Air conditioners

Abstract

To provide an air conditioner capable of changing a lowest cooling capacity and improving comfort at the time of a cooling capacity operation.SOLUTION: An air conditioner is designed so as to change a lowest cooling capacity and is structured so as to set the time T2 till stop of a compressor 3 from a thermo-off time to be longer than the time T1 till the compressor 3 at the time of a normal capacity cooling operation is stopped at the time of an extremely low capacity cooling operation where the cooling capacity is lower than that at the time of the normal capacity cooling operation. According to such a structure, a room temperature from the thermo-off time till the compressor is driven again to restart the cooling operation can be settled within almost the same temperature region both at the time of the normal capacity cooling operation and the extremely low capacity cooling operation even when a room temperature lowering degree at the time of the extremely low capacity cooling operation is more gentle than the room temperature lowering degree at the time of the normal capacity cooling operation, and thereby comfortable cooling can be achieved.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present disclosure relates to an air conditioner that is capable of switching the minimum cooling capacity. [Background technology]

[0002] Patent Document 1 discloses an air conditioner capable of cooling and heating. This air conditioner is configured such that a heat storage tank is provided in the compressor provided in the outdoor unit, heat generated by the compressor is stored in the heat storage tank, and the stored heat is used for defrosting during heating operation, so that heating operation can be continued even during defrosting, and heating operation can be continued comfortably.

[0003] On the other hand, since the cooling operation does not utilize the heat storage tank, it can only perform the same cooling operation as an air conditioner that does not have a heat storage layer, and the minimum cooling operation during low load cooling operations is performed at the minimum cooling capacity that depends on the compressor's capacity, i.e., the minimum rotation speed that the compressor can produce. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2011-163663 A Summary of the Invention [Problem to be solved by the invention]

[0005] The present disclosure provides an air conditioner that is capable of changing the minimum cooling capacity when the cooling load is small, and that improves comfort when operating at each cooling capacity. [Means for solving the problem]

[0006] The air conditioner of the present disclosure is an air conditioner equipped with a compressor, a four-way valve, an outdoor heat exchanger, an expansion valve, an indoor heat exchanger, a refrigeration cycle connected to the four-way valve, and a control unit that switches the minimum cooling capacity of cooling operation between normal capacity cooling operation which depends on the minimum rotation speed of the compressor, and extremely low cooling capacity operation which has lower capacity, and the control unit is configured to make the time from thermo-off to compressor stopping during extremely low cooling capacity operation longer than the time from thermo-off to compressor stopping during normal capacity cooling operation, or to set the thermo-off temperature for switching to extremely low cooling capacity operation lower than the thermo-off temperature during normal capacity cooling operation. Effect of the Invention

[0007] In the air conditioner disclosed herein, when switching from normal capacity operation to extremely low cooling capacity operation, the degree of decrease in room temperature is slower than the degree of decrease in room temperature during normal capacity cooling operation, and the room temperature and humidity tend to increase during the thermo-off period when the compressor is restarted and cooling operation is resumed after operation is stopped due to thermo-off, but this can be eliminated by keeping the indoor temperature and humidity during thermo-off within approximately the same temperature range as during normal capacity cooling operation, and cooling can be performed as comfortably as in conventional normal capacity cooling operation. In other words, an air conditioner can be provided that provides comfortable cooling even when the minimum cooling capacity is switchable between normal capacity cooling operation and extremely low cooling capacity operation. [Brief description of the drawings]

[0008] [Figure 1] A configuration diagram of an air conditioner according to a first embodiment. [Diagram 2] A flowchart for explaining the switching operation between normal capacity cooling operation and very low capacity cooling operation of the air conditioner in the first embodiment. [Diagram 3] FIG. 11 is an explanatory diagram for explaining the operation when switching between normal capacity cooling operation and extremely low capacity cooling operation of the air conditioner in the first embodiment. [Figure 4] Configuration diagram of an air conditioner according to a second embodiment DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] (The knowledge and other information that formed the basis of this disclosure) At the time when the inventors came up with the present disclosure, there was known an air conditioner that was capable of continuing heating operation by utilizing a heat storage tank even during defrosting, as shown in Patent Document 1, but this air conditioner was not capable of utilizing the heat storage tank during cooling operation. Therefore, the air conditioner was configured to perform cooling operation in the same way as an air conditioner that does not have a heat storage layer, and the cooling operation capacity during low load operation, for example, when the room temperature is stable and the cooling load is small, is the minimum cooling capacity determined according to the compressor capacity, i.e., the minimum rotation speed that the compressor can produce.

[0010] Therefore, the inventors considered making effective use of the above-mentioned heat storage layer to enable the cooling operation capacity during cooling operation to be switched between minimum cooling capacity operation (hereinafter referred to as normal capacity cooling operation) which depends on the minimum rotation speed of the compressor, and cooling operation with an even lower cooling capacity (hereinafter referred to as extremely low cooling capacity operation).

