EP3505850A1

EP3505850A1 - Control device of air conditioner, method of controlling air conditioner, air conditioner, and control program

Info

Publication number: EP3505850A1
Application number: EP18211427.2A
Authority: EP
Inventors: Kunihiro HIGASHIURA; Hiroshi Kanbara; Kazumi Okamura; Michiaki Nakanishi
Original assignee: Mitsubishi Heavy Industries Thermal Systems Ltd
Current assignee: Mitsubishi Heavy Industries Thermal Systems Ltd
Priority date: 2017-12-28
Filing date: 2018-12-10
Publication date: 2019-07-03
Also published as: JP6980520B2; JP2019120417A; AU2018274982B2; AU2018274982A1

Abstract

A control device of an air conditioner configured to control with a high user's comfort without decreasing an interior temperature is provided. The control device of the air conditioner includes an outdoor air temperature acquiring unit (41) configured to acquire an outside air temperature of an outdoor unit (1A), an outside heat exchange temperature acquiring unit (42) configured to acquire an outside heat exchange temperature of the outdoor unit (1A), and an operation execution unit (43) configured to perform a plurality of operation modes. The operation execution unit (43) is able to perform a positive cycle defrost operation mode and a reverse cycle defrost operation mode. Moreover, the operation execution unit (43) performs the other defrost operation mode when an entry condition of the other defrost operation mode is satisfied within a prohibition time of one defrost operation mode of the positive cycle defrost operation mode and the reverse cycle defrost operation mode.

Description

[Technical Field]

The present invention relates to a control device of an air conditioner, a method of controlling an air conditioner, an air conditioner, and a control program.
Priority is claimed on Japanese Patent Application No. 2017-253221, filed December 28, 2017 , the content of which is incorporated herein by reference.

[Background Art]

An air conditioner includes a refrigerant circuit in which various devices including a compressor, an indoor heat exchanger, an expansion device, and an outdoor heat exchanger are connected to each other through a refrigerant pipe. At the time of a heating operation, warm air is sent to an interior by circulating a refrigerant so that a high temperature and high pressure refrigerant gas delivered by a compressor is sent to an indoor heat exchanger. At this time, because the refrigerant absorbs heat, a surface of an outdoor heat exchanger on an outside air side is cooled in some cases to a subzero temperature range, particularly in the winter. Frost is generated and collects on the surface of the outdoor heat exchanger cooled in this way. Thus, heat conduction of the outdoor heat exchanger is impeded and the efficiency of heat exchange decreases.
In order to remove this frost, two types of defrosting operations are known. That is to say, these defrost operations are a positive cycle defrost operation (which is also referred to as a "bypass cycle defrost operation (positive (bypass) cycle defrost operation);" hereinafter referred to as a "DfP") and a reverse cycle defrost operation (which is also referred to as a "reverse cycle defrost operation (reverse cycle defrost operation);" hereinafter referred to as a "DfR"). The DfP is a defrosting operation in which a heat exchanger defrosts by circulating a refrigerant via a bypass pipeline through which some of a refrigerant gas discharged from a compressor is directly sent to the outdoor heat exchanger at the time of a heating operation. On the other hand, the DfR is a defrosting operation in which a heat exchanger defrosts by circulating a refrigerant through a refrigerant circuit differently from the heating operation and sending all of the refrigerant gas discharged from a compressor to the outdoor heat exchanger. That is to say, the DfR is a defrosting operation in which refrigerant circulation that is substantially the same as a cooling operation is performed except that air is not sent to an indoor heat exchanger.
With regard to switching between the two defrosting operations described above, various methods are known in accordance with differences in the assumptions concerning use situations of an air conditioner. For example, techniques performed to sense an exterior environment or an amount of defrosting from a temperature and a humidity and switch between the above-described defrosting operations in accordance with the sensed information are known.

[Citation List]

[Patent Literature]

[Patent Literature 1]
Japanese Unexamined Patent Application, First Publication No. 2001-133088

[Summary of Invention]

[Technical Problem]

Incidentally, the DfP can perform defrosting while continuing a heating operation, but some heat of a refrigerant is consumed by the defrosting. Thus, the heating efficiency decreases. Furthermore, since the defrosting is performed while the heating operation is continued, much time is required until the defrosting is fully performed. On the other hand, although the heating efficiency becomes equal to zero at the time of the DfR, most heat of a refrigerant can be used for defrosting. Thus, rapid defrosting is possible. In this way, the heating efficiency (effect) decreases or becomes zero at the time of a defrost operation. Thus, there is concern of a decrease in interior temperature and a decrease in user comfort.
In the case of the air conditioner described in Patent Literature 1, a defrost operation continues for a long time in a certain outside environment and thus an interior temperature and user comfort are likely to decrease for a long time.
The present invention was made in view of the above-described problems and an objective of the present invention is to provide a control device of an air conditioner, a method of controlling an air conditioner, an air conditioner, and a control program which perform control with high user comfort without decreasing an interior temperature.

