WO2014112322A1

WO2014112322A1 - Air conditioner

Info

Publication number: WO2014112322A1
Application number: PCT/JP2013/085080
Authority: WO
Inventors: 円上野
Original assignee: シャープ株式会社
Priority date: 2013-01-16
Filing date: 2013-12-27
Publication date: 2014-07-24
Also published as: JP2014137165A; CN104903656B; JP5997060B2; CN104903656A

Abstract

An air conditioner (1) comprises: an outdoor heat exchanger (14); an indoor heat exchanger (32); an expansion valve (15) which is disposed between the outdoor heat exchanger and the indoor heat exchanger; a compressor (12) which circulates a refrigerant through a refrigeration cycle; and a switching valve (13) which switches the circulation of the refrigerant by the compressor between circulation for cooling, in which the refrigerant discharged from the compressor first enters the outdoor heat exchanger, and circulation for heating, in which the refrigerant discharged from the compressor first enters the indoor heat exchanger. During heating operation, at a stage prior to a step for defrosting the outdoor heat exchanger, a control unit (40) can perform either first preliminary defrosting operation in which the degree of opening of the expansion valve is reduced or a second preliminary defrosting operation in which the degree of opening of the expansion valve is increased.

Description

Air conditioner

The present invention relates to a heat pump type air conditioner.

Home air conditioners adopt a heat pump system and are separated into outdoor units and indoor units. When heating operation is performed with such an air conditioner, the indoor heat exchanger becomes hot while the outdoor heat exchanger becomes cold. As a result, the problem of frost formation in the outdoor heat exchanger cannot be avoided. Accordingly, various measures have been taken to solve the problem of frost formation on the outdoor heat exchanger during heating operation.

In the air conditioner described in Patent Document 1, an outdoor heat exchanger, a connecting portion of a pressure reducing device, and a discharge portion of a compressor are connected by a refrigerant path having an on-off valve. The on-off valve opens when the pressure of the high-pressure side refrigerant path during heating or the temperature of the indoor heat exchanger exceeds a predetermined value. When the on-off valve is opened, part of the high-temperature and high-pressure refrigerant discharged from the compressor flows into the outdoor heat exchanger while being reduced in pressure in the refrigerant path, and is liquefied in the indoor heat exchanger and depressurized in the pressure reducing device. Then, it merges with the low-temperature and low-pressure refrigerant. Thereby, the refrigerant | coolant pressure and temperature of an outdoor heat exchanger become higher than usual, and the advancing speed of the frost formation to an outdoor heat exchanger surface falls.

In the defrosting apparatus described in Patent Document 2, defrosting is performed as follows. That is, at the time of defrosting, the valve opening of the decompression device is fully opened or almost fully opened, the forced ventilation of the condenser / evaporator is stopped, and the compressor is operated.

There are the following types of air conditioners of the same separate type. That is, the indoor unit is configured as a radiation panel, and the room is cooled or heated by heat radiation without using a fan. An example of this can be seen in US Pat.

The air conditioner described in Patent Document 3 includes a radiation panel disposed on the ceiling of the building. Inside the radiation panel, refrigerant piping is arranged in a meandering manner. At the time of cooling operation, heat is absorbed by the radiant panel and radiant cooling is performed. During heating operation, heat is radiated from the radiant panel and radiant heating is performed. Radiant air conditioning is free from air agitation and noise from indoor fans, and can perform quiet and comfortable air conditioning.

JP-A-1-260266 Japanese Patent Application Laid-Open No. 60-50352 Japanese Patent Laid-Open No. 10-205802

Although the defrosting process of the outdoor unit during heating operation is inevitable, it temporarily inconveniences the user due to temporary interruption of heating. This invention is made | formed in view of this point, and aims at delaying the implementation time of a defrost process as much as possible.

The air conditioner according to the present invention is configured as follows. That is, the air conditioner includes an outdoor heat exchanger, an indoor heat exchanger, an expansion valve disposed between the outdoor heat exchanger and the indoor heat exchanger, the outdoor heat exchanger, A compressor that circulates refrigerant in a refrigeration cycle including the indoor heat exchanger and the expansion valve, and refrigerant circulation by the compressor, the refrigerant discharged from the compressor is the outdoor heat exchanger first. A switching valve that switches between circulation during cooling entering and circulation during heating when refrigerant discharged from the compressor first enters the indoor heat exchanger, and a controller of the air conditioner. The controller increases a first preliminary defrosting operation for reducing the opening degree of the expansion valve or an opening degree of the expansion valve at a stage before the defrosting step of the outdoor heat exchanger during the heating operation. The second preliminary defrosting operation can be performed.

