JP2018128158A - Air conditioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten the time for a room temperature to reach a vicinity of a set heating temperature when returning to a heating operation after defrosting in an air conditioner including an inverter compressor. An inverter compressor 11 is configured so that the amount of refrigerant circulating in a refrigerant circuit 10 can be changed by changing the operating frequency by inverter control, and compresses the refrigerant flowing toward an indoor heat exchanger 16 which is a radiator. .. The expansion valve 14 changes the resistance when the refrigerant flowing toward the indoor heat exchanger 16 is depressurized by adjusting the opening degree of the expansion valve. The inverter compressor 11 is operated at an operating frequency determined based on the difference between the room temperature and the set heating temperature when the outdoor heat exchanger 13 which is an evaporator returns to the heating operation after defrosting. The expansion valve 14 is obtained by adding a correction value changed according to the difference between the room temperature and the set heating temperature to the opening degree before defrosting before defrosting when the outdoor heat exchanger 13 returns to the heating operation after defrosting. The expansion valve opening is adjusted to the opening when the heating is restored. [Selection diagram] Fig. 1

Description

  The present invention relates to an air conditioner, and more particularly to an air conditioner that performs defrosting of an evaporator.

  Conventionally, in an air conditioner equipped with an evaporator, a defrosting operation is performed in order to remove frost because frost forms on the evaporator during a heating operation. Some of these air conditioners interrupt the heating operation to heat the evaporator during the defrosting operation. Since the heating target space cannot be heated while the heating operation is interrupted, the room temperature of the heating target space may decrease. Thus, for example, in the air conditioner described in Patent Document 1 (Japanese Patent Laid-Open No. 60-71838), the start-up characteristic of the operation is improved when the operation is restarted by the indoor temperature control or the heating operation is resumed after the defrosting operation is completed. Therefore, control is performed to set the expansion valve opening of the electric expansion valve to an expansion valve opening larger by α than the expansion valve opening just before the start of the defrosting operation stored before the start of the defrosting operation.

  However, in the air conditioner described in Patent Document 1, since the compressor is only controlled to be on / off, the control is such that the expansion valve opening α always opens greatly when the defrosting operation is returned to the heating operation. ing. Let's apply the control described in Patent Document 1 to an air conditioner that uses an inverter compressor as a compressor and changes the operating frequency of the inverter compressor based on the difference between the room temperature of the space to be heated and the heating set temperature. This causes a problem. For example, when the value of α in Patent Document 1 is large, the opening of the expansion valve becomes too open when the room temperature that decreases during the defrosting operation is small, and the rise in the temperature of the condenser in the room becomes slow, It takes time to reach the heating set temperature. On the other hand, when the value of α in Patent Document 1 is small, if the operating frequency is significantly increased when the room temperature drops significantly during the defrosting operation and the operation returns to the heating operation, the expansion valve opening degree before the defrosting is increased. If the value obtained by adding α to the expansion valve opening is used, the expansion valve will not open sufficiently, causing an overshoot of the target discharge pipe temperature, and a protective function will be activated. May take a long time.

  The subject of this invention is shortening the time for a room temperature to reach the heating preset temperature vicinity at the time of heating operation return after a defrost in an air conditioner provided with an inverter compressor.

  An air conditioner according to a first aspect of the present invention performs heat exchange of a refrigerant by evaporating the refrigerant circulating in the refrigerant circuit and a radiator that performs heat exchange of the refrigerant in order to dissipate heat from the refrigerant circulating in the refrigerant circuit. An evaporator, an inverter compressor configured to change the refrigerant circulation amount of the refrigerant circuit by changing the operation frequency by inverter control, and compressing the refrigerant flowing toward the radiator, and between the radiator and the evaporator And an expansion valve that changes resistance when decompressing the refrigerant flowing toward the evaporator by adjusting the opening of the expansion valve, and the inverter compressor is at the time of heating operation return after defrosting of the evaporator, The expansion valve is operated at an operating frequency determined based on the difference between the room temperature of the heating target space and the heating set temperature, and when the expansion valve returns to the heating operation after defrosting of the evaporator, To the difference Flip expansion valve Altered correction value heating return time opening obtained in addition to the defrost before opening of the pre-defrost and is adjusted.

  In the air conditioner according to the first aspect, when the heating operation is resumed after defrosting the evaporator, the expansion valve opening degree is defrosted based on the difference between the room temperature of the space to be heated and the heating set temperature. Since it is adjusted to the opening degree at the time of heating return obtained in addition to the opening degree before defrosting, the operating frequency of the inverter compressor determined based on the difference between the room temperature of the heating target space and the heating set temperature is adjusted. Can be planned. For example, when the difference between the room temperature of the space to be heated and the heating set temperature is large and the operating frequency rises significantly compared to before defrosting, the opening degree at the time of heating return can be greatly widened, and the difference between them is small. When the operating frequency rise is smaller than that before defrosting, the opening degree at the time of return to heating can be adjusted so as not to increase too much.

