Air conditioner

Abstract

To provide a highly reliable air conditioner.SOLUTION: An air conditioner 100 includes: an indoor unit 20 that has an indoor heat exchanger 15 constituted by heat exchange parts 15a, 15b and an indoor fan 16; a control device 50 that executes a freezing operation for freezing the heat exchange part 15b; and an outdoor unit 30 having an outdoor fan 13 that promotes heat exchange in an outdoor heat exchanger 12. When determining that a predetermined condition that might cause a freezing abnormality in the heat exchange part 15b is satisfied by using measurement values Tm1, Tm2, Tm3, the control device 50 makes rotating speeds of the indoor fan 16 and the outdoor fan 13 driven during the freezing operation slower than that when the predetermined condition is not satisfied, so as to execute the freezing operation.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to an air conditioner. [Background technology]

[0002] The abstract of Patent Document 1 states that "An air conditioner capable of properly cleaning an indoor heat exchanger is provided. The air conditioner (100) includes a refrigerant circuit (Q) in which a refrigerant circulates in a refrigeration cycle through a compressor (31), a condenser, an outdoor expansion valve (34), and an evaporator in that order, and a control unit that controls at least the compressor (31) and the outdoor expansion valve (34), one of the condenser and the evaporator being an outdoor heat exchanger (32), and the other being an indoor heat exchanger (12). The control unit causes the indoor heat exchanger (12) to function as an evaporator, freezes or condenses the indoor heat exchanger (12), and after freezing the indoor heat exchanger (12), increases the opening degree of the outdoor expansion valve 34." [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2018 / 198390 Summary of the Invention [Problem to be solved by the invention]

[0004] In the air conditioner described in Patent Document 1, of the first and second indoor heat exchangers, the refrigerant from the outdoor heat exchanger is first supplied to the first indoor heat exchanger. During freezing operation, the first indoor heat exchanger functions as a reheater (paragraph 0085), and therefore operates as a condenser (heat dissipation). However, depending on at least one of the room temperature and the outdoor air temperature, the first indoor heat exchanger may unintentionally operate as an evaporator (heat absorption) rather than a condenser, and the refrigeration cycle may not be established. As a result, even if freezing operation has started, the second indoor heat exchanger may unintentionally not freeze normally (i.e., freezing abnormality may occur). The problem that the present disclosure aims to solve is to provide a highly reliable air conditioner. [Means for solving the problem]

[0005] The air conditioner of the present disclosure comprises an indoor unit including an indoor heat exchanger composed of a first heat exchanger and a second heat exchanger connected to the first heat exchanger via a pressure reducing mechanism, and an indoor fan; a control device that performs a freezing operation to freeze the second heat exchanger by flowing refrigerant through the indoor heat exchanger so that the first heat exchanger functions as a condenser and the second heat exchanger functions as an evaporator; an outdoor unit including an outdoor fan that promotes heat exchange in the outdoor heat exchanger; an outdoor air temperature sensor that measures the temperature outside the room where the outdoor unit is installed; and a room temperature sensor that measures the temperature inside the room where the indoor unit is installed.When the control device determines, using at least one of a first measurement value by the outdoor air temperature sensor or a second measurement value by the room temperature sensor, that a predetermined condition is satisfied under which a freezing abnormality may occur in the second heat exchanger, the control device restricts the start of the freezing operation, or performs the freezing operation by slowing the rotation speed of at least one of the indoor fan or the outdoor fan that are driven during the freezing operation below the rotation speed when the predetermined condition is not satisfied.

[0006] According to the present disclosure, a highly reliable air conditioner can be provided. [Brief description of the drawings]

[0007] [Figure 1] 1 is a configuration diagram showing an air conditioner of the present disclosure. [Diagram 2] FIG. 2 is a block diagram showing a hardware configuration of a control device. [Diagram 3] FIG. 11 is a Mollier diagram when the refrigeration cycle is not established and abnormal freezing (unable to freeze normally) may occur in the heat exchange section 15b. [Figure 4] 11 shows the relationship between the first measurement value and the rotation speed of the outdoor fan. [Diagram 5] 10A and 10B are diagrams illustrating a method for determining a target value of the inlet temperature of a heat exchange unit based on room temperature and indoor humidity. [Figure 6] 11 is a graph showing the time relationship of the inlet temperature of the heat exchanger during freezing operation. [Figure 7] 11 is a flowchart when a freezing operation is performed. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, a form for carrying out the present disclosure (referred to as an embodiment) will be described with reference to the drawings. In the following description of one embodiment, other embodiments applicable to the one embodiment will also be described as appropriate. The present disclosure is not limited to the following one embodiment, and different embodiments can be combined with each other or modified as desired without significantly impairing the effects of the present disclosure. In addition, the same symbols will be used for the same members, and duplicate descriptions will be omitted. Furthermore, the same names will be used for members having the same functions. The contents shown are merely schematic, and for the sake of illustration, changes may be made from the actual configuration within a range that does not significantly impair the effects of the present disclosure, and some members may be omitted or modified between drawings. In addition, the same embodiment does not necessarily need to have all the configurations.

