Air conditioner and control method for air conditioner

Abstract

To provide an air conditioner that is less likely to cause clogging of an indoor side heat exchanger due to freezing.SOLUTION: An air conditioner 1 includes: a refrigerant circuit configured by connecting a compressor 11, an outdoor side heat exchanger 13, an expansion valve 14 and an indoor side heat exchanger 21; temperature detection means 25 detecting a temperature of the indoor side heat exchanger 21; and control means 100 controlling the refrigerant circuit. When at least one condition of a first condition where a first time has passed in a range in which the temperature detected by the temperature detection means 25 is a first temperature or lower and a second condition where a second time shorter than the first time has passed in a range in which the temperature is equal to or lower than a second temperature that is lower than the first temperature, the control means 100 determines that the indoor side heat exchanger 21 is frozen and controls the refrigerant circuit on the basis of the determination result.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This disclosure relates to an air conditioner and a method for controlling an air conditioner. [Background technology]

[0002] Conventionally, there are air conditioners that perform dehumidification by designating a portion of the indoor heat exchanger as an evaporation zone and the other portion as a superheating zone. In such air conditioners, the temperature of the evaporation zone is detected by a temperature detection means, and freezing of the indoor heat exchanger is determined based on the detection result. Specifically, if the detected temperature remains below a predetermined value for a certain period of time, it is determined that the indoor heat exchanger has frozen. If it is determined that the indoor heat exchanger has frozen, a freeze-removal operation is started to suppress clogging caused by freezing of the indoor heat exchanger. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 09-014727 [Overview of the project] [Problems that the invention aims to solve]

[0004] However, with the above determination method, even if the temperature in the evaporation zone is very low, the determination that the indoor heat exchanger has frozen will not be reached unless the condition remains below a predetermined value for a certain period of time. Therefore, if the temperature in the evaporation zone is very low, there is a risk that clogging due to freezing of the indoor heat exchanger may occur before the defreezing operation is started.

[0005] In view of the above-mentioned problems, this disclosure aims to provide an air conditioner and a control method for the air conditioner in which the indoor heat exchanger is less prone to clogging due to freezing. [Means for solving the problem]

[0006] An air conditioner according to an aspect of the present disclosure includes a refrigerant circuit configured by connecting a compressor, an outdoor heat exchanger, an expansion valve, and an indoor heat exchanger, temperature detection means for detecting the temperature of the indoor heat exchanger, and control means for controlling the refrigerant circuit. The control means determines that the indoor heat exchanger is frozen when at least one of the following conditions is satisfied: a first condition where a first time has elapsed in a range where the temperature detected by the temperature detection means is equal to or lower than a first temperature, or a second condition where a second time shorter than the first time has elapsed in a range where the temperature is equal to or lower than a second temperature which is lower than the first temperature, and controls the refrigerant circuit based on the determination result.

[0007] A control method for an air conditioner according to an aspect of the present disclosure is a control method for an air conditioner including a refrigerant circuit configured by connecting a compressor, an outdoor heat exchanger, an expansion valve, and an indoor heat exchanger, temperature detection means for detecting the temperature of the indoor heat exchanger, and control means for controlling the refrigerant circuit. The control means determines that the indoor heat exchanger is frozen when at least one of the following conditions is satisfied: a first condition where a first time has elapsed in a range where the temperature detected by the temperature detection means is equal to or lower than a first temperature, or a second condition where a second time shorter than the first time has elapsed in a range where the temperature is equal to or lower than a second temperature which is lower than the first temperature, and controls the refrigerant circuit based on the determination result.

Advantages of the Invention

[0008] The air conditioner and the control method of the air conditioner according to an aspect of the present disclosure determine that the indoor heat exchanger is frozen when at least one of the first condition or the second condition is satisfied. Therefore, the indoor heat exchanger is less likely to be clogged due to freezing.

Brief Description of the Drawings

[0009] [Figure 1] Schematic configuration diagram showing the air conditioner according to the present embodiment [Figure 2] Cross-sectional view showing the indoor unit [Figure 3] Block diagram showing the air control means and the devices connected thereto [Figure 4] Schematic side view showing the evaporation and superheating regions of the indoor heat exchanger. [Figure 5] Flowchart showing the control process for dehumidification operation [Figure 6] Flowchart showing the process for determining expansion valve control conditions [Figure 7] Diagram showing target inlet temperature table [Figure 8] Diagram showing the target outlet temperature table. [Figure 9] Flowchart showing the freezing detection process [Figure 10] Flowchart showing the control process for defreezing operation using a compressor. [Figure 11] Flowchart showing the control process for defreezing operation using an expansion valve. [Modes for carrying out the invention]

[0010] The air conditioner related to this disclosure is an air conditioning system that controls indoor temperature, humidity, air purification, etc., and is, for example, a household air conditioner.

[0011] <Air Conditioner Configuration> (Schematic configuration) Figure 1 is a schematic diagram showing an air conditioner according to this embodiment. As shown in Figure 1, the air conditioner 1 according to this embodiment comprises an outdoor unit 10 and an indoor unit 20.

[0012] The outdoor unit 10 and the indoor unit 20 are connected by piping 2. Specifically, the compressor 11, four-way valve 12, outdoor heat exchanger 13, and expansion valve 14 of the outdoor unit 10, and the indoor heat exchanger 21 of the indoor unit 20 are connected by piping 2. The compressor 11, four-way valve 12, outdoor heat exchanger 13, expansion valve 14, indoor heat exchanger 21, and piping 2 constitute the refrigeration circuit. In addition, various valves (not shown) other than the four-way valve 12 and expansion valve 14, as well as strainers (not shown), etc., are also connected to piping 2.

