Air conditioner

Abstract

An air conditioner according to the present invention comprises: a refrigerant circuit having a compressor, a refrigerant flow path switching device, a heat source-side heat exchanger, a throttle device, and a load-side heat exchanger; and a control device for controlling the refrigerant circuit. The control device can switch between and execute a heating operation and a defrosting operation, and the control device is configured so as to start the defrosting operation when a defrosting start condition is satisfied during execution of the heating operation and end the defrosting operation when a defrosting end condition is satisfied during execution of the defrosting operation. The defrosting end condition includes a first time condition that is satisfied when the execution time of the defrosting operation exceeds a first threshold time. The defrosting start condition and / or the defrosting end condition in the next defrosting operation differs between a case in which the defrosting operation has ended by satisfying the first time condition and a case in which the defrosting operation has ended by satisfying a defrosting end condition other than the first time condition.

Description

air conditioning equipment

[0001] The present disclosure relates to an air conditioning apparatus.

[0002] Patent Document 1 discloses an air conditioner. This air conditioner has a refrigerant circuit in which a refrigerant circulates through a compressor, an indoor heat exchanger, a pressure reduction mechanism, and an outdoor heat exchanger in this order during heating operation, a switching valve connected to the refrigerant circuit for switching the flow direction of the refrigerant discharged from the compressor, an outdoor fan, and a controller for controlling a defrosting operation. During defrosting operation, the controller stops the outdoor fan and directs the refrigerant discharged from the compressor toward the outdoor heat exchanger using the switching valve. The defrosting operation is executed when a certain time has elapsed since the previous defrosting operation and the outdoor air temperature and the outdoor heat exchanger temperature have fallen below a predetermined temperature.

[0003] JP 2010-121789 A

[0004] However, in the above-described air conditioner, if a large amount of frost forms on the outdoor heat exchanger, the frost may remain unmelted after the defrosting operation, which can result in a decrease in the performance of the outdoor heat exchanger.

[0005] The present disclosure has been made to solve the above-mentioned problems, and aims to provide an air conditioner that can suppress performance degradation of a heat source-side heat exchanger.

[0006] The air conditioning apparatus according to the present disclosure comprises a refrigerant circuit having a compressor, a refrigerant flow switching device, a heat source side heat exchanger, a throttling device, and a load side heat exchanger, and a control device that controls the refrigerant circuit, wherein the control device is capable of switching between a heating operation in which the heat source side heat exchanger functions as an evaporator and a defrost operation in which the heat source side heat exchanger functions as a condenser, and wherein the control device is configured to start the defrost operation when a defrost start condition is satisfied during the heating operation, and to terminate the defrost operation when a defrost end condition is satisfied during the defrost operation, wherein the defrost end condition includes a first time condition that is satisfied when the execution time of the defrost operation exceeds a first threshold time, and wherein at least one of the defrost start condition and the defrost end condition for the next defrost operation is different between a case in which the defrost operation is terminated because the first time condition is satisfied and a case in which the defrost operation is terminated because a defrost end condition other than the first time condition is satisfied.

[0007] According to the present disclosure, it is possible to suppress a decrease in performance of the heat source side heat exchanger.

[0008] 1 is a schematic circuit configuration diagram showing an example of a circuit configuration of an air conditioning apparatus according to Embodiment 1. FIG. 1 is a refrigerant circuit diagram showing the flow of refrigerant in a cooling operation mode in an air conditioning apparatus according to Embodiment 1. FIG. 2 is a refrigerant circuit diagram showing the flow of refrigerant in a heating operation mode in an air conditioning apparatus according to Embodiment 1. FIG. 3 is a flowchart showing an example of the flow of switching processing between heating operation and defrost operation executed by a control device in an air conditioning apparatus according to Embodiment 1. FIG. 4 is a flowchart showing an example of the flow of defrost start condition determination processing executed by a control device in an air conditioning apparatus according to Embodiment 1. FIG. 5 is a flowchart showing another example of the flow of defrost start condition determination processing executed by a control device in an air conditioning apparatus according to Embodiment 1. FIG. 6 is a flowchart showing a flow of defrost operation processing according to a comparative example of Embodiment 1. FIG. 7 is a flowchart showing an example of the flow of defrost operation processing executed by a control device in an air conditioning apparatus according to Embodiment 1. FIG. 8 is a flowchart showing a generalized flow of defrost operation processing in an air conditioning apparatus according to Embodiment 1. FIG. 9 is a flowchart showing an example of the flow of defrost operation processing executed after flag setting in an air conditioning apparatus according to Embodiment 1. FIG. 10 is a flowchart showing an example of the flow of heating operation processing executed after flag setting in an air conditioning apparatus according to Embodiment 2. FIG. 11 is a schematic circuit configuration diagram showing an example of a circuit configuration of an air conditioning apparatus according to Embodiment 3. Fig. 10 is a flowchart showing an example of the flow of defrosting operation processing executed by a control device in an air conditioning apparatus according to embodiment 3. Fig. 11 is a schematic circuit configuration diagram showing a part of the circuit configuration of an air conditioning apparatus according to embodiment 4. Fig. 11 is a flowchart showing an example of the flow of defrosting start condition determination processing executed by a control device in an air conditioning apparatus according to embodiment 4. Fig. 12 is a flowchart showing another example of the flow of defrosting start condition determination processing executed by a control device in an air conditioning apparatus according to embodiment 4.

[0009] Embodiments of the present disclosure will be described below with reference to the drawings. The present disclosure is not limited to the following embodiments and can be modified in various ways without departing from the spirit and scope of the present disclosure. Furthermore, the present disclosure includes all possible combinations of the configurations shown in the following embodiments. In particular, the combinations of components are not limited to the combinations in each embodiment; components described in one embodiment can be applied to another embodiment. In the following description, directional terms (e.g., "up," "down," "right," "left," "front," "rear," etc.) are used as appropriate to facilitate understanding, but these are for explanatory purposes and do not limit the present disclosure. In each drawing, components designated with the same reference numerals are identical or equivalent, and this applies throughout the entire specification. Note that the relative dimensional relationships or shapes of each component in each drawing may differ from those in actuality.

[0010] Embodiment 1. An air conditioner according to embodiment 1 will be described. Fig. 1 is a schematic circuit diagram showing an example of the circuit configuration of an air conditioner according to this embodiment. The air conditioner 100 performs air conditioning using a refrigeration cycle by circulating a refrigerant. As shown in Fig. 1, the air conditioner 100 has an outdoor unit 1, an indoor unit 2, and a main refrigerant pipe 3. The outdoor unit 1 and the indoor unit 2 are connected via the main refrigerant pipe 3. The refrigerant circuit of the air conditioner 100 is made up of a refrigerant circuit on the outdoor unit 1 side, a refrigerant circuit on the indoor unit 2 side, the main refrigerant pipe 3, etc.

[0011] [Outdoor unit 1] The outdoor unit 1 is equipped with a compressor 10, a refrigerant flow switching device 11 such as a four-way valve, a heat source side heat exchanger 12, and an accumulator 13. The compressor 10, the refrigerant flow switching device 11, the heat source side heat exchanger 12, and the accumulator 13 are connected via refrigerant piping 4 to form a refrigerant circuit on the outdoor unit 1 side.

