JP2008025901A - Air conditioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an air conditioner having a simple refrigerant circuit constitution and not inhibiting initial rise of heating after defrosting. <P>SOLUTION: Four-way valves 31A, 31B of outdoor units 3A, 3B are switched so that one of the outdoor units 3A is functioned as a condenser and the other outdoor unit 3B is functioned as an evaporator when one of the outdoor units 3A needs defrosting, a compressor 30B of the other outdoor unit 3B is operated with an operational frequency higher than that of a compressor 30A of the outdoor unit 3A to be defrosted, and a refrigerant is circulated between the plural outdoor units 3A, 3B. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an air conditioner in which a plurality of outdoor units are connected in parallel to an inter-unit pipe extending from an indoor unit, and more particularly to a defrosting technique for an outdoor unit.

  In general, multiple indoor units are arranged in parallel, and multiple outdoor units containing compressors, four-way valves, outdoor heat exchangers, etc. are connected in parallel to the inter-unit piping connected to each indoor unit. An air conditioner (so-called multi-type air conditioner) is known (see, for example, Patent Document 1). This type of multi-type air conditioning apparatus has the advantage that the apparatus can be made into a large capacity system.

By the way, when the air conditioner is in a heating operation, frost may be formed on the outdoor heat exchanger of the outdoor unit. In order to reduce the operating efficiency of the air conditioner when the outdoor heat exchanger is frosted, conventionally, the outdoor heat exchanger is defrosted by a defrosting technique such as reverse cycle defrosting or hot gas defrosting. . Reverse cycle defrosting is a technique for defrosting the outdoor heat exchanger by switching the air conditioner to cooling operation so that the indoor unit functions as an evaporator and the outdoor unit functions as a condenser. In addition, hot gas defrosting leads the refrigerant discharged from the compressor to the outdoor heat exchanger and the indoor heat exchanger, defrosts the outdoor heat exchanger, and causes the indoor heat exchanger to function as a condenser. It is.
Japanese Patent Application Laid-Open No. 06-313653

However, in the reverse cycle defrosting, since the indoor heat exchanger functions as an evaporator and enters a cooling state, the inter-unit piping and the indoor unit are cooled, and the inter-unit piping is caused by thermal stress during defrosting. There was a problem that noise was generated, and that the start-up of the heating after defrosting worsened.
Further, in the hot gas defrosting, there is no heat absorption source in the refrigerant circuit, and heat is not given to the refrigerant from outside except for the refrigerant compression by the compressor, so that the defrosting takes time. is there. Furthermore, in hot gas defrosting, it is necessary to provide hot gas piping for guiding the refrigerant discharged from the compressor to the outdoor heat exchanger, which not only complicates the configuration of the refrigerant circuit but also increases the cost. There is a problem of becoming higher.

  The present invention has been made in view of the above-described circumstances, and an object thereof is to provide an air conditioner that has a simple refrigerant circuit configuration and does not hinder the rise of heating after defrosting.

  To achieve the above object, the present invention comprises an outdoor unit having a compressor, a four-way valve, an outdoor heat exchanger, and an outdoor expansion valve, and an indoor unit having an indoor heat exchanger and an indoor expansion valve. In an air conditioner in which a plurality of the outdoor units are connected in parallel to an inter-unit pipe extending from the unit, when one outdoor unit reaches a defrosting state, the one outdoor unit functions as a condenser. In addition, the four-way valve of each outdoor unit is switched so that the other outdoor units function as an evaporator, and the compressor of the other outdoor unit is operated at a higher operating frequency than the compressor of the one outdoor unit. Then, the refrigerant is circulated between the plurality of outdoor units.

  In this case, a part of the refrigerant condensed in the outdoor heat exchanger of the one outdoor unit is returned to the suction side of the compressor of the one outdoor unit and discharged from the compressor of the other outdoor unit. It is good also as a structure merged with the refrigerant.

