Air conditioner and control method

Abstract

The air conditioner includes one outdoor unit, multiple indoor units, and a control unit. The outdoor unit includes a compressor, a refrigerant storage tank, a flow switching valve, an outdoor heat exchanger, an outdoor blower fan, expansion valves corresponding to each of the multiple indoor units, a discharge temperature sensor installed in the discharge pipe from the compressor to the outdoor heat exchanger, and a condensation temperature sensor installed in the outdoor heat exchanger. The multiple indoor units include indoor heat exchangers, indoor blower fans, indoor temperature sensors, and indoor humidity sensors. The control unit switches between a first dehumidification operation mode that dehumidifies the room based on the indoor temperature and humidity, and a second dehumidification operation mode that controls the first dehumidification operation mode by narrowing the opening of the expansion valve. When some indoor units are controlled in the second dehumidification operation mode and other indoor units are stopped, the control unit switches the expansion valve corresponding to the stopped indoor unit from fully closed to slightly open when the value of the discharge temperature sensor or condensation temperature sensor exceeds a predetermined threshold.

Description

[Technical Field]

[0001] The present disclosure relates to an air conditioner and a control method. [Background technology]

[0002] In a single-type air conditioner (air conditioning device) in which one indoor unit is connected to one outdoor unit, in order to perform partial dehumidification operation (partial cooling dehumidification operating mode) that continues dehumidification operation while suppressing a drop in room temperature, the expansion valve opening of the corresponding indoor unit is narrowed to increase the gas area of ​​the refrigerant flowing to the indoor heat exchanger (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2023-123727 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in a multi-type air conditioner in which multiple indoor units are connected to one outdoor unit, if only one indoor unit is performing partial dehumidification while the other indoor units are stopped during dehumidification operation, there is a risk that excessive refrigerant will accumulate in the heat exchanger of the outdoor unit because the total amount of refrigerant is greater than in a single-type air conditioner, causing the refrigerant pressure and temperature to rise excessively, resulting in unstable operation.

[0005] The present disclosure has been made in consideration of the above-mentioned circumstances, and one of its objectives is to provide an air conditioner and a control method that can stably perform dehumidification operation in a multi-type air conditioner in which multiple indoor units are connected to one outdoor unit. [Means for solving the problem]

[0006] The air conditioner according to the present disclosure is an air conditioner comprising one outdoor unit and a plurality of indoor units, wherein the outdoor unit comprises a compressor, a refrigerant storage tank, a flow path switching valve, an outdoor heat exchanger, an outdoor blower fan, an expansion valve corresponding to each of the plurality of indoor units, a discharge temperature sensor installed in a discharge pipe connecting from the compressor to the outdoor heat exchanger, and a condensation temperature sensor installed in the outdoor heat exchanger; The expansion valve is installed in a pipe from the outdoor heat exchanger to the indoor unit, Each of the indoor units has an indoor heat exchanger, an indoor blower fan, an indoor temperature sensor, and an indoor humidity sensor, and is equipped with a control unit that switches between a first dehumidification operation mode in which the indoor space is dehumidified in accordance with the temperature and humidity of each of the rooms in which the indoor units are installed, and a second dehumidification operation mode in which the opening of the expansion valve is reduced to control the opening of the expansion valve in the first dehumidification operation mode, thereby reducing sensible heat capacity and dehumidifying the indoor space; The refrigerant circulates in the first dehumidification operation mode and the second dehumidification operation mode through the compressor, the outdoor heat exchanger, the expansion valve, and the indoor heat exchanger; When the control unit controls some of the multiple indoor units to the second dehumidification operation mode and other indoor units are stopped, when the value of the discharge temperature sensor or the condensation temperature sensor becomes equal to or greater than a predetermined threshold, the control unit changes the expansion valve corresponding to one of the multiple indoor units that is stopped from a fully closed state to a slightly open state.

[0009] Furthermore, a control method for an air conditioner according to the present disclosure is a control method for an air conditioner having one outdoor unit and multiple indoor units, wherein the outdoor unit has a compressor, a refrigerant storage tank, a flow path switching valve, an outdoor heat exchanger, an outdoor blower fan, expansion valves corresponding to each of the multiple indoor units, a discharge temperature sensor installed in a discharge pipe connecting from the compressor to the outdoor heat exchanger, and a condensation temperature sensor installed in the outdoor heat exchanger; The expansion valve is installed in a pipe from the outdoor heat exchanger to the indoor unit,Each of the indoor units has an indoor heat exchanger, an indoor blower fan, an indoor temperature sensor, and an indoor humidity sensor, and the control unit of the air conditioner switches between a first dehumidification operation mode in which the indoors are dehumidified in accordance with the temperature and humidity of each of the rooms in which the indoor units are installed, and a second dehumidification operation mode in which the sensible heat capacity is reduced by controlling the opening of the expansion valve in the first dehumidification operation mode, and dehumidifying the indoors; and when some of the indoor units among the indoor units are controlled to the second dehumidification operation mode and other indoor units are stopped, changing the expansion valve corresponding to a stopped indoor unit among the indoor units from a fully closed state to a slightly opened state when the value of the discharge temperature sensor or the condensation temperature sensor becomes equal to or greater than a predetermined threshold. The refrigerant circulation direction in the first dehumidification operation mode and the second dehumidification operation mode is the compressor, the outdoor heat exchanger, the expansion valve, and the indoor heat exchanger. . [Effects of the Invention]

[0011] According to the present disclosure, it is possible to stably perform dehumidifying operation in a multi-type air conditioner in which a plurality of indoor units are connected to one outdoor unit. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a diagram showing an example of a refrigerant circuit of an air conditioner according to a first embodiment. [Figure 2] FIG. 4 is a diagram illustrating the difference between a weak cooling dehumidifying operation and a partial dehumidifying operation according to the first embodiment. [Figure 3] FIG. 4 is a diagram showing an example of switching between a weak cooling dehumidifying operation and a partial dehumidifying operation according to the first embodiment. [Figure 4] FIG. 3 is a schematic diagram showing an example of control during partial dehumidification operation according to the first embodiment. [Figure 5] FIG. 3 is a schematic diagram showing an example of a pH diagram during partial dehumidification operation according to the first embodiment. [Figure 6] 5 is a flowchart showing an example of a control process for the expansion valve opening degree in a partial dehumidification operation mode according to the first embodiment. [Figure 7] FIG. 10 is a diagram showing an example of a refrigerant circuit of an air conditioner according to a second embodiment. [Figure 8]10 is a flowchart showing an example of a control process for the expansion valve opening degree in a partial dehumidification operation mode according to the second embodiment. [Figure 9] FIG. 10 is a diagram showing an example of a refrigerant circuit of an air conditioner according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, embodiments will be described with reference to the drawings. First Embodiment First, the first embodiment will be described.