[0012] The compressor 10 draws in a low-temperature, low-pressure refrigerant and compresses it to a high-temperature, high-pressure state. The compressor 10 may be configured as a capacity-controllable inverter compressor, etc. The refrigerant flow switching device 11 switches the refrigerant flow between cooling operation and heating operation.

[0013] The heat source-side heat exchanger 12 functions as a condenser during cooling operation and as an evaporator during heating operation. In the heat source-side heat exchanger 12, heat is exchanged between the refrigerant and air supplied from a blower (not shown). The accumulator 13 is provided on the suction side of the compressor 10. The accumulator 13 stores excess refrigerant that occurs due to differences in operating conditions between cooling operation and heating operation, or excess refrigerant that occurs due to transient changes in operation.

[0014] The outdoor unit 1 is provided with a first pressure detection device 20 and a second pressure detection device 21. The first pressure detection device 20 is provided on the refrigerant piping 4 connecting the compressor 10 and the refrigerant flow switching device 11. The first pressure detection device 20 detects the pressure P1 of the high-temperature, high-pressure refrigerant discharged from the compressor 10. The second pressure detection device 21 is provided on the refrigerant piping 4 connecting the refrigerant flow switching device 11 and the accumulator 13. The second pressure detection device 21 detects the pressure P2 of the low-temperature, low-pressure refrigerant drawn into the compressor 10.

[0015] The outdoor unit 1 is also provided with a first temperature detecting device 22 and a second temperature detecting device 23. The first temperature detecting device 22 is provided in the refrigerant piping 4 connecting the compressor 10 and the refrigerant flow switching device 11. The first temperature detecting device 22 detects a temperature T1 of the high-temperature, high-pressure refrigerant discharged from the compressor 10. The second temperature detecting device 23 is provided in the refrigerant piping 4 connecting the refrigerant flow switching device 11 and the accumulator 13. The second temperature detecting device 23 detects a temperature T2 of the low-temperature, low-pressure refrigerant drawn into the compressor 10. Each of the first temperature detecting device 22 and the second temperature detecting device 23 is constituted by a thermistor or the like.

[0016] [Indoor unit 2] The indoor unit 2 is equipped with a load-side heat exchanger 40 and an expansion device 41. The load-side heat exchanger 40 and the expansion device 41 are connected via refrigerant piping to form a refrigerant circuit on the indoor unit 2 side. The indoor unit 2 is connected to the outdoor unit 1 via a main refrigerant pipe 3.

[0017] The load-side heat exchanger 40 functions as an evaporator during cooling operation and as a condenser during heating operation. In the load-side heat exchanger 40, heat is exchanged between the refrigerant and air supplied from an indoor blower (not shown), generating air for heating or air conditioning to be supplied to the indoor space. The throttling device 41 functions as a pressure reducing valve or expansion valve, and reduces the pressure of the refrigerant to expand it. The throttling device 41 is configured as a device whose opening can be variably adjusted under the control of the control device 30, such as an electronic expansion valve.

[0018] The indoor unit 2 is provided with a third temperature detecting device 50, a fourth temperature detecting device 51, and a fifth temperature detecting device 52. The third temperature detecting device 50 detects the temperature of refrigerant flowing into the load-side heat exchanger 40 during cooling operation. The third temperature detecting device 50 is provided in the refrigerant piping connecting the expansion device 41 and the load-side heat exchanger 40. The fourth temperature detecting device 51 detects the temperature of refrigerant flowing out of the load-side heat exchanger 40 during cooling operation. The fourth temperature detecting device 51 is provided in the refrigerant piping on the opposite side of the expansion device 41 with respect to the load-side heat exchanger 40. The fifth temperature detecting device 52 detects the indoor air temperature. The fifth temperature detecting device 52 is provided in the air intake section of the load-side heat exchanger 40. Each of the third temperature detecting device 50, the fourth temperature detecting device 51, and the fifth temperature detecting device 52 is constituted by, for example, a thermistor or the like.

[0019] The air conditioning apparatus 100 has a control device 30. The control device 30 is composed of a microcomputer equipped with a CPU, ROM, and RAM. The control device 30 is configured to control the entire air conditioning apparatus 100, including the refrigerant circuit, based on the detected values ​​of each detection device and instructions from a remote control. For example, the control device 30 controls the rotation speed of the compressor 10, the rotation speed of the outdoor blower, switching of the refrigerant flow switching device 11, the opening degree of the throttling device 41, etc. Through these controls, the control device 30 switches between and executes each operating mode described below. The control device 30 may be provided in both the outdoor unit 1 and the indoor unit 2, or in either the outdoor unit 1 or the indoor unit 2.

[0020] [Cooling Operation Mode] Next, the cooling operation mode will be described using as an example a case where a cooling load is generated in the load-side heat exchanger 40. Fig. 2 is a refrigerant circuit diagram showing the flow of refrigerant in the cooling operation mode in the air conditioning apparatus according to this embodiment.

[0021] As shown in FIG. 2 , in the cooling operation mode, low-temperature, low-pressure refrigerant is compressed by the compressor 10 and discharged as high-temperature, high-pressure gas refrigerant. The high-temperature, high-pressure gas refrigerant discharged from the compressor 10 flows into the heat source-side heat exchanger 12 via the refrigerant flow switching device 11. The high-temperature, high-pressure gas refrigerant that flows into the heat source-side heat exchanger 12 condenses while releasing heat to the outdoor air, becoming high-pressure liquid refrigerant. The high-pressure liquid refrigerant that flows out of the heat source-side heat exchanger 12 flows out of the outdoor unit 1, passes through the main refrigerant pipe 3, and flows into the indoor unit 2. The high-pressure liquid refrigerant that flows into the indoor unit 2 is decompressed by the expansion device 41 and becomes low-temperature, low-pressure two-phase refrigerant. This two-phase refrigerant flows into the load-side heat exchanger 40, which functions as an evaporator, and absorbs heat from the indoor air to cool the indoor air, becoming low-temperature, low-pressure gas refrigerant. The low-temperature, low-pressure gas refrigerant flowing out of the load-side heat exchanger 40 passes through the main refrigerant pipe 3 and flows into the outdoor unit 1. The refrigerant that has flowed into the outdoor unit 1 passes through the refrigerant flow switching device 11 and the accumulator 13, and is then drawn into the compressor 10.

[0022] [Heating Operation Mode] Next, the heating operation mode will be described using as an example a case where a heating load is generated in the load-side heat exchanger 40. Fig. 3 is a refrigerant circuit diagram showing the flow of refrigerant in the heating operation mode in the air conditioning apparatus according to this embodiment.