[0011] As a result, it became possible to switch the minimum cooling operation capacity during cooling operation. However, it was discovered that if the minimum cooling capacity could be switched, the degree of decrease in room temperature during extremely low cooling capacity operation would be slower than the degree of decrease in room temperature during normal capacity cooling operation, and the room temperature and humidity would be higher during the period from when the operation was stopped due to thermo-off until the compressor was restarted and cooling operation was resumed, resulting in a problem that the same level of comfort as with conventional normal capacity cooling operation could not be obtained.

[0012] The present inventors have discovered such a problem and have come to form the subject of the present disclosure in order to solve the problem.

[0013] Therefore, the present disclosure provides an air conditioner that can provide comfortable cooling operation by ensuring that the room temperature during extremely low cooling capacity operation, when the room temperature is stable and low load, from when the thermostat is turned off to when operation is resumed, is within approximately the same range as during normal capacity cooling operation.

[0014] Hereinafter, the embodiments will be described in detail with reference to the drawings. However, more detailed explanation than necessary may be omitted. For example, detailed explanation of already well-known matters or duplicate explanation of substantially the same configuration may be omitted. This is to avoid the following explanation becoming more redundant than necessary and to facilitate understanding by those skilled in the art.

[0015] It should be noted that the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matter described in the claims.

[0016] (Embodiment 1) Hereinafter, the first embodiment will be described with reference to FIGS.

[0017] [1-1. Configuration] In FIG. 1, the air conditioner of this embodiment is configured by connecting an outdoor unit 1 and an indoor unit 2 with each other via refrigerant piping.

[0018] A compressor 3, a four-way valve 4, an outdoor heat exchanger 5, and an expansion valve 6 are provided inside the outdoor unit 1, and an indoor heat exchanger 7 is provided inside the indoor unit 2. The outdoor unit 1 and the indoor unit 2 are connected to each other via refrigerant piping to form a refrigeration cycle.

[0019] More specifically, the compressor 3 of the outdoor unit 1 is connected to the outdoor heat exchanger 5 via a refrigerant piping 8 provided with a four-way valve 4, and the outdoor heat exchanger 5 is connected to the indoor heat exchanger 7 via a refrigerant piping 8a, an expansion valve 6, and a refrigerant piping 9.

[0020] The indoor heat exchanger 7 of the indoor unit 2 is connected to the four-way valve 4 via a refrigerant pipe 10, and the three-way valve 1 The refrigerant piping 12 is branched by the refrigerant pipe 1, and is connected to the refrigerant suction side of the compressor 3 via an accumulator 13 for separating a liquid phase refrigerant from a gas phase refrigerant.

[0021] In addition, a heat storage tank 14 is provided around the compressor 3, and a heat storage heat exchanger 15 is provided inside the heat storage tank 14, and the heat storage tank 14 is filled with a heat storage material (e.g., an ethylene glycol aqueous solution) 16 for exchanging heat with the heat storage heat exchanger 15. The heat storage tank 14, the heat storage heat exchanger 15, and the heat storage material 16 constitute a heat storage device.

[0022] Here, the air conditioner is provided with a refrigerant circuit 17 for changing the heat exchange amount, which uses the heat storage heat exchanger 15 to change the heat exchange amount of the indoor heat exchanger 7 so as to reduce it. This refrigerant circuit 17 for changing the heat exchange amount is configured to flow refrigerant from the refrigerant pipe 9 to the compressor 3, bypassing the indoor heat exchanger 7.

[0023] In detail, the heat exchange amount changing refrigerant circuit 17 is formed by branching a branch refrigerant pipe 18 from between the expansion valve 6 of the refrigerant pipe 9 connected to the indoor heat exchanger 7 and the indoor heat exchanger 7, and is connected to the heat storage heat exchanger 15, that is, the heat storage heat exchanger 15 used as a capacity switching heat exchanger, via a refrigerant pipe 20 through a two-way valve (e.g., a solenoid valve) 19 serving as a capacity switching valve. The heat storage heat exchanger 15 is connected to the refrigerant pipe 12 via a refrigerant pipe 21, and is connected to the refrigerant suction side of the compressor 3 via an accumulator 13, thereby constituting the heat exchange amount changing refrigerant circuit 17.

[0024] The refrigerant pipes 12 and 20 are connected via a three-way valve 11. In this embodiment, the three-way valve 11 functions only as a two-way valve connecting the four-way valve 4 and the refrigerant pipes 12, and the refrigerant pipes 12 and 20 are isolated from each other.