In the air conditioner having the above configuration, the control unit may perform a defrosting step of the outdoor heat exchanger after performing the first preliminary defrosting operation or the second preliminary defrosting operation a predetermined number of times. preferable.

In the air conditioner configured as described above, the control unit performs the first preliminary defrosting operation when the outside air temperature is equal to or higher than a predetermined temperature, and performs the second preliminary defrosting operation when the outside air temperature is lower than the predetermined temperature. It is preferable to carry out.

In the air conditioner having the above configuration, it is preferable that the control unit switches the heating circulation to the cooling circulation in the defrosting step.

In the air conditioner having the above-described configuration, it is preferable that the control unit executes the first preliminary defrosting operation and the second preliminary defrosting operation when triggered by a frost determination on the outdoor heat exchanger.

In the air conditioner having the above-described configuration, the control unit performs the frost determination by detecting a change in temperature detected by a temperature detector attached to the outdoor heat exchanger, or an outdoor fan attached to the outdoor heat exchanger. Current change, measurement result of an air flow meter that measures the air volume of the airflow passing through the outdoor heat exchanger, or the length of time that the first preliminary defrosting operation or the second preliminary defrosting operation was not executed It is preferable to carry out based on the above.

In the air conditioner having the above-described configuration, it is preferable that the control unit increases the rotational speed of the outdoor blower during execution of the first preliminary defrosting operation or the second preliminary defrosting operation.

In the air conditioner having the above configuration, the control unit decreases the rotation speed of the compressor during the execution of the first preliminary defrosting operation, and increases the rotation speed of the compressor during the execution of the second preliminary defrosting operation. It is preferable to make it.

In the air conditioner configured as described above, it is preferable that an execution time of the preliminary defrosting operation is 1 minute or less per time.

In the air conditioner configured as described above, it is preferable that the outdoor heat exchanger is configured by a parallel flow heat exchanger.

According to the present invention, it is possible to delay the time when the normal defrosting is necessary by performing the preliminary defrosting before the normal defrosting process. Therefore, the heating operation can be continued for a long time until the normal defrosting step.

It is a schematic block diagram of the air conditioner which concerns on 1st Embodiment of this invention, and shows the state at the time of air_conditionaing | cooling operation. It is a schematic block diagram of the air conditioner which concerns on 1st Embodiment of this invention, and shows the state at the time of heating operation. It is a schematic block diagram of a parallel flow type heat exchanger. FIG. 4 is a sectional view taken along line IV-IV in FIG. 3. It is a control block diagram of the air conditioner of 1st Embodiment. It is a graph explaining the conventional defrost cycle. It is a graph explaining the defrost cycle of this invention. It is a flowchart explaining preliminary defrosting. It is a table | surface of the experimental result regarding the heating capability at the time of performing the case where it does not perform preliminary defrosting. It is a graph of the part of average heating capacity in the table | surface of FIG. It is a graph of the part of heating time in the table | surface of FIG. It is a graph of the experimental result which investigated the influence which the expansion valve opening change time has on average heating capacity. It is a graph of the experimental result which investigated the influence which the repetition frequency of preliminary defrost has on average heating capacity. It is a graph of the experimental result which investigated the influence which the rotation speed of an outdoor side fan has on average heating capacity. It is a table | surface of the experimental result which investigated whether the effect which preliminary | backup defrost brings about changes with types of heat exchangers. FIG. 16 is a graph of the table of FIG.

1 to 14, the air conditioner 1 according to the embodiment of the present invention will be described. In the air conditioner 1, a side flow parallel flow type heat exchanger is used as a heat exchanger.

Fig. 3 shows the basic structure of the side flow parallel flow heat exchanger. In FIG. 3, the upper side of the paper is the upper side of the heat exchanger, and the lower side of the paper is the lower side of the heat exchanger. The parallel flow heat exchanger 50 includes two

vertical header pipes

51 and 52 and a plurality of horizontal flat tubes 53 disposed therebetween. The

header pipes

51 and 52 are arranged in parallel at intervals in the horizontal direction. The flat tubes 53 are arranged at a predetermined pitch in the vertical direction. In the actual mounting stage, the heat exchanger 50 is installed at various angles according to design requirements. Accordingly, the “vertical direction” and “horizontal direction” in the present specification should not be strictly interpreted. It should be understood as a mere measure of direction.