[0023] As shown in Figure 3, in the heating operation mode, low-temperature, low-pressure refrigerant is compressed by the compressor 10 and discharged as high-temperature, high-pressure gas refrigerant. The high-temperature, high-pressure gas refrigerant discharged from the compressor 10 passes through the refrigerant flow switching device 11 and the main refrigerant pipe 3 and flows into the indoor unit 2. The high-temperature, high-pressure gas refrigerant that has flowed into the indoor unit 2 dissipates heat to the indoor air in the load-side heat exchanger 40, becomes high-pressure liquid refrigerant, and flows into the expansion device 41. After being decompressed to low-temperature, low-pressure two-phase refrigerant by the expansion device 41, it flows out of the indoor unit 2, passes through the main refrigerant pipe 3, and flows into the outdoor unit 1. The low-temperature, low-pressure two-phase refrigerant that has flowed into the outdoor unit 1 absorbs heat from the outdoor air in the heat-source-side heat exchanger 12, becoming low-temperature, low-pressure two-phase refrigerant. The low-temperature, low-pressure two-phase refrigerant leaving the heat source side heat exchanger 12 passes through the refrigerant flow switching device 11 and the accumulator 13, where it is separated into gas and liquid phases, and only the gas phase is drawn into the compressor 10.

[0024] [Defrosting Operation Mode] In the defrosting operation mode, the refrigerant flows in the same manner as in the cooling operation mode shown in FIG. 2. Low-temperature, low-pressure refrigerant is compressed by the compressor 10 and discharged as high-temperature, high-pressure gas refrigerant. The refrigerant flows into the heat source-side heat exchanger 12 via the refrigerant flow switching device 11. The high-temperature, high-pressure gas refrigerant that flows into the heat source-side heat exchanger 12 condenses while radiating heat to the outdoor air, becoming high-pressure liquid refrigerant. At this time, if frost has formed on the heat source-side heat exchanger 12, the frost melts due to the heat radiation. The high-pressure liquid refrigerant that flows out of the heat source-side heat exchanger 12 then flows out of the outdoor unit 1, passes through the main refrigerant pipe 3, and flows into the indoor unit 2. The high-pressure liquid refrigerant that flows into the indoor unit 2 is decompressed by the throttle device 41 and becomes a low-temperature, low-pressure two-phase refrigerant. This two-phase refrigerant flows into the load-side heat exchanger 40, which functions as an evaporator, and absorbs heat from the indoor air to cool it, becoming a low-temperature, low-pressure gas refrigerant. The low-temperature, low-pressure gas refrigerant flowing out of the load-side heat exchanger 40 passes through the main refrigerant pipe 3 and flows into the outdoor unit 1. The refrigerant that has flowed into the outdoor unit 1 passes through the refrigerant flow switching device 11 and the accumulator 13, and is then drawn into the compressor 10.

[0025] To perform defrosting efficiently, it is necessary to provide the heat source side heat exchanger 12 with an appropriate amount of heat relative to the amount of frost adhering to the heat source side heat exchanger 12. Furthermore, since the heat source for melting the frost is the energy contained in the compressed refrigerant discharged from the compressor 10, it is effective to maintain the compressor 10 in an operating state with a high circulation rate.

[0026] Whether or not to start defrosting operation is determined by determining whether frost has formed on the heat source-side heat exchanger 12 during heating operation based on the detection values ​​of each detection device. When frost has formed on the heat source-side heat exchanger 12, the heat exchange area and overall heat transfer coefficient decrease. When the intake air temperature of the heat source-side heat exchanger 12 remains unchanged, the heat exchange area and overall heat transfer coefficient decrease, causing the detected pressure of the second pressure detection device 21 and the detected temperature of the sixth temperature detection device 53 to decrease. The sixth temperature detection device 53 detects the temperature of the refrigerant flowing into the heat source-side heat exchanger 12 during heating operation and the temperature of the refrigerant flowing out of the heat source-side heat exchanger 12 during defrosting operation. The decrease in these detected values ​​is proportional to the amount of frost formed on the heat source-side heat exchanger 12. Therefore, by setting a threshold value for the detected pressure of the second pressure detection device 21 or the detected temperature of the sixth temperature detection device 53, defrosting can be started at an appropriate timing.

[0027] In actual use of the air conditioning apparatus 100, the outdoor temperature and humidity are not constant, so the amount of frost formed on the heat source-side heat exchanger 12 fluctuates. For this reason, it is effective to provide multiple thresholds and implement control that can respond to defrosting operations according to the situation. The amount of frost formed on the heat source-side heat exchanger 12 decreases the shorter the heating operation time before the defrosting operation, the lower the relative humidity, and the higher the outdoor temperature. The amount of frost formed on the heat source-side heat exchanger 12 increases the longer the heating operation time before the defrosting operation, the higher the relative humidity, and the lower the outdoor temperature.

[0028] Here, the execution control of the heating operation and the defrosting operation will be described. As a basic flow, the heating operation and the defrosting operation are executed alternately and repeatedly. If a defrosting start condition is satisfied during the execution of the heating operation, the heating operation ends and the defrosting operation starts. If a defrosting end condition is satisfied during the execution of the defrosting operation, the defrosting operation ends and the heating operation starts. Figure 4 is a flowchart showing an example of the flow of the process of switching between the heating operation and the defrosting operation executed by the control device in the air conditioning apparatus according to this embodiment.

[0029] In step S1 of FIG. 4 , the heating operation is started. Next, in step S2, the control device 30 determines whether a defrost start condition is satisfied. The defrost start condition includes multiple sub-conditions. One of the sub-conditions is a pressure condition set based on the relationship between the detection value of the second pressure detection device 21 and a threshold value, or a temperature condition set based on the relationship between the detection value of the sixth temperature detection device 53 and a threshold value. The other sub-condition is a time condition that is satisfied when the continuous execution time of the heating operation exceeds a threshold time. The time condition is set to prevent the heating from becoming ineffective due to frequent execution of the defrost operation. In this embodiment, the defrost start condition is satisfied when all of the multiple sub-conditions are satisfied. That is, the control device 30 determines that the defrost start condition is satisfied when the detection value of the second pressure detection device 21 or the sixth temperature detection device 53 falls below the threshold value and the continuous execution time of the heating operation exceeds the threshold time. Steps S12 and S13 in FIG. 5 and steps S12, S13, and S13-2 in FIG. 6, which will be described later, correspond to the process of determining sub-conditions of the defrosting start condition.

[0030] 5 is a flowchart showing an example of the flow of a defrost start condition determination process executed by the control device in the air conditioner according to the present embodiment. The defrost start condition determination process is performed during heating operation.

[0031] In step S11 of Fig. 5, the control device 30 starts determining whether a defrosting start condition is met. Next, in step S12, the control device 30 determines whether the heating operation time is longer than a minute (min). Here, a minute is a preset threshold time for the heating operation time. This threshold time can be freely set. If the heating operation time is longer than a minute, the process proceeds to step S13. If the heating operation time is a minute or less, the process proceeds to step S15.