[0009] 1 is a configuration diagram showing an air conditioner 100 of the present disclosure. Both solid and dashed arrows indicate the direction of refrigerant flow. The solid arrows indicate the direction of refrigerant flow during heating operation. The dashed arrows indicate the direction of refrigerant flow during cooling operation and freezing operation. The dotted arrows indicate electrical signal lines.

[0010] The air conditioner 100 comprises an indoor unit 20 and an outdoor unit 30. Furthermore, the air conditioner 100 comprises a control device 50 that controls the operation of the air conditioner 100. For convenience of illustration in Fig. 1, the control device 50 is shown separately from the indoor unit 20 and the outdoor unit 30. The control device 50 may be provided in the indoor unit 20 or in the outdoor unit 30.

[0011] 2 is a block diagram showing a hardware configuration of the control device 50. The control device 50 is configured to include, for example, a central processing unit (CPU) 1001, a random access memory (RAM) 1002, a read only memory (ROM) 1003, an interface (I / F) 1004, a bus 1005, and the like. The CPU 1001, the RAM 1002, the ROM 1003, and the interface 1004 are connected, for example, via the bus 1005. The control device 50 is realized by a predetermined control program (for example, the air conditioning method of the present disclosure) stored in the ROM 1003 being expanded in the RAM 1002 and executed by the CPU 1001. Signals and information are exchanged between the control device 50 and various devices (such as servers), an external network, and the like, in terms of hardware, via the interface 1004.

[0012] Returning to FIG. 1, the indoor unit 20 includes an indoor heat exchanger 15, an indoor fan 16, and a pressure reducing mechanism 38. The indoor fan 16 is inverter controlled. By the rotation of the indoor fan 16, indoor air is sucked into the indoor unit 20, and after heat exchange with the indoor heat exchanger 15, it is blown out into the room. The indoor heat exchanger 15 is composed of a heat exchange section 15a (first heat exchange section) and a heat exchange section 15b (second heat exchange section). Although details will be described later, during freezing operation of the indoor unit 20, the heat exchange section 15a does not freeze and functions as a reheater, and only the heat exchange section 15b freezes. The heat exchange section 15b is connected to the heat exchange section 15a via a pressure reducing mechanism 38. The pressure reducing mechanism 38 is, for example, a two-way valve, an expansion valve, or the like.

[0013] The outdoor unit 30 includes a compressor 11, an outdoor heat exchanger 12, an outdoor fan 13, a four-way valve 17, and a pressure reducing mechanism 14 (such as an expansion valve). The compressor 11 and the outdoor fan 13 are inverter controlled. The outdoor fan 13 promotes heat exchange in the outdoor heat exchanger 12. The compressor 11, the outdoor heat exchanger 12, the pressure reducing mechanism 14, and the indoor heat exchanger 15 are connected by refrigerant piping, and a refrigerant flows through the refrigerant piping to form a refrigeration cycle. The compressor 11 compresses the refrigerant flowing through the outdoor heat exchanger 12, the pressure reducing mechanism 14, and the indoor heat exchanger 15. The compressor 11 is provided in the air conditioner 100. By switching the four-way valve 17, the direction of the refrigerant flow is controlled to either the solid arrow or the dashed arrow.

[0014] For example, during normal air conditioning operation (cooling operation, heating operation, etc.), the pressure reduction mechanism 38 (expansion mechanism) is fully opened. Meanwhile, the pressure reduction mechanism 14 (expansion mechanism) is appropriately throttled. Furthermore, during so-called reheat dehumidification, the pressure reduction mechanism 14 is fully opened. Meanwhile, the pressure reduction mechanism 38 is controlled to a predetermined opening degree. Note that the pressure reduction mechanism 38 may be configured to be switchable between a fully open state and a predetermined opening state, for example. Furthermore, during reheat dehumidification, there is no particular need for the pressure reduction mechanism 14 to be fully opened, as long as the refrigerant flows through the pressure reduction mechanism 14.

[0015] In the air conditioner 100 of the present disclosure, the control device 50 executes a freezing operation, for example, in response to a user's remote control operation. In the freezing operation, the refrigerant flows through the indoor heat exchanger 15 so that the outdoor heat exchanger 12 and the heat exchange section 15a function as a condenser, and the heat exchange section 15b functions as an evaporator. As a result, the control device 50 freezes the heat exchange section 15b. In the air flow caused by the driving of the indoor fan 16, the heat exchange section 15a is located downstream of the heat exchange section 15b. Therefore, during the freezing operation, the air that has been cooled by releasing heat to the heat exchange section 15b (evaporator) is warmed by the heat exchange section 15a (condenser, reheater). As a result, reheat dehumidification is performed in the indoor unit 20, and blowing out of particularly cold air into the room can be suppressed. This improves the comfort of the user.