[0025] In addition to the indoor heat exchanger 7, an indoor fan 7a, upper and lower blades (not shown), and left and right blades (not shown) are provided inside the indoor unit 2. The indoor heat exchanger 7 exchanges heat between the indoor air drawn into the indoor unit 2 by the indoor fan 7a and the refrigerant flowing inside the indoor heat exchanger 7, and blows out air warmed by the heat exchange into the room during heating, and blows out air cooled by the heat exchange into the room during cooling. The upper and lower blades change the direction of the air blown out from the indoor unit 2 up and down as necessary, and the left and right blades change the direction of the air blown out from the indoor unit 2 left and right as necessary.

[0026] In addition, the outdoor unit 1 is provided with an outdoor fan 5a and an outdoor air temperature detection means 23. An indoor temperature detection means 24 is provided.

[0027] The above-mentioned compressor 3, indoor fan 7a, upper and lower blades, left and right blades, four-way valve 4, expansion valve 6, two-way valve 19, outdoor fan 5a, outdoor air temperature detection means 23, indoor temperature detection means 24, etc. are electrically connected to a control unit 22 (e.g., a microcomputer), and the operation or behavior of the compressor 3, outdoor fan 5a, indoor fan 7a, upper and lower blades, left and right blades, four-way valve 4, and expansion valve 6 are controlled based on control signals from the control unit 22.

[0028] Furthermore, in this air conditioner, the control unit 22 controls the opening and closing of the two-way valve 19 based on the temperature difference X between the outdoor air temperature A detected by the outdoor air temperature detection means 23 and the indoor temperature B detected by the indoor temperature detection means 24, changes the flow of some or all of the refrigerant to bypass the indoor heat exchanger 7, and changes the time (described later) until the compressor 3 stops after thermo-off between normal capacity cooling operation and very low cooling capacity operation, thereby switching between normal capacity cooling operation and very low cooling capacity operation.

[0029] [1-2. Operation] The operation of the air conditioner configured as above will be described below. Note that the operation during heating operation is the same as that described in the prior art document 1, so the description will be omitted and the operation during cooling operation, which is a feature of the present invention, will be mainly described.

[0030] In FIG. 1, the white arrows indicate the refrigerant flow during normal capacity cooling operation, and the black arrows indicate the refrigerant flow during extremely low capacity cooling operation.

[0031] When cooling operation is started, cooling starts in normal capacity cooling operation. During normal capacity cooling operation, the refrigerant compressed by the compressor 3 becomes a high-temperature, high-pressure refrigerant and is sent to the outdoor heat exchanger 5 through the four-way valve 4. The refrigerant then exchanges heat with the outside air by the outdoor fan 5a, dissipating heat, becoming a high-pressure liquid refrigerant and being sent to the expansion valve 6. The refrigerant is decompressed in the expansion valve 6 to become a low-temperature, low-pressure two-phase refrigerant, and is sent to the indoor heat exchanger 7 through the refrigerant pipe 9 as the two-way valve 19 of the branch refrigerant pipe 18 is closed.

[0032] The indoor air drawn in by the indoor fan 7a passes through the indoor heat exchanger 7 and exchanges heat with the refrigerant, and the refrigerant absorbs heat from the indoor air and evaporates to become a low-temperature gas refrigerant. At this time, the indoor air that has absorbed heat from the refrigerant has a lower temperature and humidity, and is blown out into the room by the indoor fan 7a to cool the room. The gas refrigerant also passes through the refrigerant pipe 10 and enters the four-way valve 4, and returns to the compressor 3 via the refrigerant pipe 12 and the accumulator 13.

[0033] Normal capacity cooling operation is performed as described above. This normal capacity cooling operation is step S51 shown in the flow chart of Fig. 2. After that, cooling operation is performed as is, and a thermo-off determination is made in the next step S52. In the next step S53, it is determined whether the temperature difference X between the outdoor temperature A detected by the outdoor temperature detection means 23 and the indoor temperature B detected by the indoor temperature detection means 24, that is, the cooling load, is equal to or less than a predetermined temperature difference (cooling load) X that is determined arbitrarily.

[0034] If the temperature difference between the outdoor air temperature A and the indoor temperature B is equal to or less than the predetermined temperature difference X, it is determined that the cooling load is small, and the process proceeds to step S54, where the operation is switched to extremely low cooling capacity operation, which has a lower cooling capacity than normal capacity cooling operation, and cooling operation is performed with the minimum cooling capacity using the refrigerant circuit 17 for changing the heat exchange amount.

[0035] When the system switches to ultra-low cooling capacity operation and performs cooling operation, the low cooling capacity prevents overcooling during low loads and reduces the frequency of thermo-off, allowing for continued comfortable cooling.

[0036] Here, if the cooling load becomes extremely small while the extremely low cooling capacity operation is continuing, the thermo-off state becomes more likely, so the amount of dehumidification in the room decreases and the humidity increases.