  An air conditioner according to a second aspect of the present invention is the air conditioner according to the first aspect, wherein the correction value is determined based on the operating frequency of the inverter compressor.

  In the air conditioner according to the second aspect, since the correction value is determined based on the operating frequency of the inverter compressor, the expansion valve opening can be linked to the operating frequency of the inverter compressor.

  An air conditioner according to a third aspect of the present invention is the air conditioner according to the second aspect, wherein the inverter compressor is controlled to increase the operation frequency stepwise immediately after the return to heating operation, and the expansion valve is Immediately after the heating operation is restored, the expansion valve opening is controlled so as to increase stepwise with the operating frequency of the inverter compressor up to the opening at the time of heating restoration.

  In the air conditioner according to the third aspect, immediately after the heating operation is restored, the expansion valve opening is controlled so as to gradually increase to the opening at the time of heating restoration together with the operation frequency of the inverter compressor. It is possible to improve the temperature rise when returning to heating while protecting the machine.

  In the air conditioner according to the fourth aspect of the present invention, the inverter compressor is controlled so as to sequentially increase the operating frequency from the preset frequency to the target operating frequency when the inverter compressor is started up and when the thermo-off is changed from the thermo-off. The expansion valve is adjusted by feedback control from a preset expansion valve opening degree to an expansion valve opening degree at which the refrigerant circuit is stabilized at the time of start-up and when changing from thermo-off to thermo-on.

  In the air conditioner according to the fourth aspect, when starting and when changing from thermo-off to thermo-on, the expansion valve is independent of the difference between the room temperature and the heating set temperature, unlike when the defrosting operation is returned to the heating operation. Furthermore, the expansion valve opening is adjusted by feedback control from the preset expansion valve opening to the expansion valve opening at which the refrigerant circuit is stabilized.

  In the air conditioner according to the first aspect of the present invention, regardless of the difference between the room temperature of the heating target space and the heating set temperature, the time for the room temperature to reach the vicinity of the heating set temperature when the heating operation is resumed after defrosting. It can be shortened.

  In the air conditioner according to the second aspect of the present invention, it is possible to improve the function of suppressing an excessive increase in the target discharge pipe temperature caused by the room temperature greatly decreasing when the heating operation is restored, and the room temperature does not drop much when the heating operation is restored. In this case, it is possible to improve the function of preventing the expansion valve opening from being excessively opened.

  In the air conditioner according to the third aspect of the present invention, the effect of shortening the time required for the room temperature to reach the vicinity of the heating set temperature can be improved while protecting the inverter compressor.

  In the air conditioner according to the fourth aspect of the present invention, the inverter compressor is sufficiently protected.

A circuit diagram showing an outline of composition of an air harmony machine concerning an embodiment. The block diagram which shows the outline | summary of a structure of the control system of an air conditioner. (A) Timing chart showing the operating frequency of the inverter compressor at the time of defrosting, (b) Timing chart for explaining control regarding the upper limit of the indoor fan at the time of defrosting, (c) Four-way switching at the time of defrosting The timing chart for demonstrating operation | movement of a valve, (d) The timing chart for demonstrating control of the outdoor fan at the time of defrost, (e) The timing chart which shows the change of the expansion valve opening degree at the time of defrost. The flowchart for demonstrating control of the inverter compressor and expansion valve at the time of defrosting.

(1) Overall Configuration An overview of the configuration of an air conditioner according to an embodiment of the present invention will be described with reference to FIG. An air conditioner 1 shown in FIG. 1 includes an indoor unit 3 attached to an indoor wall surface and the like, and an outdoor unit 2 installed outdoors. The air conditioner 1 includes a refrigerant circuit 10 and can perform a vapor compression refrigeration cycle by circulating the refrigerant in the refrigerant circuit 10. In order to form the refrigerant circuit 10 in which the refrigerant circulates, the indoor unit 3 and the outdoor unit 2 are connected by a communication pipe 4. In addition, as shown in FIG. 2, the air conditioner 1 includes a control unit 50 for controlling internal devices. A remote controller 5 is attached to the air conditioner 1, and the remote controller 5 has a function of communicating with the control unit 50 using, for example, infrared rays. The user can make various settings for the air conditioner 1 using the remote controller 5.

(1-1) Refrigerant circuit 10
The refrigerant circuit 10 includes an inverter compressor 11, a four-way switching valve 12, an outdoor heat exchanger 13, an expansion valve 14, an accumulator 15, and an indoor heat exchanger 16. The inverter compressor 11 sucks the refrigerant from the suction port, and discharges the refrigerant compressed inside to the first port of the four-way switching valve 12 from the discharge port. The inverter compressor 11 is a variable capacity compressor that performs rotational speed control by an inverter. As the operating frequency of the inverter compressor 11 increases, the refrigerant circulation amount increases. Conversely, when the operation frequency decreases, the refrigerant circulation amount decreases.