[0013] (Outdoor unit configuration) The outdoor unit 10 includes a compressor 11, a four-way valve 12, an outdoor heat exchanger 13, an expansion valve 14, an outdoor blower 15, an outdoor control means 101, and an accumulator (not shown), etc.

[0014] The compressor 11 compresses the refrigerant in the refrigeration circuit to a high temperature and high pressure.

[0015] The four-way valve 12 switches the flow path of the refrigerant so that the refrigerant in the refrigeration circuit is sent to the condenser. Specifically, during cooling or dehumidifying operation, the four-way valve 12 switches the flow path of the refrigerant so that the refrigerant is sent to the outdoor heat exchanger 13, which functions as a condenser. On the other hand, during heating operation, the four-way valve 12 switches the flow path of the refrigerant so that the refrigerant is sent to the indoor heat exchanger 21, which functions as a condenser.

[0016] The outdoor heat exchanger 13 performs heat exchange between the refrigerant in the refrigeration circuit and the air supplied to the outdoor heat exchanger 13.

[0017] The expansion valve 14 expands the refrigerant in the refrigeration circuit by reducing the pressure, making it low temperature and low pressure. During cooling or dehumidifying operation, the low temperature and low pressure refrigerant is sent from the expansion valve 14 to the indoor heat exchanger 21, which functions as an evaporator. On the other hand, during heating operation, the low temperature and low pressure refrigerant is sent to the outdoor heat exchanger 13, which functions as an evaporator.

[0018] The outdoor ventilation unit 15 is equipped with a propeller fan (not shown), and the rotation of the propeller fan creates an airflow that passes through the outdoor heat exchanger 13. This improves the efficiency of heat exchange in the outdoor heat exchanger 13.

[0019] The outdoor control means 101 controls the operation of the outdoor unit 10. Details will be described later.

[0020] (Configuration of the indoor unit) Figure 2 is a cross-sectional view showing the indoor unit. As shown in Figures 1 and 2, the indoor unit 20 comprises an indoor heat exchanger 21, an indoor air blower 22, an intake temperature detection means 23, a humidity detection means 24, an inlet temperature detection means 25, an outlet temperature detection means 26, a filter 27, upper and lower vanes 28, an indoor control means 102, and a housing 29 enclosing them.

[0021] As shown in Figure 2, the top surface of the housing 29 is provided with an intake port 29a for drawing air into the housing 29. The bottom surface of the housing 29 is provided with an outlet port 29b for expelling the air drawn into the housing 29 to the outside of the housing 29.

[0022] The indoor heat exchanger 21 comprises three main heat exchangers 21a to 21c and two auxiliary heat exchangers 21d and 21e.

[0023] The main heat exchangers 21a to 21c are arranged in a roughly inverted V shape between the indoor air blower 22 and the filter 27, surrounding the indoor air blower 22.

[0024] The auxiliary heat exchangers 21d and 21e are positioned between the indoor fan 22 and the filter 27, and further outward from the indoor fan 22 than the main heat exchangers 21a to 21c. Specifically, the auxiliary heat exchanger 21d is positioned between the main heat exchanger 21a and the filter 27, and the auxiliary heat exchanger 21e is positioned between the main heat exchanger 21b and the filter 27.

[0025] The main heat exchangers 21a to 21c and the auxiliary heat exchangers 21d and 21e each have a structure in which fins (not shown) are attached to piping (not shown). The main heat exchangers 21a to 21c and the auxiliary heat exchangers 21d and 21e perform heat exchange between the refrigerant flowing through their respective pipes and the air supplied to the indoor heat exchanger 21.

[0026] The indoor ventilation device 22 generates airflows 31 and 32 that are supplied to the indoor heat exchanger 21. Specifically, it draws in air from the intake port 29a, passes through the filter 27, the indoor heat exchanger 21, and the indoor ventilation device 22, and discharges it from the outlet port 29b, creating airflows 31 and 32. This improves the efficiency of heat exchange in the indoor heat exchanger 21.

[0027] In airflows 31 and 32, the auxiliary heat exchangers 21d and 21e are positioned upwind of the main heat exchangers 21a to 21c. Specifically, in airflow 31, the auxiliary heat exchanger 21d is positioned upwind of the main heat exchanger 21a, and in airflow 32, the auxiliary heat exchanger 21e is positioned upwind of the main heat exchanger 21b.

[0028] Returning to Figure 1, the intake port temperature detection means 23 is located near the intake port 29a inside the housing 29. The intake port temperature detection means 23 detects the temperature of the air that is drawn into the housing 29 from the intake port 29a and before heat exchange occurs by the indoor heat exchanger 21. Hereafter, the temperature detected by the intake port temperature detection means 23 will be referred to as the "intake port temperature".

[0029] The humidity detection means 24 is located near the intake port 29a inside the housing 29. The humidity detection means 24 detects the humidity of the air that is drawn into the housing 29 from the intake port 29a and before heat exchange occurs by the indoor heat exchanger 21.

[0030] The inlet temperature detection means 25 detects the temperature near the refrigerant inlet in the evaporation zone (described later) of the indoor heat exchanger 21. Hereinafter, the temperature detected by the inlet temperature detection means 25 will be referred to as "inlet temperature T1".