[Solution to Problem]

According to a first aspect of the present invention, a control device in an air conditioner includes: an outdoor air temperature acquiring unit configured to acquire an outside air temperature of an outdoor unit; an outside heat exchange temperature acquiring unit configured to acquire an outside heat exchange temperature which is a temperature of a heat exchanger in the outdoor unit; and an operation execution unit configured to perform a plurality of operation modes, wherein the operation execution unit is able to perform a positive cycle defrost operation mode for defrosting the outdoor unit while maintaining a heating operation and a reverse cycle defrost operation mode for stopping the heating operation and defrosting the outdoor unit, and wherein when an entry condition of the other defrost operation mode is satisfied within a prohibition time of one defrost operation mode of the positive cycle defrost operation mode and the reverse cycle defrost operation mode, the operation execution unit performs the other defrost operation mode.
According to a second aspect of the present invention, when an entry condition of the other defrost operation mode is satisfied within a prohibition time of one defrost operation mode and after a predetermined stable standby time has elapsed after an operation end of the one defrost operation mode, the operation execution unit may perform the other defrost operation mode.
According to a third aspect of the present invention, the operation execution unit may set the number of times the other defrost operation mode is performed within the prohibition time to one.
According to a fourth aspect of the present invention, the operation execution unit may perform the reverse cycle defrost operation mode when both of the positive cycle defrost entry condition and the reverse cycle defrost entry condition are satisfied.
According to a fifth aspect of the present invention, the operation execution unit may perform the positive cycle defrost operation mode when a temperature difference between the outside air temperature and the outside heat exchange temperature exceeds a predetermined positive cycle defrost threshold value as an entry condition of the positive cycle defrost operation mode.
According to a sixth aspect of the present invention, the operation execution unit may perform the reverse cycle defrost operation mode when a temperature difference between the outside air temperature and the outside heat exchange temperature exceeds a predetermined reverse cycle defrost threshold value as an entry condition of the reverse cycle defrost operation mode, and the reverse cycle defrost threshold value may be a value larger than the positive cycle defrost threshold value.
According to a seventh aspect of the present invention, an air conditioner includes: the control device in an air conditioner as described above; and the outdoor unit including a temperature sensor capable of detecting the outside air temperature and the outside heat exchange temperature.
According to an eighth aspect of the present invention, a method of controlling an air conditioner includes: a step of acquiring an outside air temperature of an outdoor unit; a step of acquiring an outside heat exchange temperature which is a temperature of a heat exchanger of the outdoor unit; and a step of performing a plurality of operation modes, wherein the step of performing the plurality of operation modes is able to perform a positive cycle defrost operation mode for defrosting the outdoor unit while maintaining a heating operation and a reverse cycle defrost operation mode for stopping the heating operation and defrosting the outdoor unit, and wherein when an entry condition of the other defrost operation mode is satisfied within a prohibition time of one defrost operation mode of the positive cycle defrost operation mode and the reverse cycle defrost operation mode, the step of performing the plurality of operation modes performs the other defrost operation mode.
According to a ninth aspect of the present invention, a control program causing a computer of an air conditioner to function as: an outdoor air temperature acquiring unit configured to acquire an outside air temperature of an outdoor unit; an outside heat exchange temperature acquiring unit configured to acquire an outside heat exchange temperature which is a temperature of a heat exchanger of the outdoor unit; and an operation execution unit configured to perform a plurality of operation modes, wherein the operation execution unit is able to perform a positive cycle defrost operation mode for defrosting the outdoor unit while maintaining a heating operation and a reverse cycle defrost operation mode for stopping the heating operation and defrosting the outdoor unit, and wherein when an entry condition of the other defrost operation mode is satisfied within a prohibition time of one defrost operation mode of the positive cycle defrost operation mode and the reverse cycle defrost operation mode, the operation execution unit performs the other defrost operation mode.

[Advantageous Effects of Invention]

According to the control device in an air conditioner, the method of controlling an air conditioner, the air conditioner, and the control program described above, it is possible to perform control with high user comfort without decreasing an interior temperature.

[Brief Description of Drawings]

Fig. 1 is a diagram showing an overall constitution of an air conditioner according to a first embodiment.
Fig. 2 is a diagram showing a functional constitution of a control device in an air conditioner according to the first embodiment.
Fig. 3 is a diagram for describing a processing flow of the control device in the air conditioner according to the first embodiment.
Fig. 4 is a diagram for explaining control performed by the control device in the air conditioner according to the first embodiment.
Fig. 5 is a flowchart for describing control performed by a control device of an air conditioner according to a second embodiment.
Fig. 6 is a flowchart for describing control performed by a control device in an air conditioner according to a third embodiment.