  In addition to the first port, the four-way switching valve 12 includes a second port connected to the outdoor heat exchanger 13, a third port connected to the accumulator 15, and a fourth port connected to the indoor heat exchanger 16. And have. The four-way switching valve 12 includes a state indicated by a solid line in which the refrigerant flows between the first port and the second port and the refrigerant flows between the third port and the fourth port, and the first port and the fourth port. It is possible to switch between the state indicated by the broken line in which the refrigerant flows between the second port and the third port. The four-way switching valve 12 causes the refrigerant to flow between the first port and the fourth port and simultaneously causes the refrigerant to flow between the second port and the third port when the air conditioner 1 performs the heating operation. . Further, when the air conditioner 1 performs the cooling operation and the reverse cycle defrost operation, the four-way switching valve 12 causes the refrigerant to flow between the first port and the second port and at the same time the third port and the fourth port. Allow refrigerant to flow between ports.

  The outdoor heat exchanger 13 has a first inlet / outlet for circulating the refrigerant to / from the second port of the four-way switching valve 12 and a second inlet / outlet for circulating the refrigerant to / from the expansion valve 14. Have. The outdoor heat exchanger 13 causes heat exchange between the refrigerant flowing through a heat transfer tube (not shown) connected between the first entrance and the second entrance of the outdoor heat exchanger 13 and the outdoor air.

  The expansion valve 14 is disposed between the outdoor heat exchanger 13 and the indoor heat exchanger 16. The expansion valve 14 has a function of expanding and depressurizing the refrigerant flowing between the outdoor heat exchanger 13 and the indoor heat exchanger 16. The expansion valve 14 is configured to be able to change the opening degree of the expansion valve, and by reducing the opening degree of the expansion valve, the flow path resistance of the refrigerant passing through the expansion valve 14 is increased. Is increased, the flow path resistance of the refrigerant passing through the expansion valve 14 is reduced. Such an expansion valve 14 expands and depressurizes the refrigerant flowing from the indoor heat exchanger 16 toward the outdoor heat exchanger 13 in the heating operation, and from the outdoor heat exchanger 13 in the cooling operation and the reverse cycle defrost operation. The refrigerant flowing toward the indoor heat exchanger 16 is expanded and decompressed. Even if the state of other devices attached to the refrigerant circuit 10 does not change, the flow rate of the refrigerant flowing through the refrigerant circuit 10 changes when the expansion valve opening degree of the expansion valve 14 changes.

  The indoor heat exchanger 16 has a second inlet / outlet for flowing liquid refrigerant to / from the expansion valve 14, and a first for flowing gas refrigerant to / from the fourth port of the four-way switching valve 12. Has a doorway. The indoor heat exchanger 16 includes, for example, a plurality of fins and a plurality of heat transfer tubes that penetrate the plurality of fins. And heat exchange is performed between the refrigerant | coolant and indoor air which flow through the heat exchanger tube (not shown) connected between the 1st entrance / exit of the indoor heat exchanger 16. FIG. The indoor heat exchanger 16 functions as an evaporator or a radiator depending on the operation state of the indoor unit 3. In addition, although the indoor heat exchanger 16 comprised by the fin and the heat exchanger tube is demonstrated here, the indoor heat exchanger 16 used by this invention is restricted to a fin and tube type heat exchanger. Instead, for example, a heat exchanger using a flat multi-hole tube instead of the heat transfer tube may be used.

  An accumulator 15 is disposed between the third port of the four-way switching valve 12 and the suction port of the inverter compressor 11. In the accumulator 15, the refrigerant flowing from the third port of the four-way selector valve 12 to the inverter compressor 11 is separated into gas refrigerant and liquid refrigerant. A gas refrigerant is mainly supplied from the accumulator 15 to the suction port of the inverter compressor 11.

  The outdoor unit 2 includes an outdoor fan 21 that generates an air flow of outdoor air that passes through the outdoor heat exchanger 13 in order to promote heat exchange between the refrigerant flowing through the heat transfer tube and the outdoor air. The outdoor fan 21 is driven by an outdoor fan motor 21a that can change the rotational speed. The indoor unit 3 includes an indoor fan 31 that generates an air flow of indoor air that passes through the indoor heat exchanger 16 in order to promote heat exchange between the refrigerant flowing through the heat transfer tube and the room air. The indoor fan 31 is driven by an indoor fan motor 31a whose rotation speed can be changed.

(1-2) Overview of Configuration of Control System As shown in FIG. 2, the control unit 50 includes an outdoor control device 26 built in the outdoor unit 2 and a room built in the indoor unit 3. And a control device 35. The outdoor control device 26 and the indoor control device 35 are connected to each other through signal lines, and are configured to be able to transmit and receive signals to each other.