The flat tube 53 is an elongated molded product obtained by extruding a metal. As shown in FIG. 4, a refrigerant passage 54 for circulating a refrigerant is formed inside the flat tube 53. Since the flat tube 53 is arranged so that the extrusion molding direction, which is the longitudinal direction, is horizontal, the refrigerant flow direction of the refrigerant passage 54 is also horizontal. A plurality of refrigerant passages 54 having the same cross-sectional shape and the same cross-sectional area are arranged in the left-right direction of FIG. Each refrigerant passage 54 communicates with the

header pipes

51 and 52.

A fin 55 is attached to the flat surface of the flat tube 53. Here, corrugated fins are used as the fins 55, but plate fins may also be used. Of the fins 55 arranged vertically, side plates 56 are arranged outside the uppermost and lowermost fins.

The

header pipes

51 and 52, the flat tubes 53, the fins 55, and the side plates 56 are all made of a metal having good thermal conductivity such as aluminum. The flat tube 53 is fixed to the

header pipes

51 and 52, the fin 55 is fixed to the flat tube 53, and the side plate 56 is fixed to the fin 55 by brazing or welding.

The inside of the header pipe 51 is partitioned into two sections S1 and S2 by a single partition P1. The partition part P1 divides the plurality of flat tubes 53 into a plurality of flat tube groups. A flat tube group consisting of 12 out of a total of 24 flat tubes 53 is connected to the section S1. A flat tube group consisting of 12 flat tubes 53 is also connected to the section S2. In addition, the number of the flat tubes 53 shown here is an example, and is not limited to this.

The interior of the header pipe 52 is partitioned into three sections S3, S4, and S5 by two partition portions P2 and P3. The partition parts P2 and P3 divide the plurality of flat tubes 53 into a plurality of flat tube groups. A flat tube group consisting of four of the total 24 flat tubes 53 is connected to the section S3. A flat tube group consisting of 15 flat tubes 53 is connected to the section S4. A flat tube group consisting of five flat tubes 53 is connected to the section S5.

The total number of the flat tubes 53 described above, the number of partition portions inside each header pipe and the number of partitions partitioned thereby, and the number of flat tubes 53 for each flat tube group divided by the partition portions are merely examples. Yes, it does not limit the invention.

A refrigerant access pipe 57 is connected to the compartment S3. A refrigerant inlet / outlet pipe 58 is connected to the section S5.

The function of the heat exchanger 50 is as follows. When the heat exchanger 50 is used as a condenser, the refrigerant is supplied to the compartment S3 through the refrigerant inlet / outlet pipe 57. The refrigerant that has entered the compartment S3 travels through the four flat tubes 53 connecting the compartment S3 and the compartment S1 to the compartment S1. The flat tube group formed by the four flat tubes 53 constitutes the refrigerant path A. The refrigerant path A is symbolized by a block arrow. Other refrigerant paths are also symbolized by block arrows.

The refrigerant that has entered the compartment S1 turns back and passes through the eight flat tubes 53 that connect the compartment S1 and the compartment S4 to the compartment S4. The flat tube group formed by the eight flat tubes 53 constitutes the refrigerant path B.

The refrigerant that has entered the compartment S4 is turned back and passes through the seven flat tubes 53 connecting the compartment S4 and the compartment S2 toward the compartment S2. The flat tube group formed by the seven flat tubes 53 constitutes the refrigerant path C.

The refrigerant that has entered the compartment S2 is turned back there, and travels to the compartment S3 through the five flat tubes 53 that connect the compartment S2 and the compartment S5. The flat tube group formed by the five flat tubes 53 constitutes the refrigerant path D. The refrigerant entering the compartment S5 flows out from the refrigerant inlet / outlet pipe 58.

When the heat exchanger 50 is used as an evaporator, the refrigerant is supplied to the section S5 through the refrigerant inlet / outlet pipe 58. Subsequent refrigerant flows follow the refrigerant path when the heat exchanger 50 is used as a condenser. That is, the refrigerant enters the section S 1 through the route of the refrigerant path D → refrigerant path C → refrigerant path B → refrigerant path A and flows out from the refrigerant inlet / outlet pipe 57.

FIG. 1 shows a schematic configuration of a separate air conditioner 1 using the heat exchanger 50 as a component of a heat pump cycle. The air conditioner 1 includes an outdoor unit 10 and an indoor unit 30.