[Description of Embodiments]

[First embodiment]

A control device in an air conditioner according to a first embodiment will be described in detail below with reference to the drawings.

(Overall constitution of air conditioner)

Fig. 1 is a diagram showing an overall constitution of an air conditioner according to the first embodiment.
A constitution of an air conditioner 1 according to the first embodiment will be described with reference to Fig. 1.
The air conditioner 1 according to the first embodiment includes a refrigerant circuit 10. The refrigerant circuit 10 includes a compressor 2, an indoor heat exchanger 3, an expansion valve 4, an outdoor heat exchanger 5, a two-way valve 6, and a four-way valve 7. The compressor 2, the indoor heat exchanger 3, the expansion valve 4, the outdoor heat exchanger 5, the two-way valve 6, and the four-way valve 7 are connected to a refrigerant pipe 20 through which a refrigerant can circulate.
The refrigerant circuit 10 includes a main circuit 100 used at the time of a heating operation, at the time of a positive cycle defrost operation, and at the time of a reverse cycle defrost operation and a bypass pipe 200 used only at the time of a positive cycle defrost operation.
When the four-way valve 7 is used as a starting point, the main circuit 100 includes a heat exchanger side main circuit 110 connected to a first terminal 7A and a second terminal 7B among terminals of the four-way valve 7 and a compressor side main circuit 120 connected to a third terminal 7C and a fourth terminal 7D among the terminals of the four-way valve 7. In other words, the heat exchanger side main circuit 110 and the compressor side main circuit 120 are connected to each other via the four-way valve 7.
The indoor heat exchanger 3, the expansion valve 4, and the outdoor heat exchanger 5 are provided in the heat exchanger side main circuit 110. The compressor 2 is provided in the compressor side main circuit 120.
In the four-way valve 7, it is possible to connect two pairs of pipelines obtained by paring two respective pipelines among four pipelines connected to the terminals and it is possible to switch between the two pairs of pipelines. To be specific, in the four-way valve 7, it is possible to connect a pair of the first terminal 7A and the fourth terminal 7D and a pair of the second terminal 7B and the third terminal 7C. Furthermore, in the four-way valve 7, it is possible to connect a pair of the first terminal 7A and the third terminal 7C and a pair of the second terminal 7B and the fourth terminal 7D.
Thus, it is possible to switch a connection relationship between the heat exchanger side main circuit 110 and the compressor side main circuit 120. When the refrigerant pipe 20 through which a refrigerant which has been discharged from the compressor 2 passes is connected to the third terminal 7C of the four-way valve 7, the high temperature and high pressure refrigerant discharged from the compressor 2 flows through any one of two types of paths, i.e., a path (cooling path) from the second terminal 7B toward the outdoor heat exchanger 5 and a path (heating path) from the first terminal 7A toward the indoor heat exchanger 3.
As described above, the refrigerant circuit 10 in the air conditioner 1 in the first embodiment further includes the bypass pipe 200. The bypass pipe 200 is a refrigerant pipe configured to connect (a bypass start point 20A between) the compressor 2 and the four-way valve 7, in the compressor side main circuit 120 on a discharge side of the compressor 2, to a bypass end point 20B provided in the heat exchanger side main circuit 110 between an expansion device 4 and the outdoor heat exchanger 5. The two-way valve 6 is provided in the bypass pipe 200 and thus it is possible to open and close the bypass pipe 200. It should be noted that the two-way valve 6 is closed at the time of a normal heating operation, at the time of a cooling operation, and at the time of a reverse cycle defrost operation.
The circulation of a refrigerant at the time of a heating operation will be described. At the time of a heating operation, the four-way valve 7 is in a connection relationship of a heating path. A refrigerant is compressed by the compressor 2 to have a high temperature and a high pressure and then enters from the third terminal 7C of the four-way valve 7 and goes from the first terminal 7A to the indoor heat exchanger 3. In the indoor heat exchanger 3, a refrigerant is cooled and condensed by performing heat exchange, and instead, heat is transferred to indoor air outside the indoor heat exchanger 3. The indoor air is sent through an indoor side sending machine 13. The condensed refrigerant flows into the expansion valve 4 to have a low temperature and a low pressure. The refrigerant flowing outside of the expansion valve 4 flows into the outdoor heat exchanger 5, is heated by outdoor air, and evaporates and vaporizes in the outdoor heat exchanger 5. The vaporized refrigerant is returned to the compressor 2 through the second terminal 7B and the fourth terminal 7D of the four-way valve 7. By continuously repeating the above-described cycle, the air conditioner 1 performs the heating operation.