[0014] 1 is a diagram showing an example of a refrigerant circuit of an air conditioner according to this embodiment. The illustrated air conditioner 100 includes an outdoor unit 90, multiple indoor units 91 (91a, 91b), and a control device 50. The outdoor unit 90 and each of the multiple indoor units 91 (91a, 91b) are connected via piping that circulates the refrigerant, and are configured as a refrigerant circuit.

[0015] The control device 50 is connected to the outdoor unit 90 and each of the multiple indoor units 91 (91a, 91b) via a control signal line. The control device 50 is configured to include a CPU (Central Processing Unit), memory (storage section), etc., and transmits control signals for controlling the outdoor unit 90 and the multiple indoor units 91 (91a, 91b). The control device 50 may be provided separately from the outdoor unit 90 and the multiple indoor units 91, may be provided inside the outdoor unit 90, or may be provided in any of the multiple indoor units 91.

[0016] The outdoor unit 90 includes a compressor 1, a flow path switching valve 2, an outdoor heat exchanger 3, an expansion valve 4 (4a, 4b), an accumulator 6 (refrigerant storage tank), an outdoor blower fan 7, a discharge temperature sensor 24, and a condensation temperature sensor 25.

[0017] Compressor 1 compresses and outputs refrigerant gas. The output of compressor 1 is adjusted by changing the frequency (operating frequency) of compressor 1 using a control signal from control device 50. Compressor 1 can be of various types, such as a rotary type (scroll type, rotary type, screw type, etc.) or a reciprocating type.

[0018] The flow path switching valve 2 switches the refrigerant circulation direction between the cooling operation, dehumidifying operation, and heating operation in response to a control signal from the control device 50.

[0019] The accumulator 6 is provided in the piping on the suction side of the compressor 1. The accumulator 6 separates the drawn refrigerant into liquid refrigerant and gas refrigerant, and draws only the gas refrigerant into the compressor 1. The accumulator 6 prevents the compressor 1 from drawing in liquid refrigerant, thereby avoiding breakdown of the compressor 1 due to liquid compression. The accumulator 6 also functions as a liquid reservoir for storing excess refrigerant that occurs due to fluctuations in the number of operating indoor units 91 in the multi-type air conditioner 100.

[0020] The discharge temperature sensor 24 is installed in the discharge pipe 11 that connects the compressor 1 to the outdoor heat exchanger 3. The condensation temperature sensor 25 is installed inside the outdoor heat exchanger 3 (for example, in the middle part).

[0021] The expansion valves 4 (4a, 4b) are provided corresponding to each of the multiple indoor units 91 (91a, 91b), and are capable of adjusting the flow rate of the refrigerant flowing through the piping. For example, the expansion valves 4 are linear expansion valves (LEV) that can open and close the valve using the force of an electromagnet. The expansion valves 4 change the valve opening (LEV opening) according to a control signal from the control device 50. Here, a state in which the valve is completely closed is referred to as "fully closed," and a state in which the valve is completely open is referred to as "fully open."

[0022] In the example shown, the expansion valve 4a is provided corresponding to the indoor unit 91a, and is installed in the piping from the outdoor heat exchanger 3 to the indoor unit 91a. That is, the expansion valve 4a is capable of adjusting the flow rate of refrigerant to the indoor unit 91a. The expansion valve 4b is provided corresponding to the indoor unit 91b, and is installed in the piping from the outdoor heat exchanger 3 to the indoor unit 91b. That is, the expansion valve 4b is capable of adjusting the flow rate of refrigerant to the indoor unit 91b.

[0023] Indoor unit 91a and indoor unit 91b are shown as examples of multiple indoor units 91 connected to the outdoor unit 90 by a refrigerant circuit. In this figure, two indoor units 91, indoor unit 91a and indoor unit 91b, are shown, but three or more indoor units may be used.

[0024] The indoor unit 91a includes an indoor heat exchanger 5a, an indoor blower fan 8a, an indoor temperature sensor 20a, an indoor humidity sensor 21a, a refrigerant liquid temperature sensor 22a, and a refrigerant gas temperature sensor 23a. Similarly, the indoor unit 91b includes an indoor heat exchanger 5b, an indoor blower fan 8b, an indoor temperature sensor 20b, an indoor humidity sensor 21b, a refrigerant liquid temperature sensor 22b, and a refrigerant gas temperature sensor 23b.

[0025] In this embodiment, control when the air conditioner 100 performs dehumidifying operation will be described. The refrigerant circulates in the same direction during dehumidifying operation as during cooling operation. During dehumidifying operation, the refrigerant circulates in the order of compressor 1, outdoor heat exchanger 3, expansion valve 4 (4a, 4b), indoor heat exchanger 5 (5a, 5b), flow path switching valve 2, and refrigerant storage tank 6, before returning to the compressor 1.

[0026] Here, the air conditioner 100 has two types of operation modes for dehumidification operation. The first dehumidification operation mode is a dehumidification operation mode in which a normal dehumidification operation is performed to dehumidify the room according to the room temperature and humidity, and a cooling operation is performed by reducing the airflow rate of the indoor blower fans 8 (8a, 8b) (hereinafter referred to as "weak cooling dehumidification operation mode").

[0027] The second dehumidification operation mode is a dehumidification operation mode that dehumidifies the room by reducing the sensible heat capacity so that the room temperature does not drop more than necessary.The refrigerant flow is the same as in the weak cooling dehumidification operation mode, but the opening of the expansion valve 4 (4a, 4b) is controlled by narrowing it (hereinafter referred to as the ``partial dehumidification operation mode'').