[0031] The outlet temperature detection means 26 detects the temperature near the outlet of the refrigerant in the evaporation zone of the indoor heat exchanger 21, which will be described later. Hereinafter, the temperature detected by the outlet temperature detection means 26 will be referred to as "outlet temperature T2".

[0032] The filter 27 is positioned near the intake port 29a inside the housing 29 so as to block the intake port 29a, and removes dust and dirt from the air being drawn into the housing 29 through the intake port 29a.

[0033] The upper and lower vanes 28 are rotatably mounted near the discharge port 29b of the housing 29, and adjust the direction of the air discharged from the discharge port 29b when the air conditioner 1 is in operation. When the air conditioner 1 is not in operation, the upper and lower vanes 28 block the discharge port 29b.

[0034] The indoor control means 102 controls the operation of the indoor unit 20. Details will be described later.

[0035] (Configuration of air control means) As shown in Figure 1, the control means 100 is composed of an outdoor control means 101 of the outdoor unit 10 and an indoor control means 102 of the indoor unit 20. The operation of the air conditioner 1 is controlled by the control means 100.

[0036] Figure 3 is a block diagram showing an air control means and a device connected thereto. As shown in Figure 3, the control means 100 includes an acquisition unit 103, a storage unit 104, a calculation unit 105, and a drive unit 106. The calculation unit 105 is connected to the acquisition unit 103, the storage unit 104, and the drive unit 106, respectively.

[0037] The acquisition unit 103 is connected to the intake port temperature detection means 23, humidity detection means 24, inlet temperature detection means 25, and outlet temperature detection means 26. The acquisition unit 103 acquires the intake port temperature detected by the intake port temperature detection means 23, the humidity detected by the humidity detection means 24, the inlet temperature T1 detected by the inlet temperature detection means 25, and the outlet temperature T2 detected by the outlet temperature detection means 26.

[0038] The memory unit 104 stores the setting values ​​that the calculation unit 105 uses to create the temperature table.

[0039] The calculation unit 105 receives information from the acquisition unit 103 and the storage unit 104, respectively, and performs calculations based on that information.

[0040] The drive unit 106 is connected to the compressor 11 and the expansion valve 14. Based on the calculation results from the calculation unit 105, the drive unit 106 transmits instruction signals to the compressor 11 and the expansion valve 14 to drive them.

[0041] <Air conditioner operation> (Refrigerant flow in the refrigeration circuit) This section explains the flow of refrigerant within the refrigeration circuit during cooling or dehumidifying operation.

[0042] During cooling or dehumidifying operation, the refrigerant in a gaseous state within the refrigeration circuit is compressed by the compressor 11 to become high temperature and high pressure. The high temperature and high pressure refrigerant is then sent to the outdoor heat exchanger 13 via the four-way valve 12. The refrigerant sent to the outdoor heat exchanger 13 exchanges heat with the air passing through it. This heat exchange causes the gaseous refrigerant to condense and change into a liquid state. The liquid refrigerant then passes through the expansion valve 14, becoming low temperature and low pressure, and thus becoming a two-phase gas-liquid refrigerant, which is then sent to the indoor heat exchanger 21.

[0043] The gaseous-liquid two-phase refrigerant sent to the indoor heat exchanger 21 exchanges heat with the air passing through the indoor heat exchanger 21. This heat exchange changes the gaseous-liquid two-phase refrigerant into a gaseous state. The refrigerant, now in a gaseous state, is then sent back to the compressor 11.

[0044] As described above, during cooling or dehumidifying operation, the refrigerant circulates through the refrigeration circuit in the following order: compressor 11, four-way valve 12, outdoor heat exchanger 13, expansion valve 14, and indoor heat exchanger 21. On the other hand, during heating operation, the refrigerant circulates through the refrigeration circuit in the opposite direction to that during cooling or dehumidifying operation.

[0045] (Evaporation and superheating regions of the indoor heat exchanger) The air conditioner 1 can selectively perform dehumidification operation in which a portion of the indoor heat exchanger 21 is in the evaporation zone, and dehumidification operation in which the entire indoor heat exchanger 21 is in the evaporation zone. The user can select which type of dehumidification operation to perform by operating a remote controller (not shown), etc. The indoor heat exchanger 21 in the evaporation zone will be described in detail below. Note that the air conditioner 1 may be configured to only perform dehumidification operation in which a portion of the indoor heat exchanger 21 is in the evaporation zone, and not to perform dehumidification operation in which the entire indoor heat exchanger 21 is in the evaporation zone. Alternatively, the air conditioner 1 may be configured to perform dehumidification operation in which a portion of the indoor heat exchanger 21 is in the evaporation zone when certain conditions are met (for example, when the indoor and outdoor temperatures are predetermined, the indoor humidity is predetermined, and the compressor 11 has reached a predetermined operating time) during cooling operation or dehumidification operation in which the entire indoor heat exchanger 21 is in the evaporation zone.

[0046] Figure 4 is a schematic side view showing the evaporation and superheating regions of the indoor heat exchanger. During dehumidification operation, the indoor heat exchanger 21 is divided into an evaporation region and a superheating region, as shown in Figure 4, for example. In Figure 4, the areas marked with "×" in the circle are the evaporation region, and the areas marked with "〇" in the circle are the superheating region. That is, the entire main heat exchanger 21a is in the superheating region. The main heat exchangers 21b and 21c each have a portion in the evaporation region and the other portion in the superheating region. The auxiliary heat exchangers 21d and 21e each have the entire evaporation region. The main heat exchangers 21a to 21c and the auxiliary heat exchangers 21d and 21e are connected by piping 50 to 60.