At the time of a heating operation, heat of air outside the outdoor heat exchanger 5 is taken away by a refrigerant and the air has a lower temperature as described above. Thus, a temperature of a surface of the indoor heat exchanger 3 decreases to a subzero temperature range and frost is generated and collects in some cases. Thus, there are concerns of the hindrance of heat conduction of a heat exchanger and a decrease in efficiency of heat exchange.
In order to remove this frost, two types of defrosting operations (defrost operations) are known. That is to say, there are a positive cycle defrost operation (bypass cycle defrost operation; hereinafter referred to as a "DfP") and a reverse cycle defrost operation (reverse cycle defrost operation; hereinafter referred to as a "DfR").
The DfP is a defrosting operation of performing defrosting of the outdoor heat exchanger 5 by circulating a refrigerant via the bypass pipe 200 through which a part of a refrigerant gas discharged from the compressor 2 at the time of a heating operation is sent to the outdoor heat exchanger 5. The DfP is performed by opening the two-way valve 6.
Circulation of a refrigerant at the time of the DfP will be described. At the time of the DfP, a connection relationship of a heating path in the four-way valve 7 is maintained and thus the circulation of the refrigerant at the time of the heating operation is maintained. In addition to this, the two-way valve 6 is opened and the refrigerant also flows to the bypass pipe 200 so that a part of the high temperature and high pressure refrigerant discharged from the compressor 2 is sent to the outdoor heat exchanger 5 without passing through the indoor heat exchanger 3. Thus, heat is transferred to the outdoor heat exchanger 5 and defrosting is performed.
It should be noted that, since the DfP includes sending a part of the high temperature and high pressure refrigerant to be originally sent to the indoor heat exchanger 3 to the outdoor heat exchanger 5, the DfP can continue the heating operation while performing defrosting, but the heating capacity thereof decreases to about one third as compared with a normal heating operation. Furthermore, since an amount of refrigerant sent to the outdoor heat exchanger 5 is a part of a total refrigerant, the defrosting capacity thereof decreases as compared with the DfR which will be described next.
On the other hand, the DfR is a defrosting operation of performing defrosting by circulating a refrigerant in the heat exchanger side main circuit 110 in a direction opposite to that of a heating operation. By performing the circulation in the direction opposite to that of the heating operation, all of the refrigerant gas discharged from the compressor 2 is sent to the outdoor heat exchanger 5. Thus, in the DfR, frost can be more significantly melted as compared with the DfP. However, since an operation is performed by switching the four-way valve 7 to a connection relationship of a cooling path in the DfR, refrigerant circulation that is substantially the same as the cooling operation is performed except that air is not blown to the indoor heat exchanger 3. For this reason, during the DfR, the heating operation stops, indoor heat is taken away, and an interior temperature decreases.
Circulation of a refrigerant at the time of the DfR will be described. The refrigerant is compressed by the compressor 2 to have a high temperature and a high pressure and then enters from the third terminal 7C of the four-way valve 7 and goes from the second terminal 7B to the outdoor heat exchanger 5. In the outdoor heat exchanger 5, the refrigerant is cooled and condensed by performing heat exchange, and instead, transfers heat to outdoor air outside the outdoor heat exchanger 5. For this reason, the condensed refrigerant flows into the expansion device 4 to have a low temperature and a low pressure. The refrigerant flowing outside of the expansion device 4 flows into the indoor heat exchanger 3, is heated by indoor air, and evaporates and vaporizes in the indoor heat exchanger 3. At this time, heat is taken away from the indoor air outside the indoor heat exchanger 3. In the case of a cooling operation, the low temperature indoor air is sent by the indoor side sending machine 13 and is used for indoor cooling, but air is not sent in the DfR. The vaporized refrigerant enters from the first terminal 7A of the four-way valve 7, flows outside of the fourth terminal 7D, and is returned to the compressor 2. The above-described cycle is continuously repeated.
Here, the air conditioner 1 in this embodiment further includes the outside air temperature sensor 25, a heat exchanger temperature sensor 35, and a control device 201 configured to switch among three operation modes, i.e., the above-described heating operation, DfP, and DfR.