[0028] FIG. 2 is a diagram illustrating the difference between weak cooling and dehumidifying operation and partial dehumidifying operation. This FIG. 2 shows the relationship between the temperature and the flow position of the refrigerant in the indoor heat exchanger 5 (5a, 5b). In weak cooling and dehumidifying operation mode, the airflow rate of the indoor blower fans 8 (8a, 8b) is reduced to perform cooling operation. The refrigerant flowing through the indoor heat exchanger 5 (5a, 5b) is in two phases, liquid and gas, throughout the entire area from the inlet to the outlet, and its temperature remains approximately constant.

[0029] On the other hand, in partial dehumidification mode, the refrigerant flow is the same as in cooling mode (similar to weak cooling and dehumidification mode), but the amount of refrigerant flowing through the indoor heat exchanger 5 (5a, 5b) is less than in weak cooling and dehumidification mode because the expansion valve 4 (4a, 4b) is narrowed. The refrigerant flowing through the indoor heat exchanger 5 (5a, 5b) is in two phases (liquid and gas) at the inlet, but it completely gasifies halfway through and becomes single-phase gas at the outlet, causing the temperature to rise. As the temperature rises, it approaches room temperature, so partial dehumidification mode allows for dehumidification with reduced sensible heat capacity. Note that in partial dehumidification mode, the two-phase refrigerant region at the inlet of the indoor heat exchanger 5 (5a, 5b) is kept below the dew point temperature to ensure reliable dehumidification in this region.

[0030] FIG. 3 is a diagram showing an example of switching between weak cooling and dehumidifying operation and partial dehumidifying operation. The air conditioner 100 is controlled to weak cooling and dehumidifying operation mode when there is a large difference between the room temperature and the set temperature (i.e., when the sensible heat load is high). On the other hand, when the difference between the room temperature and the set temperature is small and further lowering the room temperature is not desirable (i.e., when the sensible heat load is low), partial dehumidifying operation mode, which performs dehumidifying operation with reduced sensible heat capacity, is appropriate. However, if partial dehumidifying operation is performed when the indoor humidity is high, the high-temperature, humid air that has passed through the dry part of the indoor heat exchanger 5 (5a, 5b) and the low-temperature, dry air that has passed through the two-phase low-temperature part may mix, causing condensed water droplets to fly outside the indoor unit (dew splash). Therefore, it is desirable to perform partial dehumidifying operation only when the indoor humidity is low.

[0031] Therefore, the air conditioner 100 controls to the weak cooling dehumidifying operation mode when the sensible heat load is equal to or greater than a preset threshold (sensible heat load threshold), and switches to the partial dehumidifying operation mode when the sensible heat load is less than the preset threshold (sensible heat load threshold) and the latent heat load is less than a preset threshold (latent heat load threshold). Note that even if the sensible heat load is less than the preset threshold (sensible heat load threshold), the air conditioner 100 controls to the weak cooling dehumidifying operation mode if the latent heat load is equal to or greater than the preset threshold (latent heat load threshold) because there is a concern that dew splashing may occur.

[0032] Here, in a multi-type air conditioner 100, for example, if one indoor unit 91 is operating in partial dehumidification mode while the other indoor units 91 are stopped, there is a concern that an excessive amount of refrigerant will accumulate in the outdoor heat exchanger 3 of the outdoor unit 90 because the total amount of refrigerant is greater than in a single-type air conditioner, causing the refrigerant pressure and temperature to rise excessively, resulting in unstable operation. This applies when there are two indoor units 91 and one is in partial dehumidification mode while the other is stopped, but when there are three or more indoor units 91, the same concern applies when at least one is stopped and the others are in partial dehumidification mode.

[0033] Therefore, in the air conditioner 100 according to this embodiment, the expansion valve 4 corresponding to the stopped indoor unit 91 is controlled from fully closed to slightly open, so that a small amount of refrigerant flows into the stopped indoor unit 91, allowing the refrigerant to escape and preventing excessive accumulation of refrigerant in the outdoor heat exchanger 3.

[0034] Here, the opening degree when controlling the expansion valve 4 corresponding to the stopped indoor unit 91 to be slightly open is preferably set to an opening degree of 6% to 30% of fully open, and more preferably set to an opening degree of 6% to 20%. In other words, the range of opening degree when controlling the expansion valve 4 to be "slightly open" is 6% to 30% of fully open, and more preferably 6% to 20%.

[0035] Hereinafter, control during partial dehumidification operation in the air conditioner 100 will be described with reference to FIGS.

[0036] Fig. 4 is a schematic diagram showing an example of control during partial dehumidification operation according to this embodiment. This diagram is based on the refrigerant circuit shown in Fig. 1, with expansion valve control added. In the example shown, indoor unit 91a is stopped, and indoor unit 91b is performing partial dehumidification operation in the partial dehumidification operation mode.

[0037] The expansion valve 4b provided in the piping to the indoor unit 91b performing partial dehumidification operation is in an open state (pulse 1). On the other hand, the expansion valve 4a provided in the piping to the stopped indoor unit 91a is in a fully closed state under conventional control, but in this embodiment, by setting it to a slightly open state (pulse 2), refrigerant also flows into the stopped indoor unit 91a.

[0038] Here, the relationship between the opening degrees of expansion valve 4b and expansion valve 4a is open (pulse 1) > slightly open (pulse 2). If the relationship between the opening degrees of expansion valve 4b and expansion valve 4a were reversed, too much refrigerant would flow to the stopped indoor unit 91a. Therefore, by maintaining the relationship between the opening degrees of expansion valve 4b and expansion valve 4a, it is possible to prevent too much refrigerant from flowing to the stopped indoor unit 91a, and to prevent the room from feeling cold even when the unit is stopped.

[0039] In addition, the opening degree when the expansion valve 4a installed in the piping to the stopped indoor unit 91a is slightly opened may be fixed to an opening degree that does not exceed the opening degree of the expansion valve 4b, or may change in accordance with changes in the opening degree of the expansion valve 4b within a range that does not exceed the opening degree of the expansion valve 4b.