[0037] Therefore, in this embodiment, if the cooling load becomes extremely small while the extremely low cooling capacity operation is continuing, the next step S55 judges whether the temperature difference between the outdoor temperature A detected by the outdoor temperature detection means 23 and the indoor temperature B detected by the indoor temperature detection means 24 is X1, which is extremely lower than the above X, and if it is judged that the condition is satisfied, that is, the cooling load has become extremely small, the process returns to step 51 and switches to normal capacity cooling operation, increasing the minimum cooling capacity and reducing the frequency of thermo-off to ensure the amount of dehumidification. If the condition is not satisfied in the above step S55, that is, if the cooling load has not become extremely small, the extremely low capacity cooling operation continues as it is, and comfortable cooling operation is continued while suppressing overcooling and the frequency of thermo-off.

[0038] Next, the specific operation of the extremely low capacity cooling operation will be described with reference back to FIG.

[0039] When the operation mode is switched to very low capacity cooling operation, the control unit 22 opens the two-way valve 19 for switching the cooling capacity. In this state, the two-phase refrigerant that flows from the compressor 3 to the four-way valve 4, the outdoor heat exchanger 5, and the expansion valve 6 flows to the indoor heat exchanger 7 as in normal capacity cooling operation, but some of the refrigerant is diverted from the branch refrigerant pipe 18 via the two-way valve 19 to the heat storage heat exchanger 15 of the refrigerant circuit 17 for changing the heat exchange amount.

[0040] The refrigerant diverted to the heat storage heat exchanger 15 exchanges heat in the heat storage heat exchanger 15, dissipates heat, becomes a high-pressure liquid refrigerant, and returns to the compressor 3 from the refrigerant pipes 21, 12 via the accumulator 13. That is, the refrigerant bypasses the indoor heat exchanger 7 and returns to the compressor 3 without exchanging heat with the indoor air in the indoor heat exchanger 7. In other words, the amount of refrigerant exchanging heat with the indoor air in the indoor heat exchanger 7 decreases.

[0041] This reduces the amount of heat exchanged with the indoor air in the indoor heat exchanger 7. In other words, the cooling capacity is reduced compared to the normal capacity cooling operation, and cooling is performed at a lower cooling capacity, i.e., at extremely low capacity cooling operation.

[0042] As described above, cooling is performed using normal capacity cooling operation and very low capacity cooling operation, but after the operation is stopped due to thermo-off, the room temperature begins to rise during the minimum compressor stop time required until the compressor 3 is restarted. As described above, if the conventional method is used, the room temperature during very low capacity cooling operation will be higher than the room temperature during normal capacity cooling operation, reducing comfort.

[0043] Figure 3 shows the change in room temperature during normal capacity cooling operation and during very low capacity cooling operation. In Figure 3, Y is the change in room temperature during normal capacity cooling operation, Z1 is the change in room temperature during very low capacity cooling operation assuming that the same control as during normal capacity cooling operation is performed, and Z2 is the change in room temperature during very low capacity cooling operation in this disclosure. The vertical axis indicates the room temperature, and the horizontal axis indicates time.

[0044] On the time axis, T0 indicates the time when the thermostat is off, and T1 indicates the time from the time T0 when the thermostat is off until the compressor 3 actually stops. The value 1 is arbitrarily determined in advance at the design stage. Also, L indicates the minimum compressor stop time (compressor 3 standby time) required from T1 when the compressor 3 stops until the compressor 3 is restarted.

[0045] As is clear from Figure 3 above, the degree of room temperature drop during very low capacity cooling operation is more gradual than the degree of room temperature drop during normal capacity cooling operation. Therefore, the room temperature during very low capacity cooling operation at time T1, when a time arbitrarily determined in advance at the design stage has elapsed from when the thermostat is off T0, is higher than the room temperature during normal capacity cooling. Therefore, when the standby time L of the compressor 3 has elapsed, the terminal temperature Z1e of the room temperature change line during very low capacity cooling operation Z1 is higher than the terminal temperature Ye of the room temperature change line during normal capacity cooling operation Y, resulting in a loss of comfort.

[0046] However, in the air conditioner of this embodiment, when the control unit 22 switches from normal capacity cooling operation to extremely low capacity cooling operation, the time from when the thermostat is off T0 to when the compressor 3 is actually stopped is lengthened from T1 to T2.

[0047] As a result, the change in room temperature during extremely low capacity cooling operation will be as shown in Z2, and even if the degree of decrease in room temperature is gradual, the terminal temperature Z2e of the room temperature change line will be approximately the same temperature as the terminal temperature Ye of the room temperature change line during normal capacity cooling operation Y, which falls within the desired target temperature range. Therefore, when operating at the ultra-lowest cooling capacity, the room temperature during the period from when the thermo is turned off until cooling operation is resumed will fall within the desired target temperature range, and cooling during extremely low capacity cooling operation can be achieved as comfortably as during normal capacity cooling operation.

