have dehumidifying capacity, but also to prevent the air temperature from dropping too low.

[0006] As described above, conventional air conditioners that use R32 as a refrigerant have the problem of insufficient dehumidifying capacity or excessively low indoor temperatures.

[0007] An air conditioner according to a first aspect is an air conditioner that uses R32 as a refrigerant and performs dehumidifying operation, and includes a heat source unit, a first usage unit, a first connecting pipe, a second connecting pipe, and a third connecting pipe. The heat source unit includes a compressor, a discharge pipe, a suction pipe, and a heat source heat exchanger. Refrigerant discharged from the compressor flows through the discharge pipe. Refrigerant drawn into the compressor flows through the suction pipe. In dehumidifying operation, the refrigerant flows from the discharge pipe into the heat source heat exchanger. The first usage unit includes a first usage heat exchanger, a first expansion device, and a second usage heat exchanger. The first usage heat exchanger functions as an evaporator in dehumidifying operation. The first expansion device expands the refrigerant before it flows into the first usage heat exchanger in dehumidifying operation. The second usage heat exchanger functions as a condenser in dehumidifying operation. The first connecting pipe connects a refrigerant outlet of the heat source heat exchanger in dehumidifying operation to the first expansion device. The second connecting pipe connects the refrigerant outlet of the first utilization heat exchanger to the suction pipe in dehumidifying operation. The third connecting pipe connects the discharge pipe to the refrigerant inlet of the second utilization heat exchanger in dehumidifying operation. In this air conditioner, during dehumidifying operation, the refrigerant that flows from the discharge pipe through the third connecting pipe to the second utilization heat exchanger condenses in the second utilization heat exchanger, joins with the refrigerant that was condensed in the heat source heat exchanger and flowed to the first utilization unit through the first connecting pipe, and evaporates in the first utilization heat exchanger.

[0008] Because the air conditioner of the first aspect uses R32 as a refrigerant, it can achieve a higher dehumidifying capacity than an air conditioner using R410A, even with the same refrigerant circulation volume. Furthermore, the air conditioner of the first aspect is provided with three connecting pipes, namely, a first connecting pipe, a second connecting pipe, and a third connecting pipe, and during dehumidifying operation, the third connecting pipe flows refrigerant from the discharge pipe of the heat source unit to the second utilization heat exchanger of the first utilization unit. This allows the refrigerant to condense in the second utilization heat exchanger to warm the air while evaporating to dehumidify the air in the first utilization heat exchanger of the first utilization unit, thereby raising the air temperature that would otherwise drop due to dehumidification. In this way, the air conditioner of the first aspect can prevent problems such as insufficient dehumidifying capacity or excessive drops in indoor temperature.

[0009] An air conditioner according to a second aspect is the air conditioner according to the first aspect, further comprising a second usage unit separate from the first usage unit. The first usage unit is installed in a bathroom or kitchen, which is a space in the house where hot water is used.

[0010] Homes often have bathrooms where humidity tends to be high due to the use of hot water in showers or bathtubs, and kitchens where hot water is used for cooking (such as separate kitchens or kitchens located in a corner of the living room). While these spaces require high dehumidifying capacity, they also need to prevent excessive drops in air temperature during dehumidifying operation to prevent heat shock in the bathroom and to suppress temperature drops in the living room. The air conditioner of the second aspect is the same as the air conditioner of the first aspect, and therefore uses R32 as a refrigerant, enabling high dehumidifying capacity, and the air temperature that drops due to dehumidification can be raised by the second utilization heat exchanger. Thus, the first utilization unit of the air conditioner of the second aspect is suitable for dehumidifying a bathroom or kitchen.

[0011] The second usage unit may have the same configuration as the first usage unit or a different configuration, but for spaces where a slight drop in temperature is acceptable, such as a hallway, a second usage unit without a second usage heat exchanger may be used.

[0012] An air conditioner according to a third aspect is the air conditioner according to the first or second aspect, wherein the first utilization unit further has a second expansion device corresponding to the second utilization heat exchanger.

[0013] Here, in addition to a first expansion device that expands the refrigerant before it flows into the first utilization heat exchanger, a second expansion device corresponding to the second utilization heat exchanger is also provided, making it possible to adjust the amount of refrigerant flowing through the first utilization heat exchanger and the second utilization heat exchanger.

[0014] An air conditioner according to a fourth aspect is the air conditioner according to any one of the first to third aspects, further comprising a control unit that controls the compressor and the first expansion device during dehumidification operation. The heat source unit further comprises a pressure sensor that detects the pressure of the refrigerant. During dehumidification operation, the control unit controls the compressor and the first expansion device based on the value detected by the pressure sensor so that the evaporation temperature of the refrigerant in the first utilization heat exchanger is lower than the dew point of the air to be dehumidified.