[0040] FIG. 5 is a schematic diagram showing an example of a ph diagram during partial dehumidification operation shown in FIG. 4. As explained with reference to FIG. 4, this diagram shows an example of a ph diagram when the indoor unit 91b is performing partial dehumidification operation and the indoor unit 91a is stopped. The vertical axis represents pressure P, and the horizontal axis represents specific enthalpy h. Furthermore, A, B, C, D, E, and F on the ph diagram shown in FIG. 5 represent values ​​at locations indicated by the respective symbols on the refrigerant circuit shown in FIG. 4. The dashed line indicates the case where the expansion valve 4a is fully closed (conventional control), and the solid line indicates the case where the expansion valve 4a is slightly open (this embodiment).

[0041] In conventional control, the expansion valve 4a is fully closed, so refrigerant flows only to the indoor unit 91b connected to the expansion valve 4b. Because the indoor unit 91b is performing partial dehumidification operation, only gas refrigerant flows from the indoor unit 91b to the outdoor unit 90. The outdoor unit 90 is provided with an accumulator 6, but because the refrigerant flowing from the indoor unit 91b to the outdoor unit 90 is gas refrigerant, it is not stored as liquid refrigerant in the accumulator 6 and the gas refrigerant is supplied to the compressor 1. As partial dehumidification operation continues, the gas refrigerant flowing from the indoor unit 91a to the outdoor unit 90 becomes liquid refrigerant in the compressor 1 and continues to flow to the outdoor heat exchanger 3. Because the multi-type air conditioner 100 has a larger total amount of refrigerant than the single-type, if refrigerant flows only from the outdoor heat exchanger 3 to the indoor unit 91b, excessive refrigerant will accumulate in the outdoor heat exchanger 3, deteriorating heat exchange performance and increasing the condensation temperature and pressure. At this time, the right vertex A' of the pH diagram shown in FIG. 5 is the discharge temperature of the compressor 1 under conventional control, and there is a concern that this will rise too much, resulting in unstable operation.

[0042] In contrast, in the air conditioner 100 according to this embodiment, the expansion valve 4a corresponding to the stopped indoor unit 91a is controlled from fully closed to slightly open, so that liquid refrigerant is also supplied to the stopped indoor unit 91a from the outdoor heat exchanger 3. As a result, the air conditioner 100 is able to prevent excessive accumulation of refrigerant in the outdoor heat exchanger 3 and prevent deterioration of the heat exchange performance of the outdoor heat exchanger 3, resulting in lower condensing temperature and pressure compared to conventional control (right vertex A of the ph diagram shown in FIG. 5).

[0043] For example, in the air conditioner 100, when the control device 50 controls some of the multiple indoor units 91 (e.g., indoor unit 91b) to a partial dehumidification operation mode and other indoor units (e.g., indoor unit 91a) are stopped, when the value of the discharge temperature sensor 24 or the condensation temperature sensor 25 reaches or exceeds a predetermined threshold, the control device 50 changes the expansion valve (e.g., expansion valve 4a) corresponding to the stopped indoor unit (e.g., indoor unit 91a) from a fully closed state to a slightly open state.

[0044] Next, referring to FIG. 6, the operation of the process in which the control device 50 controls the opening degree of the expansion valve corresponding to the stopped indoor unit when the control device 50 controls some indoor units (e.g., indoor unit 91b) to the partial dehumidification operation mode and stops other indoor units (e.g., indoor unit 91a) will be described.

[0045] FIG. 6 is a flowchart showing an example of a control process for the expansion valve opening degree in the partial dehumidification operation mode according to this embodiment.

[0046] (Step S101) The control device 50 switches between a weak cooling and dehumidifying operation mode and a partial dehumidifying operation mode. For example, the control device 50 controls to the weak cooling and dehumidifying operation mode when the sensible heat load is equal to or greater than a predetermined threshold (sensible heat load threshold) or the latent heat load is equal to or greater than a predetermined threshold (latent heat load threshold) (see FIG. 3). On the other hand, the control device 50 switches to the partial dehumidifying operation mode when the sensible heat load is less than the predetermined threshold (sensible heat load threshold) and the latent heat load is less than the predetermined threshold (latent heat load threshold) (see FIG. 3).

[0047] (Step S103) The control device 50 determines whether or not some of the indoor units 91 are in partial dehumidification operation mode and other indoor units 91 are stopped. For example, if some of the indoor units (e.g., indoor unit 91a) are stopped and other indoor units (e.g., indoor unit 91b) are operating in partial dehumidification operation mode (step S103: YES), the process proceeds to step S105. On the other hand, if it is determined that some of the indoor units 91 are not in partial dehumidification operation mode and other indoor units 91 are not stopped (step S103: NO), the process proceeds to step S109.

[0048] (Step S105) The control device 50 acquires the values ​​detected by the discharge temperature sensor 24 and the condensation temperature sensor 25, and determines whether the value of the discharge temperature sensor 24 or the condensation temperature sensor 25 is equal to or greater than a predetermined threshold. This predetermined threshold is a threshold designed in advance based on the temperature at which the heat exchange performance of the outdoor heat exchanger 3 deteriorates.

[0049] If the control device 50 determines that the value of the discharge temperature sensor 24 or the condensation temperature sensor 25 is equal to or greater than the predetermined threshold (step S105: YES), the process proceeds to step S107. On the other hand, if the control device 50 determines that the value of the discharge temperature sensor 24 or the condensation temperature sensor 25 is less than the predetermined threshold (step S105: NO), the process proceeds to step S109.

[0050] (Step S107) The controller 50 slightly opens the expansion valve (for example, the expansion valve 4a) corresponding to the stopped indoor unit (for example, the indoor unit 91a).

[0051] (Step S109) If there is an indoor unit 91 that is stopped, the control device 50 fully closes the expansion valve (for example, expansion valve 4a) corresponding to that indoor unit (for example, indoor unit 91a).

[0052] In addition, the expansion valve (e.g., expansion valve 4b) corresponding to the indoor unit (e.g., indoor unit 91b) operating in partial dehumidification operation mode is in an open state, and its opening degree is appropriately controlled according to the indoor temperature and changes in the indoor temperature, etc.

[0053] As described above, the air conditioner 100 according to this embodiment includes one outdoor unit 90 and multiple indoor units 91 (for example, indoor unit 91a and indoor unit 91b). The outdoor unit 90 includes a compressor 1, an accumulator 6 (an example of a refrigerant storage tank), a flow path switching valve 2, an outdoor heat exchanger 3, an outdoor blower fan 7, expansion valves 4 (for example, expansion valves 4a and 4b) corresponding to each of the multiple indoor units 91, a discharge temperature sensor 24 installed in a discharge pipe 11 connecting the compressor 1 to the outdoor heat exchanger 3, and a condensation temperature sensor 25 installed in the outdoor heat exchanger 3.