  Further, when the defrosting of the one outdoor unit is completed, the four-way valve may be switched, and the defrosting of the other outdoor unit may be performed following the defrosting of the one outdoor unit. Further, the indoor expansion valve of the indoor unit may be fully closed during the defrosting operation.

  According to the present invention, the heating operation after defrosting can be started earlier than before with a simple refrigerant circuit configuration.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a refrigerant circuit diagram of an air conditioner 1 according to an embodiment of the present invention. As shown in this figure, the air conditioner 1 includes a plurality (two in the present embodiment) of indoor units 2A and 2B, and a plurality of (two in the present embodiment) outdoor units 3A and 3B. The indoor units 2A and 2B and the outdoor units 3A and 3B are connected by an inter-unit pipe 4. The inter-unit pipe 4 is composed of a gas pipe 5 and a liquid pipe 6. Each of the indoor units 2A and 2B is connected to the inter-unit pipe 4 in parallel with each other, and each of the outdoor units 3A and 3B is also connected. The inter-unit pipes 4 are connected in parallel to each other. In the following description, each of the indoor units 2A and 2B is referred to as an indoor unit 2 when it is not necessary to distinguish between them. Similarly, when it is not necessary to distinguish each of the outdoor units 3 </ b> A and 3 </ b> B, they are expressed as the outdoor unit 3.

  Each of the indoor units 2 includes an indoor heat exchanger 20, an indoor expansion valve 21, and an indoor fan 22. The indoor heat exchanger 20 is interposed between the gas pipe 5 and the liquid pipe 6, and the indoor expansion valve 21 is provided between the indoor heat exchanger 20 and the liquid pipe 6. The indoor fan (blower) 22 is provided in the vicinity of the indoor heat exchanger 20, and exchanges heat between the indoor air and the indoor heat exchanger 20 to blow conditioned air into the room. In addition to this, the indoor unit 2 is provided with a temperature sensor for detecting the indoor air temperature and an indoor control device (both not shown) for controlling each part of the indoor unit 2.

The outdoor unit 3A includes a compressor 30A, a four-way valve 31A, an outdoor heat exchanger 32A, an outdoor expansion valve 33A, an outdoor fan 34A, and an auxiliary cooler 35A. The auxiliary cooler 35A improves the cooling capacity in the indoor unit 2 by supercooling the liquid refrigerant flowing through the refrigerant pipe 36A connecting the outdoor expansion valve 33A and the liquid pipe 6 during the cooling operation. . Specifically, the auxiliary cooler 35A is formed of a so-called double pipe heat exchanger in which an inner pipe and an outer pipe are constituted by a double pipe, and the refrigerant pipe 36A is connected to the inner pipe. The outer pipe is connected to a branch pipe 38A through which the refrigerant branched from the refrigerant pipe 36A passes through the auxiliary cooling expansion valve 37A. The branch pipe 38A is connected to the suction side of the compressor 30A via a refrigerant pipe 39A connected to the outer pipe of the auxiliary cooler 35A, and the refrigerant passing through the branch pipe 38A and the refrigerant pipe 39A is compressed by the compressor 30A. It is designed to be returned to the inlet.
This compressor 30A is a variable compressor (inverter compressor) with variable capacity. A temperature sensor (not shown) is disposed in the outdoor heat exchanger 32A, and the temperature of the outdoor heat exchanger 32A is output to the control device 100. The control device 100 executes various controls such as switching of the four-way valve 31A accompanying switching between cooling operation and heating operation, operation frequency control of the compressor 30A, or opening degree adjustment of the outdoor expansion valve 33A. Furthermore, in this Embodiment, a defrost start state is judged based on the temperature of the outdoor heat exchanger 32A, and the defrost process mentioned later is started at the time of defrost. In this embodiment, since the outdoor unit 3B has substantially the same configuration as the outdoor unit 3A, the same reference numerals are given and description thereof is omitted.