[0016] In the freezing operation, the refrigerant flows in the direction indicated by the dashed arrow. In the freezing operation, the heat exchanger 15a located upstream in the refrigerant flow indicated by the dashed arrow among the heat exchangers 15a and 15b functions as a condenser (reheater) as described above. On the other hand, the heat exchanger 15b located downstream from the heat exchanger 15a functions as an evaporator (cooler) as described above. In the freezing operation, the pressure reducing mechanism 14 is controlled to be fully open or substantially fully open. Therefore, in the freezing operation, as the refrigerant flow in the refrigeration cycle, the gas refrigerant from the outdoor heat exchanger 12 is condensed in the heat exchanger 15a which serves as a condenser. As a result, the cooled (dehumidified) air is warmed. The refrigerant coming out of the heat exchanger 15a is depressurized by the pressure reducing mechanism 38, and the depressurized gas-liquid two-phase refrigerant is evaporated in the heat exchanger 15b which serves as an evaporator. As a result, the heat exchanger 15b freezes, and the air in the room is cooled and dehumidified. The refrigerant leaving the heat exchange section 15b flows toward the compressor 11.

[0017] The air conditioner 100 further includes an outdoor air temperature sensor 61, a room air temperature sensor 62, and a humidity sensor 63. The outdoor air temperature sensor 61 measures the temperature outside the room where the outdoor unit 30 is installed, and is installed in, for example, the outdoor unit 30. The room air temperature sensor 62 measures the temperature inside the room where the indoor unit 20 is installed, and is installed in, for example, the indoor unit 20. The humidity sensor 63 measures the humidity inside the room where the indoor unit 20 is installed, and is installed in, for example, the indoor unit 20.

[0018] The control device 50 uses at least one of the measured values ​​Tm1 (first measured value) by the outside air temperature sensor 61 and the measured value Tm2 (second measured value) by the room temperature sensor 62, Tm1, Tm2, ​​to determine whether or not a predetermined condition is satisfied. The predetermined condition is a condition under which a freezing abnormality may occur in the heat exchanger 15b. The freezing abnormality referred to here means that the temperature is too high and the heat exchanger 15b does not freeze at all, or that even if it freezes, the freezing is insufficient (it is not the desired freezing). Hereinafter, the same meaning will be used when referring to a freezing abnormality.

[0019] When it is determined that the predetermined condition is satisfied, the control device 50 restricts the start of the freezing operation, or executes the freezing operation by slowing down the rotation speed of at least one of the indoor fan 16 and the outdoor fan 13 that are driven during the freezing operation, compared to the rotation speed when the predetermined condition is not satisfied. For example, by restricting the stop, it is possible to avoid the execution of the freezing operation that causes unintended behavior. This improves the reliability of the air conditioner 100. In addition, by executing the freezing operation (second freezing operation described below) with a relatively slow rotation speed, it is possible to freeze the heat exchanger 15b according to the predetermined condition. This allows the cleaning effect of the heat exchanger 15b by freezing to be exerted as desired, and the reliability of the air conditioner 100 to be improved.

[0020] Hereinafter, the normal freezing operation performed when the specified conditions are not met may be referred to as the "first freezing operation," and the other freezing operation that may be performed when the specified conditions are met may be referred to as the "second freezing operation." The first freezing operation is, for example, the freezing operation described in Patent Document 1. On the other hand, when the first freezing operation and the second freezing operation are referred to collectively without any particular distinction, they are simply referred to as the "freezing operation."

[0021] The freezing operation is performed in response to a user's operation, for example, by using a remote control (not shown). The freezing operation may also be performed when a predetermined operation start condition is met, for example, when the accumulated operation time exceeds a predetermined time. However, as described above, depending on at least one of the outside air temperature and the room temperature, the refrigeration cycle may not be established, and the heat exchanger 15b may not freeze or may freeze insufficiently (i.e., abnormal freezing may occur).

[0022] Fig. 3 is a Mollier diagram when the refrigeration cycle is not established and abnormal freezing (unable to freeze normally) may occur in heat exchanger 15b. Fig. 3 is a Mollier diagram when heat exchanger 15a, which serves as a reheater in freezing operation, unintentionally absorbs heat (serves as an evaporator). The horizontal axis is specific enthalpy (h) and the vertical axis is pressure (p). Curve L1 is the saturated liquid line and curve L2 is the saturated vapor line.

[0023] At points A to B, the refrigerant evaporates in heat exchange section 15b, and the specific enthalpy increases. Then, at points B to C, compressor 11 compresses the refrigerant. At points C to D, the refrigerant condenses in outdoor heat exchanger 12, and the specific enthalpy decreases significantly. At points D to E, in heat exchange section 15a, the refrigerant unintentionally absorbs heat and evaporates, even though it would normally release heat and condense. At points E to A, the refrigerant expands in pressure reduction mechanism 38, and at points A to B, the refrigerant evaporates in heat exchange section 15b.