  The outdoor control device 26 of the outdoor unit 2 controls the inverter compressor 11, the four-way switching valve 12, the expansion valve 14, the outdoor fan 21, and the like. Therefore, the outdoor unit 2 includes an outdoor temperature sensor 22 for measuring the temperature of the outdoor air, an outdoor heat exchanger temperature sensor 23 for measuring the temperature of the refrigerant flowing in a specific place of the outdoor heat exchanger 13, and And a discharge pipe temperature sensor 24 for detecting the temperature of the refrigerant discharged from the inverter compressor 11 and a suction pipe temperature sensor 25 for detecting the temperature of the refrigerant drawn into the inverter compressor 11. . The outdoor control device 26 is connected to the outdoor temperature sensor 22 to the suction pipe temperature sensor 25 in order to receive a signal related to the temperature measured by the outdoor temperature sensor 22 to the suction pipe temperature sensor 25. The outdoor control device 26 includes, for example, a CPU (not shown) and a memory 26a, and is configured to be able to control the outdoor unit 2 in accordance with a program stored in the memory 26a.

  The indoor control device 35 of the indoor unit 3 controls the indoor fan 31 and the like. For this purpose, the indoor unit 3 includes a room temperature sensor 32 for measuring the temperature of the indoor air, and an indoor heat exchanger temperature sensor 33 for measuring the temperature of the refrigerant flowing in a specific place of the indoor heat exchanger 16. I have. And the indoor control apparatus 35 is connected to the room temperature sensor 32 and the indoor heat exchanger temperature sensor 33 in order to receive the signal regarding the temperature which the room temperature sensor 32 and the indoor heat exchanger temperature sensor 33 measured. The indoor control device 35 includes, for example, a CPU (not shown) and a memory 35a, and can control the indoor unit 3 according to a program stored in the memory 35a.

  The remote controller 5 includes an operation switch 51, an operation changeover switch 52, a temperature setting switch 53, an air direction setting switch 54 and an air volume setting switch 55. The user can set and operate the air conditioner 1 using these switches. The operation switch 51 is a switch for switching between the operation and the stop of the air conditioner 1, and the operation and the stop are alternately switched every time the operation switch 51 is operated. The operation changeover switch 52 is used, for example, when selecting between a cooling operation and a heating operation. The temperature setting switch 53 is a switch used to input a room temperature desired by the user. The wind direction setting switch 54 is a switch for performing settings related to the wind direction. The air volume setting switch 55 is a switch used for inputting the air volume.

  The control unit 50 sets the target temperature Tt based on the set temperature Ts input using the temperature setting switch 53. In the heating operation, for example, a temperature (Ts + α1) obtained by adding a constant value α1 to the set temperature Ts is set as the target temperature Tt. Alternatively, the target temperature Tt may be a temperature (Ts + β1) obtained by subtracting the value β1 calculated according to a predetermined function f1 (x) from the set temperature Ts. When the room temperature Tr becomes higher than the target temperature Tt, the control unit 50 causes the air conditioner 1 to be thermo-off. In addition, if the room temperature Tr becomes lower than the temperature (Ts−α2) obtained by subtracting the constant value α2 from the set temperature Ts, the control unit 50 causes the air conditioner 1 to be thermo-on. Alternatively, when the room temperature Tr becomes lower than the temperature (Ts−β1) obtained by subtracting the value β2 calculated according to the predetermined function f2 (x) from the set temperature Ts, the controller 50 causes the air conditioner 1 to be thermo-ON. It may be set as follows. In the thermo-on state, the inverter compressor 11 is driven and there is heat transfer by the refrigerant, but in the thermo-off state, the inverter compressor 11 is stopped and the heat transfer by the refrigerant is stopped.

  The control unit 50 controls various devices constituting the air conditioner 1 based on the measurement values of various sensors as described above and the commands input from the remote controller 5. The operation frequency of the inverter compressor 11 during the heating operation is determined by the control unit 50 based on the difference (Tr−Ts) between the room temperature Tr and the heating set temperature Ts. In other words, the determination based on the difference between the room temperature Tr and the heating set temperature Ts (Tr−Ts) is determined based on the difference between the room temperature Tr and the target temperature Tt (Tr−Tt). . Normally, when the difference between the room temperature Tr and the heating set temperature Ts (Tr−Ts) increases, the control unit 50 increases the operating frequency of the inverter compressor 11 because it is necessary to supply a large amount of heat energy. If the expansion valve opening degree of the expansion valve 14 is left as it is when the operating frequency of the inverter compressor 11 is increased, the temperature of the refrigerant discharged from the inverter compressor 11 rises. The control unit 50 uses the discharge pipe temperature sensor 24 to control so that the temperature of the refrigerant discharged from the inverter compressor 11 does not rise excessively. For example, when the detected temperature of the discharge pipe temperature sensor 24 exceeds a preset threshold value, control is performed to stop the inverter compressor 11 to protect the inverter compressor 11. Further, the control unit 50 may be configured to control the expansion valve opening degree of the expansion valve 14 in order to control the temperature of the refrigerant discharged from the inverter compressor 11. The temperature of the refrigerant discharged from the inverter compressor 11 is detected as the discharge pipe temperature. For example, the control unit 50 calculates a discharge pipe temperature that gives an appropriate refrigeration effect from the temperatures detected by the outdoor heat exchanger temperature sensor 23 and the indoor heat exchanger temperature sensor 33 so that the calculated discharge pipe temperature is obtained. To control the opening of the expansion valve.