[0015] Because the air conditioner of the fourth aspect uses R32 as the refrigerant, the refrigerant circulation volume per unit capacity is smaller than that of an air conditioner using R410A. Therefore, even if the evaporation temperature of the refrigerant in the first utilization heat exchanger of the first utilization unit, which is separate from the heat source unit, is estimated using the refrigerant pressure detected by a pressure sensor included in the heat source unit, the accuracy of the estimation of the evaporation temperature is high. This is because, even if the connecting pipe is somewhat long, if the refrigerant circulation volume is small, the refrigerant pressure loss is small. In light of this, the control unit of the air conditioner of the fourth aspect controls the compressor and the first expansion device based on the detected value of the pressure sensor. This eliminates the need to provide a temperature sensor for measuring the evaporation temperature in the first utilization heat exchanger of the first utilization unit, thereby reducing manufacturing costs.

[0016] Fig. 1 is a refrigerant circuit diagram of an air conditioner according to a first embodiment. Fig. 2 is a control block diagram of an air conditioner. Fig. 3 is a refrigerant circuit diagram of an air conditioner according to a second embodiment. Fig. 4 is a refrigerant circuit diagram of an air conditioner according to a third embodiment. Fig. 5 is a refrigerant circuit diagram of an air conditioner according to a fourth embodiment. Fig. 6 is a refrigerant circuit diagram of an air conditioner according to another embodiment.

[0017] <First Embodiment> (1) Configuration of Air Conditioner An air conditioner 1 according to a first embodiment will be described with reference to FIG. 1 . The air conditioner 1 includes an outdoor unit 100 and a dehumidification / reheating indoor unit 200. The outdoor unit 100, which is a heat source unit of the air conditioner 1, includes a compressor 11, an outdoor heat exchanger 12, an outdoor fan 13, an outdoor expansion valve V2, and an accumulator 14. The dehumidification / reheating indoor unit 200, which is a utilization unit of the air conditioner 1, includes a first utilization heat exchanger 21, which is a first indoor heat exchanger, a second utilization heat exchanger 22, which is a second indoor heat exchanger, and a first expansion valve V5, which serves as a first expansion device. The first utilization heat exchanger 21 functions as an evaporator in the dehumidification operation described below. The first expansion valve V5 expands the refrigerant before it flows into the first utilization heat exchanger 21 in the dehumidification operation. An electric valve or a solenoid valve can be used as the first expansion valve V5. The second utilization heat exchanger 22 functions as a condenser in the dehumidification operation.

[0018] The air conditioner 1 is a refrigeration cycle device developed for installation in a home. The outdoor unit 100 is installed outdoors, such as on a balcony or in a garden. The dehumidifying and reheating indoor unit 200 is installed in a bathroom or kitchen, which are spaces in the home where hot water is used.

[0019] In the air conditioner 1, a dehumidification circuit is formed by connecting the compressor 11, outdoor heat exchanger 12, outdoor expansion valve V2, first expansion valve V5, first utilization heat exchanger 21, accumulator 14, and compressor 11 in this order with piping. The air conditioner 1 is equipped with the following piping: a discharge pipe P0 connected to a refrigerant discharge portion of the compressor 11, a first connecting pipe P1, a second connecting pipe P2, and a suction pipe P9 connected to a refrigerant suction portion of the compressor 11.

[0020] The refrigerant discharged from the compressor 11 flows through a discharge pipe P0. The refrigerant drawn into the compressor 11 flows through a suction pipe P9. During a dehumidifying operation, which will be described later, the refrigerant flows from the discharge pipe P0 into the outdoor heat exchanger 12, which is a heat source heat exchanger.

[0021] The first connecting pipe P1 connects the refrigerant outlet of the outdoor heat exchanger 12 to the first expansion valve V5 during dehumidification operation. Specifically, the first connecting pipe P1 sequentially connects the discharge pipe P0, the outdoor heat exchanger 12, the outdoor expansion valve V2, the first expansion valve V5, and the first utilization heat exchanger 21.

[0022] The second connecting pipe P2 connects the refrigerant outlet of the first utilization heat exchanger 21 and the suction pipe P9 during the dehumidification operation. Specifically, the second connecting pipe P2 connects the first utilization heat exchanger 21 and the suction pipe P9.

[0023] Here, the section from the discharge side of the compressor 11 to point K0 in Figure 1 is defined as a discharge pipe P0. The section from point K0 in Figure 1 to the upstream end of the first utilization heat exchanger 21 in the refrigerant flow direction (see the dashed arrow in Figure 1) is defined as part of the first connecting pipe P1. The section from the downstream end of the first utilization heat exchanger 21 in the refrigerant flow direction to point K1 in Figure 1 is defined as a second connecting pipe P2. The section from point K1 in Figure 1 to the suction side of the compressor 11 is defined as a suction pipe P9. The accumulator 14 is provided midway through the suction pipe P9.