[0024] At the above points D to E, the heat exchanger 15a does not absorb heat as in FIG. 3, but actually functions as a reheater (condenser) by releasing heat. To fulfill this function, the inlet temperature of the indoor heat exchanger 15 (the temperature of the refrigerant supplied to the indoor heat exchanger 15) is higher than the room temperature. However, if the inlet temperature is lower than the room temperature, the phenomenon shown in FIG. 3 is likely to occur. In addition, the temperature of the refrigerant supplied to the indoor heat exchanger 15 is also affected by the outdoor air temperature. Then, due to the phenomenon shown in FIG. 3, heat is absorbed in both the heat exchanger 15a and the heat exchanger 15b. Furthermore, a pressure reducing mechanism 38 is provided between the heat exchanger 15a and the heat exchanger 15b, and the expanded refrigerant is supplied to the heat exchanger 15b. As a result, the refrigeration cycle is not established, and the possibility of freezing abnormality occurring in the heat exchanger 15b increases.

[0025] Therefore, in the present disclosure, when a predetermined condition (preferably a predetermined condition that causes a freezing abnormality) that may cause a freezing abnormality in the heat exchanger 15b is satisfied, a process different from the first freezing operation is performed. Specifically, for example, the freezing operation is normally performed by the user or the like operating a remote control, but when the predetermined condition is satisfied, for example, the start of the freezing operation is restricted. If the freezing operation (normal freezing operation; first freezing operation) is performed in an environment that satisfies such a predetermined condition, a freezing abnormality occurs in the heat exchanger 15b, and the desired freezing operation is not performed. Therefore, by restricting the start of the freezing operation and not performing the first freezing operation, only the desired freezing operation can be performed. In this case, since the freezing operation that is normally performed is not performed, for example, a display unit (not shown) provided on the indoor unit 20, the remote control, a mobile terminal held by the user, etc. (all not shown) can display information that the freezing operation is not performed.

[0026] However, depending on at least one of the measured values ​​Tm1 and Tm2, ​​a freezing abnormality may occur in the heat exchanger 15b in the first freezing operation (normal freezing operation), but if the second freezing operation (freezing operation of the present disclosure) is performed by a control different from that of the first freezing operation, the freezing operation may not occur (the heat exchanger 15b may be frozen normally). In such a case, the rotation speed of at least one of the indoor fan 16 or the outdoor fan 13 is slower than the rotation speed (the rotation speed in the first freezing operation) when the above-mentioned predetermined condition is not satisfied, and the freezing operation is performed. This makes it possible to suppress heat exchange in at least one of the indoor heat exchanger 15 or the outdoor heat exchanger 12, and to establish a refrigeration cycle. Therefore, it is possible to suppress the occurrence of a freezing abnormality in the heat exchanger 15b.

[0027] Among these, by slowing down the rotation speed of the indoor fan 16, the amount of heat exchange can be reduced and the cycle balance of the refrigeration cycle can be adjusted. Also, by slowing down the rotation speed of the outdoor fan 13, the amount of heat exchange can be similarly reduced and an excessive decrease in the temperature of the refrigerant supplied from the compressor 11 can be suppressed. This allows the heat exchanger 15a, which functions as a reheater, to sufficiently raise the temperature of the cold air.

[0028] When the above-mentioned predetermined conditions are satisfied, in order to execute the freezing operation (second freezing operation) by slowing the rotation speed of the outdoor fan 13 down compared to the rotation speed when the above-mentioned predetermined conditions are not satisfied, the control device 50 controls the rotation speed of the outdoor fan 13 based on the measured value Tm1 (first measured value). When the rotation speed of the outdoor fan 13 is constant, the heat exchange amount is usually constant as well, so that depending on the outdoor air temperature, the temperature of the refrigerant supplied to the heat exchanger 15a may not be the desired temperature. Therefore, by controlling the rotation speed of the outdoor fan 13 based on the measured value Tm1, the refrigerant temperature can be controlled to the desired temperature, and it is easy to prevent the temperature of the refrigerant supplied to the indoor heat exchanger 15 from becoming lower than room temperature.

[0029] FIG. 4 shows the relationship between the measured value Tm1 and the rotational speed of the outdoor fan 13. The horizontal axis represents the measured value Tm1, and the vertical axis represents the rotational speed of the outdoor fan 13. When the measured value Tm1 by the outside air temperature sensor 61 is equal to or higher than a predetermined value T5 (the fifth predetermined value), the control device 50 rotates the outdoor fan 13 at a speed V1 (the first speed). On the other hand, when the measured value Tm1 is less than the predetermined value T5, the control device 50 rotates the outdoor fan 13 at a speed V2 (the second speed). The speed V2 is lower than the speed V1.