(2) Overview of heating operation, cooling operation and reverse cycle defrost operation
(2-1) Heating operation When the air conditioner 1 is in the heating operation, the four-way switching valve 12 switches to the broken line state shown in FIG. In a state after the four-way switching valve 12 is switched, the high-temperature and high-pressure refrigerant discharged from the inverter compressor 11 flows into the indoor heat exchanger 16 through the four-way switching valve 12. At this time, the indoor heat exchanger 16 functions as a radiator. Therefore, as it flows through the indoor heat exchanger 16, the refrigerant is cooled by radiating heat when it heats the indoor air in heat exchange with the indoor air. The low-temperature and high-pressure refrigerant deprived of the temperature by the indoor heat exchanger 16 is decompressed by the expansion valve 14 and is changed to a low-temperature and low-pressure refrigerant. The refrigerant that has flowed into the outdoor heat exchanger 13 via the expansion valve 14 is warmed by heat exchange with the outdoor air. At this time, the outdoor heat exchanger 13 functions as an evaporator. Then, low-temperature gas refrigerant is mainly sucked into the inverter compressor 11 from the outdoor heat exchanger 13 through the four-way switching valve 12 and the accumulator 15. In the forward cycle, the refrigerant is flowed in the order of the inverter compressor 11, the indoor heat exchanger 16, the expansion valve 14, and the outdoor heat exchanger 13, and such a vapor compression refrigeration cycle is repeated.

(2-2) Cooling Operation When the air conditioner 1 is in the cooling operation, the four-way switching valve 12 switches to the solid line state shown in FIG. In a state after the four-way switching valve 12 is switched, the high-temperature and high-pressure refrigerant discharged from the inverter compressor 11 flows into the outdoor heat exchanger 13 through the four-way switching valve 12. At this time, the outdoor heat exchanger 13 functions as a radiator. Therefore, the refrigerant is cooled as it flows through the outdoor heat exchanger 13 due to heat radiation during heat exchange with the outdoor air. The low-temperature and high-pressure refrigerant whose temperature has been deprived by the outdoor heat exchanger 13 is reduced in pressure by the expansion valve 14 and changed to a low-temperature and low-pressure refrigerant. The refrigerant that has flowed into the indoor heat exchanger 16 via the expansion valve 14 cools the indoor air and heats itself when exchanging heat with the indoor air. At this time, the indoor heat exchanger 16 functions as an evaporator. Then, low-temperature gas refrigerant is mainly sucked into the inverter compressor 11 from the indoor heat exchanger 16 through the four-way switching valve 12 and the accumulator 15.

(2-3) Reverse cycle defrost operation Reverse cycle defrost operation is performed in order to remove the frost adhering to the outdoor heat exchanger 13 by having performed heating operation. Therefore, it switches to reverse cycle defrost operation in the middle of heating operation, and when reverse cycle defrost operation is completed, it returns to heating operation again. In the reverse cycle defrost operation, as in the cooling operation, the four-way switching valve 12 is switched to the solid line state shown in FIG. In the reverse cycle defrost operation, the same vapor compression refrigeration cycle as in the cooling operation is repeated. In other words, the reverse cycle defrost operation is performed in the reverse cycle defrost operation as opposed to the normal cycle during the heating operation, and the refrigerant flows in the order of the inverter compressor 11, the outdoor heat exchanger 13, the expansion valve 14, and the indoor heat exchanger 16. This is a reverse cycle in which the compression refrigeration cycle is repeated.

  The operation of the air conditioner 1 related to the reverse cycle defrost operation will be described with reference to the timing charts shown in FIGS. 3 (a) to 3 (e). The operation when returning from the reverse cycle defrost operation to the heating operation will be described with reference to the flowchart of FIG. At time t1 after it is decided to perform the reverse cycle defrost operation, as shown in FIG. 3B, in the indoor unit 3, the upper limit of the rotational speed of the indoor fan 31 is the normal heating operation. Switch from time limit to defrost limit. When the restriction for defrosting is imposed on the indoor fan 31, even if the maximum air volume is set by the air volume setting switch 55, the control unit 50 sets the rotation speed of the indoor fan 31 higher than the rotation speed at the maximum air volume. Limit to a small number of revolutions. By providing such a defrosting restriction on the rotational speed of the indoor fan 31, the discomfort felt by the user due to the cold air blown during the defrosting operation is suppressed.