The outdoor unit 10 houses a compressor 12, a switching valve 13, an outdoor heat exchanger 14, an expansion valve 15, an outdoor blower 16, and the like in a housing 11 made of sheet metal parts and synthetic resin parts. is doing. The switching valve 13 is a four-way valve. A heat exchanger 50 is used as the outdoor heat exchanger 14. As the expansion valve 15, a valve whose opening degree can be controlled is used. The outdoor blower is a combination of a motor and a propeller fan.

The outdoor unit 10 is connected to the indoor unit 30 through two

refrigerant pipes

17 and 18. The refrigerant pipe 17 is intended to flow a liquid refrigerant, and a pipe that is thinner than the refrigerant pipe 18 is used. Therefore, the refrigerant pipe 17 may be referred to as “liquid pipe”, “narrow pipe”, or the like. The refrigerant pipe 18 is intended to flow a gaseous refrigerant, and is thicker than the refrigerant pipe 17. Therefore, the refrigerant pipe 18 may be referred to as “gas pipe”, “thick pipe”, or the like. For example, HFC R410A or R32 is used as the refrigerant.

A two-way valve 19 is provided in the refrigerant pipe connected to the refrigerant pipe 17 in the refrigerant pipe inside the outdoor unit 10. A three-way valve 20 is provided in the refrigerant pipe connected to the refrigerant pipe 18. The two-way valve 19 and the three-way valve 20 are closed when the

refrigerant pipes

17 and 18 are removed from the outdoor unit 10 to prevent the refrigerant from leaking from the outdoor unit 10 to the outside. When it is necessary to release the refrigerant from the outdoor unit 10 or from the entire refrigeration cycle including the indoor unit 30, the refrigerant is discharged through the three-way valve 20.

The indoor unit 30 houses an indoor heat exchanger 32, an indoor blower 33, and the like inside a casing 31 made of synthetic resin parts. The indoor heat exchanger 32 is a combination of three heat exchangers 32 A, 32 B, and 32 C like a roof that covers the indoor blower 33. Any or all of the heat exchangers 32 A, 32 B, and 32 C can be configured by the heat exchanger 50. The indoor blower 33 is a combination of a motor and a cross flow fan.

知る It is essential to know the temperature of each place in order to control the operation of the air conditioner 1. For this purpose, temperature detectors are arranged in the outdoor unit 10 and the indoor unit 30. In the outdoor unit 10, a temperature detector 21 is disposed in the outdoor heat exchanger 14. A temperature detector 22 is disposed in the discharge pipe 12 a serving as a discharge portion of the compressor 12. A temperature detector 23 is disposed in the suction pipe 12 b serving as a suction portion of the compressor 12. A temperature detector 24 is disposed in the refrigerant pipe between the expansion valve 15 and the two-way valve 19. A temperature detector 25 for measuring the outside air temperature is disposed at a predetermined location inside the housing 11. In the indoor unit 30, a temperature detector 34 is disposed in the indoor heat exchanger 32. Each of the

temperature detectors

21, 22, 23, 24, 25, and 34 is formed of a thermistor.

The control unit 40 shown in FIG. 5 is responsible for overall control of the air conditioner 1. The control unit 40 performs control so that the room temperature reaches a target value set by the user.

The control unit 40 issues operation commands to the compressor 12, the switching valve 13, the expansion valve 15, the outdoor blower 16, and the indoor blower 33. The control unit 40 receives output signals of the detected temperatures from the temperature detectors 21 to 25 and the temperature detector 34, respectively. The controller 40 issues operation commands to the compressor 12, the outdoor blower 16, and the indoor blower 33 while referring to output signals from the temperature detectors 21 to 25 and the temperature detector 34. The control unit 40 issues a state switching command to the switching valve 13 and the expansion valve 15.

FIG. 1 shows a state where the air conditioner 1 is performing a cooling operation or a defrosting operation. At this time, the compressor 12 circulates the refrigerant in a cooling mode, that is, a circulation mode in which the refrigerant discharged from the compressor 12 first enters the outdoor heat exchanger 14.