[0047] Specifically, the expansion valve 14 (not shown in Figure 4) is connected to the auxiliary heat exchanger 21d by piping 50. The auxiliary heat exchanger 21d is connected to the auxiliary heat exchanger 21e by piping 51. The auxiliary heat exchanger 21e is connected to the evaporation zone of the main heat exchanger 21b by piping 52. The evaporation zone of the main heat exchanger 21b is connected to the evaporation zone of the main heat exchanger 21c by piping 53. Thus, the evaporation zone of the indoor heat exchanger 21 is composed of the auxiliary heat exchanger 21d, the auxiliary heat exchanger 21e, the evaporation zone of the main heat exchanger 21b, and the evaporation zone of the main heat exchanger 21c.

[0048] The evaporation zone of the main heat exchanger 21c is connected to the main heat exchanger 21a by pipes 54 and 55. The main heat exchanger 21a is connected to a portion of the superheating zone of the main heat exchanger 21b by pipe 56. A portion of the superheating zone of the main heat exchanger 21b is connected to the compressor 11 (not shown in Figure 4) by pipe 57. The first superheating zone of the indoor heat exchanger 21 is formed by the main heat exchanger 21a and a portion of the superheating zone of the main heat exchanger 21b.

[0049] The evaporation zone of the main heat exchanger 21c is connected to the rest of the superheating zone of the main heat exchanger 21b by pipes 54 and 58. The rest of the superheating zone of the main heat exchanger 21b is connected to the superheating zone of the main heat exchanger 21c by pipe 59. The superheating zone of the main heat exchanger 21c is connected to the compressor 11 (not shown in Figure 4) by pipe 60. The rest of the superheating zone of the main heat exchanger 21b and the superheating zone of the main heat exchanger 21c together constitute the second superheating zone of the indoor heat exchanger 21.

[0050] The refrigerant supplied from the expansion valve 14 first flows into the evaporation zone of the indoor heat exchanger 21, then branches off and passes through the first and second superheating zones, flows out from those superheating zones and is sent to the compressor 11. Specifically, the refrigerant supplied from the expansion valve 14 flows from piping 50 into the auxiliary heat exchanger 21d, passes through piping 51, auxiliary heat exchanger 21e, piping 52, the evaporation zone of the main heat exchanger 21b, piping 53, and the evaporation zone of the main heat exchanger 21c. Next, since piping 54 branches into piping 55 and piping 58, it passes through a route consisting of the main heat exchanger 21a, piping 56, and part of the superheating zone of the main heat exchanger 21b, or a route consisting of the other part of the superheating zone of the main heat exchanger 21b, piping 59, and the superheating zone of the main heat exchanger 21c, flows out from piping 57 or piping 60 and is sent to the compressor 11.

[0051] The inlet temperature detection means 25 is located near the inlet of the evaporation zone of the indoor heat exchanger 21. More specifically, the inlet temperature detection means 25 is located near the auxiliary heat exchanger 21d. As described above, the evaporation zone of the indoor heat exchanger 21 is composed of the auxiliary heat exchanger 21d, the auxiliary heat exchanger 21e, the evaporation zone of the main heat exchanger 21b, and the evaporation zone of the main heat exchanger 21c, with the auxiliary heat exchanger 21d being the upstreammost of these. Therefore, the piping 50 connected to the upstreammost auxiliary heat exchanger 21d is located near the inlet of the evaporation zone. Accordingly, the inlet temperature detection means 25 is located in the piping 50.

[0052] Since the inlet temperature detection means 25 is provided in the piping 50 through which the refrigerant flows into the evaporation zone, the temperature near the inlet of the evaporation zone of the indoor heat exchanger 21 can be accurately measured. Therefore, temperature control can be efficiently performed when suppressing clogging due to freezing of the indoor heat exchanger 21 or when performing thawing operations.

[0053] The outlet temperature detection means 26 is located at the outlet of the evaporation zone of the indoor heat exchanger 21. To reiterate, the evaporation zone of the indoor heat exchanger 21 is composed of the auxiliary heat exchanger 21d, the auxiliary heat exchanger 21e, the evaporation zone of the main heat exchanger 21b, and the evaporation zone of the main heat exchanger 21c. Of these, the downstreammost is the evaporation zone of the main heat exchanger 21c. Therefore, the piping 54 connected to the evaporation zone of the main heat exchanger 21c, which is the downstreammost, corresponds to the outlet of the evaporation zone. Accordingly, the outlet temperature detection means 26 is located in the piping 54.

[0054] Since the outlet temperature detection means 26 is provided in the piping 54 through which the refrigerant flows out of the evaporation zone, the temperature near the outlet of the evaporation zone of the indoor heat exchanger 21 can be accurately measured. Therefore, if the temperature near the outlet of the evaporation zone of the indoor heat exchanger 21 detected by the outlet temperature detection means 26 is approximately the same as the intake temperature detected by the intake temperature detection means 23, it can be detected that evaporation has finished. The locations where the inlet temperature detection means 25 and outlet temperature detection means 26 are provided are not limited to those described above. The inlet temperature detection means 25 may be provided upstream of the piping 50, that is, near the expansion valve 14. This arrangement allows for the detection of the temperature at which the refrigerant temperature drops the most. Furthermore, the inlet temperature detection means 25 may be provided in the piping within the evaporation region, for example, in piping 51, piping 52, and piping 53.