[0024] The dehumidification and reheating indoor unit 200 of the air conditioner 1 not only has a first utilization heat exchanger 21 and a first expansion valve V5, but also has a second utilization heat exchanger 22, an indoor fan 23 serving as a blower, and a second expansion valve V6 serving as a second expansion device. An electric valve or a solenoid valve can be used as the second expansion valve V6. The first utilization heat exchanger 21 and the second utilization heat exchanger 22 are disposed in the air flow path formed by the indoor fan 23. The first utilization heat exchanger 21 is provided upstream of the second utilization heat exchanger 22 in the air flow path formed by the indoor fan 23.

[0025] In the air conditioner 1, a reheat circuit is formed by connecting, in order, a midpoint of the discharge pipe P0, the second utilization heat exchanger 22, the second expansion valve V6, and a midpoint of the first connecting pipe P1. The air conditioner 1 further includes, as piping, a branch pipe P4 and a third connecting pipe P3 connected in series.

[0026] During dehumidification operation, which will be described later, the third connecting pipe P3 connects the discharge pipe P0 to the refrigerant inlet of the second utilization heat exchanger 22 via the branch pipe P4. Specifically, the third connecting pipe P3 sequentially connects the branch pipe P4, the second utilization heat exchanger 22, the second expansion valve V6, and intermediate positions of the first connecting pipe P1. The branch pipe P4 is a pipe branched from an intermediate position of the discharge pipe P0. The branch pipe P4 branches off at point K2 in FIG. 1 and extends to point K4 in FIG. 1. The third connecting pipe P3 extends from point K4 in FIG. 1 to point K5 in FIG. 1, which is located between the outdoor expansion valve V2 and the first expansion valve V5.

[0027] Both the dehumidification circuit and the reheat circuit of the air conditioner 1 are part of a single refrigerant circuit through which a refrigerant circulates. The refrigerant circuit of the air conditioner 1 contains a single refrigerant, R32. Here, a refrigerant containing 99% by weight or more, preferably 99.5% or more, of R32 is referred to as a single R32 refrigerant. Because this refrigerant is used, the air conditioner 1 can achieve the same capacity as air conditioners using the widely used R410A, even with a refrigerant circulation volume that is 20% or more less.

[0028] The air conditioner 1 further includes a control unit 50 shown in FIG. 2 . The control unit 50 is configured by connecting an outdoor control unit 50a disposed in the outdoor unit 100 and an indoor control unit 50b disposed in the dehumidification / reheat indoor unit 200 via communication lines. The control unit 50 controls the operation of components such as the compressor 11, the outdoor fan 13, the outdoor expansion valve V2, the indoor fan 23, the first expansion valve V5, and the second expansion valve V6. The control unit 50 is also connected to a discharge pressure sensor 51 that detects the pressure of the refrigerant flowing through the discharge pipe P0, a suction pressure sensor 52 that detects the pressure of the refrigerant flowing through the suction pipe P9, and multiple temperature sensors that detect the temperature of the refrigerant. Based on the values ​​detected by these sensors, the control unit 50 controls the operation of each component in a dehumidification / reheat operation mode in which dehumidification is performed, for example.

[0029] (2) Dehumidification operation in dehumidification reheat operation mode During dehumidification operation, the refrigerant that flows from the discharge pipe through the third connecting pipe into the second utilization heat exchanger condenses in the second utilization heat exchanger, merges with the refrigerant that has been condensed in the heat source heat exchanger and flowed to the first utilization unit through the first connecting pipe, and evaporates in the first utilization heat exchanger.

[0030] Next, the dehumidifying operation in the dehumidifying reheat operation mode by the air conditioner 1 will be described.

[0031] In the dehumidification and reheat operation mode, a portion of the refrigerant compressed and discharged by the compressor 11 is transported to the outdoor heat exchanger 12, while the other portion of the refrigerant compressed and discharged by the compressor 11 flows to the second utilization heat exchanger 22 of the dehumidification and reheat indoor unit 200. The refrigerant transported to the outdoor heat exchanger 12 exchanges heat with outdoor air taken in by the outdoor fan 13 in the outdoor heat exchanger 12, condenses, and then passes through the outdoor expansion valve V2 and the first connecting pipe P1 into the dehumidification and reheat indoor unit 200. Meanwhile, the refrigerant that enters the second utilization heat exchanger 22 of the dehumidification and reheat indoor unit 200 through the discharge pipe P0 and the third connecting pipe P3 exchanges heat with indoor air taken in by the indoor fan 23 in the second utilization heat exchanger 22, condenses, and heats the indoor air. This heating of the indoor air is the heating of the indoor air that has been cooled and dehumidified in the first utilization heat exchanger 21, which will be described later, and is therefore sometimes referred to as reheating the indoor air.