  Based on the difference between the room temperature and the heating set temperature at the time t1, the control unit 50 determines the target operating frequency when returning to the heating operation after defrosting. Further, the control unit 50 monitors the expansion valve opening degree of the expansion valve 14 (step S1). When there is an instruction for defrosting operation (step S2), the control unit 50 determines the expansion valve opening degree at this time t1 as the opening degree BO before defrosting (step S3), and writes and stores it in the memory 26a. To do.

  And the control part 50 performs a defrost driving | operation (step S4). By the way, at the time of defrosting, since heating cannot be performed, the room temperature Tr generally decreases. Considering that the room temperature Tr decreases due to defrosting, the target operating frequency immediately before defrosting is usually lower than the appropriate operating frequency of the inverter compressor 11 when the heating operation is restored after defrosting. is there. That is, when the normal heating operation is started after returning to the heating operation, since the room temperature Tr is lowered, the operation frequency of the inverter compressor 11 becomes higher than the target operation frequency immediately before the defrosting. If the expansion valve 14 is set to the opening degree BO before defrosting in the refrigerant circuit 10 in which the inverter compressor 11 is operated at an operation frequency higher than the target operation frequency immediately before defrosting, the temperature of the refrigerant discharged from the inverter compressor 11 is excessive. It becomes easy to rise.

  Therefore, the control unit 50 calculates the opening AO during heating return obtained by adding the correction value CV changed according to the difference between the room temperature Tr and the heating set temperature Ts to the opening degree BO before the defrosting. . For this purpose, the control unit 50 calculates the correction value CV, and the calculation of the correction value CV and the heating return opening AO will be described later.

  In the outdoor unit 2, the outdoor control device 26 starts control to gradually lower the operating frequency of the inverter compressor 11 from time t1. And it turns out from the timing chart of Fig.3 (a) which shows the operating frequency of the inverter compressor 11 that the inverter compressor 11 was stopped at the time t2. When the inverter compressor 11 is stopped and the operation frequency of the inverter compressor 11 becomes 0, the pressures on the indoor heat exchanger 16 side and the outdoor heat exchanger 13 side of the four-way switching valve 12 become approximately the same. Pressure equalization is performed.

  As shown in FIG. 3C showing the operation of the four-way switching valve 12, after the pressure equalization is performed and the state suitable for switching the four-way switching valve 12 is reached, at time t3, four The path switching valve 12 is switched from the heating side to the cooling side (reverse cycle defrost operation side). That is, the four-way switching valve 12 is switched from the broken line connection state in FIG. 1 to the solid line connection state. After the four-way switching valve 12 is switched, the inverter compressor 11 starts driving (time t4 in FIG. 3A). As shown in FIG. 3D, the driving of the outdoor fan 21 is stopped from time t4. Illustrations such as the operating frequency of the inverter compressor 11 and the opening degree of the expansion valve during defrosting are omitted.

  When the defrost operation ends, the operation frequency of the inverter compressor 11 is gradually decreased from time t5 to the remaining operation frequency Fx, and the remaining operation frequency Fx is held for a predetermined time from time t6. By this residual operation, the pressure difference from the first port to the fourth port of the four-way switching valve 12 is relaxed. When the residual operation is completed (time t7), the outdoor control device 26 of the control unit 50 stops the inverter compressor 11. Then, with the inverter compressor 11 stopped, the four-way selector valve 12 is switched from the solid line connection to the broken line connection (time t8) as shown in FIG. That is, the refrigerant discharged from the inverter compressor 11 is sent to the indoor heat exchanger 16, and the refrigerant flowing out of the outdoor heat exchanger 13 is switched to a path for sucking into the inverter compressor 11. At this time, the driving of the outdoor fan 21 is started as shown in FIG.

  The indoor control device 35 starts the inverter compressor 11 from time t9, and shifts the upper limit of the rotational speed of the indoor fan 31 from the defrosting limit to the heating limit. The indoor control device 35 receives the room temperature Tr9 detected by the room temperature sensor 32 at the end of the period when the inverter compressor 11 is stopped (time t9). The control unit 50 calculates the correction value CV according to the difference ΔT (= Tr9−Ts) between the room temperature Tr9 and the heating set temperature Ts when returning to the heating operation (time t9) (step S5). In general, when the difference between the room temperature Tr and the heating set temperature Ts when returning to the heating operation is expressed as ΔT, CV is a function f3 of ΔT. That is, CV = f3 (ΔT). This function f3 (ΔT) is stored in the control unit 50 as, for example, a mathematical expression or a table obtained from a simulation or an experiment with an actual machine. The correction value CV is calculated using a function f3 (ΔT) or the like stored in the control unit 50 as such an equation or a table. Using this calculated correction value CV, the control unit 50 calculates the opening degree AO when returning to heating. And at the time of heating operation return, the control part 50 uses opening degree AO (= BO + CV) at the time of heating return as an expansion valve opening degree. As described above, the temperature difference (Tr9−Ts) may be used to obtain the correction value CV that is changed according to the difference between the room temperature Tr and the heating set temperature Ts. Since the operating frequency of the inverter compressor 11 is determined based on the difference between the room temperature Tr and the heating set temperature Ts (Tr−Ts), the correction value CV may be calculated using the operating frequency at time t9. .