[0055] The outlet temperature detection means 26 may be provided in pipes 55 and 58 that branch off from pipe 54. This arrangement allows the outlet temperature detection means 26 to detect the temperature of the pipe through which the refrigerant flows after branching. Furthermore, the outlet temperature detection means 26 may be provided downstream of pipes 55 and 58, that is, near the main heat exchanger 21a and / or main heat exchanger 21b. This arrangement allows for more accurate detection of the temperature at which the main heat exchanger 21a and / or main heat exchanger 21b enter the superheated zone.

[0056] <Air conditioner control method> (Control processing for dehumidification operation) Figure 5 is a flowchart showing the control process for dehumidification operation. As shown in Figure 5, when dehumidification operation is started, for example by pressing the first dehumidification operation button by the user, the control means 100 performs a process to determine the expansion valve control conditions (step S101). Details of the process to determine the expansion valve control conditions will be described later.

[0057] Once the process for determining the expansion valve control conditions is complete, the control means 100 determines whether the inlet temperature T1 is equal to or above the upper limit temperature (step S102). The upper limit temperature is the temperature determined in the expansion valve control condition determination process described later.

[0058] If the inlet temperature T1 is above the upper limit temperature (Yes in step S102), the control means 100 sends an instruction signal to the drive unit 106 to reduce the opening degree of the expansion valve 14, and the drive unit 106 reduces the opening degree of the expansion valve 14 (step S107).

[0059] When the opening of the expansion valve 14 decreases, the control means 100 determines whether or not the dehumidification operation has stopped (S109). If the dehumidification operation has stopped (Yes in step S109), the control process for the dehumidification operation is terminated. If the dehumidification operation has not stopped (No in step S109), the process for determining the expansion valve control conditions is performed again (step S101).

[0060] Returning to step S102, if the inlet temperature T1 is not above the upper limit temperature (No in step S102), the control means 100 determines whether the heating temperature T3 is above the upper limit temperature (step S103). If the heating temperature T3 is above the upper limit temperature (Yes in step S103), the control means 100 sends an instruction signal to the drive unit 106 to reduce the opening degree of the expansion valve 14, and the drive unit 106 reduces the opening degree of the expansion valve 14 (step S107). The processing after the opening degree of the expansion valve 14 is reduced is as described above.

[0061] Returning to step S103, if the heating temperature T3 is not above the upper limit temperature (No in step S103), the control means 100 determines whether the inlet temperature T1 is below the lower limit temperature (step S104). The lower limit temperature is the temperature determined in the expansion valve control condition determination process described later.

[0062] If the inlet temperature T1 is below the lower limit temperature (Yes in step S104), the control means 100 sends an instruction signal to the drive unit 106 to increase the opening degree of the expansion valve 14, and the drive unit 106 increases the opening degree of the expansion valve 14 (step S108).

[0063] When the opening of the expansion valve 14 increases, the control means 100 determines whether or not the dehumidification operation has stopped (S109). If the dehumidification operation has stopped (Yes in step S109), the control process for the dehumidification operation is terminated. If the dehumidification operation has not stopped (Yes in step S109), the process for determining the expansion valve control conditions is performed again (step S101).

[0064] On the other hand, returning to step S104, if the inlet temperature T1 is not below the lower limit temperature (No in step S104), the control means 100 determines whether the heating temperature T3 is below the lower limit temperature (step S105). If the heating temperature T3 is below the lower limit temperature (Yes in step S105), the control means 100 sends an instruction signal to the drive unit 106 to increase the opening degree of the expansion valve 14, and the drive unit 106 increases the opening degree of the expansion valve 14 (step S108). The processing after the opening degree of the expansion valve 14 is increased is as described above.

[0065] Returning to step S105, if the heating temperature T3 is not below the lower limit temperature (no in step S105), the control means 100 determines that the inlet temperature T1 and heating temperature T3 are within the stable range and maintains the opening of the expansion valve 14 (step S106). Furthermore, the control means 100 determines whether the dehumidification operation has stopped (S109), and if the dehumidification operation has stopped (yes in step S109), it terminates the control process for the dehumidification operation. If the dehumidification operation has not stopped (yes in step S109), it performs the process of determining the expansion valve control conditions again (step S101).

[0066] As described above, if at least one of the inlet temperature T1 and the heating temperature T3 is above the upper limit temperature, the opening of the expansion valve 14 is reduced, and if at least one of the inlet temperature T1 and the heating temperature T3 is below the lower limit temperature, the opening of the expansion valve 14 is increased. In all other cases, the opening of the expansion valve 14 is maintained.

[0067] However, in dehumidification operation where a portion of the indoor heat exchanger 21 is in the evaporation zone, it is expected that the inlet temperature T1 will drop sharply. Furthermore, since the air conditioner 1 prioritizes the control of throttling the expansion valve 14, there is a risk of clogging due to freezing in the evaporation zone of the indoor heat exchanger 21. Therefore, in order to prevent freezing in the evaporation zone of the indoor heat exchanger 21, the air conditioner 1 sets a time for determining freezing according to the temperature at which freezing is determined. Specifically, when the inlet temperature T1 is below the first temperature (e.g., 0°C), freezing is determined when that condition continues for the first hour (e.g., 10 minutes). Also, when the outlet temperature T2 is below the second temperature (e.g., -5°C), freezing is determined when that condition continues for the second hour (e.g., 3 minutes). While the above temperature settings are preferable, the second temperature only needs to be at least lower than the first temperature, and the second hour only needs to be at least shorter than the first hour.