[0032] The refrigerant after exchanging heat with the indoor air in the second utilization heat exchanger 22 passes through the second expansion valve V6 and merges with the refrigerant that entered the dehumidification / reheat indoor unit 200 from the outdoor unit 100 through the first connecting pipe P1 at point K5 in FIG. 1 . The merged refrigerant passes through the first expansion valve V5 of the dehumidification / reheat indoor unit 200 and enters the first utilization heat exchanger 21. The refrigerant that entered the first utilization heat exchanger 21 exchanges heat with indoor air taken in by the indoor fan 23 in the first utilization heat exchanger 21, thereby dehumidifying the indoor air. This dehumidification of the indoor air is achieved by cooling the indoor air to a temperature below the dew point and causing condensation, so more accurately, it refers to the cooling and dehumidification of the indoor air. The refrigerant after exchanging heat with the indoor air in the first utilization heat exchanger 21 flows through the second connecting pipe P2 to the outdoor unit 100, passes through the accumulator 14, and returns to the compressor 11.

[0033] Next, control of the evaporation temperature of the first utilization heat exchanger 21 during dehumidification operation will be described. As described above, during dehumidification operation, indoor air passing through the first utilization heat exchanger 21 is cooled to a temperature below the dew point, and moisture in the indoor air is condensed on the surface of the first utilization heat exchanger 21, thereby performing dehumidification. Here, in order to bring the indoor humidity closer to the set humidity, the control unit 50 determines a target value for the evaporation temperature, which is the temperature of the refrigerant flowing through the first utilization heat exchanger 21, and controls the inverter frequency of the compressor 11 and the opening degree of the first expansion valve V5 so that the evaporation temperature approaches the target value. Specifically, during dehumidification operation in the dehumidification reheat operation mode, the control unit 50 calculates the evaporation temperature of the refrigerant in the first utilization heat exchanger 21 from the refrigerant pressure, which is the value detected by the suction pressure sensor 52, and controls the compressor 11 and the first expansion valve V5 so that the evaporation temperature approaches the target value.

[0034] (3) Features of the Air Conditioner (3-1) Because the air conditioner 1 of this embodiment uses a single refrigerant, R32, it can achieve higher dehumidification capacity than conventional air conditioners that use R410A as a refrigerant, even with the same refrigerant circulation volume. Furthermore, the air conditioner 1 is provided with three connecting pipes: a first connecting pipe P1, a second connecting pipe P2, and a third connecting pipe P3. During dehumidification operation, the refrigerant flows from the discharge pipe P0 of the outdoor unit 100 to the second utilization heat exchanger 22 of the dehumidification / reheat indoor unit 200 via the third connecting pipe P3. As a result, while the refrigerant evaporates to dehumidify the air in the first utilization heat exchanger 21 of the dehumidification / reheat indoor unit 200, the refrigerant condenses in the second utilization heat exchanger 22 to warm the air, thereby raising the air temperature that would otherwise be lowered by dehumidification. In this way, in the air conditioner 1, indoor air can be reheated in the second utilization heat exchanger 22 of the dehumidification / reheat indoor unit 200, thereby preventing the indoor temperature from dropping too low.

[0035] (3-2) The air conditioner 1 of this embodiment was developed assuming installation in a home. Homes often have bathrooms that tend to be humid because people use hot water in showers or bathtubs, and kitchens where hot water is used for cooking. While these spaces require high dehumidifying capacity, they also need to prevent excessive temperature drops during dehumidifying operation in order to prevent heat shock in the bathroom and to prevent temperature drops in the living room.

[0036] As described above, the air conditioner 1 of this embodiment uses a single refrigerant, R32, to achieve high dehumidification capacity. Furthermore, the dehumidification / reheat indoor unit 200 of the air conditioner 1 includes not only a first heat utilization exchanger 21 that performs dehumidification during dehumidification operation, but also a second heat utilization exchanger 22 that performs reheating during dehumidification operation. In the air conditioner 1, reheating is performed by flowing high-temperature refrigerant from the discharge pipe P0 of the outdoor unit 100 to the second heat utilization heat exchanger 22 of the dehumidification / reheat indoor unit 200 via the third connecting pipe P3. This allows for high-performance dehumidification of the bathroom or kitchen while preventing the bathroom or kitchen from becoming too cold.