[0030] By these controls, heat exchange can be promoted when the outside air temperature is relatively high (Tm1 ≧ T5) compared to when it is relatively low (Tm1 < T5). Thereby, the temperature of the refrigerant flowing from the outdoor heat exchanger 12 to the indoor heat exchanger 15 (the heat exchange section 15a) can be relatively lowered, and the refrigerant temperature can be sufficiently decreased by the decompression mechanism 38. Also, when the outside air temperature is relatively low (Tm1 < T5), the heat exchange amount can be suppressed compared to when it is relatively high (Tm1 ≧ T5). Thereby, it is possible to suppress the temperature of the refrigerant flowing into the heat exchange section 15a from decreasing excessively.

[0031] The predetermined conditions used for the determination by the control device 50 include, for example, at least one of the first conditions that the measured value Tm1 (the first measured value) of the outside air temperature is equal to or lower than a predetermined value T1 (the first predetermined value), or the measured value Tm2 (the second measured value) of the room temperature is equal to or higher than a predetermined value T2 (the second predetermined value). For example, when the outside air temperature is low, the temperature of the refrigerant supplied to the indoor heat exchanger 15 may be lower than the room temperature, and thus, the freezing operation cannot be properly executed. Therefore, in this case, either the freezing operation is not performed, or the above-described second freezing operation (for example, the freezing operation in which the rotational speed of the outdoor fan 13 is made slower than that of the first freezing operation) is performed. Which control to perform can be determined, for example, according to the specifications of the air conditioner 100. These points are the same, for example, when the room temperature is high, and when the outside air temperature is low and the room temperature is high.

[0032] The predetermined condition also includes a second condition in which the measured value Tm1 is lower than the measured value Tm2 and the difference between the measured values ​​Tm1 and Tm2 is equal to or greater than a predetermined value T3 (third predetermined value). For example, when the outside air temperature is low and the difference between the outside air temperature and the room temperature is too large (equal to or greater than the predetermined value T3), the refrigeration cycle does not function normally and freezing abnormalities are likely to occur in the heat exchanger 15b. In this case, therefore, either the freezing operation is not performed or the above-mentioned second freezing operation is performed. Which control is performed can be determined, for example, according to the specifications of the air conditioner 100.

[0033] The predetermined values ​​T1, T2, and T3 are all thresholds within a range where freezing abnormality may occur, and are, for example, but not limited to, fixed values. The predetermined values ​​T1, T2, and T3 can be determined in advance by experiments, simulations, etc., depending on, for example, the specifications of the air conditioner 100, the installation environment, etc.

[0034] In another embodiment, the predetermined condition includes a third condition that at least one of the measured values ​​Tm1, Tm2, ​​and Tm3 (third measured value) measured by the humidity sensor 63 is outside a predetermined range. The control device 50 restricts the start of the freezing operation when the third condition is satisfied. The predetermined ranges here refer to the ranges of room temperature, outdoor air temperature, and indoor humidity that do not cause freezing abnormality in the heat exchanger 15b. The predetermined ranges can be determined in advance, for example, by experiments, simulations, etc., depending on the specifications and installation environment of the air conditioner 100. By restricting the start of the freezing operation when the third condition is satisfied, the occurrence of freezing abnormality in the heat exchanger 15b can be suppressed.

[0035] In another embodiment, the predetermined condition includes a fourth condition in which all of the measured values ​​Tm1, Tm2, ​​and Tm3 are within a predetermined range, and Tm2 (the second measured value) is higher than Tm1 (the first measured value). The predetermined range here is, for example, the same as the predetermined range in the third condition. Therefore, the predetermined condition may include both the third condition and the fourth condition. When the fourth condition is satisfied, the control device 50 executes the second freezing operation by slowing down the rotation speed of at least one (preferably both) of the indoor fan 16 or the outdoor fan 13 compared to the rotation speed when the predetermined condition is not satisfied. In this way, the amount of heat exchange in the outdoor heat exchanger 12 and the indoor heat exchanger 15 can be suppressed, and the second freezing operation can be executed.

[0036] The control device 50 determines a target value of the inlet temperature, which is the refrigerant temperature at the inlet of the heat exchange section 15b (second heat exchange section) during the second freezing operation, based on at least the measured value Tm2. The "ease of lowering" the inlet temperature to the target value varies depending on the room temperature. For example, if the difference between the room temperature and the target temperature is relatively large, it is relatively difficult to lower the temperature, and if the difference between the room temperature and the target temperature is relatively small, it is relatively easy to lower the temperature. Therefore, by determining the target value of the inlet temperature using at least the measured value Tm2, ​​the load on the compressor 11, etc. can be reduced.

[0037] 5 is a diagram illustrating a method for determining a target value of the refrigerant temperature (inlet temperature) at the inlet of heat exchanger 15b based on room temperature and indoor humidity. The inlet temperature of heat exchanger 15b is measured, and a target temperature of the inlet temperature of heat exchanger 15b is determined based on room temperature and indoor humidity.