[0068] (Determination process for expansion valve control conditions) Figure 6 is a flowchart showing the process for determining the expansion valve control conditions. As shown in Figure 6, in the process for determining the expansion valve control conditions, the acquisition unit 103 acquires information regarding the suction port temperature detected by the suction port temperature detection means 23 (suction port temperature information) from the suction port temperature detection means 23 (step S201). The acquisition unit 103 also acquires information regarding the humidity detected by the humidity detection means 24 (humidity information) from the humidity detection means 24 (step S202). Note that the acquisition of suction port temperature information and the acquisition of humidity information can be performed in either order, or both can be performed simultaneously.

[0069] Next, the calculation unit 105 determines the dew point temperature based on the intake port temperature information and humidity information acquired by the acquisition unit 103 and the set value previously stored in the storage unit 104 (step S203).

[0070] Next, the calculation unit 105 determines a target inlet temperature table based on the dew point temperature and the information from the storage unit 104 (step S204). Here, the target inlet temperature table is a temperature table aimed at controlling the opening degree of the expansion valve 14 so that the inlet temperature T1 detected by the inlet temperature detection means 25 falls within a stable region. Details of the method for determining the target inlet temperature table will be described later.

[0071] Next, the calculation unit 105 determines a target outlet temperature table based on the dew point temperature and the information from the storage unit 104 (step S205). Here, the target outlet temperature table is a temperature table that aims to control the opening degree of the expansion valve 14 so that the temperature obtained by subtracting the outlet temperature T2 detected by the outlet temperature detection means 26 from the intake port temperature (hereinafter referred to as "heating temperature T3") falls within a stable region. Details of the method for determining the target outlet temperature table will be described later.

[0072] Furthermore, the determination of the target inlet temperature table and the target outlet temperature table can be done in either order, or both can be done simultaneously.

[0073] (Target Inlet Temperature Table) Figure 7 is a diagram showing the target inlet temperature table. As shown in Figure 7, in this embodiment, the target inlet temperature table is divided into five regions in descending order of temperature: opening degree decrease region A, opening degree decrease region B, stable region, opening degree increase region B, and opening degree increase region A. Opening degree increase region A and opening degree increase region B are regions where the opening degree of the expansion valve 14 is increased, while opening degree decrease region A and opening degree decrease region B are regions where the opening degree of the expansion valve 14 is decreased. Here, using the opening degree of the expansion valve 14 in the stable region as a reference, the magnitude of the increase in opening degree is opening degree increase region A > opening degree increase region B, and the magnitude of the decrease in opening degree is opening degree decrease region A > opening degree decrease region B.

[0074] By determining the region band in this way, even if the inlet temperature T1 is in a temperature range higher than the stable regions such as the opening reduction region A and the opening reduction region B, by reducing the opening of the expansion valve 14, the inlet temperature T1 can be reduced to the stable region, and the indoor air passing through the indoor heat exchanger 21 can be reduced to below the dew point temperature, and dehumidification can be performed. Further, even if the inlet temperature T1 is in a temperature range lower than the stable regions such as the opening increase region A and the opening increase region B, by increasing the opening of the expansion valve 14, freezing near the inlet of the indoor heat exchanger 21 can be suppressed, and stable dehumidification can be performed without being clogged by freezing.

[0075] These region bands are divided by eight temperatures of T I1 、T I2 、T I3 、T I4 、T I1 +1、T I2 +1、T I3 +1、T I4 +1. Among these, T I1 、T I2 、T I1 +1、T I2 +1 indicate the upper limit temperatures that serve as the criteria for determining to reduce the opening of the expansion valve 14 in the control process of the dehumidification operation. Further, T I3 、T I4 、T I3 +1、T I4 +1 indicate the lower limit temperatures that serve as the criteria for determining to increase the opening of the expansion valve 14 in the control process of the dehumidification operation.

[0076] Furthermore, explaining the eight temperatures from another perspective, T I1 、T I2 、T I3 、T I4 indicate the boundary temperatures when the inlet temperature T1 decreases, and T I1 +1、T I2 +1、T I3 +1、T I4+1 indicates the boundary temperature when the inlet temperature T1 rises. The boundary temperature when the inlet temperature T1 rises is set 1°C higher than the boundary temperature when the inlet temperature T1 falls. Note that it is not limited to 1°C, but may be a fixed value other than 1°C that allows for normal operation. Furthermore, it may not be a fixed value, but a variable value that changes depending on the external environment, etc.

[0077] For example, when the inlet temperature T1 is within the range of opening degree reduction region A, the boundary temperature to opening degree reduction region B is T I1 Therefore, the boundary line when the opening decreases from the decreasing region B to the stable region is T. I2 On the other hand, when the inlet temperature T1 is within the range of the stable region, the boundary temperature to the opening degree reduction region B is T I2 The value is +1, and the boundary temperature from the opening degree reduction region B to the opening degree reduction region A is T I1 It's +1.

[0078] (Target outlet temperature table) Figure 8 is a diagram showing the target outlet temperature table. As shown in Figure 8, in this embodiment, the target outlet temperature table is determined to have five regions in descending order of temperature: opening degree decreasing region C, opening degree decreasing region D, stable region, opening degree increasing region D, and opening degree increasing region C.

[0079] The opening degree increase region C and the opening degree increase region D are regions in which the opening degree of the expansion valve 14 is increased, and the opening degree decrease region C and the opening degree decrease region D are regions in which the opening degree of the expansion valve 14 is decreased. Here, with the opening degree of the expansion valve 14 in the stable region as the reference, the magnitude of the increase in the opening degree is opening degree increase region C > opening degree increase region D, and the magnitude of the decrease in the opening degree is opening degree decrease region C > opening degree decrease region D.