[0054] Each of the multiple indoor units 91 (e.g., indoor unit 91a and indoor unit 91b) has an indoor heat exchanger 5 (e.g., indoor heat exchanger 5a, indoor heat exchanger 5b), an indoor blower fan 8 (e.g., indoor blower fan 8a, indoor blower fan 8b), an indoor temperature sensor 20 (e.g., indoor temperature sensor 20a, indoor temperature sensor 20b), and an indoor humidity sensor 21 (e.g., indoor humidity sensor 21a, indoor humidity sensor 21b).

[0055] The air conditioner 100 also includes a control device 50 (an example of a control unit). The control device 50 switches between a weak cooling and dehumidifying operation mode (an example of a first dehumidifying operation mode) in which the air conditioner dehumidifies the room in accordance with the temperature and humidity of each of the rooms in which the multiple indoor units 91 (for example, indoor unit 91a and indoor unit 91b) are installed, and a partial dehumidifying operation mode (an example of a second dehumidifying operation mode) in which the opening of the expansion valve 4 is narrowed and controlled to reduce the sensible heat capacity and dehumidify the room in the weak cooling and dehumidifying operation mode.

[0056] When the control device 50 controls some of the multiple indoor units 91 (e.g., indoor unit 91a and indoor unit 91b) to a partial dehumidification operation mode and the other indoor units are stopped, when the value of the discharge temperature sensor 24 or the condensation temperature sensor 25 reaches or exceeds a predetermined threshold, the control device 50 changes the expansion valve 4 (e.g., expansion valve 4a) corresponding to the stopped indoor unit (e.g., indoor unit 91a) among the multiple indoor units 91 (e.g., indoor unit 91a and indoor unit 91b) from a fully closed state to a slightly open state.

[0057] As a result, when the air conditioner 100 controls some of the multiple indoor units 91 (for example, indoor unit 91a and indoor unit 91b) to a partial dehumidification operation mode while the other indoor units are stopped, it is possible to provide stable operation without excessive increases in refrigerant pressure and refrigerant temperature by supplying the refrigerant stagnating in the outdoor heat exchanger 3 to the stopped indoor unit (for example, indoor unit 91a). Therefore, dehumidification operation can be stably performed in a multi-type air conditioner 100 in which multiple indoor units 91 are connected to one outdoor unit 90.

[0058] Here, when the expansion valve 4 (e.g., expansion valve 4a) corresponding to the indoor unit (e.g., indoor unit 91a) that is stopped among the multiple indoor units 91 (e.g., indoor unit 91a and indoor unit 91b) is slightly opened, the opening degree is smaller than the opening degree (e.g., expansion valve 4b) corresponding to the indoor unit (e.g., indoor unit 91b) controlled to the partial dehumidification operation mode.

[0059] This allows the air conditioner 100 to prevent excessive refrigerant flowing into a stopped indoor unit (e.g., indoor unit 91b) which would increase the cooling capacity, thereby preventing the room from feeling cold even when the unit is stopped.

[0060] Furthermore, the control method for the air conditioner 100 according to this embodiment is such that the control device 50 (an example of a control unit) provided in the air conditioner 100 controls a weak cooling dehumidification operation mode (an example of a first dehumidification operation mode) in which the air conditioner 100 dehumidifies the room in accordance with the temperature and humidity of each of the rooms in which the plurality of indoor units 91 (for example, the indoor unit 91a and the indoor unit 91b) are installed, and a partial dehumidification operation mode (an example of a second dehumidification operation mode) in which the opening of the expansion valve 4 is narrowed and controlled to reduce the sensible heat capacity and dehumidify the room. and when some of the indoor units 91 (e.g., indoor unit 91a and indoor unit 91b) are controlled to a partial dehumidification operation mode and the other indoor units are stopped, when the value of the discharge temperature sensor 24 or the condensation temperature sensor 25 becomes equal to or greater than a predetermined threshold, changing the expansion valve 4 (e.g., expansion valve 4a) corresponding to the stopped indoor unit (e.g., indoor unit 91a) of the multiple indoor units 91 (e.g., indoor unit 91a and indoor unit 91b) from a fully closed state to a slightly open state.

[0061] As a result, when some of the multiple indoor units 91 (for example, indoor unit 91a and indoor unit 91b) are controlled to a partial dehumidification operation mode and the other indoor units are stopped, the control method in the air conditioner 100 can provide stable operation without excessive increases in refrigerant pressure and refrigerant temperature by supplying the refrigerant stagnating in the outdoor heat exchanger 3 to the stopped indoor unit (for example, indoor unit 91a). Thus, the control method in the air conditioner 100 can stably perform dehumidification operation in a multi-type air conditioner 100 in which multiple indoor units 91 are connected to one outdoor unit 90.

[0062] In addition, when some of the multiple indoor units 91 (for example, indoor unit 91a and indoor unit 91b) are controlled to a partial dehumidification operation mode while the other indoor units are stopped, the control device 50 may reduce the airflow rate of the outdoor blower fan 7 to a predetermined threshold value or below.

[0063] As a result, the air conditioner 100 reduces the amount of liquid refrigerant accumulating in the outdoor heat exchanger 3 by reducing the airflow rate of the outdoor blower fan 7, and together with supplying refrigerant to a stopped indoor unit (e.g., indoor unit 91a), it is possible to prevent excessive accumulation of refrigerant in the outdoor heat exchanger 3.

[0064] In addition, in the partial dehumidification operation mode, the control device 50 controls the frequency of the compressor 1 so that the evaporation temperature (the temperature on the inlet side during partial dehumidification operation shown in Figure 2) detected by the refrigerant liquid temperature sensor 22 (22a, 22b) installed on the inlet side of the indoor heat exchanger 5 (5a, 5b) becomes equal to or lower than the target dew point temperature calculated from the target temperature and humidity.