(Functional constitution of control device in air conditioner)

Fig. 2 is a diagram showing a functional constitution of the control device in the air conditioner according to the first embodiment.
The control device in the air conditioner in the first embodiment will be described below with reference to Figs. 1 and 2.
As illustrated in Fig. 2, an outdoor unit 1A includes the control device 201. The control device 201 illustrated in Fig. 2 operates on the basis of a predetermined program to function as an outdoor air temperature acquiring unit 41, an outside heat exchange temperature acquiring unit 42, and an operation execution unit 43.
The outdoor air temperature acquiring unit 41 acquires the outside air temperature of the outdoor unit 1A through the outside air temperature sensor 25.
The outside heat exchange temperature acquiring unit 42 acquires a temperature of the outdoor heat exchanger 5 in the outdoor unit 1A (hereinafter also referred to as an "outside heat exchange temperature") through the heat exchanger temperature sensor 35.
The operation execution unit 43 switches an operation mode of the air conditioner 1 on the basis of a predetermined condition based on the outside air temperature and the outside heat exchange temperature. The operation execution unit 43 switches an operation mode by mainly controlling the two-way valve 6 and the four-way valve 7.

(Processing flow of control device in air conditioner)

Fig. 3 is a diagram for describing a processing flow of the control device in the air conditioner according to the first embodiment.
Fig. 4 is a diagram for explaining control performed by the control device in the air conditioner according to the first embodiment.
A processing flow performed by the control device 201 according to the first embodiment will be described below with reference to Figs. 3 and 4.
First, when a user starts using the heating, the control device 201 starts a heating operation (Step S1A). To be specific, the operation execution unit 43 controls the four-way valve 7 so that the refrigerant gas discharged from the compressor 2 circulates through a heating path (a path from the first terminal 7A toward the indoor heat exchanger 3) and closes the two-way valve 6.
In Step S 1 A, the operation execution unit 43 determines whether a predetermined DfP prohibition time t1 (for example, 35 minutes) has elapsed from the start of the heating operation (whether an elapsed time t of the heating operation exceeds the DfP prohibition time t1) (Step S2A).
When it is determined that the predetermined DfP prohibition time t1 has not elapsed from the start of the heating operation (Step S2A: NO), the operation execution unit 43 returns to the process of Step S1A so as to continue the heating operation ongoingly.
When it is determined that the predetermined DfP prohibition time t1 has elapsed from the start of the heating operation (Step S2A: YES), the operation execution unit 43 determines whether an outside air temperature ThA and an outside heat exchange temperature ThR satisfy a predetermined positive cycle defrost entry condition.
To be specific, the operation execution unit 43 determines whether a temperature difference between the outside air temperature ThA and the outside heat exchange temperature ThR (ThA-ThR) exceeds a positive cycle defrost threshold value Th1 (for example, 20 °C) (Step S3A).
When it is determined that the temperature difference (ThA-ThR) does not exceed the positive cycle defrost threshold value Th1 (Step S3A: NO), the operation execution unit 43 returns to the process of Step S1A so as to continue the heating operation ongoingly.
When it is determined that the temperature difference (ThA-ThR) exceeds the positive cycle defrost threshold value Th1 (Step S3A: YES), the operation execution unit 43 determines that the outdoor heat exchanger 5 is frosting and performs a positive cycle defrost operation mode (Step S4A). Here, the operation execution unit 43 opens the two-way valve 6 while maintaining a connection state of the four-way valve 7 (while maintaining that the refrigerant is circulating through the heating path). Thus, a part of the discharged refrigerant gas flows through the bypass pipe 200 and is sent to the outdoor heat exchanger 5, thereby performing defrosting.
Subsequently, the operation execution unit 43 determines whether the outdoor heat exchanger 5 has defrosted by performing the positive cycle defrost operation mode. To be specific, the operation execution unit 43 determines whether the temperature difference (ThA-ThR) is a predetermined defrost release threshold value ThC or less (Step S5A). Here, the defrost release threshold value ThC is set to a value smaller than the positive cycle defrost threshold value Th1.
When it is determined that the temperature difference (ThA-ThR) is not the predetermined defrost release threshold value ThC or less (Step S5A: NO), the operation execution unit 43 returns to the process of Step S4A on the basis of the determination that the outdoor heat exchanger 5 has not defrosted, and subsequently performs the positive cycle defrost operation mode.
On the other hand, when it is determined that the temperature difference (ThA-ThR) is the predetermined defrost release threshold value ThC or less (Step S5A: YES), the operation execution unit 43 ends the positive cycle defrost operation mode on the basis of the determination that the outdoor heat exchanger 5 has defrosted and starts the heating operation again (Step S6A).
Here, as will be described later, even when it is determined that the temperature difference (ThA-ThR) is the defrost release threshold value ThC or less, it is conceivable that the outdoor heat exchanger 5 has not necessarily completely defrosted. That is to say, it is also assumed that there is the melted residue of the frost in the outdoor heat exchanger 5 in accordance with an environmental condition or the like.