[0048] [1-3. Effects, etc.] As described above, the air conditioner of the present disclosure comprises a compressor 3, a four-way valve 4, an outdoor heat exchanger 5, an expansion valve 6, an indoor heat exchanger 7, a refrigeration cycle connecting the four-way valve 4, and a control unit 22 that switches the minimum cooling capacity of the cooling operation between normal capacity cooling operation which depends on the minimum rotation speed of the compressor, and extremely low capacity cooling operation which has a lower capacity, and the control unit 22 is configured to make the time from when the thermostat is turned off to when the compressor 3 stops, when switching from normal capacity cooling operation to extremely low capacity cooling operation, longer than the time from when the thermostat is turned off to when the compressor 3 stops during the normal capacity cooling operation.

[0049] As a result, even if the degree of drop in room temperature during extremely low capacity cooling operation is slower than the degree of drop in room temperature during normal capacity cooling operation, the indoor temperature during the thermo-off period until compressor 3 is driven to resume cooling operation can be kept within approximately the same temperature range both during normal capacity cooling operation and extremely low capacity cooling operation, making it possible to operate the air conditioner in a comfortable environment even during extremely low capacity cooling operation.

[0050] Furthermore, in the air conditioner of the present disclosure, the refrigeration cycle is provided with a refrigerant circuit 17 for changing the heat exchange amount which changes the heat exchange amount of the indoor heat exchanger during cooling operation, and the refrigerant circuit 17 for changing the heat exchange amount has a capacity switching valve 19 which switches so that some or all of the refrigerant during cooling operation bypasses the indoor heat exchanger, and a capacity switching heat exchanger 15 which exchanges heat with the part of the refrigerant switched by the capacity switching valve 19, and is configured so that the capacity switching valve 19 is controlled by a control unit 22 to bypass some or all of the refrigerant to the capacity switching heat exchanger 15.

[0051] As a result, the amount of heat exchanged in the indoor heat exchanger 7 is reduced by the amount by which part or all of the refrigerant is bypassed to the capacity switching heat exchanger 15, and the cooling capacity is switched to extremely low capacity cooling operation, which has an even lower cooling capacity than normal capacity cooling operation. The minimum cooling capacity during extremely low capacity cooling operation can also be set freely by setting the amount of heat exchanged in the capacity switching heat exchanger 15.

[0052] Furthermore, in the air conditioner of the present disclosure, the capacity switching heat exchanger 15 is configured as a heat storage heat exchanger 15 that accumulates heat generated by the compressor 3 and uses it for defrosting during heating operation.

[0053] This makes it possible to switch the minimum cooling capacity by utilizing the heat storage heat exchanger 15 used for defrosting during heating operation, making it possible to continue heating while defrosting, and also providing comfortable cooling by switching the minimum cooling capacity.

[0054] Furthermore, in the air conditioner of the present disclosure, the control unit 22 is configured to switch from normal capacity cooling operation to very low capacity cooling operation when the difference between the indoor temperature and the outdoor temperature, that is, the cooling load, falls below a predetermined value.

[0055] As a result, when the difference between the indoor temperature and the outdoor temperature falls below a specified value, i.e., when the cooling load falls below a specified value, the system automatically switches to extremely low-capacity cooling operation, eliminating the need to switch capacities and improving usability. In addition, the frequency of thermo-off is reduced, allowing for stable cooling with minimal fluctuations in room temperature, thereby improving comfort.

[0056] Furthermore, in the air conditioner of the present disclosure, the control unit 22 is configured to return to normal capacity cooling operation when the difference between the indoor temperature and the outdoor temperature, i.e., the cooling load, falls below a second predetermined value which is even smaller than the predetermined value for switching to extremely low capacity cooling operation.

[0057] This reduces the frequency with which the thermo-off function goes into effect, ensuring sufficient dehumidification and improving comfort during cooling.

[0058] (Embodiment 2) [2-1. Configuration] The second embodiment will be described below with reference to FIG.

[0059] FIG. 4 is a configuration diagram of an air conditioner according to the second embodiment, and components that are the same as those in the first embodiment are given the same reference numbers and descriptions thereof will be omitted.

