JP5997060B2 - Air conditioner - Google Patents

Description

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

  Air conditioners for homes adopt a heat pump system, and the main type is a separate type that is divided into an outdoor unit and an indoor unit. When performing heating operation with such an air conditioner, avoid the problem of frost formation on the outdoor heat exchanger as a result of the indoor heat exchanger becoming hot while the outdoor heat exchanger becomes cold. I can't. 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, a connection portion between the outdoor heat exchanger and the pressure reducing device and a discharge portion of the compressor are connected by a refrigerant path having an opening / closing valve, and the opening / closing valve is on the high pressure side during heating. It opens when the pressure in the refrigerant path 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 device described in Patent Document 2, the defrosting is performed by opening the valve opening of the decompression device at the time of defrosting, or by fully opening the valve opening of the decompression device and stopping the forced ventilation of the condenser / evaporator and operating the compressor. I do.

  Even in the same separate type air conditioner, there is a type in which the indoor unit is configured as a radiant 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 Laid-Open No. 60-50352 Japanese Patent Laid-Open No. 10-205802

  Although the defrosting process of the outdoor unit during the heating operation is inevitable, it temporarily inconveniences the user due to the temporary interruption of the 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.

  An air conditioner according to the present invention includes an outdoor heat exchanger, an indoor heat exchanger, an expansion valve disposed between the outdoor heat exchanger and the indoor heat exchanger, and the outdoor heat. A compressor that circulates a refrigerant in a refrigeration cycle including the exchanger, the indoor heat exchanger, and the expansion valve; and the refrigerant that is discharged from the compressor first in the refrigerant circulation by the compressor. The air conditioner control unit includes a switching valve that switches between cooling circulation entering the heat exchanger and heating circulation that the refrigerant discharged from the compressor first enters the indoor heat exchanger. During the operation, the first preliminary defrosting operation for reducing the opening degree of the expansion valve or the second preliminary defrosting operation for increasing the opening degree of the expansion valve in the stage before the defrosting step of the outdoor heat exchanger. Is feasible.

  In the air conditioner having the above configuration, it is preferable that after the first preliminary defrosting operation or the second preliminary defrosting operation is executed a predetermined number of times, the defrosting process of the outdoor heat exchanger is entered.

  In the air conditioner having the above-described configuration, the first preliminary defrosting operation is performed when the outside air temperature is equal to or higher than the predetermined temperature, and the second preliminary defrosting operation is performed when the outside air temperature is lower than the predetermined temperature. preferable.

  In the air conditioner configured as described above, it is preferable that the heating circulation is switched to the cooling circulation in the defrosting step.

  In the air conditioner having the above-described configuration, it is preferable that the first preliminary defrosting operation and the second preliminary defrosting operation are executed in response to a frost determination on the outdoor heat exchanger.

  In the air conditioner having the above configuration, the frost determination is performed by changing a temperature detected by a temperature detector attached to the outdoor heat exchanger, or changing a current of an outdoor fan attached to the outdoor heat exchanger, or It is made based on the measurement result of the 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 is not executed. It is preferable.

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

  In the air conditioner having the above configuration, it is preferable that the rotation speed of the compressor is decreased during the execution of the first preliminary defrosting operation, and the rotation speed of the compressor is increased during the execution of the second preliminary defrosting operation.

  In the air conditioner having the above configuration, it is preferable that the execution time of the preliminary defrosting operation is 1 minute or less per time.

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

  According to the present invention, by performing preliminary defrosting in the previous stage of the normal defrosting process, it is possible to delay the time when the normal defrosting is necessary. Can continue.

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.

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

  The basic structure of a side flow type parallel flow heat exchanger is shown in FIG. 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, and the flat tubes 53 are arranged at a predetermined pitch in the vertical direction. Since the heat exchanger 50 is installed at various angles according to design requirements at the stage of actually mounting on equipment, the “vertical direction” and “horizontal direction” in this specification should not be interpreted strictly. It should be understood as a mere measure of direction.

  The flat tube 53 is an elongated molded product obtained by extruding a metal, and as shown in FIG. 4, a refrigerant passage 54 through which a refrigerant flows is formed. 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 cross-sectional area are arranged in the left-right direction in FIG. 4, and therefore the vertical cross section of the flat tube 53 has a harmonica shape. Each refrigerant passage 54 communicates with the header pipes 51 and 52.

  Fins 55 are 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, 52, the flat tubes 53, the fins 55, and the side plates 56 are all made of a metal having good heat conductivity such as aluminum. The flat tubes 53 are for the header pipes 51, 52 and the fins 55 are for the flat tubes 53. 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 one partition portion 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, and a flat tube group consisting of 12 flat tubes 53 is 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 inside 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 4 of the 24 flat tubes 53 in total is connected to the section S3, a flat tube group consisting of 15 flat tubes 53 is connected to the section S4, and 5 pieces are connected to the section S5. A flat tube group consisting of the flat tubes 53 is connected.

  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 inlet / outlet pipe 57 is connected to the section 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 section S1 is turned back there, and travels to the section S4 through the eight flat tubes 53 that connect the sections S1 and S4. The flat tube group formed by the eight flat tubes 53 constitutes the refrigerant path B.

  The refrigerant that has entered the section S4 is turned back there, and travels to the section S2 through the seven flat tubes 53 that connect the sections S4 and 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 turns 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 compartment 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 <b> 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.

  A schematic configuration of a separate air conditioner 1 using the heat exchanger 50 as a component of a heat pump cycle is shown in FIG. 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. 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.