[0080] By setting these temperature zones, even if the heating temperature T3 is in a temperature zone higher than the stable zone, such as the opening degree reduction zone C and opening degree reduction zone D, the heating temperature T3 can be lowered to the stable zone by reducing the opening degree of the expansion valve 14, and the area of ​​the evaporation zone can be controlled to stay within a predetermined range. Furthermore, the dehumidified air passes through the superheated zone, warming it to near room temperature before being discharged into the room. In addition, even if the heating temperature T3 is in a temperature zone lower than the stable zone, such as the opening degree increase zone C and opening degree increase zone D, the heating temperature T3 can be raised to the stable zone by increasing the opening degree of the expansion valve 14, thereby suppressing the decrease in dehumidification performance due to the widening of the superheated zone area.

[0081] These regions are T O1 , T O2 , T O3 , T O4 , T O1 +1, T O2 +1, T O3 +1, T O4 It can be divided into eight temperatures starting from +1. Of these, T O1 , T O2 , T O1 +1, T O2 +1 indicates the upper temperature limit that serves as the criterion for deciding to reduce the opening degree of the expansion valve 14 in the control process of dehumidification operation. O3 , T O4 , T O3 +1, T O4 +1 indicates the lower limit temperature which serves as the criterion for deciding to increase the opening degree of the expansion valve 14 during the control process of dehumidification operation.

[0082] Furthermore, to explain the eight temperatures from a different angle, T O1 , T O2 , T O3 , T O4 This indicates the boundary temperature when the heating temperature T3 decreases. O1 +1, T O2 +1, T O3 +1, T O4+1 indicates the boundary temperature when the heating temperature T3 rises. The boundary temperature when the heating temperature T3 rises is set 1°C higher than the boundary temperature when the heating temperature T3 falls. Note that it is not limited to 1°C, but may be a fixed value other than 1°C that allows for normal operation. Furthermore, it may not be a fixed value, but a variable value that changes depending on the external environment, etc.

[0083] For example, when the heating temperature T3 is within the range of the opening degree reduction region C, the boundary temperature to the opening degree reduction region D is T O1 Therefore, the boundary temperature when the opening decreases from the decreasing region D to the stable region is T O2 On the other hand, when the heating temperature T3 is within the stable region, the boundary temperature to the opening degree reduction region D is T O2 The value is +1, and the boundary temperature from the opening degree decreasing region D to the opening degree decreasing region C is T O1 It's +1.

[0084] Incidentally, regarding the target inlet temperature table and target outlet temperature table, it is conceivable that different control commands may be issued for the outlet side and the inlet side. Therefore, in air conditioner 1, the following priority order is set: inlet side "decrease expansion valve opening" > outlet side "decrease expansion valve opening" > inlet side "increase expansion valve opening" > outlet side "increase expansion valve opening".

[0085] (Freezing detection process) Figure 9 is a flowchart of the freezing determination process. As shown in Figure 9, when the dehumidification operation starts, the control means 100 determines whether the inlet temperature T1 is less than the first temperature (step S301).

[0086] If the inlet temperature T1 is below the first temperature (Yes in step S301), it is determined whether that condition continues for a first time (step S302). If it continues (Yes in step S302), the control means 100 determines that the indoor heat exchanger 21 will freeze (step S305).

[0087] On the other hand, if the inlet temperature T1 is not less than the first temperature (No in step S301), the inlet temperature T1 and the first temperature are continuously compared.

[0088] If the condition does not persist, the next step is to determine whether the inlet temperature T1 is below the second temperature (step S303). If it is below the second temperature, the next step is to determine whether the condition persists for two hours (step S304), and if it persists, it is determined that the system is frozen (step S305). By determining the duration of each of the two temperature values ​​in this way, freezing can be determined efficiently.

[0089] (Defrosting operation) Next, the defreezing operation will be described. When the control means 100 determines that the indoor heat exchanger 21 is frozen, it performs a defreezing operation to thaw the freezing. Below, as examples of defreezing operations, a defreezing operation using the compressor 11 and a defreezing operation using the expansion valve 14 will be described.

[0090] First, I will explain the defreezing operation using a compressor.

[0091] Figure 10 is a flowchart showing the control process for defreezing operation using a compressor. As shown in Figure 10, if it is determined that the indoor heat exchanger 21 is frozen, the control means 100 reduces the operating frequency of the compressor 11 (step S401). Specifically, the calculation unit 105 of the control means 100 sends an instruction signal to the drive unit 106 to reduce the operating frequency of the compressor 11, and the drive unit 106 controls the compressor 11 based on that instruction signal. As a result, the operating frequency of the compressor 11 decreases, the temperature of the indoor heat exchanger 21 rises, and defreezing begins.

[0092] The reduction in operating frequency is, for example, 2 Hz. However, the reduction in operating frequency is not limited to 2 Hz; any value that can thaw the freezing is acceptable.

[0093] Next, the control means 100 determines whether the inlet temperature T1 is equal to or greater than the first temperature (step S402). Then, until the inlet temperature T1 becomes equal to or greater than the first temperature, the control to reduce the operating frequency of the compressor 11 is continued (No in step S402).