[0060] In the second embodiment, the heat exchange amount changing refrigerant circuit 17A is configured as follows. That is, in the first embodiment, a two-way valve (capacity switching valve) 19 and a heat storage heat exchanger 15 (capacity switching heat exchanger) are provided to bypass the indoor unit 2 and allow some or all of the refrigerant to flow, but in the heat exchange amount changing refrigerant circuit 17A in the second embodiment, the branch refrigerant pipe 18 and the two-way valve 19 are eliminated, and a three-way valve 11A provided between the refrigerant pipe 12 and the refrigerant pipe 20 is used as a capacity switching valve so that some or all of the refrigerant after flowing through the indoor heat exchanger 7 flows to the heat storage heat exchanger 15 (capacity switching heat exchanger).

[0061] Specifically, the heat exchange amount changing refrigerant circuit 17A is configured by connecting the three-way valve 11A serving as a capacity switching valve to the heat storage heat exchanger 15 serving as a capacity switching heat exchanger via the refrigerant piping 20, and then connecting it to the refrigerant suction side of the compressor 3 via the refrigerant piping 21, the refrigerant piping 12, and the accumulator 13. As a result, the three-way valve 11A serving as a capacity switching valve diverts part or all of the refrigerant from the four-way valve 4 to the heat storage heat exchanger 15 (capacity switching heat exchanger) connected to the refrigerant piping 20 during extremely low capacity cooling operation.

[0062] On the other hand, the control unit 22 detects the outdoor air temperature A detected by the outdoor air temperature detection means 23 and the indoor air temperature detection means 24. and controls three-way valve 11A based on temperature difference X between the indoor temperature B detected by the three-way valve 11A, and changes and controls so that part or all of the refrigerant flowing through three-way valve 11A is also diverted to refrigerant pipe 20. As in the first embodiment, the time from thermo-off time 0 after thermo-off to when compressor 3 is actually stopped is changed between normal capacity cooling operation and very low capacity cooling operation, so as to switch between normal capacity cooling operation and very low capacity cooling operation.

[0063] [2-2. Operation] The operation of the air conditioner configured as above will now be described.

[0064] In the second embodiment, the normal capacity cooling operation is the same as in the first embodiment, but the extremely low capacity cooling operation is performed as follows.

[0065] That is, switching from normal capacity cooling operation to very low capacity cooling operation is performed based on the temperature difference X between the outdoor air temperature A and the room temperature B, as in the first embodiment, and when switching to very low capacity cooling operation, the control unit 22 also opens the three-way valve 11A for switching the cooling capacity to the refrigerant piping 20 side connected to the heat storage heat exchanger 15.

[0066] In this state, the two-phase refrigerant that flows from the compressor 3 to the four-way valve 4, the outdoor heat exchanger 5, and the expansion valve 6 flows directly to the indoor heat exchanger 7 to exchange heat with the indoor air, and then passes through the four-way valve 4 to reach the three-way valve 11A, which serves as a capacity switching valve. The refrigerant that has reached the three-way valve 11A returns to the compressor 3 from the refrigerant piping 12 via the accumulator 13, but some of the refrigerant flows into the refrigerant piping 20 at the three-way valve 11A and is diverted to the heat storage heat exchanger 15, which serves as a capacity switching heat exchanger.

[0067] A portion of the refrigerant diverted to the heat storage heat exchanger 15 exchanges heat with the heat storage material 16 to release heat, turns into high-pressure liquid refrigerant, and returns to the compressor 3 through the refrigerant pipe 21 and the accumulator 13.

[0068] This reduces the amount of heat exchanged with the indoor air in the indoor heat exchanger 7. In other words, the cooling capacity of the indoor heat exchanger 7 is reduced compared to the cooling capacity during normal operation, and cooling is performed with a lower cooling capacity, i.e., extremely low capacity cooling operation.

[0069] In this embodiment, the amount of refrigerant flowing to the indoor heat exchanger 7 can be changed by controlling the opening of the three-way valve 11 toward the refrigerant piping 20, thereby changing the amount of heat exchanged in the indoor heat exchanger 7 and adjusting the minimum cooling capacity. The same effect can be obtained by opening the three-way valve 11 shown in embodiment 1 also toward the refrigerant piping 20 and controlling the opening.

[0070] Correction to the terminal temperature V2e of the room temperature change curve during extremely low capacity cooling operation is performed in the same manner as in embodiment 1, and comfort is improved by making the room temperature when the thermo is off during normal capacity cooling operation and extremely low capacity cooling operation approximately the same temperature. [2-3. Effects, etc.] The air conditioner of the present disclosure is equipped with a refrigerant circuit 17A for changing the heat exchange amount that changes the heat exchange amount of the indoor heat exchanger 7 during cooling operation, and the refrigerant circuit 17A for changing the heat exchange amount has a capacity switching valve 11A that diverts some or all of the refrigerant after passing through the indoor heat exchanger 7, and a capacity switching heat exchanger 15 that exchanges heat with the refrigerant diverted by the capacity switching valve, and is configured so that the capacity switching valve 11A is controlled by a control unit 22 to divert some or all of the refrigerant after passing through the indoor heat exchanger to the capacity switching heat exchanger 15.