[0032] In step S13, the control device 30 determines whether the state in which the detected temperature T6 of the sixth temperature detection device 53 is lower than temperature b has been detected for n consecutive minutes. Temperature b is a preset threshold temperature. n minutes is a preset threshold time for the continuous detection time. Because the sixth temperature detection device 53 detects the temperature of the refrigerant flowing through the piping, the detected temperature may fluctuate. For this reason, rather than determining whether the detected temperature T6 is lower than temperature b, it is more desirable to determine whether this state has continued for n consecutive minutes. These threshold temperatures and threshold times can be set freely. If the state in which the detected temperature T6 of the sixth temperature detection device 53 is lower than temperature b has been detected for n consecutive minutes, the process proceeds to step S14; otherwise, the process proceeds to step S15.

[0033] In step S14, the control device 30 ends the heating operation and starts the defrosting operation. In step S15, the control device 30 continues the heating operation.

[0034] In order to detect the influence of outside air more accurately, the pressure detected by the second pressure detection device 21 may be added to the defrost start conditions. Figure 6 is a flowchart showing another example of the flow of the defrost start condition determination process executed by the control device in the air conditioning apparatus according to this embodiment. Step S13-2 has been added to the process flow shown in Figure 6. The rest of the process is the same as that shown in Figure 5.

[0035] In step S13-2, the control device 30 determines whether the detected pressure P2 of the second pressure detection device 21 has been detected as being lower than the pressure c for n consecutive minutes. The pressure c is a preset threshold pressure. Because pressure can be detected with better responsiveness than temperature, the defrosting operation can be started at a more appropriate timing by including the detected pressure P2 in the defrosting start conditions.

[0036] 4, if the defrost start condition is satisfied in step S2, the process proceeds to step S3. If the defrost start condition is not satisfied in step S2, the process returns to step S1 and the heating operation is continued. Thus, the heating operation is continued until the defrost start condition is satisfied.

[0037] In step S3, the control device 30 terminates the heating operation and initiates the defrosting operation. Next, in step S4, the control device 30 determines whether the defrosting termination condition is satisfied. The defrosting termination condition includes multiple sub-conditions. One of the sub-conditions is a pressure condition set based on the relationship between the detection value of the second pressure detection device 21 and a threshold value, or a refrigerant temperature condition set based on the relationship between the detection value of the sixth temperature detection device 53 and a threshold value. The other sub-condition is a time condition that is satisfied when the continuous execution time of the defrosting operation exceeds a threshold time. The time condition is set to prevent the heating from becoming ineffective due to the defrosting operation continuing for a long period of time. In this embodiment, the defrosting termination condition is satisfied when any one of the multiple sub-conditions is satisfied. That is, the control device 30 determines that the defrosting termination condition is satisfied when the detection value of the second pressure detection device 21 or the sixth temperature detection device 53 exceeds a threshold value, or when the continuous execution time of the defrosting operation exceeds a threshold time.

[0038] If the defrost termination conditions are met, the process proceeds to step S5, where the defrosting operation is terminated and the heating operation is started. If the defrosting termination conditions are not met, the process returns to step S3, where the defrosting operation is continued.

[0039] 7 is a flowchart showing the flow of the defrosting operation process according to a comparative example of this embodiment. In step S21 of FIG. 7, the defrosting operation is started.

[0040] In step S22, the control device 30 determines whether the defrosting operation time is shorter than d minutes. d minutes is a preset threshold time for the defrosting operation time. This threshold time can be freely set. If the defrosting operation time is shorter than d minutes, the process proceeds to step S23. If the defrosting operation time is d minutes or more, the process proceeds to step S24.

[0041] In step S23, the control device 30 determines whether the detected temperature T6 of the sixth temperature detecting device 53 has been detected as being higher than temperature e for x minutes consecutively. Temperature e is a preset threshold temperature. x minutes is a preset threshold time for continuous detection. During defrosting operation, high-temperature, high-pressure refrigerant flows through the heat-source-side heat exchanger 12, as in cooling operation. While the frost on the heat-source-side heat exchanger 12 is melting, a latent heat change occurs, so the detected temperature T6 of the sixth temperature detecting device 53 remains near 0°C. After the frost on the heat-source-side heat exchanger 12 melts, a sensible heat change occurs, so the detected temperature T6 of the sixth temperature detecting device 53 rises.

[0042] If the state in which the detected temperature T6 is higher than the temperature e has been detected for x minutes consecutively, the process proceeds to step S24, otherwise the process returns to step S22. In step S24, the control device 30 ends the defrosting operation.

[0043] 7, when the defrosting operation time exceeds the threshold, the defrosting operation ends without completely melting the frost on the heat source-side heat exchanger 12. If such a defrosting operation is repeated, frost continues to adhere to the heat source-side heat exchanger 12, which may prevent the heat source-side heat exchanger 12 from performing its intended function.

[0044] For this reason, in this embodiment, defrosting operation control is executed as shown in Fig. 8. Fig. 8 is a flowchart showing an example of the flow of defrosting operation processing executed by the control device in the air conditioning apparatus according to this embodiment. In this embodiment, a flag area is provided in the RAM of the control device 30. A flag F1 or a flag F2 can be set in the flag area. Each flag indicates which condition has been met to end the defrosting operation.

[0045] In step S31 of FIG. 8, the defrosting operation is started. In step S32, the control device 30 determines whether the defrosting operation time is shorter than d minutes. d minutes is a preset threshold time for the defrosting operation time. This threshold time can be freely set. If the defrosting operation time is shorter than d minutes, the process proceeds to step S33. If the defrosting operation time is d minutes or more, the process proceeds to step S35. A defrosting operation time of d minutes or more is an example of a sub-condition for the defrosting termination condition. In this embodiment, the process proceeds to step S35 if the defrosting operation time is equal to d minutes, but it may also proceed to step S33 if the defrosting operation time is equal to d minutes.

[0046] In step S33, the control device 30 determines whether the detected temperature T6 of the sixth temperature detection device 53 has been detected as being higher than temperature e for x minutes consecutively. Temperature e is a preset threshold temperature. x minutes is a preset threshold time for continuous detection. These threshold temperatures and threshold times can be freely set. During defrosting operation, high-temperature, high-pressure refrigerant flows through the heat-source-side heat exchanger 12, as in cooling operation. While the frost on the heat-source-side heat exchanger 12 is melting, a latent heat change occurs, so the detected temperature T6 of the sixth temperature detection device 53 remains near 0°C. After the frost on the heat-source-side heat exchanger 12 melts, a sensible heat change occurs, so the detected temperature T6 of the sixth temperature detection device 53 rises.

[0047] If the detected temperature T6 has been detected as being higher than the temperature e for x minutes consecutively, the process proceeds to step S34; otherwise, the process returns to step S32. In step S34, the control device 30 sets a flag F1 in the flag area of ​​the RAM. In step S35, the control device 30 sets a flag F2 in the flag area of ​​the RAM. In step S36, the control device 30 ends the defrosting operation.

[0048] After the defrosting operation is completed, the heating operation is started with flag F1 or flag F2 set. Flag F2 is set when the defrosting operation is completed because a time condition is satisfied. Flag F1 is set when the defrosting operation is completed because a condition other than the time condition is satisfied. By setting flag F1 or flag F2, a record is kept of the determination at which the defrosting operation was completed. This makes it possible to determine whether to perform additional control if the defrosting operation is not completed within the time due to an unexpected environmental load.