[0038] When the measured value Tm2 (measured value of room temperature; second measured value) is equal to or greater than a predetermined value T6 (sixth predetermined value), the control device 50 determines the target value of the inlet temperature to be temperature Ta (first temperature). When the measured value Tm2 is less than the predetermined value T6, the control device 50 determines the target value of the inlet temperature to be temperature Tb (second temperature). Temperature Tb is a temperature lower than temperature Ta. In this way, when the room temperature is relatively high, the inlet temperature is also relatively high, making it possible to reduce the load on the compressor 11, etc. On the other hand, when the room temperature is relatively low, the inlet temperature is also relatively low, making it easier to freeze the heat exchange section 15b.

[0039] The control device 50 further determines a target value for the inlet temperature based on a measured value Tm3 (third measured value) measured by the humidity sensor 63. The amount of condensed water generated during the freezing operation varies depending on the indoor humidity. Therefore, by determining the target value based on the humidity, the amount of condensed water can be made appropriate, and for example, the overflow of condensed water from a drain pan (not shown) during thawing after freezing can be suppressed.

[0040] Specifically, when the measured value Tm3 is equal to or greater than a predetermined value H7 (seventh predetermined value), the control device 50 sets the target value to the temperature Ta (first temperature). When the measured value Tm3 is less than the predetermined value H7, the control device 50 sets the target value to the temperature Tb (second temperature). As described above, the temperature Tb is lower than the temperature Ta. When the humidity is relatively high, the amount of condensed water is relatively large. In this case, the amount of condensed water can be intentionally suppressed by relatively increasing the inlet temperature. This can suppress the overflow of condensed water from the drain pan (not shown) during thawing after freezing. On the other hand, when the humidity is relatively low, the amount of condensed water is relatively small. In this case, the inlet temperature can be relatively low to promote condensation in the heat exchanger 15b. This can improve the cleaning effect of the heat exchanger 15b using the condensed water.

[0041] The predetermined values T6 and H7 are both values determined in advance from viewpoints such as ease of freezing and amount of dew condensation water, etc., and are not limited thereto but are, for example, fixed values. The predetermined values T6 and H7 can be determined in advance by experiments, simulations, etc. according to, for example, the specifications of the air conditioner 100, the installation environment, etc.

[0042] In the example shown in FIG. 5, when the measured value Tm2 of the room temperature satisfies T11 ≤ Tm2 ≤ T12 and the measured value Tm3 of the indoor humidity satisfies H13 ≤ Tm3 ≤ H14, the second freezing operation is executed. Therefore, these ranges are included in the above-mentioned third condition and fourth condition. Also, although not shown, the above-mentioned third condition and fourth condition also include the range of the outside air temperature. When the second freezing operation is executed, when the measured value Tm2 satisfies T11 ≤ Tm2 < T6 and the measured value Tm3 of the humidity satisfies H13 ≤ Tm3 < H7, the target value of the inlet temperature is set to the temperature Tb. On the other hand, when at least one of the measured values Tm2 and Tm3 does not satisfy these ranges, the target value of the inlet temperature is set to the temperature Ta.

[0043] FIG. 6 is a graph showing the relationship over time of the inlet temperature of the heat exchange unit 15b in the freezing operation. FIG. 6 exemplifies the case where the target value of the inlet temperature is the temperature Ta as an example, but when the target value is the temperature Tb, in the following description and the description of FIG. 6, the temperature Ta is replaced with the temperature Tb. Also, in the example of FIG. 6, at the start of the freezing operation, the rotational speed of the compressor 11 gradually decreases to the speed V4 after being at the speed V3 for a while, but the form of change of the rotational speed is not limited to this example. For example, the rotational speed may repeat increases and decreases according to the difference Δt. For example, the rotational speed may be increased when the difference ΔT is large and decreased when the difference ΔT is small. Also, the rotational speed may increase and decrease in a stepwise (staircase-like) manner instead of a gentle increase and decrease. In FIG. 6, the freezing operation starts at time t1.

[0044] The control device 50 compares the current (operating) inlet temperature of the heat exchanger 15b with the target temperature Ta to change the rotation speed of the compressor 11. Specifically, the larger the temperature difference ΔT between the inlet temperature of the heat exchanger 15b and the target temperature Ta, the higher the rotation speed. For example, assume that the upper limit of the rotation speed of the compressor 11 is Vmax and the lower limit is Vmin. Immediately after the start of the freezing operation at time t1, the difference ΔT is large, so the rotation speed is Vmax (an example of speed V3). As the freezing operation progresses and the difference ΔT becomes smaller (for example, it becomes less than a predetermined value that is a threshold value), the rotation speed decreases, and the freezing operation is continued at the reduced rotation speed V4. Therefore, the rotation speed varies between the upper limit Vmax and the lower limit Vmin according to the difference ΔT.