[0071] As a result, part or all of the refrigerant after passing through the indoor heat exchanger is diverted to the capacity switching heat exchanger 15 and heat exchanged in the capacity switching heat exchanger 15, thereby reducing the amount of heat exchange in the indoor heat exchanger 7, and the cooling capacity can be switched to extremely low capacity cooling operation, which has an even lower cooling capacity than normal capacity cooling operation. In this case, there is no need to provide a separate refrigerant circuit that bypasses the indoor heat exchanger 7, simplifying the configuration, and by setting the amount of heat exchange in the capacity switching heat exchanger 15, the minimum cooling capacity during extremely low capacity cooling operation can be set as desired.

[0072] (Other embodiments) As described above, the first and second embodiments have been described as examples of the technology disclosed in this application. However, the technology in this disclosure is not limited to these, and can be applied to embodiments in which modifications, substitutions, additions, omissions, etc. are made. In addition, it is also possible to combine the components described in the first embodiment above to create new embodiments.

[0073] Therefore, some other embodiments will be exemplified below.

[0074] In the first and second embodiments, a configuration is shown in which the time from thermo-off to resumption of cooling operation is made different between very low capacity cooling operation and normal capacity cooling operation, in order to keep the indoor temperature when the thermo is off during normal capacity cooling operation and very low capacity cooling operation within approximately the same range.

[0075] However, this can also be achieved by changing the thermo-off temperature itself, for example. That is, the same effect can be obtained by setting the thermo-off temperature for switching to extremely low capacity cooling operation lower than the thermo-off temperature during normal capacity cooling operation.

[0076] Also, a combination of changing the thermo-off temperature itself and varying the time from thermo-off to resumption of cooling operation may be carried out.

[0077] This combination method makes it possible to more accurately keep the indoor temperature within the same range when operation is restarted.

[0078] In any of the above cases, if the thermo-off temperature, the time from thermo-off to resumption of cooling operation, and combinations of these are determined through experiments according to cooling load conditions such as the size of the room in which the air conditioner is installed, and these are made switchable when the equipment is installed, the room temperature when the thermo is off can be kept within a certain range more accurately, resulting in a more comfortable air conditioner.

[0079] In addition, as a method for switching the cooling capacity in two stages, an example has been given in which the air conditioner having the heat storage tank 14 is effectively utilized. However, the method can also be realized in an air conditioner that does not have the heat storage tank 14.

[0080] For example, a refrigerant circuit 17 for changing the heat exchange amount shown in the first embodiment or a refrigerant circuit 17A for changing the heat exchange amount shown in the second embodiment may be provided to bypass the indoor heat exchanger 7 shown in the first embodiment, and the capacity switching heat exchanger 15 downstream of the refrigerant piping 20 of the refrigerant circuit 17 or 17A for changing the heat exchange amount may simply be routed around the compressor.

[0081] Alternatively, the capacity switching heat exchanger 15 downstream of the refrigerant piping 20 of the refrigerant circuit 17 for changing the heat exchange amount that bypasses the indoor heat exchanger 7 shown in embodiment 1 or the refrigerant circuit 17A for changing the heat exchange amount shown in embodiment 2 may be provided downstream of the outdoor fan 5a to exchange heat with the air from the outdoor fan 5a, and various configurations are possible.

[0082] In this way, in the present invention, the configuration for switching the minimum cooling capacity between two stages does not necessarily have to be a heat storage type air conditioner having a heat storage tank 14, and any configuration is acceptable as long as the heat exchange of the refrigerant that exchanges heat in the indoor heat exchanger 7 can also be performed in parts other than the indoor heat exchanger.

[0083] The air conditioner according to the present invention has been described above using the above-mentioned embodiments, but the present invention is not limited to this, and various modifications, substitutions, additions, omissions, etc. can be made within the scope of the claims or their equivalents.

[0084] Furthermore, although the present disclosure describes an air conditioner that has a four-way valve and can switch between heating and cooling, it goes without saying that the disclosure can also be applied to a cooling-only unit that does not have a four-way valve. [Industrial Applicability]

[0085] The air conditioner disclosed herein can cool the room by keeping the indoor temperature within approximately the same temperature range during the thermo-off period until the cooling operation is resumed, whether in normal capacity cooling operation or in extremely low capacity cooling operation, and can provide comfortable cooling in both normal capacity cooling operation and extremely low capacity cooling operation. Therefore, the air conditioner can be widely used for both home and commercial use. [Explanation of symbols]