[0094] On the other hand, if the inlet temperature T1 rises above the first temperature ("Yes" in step S402), the control means 100 increases the operating frequency of the compressor 11 (step S403). Specifically, the calculation unit 105 of the control means 100 sends an instruction signal to the drive unit 106 to return the operating frequency of the compressor 11 to its original value, and the drive unit 106 controls the compressor 11 based on that instruction signal. As a result, the operating frequency of the compressor 11 increases, and the temperature of the indoor heat exchanger 21 decreases. In other words, the thawing operation ends and the dehumidification operation resumes.

[0095] Figure 11 is a flowchart showing the control process for defreezing operation using an expansion valve. As shown in Figure 11, if it is determined that the indoor heat exchanger 21 is frozen, the control means 100 increases the opening of the expansion valve 14 (step S501). Specifically, the calculation unit 105 of the control means 100 sends an instruction signal to the drive unit 106 to increase the opening of the expansion valve 14, and the drive unit 106 controls the expansion valve 14 based on that instruction signal. As a result, the opening of the expansion valve 14 increases, the temperature of the indoor heat exchanger 21 rises, and defreezing begins.

[0096] The increase in the opening degree of the expansion valve 14 is, for example, 10 pls. However, the increase in the opening degree of the expansion valve 14 is not limited to 10 pls; any value that can thaw the freezing is acceptable.

[0097] Next, the control means 100 determines whether the inlet temperature T1 is equal to or greater than the first temperature (step S502). Then, until the inlet temperature T1 is equal to or greater than the first temperature, the control to increase the opening degree of the expansion valve 14 is continued (No in step S502).

[0098] On the other hand, if the inlet temperature T1 becomes equal to or greater than the first temperature (Yes in step S502), the control means 100 reduces the opening degree of the expansion valve 14 (step S503). Specifically, the calculation unit 105 of the control means 100 sends an instruction signal to the drive unit 106 to return the opening degree of the expansion valve 14 to its original state, and the drive unit 106 controls the expansion valve 14 based on that instruction signal. As a result, the opening degree of the expansion valve 14 decreases, and the temperature of the indoor heat exchanger 21 drops. In other words, the thawing operation ends and the dehumidification operation resumes.

[0099] As described above, the defreezing operation may be performed simultaneously using the compressor 11 and the expansion valve 14, or only one of them may be performed. Furthermore, the defreezing operation may consist of either cooling operation, heating operation, or dehumidification operation where the entire indoor heat exchanger 21 is in the evaporation zone. It may also be combined with the defreezing operation using the compressor 11 and the expansion valve 14. [Industrial applicability]

[0100] An air conditioner and a control method for an air conditioner according to one aspect of this disclosure can be widely applied to various air conditioners, including those used in ordinary households. [Explanation of symbols]

[0101] 1. Air conditioner 11 Compressor 13 Outdoor heat exchanger 14. Expansion valve 21 Indoor heat exchanger 21a,21b,21c Main heat exchanger 21d,21e Auxiliary heat exchanger 25 Temperature detection means (inlet temperature detection means) 26. Temperature detection means (outlet temperature detection means) 100 Control means

Claims

1. The system comprises a refrigerant circuit comprising a compressor, an outdoor heat exchanger, an expansion valve, and an indoor heat exchanger, a temperature detection means for detecting the temperature of the indoor heat exchanger, and a control means for controlling the refrigerant circuit. The control means performs a dehumidification operation in which a part of the indoor heat exchanger is designated as an evaporation zone and the other part as a superheating zone, and when the control means satisfies at least one of the following conditions, a first condition in which a first time has elapsed while the temperature detected by the temperature detection means is in a range of a first temperature or less, or a second condition in which a second time shorter than the first time has elapsed while the temperature is in a range of a second temperature or less that is less than the first temperature, the control means determines that the indoor heat exchanger is frozen and performs a defreezing operation. The control means is characterized in that, after performing the defreezing operation, it cancels the defreezing operation when the temperature detected by the temperature detection means becomes equal to or greater than the first temperature.

2. The air conditioner according to claim 1, wherein the indoor heat exchanger is composed of a main heat exchanger and an auxiliary heat exchanger located upstream of the main heat exchanger, and the temperature detection means for detecting the temperature of the indoor heat exchanger is located in the refrigerant inlet piping of the auxiliary heat exchanger during the dehumidification operation.

3. The air conditioner according to any one of claims 1 or 2, characterized in that the control means performs a defreezing operation that reduces the operating frequency of the compressor.

4. The air conditioner according to any one of claims 1 to 3, characterized in that the control means performs a defreezing operation that increases the opening degree of the expansion valve.

5. The air conditioner according to any one of claims 1 to 4, characterized in that the temperature sensing means is provided in the refrigerant inlet piping of the indoor heat exchanger when the indoor heat exchanger is functioning as an evaporator.

6. A control method for an air conditioner comprising: a refrigerant circuit configured by connecting a compressor, an outdoor heat exchanger, an expansion valve, and an indoor heat exchanger; a temperature detection means for detecting the temperature of the indoor heat exchanger; and a control means for controlling the refrigerant circuit, The control means performs a dehumidification operation in which a part of the indoor heat exchanger is designated as an evaporation zone and the other part as a superheating zone. The control means determines that the indoor heat exchanger has frozen when at least one of the following conditions is met: a first condition in which a first time has elapsed while the temperature detected by the temperature detection means is within a range of a first temperature or less, or a second condition in which a second time shorter than the first time has elapsed while the temperature is within a range of a second temperature or less than the first temperature, and performs a defreezing operation. A control method for an air conditioner, characterized in that the control means cancels the defreezing operation after performing the defreezing operation if the temperature detected by the temperature detection means becomes equal to or greater than the first temperature.

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