[0045] Also, for example, when the difference ΔT between the actual measured value of the inlet temperature of the heat exchanger 15b and the determined temperature Ta (an example of a target value) is equal to or greater than a predetermined value, the control device 50 drives the compressor 11 at a rotation speed of speed V3 (third speed). In the illustrated example, the speed V3 is the upper limit Vmax of the rotation speed as described above. On the other hand, when the difference ΔT is less than the predetermined value, the control device 50 drives the compressor 11 at a speed V4 (fourth speed). The speed V4 is a speed slower than the speed V3. The predetermined value to be compared with the difference ΔT can be determined in advance by experiments, simulations, etc., depending on, for example, the specifications of the air conditioner 100, the installation environment, etc.

[0046] In this way, excessive overshooting of the decreasing inlet temperature can be suppressed compared to when the compressor 11 is driven without changing the rotation speed. That is, by relatively slowing down the rotation speed when the inlet temperature approaches the temperature Ta, the temperature drop rate also becomes relatively slow. This allows the inlet temperature to reach the temperature Ta relatively slowly.

[0047] The freezing operation is performed by maintaining the inlet temperature of the heat exchanger 15b at or below temperature T8 for a predetermined time t5. Temperature T8 is higher than temperature Ta, and the difference between temperature T8 and temperature Ta is temperature T9. During time t4 when the compressor 11 is controlled for the freezing operation, the inlet temperature of the heat exchanger 15b is at or below temperature T8 for time t5. Time t5 is the time from time t2 to time t3. Time t5 is the time required to sufficiently freeze the condensed water present in the heat exchanger 15b. Time t5 can be determined in advance by experiment, simulation, etc., depending on the specifications of the air conditioner 100, the installation environment, etc.

[0048] In the example of Fig. 6, the inlet temperature reaches temperature T8 at time t2, and reaches temperature Ta at time t3. However, it is not necessary for the inlet temperature to reach temperature Ta at time t3, and the freezing operation may end when the inlet temperature is equal to or lower than temperature T8 but before it reaches temperature Ta, or control may be performed such that the temperature drop is stopped by stopping compressor 11 when it reaches temperature Ta. In addition, it is not strictly prohibited for the actual measured value of the inlet temperature to overshoot temperature Ta, and it is permissible as long as the overshoot is not excessive.

[0049] Fig. 7 is a flow chart for performing the freezing operation. The flow of Fig. 7 can be executed by the control device 50 (Fig. 1). Fig. 7 also shows an example in which the predetermined conditions do not include the first and second conditions, but include the third and fourth conditions.

[0050] For example, a command to start freezing operation is input to the control device 50 by a user operating the remote control, or when the accumulated operation time exceeds a predetermined time. The control device 50 determines whether or not the above-mentioned predetermined condition, i.e., either the third condition or the fourth condition, is met (step S1). If it is met (Yes), the control device 50 determines whether or not the third condition is met, i.e., whether or not to restrict the start of freezing operation (step S2). If the third condition is met, i.e., if the start of freezing operation is restricted (Yes), the flow shown in FIG. 7 ends without performing freezing operation.

[0051] On the other hand, if the start of the freezing operation is not restricted (No), the third condition is not satisfied, but the fourth condition is satisfied. Therefore, the second freezing operation is performed instead of the first freezing operation. Specifically, the control device 50 slows the rotation speed of at least one (preferably both) of the indoor fan 16 or the outdoor fan 13 to be slower than the rotation speed (the rotation speed in the first freezing operation) when the predetermined condition in step S1 is not satisfied, thereby freezing the heat exchanger 15b (step S21). After maintaining the predetermined time, the heat exchanger 15b is thawed (step S31), and the freezing operation ends.

[0052] In addition, in the above step S1, if the predetermined condition is not satisfied (No), the heat exchanger 15b is frozen as the first freezing operation (step S22). After maintaining the frozen state for a predetermined time, the heat exchanger 15b is thawed (step S32), and the freezing operation ends.

[0053] According to the air conditioner 100 of the present disclosure, when the refrigeration cycle is not established due to at least one of the room temperature and the outdoor temperature, the start of the freezing operation is restricted or the second freezing operation is performed under conditions different from the first freezing operation. This makes it possible to suppress the occurrence of freezing abnormalities and to increase the reliability of the air conditioner 100. [Explanation of symbols]