[0049] In the example shown in FIG. 8 , steps S32 and S33 each correspond to a process for determining a sub-condition of the defrost termination condition. Therefore, the number of sub-conditions of the defrost termination condition is two. Therefore, two flags F1 and F2 are provided. The same number of flags as the number of sub-conditions of the defrost termination condition may be provided. FIG. 9 is a flowchart showing a generalized flow of the defrost operation process in the air conditioning apparatus according to this embodiment. As shown in FIG. 9 , if the number of determination processes, i.e., the number of sub-conditions of the defrost termination condition, is n, n flags F1 to Fn may be provided. In the following description, for simplicity, an example in which two flags are provided is illustrated, but the same number of flags as the number of determination processes for whether or not to terminate the defrost operation may be provided.

[0050] Fig. 10 is a flowchart showing an example of the flow of the defrosting operation process executed after a flag is set in the air conditioning apparatus according to the present embodiment. In step S41 of Fig. 10, the defrosting operation is started. In step S42, the control device 30 determines the type of flag. The flag was set during the previous defrosting operation. If flag F1 is set, the process proceeds to step S43, and if flag F2 is set, the process proceeds to step S46.

[0051] In step S43, the control device 30 determines whether the defrosting operation time is shorter than d1 minutes. d1 minutes is a preset threshold time for the defrosting operation time. If the defrosting operation time is shorter than d1 minutes, the process proceeds to step S44. If the defrosting operation time is d1 minutes or longer, the process proceeds to step S48.

[0052] In step S44, the control device 30 determines whether the state in which the detected temperature T6 of the sixth temperature detection device 53 is higher than the temperature e1 has been detected for x1 minutes consecutively. The temperature e1 is a preset threshold temperature. The x1 minute is a preset threshold time for the continuous detection time. If the state in which the detected temperature T6 is higher than the temperature e1 has been detected for x1 minutes consecutively, the process proceeds to step S45; otherwise, the process returns to step S43.

[0053] In step S46, the control device 30 determines whether the defrosting operation time is shorter than d2 minutes. d2 minutes is a preset threshold time for the defrosting operation time. d2 minutes is set to a time longer than d1 minutes. As a result, when flag F2 is set, the defrosting operation time is ensured to be longer than when flag F1 is set. If the defrosting operation time is shorter than d2 minutes, the process proceeds to step S47. If the defrosting operation time is d2 minutes or more, the process proceeds to step S48.

[0054] In step S47, the control device 30 determines whether the state in which the detected temperature T6 of the sixth temperature detection device 53 is higher than the temperature e2 has been detected for x2 consecutive minutes. The temperature e2 is a preset threshold temperature. For example, the temperature e2 is set to the same temperature as the temperature e1. The x2 minutes is a preset threshold time for the continuous detection time. For example, the x2 minutes is set to the same time as the x1 minute. If the state in which the detected temperature T6 is higher than the temperature e2 has been detected for x2 consecutive minutes, the process proceeds to step S45; otherwise, the process returns to step S46.

[0055] In step S45, the control device 30 sets a flag F1 in the flag area of ​​the RAM. In step S48, the control device 30 sets a flag F2 in the flag area of ​​the RAM. In step S49, the control device 30 ends the defrosting operation. Thereafter, the heating operation is started.

[0056] In this embodiment, the flag set at the end of the previous defrosting operation is read at the start of the defrosting operation, and the defrosting end conditions for the current defrosting operation are adjusted based on this flag. In this embodiment, the threshold time d2 minutes for the defrosting operation time when flag F2 is set is set to a time longer than the threshold time d1 minutes for the defrosting operation time when flag F1 is set. When flag F2 is set, the previous defrosting operation ended due to timeout, so there is a possibility that frost remains unmelted in the heat source side heat exchanger 12. In this embodiment, when flag F2 is set, a longer defrosting operation time is ensured, making it possible to more reliably reduce the amount of unmelted frost.

[0057] In this embodiment, the threshold value for the defrosting operation time is adjusted based on the flag, but the threshold temperatures e1 and e2 for the detection temperature T6 may also be adjusted, or the continuous detection times x1 and x2 may also be adjusted. For example, when flag F2 is set, the threshold temperature e2 for the detection temperature T6 is set to a temperature higher than the threshold temperature e2 for the detection temperature T6 when flag F1 is set. Furthermore, for example, when flag F2 is set, the continuous detection time x2 is set to a time longer than the continuous detection time x1 when flag F1 is set. In this way, the defrosting termination conditions when flag F2 is set are set to stricter conditions than the defrosting termination conditions when flag F1 is set. This allows the defrosting operation time when flag F2 is set to be longer than when flag F1 is set.

[0058] The flag should be checked each time a defrosting operation is completed. In other words, by setting an appropriate flag for the environmental load each time, the control can be adapted to transient conditions. After adapting to the transient conditions, the control can return to the control suitable for the normal environment.

[0059] In the control flow shown in Fig. 10, a determination process similar to step S13-2 in Fig. 6 may be added. That is, a defrosting end condition may be added in which the detected pressure P2 of the second pressure detection device 21 is continuously detected as being lower than the pressure c for n minutes.

[0060] As described above, the air conditioning apparatus 100 according to this embodiment includes a refrigerant circuit having a compressor 10, a refrigerant flow switching device 11, a heat source-side heat exchanger 12, a throttling device 41, and a load-side heat exchanger 40, and a control device 30 that controls the refrigerant circuit. The control device 30 is capable of switching between a heating operation in which the heat source-side heat exchanger 12 functions as an evaporator and a defrost operation in which the heat source-side heat exchanger 12 functions as a condenser. The control device 30 is configured to start a defrost operation when a defrost start condition is satisfied during the heating operation, and to terminate the defrost operation when a defrost termination condition is satisfied during the defrost operation. The defrost termination condition includes a first time condition that is satisfied when the execution time of the defrost operation exceeds a first threshold time. At least one of the defrost start condition and the defrost termination condition for the next defrost operation differs between a case in which the defrost operation is terminated because the first time condition is satisfied and a case in which the defrost operation is terminated because a defrost termination condition other than the first time condition is satisfied.

[0061] When the defrosting operation is terminated because the first time condition is satisfied, there is a higher possibility that frost remains unmelted on the heat source-side heat exchanger 12 compared to when the defrosting operation is terminated because a defrosting termination condition other than the first time condition is satisfied. According to the above configuration, when the defrosting operation is terminated because the first time condition is satisfied, the execution time of the heating operation or the execution time of the next defrosting operation can be adjusted so as to reduce the amount of unmelted frost on the heat source-side heat exchanger 12. This makes it possible to appropriately set the time ratio between the heating operation and the defrosting operation. Therefore, the amount of unmelted frost on the heat source-side heat exchanger 12 can be reduced, and a decrease in performance of the heat source-side heat exchanger 12 can be suppressed.