[0086] 1 Outdoor unit 2 Indoor unit 3. Compressor 4. Four-way valve 5 Outdoor heat exchanger 5a Outdoor fan 6 Expansion valve 7 Indoor heat exchanger 7a Indoor fan 8 Refrigerant piping 8a Refrigerant piping 9 Refrigerant piping 10 Refrigerant piping 11 Three-way valve (capacity changeover valve) 11A Three-way valve (capacity switching valve) 12 Refrigerant piping 13 Accumulator 14 Heat storage tank 15 Heat storage heat exchanger (capacity switching heat exchanger) 16 Heat storage material 17, 17A Refrigerant circuit for changing heat exchange amount 18 Branch refrigerant piping 19 Two-way valve (capacity changeover valve) 20 Refrigerant piping 21 Refrigerant piping 22 Control section 23 Outside air temperature detection means 24 Indoor temperature detection means

Claims

1. An air conditioner comprising: a compressor, a four-way valve, an outdoor heat exchanger, an expansion valve, an indoor heat exchanger, and a refrigeration cycle connected to the four-way valve; and a control unit that switches the minimum cooling capacity of cooling operation between normal capacity cooling operation which depends on the minimum rotation speed of the compressor and very low capacity cooling operation which has lower capacity than normal capacity cooling operation, wherein the control unit is configured to switch from normal capacity cooling operation to very low capacity cooling operation when the difference between the indoor temperature and the outdoor temperature falls below a predetermined value, and during the very low capacity cooling operation, the time from thermo-off to the compressor stopping is made longer than the time from thermo-off to the compressor stopping during the normal capacity cooling operation, or the thermo-off temperature during the very low capacity cooling operation is made lower than the thermo-off temperature during the normal capacity cooling operation.

2. 2. The air conditioner of claim 1, wherein the refrigeration cycle includes a refrigerant circuit for changing the heat exchange amount that changes the heat exchange amount of the indoor heat exchanger during cooling operation, the refrigerant circuit for changing the heat exchange amount having a capacity switching valve that switches so that some or all of the refrigerant bypasses the indoor heat exchanger during cooling operation, and a capacity switching heat exchanger that exchanges heat with the refrigerant switched by the capacity switching valve, and the control unit controls the capacity switching valve to bypass some or all of the refrigerant to the capacity switching heat exchanger.

3. 2. The air conditioner of claim 1, wherein the refrigeration cycle includes a refrigerant circuit for changing the heat exchange amount that changes the heat exchange amount of the indoor heat exchanger during cooling operation, the refrigerant circuit for changing the heat exchange amount having a capacity switching valve that diverts some or all of the refrigerant after passing through the indoor heat exchanger, and a capacity switching heat exchanger that exchanges heat with the refrigerant diverted by the capacity switching valve, and the control unit controls the capacity switching valve to divert some or all of the refrigerant after passing through the indoor heat exchanger to the capacity switching heat exchanger.

4. 4. The air conditioner according to claim 2, wherein the capacity switching heat exchanger is a heat storage heat exchanger which stores heat generated by the compressor and uses it for defrosting during heating operation.

5. The air conditioner according to claims 1 to 4, wherein the control unit is configured to return to normal capacity cooling operation when the difference between the indoor temperature and the outdoor temperature falls below a second predetermined value which is even smaller than the predetermined value for switching to extremely low capacity cooling operation.

6. In an air conditioner comprising a compressor, a four-way valve, an indoor heat exchanger, an expansion valve, an outdoor heat exchanger, a refrigeration cycle connected to the four-way valve, and a control unit which controls the compressor, the four-way valve, and the expansion valve, and which performs cooling operation by changing the flow of refrigerant through control of the four-way valve by the control unit, a heat exchange amount changing refrigerant circuit is provided which changes the heat exchange amount of the indoor heat exchanger during the cooling operation, the heat exchange amount changing refrigerant circuit is configured with a capacity switching valve which switches the flow of a portion of the refrigerant, and a capacity switching heat exchanger which exchanges heat with a portion or all of the refrigerant switched by the capacity switching valve, and the control unit controls the capacity switching valve so that a portion or all of the refrigerant flows to the capacity switching heat exchanger. and a control unit that controls a valve to switch the minimum cooling capacity of the cooling operation between normal capacity cooling operation, which depends on the minimum rotation speed of the compressor, and very low capacity cooling operation, which has a lower capacity than the normal capacity cooling operation, wherein the control unit is configured to switch from normal capacity cooling operation to very low capacity cooling operation when the difference between the indoor temperature and the outdoor temperature falls below a predetermined value, and the control unit is configured, when switching from normal capacity cooling operation to very low capacity cooling operation, to make the time from thermo-off to the compressor stopping longer than the time from thermo-off to the compressor stopping during normal capacity cooling operation, or to set the thermo-off temperature at which to switch to very low capacity cooling operation lower than the thermo-off temperature during normal capacity cooling operation.

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