  The controller 50 increases the operating frequency of the inverter compressor 11 stepwise from time t9 to time t10 in order to protect the inverter compressor 11. At time t9 and time t10, the temperature does not change so much, and it can be considered that the room temperature Tr9 at time t9 and the room temperature Tr10 at time t10 are substantially the same (Tr9≈Tr10). When the outdoor heat exchanger 13 that functions as an evaporator during heating operation returns to the heating operation after defrosting, the control unit 50 operates based on the difference between the room temperature Tr9 of the room that is the heating target space and the heating set temperature Ts. And the inverter compressor 11 is controlled so as to be operated at time t10 at the determined operation frequency. Further, the control unit 50 gradually increases the expansion valve opening degree from time t9 to time t10, and adjusts the expansion valve opening degree so as to be the heating return opening degree AO at time t10 (step S6).

  At time t10, since the room temperature Tr decreases during the reverse cycle defrost operation, the operation frequency of the inverter compressor 11 increases by ΔF compared to the target operation frequency Fw immediately before defrosting. Since the opening degree AO at the time of heating return is larger than the opening degree BO before defrosting by the correction value CV, the opening degree of the expansion valve is too narrow or too open with respect to the target operating frequency (Fw + ΔF) at time t10. It becomes an appropriate state without doing.

  When the operation frequency of the inverter compressor 11 reaches the target operation frequency (Fw + ΔF) (step S7), the control unit 50 determines the operation frequency of the inverter compressor 11 and the expansion valve 14 according to the room temperature Tr and the heating set temperature Ts. The routine proceeds to normal operation for controlling the opening degree of the expansion valve (step S8).

(2-4) Operation when starting and when changing from thermo-off to thermo-on The operation of the inverter compressor 11 and the expansion valve 14 at the time of returning to the heating operation described above is the operation when starting and changing from thermo-off to thermo-on. Is different. The inverter compressor 11 is controlled by the control unit 50 so as to sequentially increase the operation frequency from the preset initial frequency to the target operation frequency when the inverter compressor 11 is started up and when the thermo-off is changed from the thermo-off.

  Further, the expansion valve 14 is adjusted by feedback control from a preset initial expansion valve opening to an expansion valve opening at which the refrigerant circuit 10 is stabilized when starting and when the thermo-off is changed from the thermo-off. The initial expansion valve opening when starting and when changing from thermo-off to thermo-on is a constant value determined independently of the room temperature Tr and the heating set temperature Ts. The initial expansion valve opening is an opening that is closer to a fully open state than the opening AO during heating return.

(3) Features (3-1)
In the air conditioner 1 of the above embodiment, when the outdoor heat exchanger 13 (an example of an evaporator) returns to the heating operation after defrosting, the expansion valve opening degree of the expansion valve 14 is a room to be heated, for example, room temperature of the room The correction value CV determined based on the difference between Tr and the heating set temperature Ts is adjusted to the heating return opening AO obtained by adding the correction value CV before the defrosting to the opening degree BO before the defrosting. From this, it is possible to achieve harmony with the operating frequency of the inverter compressor 11 determined based on the difference (Tr−Ts) between the room temperature Tr and the heating set temperature Ts. For example, when the difference between the room temperature Tr and the heating set temperature Ts (Tr−Ts) is large and the operating frequency is significantly increased compared to before the defrosting, the opening AO during heating return of the expansion valve 14 can be greatly widened. If the difference between them is small and the increase width of the operating frequency is small compared with that before defrosting, the opening AO at the time of heating return can be adjusted so as not to increase too much. As a result, regardless of the difference (Tr−Ts) between the room temperature Tr and the heating set temperature Ts, the time for the room temperature Tr to reach the vicinity of the heating set temperature Ts when returning to the heating operation after defrosting can be shortened. it can. Note that the radiator when the outdoor heat exchanger 13 functions as an evaporator is the indoor heat exchanger 16.

(3-2)
In the above embodiment, the operating frequency of the inverter compressor 11 is determined based on the difference (Tr−Ts) between the room temperature Tr and the heating set temperature Ts. The correction value CV is also determined based on the difference (Tr−Ts) between the room temperature Tr and the heating set temperature Ts. Therefore, it can be said that the correction value CV is determined based on the operating frequency of the inverter compressor 11. Since the correction value CV is determined based on the operating frequency of the inverter compressor 11, the expansion valve opening can be linked to the operating frequency of the inverter compressor 11. As a result, it is possible to improve the function of suppressing the excessive increase in the target discharge pipe temperature caused by the room temperature Tr greatly decreasing at the time of heating operation return, and when the room temperature Tr does not decrease much at the time of heating operation return, the expansion valve opening degree is opened. It is possible to improve the function of suppressing excess.