[0037] (3-3) The dehumidification and reheating indoor unit 200 of the air conditioner 1 of this embodiment is provided with not only a first expansion valve V5 corresponding to the first utilization heat exchanger 21, but also a second expansion valve V6 corresponding to the second utilization heat exchanger 22. This makes it possible for the air conditioner 1 to adjust the amount of refrigerant flowing through the first utilization heat exchanger 21 and the amount of refrigerant flowing through the second utilization heat exchanger 22. This makes it possible for the air conditioner 1 to appropriately and accurately control the dehumidification capacity and reheating capacity according to the set temperature and set humidity.

[0038] (3-4) As described above, the air conditioner 1 of this embodiment uses R32 as the refrigerant, and therefore the amount of refrigerant circulating per unit capacity is smaller than in air conditioners that use R410A. Furthermore, in the air conditioner 1 of this embodiment, even if the outdoor unit 100 and the dehumidification / reheating indoor unit 200 are far apart and the first connecting pipe P1, second connecting pipe P2, and third connecting pipe P3 are long, the amount of refrigerant circulating is small, so the pressure loss of the refrigerant flowing through the refrigerant piping is small. If the pressure loss of the refrigerant is small, there is no significant difference between the refrigerant pressure in the suction pipe P9 of the outdoor unit 100 and the refrigerant pressure in the first utilization heat exchanger 21 of the dehumidification / reheating indoor unit 200.

[0039] In consideration of this, the control unit 50 of the air conditioner 1 calculates (estimates) the evaporation temperature of the refrigerant in the first utilization heat exchanger 21 of the dehumidification and reheat indoor unit 200, which is located indoors away from the outdoor unit 100, using the pressure detection value of the suction pressure sensor 52 of the outdoor unit 100. Even when the evaporation temperature of the refrigerant in the first utilization heat exchanger 21 is calculated in this way, a highly accurate estimated value of the evaporation temperature can be obtained, so in the air conditioner 1, there is no need to install a temperature sensor that directly measures the refrigerant temperature in the first utilization heat exchanger 21, thereby reducing manufacturing costs.

[0040] <Second embodiment> Fig. 3 shows an air conditioner 1A according to a second embodiment. The structure of the air conditioner 1A of this embodiment overlaps with that of the air conditioner 1 of the first embodiment. Therefore, the same components as those of the first embodiment are denoted by the same reference numerals, and only the differences from the first embodiment will be described here.

[0041] As shown in Fig. 3, the outdoor unit 100A further includes a four-way selector valve V1. The four-way selector valve V1 connects the discharge pipe P0, the first connecting pipe P1, the second connecting pipe P2, and the suction pipe P9, and is switchable between a first and a second switching state. In the first switching state, the four-way selector valve V1 connects the first connecting pipe P1 to the suction pipe P9 and also connects the second connecting pipe P2 to the discharge pipe P0. In the second switching state, the four-way selector valve V1 connects the first connecting pipe P1 to the discharge pipe P0 and also connects the second connecting pipe P2 to the suction pipe P9. In the air conditioner 1A, the four-way switching valve V1 of the outdoor unit 100A can be switched to a first switching state to operate in heating mode, and the four-way switching valve V1 of the outdoor unit 100A can be switched to a second switching state to operate in dehumidification reheat mode.

[0042] The dehumidifying operation performed by the air conditioner 1A in the dehumidifying reheat mode is the same as the dehumidifying operation performed by the air conditioner 1 of the first embodiment, and therefore a description thereof will be omitted here. Hereinafter, the operation in the heating mode performed by the air conditioner 1A of this embodiment will be described with reference to Fig. 3 .

[0043] In the heating mode, the control unit of the air conditioner 1A sets the four-way switching valve V1 of the outdoor unit 100A to a first switching state. In this state, a portion of the refrigerant discharged from the compressor 11 flows to the first utilization heat exchanger 21 of the dehumidification / reheat indoor unit 200, and the other portion of the refrigerant flows to the second utilization heat exchanger 22 of the dehumidification / reheat indoor unit 200. The refrigerant that flows into the first utilization heat exchanger 21 of the dehumidification / reheat indoor unit 200 exchanges heat with indoor air taken in by the indoor fan 23 in the first utilization heat exchanger 21, thereby heating the indoor air. After exchanging heat with the indoor air in the first utilization heat exchanger 21, the refrigerant passes through the first expansion valve V5. Meanwhile, the refrigerant that flows into the second utilization heat exchanger 22 of the dehumidification / reheat indoor unit 200 exchanges heat with indoor air taken in by the indoor fan 23 in the second utilization heat exchanger 22, thereby heating the indoor air. After exchanging heat with the indoor air in the second utilization heat exchanger 22, the refrigerant passes through the second expansion valve V6.