Subsequently, in Step S6A, the operation execution unit 43 determines whether a predetermined DfR prohibition time t2 (t2>t1; for example, 45 minutes) has elapsed from the start of the heating operation while performing the heating operation (Step S7A). When it is determined that the predetermined DfR prohibition time t2 has not elapsed from the start of the heating operation (Step S7A: NO), the operation execution unit 43 returns to the process of Step S6A so as to continue the heating operation ongoingly.
When it is determined that the predetermined DfR prohibition time t2 has elapsed from the start of the heating operation (Step S7A: YES), subsequently, the operation execution unit 43 determines whether a predetermined stable standby time (for example, 5 minutes) has elapsed from an operation end of the positive cycle defrost operation mode (Step S4A) (Step S8A).
When it is determined that the predetermined stable standby time has not elapsed from the operation end of the positive cycle defrost operation mode (Step S8A: NO), the process returns to the process of Step S6A on the basis of the determination that the outside heat exchange temperature ThR or the like is not stable after the heating operation starts again (Step S6A), and subsequently, continues the heating operation.
On the other hand, when it is determined that the predetermined stable standby time has elapsed from the operation end of the positive cycle defrost operation mode (Step S8A: YES), the operation execution unit 43 further determines whether the DfP prohibition time t1 has elapsed from the operation end of the positive cycle defrost operation mode (Step S9A).
When it is determined that the DfP prohibition time t1 has elapsed from the operation end of the positive cycle defrost operation mode (Step S9A: YES), the operation execution unit 43 can immediately perform the positive cycle defrost operation mode when the positive cycle defrost entry condition is satisfied in the subsequent process. Therefore, the process of the operation execution unit 43 returns to the process of Step S3A and performs the positive cycle defrost operation mode or continues the heating operation in accordance with the determination of whether the positive cycle defrost entry condition is satisfied.
On the other hand, when it is determined that the DfP prohibition time t1 has not elapsed from the operation end of the positive cycle defrost operation mode (Step S9A: NO), the operation execution unit 43 cannot perform the positive cycle defrost operation mode again until the DfP prohibition time t1 has elapsed.
Here, if it is assumed that defrosting through the positive cycle defrost operation which is initially performed (performed in Step S4A) is insufficient (there is the melted residue of the frost), it is assumed that, when the DfP prohibition time t1 has additionally elapsed from that time, the frost has significantly grown and it takes a lot of time to complete defrosting until defrosting has been completed through the positive cycle defrost operation to be performed again. Thus, the positive cycle defrost operation period (that is, a period during which heating capacity is not sufficient) lasts for a long time and thus the user's comfort is impaired.
Thus, while the DfP prohibition time t1 has not elapsed from the operation end of the positive cycle defrost operation mode, the operation execution unit 43 determines whether defrosting is sufficiently performed through the positive cycle defrost operation performed in Step S4A (whether there is not the melted residue of the frost). To be specific, the operation execution unit 43 determines whether the outside air temperature ThA and the outside heat exchange temperature ThR satisfy a predetermined reverse cycle defrost entry condition.
That is to say, the operation execution unit 43 determines whether the temperature difference (ThA-ThR) exceeds a reverse cycle defrost threshold value Th2 (Th1<Th2) (Step S10A).
When it is determined that the temperature difference (ThA-ThR) does not exceed the reverse cycle defrost threshold value Th2 (Th1<Th2) (Step S10A), the process of the operation execution unit 43 returns to the process of Step S6A on the basis of the determination that the defrosting has been sufficiently performed and continues the heating operation.
On the other hand, when it is determined that the temperature difference (ThA-ThR) does not exceed the reverse cycle defrost threshold value Th2 (Th1<Th2), it is conceivable that the defrosting is not sufficiently performed after the positive cycle defrost operation ends. Thus, it is conceivable that the temperature difference (ThA-ThR) is that the outside heat exchange temperature sharply decreased in a short time. Thus, the operation execution unit 43 immediately performs the reverse cycle defrost operation mode (Step S11A).
Here, the operation execution unit 43 switches the four-way valve 7 to a connection relationship of the cooling path and performs an operation.
Subsequently, the operation execution unit 43 determines whether the outdoor heat exchanger 5 has defrosted by performing the reverse cycle defrost operation mode. To be specific, the operation execution unit 43 determines whether the temperature difference (ThA-ThR) is the predetermined defrost release threshold value ThC (ThC>Th2) or less (Step S12A).
When it is determined that the temperature difference (ThA-ThR) is the predetermined defrost release threshold value ThC or less (Step S12A: NO), the process of the operation execution unit 43 returns to the process of Step S12A, and subsequently, performs the reverse cycle defrost operation mode.
On the other hand, when it is determined that the temperature difference (ThA-ThR) is the predetermined defrost release threshold value ThC or less (Step S12A: YES), the operation execution unit 43 ends the reverse cycle defrost operation mode on the basis of the determination that the outdoor heat exchanger 5 has defrosted and starts the heating operation again (Step S13A).
The operation execution unit 43 ends the reverse cycle defrost operation mode, resets the elapsed time at a timing at which the heating operation starts again (Step S14A), and returns to the process of Step S2A.