(3-3)
In the above embodiment, immediately after the heating operation is restored from time t9 to time t10, the expansion valve opening of the expansion valve 14 is increased stepwise to the heating return opening AO together with the operation frequency of the inverter compressor 11. Since it is controlled, the temperature rise at the time of heating return can be improved while protecting the inverter compressor 11. The effect of shortening the time for the room temperature to reach the vicinity of the heating set temperature can be improved while protecting the inverter compressor 11 without rapidly increasing the operating frequency of the inverter compressor 11.

(3-4)
In the air conditioner 1 of the above embodiment, when starting and when changing from thermo-off to thermo-on, the expansion valve 14 is different from the difference between the room temperature and the heating set temperature, unlike when the defrosting operation is returned to the heating operation. Irrespective of the initial expansion valve opening degree set in advance, the expansion valve opening degree at which the refrigerant circuit is stabilized is adjusted by feedback control. At this time, the inverter compressor 11 is controlled so as to sequentially increase the operation frequency from the preset initial frequency to the target operation frequency. For this reason, it takes time for the expansion valve opening of the expansion valve 14 to stabilize, and it takes time to reach the heating set temperature, but gradually decreases from the initial expansion valve opening larger than the heating return opening AO. Therefore, the inverter compressor is sufficiently protected.

(4) Modification (4-1) Modification 1A
Although the case where the reverse cycle defrost operation is performed as the defrost operation has been described in the above embodiment, the defrost operation that can be performed by the air conditioner to which the present invention is applied is not limited to the reverse cycle defrost operation. The present invention is applied to the air conditioner which starts the heating operation after the return to heating in the state of the lowered room temperature Tr when the air conditioner temporarily interrupts the heating operation for defrosting and lowers the room temperature Tr. Can be applied.

(4-2) Modification 1B
In the above embodiment, the case where the correction value CV is calculated using the operation frequency of the inverter compressor 11 as a numerical value other than the difference between the room temperature Tr and the heating set temperature Ts has been described. However, any numerical value other than the difference between the room temperature Tr and the heating set temperature Ts may be used as long as it is a value that can derive the room temperature Tr and the heating set temperature Ts.

(4-3) Modification 1C
In the above-described embodiment, the case where the expansion valve opening is gradually increased from time t9 to time t10 has been described. However, at time t9, the opening is changed to the heating return opening AO and the state is maintained until time t10. You may comprise.

DESCRIPTION OF SYMBOLS 1 Air conditioner 2 Outdoor unit 3 Indoor unit 10 Refrigerant circuit 11 Inverter compressor 12 Four-way switching valve 13 Outdoor heat exchanger 14 Outdoor valve 16 Indoor heat exchanger 21 Outdoor fan 22 Outdoor temperature sensor 23 Outdoor heat exchanger temperature sensor 24 Discharge pipe temperature sensor 25 Suction pipe temperature sensor 31 Indoor fan 32 Indoor temperature sensor 33 Indoor heat exchanger temperature sensor

JP 60-71838 A

Claims (4)

A radiator (16) for exchanging heat of the refrigerant in order to dissipate heat from the refrigerant circulating in the refrigerant circuit (10);
An evaporator (13) for evaporating the refrigerant circulating in the refrigerant circuit and exchanging heat of the refrigerant;
An inverter compressor (11) configured to change a refrigerant circulation amount of the refrigerant circuit by changing an operation frequency by inverter control, and compressing a refrigerant flowing toward the radiator;
An expansion valve (14) that is disposed between the radiator and the evaporator and changes a resistance when the refrigerant flowing toward the evaporator is depressurized by adjusting an expansion valve opening;
With
The inverter compressor is operated at an operation frequency determined based on a difference between a room temperature of a space to be heated and a heating set temperature at the time of heating operation return after defrosting of the evaporator,
The expansion valve sets a correction value, which is changed according to a difference between a room temperature of the heating target space and the heating set temperature, to a pre-defrost opening before defrosting when the evaporator returns to the heating operation after defrosting. An air conditioner in which the opening degree of the expansion valve is adjusted to the opening degree when heating is additionally obtained. The correction value is determined based on the operating frequency of the inverter compressor.
The air conditioner according to claim 1. The inverter compressor is controlled to increase the operation frequency stepwise immediately after the return to heating operation,
The expansion valve is controlled such that immediately after the heating operation is restored, the expansion valve opening is gradually increased to the opening at the time of heating restoration together with the operating frequency of the inverter compressor.
The air conditioner according to claim 2. The inverter compressor is controlled to sequentially increase the operation frequency from a preset frequency to a target operation frequency when starting and when changing from thermo-off to thermo-on,
The expansion valve is adjusted by feedback control from a preset expansion valve opening to an expansion valve opening at which the refrigerant circuit is stabilized when starting and when changing from thermo-off to thermo-on,
The air conditioner as described in any one of Claim 1 to 3.

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