  In the refrigerant pipe inside the outdoor unit 10, a two-way valve 19 is provided in the refrigerant pipe connected to the refrigerant pipe 17, and 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 in a housing 31 formed of synthetic resin parts. The indoor heat exchanger 32 is a combination of three heat exchangers 32 </ b> A, 32 </ b> B, and 32 </ b> C like a roof that covers the indoor blower 33. Any or all of the heat exchangers 32 </ b> A, 32 </ b> B, and 32 </ b> C can be configured by the heat exchanger 50. The indoor blower 33 is a combination of a motor and a cross flow fan.

  In order to control the operation of the air conditioner 1, it is indispensable to know the temperature of each place. 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, and a temperature detector 22 is disposed in the discharge pipe 12 a serving as the discharge unit of the compressor 12, and the suction serving as the suction unit of the compressor 12. A temperature detector 23 is disposed in the pipe 12 b, a temperature detector 24 is disposed in the refrigerant pipe between the expansion valve 15 and the two-way valve 19, and a temperature detector for measuring the outside air temperature at a predetermined location inside the housing 11. 25 is arranged. 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 fan 16, and the indoor fan 33. The control unit 40 receives output signals of the detected temperatures from the temperature detectors 21 to 25 and the temperature detector 34. While referring to the output signals from the temperature detectors 21 to 25 and the temperature detector 34, the control unit 40 issues an operation command to the compressor 12, the outdoor fan 16, and the indoor fan 33, and the expansion valve 13 and the expansion valve 13 are expanded. A command for switching the state is issued to the valve 15.

  FIG. 1 shows a state in which 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 air flow generated by the outdoor blower 16 promotes heat radiation from the outdoor heat exchanger 14, and the air flow generated by the indoor blower 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 air flow generated by the outdoor blower 33 promotes heat dissipation from the indoor heat exchanger 33, and the air flow generated by the outdoor blower 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. The conventional control method shown in FIG. 6 increases the heating capacity after the start of the heating operation and maintains a high heating capacity until a certain point in time, but stops the heating operation because the heating capacity rapidly decreases due to frost formation at a certain point in time. Then, after entering the defrosting process, after completing the defrosting process, 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. In the meantime, the user had to put up with the room temperature going down.

  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, normal defrosting is performed. 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 frost formation on the outdoor heat exchanger 14 has progressed until the qualifying conditions for 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 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, is executed for a predetermined time since the heating operation has not been performed 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 opening degree of the expansion valve 15 is changed. When the outside air temperature measured in step # 103 is equal to or higher than the predetermined temperature, the first preliminary defrosting operation for reducing the opening degree of the expansion valve 15 is executed. If the outside air temperature measured in step # 103 is lower than the predetermined temperature, the second preliminary defrosting operation for increasing the opening degree of the expansion valve 15 is executed.

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 preliminary 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 second preliminary defrosting operation for increasing the opening degree of the expansion valve 15 is executed. 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 preliminary 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 with an average heating capacity of about 2400 W under the 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”. The “average heating capacity” is a numerical value obtained by dividing the heating capacity in the time (1 cycle) from the start of the heating operation to the end of the normal defrost 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 three experimental results of “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. 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 time is also set. It turns out that it becomes long.

  It is desirable that the expansion valve change time for reducing or increasing the opening degree 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

  Do not unnecessarily increase the number of preliminary defrosting 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 defrost 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.

  Returning to the flowchart of FIG. The process proceeds from step # 104 to step # 105. In step # 105, the rotational speed of the outdoor blower 16 is changed.

As can be seen from the graph of FIG. 14 (valve fully open), 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 preliminary defrosting operation or the second preliminary defrosting operation.

The process proceeds from step # 105 to step 106. In step # 106, the rotation speed of the compressor 12 is changed. 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 preliminary defrosting operation or the second preliminary defrosting operation.

  In step # 107, the control unit 40 checks whether or not 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. 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 of the expansion valve 15 is returned to the vicinity of the original opening. 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 can keep the outdoor heat exchanger 14 in a state of good heat exchange efficiency with little frost formation for a long period of time, which 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 if difficult 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 because the parallel flow type heat exchanger has a higher fin efficiency, so that the surface temperature of the fins approaches the refrigerant temperature, resulting in 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 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.

  Although the embodiments of the present invention have been described above, the scope of the present invention is not limited to these embodiments, and 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 (5)

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, and the indoor heat exchanger And a compressor that circulates a refrigerant in a refrigeration cycle including the expansion valve, and a refrigerant circulation by the compressor, and a cooling circulation that the refrigerant discharged from the compressor first enters the outdoor heat exchanger. In the air conditioner provided with a switching valve for switching between the refrigerant discharged from the compressor and the circulation at the time of heating that first enters the indoor heat exchanger,
The controller of the air conditioner performs a first preliminary defrosting operation for reducing the opening degree of the expansion valve or opening the expansion valve at the stage before the defrosting process of the outdoor heat exchanger during the heating operation. executable der the second preliminary defrosting operation to increase the degree is,
The air conditioner is characterized in that the first preliminary defrosting operation is executed when the outside air temperature is equal to or higher than a predetermined temperature, and the second preliminary defrosting operation is executed when the outside air temperature is lower than the predetermined temperature .   2. The air conditioner according to claim 1, wherein after the first preliminary defrosting operation or the second preliminary defrosting operation is executed a predetermined number of times, the outdoor heat exchanger enters a defrosting step. The air conditioner according to claim 1 or 2 , wherein in the defrosting step, the heating circulation is switched to the cooling circulation. The air according to any one of claims 1 to 3 , wherein the first preliminary defrosting operation and the second preliminary defrosting operation are executed in response to a frost determination on the outdoor heat exchanger. Harmony machine. The frosting determination is 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 a passage through the outdoor heat exchanger. claim 4, characterized in that measurement results, or the first preliminary defrosting operation or the second preliminary defrosting operation airflow meter for measuring the air volume of the air stream is made based on the length of time that was not executed to Air conditioner as described in.

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