[0065] As a result, the air conditioner 100 can continue dehumidifying by controlling the evaporation temperature of the refrigerant to a temperature equal to or lower than the dew point temperature, even if the air volume of the outdoor blower fan 7 or the opening degree of the expansion valve 4 is changed.

[0066] In addition, in the partial dehumidification operation mode, the control device 50 controls the indoor blower fans 8 (8a, 8b) so that the degree of superheat calculated from the temperatures detected by the refrigerant gas temperature sensor 23 (23a, 23b) installed on the outlet side of the indoor heat exchanger 5 (5a, 5b) and the refrigerant liquid temperature sensor 22 (22a, 22b) installed on the inlet side of the indoor heat exchanger 5 (5a, 5b) becomes equal to or greater than a preset threshold value.

[0067] This allows the air conditioner 100 to control the sensible heat capacity of the indoor unit 91 (e.g., indoor unit 91b) performing partial dehumidification operation. For example, as shown in FIG. 2, during partial dehumidification operation, the sensible heat capacity decreases as the single-phase gas region increases, relative to the region where the refrigerant is in a two-phase liquid-gas state on the inlet side and a single-phase gas state on the outlet side. The air conditioner 100 can continue dehumidification by reducing the sensible heat capacity, by controlling the indoor blower fans 8 (8a, 8b) so that the degree of superheat (the temperature rise on the outlet side relative to the inlet side of the indoor heat exchanger 5) is equal to or greater than a preset threshold (so that the single-phase gas region increases). Thus, while weak cooling dehumidification results in a high sensible heat capacity and a drop in room temperature, partial dehumidification operation reduces the sensible heat capacity, preventing the room temperature from dropping.

[0068] In addition, in the partial dehumidification operation mode, the control device 50 may control the airflow rate of the indoor blower fan 8 (8a, 8b) based on the difference in temperature (degree of superheat, temperature increase on the outlet side relative to the inlet side) detected on the outlet side and the inlet side of the indoor heat exchanger 5 (5a, 5b).

[0069] Furthermore, the control device 50 controls whether to switch from the weak cooling dehumidification operation mode to the partial dehumidification operation mode based on the indoor temperature detected by the indoor temperature sensors 20 (20a, 20b) and the indoor humidity detected by the indoor humidity sensors 21 (21a, 21b) of the indoor units 91 (for example, the indoor units 91a and 91b). For example, the control device 50 controls to the partial dehumidification operation mode when the dew point temperature calculated from the indoor temperature detected by the indoor temperature sensors 20 (20a, 20b) and the indoor humidity detected by the indoor humidity sensors 21 (21a, 21b) of the indoor units 91 (for example, the indoor units 91a and 91b) is equal to or lower than a preset threshold.

[0070] As a result, the air conditioner 100 performs partial dehumidification operation when the dew point temperature is below a preset threshold (when the indoor humidity is low), thereby preventing dew splashing, which occurs when condensed water droplets fly outside the indoor unit.

[0071] <Second embodiment> Next, a second embodiment will be described. In the first embodiment, an example was described in which the expansion valve 4a (for example) corresponding to a stopped indoor unit (for example, the indoor unit 91a) is changed from fully closed to slightly opened to allow the refrigerant to flow from the outdoor heat exchanger 3 to the stopped indoor unit (for example, the indoor unit 91a) so that an excessive amount of refrigerant does not accumulate in the outdoor heat exchanger 3. In this embodiment, instead of flowing the refrigerant from the outdoor heat exchanger 3 to the stopped indoor unit (for example, the indoor unit 91a), the refrigerant is flowed to the accumulator 6 to prevent an excessive amount of refrigerant from accumulating in the outdoor heat exchanger 3.

[0072] Figure 7 is a diagram showing an example of a refrigerant circuit of an air conditioner according to this embodiment. In this figure, components corresponding to those shown in Figure 1 are given the same reference numerals, and their explanation will be omitted. In the air conditioner 100A shown in Figure 7, the configuration of the outdoor unit 90A differs from the configuration of the outdoor unit 90 of the air conditioner 100 shown in Figure 1, with a bypass expansion valve 9 and bypass piping 10 being added to the configuration of the outdoor unit 90. The rest of the configuration of the air conditioner 100A is the same as the configuration of the air conditioner 100 shown in Figure 1.

[0073] The bypass piping 10 connects a piping 13 from the outdoor heat exchanger 3 to the expansion valves 4 (4a, 4b) with a suction piping 12 that is connected from the flow path switching valve 2 to the compressor 1 via the accumulator 6 (before the accumulator 6). The bypass expansion valve 9 is installed in the bypass piping 10. The bypass expansion valve 9 can adjust the flow rate of the refrigerant that flows from the outdoor heat exchanger 3 to the accumulator 6 via the bypass piping 10. The bypass expansion valve 9 may be an ON / OFF valve that switches between an open state and a closed state, or may be a variable valve that can change the opening degree.

[0074] For example, in the air conditioner 100A, when the control device 50 controls some of the multiple indoor units 91 (e.g., indoor unit 91b) to a partial dehumidification operation mode and stops other indoor units (e.g., indoor unit 91a), it opens the bypass expansion valve 9 while keeping the expansion valve (e.g., expansion valve 4a) of the stopped indoor unit (e.g., indoor unit 91a) fully closed.

[0075] As a result, the air conditioner 100A can prevent excessive accumulation of refrigerant in the outdoor heat exchanger 3 by flowing the refrigerant from the outdoor heat exchanger 3 to the accumulator 6, thereby preventing excessive increases in refrigerant pressure and refrigerant temperature and providing stable operation. Therefore, as with the first embodiment, the air conditioner 100A can stably perform dehumidification operation in a multi-type air conditioner 100A in which multiple indoor units 91 are connected to one outdoor unit 90A.

[0076] In the air conditioner 100A, when the control device 50 controls some of the multiple indoor units 91 (for example, indoor unit 91b) to a partial dehumidification operation mode and the other indoor units (for example, indoor unit 91a) are stopped, the control device 50 may open the bypass expansion valve 9 when the value of the discharge temperature sensor 24 or the condensation temperature sensor 25 becomes equal to or greater than a predetermined threshold value.

[0077] FIG. 8 is a flowchart showing an example of a control process for the expansion valve opening degree in the partial dehumidification operation mode according to this embodiment.