[0062] In the air conditioning device 100 of this embodiment, when the defrosting operation is terminated because the first time condition is satisfied, the first threshold time d2 for the next defrosting operation is set to a longer time than when the defrosting operation is terminated because a defrosting termination condition other than the first time condition is satisfied.

[0063] According to this configuration, when the defrosting operation is terminated because the first time condition is satisfied, the execution time of the next defrosting operation can be extended.

[0064] In the air conditioning apparatus 100 according to this embodiment, the defrost termination conditions include a first refrigerant temperature condition that is satisfied when the temperature of the refrigerant flowing out of the heat source-side heat exchanger 12 during defrost operation exceeds a first threshold temperature. When the defrost operation is terminated because the first time condition is satisfied, the first threshold temperature e2 for the next defrost operation is set to a higher temperature than when the defrost operation is terminated because a defrost termination condition other than the first time condition is satisfied.

[0065] According to this configuration, when the defrosting operation is terminated because the first time condition is satisfied, the execution time of the next defrosting operation can be extended.

[0066] In the air conditioning apparatus 100 according to this embodiment, the defrost termination conditions include a pressure condition that is satisfied when the pressure of the refrigerant drawn into the compressor 10 exceeds a threshold pressure. When the defrost operation is terminated because the first time condition is satisfied, the threshold pressure c for the next defrost operation is set to a higher pressure than when the defrost operation is terminated because a defrost termination condition other than the first time condition is satisfied.

[0067] According to this configuration, when the defrosting operation is terminated because the first time condition is satisfied, the execution time of the next defrosting operation can be extended.

[0068] Embodiment 2. An air conditioning apparatus according to embodiment 2 will be described. Fig. 11 is a flowchart showing an example of the flow of heating operation processing executed after a flag is set in an air conditioning apparatus according to this embodiment. In embodiment 1, the defrost end condition for the next defrost operation is adjusted based on the flag set at the end of the defrost operation, whereas in this embodiment, the defrost start condition for the next defrost operation is adjusted based on the flag set at the end of the defrost operation. The defrost start condition is determined while the heating operation is being performed.

[0069] In step S51 of Fig. 11, the heating operation is started. In step S52, the control device 30 determines the type of flag. The flag was set during the previous defrosting operation. If flag F1 is set, the process proceeds to step S53, and if flag F2 is set, the process proceeds to step S56.

[0070] In step S53, the control device 30 determines whether the heating operation time is shorter than a1 minute. a1 minute is a preset threshold time for the heating operation time. If the heating operation time is shorter than a1 minute, the process proceeds to step S54. If the heating operation time is equal to or longer than a1 minute, the process proceeds to step S55.

[0071] In step S54, the control device 30 determines whether the state in which the detected temperature T6 of the sixth temperature detection device 53 is lower than the temperature b1 has been detected for n1 consecutive minutes. The temperature b1 is a preset threshold temperature. The n1 minutes is a preset threshold time for the continuous detection time. If the state in which the detected temperature T6 is lower than the temperature b1 has been detected for n1 consecutive minutes, the process proceeds to step S58; otherwise, the process proceeds to step S55.

[0072] In step S56, the control device 30 determines whether the heating operation time is shorter than a2 minutes. a2 minutes is a preset threshold time for the heating operation time. a2 minutes is set to a time shorter than a1 minutes. If the heating operation time is shorter than a2 minutes, the process proceeds to step S57. If the heating operation time is a2 minutes or more, the process proceeds to step S55.

[0073] In step S57, the control device 30 determines whether the state in which the detected temperature T6 of the sixth temperature detection device 53 is lower than the temperature b2 has been detected for n2 consecutive minutes. The temperature b2 is a preset threshold temperature. For example, the temperature b2 is set to the same temperature as the temperature b1. The n2 minutes is a preset threshold time for the continuous detection time. For example, the n2 minutes is set to the same time as the n1 minutes. If the state in which the detected temperature T6 is lower than the temperature b2 has been detected for n2 consecutive minutes, the process proceeds to step S58; otherwise, the process proceeds to step S55.

[0074] In step S55, the heating operation continues. In step S58, the heating operation ends and the defrosting operation starts.

[0075] In this embodiment, the flag set at the end of the previous defrosting operation is read during heating operation, and the defrosting start conditions for the next defrosting operation are adjusted based on this flag. In this embodiment, the threshold time a2 minutes for the heating operation time when flag F2 is set is set to a time shorter than the threshold time a1 minutes for the heating operation time when flag F1 is set. When flag F2 is set, the previous defrosting operation ended due to timeout, so there is a possibility that frost remains melted on the heat source-side heat exchanger 12. In this embodiment, when flag F2 is set, the heating operation time is set to a short time, so the amount of frost that newly adheres to the heat source-side heat exchanger 12 can be reduced.

[0076] In this embodiment, the threshold value for the heating operation time is adjusted based on the flag, but the threshold temperatures b1 and b2 for the detection temperature T6 may also be adjusted, or the continuous detection times n1 and n2 may also be adjusted. For example, when flag F2 is set, the threshold temperature b2 for the detection temperature T6 is set to a temperature higher than the threshold temperature b2 for the detection temperature T6 when flag F1 is set. Furthermore, for example, when flag F2 is set, the continuous detection time n2 is set to a time shorter than the continuous detection time n1 when flag F1 is set. In this way, the defrost start conditions when flag F2 is set are set to conditions that are more lenient than the defrost start conditions when flag F1 is set. This allows the heating operation time when flag F2 is set to be shorter than when flag F1 is set.

[0077] As described above, in the air conditioning apparatus 100 according to this embodiment, the defrost start conditions include the second time condition that is satisfied when the execution time of the heating operation exceeds the second threshold time. When the defrost operation is terminated because the first time condition is satisfied, the second threshold time a2 for the next defrost operation is set to a shorter time than when the defrost operation is terminated because a defrost termination condition other than the first time condition is satisfied.

[0078] When the defrosting operation is terminated because the first time condition is satisfied, the execution time of the next heating operation can be shortened.

[0079] Embodiment 3. An air conditioner according to embodiment 3 will now be described. FIG. 12 is a schematic circuit diagram illustrating an example of the circuit configuration of an air conditioner according to this embodiment. As shown in FIG. 12, this embodiment is provided with a seventh temperature detector 54 that detects the outside air temperature as the detected temperature T7. The seventh temperature detector 54 is provided, for example, in the air intake section of the heat source-side heat exchanger 12. As the outside air temperature decreases, the evaporation temperature decreases, which tends to reduce the density of the refrigerant intake and the defrosting capacity. Therefore, by adding an outside air temperature condition to the flag determination, the defrosting operation can be performed more appropriately, and the amount of unmelted frost on the heat source-side heat exchanger 12 can be reduced, thereby suppressing performance degradation of the heat source-side heat exchanger 12.

[0080] 13 is a flowchart showing an example of the flow of the defrosting operation process executed by the control device in the air conditioning apparatus according to the present embodiment. In step S61 in FIG. 13, the defrosting operation is started.