The high-temperature and high-pressure refrigerant discharged from the compressor 12 enters the outdoor heat exchanger 14 where heat exchange with outdoor air is performed. The refrigerant dissipates heat to the outdoor air and condenses. The refrigerant that is condensed to become liquid enters the expansion valve 15 from the outdoor heat exchanger 14 and is decompressed there. The decompressed refrigerant is sent to the indoor heat exchanger 32, expands to a low temperature and low pressure, and lowers the surface temperature of the indoor heat exchanger 32. The indoor side heat exchanger 32 whose surface temperature has been lowered absorbs heat from the indoor air, thereby cooling the room. After the heat absorption, the low-temperature gaseous refrigerant returns to the compressor 12. The airflow generated by the outdoor fan 16 promotes heat dissipation from the outdoor heat exchanger 14. The airflow generated by the indoor fan 33 promotes heat absorption of the indoor heat exchanger 32.

FIG. 2 shows a state where the air conditioner 1 is performing a heating operation. At this time, the switching valve 13 is switched to reverse the refrigerant flow during the cooling operation. The compressor 12 circulates the refrigerant in a circulation mode during heating, that is, in a circulation mode in which the refrigerant discharged from the compressor 12 first enters the indoor heat exchanger 32.

The high-temperature and high-pressure refrigerant discharged from the compressor 12 enters the indoor heat exchanger 32 where heat exchange with the indoor air is performed. The refrigerant dissipates heat to the room air and warms the room. The refrigerant that has dissipated heat and has become liquid by condensing enters the expansion valve 15 from the indoor heat exchanger 32 and is decompressed there. The decompressed refrigerant is sent to the outdoor heat exchanger 14 and expands to a low temperature and low pressure, thereby lowering the surface temperature of the outdoor heat exchanger 14. The outdoor heat exchanger 14 whose surface temperature has dropped absorbs heat from outdoor air. After the heat absorption, the low-temperature gaseous refrigerant returns to the compressor 12. The airflow generated by the outdoor blower 33 promotes heat radiation from the indoor heat exchanger 33. The airflow generated by the outdoor fan 16 promotes heat absorption by the outdoor heat exchanger 14.

When the outdoor heat exchanger 14 absorbs heat during the heating operation, moisture contained in outdoor air becomes frost and adheres to the outdoor heat exchanger 14. Since frost reduces the amount of air passing through the outdoor heat exchanger 14 and also reduces the heat exchange efficiency, it must be removed in the defrosting process. The present invention is characterized in that preliminary defrosting is performed before the defrosting step. Hereinafter, what the preliminary defrosting is will be described with reference to FIGS. 6 to 14.

In the graphs of FIGS. 6 and 7, the vertical axis indicates the heating capacity and the horizontal axis indicates the time. In the conventional control method shown in FIG. 6, the heating capacity increases after the start of the heating operation, and the high heating capacity is maintained until a certain point. However, since the heating capacity suddenly decreases due to frost formation at a certain point in time, the heating operation is stopped and the defrosting process is entered. After the defrosting process is completed, the heating operation is resumed. When performing reverse defrosting in the defrosting process (defrosting the outdoor unit to the condenser side by making the refrigerant flow the same as during cooling operation), defrosting requires a certain amount of time. To do. Therefore, the user had to put up with the room temperature going down during that time.

FIG. 7 shows the concept of the preliminary defrosting system according to the present invention. Prior to the normal full-scale defrosting process (hereinafter referred to as “normal defrosting” in the present specification), the preliminary defrosting is repeated to extend the heating operation period until the normal defrosting as much as possible. Is.

The control of the preliminary defrosting operation by the control unit 40 is performed as shown in the flowchart of FIG. After starting the heating operation, in step # 101, the control unit 40 determines whether or not the normal defrosting condition is satisfied. If the determination is NO, the process proceeds to step 102, and if YES, the process proceeds to step # 109.

When the process proceeds to step # 109, the control unit 40 performs normal defrosting. Here, the circulation at the time of heating is switched to the circulation at the time of cooling, and the high-temperature and high-pressure refrigerant flows into the outdoor heat exchanger 14 so that the outdoor heat exchanger 14 is defrosted. After a predetermined time has elapsed, the normal defrosting is completed and the operation returns to the heating operation. The flow returns to step # 101.

In step # 102, the control unit 40 determines whether the preliminary defrosting condition is satisfied. If the determination is YES, the process proceeds to step # 103, and if NO, the process returns to step # 101.

In step # 102, the control unit 40 determines whether or not the frosting on the outdoor heat exchanger 14 has progressed until the qualifying conditions for the preliminary defrosting are satisfied (hereinafter referred to as “frosting determination” in this specification). Do. The frost formation determination is to determine that the outdoor heat exchanger 14 is slightly frosted, and can be performed according to various determination criteria described below.