[0078] (Step S201) The control device 50 switches between a weak cooling and dehumidifying operation mode and a partial dehumidifying operation mode. For example, the control device 50 controls to the weak cooling and dehumidifying operation mode when the sensible heat load is equal to or greater than a predetermined threshold (sensible heat load threshold) or the latent heat load is equal to or greater than a predetermined threshold (latent heat load threshold) (see FIG. 3). On the other hand, the control device 50 switches to the partial dehumidifying operation mode when the sensible heat load is less than the predetermined threshold (sensible heat load threshold) and the latent heat load is less than the predetermined threshold (latent heat load threshold) (see FIG. 3).

[0079] (Step S203) The control device 50 determines whether or not some of the indoor units 91 are in partial dehumidification operation mode and other indoor units 91 are stopped. For example, if some of the indoor units (e.g., indoor unit 91a) are stopped and other indoor units (e.g., indoor unit 91b) are operating in partial dehumidification operation mode (step S203: YES), the process proceeds to step S205. On the other hand, if it is determined that some of the indoor units 91 are not in partial dehumidification operation mode and other indoor units 91 are not stopped (step S203: NO), the process proceeds to step S209.

[0080] (Step S205) The control device 50 fully closes the expansion valve (for example, the expansion valve 4a) corresponding to the stopped indoor unit (for example, the indoor unit 91a), and then proceeds to step S207.

[0081] (Step S207) The controller 50 opens the bypass expansion valve 9 while keeping the expansion valve (for example, the expansion valve 4a) of the stopped indoor unit (for example, the indoor unit 91a) fully closed.

[0082] (Step S209) If there is an indoor unit 91 that is stopped, the control device 50 fully closes the expansion valve (for example, expansion valve 4a) corresponding to that indoor unit (for example, indoor unit 91a).

[0083] Thus, the control method for the air conditioner 100A according to this embodiment includes the steps of: the control device 50 (an example of a control unit) provided in the air conditioner 100 switching between a weak cooling and dehumidifying operation mode (an example of a first dehumidifying operation mode) in which the air conditioner 100 dehumidifies the room according to the temperature and humidity of each of the rooms in which the multiple indoor units 91 (e.g., indoor unit 91a and indoor unit 91b) are installed; and a partial dehumidifying operation mode (an example of a second dehumidifying operation mode) in which the air conditioner 100 dehumidifies the room by reducing the opening of the expansion valve 4 in the weak cooling and dehumidifying operation mode, thereby reducing the sensible heat capacity; and, when some of the multiple indoor units 91 (e.g., indoor unit 91a and indoor unit 91b) are controlled to the partial dehumidifying operation mode and the other indoor units are stopped, opening the bypass expansion valve 9 while keeping the expansion valve (e.g., expansion valve 4a) of the stopped indoor unit (e.g., indoor unit 91a) fully closed.

[0084] As a result, the control method for the air conditioner 100A prevents excessive accumulation of refrigerant in the outdoor heat exchanger 3 by flowing the refrigerant from the outdoor heat exchanger 3 to the accumulator 6, and stable operation can be provided without excessive increases in refrigerant pressure and refrigerant temperature. Therefore, as with the first embodiment, the control method for the air conditioner 100A can stably perform dehumidification operation in a multi-type air conditioner 100A in which multiple indoor units 91 are connected to one outdoor unit 90A.

[0085] <Third embodiment> Next, a third embodiment will be described. In this embodiment, instead of flowing the refrigerant to a stopped indoor unit (for example, indoor unit 91a) or the accumulator 6, a receiver for storing excess liquid refrigerant is installed in the pipe 13 from the outdoor heat exchanger 3 to the expansion valve 4 (4a, 4b), thereby preventing excessive accumulation of refrigerant in the outdoor heat exchanger 3.

[0086] Figure 9 is a diagram showing an example of a refrigerant circuit of an air conditioner according to this embodiment. In this figure, components corresponding to those shown in Figure 1 are given the same reference numerals, and their explanation will be omitted. In the air conditioner 100B shown in Figure 9, the configuration of the outdoor unit 90B differs from the configuration of the outdoor unit 90 of the air conditioner 100 shown in Figure 1, with a receiver 15 being added to the configuration of the outdoor unit 90. The rest of the configuration of the air conditioner 100B is the same as the configuration of the air conditioner 100 shown in Figure 1.

[0087] Generally, when an accumulator is installed in an outdoor unit to mitigate the effects of differences in the number of connected indoor units and differences in the amount of refrigerant between cooling and heating operation, a receiver with a similar purpose is not installed at the same time. However, when some of the indoor units perform partial dehumidification operation, gas refrigerant flows into the outdoor unit and cannot be stored in the accumulator 6.

[0088] Therefore, in the air conditioner 100B of this embodiment, in addition to the accumulator 6, a receiver 15 for storing liquid refrigerant is installed in the outdoor unit 90B in the piping 13 from the outdoor heat exchanger 3 to the expansion valve 4 (4a, 4b).

[0089] As a result, the air conditioner 100B can store excess liquid refrigerant in the receiver after the gas refrigerant compressed by the compressor 1 is converted to liquid refrigerant through heat exchange in the outdoor heat exchanger 3, thereby providing stable operation without excessive increases in refrigerant pressure and refrigerant temperature. Thus, similar to the first embodiment, the air conditioner 100B can stably perform dehumidification operation in a multi-type air conditioner 100B in which multiple indoor units 91 are connected to one outdoor unit 90B.

[0090] Each embodiment has been described above in detail with reference to the drawings, but the specific configuration is not limited to these embodiments, and it is possible to combine the embodiments, or to modify or omit the embodiments as appropriate.

[0091] It should be noted that a program for realizing the functions of the control device 50 may be recorded on a computer-readable recording medium, and the program recorded on this recording medium may be read into a computer system and executed to perform the processing of the control device 50. Note that the term "computer system" here includes hardware such as an OS and peripheral devices.