[0081] In step S62, the control device 30 determines whether the detected temperature T7 of the seventh temperature detecting device 54 is lower than the temperature z. The temperature z is a preset threshold temperature. If the detected temperature T7 is lower than the temperature z, the process proceeds to step S63. If the detected temperature T7 is equal to or higher than the temperature z, the process proceeds to step S64.

[0082] In step S63, the control device 30 sets flag F2. In step S64, the control device 30 sets flag F1. After the flag is set, for example, the defrosting operation process shown in Fig. 10 and the heating operation process shown in Fig. 11 are executed.

[0083] As described above, the air conditioning apparatus 100 according to this embodiment includes a refrigerant circuit having a compressor 10, a refrigerant flow switching device 11, a heat source-side heat exchanger 12, a throttling device 41, and a load-side heat exchanger 40, and a control device 30 that controls the refrigerant circuit. The control device 30 is capable of switching between a heating operation in which the heat source-side heat exchanger 12 functions as an evaporator and a defrost operation in which the heat source-side heat exchanger 12 functions as a condenser. The control device 30 is configured to start a defrost operation when a defrost start condition is satisfied during heating operation, and to end the defrost operation when a defrost end condition is satisfied during defrost operation. At least one of the defrost start condition and the defrost end condition for the next defrost operation differs between a case in which the outdoor air temperature during the defrost operation is below a threshold temperature z and a case in which the outdoor air temperature during the defrost operation is equal to or higher than the threshold temperature z.

[0084] The lower the outdoor temperature, the lower the defrosting capacity due to a decrease in the density of the suction refrigerant. According to the above configuration, when the outdoor temperature is low, the execution time of the heating operation or the execution time of the next defrosting operation can be adjusted to compensate for the decrease in defrosting capacity. This allows the time ratio between the heating operation and the defrosting operation to be appropriately set. Therefore, the amount of unmelted frost in the heat source-side heat exchanger 12 can be reduced, and the performance degradation of the heat source-side heat exchanger 12 can be suppressed.

[0085] Embodiment 4 An air conditioner according to embodiment 4 will now be described. Fig. 14 is a schematic circuit diagram showing part of the circuit configuration of an air conditioner according to this embodiment.

[0086] Generally, in order to increase the cooling capacity and heating capacity of the outdoor unit 1, it is necessary to increase the heat exchange area of ​​the heat source-side heat exchanger 12. However, from the viewpoints of the manufacturing process and refrigerant flow control, there is a limit to the heat exchange area of ​​a single heat source-side heat exchanger 12. For this reason, multiple heat source-side heat exchangers 12 are sometimes provided in parallel.

[0087] 14 , in this embodiment, a plurality of heat source-side heat exchangers 12 a, 12 b, and 12 c are provided as heat source-side heat exchangers. The heat source-side heat exchangers 12 a, 12 b, and 12 c are provided in parallel in the refrigerant flow. Sixth temperature detection devices 53 a, 53 b, and 53 c are provided corresponding to the heat source-side heat exchangers 12 a, 12 b, and 12 c, respectively.

[0088] The sixth temperature detecting device 53a detects the temperature of the refrigerant flowing into the heat source side heat exchanger 12a during heating operation, and detects the temperature of the refrigerant flowing out from the heat source side heat exchanger 12a during defrost operation. The sixth temperature detecting device 53b detects the temperature of the refrigerant flowing into the heat source side heat exchanger 12b during heating operation, and detects the temperature of the refrigerant flowing out from the heat source side heat exchanger 12b during defrost operation. The sixth temperature detecting device 53c detects the temperature of the refrigerant flowing into the heat source side heat exchanger 12c during heating operation, and detects the temperature of the refrigerant flowing out from the heat source side heat exchanger 12c during defrost operation. The refrigerant circuit other than the heat source side heat exchangers 12a, 12b, 12c and their surroundings is the same as the refrigerant circuit shown in FIG. 1 etc.

[0089] When multiple heat source-side heat exchangers 12a, 12b, and 12c are provided, it is assumed that the amount of frost formed on each of the heat source-side heat exchangers 12a, 12b, and 12c will be different. Therefore, in this case, it is desirable to set defrost start conditions and defrost end conditions for each of the heat source-side heat exchangers 12a, 12b, and 12c.

[0090] 15 is a flowchart showing an example of the flow of a defrost start condition determination process executed by the control device in the air conditioning apparatus according to the present embodiment. The defrost start condition determination process is performed during heating operation.

[0091] In step S71, a determination of the defrost start condition is started. In step S72, the control device 30 determines whether the heating operation time is longer than a minute. a minute is a preset threshold time for the heating operation time. If the heating operation time is longer than a minute, the process proceeds to step S73. If the heating operation time is a minute or less, the process proceeds to step S77.

[0092] In step S73, the control device 30 determines whether the state in which the detected temperature T6a of the sixth temperature detecting device 53a is lower than the temperature b has been detected for n consecutive minutes. The temperature b is a preset threshold temperature. The n minutes is a preset threshold time for the continuous detection time. If the state in which the detected temperature T6a of the sixth temperature detecting device 53a is lower than the temperature b has been detected for n consecutive minutes, the process proceeds to step S74; otherwise, the process proceeds to step S77.

[0093] In step S74, the control device 30 determines whether the state in which the detected temperature T6b of the sixth temperature detecting device 53b is lower than the temperature b has been detected for n consecutive minutes. If the state in which the detected temperature T6b of the sixth temperature detecting device 53b is lower than the temperature b has been detected for n consecutive minutes, the process proceeds to step S75; otherwise, the process proceeds to step S77.

[0094] In step S75, the control device 30 determines whether the state in which the detected temperature T6c of the sixth temperature detecting device 53c is lower than the temperature b has been detected for n consecutive minutes. If the state in which the detected temperature T6c of the sixth temperature detecting device 53c is lower than the temperature b has been detected for n consecutive minutes, the process proceeds to step S76; otherwise, the process proceeds to step S77.

[0095] In step S76, the control device 30 ends the heating operation and starts the defrosting operation. In step S77, the control device 30 continues the heating operation.

[0096] 16 is a flowchart showing another example of the flow of the defrost start condition determination process executed by the control device in the air conditioning apparatus according to the present embodiment. In step S81, the defrost start condition determination is started.

[0097] In step S82, the control device 30 determines whether the heating operation time is longer than a minute. a minute is a preset threshold time for the heating operation time. If the heating operation time is longer than a minute, the process proceeds to step S83. If the heating operation time is a minute or less, the process proceeds to step S87.

[0098] In step S83, the control device 30 determines whether the state in which the detected temperature T6a of the sixth temperature detecting device 53a is lower than the temperature b has been detected for n consecutive minutes. The temperature b is a preset threshold temperature. The n minutes is a preset threshold time for the continuous detection time. If the state in which the detected temperature T6a of the sixth temperature detecting device 53a is lower than the temperature b has been detected for n consecutive minutes, the process proceeds to step S86; otherwise, the process proceeds to step S84.

[0099] In step S84, the control device 30 determines whether the state in which the detected temperature T6b of the sixth temperature detecting device 53b is lower than the temperature b has been detected for n consecutive minutes. If the state in which the detected temperature T6b of the sixth temperature detecting device 53b is lower than the temperature b has been detected for n consecutive minutes, the process proceeds to step S86; otherwise, the process proceeds to step S85.