The first criterion for determining frost formation is a change in the detected temperature of the temperature detector 21 attached to the outdoor heat exchanger 14. When the detected temperature of the temperature detector 21 becomes a predetermined value or less, the control unit 40 determines “frosting”.

The second criterion for determining frost formation is a change in the current of the outdoor fan 16. When frosting on the outdoor heat exchanger 14 proceeds, the ventilation resistance of the outdoor heat exchanger 14 increases, and the current flowing through the outdoor blower 16 changes. When the current of the outdoor blower 16 changes by a predetermined value or more, the control unit 40 determines “frosting”.

The third criterion for determining frost formation is the air volume of the airflow passing through the outdoor heat exchanger 14. For this purpose, an air flow meter (not shown) is arranged in the airflow passing through the outdoor heat exchanger 14. When frosting on the outdoor heat exchanger 14 proceeds, the ventilation resistance of the outdoor heat exchanger 14 increases, and the amount of air passing through the outdoor heat exchanger 14 decreases. When the air volume decreases by a predetermined value or more, the control unit 40 determines “frosting”.

The fourth criterion for determining frost formation is time. A first preliminary defrosting operation or a second preliminary defrosting operation, which will be described later, has been executed for a predetermined time since the heating operation has been started for a predetermined time or since the previous first preliminary defrosting operation or the second preliminary defrosting operation. If not, the control unit 40 determines “frosting”.

If the control part 40 performs frost determination, it will progress to step # 103. In step # 103, the control unit 40 determines the outside air temperature. That is, it is determined whether the outside air temperature is higher or lower than a predetermined temperature (for example, + 2 ° C.). Thereafter, the process proceeds to step # 104. Preliminary defrosting is started from here.

In step # 104, the control unit 40 changes the opening degree of the expansion valve 15. When the outside air temperature measured in step # 103 is equal to or higher than the predetermined temperature, the control unit 40 performs a first preliminary defrosting operation for reducing the opening degree of the expansion valve 15. If the outside air temperature measured in step # 103 is less than the predetermined temperature, the control unit 40 performs a second preliminary defrosting operation for increasing the opening degree of the expansion valve 15.

In the first preliminary defrosting operation, it is difficult for the refrigerant to flow by reducing the opening degree of the expansion valve 15, and in that state, an air flow having a temperature equal to or higher than a predetermined temperature passes through the outdoor heat exchanger 14, The frost adhering to the outdoor heat exchanger 14 is melted. This first defrosting operation is suitable when the outside air temperature is high.

When the outside air temperature measured in step # 103 is lower than the predetermined temperature, the control unit 40 executes a second preliminary defrosting operation for increasing the opening degree of the expansion valve 15. As the opening degree of the expansion valve 15 increases, a large amount of the refrigerant that has passed through the indoor heat exchanger 32 flows through the outdoor heat exchanger 14, and the heat of the refrigerant is transferred to the outdoor heat exchanger 14. The attached frost melts. This second defrosting operation is suitable when the outside air temperature is low.

The effects of the first preliminary defrosting operation and the second preliminary defrosting operation will be described with reference to FIGS. As an example, the results of an experiment conducted using a separate air conditioner having an average heating capacity of about 2400 W under conditions of an outdoor dry bulb temperature of 2 ° C., an outdoor wet bulb temperature of 1 ° C., and an indoor dry bulb temperature of 20 ° C. are shown in FIG. Shown in

In the table of FIG. 9, “normal defrosting” is a heating operation mode in which only normal defrosting is performed without performing preliminary defrosting operation. “Expansion valve fully closed” is a heating operation mode with a first preliminary defrosting operation, and is a heating operation mode in which the opening degree of the expansion valve is “fully closed”. “Expansion valve fully open” is a heating operation mode with a second preliminary defrosting operation, and is a heating operation mode in which the opening of the expansion valve is “fully open”. "Average heating capacity" is a numerical value obtained by dividing the heating capacity in the time (1 cycle) from the start of heating operation to the end of normal defrosting performed immediately after the heating operation by the time of the 1 cycle, The unit is kW or W. The “heating time” is the time of the one cycle.