(Action and effect)

As described above, the operation execution unit 43 according to the first embodiment can perform both of the positive cycle defrost operation mode in which the defrosting of the outdoor unit 1A is performed while maintaining the heating operation and the reverse cycle defrost operation mode in which the heating operation stops and the defrosting of the outdoor unit 1A is performed. Moreover, the operation execution unit 43 performs the reverse cycle defrost operation mode when an entry condition (reverse cycle defrost entry condition) of the reverse cycle defrost operation mode is satisfied within the prohibition time of the positive cycle defrost operation mode.
Thus, even when the defrosting through the first positive cycle defrost operation is insufficient, an additional defrost operation (reverse cycle defrost operation) is performed on the basis of the fact that the reverse cycle defrost entry condition is satisfied within the prohibition time of the positive cycle defrost operation and the defrosting is completely performed. Therefore, even when the subsequent positive cycle defrost operation starts after the prohibition time has elapsed, the positive cycle defrost period (that is, a period in which heating capacity is low) is not continued for a long period of time (the defrosting is completed in a short time).
On the other hand, when the defrosting through the first positive cycle defrost operation is originally sufficient, no additional defrost operation (reverse cycle defrost operation) is performed within the prohibition time. Therefore, in this case, it is possible to provide the user with the heating operation at all times including the positive cycle defrost operation period.
Thus, it is possible to control with a high user's comfort without decreasing an indoor temperature.
Also, the operation execution unit 43 according to the first embodiment performs the reverse cycle defrost operation mode when the reverse cycle defrost entry condition is satisfied within the prohibition time of the positive cycle defrost operation mode, after the operation end of the positive cycle defrost operation mode, and after a predetermined stable standby time (for example, 5 minutes) has elapsed.
In this way, it is possible to determine whether to perform an additional reverse cycle defrost operation after stabilizing the fluctuation (overshoot) of the outside heat exchange temperature ThR after the end of the positive cycle defrost operation by providing the stable standby time after the end of the positive cycle defrost operation.

[Second embodiment]

A second embodiment will be described below with reference to Fig. 5. Constituent elements in the second embodiment that are the same as those of the first embodiment will be denoted by the same reference numerals and detailed description thereof will be omitted.
The second embodiment and the first embodiment differ in that all of the DfP prohibition time t1 and the DfR prohibition time t2, the DfP and the DfR, the positive cycle defrost threshold value Th1 and the reverse cycle defrost threshold value Th2 associated with a procedure to be performed and an operation mode are mutually replaced. That is to say, in the second embodiment, the execution condition determination of the DfP and the procedure of executing the DfP in the first embodiment is replaced with the execution condition determination of the DfR and the execution thereof and the execution condition determination of the DfR and the procedure of executing the DfR in the first embodiment is replaced with the execution condition determination of the DfP and the execution thereof.
In the control device 201 in the air conditioner and the air conditioner 1 including the control device 201 described above, the DfR is more preferentially performed than the DfP. For this reason, when an outside air temperature is relatively low in a case in which defrosting is required, control in which the longer duration of the heating effect is ensured can be eventually performed by performing a rapid defrosting.

[Third embodiment]

A third embodiment will be described below with reference to Fig. 6. Constituent elements in the third embodiment that are the same as those of the first embodiment will be denoted by the same reference numerals and detailed description thereof will be omitted.
The third embodiment and the first embodiment differ in that an operation execution unit 43 associated with the third embodiment has a means for determining whether an outside air temperature ThA is higher than a predetermined determination threshold value Th3.
Also, as a procedure, Step S1A to S14A and Step S1B to S14B are the same as those of the first and second embodiments are provided and Step S1C is provided as a step before Steps S1A and S1B. Step S1C is a procedure of determining whether the outside air temperature ThA satisfies a relationship of ThA>Th3 and the determination threshold value Th3 is a threshold value for determining whether the control of the first embodiment or the control of the second embodiment is to be performed. In addition, when the process passes through the process of Step S14A or Step S14B, the process returns to the process of Step S1C.
In the control device 201 of the air conditioner and the air conditioner 1 including the control device 201 described above, it is possible to automatically switch between the control which gives a priority to the DfP and the control which gives a priority to the DfR in accordance with a change in outside air temperature. Thus, for example, even when an outside air temperature significantly changes in a day, it is possible to appropriately perform an defrost operation according to an amount of required defrosting while securing a heating time.
Also, a control device 201 (operation execution unit 43) in an air conditioner associated with other embodiments may limit the number of times the other defrost operation mode is performed to one within a prohibition time of one of the positive cycle defrost operation mode and the reverse cycle defrost operation mode.
In this way, it is possible to prevent the user's comfort from being impaired instead due to the frequent execution of the other defrost operation within a prohibition time of one defrost operation.
While the first, second, and third embodiments of the present invention have been described in detail above with reference to the drawings, the specific constitution is not limited to the embodiments and design changes are also included without departing from the gist of the present invention.