[0100] In step S85, the control device 30 determines whether the state in which the detected temperature T6c of the sixth temperature detecting device 53c is lower than the temperature b has been detected for n consecutive minutes. If the state in which the detected temperature T6c of the sixth temperature detecting device 53c is lower than the temperature b has been detected for n consecutive minutes, the process proceeds to step S86; otherwise, the process proceeds to step S87.

[0101] In step S86, the control device 30 ends the heating operation and starts the defrosting operation. In step S87, the control device 30 continues the heating operation.

[0102] In the control flow shown in Figure 15, the defrosting operation does not start unless the defrosting start conditions are satisfied in all of the heat source side heat exchangers 12a, 12b, and 12c. On the other hand, in the control flow shown in Figure 16, the defrosting operation starts when the defrosting start conditions are satisfied in any one of the heat source side heat exchangers 12a, 12b, and 12c. In this way, in this embodiment, the operating mode can be selected according to the situation.

[0103] As described above, in the air conditioning apparatus 100 according to this embodiment, the defrost start condition includes a second refrigerant temperature condition that is satisfied when the temperature T6 of the refrigerant flowing into the heat source-side heat exchanger 12 during heating operation falls below the second threshold temperature b. The heat source-side heat exchangers include multiple heat source-side heat exchangers 12a, 12b, and 12c. The defrost start condition is satisfied when the second refrigerant temperature condition is satisfied in all of the multiple heat source-side heat exchangers 12a, 12b, and 12c. This configuration allows for a longer heating operation time.

[0104] In the air conditioning apparatus 100 according to this embodiment, the defrost start condition includes a second refrigerant temperature condition that is satisfied when the temperature T6 of the refrigerant flowing into the heat source-side heat exchanger 12 during heating operation falls below a second threshold temperature b. The heat source-side heat exchangers include multiple heat source-side heat exchangers 12a, 12b, and 12c. The defrost start condition is satisfied when the second refrigerant temperature condition is satisfied in any one of the multiple heat source-side heat exchangers 12a, 12b, and 12c. This configuration more reliably suppresses performance degradation in each of the heat source-side heat exchangers 12a, 12b, and 12c.

[0105] 1 outdoor unit, 2 indoor unit, 3 refrigerant main pipe, 4 refrigerant piping, 10 compressor, 11 refrigerant flow switching device, 12, 12a, 12b, 12c heat source side heat exchanger, 13 accumulator, 20 first pressure detection device, 21 second pressure detection device, 22 first temperature detection device, 23 second temperature detection device, 30 control device, 40 load side heat exchanger, 41 throttle device, 50 third temperature detection device, 51 fourth temperature detection device, 52 fifth temperature detection device, 53, 53a, 53b, 53c sixth temperature detection device, 54 seventh temperature detection device, 100 air conditioning device.

Claims

1. An air conditioning apparatus comprising: a refrigerant circuit having a compressor, a refrigerant flow switching device, a heat source side heat exchanger, a throttling device, and a load side heat exchanger; and a control device for controlling the refrigerant circuit, wherein the control device is capable of switching between a heating operation in which the heat source side heat exchanger functions as an evaporator, and a defrost operation in which the heat source side heat exchanger functions as a condenser, and wherein the control device is configured to start the defrost operation if a defrost start condition is met during the heating operation, and to end the defrost operation if a defrost end condition is met during the defrost operation, and wherein the defrost end condition includes a first time condition that is met when the execution time of the defrost operation exceeds a first threshold time, and wherein at least one of the defrost start condition and the defrost end condition for the next defrost operation is different between a case in which the defrost operation is ended because the first time condition is met and a case in which the defrost operation is ended because a defrost end condition other than the first time condition is met.

2. An air conditioning apparatus as described in claim 1, wherein when the defrosting operation is terminated because the first time condition is satisfied, the first threshold time for the next defrosting operation is set to a longer time than when the defrosting operation is terminated because a defrosting termination condition other than the first time condition is satisfied.

3. The air conditioning apparatus of claim 1 or 2, wherein the defrost termination conditions include a first refrigerant temperature condition that is satisfied when the temperature of the refrigerant flowing out of the heat source side heat exchanger during the defrost operation exceeds a first threshold temperature, and when the defrost operation is terminated because the first time condition is satisfied, the first threshold temperature for the next defrost operation is set to a higher temperature than when the defrost operation is terminated because a defrost termination condition other than the first time condition is satisfied.

4. An air conditioning apparatus as described in any one of claims 1 to 3, wherein the defrost termination conditions include a pressure condition that is satisfied when the pressure of the refrigerant sucked into the compressor exceeds a threshold pressure, and when the defrosting operation is terminated because the first time condition is satisfied, the threshold pressure for the next defrosting operation is set to a higher pressure than when the defrosting operation is terminated because a defrosting termination condition other than the first time condition is satisfied.

5. An air conditioning apparatus as described in any one of claims 1 to 4, wherein the defrost start condition includes a second time condition that is satisfied when the execution time of the heating operation exceeds a second threshold time, and when the defrost operation is terminated because the first time condition is satisfied, the second threshold time for the next defrost operation is set to a shorter time than when the defrost operation is terminated because a defrost termination condition other than the first time condition is satisfied.

6. An air conditioning apparatus as described in any one of claims 1 to 5, wherein the defrost start condition includes a second refrigerant temperature condition that is satisfied when the temperature of the refrigerant flowing into the heat source side heat exchanger during the heating operation falls below a second threshold temperature, the heat source side heat exchanger has a plurality of heat source side heat exchangers, and the defrost start condition is satisfied when the second refrigerant temperature condition is satisfied in all of the plurality of heat source side heat exchangers.

7. An air conditioning apparatus as described in any one of claims 1 to 5, wherein the defrost start condition includes a second refrigerant temperature condition that is satisfied when the temperature of the refrigerant flowing into the heat source side heat exchanger during the heating operation falls below a second threshold temperature, the heat source side heat exchanger has a plurality of heat source side heat exchangers, and the defrost start condition is satisfied when the second refrigerant temperature condition is satisfied in any one of the plurality of heat source side heat exchangers.

8. An air conditioning apparatus comprising: a refrigerant circuit having a compressor, a refrigerant flow switching device, a heat source side heat exchanger, a throttling device, and a load side heat exchanger; and a control device for controlling the refrigerant circuit, wherein the control device is capable of switching between a heating operation in which the heat source side heat exchanger functions as an evaporator, and a defrost operation in which the heat source side heat exchanger functions as a condenser, and wherein the control device is configured to start the defrost operation when a defrost start condition is met during the heating operation, and to end the defrost operation when a defrost end condition is met during the defrost operation, and wherein at least one of the defrost start condition and the defrost end condition for the next defrost operation differs between a case in which the outside air temperature during the defrost operation is below a threshold temperature and a case in which the outside air temperature during the defrost operation is equal to or higher than the threshold temperature.

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