Under the above-described configuration, during the cooling operation, as shown in FIG. 1, the control device 100 causes the high-temperature and high-pressure gas refrigerant discharged from the compressors 30A and 30B to flow toward the indoor units 2A and 2B. The four-way valves 31A and 31B of the units 3A and 3B are switched to the positions for the cooling operation. Thereby, the outdoor heat exchangers 32A and 32B of the outdoor units 3A and 3B function as a condenser, and the indoor heat exchanger 20 of the indoor unit 2 functions as an evaporator, thereby cooling the room.
On the other hand, at the time of heating operation, as shown in FIG. 2, the control device 100 sets the outdoor unit so that the high-temperature and high-pressure gas refrigerant discharged from the compressors 30A and 30B flows toward each of the indoor units 2A and 2B. The four-way valves 31A and 31B of 3A and 3B are switched to the positions during the heating operation. Thereby, contrary to the cooling operation, the outdoor heat exchangers 32A and 32B of the outdoor units 3A and 3B function as an evaporator, and the indoor heat exchanger 20 of the indoor unit 2 functions as a condenser. The heating is done.

Next, the operation during the defrosting operation will be described.
As described above, the control device 100 determines the defrosting start state based on the detected temperature of the outdoor heat exchanger 32 during the heating operation. And the control apparatus 100 starts a defrost process, when it determines with the outdoor heat exchanger 32 having frosted. Hereinafter, the defrosting process will be described in detail with reference to FIGS. 3 and 4. In the following description, the outdoor unit 3A among the two outdoor units 3A and 3B will be described as being a unit to be defrosted (one outdoor unit).

FIG. 3 is a flowchart showing the defrosting process, and FIG. 4 is a refrigerant circuit diagram during the defrosting process. As shown in FIG. 3, in the control device 100, first, the outdoor heat exchanger 32A of one outdoor unit 3A to be defrosted functions as a condenser, and the outdoor heat exchanger 32B of another outdoor unit 3B The four-way valves 31A and 31B of the outdoor units 3A and 3B are switched so as to function as an evaporator (heat absorption source) (step S1).
Specifically, the control device 100 intermittently or continuously monitors the temperatures of the outdoor heat exchangers 32A and 32B of the outdoor units 3A and 3B during the heating operation, and this temperature is below a predetermined temperature. When the outdoor unit 3 which has fallen exists, the outdoor unit 3 is targeted for defrosting (in this embodiment, the outdoor unit 3A), and as shown in FIG. 4, the outdoor heat exchanger 32A of the outdoor unit 3A. So as to function as a condenser, the four-way valve 31A of the outdoor unit 3A is switched to the position during the cooling operation. During the heating operation, since the outdoor heat exchanger 32B of the other outdoor unit 3B originally functions as an evaporator, the four-way valve 31B of the other outdoor unit 3B is held at the position during the heating operation. Further, the control device 100 fully opens the outdoor expansion valve 33A of the outdoor unit 3A, and adjusts the opening degree so that the degree of superheat of the refrigerant sucked into the compressor 30A by the auxiliary cooling expansion valve 37A becomes substantially constant. Further, the control device 100 fully closes the auxiliary cooling expansion valve 37B, and adjusts the opening degree of the outdoor expansion valve 33B so that the degree of superheat of the refrigerant at the outlet of the outdoor heat exchanger 32B becomes substantially constant.

  Next, the control device 100 drives the compressors 30A and 30B of the outdoor units 3A and 3B so that the refrigerant circulates between the outdoor units 3A and 3B (step S2). As a result, as shown in FIG. 4, the gas refrigerant compressed by the compressor 30B of the outdoor unit 3B is sucked into the compressor 30A of the outdoor unit 3A via the gas pipe 5. Then, the refrigerant is further compressed by the compressor 30A (so-called two-stage compression), becomes a high-temperature / high-pressure gas refrigerant, and is led to the outdoor heat exchanger 32A of the outdoor unit 3A. The outdoor heat exchanger 32A is heated and defrosted by the heat energy of the high-temperature and high-pressure gas refrigerant.