[0092] Furthermore, the term "computer-readable recording medium" refers to portable media such as flexible disks, optical magnetic disks, ROMs, and CD-ROMs, as well as storage devices such as hard disks built into computer systems. Furthermore, the term "computer-readable recording medium" also includes devices that dynamically store programs for a short period of time, such as communication lines used when transmitting programs over networks like the Internet or communication lines like telephone lines, and devices that store programs for a fixed period of time, such as volatile memory within the computer systems that serve as servers or clients. The program may be a program that implements part of the aforementioned functions, or may be a program that can implement the aforementioned functions in combination with a program already stored in the computer system. The program may also be stored on a designated server and distributed (e.g., downloaded) over communication lines in response to requests from other devices.

[0093] Furthermore, some or all of the functions of the control device 50 may be realized as an integrated circuit such as an LSI (Large Scale Integration). Each function may be individually implemented as a processor, or some or all of the functions may be integrated into a processor. The integrated circuit method is not limited to LSI, and may be realized using a dedicated circuit or a general-purpose processor. Furthermore, if an integrated circuit technology that can replace LSI emerges due to advances in semiconductor technology, an integrated circuit based on that technology may be used. [Explanation of symbols]

[0094] 1 Compressor 2 Flow path switching valve 3 Outdoor heat exchanger 4(4a,4b) Expansion valve 5 Indoor heat exchanger 6 Accumulator 7 Outdoor ventilation fan 8(8a,8b) Indoor ventilation fan 9. Bypass expansion valve 10 Bypass piping 11 Discharge piping 12 Intake piping 13 Piping from outdoor heat exchanger to expansion valve 15 Receiver 20(20a, 20b) Indoor temperature sensor 21(21a, 21b) Indoor humidity sensor 22(22a, 22b) Refrigerant liquid temperature sensor 23(23a, 23b) Refrigerant gas temperature sensor 24 Discharge temperature sensor 25 Condensation temperature sensor 50 Control device 90(90A,90B) Outdoor unit 91(91a,91b) Indoor unit 100(100A, 100B) Air conditioner

Claims

1. An air conditioner having one outdoor unit and multiple indoor units, The outdoor unit includes a compressor, a refrigerant storage tank, a flow path switching valve, an outdoor heat exchanger, an outdoor blower fan, expansion valves corresponding to each of the plurality of indoor units, a discharge temperature sensor installed in a discharge pipe connecting from the compressor to the outdoor heat exchanger, and a condensation temperature sensor installed in the outdoor heat exchanger, The expansion valve is installed in a pipe from the outdoor heat exchanger to the indoor unit, Each of the indoor units has an indoor heat exchanger, an indoor blower fan, an indoor temperature sensor, and an indoor humidity sensor, a control unit that switches between a first dehumidifying operation mode in which the indoor air is dehumidified in accordance with the temperature and humidity of each of the rooms in which the plurality of indoor units are installed, and a second dehumidifying operation mode in which the sensible heat capacity is reduced by controlling the opening of the expansion valve in the first dehumidifying operation mode; Equipped with The refrigerant circulates in the first dehumidification operation mode and the second dehumidification operation mode through the compressor, the outdoor heat exchanger, the expansion valve, and the indoor heat exchanger; The control unit When some of the indoor units among the plurality of indoor units are controlled to the second dehumidifying operation mode and other indoor units are stopped, when the value of the discharge temperature sensor or the condensation temperature sensor becomes equal to or greater than a predetermined threshold, the expansion valve corresponding to the stopped indoor unit among the plurality of indoor units is changed from a fully closed state to a slightly opened state. Air conditioner.

2. the opening degree when the expansion valve corresponding to the stopped indoor unit among the plurality of indoor units is slightly opened is smaller than the opening degree of the expansion valve corresponding to the indoor unit controlled to the second dehumidifying operation mode. The air conditioner according to claim 1.

3. The control unit When some of the indoor units among the plurality of indoor units are controlled to the second dehumidifying operation mode and other indoor units are stopped, the air volume of the outdoor blower fan is reduced to a predetermined threshold value or less. The air conditioner according to claim 1 or 2.

4. The control unit In the second dehumidification operation mode, the frequency of the compressor is controlled so that an evaporation temperature detected by a temperature sensor installed on an inlet side of the indoor heat exchanger becomes equal to or lower than a target dew point temperature calculated from a target temperature and humidity. The air conditioner according to claim 1 or 2.

5. The control unit In the second dehumidifying operation mode, the indoor blower fan is controlled so that a degree of superheat calculated from temperatures detected by a temperature sensor installed on an outlet side of the indoor heat exchanger and a temperature sensor installed on an inlet side of the indoor heat exchanger becomes equal to or greater than a preset threshold value. The air conditioner according to claim 1 or 2.

6. The control unit When a dew point temperature calculated from the indoor temperature detected by the indoor temperature sensor and the indoor humidity detected by the indoor humidity sensor provided in the indoor unit is equal to or lower than a preset threshold value, the indoor unit is controlled to the second dehumidification operation mode.

3. The air conditioner according to claim 1 or 2.

7. A control method for an air conditioner having one outdoor unit and multiple indoor units, The outdoor unit includes a compressor, a refrigerant storage tank, a flow path switching valve, an outdoor heat exchanger, an outdoor blower fan, expansion valves corresponding to each of the plurality of indoor units, a discharge temperature sensor installed in a discharge pipe connecting from the compressor to the outdoor heat exchanger, and a condensation temperature sensor installed in the outdoor heat exchanger, The expansion valve is installed in a pipe from the outdoor heat exchanger to the indoor unit, Each of the indoor units has an indoor heat exchanger, an indoor blower fan, an indoor temperature sensor, and an indoor humidity sensor, A control unit provided in the air conditioner, a step of switching between a first dehumidifying operation mode in which the indoor air is dehumidified in accordance with the temperature and humidity of each of the rooms in which the plurality of indoor units are installed, and a second dehumidifying operation mode in which the sensible heat capacity is reduced by controlling the opening of the expansion valve in the first dehumidifying operation mode; When some of the indoor units among the plurality of indoor units are controlled to the second dehumidifying operation mode and other indoor units are stopped, when a value of the discharge temperature sensor or the condensation temperature sensor becomes equal to or greater than a predetermined threshold, changing the expansion valve corresponding to the stopped indoor unit among the plurality of indoor units from a fully closed state to a slightly opened state; Including, The refrigerant circulation direction in the first dehumidification operation mode and the second dehumidification operation mode is the compressor, the outdoor heat exchanger, the expansion valve, and the indoor heat exchanger. Control method.

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