[0044] The refrigerant that has passed through the first expansion valve V5 and the refrigerant that has passed through the second expansion valve V6 join together and flow through the first connecting pipe P1 toward the outdoor unit 100A. The refrigerant that has passed through the outdoor expansion valve V2 of the outdoor unit 100A flows into the outdoor heat exchanger 12, where it exchanges heat with outdoor air taken in by the outdoor fan 13 and evaporates. The refrigerant that has evaporated in the outdoor heat exchanger 12 returns to the compressor 11 via the accumulator 14.

[0045] According to the air conditioner 1A of this embodiment, by setting the four-way switching valve V1 of the outdoor unit 100A to the first switching state, both the first utilization heat exchanger 21 and the second utilization heat exchanger 22 can function as condensers, and the indoor air can be heated (spaced) with high capacity.

[0046] Furthermore, according to the air conditioner 1A of this embodiment, by switching the four-way switching valve V1 of the outdoor unit 100A to the second switching state, dehumidification operation in the dehumidification reheat mode can be performed, as in the first embodiment.

[0047] <Third embodiment> Fig. 4 shows an air conditioner 1B according to a third embodiment. The structure of the air conditioner 1B of this embodiment overlaps with that of the air conditioner 1A of the second embodiment. Therefore, the same components as those of the second embodiment are denoted by the same reference numerals, and only the differences from the second embodiment will be described here.

[0048] As shown in FIG. 4 , the outdoor unit 100B of the air conditioner 1B further includes a branch pipe P5, a branch pipe P6, a throttle V4, and a four-way selector valve V3. The branch pipe P5 branches off from the suction pipe P9 at point K6 in FIG. 4 . The branch pipe P6 branches off from the branch pipe P5 at point K3 in FIG. 4 . The throttle V4 is provided on the branch pipe P6. The four-way selector valve V3 connects the third connecting pipe P3, the branch pipe P4, the branch pipe P5, and the branch pipe P6, and switches between a first switching state and a second switching state. In the first switching state, the four-way selector valve V3 connects the third connecting pipe P3 and the branch pipe P4, and also connects the branch pipe P5 and the branch pipe P6, forming a loop circuit. In the second switching state, the four-way selector valve V3 connects the third connecting pipe P3 to the branch pipe P5 and also connects the branch pipe P4 to the branch pipe P6. By introducing oil accumulated in the four-way selector valve V3 into the circuit for separation and recovery, it is possible to prevent the four-way selector valve V3 from failing due to oil accumulation. To prevent this, the throttle V4 is preferably a capillary tube.

[0049] The air conditioner 1B of this embodiment can be switched among a first mode, a second mode, a third mode, and a fourth mode by a control unit. In the first mode, the four-way switching valve V1 is switched to a first switching state, and the four-way switching valve V3 is switched to a first switching state. In the second mode, the four-way switching valve V1 is switched to a second switching state, and the four-way switching valve V3 is switched to a second switching state. In the third mode, the four-way switching valve V1 is switched to a second switching state, and the four-way switching valve V3 is switched to a first switching state. In the fourth mode, the four-way switching valve V1 is switched to a second switching state, and the four-way switching valve V3 is switched to a second switching state, and operation of the indoor fan 23 is stopped.

[0050] The operation performed by the air conditioner 1B of this embodiment in the first mode is the same as the operation in the heating mode by the air conditioner 1A of the second embodiment. The operation performed by the air conditioner 1B of this embodiment in the third mode is the same as the dehumidification operation in the dehumidification reheat mode by the air conditioner 1A of the second embodiment. The operation performed by the air conditioner 1B of this embodiment in the second mode (cooling operation) and the operation performed in the fourth mode (second defrosting operation) are generally the same, so the operation in the second mode by the air conditioner 1B of this embodiment will be described with reference to Figure 4.

[0051] In the second mode, the control unit of the air conditioner 1B sets the four-way switching valve V1 of the outdoor unit 100B to the second switching state and sets the four-way switching valve V3 of the outdoor unit 100B to the second switching state. This establishes communication between the first connecting pipe P1 and the discharge pipe P0, between the second connecting pipe P2 and the suction pipe P9, and between the third connecting pipe P3 and the branch pipe P5. In this second mode, refrigerant discharged from the compressor 11 flows to the outdoor heat exchanger 12. The refrigerant condenses in the outdoor heat exchanger 12 after heat exchange with outdoor air taken in by the outdoor fan 13, and then flows through the outdoor expansion valve V2 to the dehumidification / reheating indoor unit 200. The refrigerant flowing into the dehumidification / reheat indoor unit 200 is divided at point K5 in Fig. 4, with part passing through the first expansion valve V5 and flowing into the first utilization heat exchanger 21, and the other part passing through the second expansion valve V6 and flowing into the second utilization heat exchanger 22. In the first utilization heat exchanger 21, the refrigerant exchanges heat with the indoor air taken in by the indoor fan 23, cools the indoor air, and evaporates. Meanwhile, in the second utilization heat exchanger 22, the refrigerant exchanges heat with the indoor air taken in by the indoor fan 23, and also cools the indoor air and evaporates. The refrigerant flowing out of the first utilization heat exchanger 21 and the second utilization heat exchanger 22 each flow to the outdoor unit 100B, join at point K6 in Fig. 4, and return to the compressor 11 via the accumulator 14.