  The liquid refrigerant condensed in the outdoor heat exchanger 32A of the outdoor unit 3A is auxiliary cooled in the auxiliary cooler 35A via the refrigerant pipe 36A and then transferred to the other outdoor unit 3B via the liquid pipe 6. be introduced. Then, the pressure is reduced by the outdoor expansion valve 33B of the other outdoor unit 3B and evaporated by the outdoor heat exchanger 32B, thereby becoming a low-temperature / low-pressure gas refrigerant, and again sucked into the compressor 30B of the other outdoor unit 3B. Compressed.

  In this configuration, as described above, the outdoor unit 3A includes the auxiliary cooler 35A, and the refrigerant supplied to the outer pipe of the auxiliary cooler 35A exchanges heat with the refrigerant flowing through the inner pipe of the auxiliary cooler 35A. Thus, the gas refrigerant is returned to the suction side of the compressor 30A through the refrigerant pipe 39A. According to this, the high-temperature / high-pressure gas refrigerant discharged from the compressor 30B of the other outdoor unit 3B and the low-temperature / low-pressure gas refrigerant used for auxiliary cooling in the auxiliary cooler 35A are sucked into the compressor 30A. As shown in FIG. 5, the gas refrigerant discharged from the compressor 30B is cooled, and the degree of superheat on the suction side (point C in the figure) of the compressor 30A is kept low. it can. For this reason, even when the refrigerant is compressed in two stages by the compressors 30A and 30B, the temperature of the gas refrigerant discharged from the compressor 30A does not rise abnormally, and between the outdoor units 3A and 3B. By circulating the refrigerant, the defrosting outdoor unit 3A can be efficiently defrosted.

  Further, in this configuration, in the control device 100, the operation frequency β of the compressor 30B of the other outdoor unit 3B is higher than the operation frequency α of the compressor 30A of the outdoor unit 3A to be defrosted (that is, β> α). In this way, the operating frequencies α and β of the compressors 30A and 30B are adjusted. Specifically, the operation frequency β of the compressor 30B is set to 80 Hz, and the operation frequency α of the compressor 30A is set to 20 Hz. According to this configuration, the operating frequency of the compressor 30B of the outdoor unit 3B corresponding to the low stage side in the two-stage compression is set higher than the operating frequency of the compressor 30A of the outdoor unit 3A corresponding to the high stage side. Therefore, the refrigerant is constantly supplied from the compressor 30B to the suction side of the compressor 30A, thereby preventing a shortage of refrigerant in the piping between the compressor 30B and the compressor 30A. The refrigerant can be efficiently circulated between the outdoor units 3A and 3B.

Thus, after starting defrosting with respect to outdoor unit 3A, control device 100 judges whether defrosting is completed based on the temperature of outdoor unit 3A (Step S3), and defrosting is completed. If not (step S3: NO), the processing step is returned to step S2, and the defrosting of the outdoor unit 3A is continued. On the other hand, if the defrosting is completed (step S3: YES), the defrosting process of the outdoor unit 3A is terminated, and subsequently, the defrosting process of the other outdoor unit 3B is started. Specifically, the four-way valve 31B of the outdoor unit 3B is switched to the position during the cooling operation so that the outdoor unit 3B functions as a condenser with the outdoor unit 3B as a defrost target. At the same time, the four-way valve 31A of the outdoor unit 3A is switched to the heating position so that the outdoor heat exchanger 32A of the outdoor unit 3A that has completed the defrosting process functions as an evaporator (step S4).
As described above, the compressors 30A and 30B of the outdoor units 3A and 3B are driven so that the refrigerant circulates between the outdoor units 3A and 3B, and the refrigerant is circulated between the outdoor units 3A and 3B. Then, defrosting of the outdoor heat exchanger 32B of the outdoor unit 3B is performed (step S5). In this case, contrary to the case of the outdoor unit 3A, the control device 100 uses the operating frequency β of the compressor 30B of the other outdoor unit 3B to be defrosted as the operating frequency α of the compressor 30A of the outdoor unit 3A. The operating frequency of each compressor 30A, 30B is adjusted so as to be higher. Specifically, the operation frequency α of the compressor 30A is set to 80 Hz, and the operation frequency β of the compressor 30B is set to 20 Hz.
Subsequently, the control device 100 determines whether or not the defrosting is completed based on the temperature of the outdoor unit 3B (step S6). If the defrosting is not completed (step S6: NO), the processing step is performed. It returns to step S5 and continues defrosting with respect to the outdoor unit 3B. On the other hand, if the defrosting is completed (step S6: YES), the defrosting process of the outdoor unit 3B is completed.