The table of FIG. 9 summarizes the results of the three experiments, “normal defrosting”, “expansion valve fully closed”, and “expansion valve fully open”. Here, “frosting” was determined using time as a criterion. In the “normal defrosting” experiment, the average heating capacity was 2384, and the heating time was 32 minutes and 35 seconds. In the experiment of “expansion valve fully closed”, the first preliminary defrosting operation was executed a total of 7 times, the average heating capacity was 2497, and the heating time was 58 minutes and 50 seconds. In the experiment of “expansion valve fully open”, the second preliminary defrosting operation was executed four times in total, the average heating capacity was 2528, and the heating time was 55 minutes and 50 seconds.

Fig. 10 is a graph of the average heating capacity data in the table of Fig. 9. Similarly, FIG. 11 is a graph of heating time data in the table of FIG.

From FIG. 9 to FIG. 11, by setting the normal defrosting to be performed after the first preliminary defrosting operation or the second preliminary defrosting operation is performed a predetermined number of times, the average heating capacity is improved and the heating is performed. It can be seen that the time will be longer.

It is desirable that the expansion valve change time for reducing or increasing the opening of the expansion valve 15 is not long. As shown in FIG. 12, the preliminary defrosting operation for reducing the opening degree of the expansion valve brings about an effect of improving the average heating capacity if the expansion valve change time is up to about 50 seconds. Is small. Therefore, the length of the first preliminary defrosting operation is up to about 50 seconds. Further, the preliminary defrosting operation for increasing the opening degree of the expansion valve brings about an effect of improving the average heating capacity if the expansion valve change time is up to about 30 seconds, but there is no effect of improving the average heating capacity in the time longer than that. Therefore, the length of the second preliminary defrosting operation is preferably up to about 30 seconds. Considering that there is variation depending on the frosting condition and the type of heat exchanger, the execution time of the preliminary defrosting operation including the first preliminary defrosting operation and the second preliminary defrosting operation is 1 minute or less per time It is desirable that

しない Do not increase the number of preliminary defrost operations. As shown in FIG. 13 (valve fully closed), the average heating capacity is improved until the first preliminary defrosting operation is repeated six times. Therefore, the number of times that is not much different from this is set as the number of repetitions of the first preliminary defrosting operation. The number of repetitions of the second preliminary defrosting operation is set similarly to the number of repetitions of the first preliminary defrosting operation.

Referring back to the flowchart of FIG. The process proceeds from step # 104 to step # 105. In step # 105, the control unit 40 changes the rotational speed of the outdoor blower 16.

As shown in the graph of FIG. 14 (valve fully opened), the average heating capacity generally improves as the rotational speed of the outdoor blower 16 increases. Therefore, in step # 105, the rotational speed of the outdoor blower 16 is increased. The rotational speed of the outdoor blower 16 is increased only during the execution of the first defrosting operation or the second defrosting operation.

The process proceeds from step # 105 to step 106. In step # 106, the control unit 40 changes the rotational speed of the compressor 12. In the first preliminary defrosting operation, the rotational speed of the compressor 12 is decreased in order to reduce the flow of the refrigerant. In the second preliminary defrosting operation, in order to flow a large amount of heat-bearing refrigerant to the outdoor heat exchanger 14, the rotational speed of the compressor 12 is increased. The rotation speed of the compressor 12 is changed only during execution of the first defrosting operation or the second defrosting operation.

In step # 107, the control unit 40 checks whether the time set as the time for the first preliminary defrosting operation or the time set as the time for the second preliminary defrosting operation has elapsed. When the time set as the time of the first preliminary defrosting operation or the time set as the time of the second preliminary defrosting operation has elapsed, the process proceeds to step # 108.

In step # 108, the control unit 40 restores the rotational speeds of the outdoor blower 16 and the compressor 12. Further, the opening degree of the expansion valve 15 is returned to the vicinity of the original opening degree. The reason why the width of the vicinity of the original opening is given is that the frost is applied to the outdoor heat exchanger 14 before and after the preliminary defrosting. Because it is different. Therefore, the opening degree of the expansion valve 15 is returned so that the optimum opening degree after the preliminary defrosting is obtained. After step # 108, the process returns to step # 101.

Preliminary defrosting enables the outdoor heat exchanger 14 to be kept in a state of good heat exchange efficiency with little frost formation for a long time, and thus also brings about an energy saving effect.

FIG. 15 shows the results of an experiment in which it is determined whether the effect of the frost control on the outdoor heat exchanger by performing preliminary defrosting during the heating operation, that is, the effect of the difficult frost control varies depending on the type of the heat exchanger. And the graph of FIG. In the tables and graphs, “F & T” indicates a fin-and-tube heat exchanger, and “AL-PFC” indicates an all-aluminum side-flow parallel-flow heat exchanger.