[Industrial Applicability]

[Reference Signs List]

1 Air conditioner
1A Outdoor unit
201 Control device
2 Compressor
3 Indoor heat exchanger
4 Expansion valve
5 Outdoor heat exchanger
6 Two-way valve
7 Four-way valve
7A First terminal
7B Second terminal
7C Third terminal
7D Fourth terminal
10 Refrigerant circuit
20 Refrigerant pipe
20A Bypass start point
20B Bypass end point
200 Bypass pipe
100 Main circuit
110 Heat exchanger side main circuit
120 Compressor side main circuit
41 Outdoor air temperature acquiring unit
42 Outside heat exchange temperature acquiring unit
43 Operation execution unit

Claims

A control device in an air conditioner, comprising:
an outdoor air temperature acquiring unit configured to acquire an outside air temperature of an outdoor unit;

an outside heat exchange temperature acquiring unit configured to acquire an outside heat exchange temperature which is a temperature of a heat exchanger in the outdoor unit; and

an operation execution unit configured to perform a plurality of operation modes,
wherein the operation execution unit is able to perform a positive cycle defrost operation mode for defrosting the outdoor unit while maintaining a heating operation and a reverse cycle defrost operation mode for stopping the heating operation and defrosting the outdoor unit, and
wherein when an entry condition of the other defrost operation mode is satisfied within a prohibition time of one defrost operation mode of the positive cycle defrost operation mode and the reverse cycle defrost operation mode, the operation execution unit performs the other defrost operation mode.
The control device in an air conditioner according to claim 1, wherein, when an entry condition of the other defrost operation mode is satisfied within a prohibition time of one defrost operation mode and after a predetermined stable standby time has elapsed after an operation end of the one defrost operation mode, the operation execution unit performs the other defrost operation mode.
The control device in an air conditioner according to claim 2, wherein the operation execution unit sets the number of times the other defrost operation mode is performed within the prohibition time to one.
The control device in an air conditioner according to any one of claims 1 to 3, wherein the operation execution unit performs the reverse cycle defrost operation mode when both of the positive cycle defrost entry condition and the reverse cycle defrost entry condition are satisfied.
The control device in an air conditioner according to any one of claims 1 to 4, wherein the operation execution unit performs the positive cycle defrost operation mode when a temperature difference between the outside air temperature and the outside heat exchange temperature exceeds a predetermined positive cycle defrost threshold value as an entry condition of the positive cycle defrost operation mode.
The control device in an air conditioner according to claim 5, wherein the operation execution unit performs the reverse cycle defrost operation mode when a temperature difference between the outside air temperature and the outside heat exchange temperature exceeds a predetermined reverse cycle defrost threshold value as an entry condition of the reverse cycle defrost operation mode, and
the reverse cycle defrost threshold value is a value larger than the positive cycle defrost threshold value.
An air conditioner comprising:
the control device in an air conditioner according to any one of claims 1 to 6; and

the outdoor unit including a temperature sensor capable of detecting the outside air temperature and the outside heat exchange temperature.
A method of controlling an air conditioner, comprising:
a step of acquiring an outside air temperature of an outdoor unit;

a step of acquiring an outside heat exchange temperature which is a temperature of a heat exchanger of the outdoor unit; and

a step of performing a plurality of operation modes,
wherein the step of performing the plurality of operation modes is able to perform a positive cycle defrost operation mode for defrosting the outdoor unit while maintaining a heating operation and a reverse cycle defrost operation mode for stopping the heating operation and defrosting the outdoor unit, and
wherein when an entry condition of the other defrost operation mode is satisfied within a prohibition time of one defrost operation mode of the positive cycle defrost operation mode and the reverse cycle defrost operation mode, the step of performing the plurality of operation modes performs the other defrost operation mode.
A control program causing a computer of an air conditioner to function as:
an outdoor air temperature acquiring unit configured to acquire an outside air temperature of an outdoor unit;

an outside heat exchange temperature acquiring unit configured to acquire an outside heat exchange temperature which is a temperature of a heat exchanger of the outdoor unit; and

an operation execution unit configured to perform a plurality of operation modes,
wherein the operation execution unit is able to perform a positive cycle defrost operation mode for defrosting the outdoor unit while maintaining a heating operation and a reverse cycle defrost operation mode for stopping the heating operation and defrosting the outdoor unit, and
wherein when an entry condition of the other defrost operation mode is satisfied within a prohibition time of one defrost operation mode of the positive cycle defrost operation mode and the reverse cycle defrost operation mode, the operation execution unit performs the other defrost operation mode.