[0052] According to the air conditioner 1B of this embodiment, when the control unit switches to the first mode, the first utilization heat exchanger 21 and the second utilization heat exchanger 22 both function as condensers, as in the second embodiment, and the indoor air can be heated (spaced).

[0053] Furthermore, according to the air conditioner 1B of this embodiment, when the control unit switches to the third mode, it is possible to perform dehumidifying operation in the dehumidification reheat mode, as in the first embodiment.

[0054] Furthermore, in the air conditioner 1B of this embodiment, if operation continues in the first mode, frost may form on the outdoor heat exchanger 12 of the outdoor unit 100B, reducing operating efficiency. Therefore, the air conditioner 1B performs a defrosting operation to remove frost after operating in the first mode for a certain period of time. The defrosting operation is performed in the third mode or the fourth mode. In the first defrosting operation in the third mode, the first utilization heat exchanger 21 serves as an evaporator, and the second utilization heat exchanger 22 serves as a condenser. In the second defrosting operation in the fourth mode, both the first utilization heat exchanger 21 and the second utilization heat exchanger 22 serve as evaporators. In the second defrosting operation, the operation of the indoor fan 23 is stopped, thereby suppressing a decrease in the indoor temperature. In the first defrosting operation, the defrosting speed is slower than in the second defrosting operation, but because the second utilization heat exchanger 22 reheats, cold air is not blown into the room even if the indoor fan 23 continues to operate.

[0055] <Fourth embodiment> Fig. 5 shows an air conditioner 1C according to a fourth embodiment. The structure of the air conditioner 1C of this embodiment overlaps with that of the air conditioner 1B of the third embodiment. Therefore, the same components as those of the third embodiment are denoted by the same reference numerals, and only the differences from the third embodiment will be described here.

[0056] As shown in Fig. 5, the air conditioner 1C further includes a first branch connection pipe P7 branched off from the first connection pipe P1 and a second branch connection pipe P8 branched off from the second connection pipe P2. The first branch connection pipe P7 branches off from the first connection pipe P1 at point K7 in Fig. 5. Point K7 is located between the first expansion valve V5 and the outdoor expansion valve V2. The second branch connection pipe P8 branches off from the second connection pipe P2 at point K8 in Fig. 5.

[0057] In this embodiment, as shown in Fig. 5, the air conditioner 1C further includes two indoor units 200A and 200B, each having a heat exchanger and an expansion valve. These two indoor units 200A and 200B are connected in parallel to a first branch connection pipe P7 and a second branch connection pipe P8.

[0058] As described above, the dehumidifier / reheat indoor unit 200 is installed in the bathroom or kitchen of the house, while the indoor units 200A, 200B are installed in other spaces of the house, such as the living room, bedroom, children's room, hallway, etc. In Fig. 5, the indoor unit 200A is installed in the living room, and the indoor unit 200B is installed in the bedroom. Although the indoor units 200A, 200B have inferior defrosting capacity compared to the dehumidifier / reheat indoor unit 200, it is cost-effective to install the indoor units 200A, 200B, which are less expensive than the dehumidifier / reheat indoor unit 200, in spaces where this is acceptable.

[0059] <Other Embodiments> (1) In the first to fourth embodiments, the first utilization heat exchanger 21 is provided upstream of the second utilization heat exchanger 22 in the air flow path formed by the indoor fan 23, but the arrangement of the first utilization heat exchanger 21 and the second utilization heat exchanger 22 may be reversed.

[0060] (2) In the first to fourth embodiments, the first utilization heat exchanger 21 and the second utilization heat exchanger 22 may be provided in parallel in the air flow path formed by the indoor fan.

[0061] (3) In the first embodiment, the outdoor unit 100 has the outdoor expansion valve V2, but the outdoor expansion valve V2 may be omitted.

[0062] (4) In the third embodiment, the four-way switching valve V3 is provided in the outdoor unit 100B of the air conditioner 1B, but it is also possible to provide the four-way switching valve V3 in the dehumidification and reheating indoor unit 200, or to provide it between the outdoor unit 100B and the dehumidification and reheating indoor unit 200.