As a result of the experiment, the average heating capacity did not increase so much in the fin-and-tube heat exchanger even when the hard frost control was performed. On the other hand, in the all-aluminum side flow parallel flow type heat exchanger, the average heating capacity was improved by 6% by the hard frost control. From this, it can be seen that the effect of the present invention is particularly great when a parallel flow heat exchanger having high heat exchange efficiency is used as the outdoor heat exchanger. This is due to the following reason. That is, the parallel flow type heat exchanger has a high fin efficiency, so that the surface temperature of the fin approaches the refrigerant temperature and becomes a lower temperature. As a result, the temperature difference between the outdoor atmosphere and the surface temperature of the outdoor heat exchanger increases, and frost formation is likely to occur in the outdoor heat exchanger. On the other hand, when fin efficiency is high, when melting frost, it becomes easy to melt | dissolve conversely. Moreover, since the parallel flow type heat exchanger has a narrow gap between the fins, it is easy to prevent ventilation due to frost, and the effect of suppressing the obstruction of ventilation by the difficult frost control can be enjoyed more than other types of heat exchangers.

The air conditioner targeted by the present invention is not limited to one using a parallel flow heat exchanger or a fin-and-tube heat exchanger as a heat exchanger. The present invention can also be applied to a defrosting of an outdoor unit of a radiation type air conditioner, that is, an air conditioner in which the indoor unit circulates indoor air by natural convection without using a blower.

As mentioned above, although the embodiment of the present invention has been described, the scope of the present invention is not limited to this. Various modifications can be made without departing from the spirit of the invention.

The present invention is widely applicable to heat pump type air conditioners.

DESCRIPTION OF SYMBOLS 1 Air conditioner 10 Outdoor unit 11 Case 12 Compressor 13 Switching valve 14 Outdoor heat exchanger 15 Expansion valve 16

Outdoor blower

17, 18 Refrigerant piping 21 Temperature detector 30 Indoor unit 31 Case 32 Indoor side heat exchanger 33 Indoor Blower 40 Control Unit

Claims

An air conditioner comprising the following:
An outdoor heat exchanger,
An indoor heat exchanger,
An expansion valve disposed between the outdoor heat exchanger and the indoor heat exchanger;
A compressor for circulating a refrigerant in a refrigeration cycle including the outdoor heat exchanger, the indoor heat exchanger, and the expansion valve;
Refrigerant circulation by the compressor, cooling-time circulation in which refrigerant discharged from the compressor first enters the outdoor heat exchanger, and refrigerant discharged from the compressor first in the indoor heat exchanger A switching valve that switches between entering heating circulation,
A controller of the air conditioner,
The controller increases a first preliminary defrosting operation for reducing the opening degree of the expansion valve or an opening degree of the expansion valve at a stage before the defrosting step of the outdoor heat exchanger during the heating operation. The second preliminary defrosting operation can be performed.
The air conditioner of claim 1, wherein the air conditioner is configured as follows:
The said control part performs the defrost process of the said outdoor heat exchanger, after performing the said 1st preliminary | backup defrost operation or the said 2nd preliminary | backup defrost operation predetermined times.
The air conditioner according to claim 1 or 2, wherein the air conditioner is configured as follows:
The control unit executes the first preliminary defrosting operation when the outside air temperature is equal to or higher than a predetermined temperature, and executes the second preliminary defrosting operation when the outside air temperature is lower than the predetermined temperature.
The air conditioner according to any one of claims 1 to 3, wherein the air conditioner is configured as follows:
In the defrosting step, the control unit switches the heating circulation to the cooling circulation.
The air conditioner according to any one of claims 1 to 4, which is configured as follows:
The said control part performs the said 1st preliminary | backup defrost operation and the said 2nd preliminary | backup defrost operation by the frost formation determination with respect to the said outdoor heat exchanger.
6. The air conditioner according to claim 5, which is configured as follows:
The control unit performs the frost determination by measuring a change in temperature detected by a temperature detector attached to the outdoor heat exchanger, a change in current of an outdoor fan attached to the outdoor heat exchanger, or the outdoor side. This is performed based on the measurement result of the air flow meter that measures the air volume of the airflow passing through the heat exchanger, or the length of time during which the first preliminary defrosting operation or the second preliminary defrosting operation is not executed.