[0054] 100 Air conditioner 11 Compressor 12 Outdoor heat exchanger 13 Outdoor fan 14 Pressure reducing mechanism 15 Indoor heat exchanger 15a Heat exchange section (1st heat exchange section) 15b Heat exchange section (second heat exchange section) 16 Indoor Fan 17 Four-way valve 20 Indoor unit 30 Outdoor unit 38 Pressure reducing mechanism 50 Control device 61 Outside air temperature sensor 62 Room temperature sensor 63 Humidity Sensor H7 Predetermined value (7th predetermined value) L1 curve L2 curve t1 time t2 time t3 time t4 Time t5 Time T1 Predetermined value (first predetermined value) T2 Predetermined value (second predetermined value) T3 Predetermined value (third predetermined value) T5 predetermined value (5th predetermined value) T6 Predetermined value (6th predetermined value) T8 temperature T9 Predetermined value (9th predetermined value) Ta temperature (1st temperature) Tb temperature (second temperature) Tm1 measurement (first measurement) Tm2 measurement (second measurement) Tm3 measurement (third measurement) V1 speed (1st speed) V2 speed (2nd speed) V3 speed (3rd speed) V4 speed (4th speed) ΔT difference

Claims

1. an indoor unit including an indoor heat exchanger including a first heat exchange unit and a second heat exchange unit connected to the first heat exchange unit via a pressure reducing mechanism, and an indoor fan; a control device that executes a freezing operation in which a refrigerant flows through the indoor heat exchanger so that the first heat exchange unit functions as a condenser and the second heat exchange unit functions as an evaporator, thereby freezing the second heat exchange unit; an outdoor unit including an outdoor fan that promotes heat exchange in the outdoor heat exchanger; an outdoor air temperature sensor for measuring the temperature outside the room where the outdoor unit is installed; a room temperature sensor for measuring the temperature in a room where the indoor unit is installed; The control device includes: When it is determined that a predetermined condition that a freezing abnormality may occur in the second heat exchange unit is satisfied using at least one of the first measurement value by the outside air temperature sensor and the second measurement value by the room temperature sensor, Limiting the start of the freezing operation, or The rotation speed of at least one of the indoor fan and the outdoor fan driven during the freezing operation is set slower than the rotation speed when the predetermined condition is not satisfied, thereby performing the freezing operation. An air conditioner characterized by the above.

2. The predetermined condition is: the first measurement value is less than or equal to a first predetermined value, or the second measurement value is equal to or greater than a second predetermined value; At least one of the first conditions 2. The air conditioner according to claim 1 .

3. The predetermined condition is: The first measurement value is lower than the second measurement value, and the difference between the first measurement value and the second measurement value is equal to or greater than a third predetermined value. Including the second condition that 2. The air conditioner according to claim 1 .

4. A humidity sensor is provided to measure the humidity in the room, the predetermined condition includes a third condition that at least one of the first measurement value, the second measurement value, or a third measurement value measured by the humidity sensor is outside a predetermined range; The control device limits the start of the freezing operation when the third condition is satisfied.

2. The air conditioner according to claim 1 .

5. A humidity sensor is provided to measure the humidity in the room, the predetermined condition includes a fourth condition that the first measurement value, the second measurement value, and a third measurement value measured by the humidity sensor are all within a predetermined range, and the second measurement value is higher than the first measurement value; When the fourth condition is satisfied, the control device executes the freezing operation by slowing down the rotation speed of at least one of the indoor fan or the outdoor fan compared to the rotation speed when the predetermined condition is not satisfied.

2. The air conditioner according to claim 1 .

6. When the freezing operation is performed by making the rotation speed of the outdoor fan slower than the rotation speed when the predetermined condition is not satisfied, The control device controls the rotation speed of the outdoor fan based on the first measurement value.

2. The air conditioner according to claim 1 .

7. The control device includes: When the first measured value is equal to or greater than a fifth predetermined value, the outdoor fan is rotated at a first speed; When the first measured value is less than a fifth predetermined value, the outdoor fan is rotated at a second speed slower than the first speed.

7. The air conditioner according to claim 6.

8. The control device determines a target value of an inlet temperature, which is a refrigerant temperature at an inlet of the second heat exchange unit during the freezing operation, based on at least the second measurement value.

2. The air conditioner according to claim 1 .

9. The control device includes: When the second measured value is equal to or greater than a sixth predetermined value, the target value is determined to be a first temperature; When the second measured value is less than a sixth predetermined value, the target value is determined to be a second temperature lower than the first temperature.

9. The air conditioner according to claim 8.

10. A compressor that compresses the refrigerant flowing through the indoor heat exchanger, The control device includes: When a difference between the actual measured value of the inlet temperature and the determined target value is equal to or greater than a predetermined value, the compressor is driven at a third rotation speed; When the difference is less than the predetermined value, the compressor is driven at a fourth speed slower than the third speed.

9. The air conditioner according to claim 8.

11. A humidity sensor is provided to measure the humidity in the room, The control device further determines the target value based on a third measured value measured by the humidity sensor.

9. The air conditioner according to claim 8.

12. The control device includes: When the third measured value is equal to or greater than a seventh predetermined value, the target value is set to a first temperature; When the third measured value is less than a seventh predetermined value, the target value is set to a second temperature that is lower than the first temperature.

12. The air conditioner according to claim 11.

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