[0063] (5) In the third embodiment, the four-way switching valve V3 is used, but a three-way valve may be used instead.

[0064] (6) In the third embodiment, the branch pipe P5 branches off from the suction pipe P9 at point K6 in Fig. 4, but the present invention is not limited to this. As shown in Fig. 6, instead of the branch pipe P5, a pipe P5' having one end connected to the four-way switching valve V3 and the other end connected to the accumulator 14 can be used. This structure can also be applied to the structures shown in Figs. 5 and 6.

[0065] (7) In the fourth embodiment, two indoor units, indoor unit 200A and indoor unit 200B, are connected in parallel to the first branch connection pipe P7 and the second branch connection pipe P8, but this is not limited to this. Only one indoor unit may be connected to the first branch connection pipe P7 and the second branch connection pipe P8, or three or more indoor units may be connected in parallel.

[0066] (8) In the fourth embodiment, the indoor unit A and the indoor unit B have the same structure, but this is not limiting, and the indoor unit 200A and the indoor unit 200B may have different structures.

[0067] (9) In the first to fourth embodiments, the accumulator 14 is provided in the intake pipe P9, but this is not limitative, and the accumulator 14 may be omitted.

[0068] (10) In the first to fourth embodiments, a branch pipe such as a Y-shaped adapter may be used as the branch pipe in the refrigerant circuit, or the branch pipe may be formed by drilling a hole in a pipe and welding it.

[0069] (11) As long as there is no contradiction between them, the structures of the first to fourth embodiments may be combined or some of the components therein may be omitted.

[0070] (12) Although several embodiments have been described above, it will be understood that various changes in form and details can be made without departing from the spirit and scope of the present disclosure as defined in the claims.

[0071] REFERENCE SIGNS LIST 1 Air conditioner 11 Compressor 12 Outdoor heat exchanger (heat source heat exchanger) 21 First utilization heat exchanger 22 Second utilization heat exchanger 50 Control unit (control unit) 52 Suction pressure sensor (pressure sensor) 100 Outdoor unit (heat source unit) 200 Dehumidification and reheating indoor unit (first utilization unit) 200A Indoor unit (second utilization unit) P0 Discharge pipe P1 First connecting pipe P2 Second connecting pipe P3 Third connecting pipe P9 Suction pipe V5 First expansion valve (first expansion device) V6 Second expansion valve (second expansion device)

[0072] Japanese Patent Application Laid-Open No. 2014-1917

Claims

1. An air conditioner (1) that uses R32 as a refrigerant and performs a dehumidifying operation, comprising: a heat source unit (100) having a compressor (11), a discharge pipe (P0) through which refrigerant discharged from the compressor flows, a suction pipe (P9) through which refrigerant drawn into the compressor flows, and a heat source heat exchanger (12) into which refrigerant flows from the discharge pipe during the dehumidifying operation; a first utilization unit (200) having a first utilization heat exchanger (21) that functions as an evaporator during the dehumidifying operation, a first expansion device (V5) that expands refrigerant before flowing into the first utilization heat exchanger during the dehumidifying operation, and a second utilization heat exchanger (22) that functions as a condenser during the dehumidifying operation; a first connecting pipe (P1) that connects a refrigerant outlet of the heat source heat exchanger to the first expansion device during the dehumidifying operation; and a second connecting pipe (P2) that connects a refrigerant outlet of the first utilization heat exchanger to the suction pipe during the dehumidifying operation. a third connecting pipe (P3) connecting the discharge pipe and a refrigerant inlet of the second utilization heat exchanger in the dehumidifying operation, wherein in the dehumidifying operation, the refrigerant that flows from the discharge pipe through the third connecting pipe into the second utilization heat exchanger condenses in the second utilization heat exchanger, joins with the refrigerant that has been condensed in the heat source heat exchanger and flowed to the first utilization unit through the first connecting pipe, and evaporates in the first utilization heat exchanger.

2. The air conditioner according to claim 1, further comprising a second usage unit (200A) separate from the first usage unit, the first usage unit being installed in a bathroom or kitchen, which is a space in a house where hot water is used.

3. The air conditioner according to claim 1 or 2, wherein the first utilization unit further comprises a second expansion device (V6) corresponding to the second utilization heat exchanger.

4. An air conditioner as described in any one of claims 1 to 3, further comprising a control unit (50) that controls the compressor and the first expansion device during the dehumidification operation, wherein the heat source unit further has a pressure sensor (52) that detects the pressure of the refrigerant, and wherein the control unit controls the compressor and the first expansion device based on the detection value of the pressure sensor during the dehumidification operation so that the evaporation temperature of the refrigerant in the first utilization heat exchanger is lower than the dew point of the air to be dehumidified.

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