According to the defrosting operation of this configuration, in the outdoor unit functioning as an evaporator, heat can be absorbed from the air when the refrigerant evaporates, so defrosting compared to conventional reverse cycle defrosting and hot gas defrosting. Experiments have shown that the time can be shortened (about 1/2 or less). Therefore, as described above, even when the defrosting process for a plurality of outdoor units is performed twice, since the defrosting time per one time is about ½ or less, all the outdoor units are The total defrost time for defrosting all can be shortened rather than the conventional one.
In the defrosting operation according to this configuration, a plurality of outdoor units connected to each other are divided into an outdoor unit that functions as a condenser and an outdoor unit that functions as an evaporator. The defrosting of the outdoor unit that functions as a vessel is performed. In order to perform this defrosting efficiently, it is desirable that the capacity | capacitance of an evaporator and a condenser is substantially equal. Therefore, in this configuration, the outdoor units are divided into two groups in advance, and the number of outdoor units belonging to each group is substantially the same.
Here, when even one of the outdoor units is to be defrosted, all the outdoor units of the group to which this one belongs function as a condenser, and all the outdoor units of the remaining groups function as an evaporator. The defrosting operation is executed by switching the four-way valve of each outdoor unit so that it functions, and circulating the refrigerant between the outdoor units.

  In this configuration, in step S2, the indoor expansion valves 21 of the indoor units 2A and 2B are fully closed to prevent refrigerant from flowing into the indoor unit 2 during the defrosting operation. Further, in the present embodiment, in step S2, the outdoor expansion valve 33 of the outdoor unit 3A that functions as a condenser is fully opened, and the opening degree of the outdoor expansion valve 33B of another outdoor unit 3B that functions as an evaporator. Is controlled so that the degree of superheat of the evaporator outlet is constant. Thus, by controlling the opening degree of the outdoor expansion valve 33B of the outdoor unit 3B on the evaporator side, the degree of superheat at the outlet of the evaporator is maintained, and liquid return to the compressor 30B is prevented.

  As described above, according to this embodiment, during the defrosting operation, one outdoor unit 3A functions as a condenser, and the other outdoor unit 3B functions as an evaporator so that each outdoor unit has a four-way valve. 31A and 31B are switched, the refrigerant is circulated between the outdoor units 3A and 3B, and the outdoor heat exchanger 32A of the outdoor unit 3A that functions as a condenser is defrosted.

  Thereby, during the defrosting operation, the indoor unit 2 does not need to be in a cooling state, and the indoor unit 2 and the inter-unit piping 4 are not cooled, so that the startup performance during the heating operation after the defrosting is good. Further, it is possible to prevent a situation in which noise is generated in the inter-unit piping 4 due to thermal stress during the defrosting operation.

  Further, according to the present embodiment, at the time of defrosting operation, it is only necessary to switch the four-way valves 31A, 31B of the outdoor units 3A, 3B, and there is no need to make a change such as newly providing a pipe in the refrigerant circuit. Any outdoor unit 3A, 3B can be defrosted with a simple refrigerant circuit without complicating the refrigerant circuit configuration.

  Further, according to the present embodiment, since the outdoor unit 3B other than the outdoor unit 3A to be defrosted is configured to function as an evaporator serving as a heat absorption source, the time required for the defrosting of the outdoor unit 3A is reversed to the conventional one. It can be shortened compared with cycle defrosting and hot gas defrosting. Specifically, it has been proved by experiments and the like that the defrosting time per time according to this configuration is about ½ or less compared to reverse cycle defrosting or hot gas defrosting. Even when the defrosting process is performed in two steps, the process can be completed earlier than the conventional defrosting described above.

  Further, according to the present embodiment, the operating frequency of the compressor 30B of the outdoor unit 3B corresponding to the low stage side is set higher than the operating frequency of the compressor 30A of the outdoor unit 3A corresponding to the high stage side. The refrigerant is continuously supplied from the compressor 30B to the suction side of the compressor 30A, thereby preventing a refrigerant shortage from occurring in the piping between the compressor 30B and the compressor 30A. The refrigerant can be efficiently circulated between the outdoor units 3A and 3B, and thus the defrosting time can be shortened.

  Further, according to the present embodiment, a part of the refrigerant condensed in the outdoor heat exchanger 32A of the one outdoor unit 3A is returned to the suction side of the compressor 30A of the one outdoor unit 3A, and the other outdoor unit Since the refrigerant discharged from the 3B compressor 30B is merged, the superheat degree of the refrigerant on the suction side of the high-stage compressor 30A can be kept low, and even when two-stage compression is performed, The temperature of the gas refrigerant discharged from the stage-side compressor 30A does not rise abnormally, and the outdoor unit 3A can be efficiently defrosted.

  Moreover, according to this Embodiment, since it is set as the structure which makes the indoor expansion valve 21 of the indoor unit 2 fully closed at the time of a defrost operation, the flow of the refrigerant | coolant to the indoor unit 2 is prevented. Thereby, the inter-unit piping 4 and the indoor unit 2 are not cooled by the low-temperature and low-pressure gas refrigerant, and noise generation in the inter-unit piping 4 can be further suppressed.

  The above-described embodiment is merely an aspect of the present invention, and can be arbitrarily modified within the scope of the present invention. For example, in the air conditioning apparatus according to the present embodiment, the configuration includes the two outdoor units 3A and 3B, but the configuration may include three or more outdoor units.

It is a refrigerant circuit figure of the air harmony device concerning an embodiment of the invention. It is a refrigerant circuit figure at the time of the cooling operation of the air conditioning apparatus. It is a flowchart of a defrost process. It is a refrigerant circuit figure at the time of the defrost operation of an air conditioning apparatus. It is a ph diagram of the refrigerating cycle at the time of defrosting operation.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Air conditioning apparatus 2, 2A, 2B Indoor unit 3, 3A, 3B Outdoor unit 4 Inter-unit piping 20 Indoor heat exchanger 21 Indoor expansion valve 30A, 30B Compressor 31A, 31B Four-way valve 32A, 32B Outdoor heat exchanger 33A, 33B outdoor expansion valve 100 controller

Claims (4)

An outdoor unit having a compressor, a four-way valve, an outdoor heat exchanger and an outdoor expansion valve, and an indoor unit having an indoor heat exchanger and an indoor expansion valve, and a plurality of the outdoor units are provided in an inter-unit pipe extending from the indoor unit. In the air conditioner connected in parallel,
When one outdoor unit is in a defrosting state, the one outdoor unit functions as a condenser, and the other outdoor unit functions as an evaporator. The air conditioner is characterized in that the refrigerant is circulated between the plurality of outdoor units by switching and operating the compressor of the other outdoor unit at a higher operating frequency than the compressor of the one outdoor unit.   A part of the refrigerant condensed in the outdoor heat exchanger of the one outdoor unit is returned to the suction side of the compressor of the one outdoor unit, and merged with the refrigerant discharged from the compressor of the other outdoor unit. The air conditioning apparatus according to claim 1, wherein   2. When the defrosting of the one outdoor unit is completed, the four-way valve is switched, and the defrosting of the other outdoor unit is performed following the defrosting of the one outdoor unit. Or the air conditioning apparatus of 2. The air conditioner according to any one of claims 1 to 3, wherein the indoor expansion valve of the indoor unit is fully closed during the defrosting operation.

Images