CN108474595B

CN108474595B - Air conditioner and control method thereof

Info

Publication number: CN108474595B
Application number: CN201680079580.5A
Authority: CN
Inventors: 武市久史; 青野正弘
Original assignee: Samsung Electronics Co Ltd
Current assignee: Samsung Electronics Co Ltd
Priority date: 2016-02-19
Filing date: 2016-12-08
Publication date: 2021-07-09
Anticipated expiration: 2036-12-08
Also published as: KR102461708B1; CN108474595A; EP3374704A1; KR20170098138A; EP3374704A4; JP2017146061A

Abstract

An air conditioner is provided. The air conditioner includes a heat pump cycle in which a compressor, an outdoor heat exchanger, an expansion valve, and an indoor heat exchanger are sequentially connected to each other. A resistance passage is provided between the outlet of the compressor and the outdoor heat exchanger to increase the pressure of the refrigerant flowing from the outlet to the outdoor heat exchanger.

Description

Air conditioner and control method thereof

Technical Field

Apparatuses and methods consistent with exemplary embodiments relate to an air conditioner.

Background

In recent years, an air conditioner installed in a server room or the like can perform a cooling operation even at a low outdoor temperature in winter (for example, at a low outdoor temperature such as minus 25 degrees or less).

When the cooling operation is performed at a low outdoor temperature, the heat exchange capacity of the outdoor heat exchanger is superior to that of the indoor heat exchanger, and thus there is no difference between the condensing pressure and the evaporating pressure. Therefore, the compressor may malfunction, and in this case, there is a problem in that reliability of the compressor cannot be secured.

Disclosure of Invention

Technical problem

One or more exemplary embodiments may overcome the above disadvantages and other disadvantages not described above. However, it should be understood that one or more exemplary embodiments are not required to overcome the disadvantages described above, and may not overcome any of the problems described above.

One or more exemplary embodiments provide an air conditioner that can ensure a differential compressor pressure even when a cooling operation is performed at a low outdoor temperature, and a control method thereof.

Technical scheme

According to an aspect of exemplary embodiments, there is provided an air conditioner including a heat pump cycle and a resistance passage, wherein a compressor, an outdoor heat exchanger, an expansion valve, and an indoor heat exchanger are sequentially connected to each other in the heat pump cycle; the resistance passage is provided between an outlet of the compressor and the outdoor heat exchanger to increase a pressure of the refrigerant flowing from the outlet to the outdoor heat exchanger.

The resistance channel may comprise a small bore tube or capillary tube having a diameter smaller than the diameter of the outlet.

The air conditioner may further include a bypass passage connected in parallel with the resistance passage, and a bypass valve opening and closing the bypass passage.

The bypass passage may have a diameter greater than a diameter of the resistance passage, and the flow rate of the refrigerant passing through the bypass passage may be greater than the flow rate of the refrigerant passing through the resistance passage in response to the bypass valve being opened.

The air conditioner may further include a return passage branched between the outlet and the resistance passage and connected to an inlet of the compressor, and a return valve opening and closing the return passage.

The return passage may have a diameter greater than that of the resistance passage, and some of the refrigerant discharged from the outlet may be returned to the compressor through the return passage in response to the return valve being opened.

The air conditioner may further include an injection passage and an injection valve, wherein the injection passage is branched between the expansion valve and the indoor heat exchanger and connected with the inlet; the injection valve opens and closes the injection passage, and some of the refrigerator flowing between the expansion valve and the indoor heat exchanger may flow into the inlet in response to the injection valve being opened.

The injection passage may have one end thereof branched between the expansion valve and the indoor heat exchanger and the other end thereof opposite to the one end branched from the return passage.

The air conditioner may further include an injection passage and a return passage, wherein the injection passage is branched between the expansion valve and the indoor heat exchanger and connected with an inlet of the compressor; the return channel has one end thereof branched between the outlet and the resistance channel and the other end thereof opposite to the one end branched from the injection channel.

The refrigerant may be R32 refrigerant or a mixed refrigerant including R32 refrigerant.

According to an aspect of another exemplary embodiment, there is provided a control method of an air conditioner, including: measuring a discharge temperature of refrigerant discharged from an outlet of the compressor; comparing the discharge temperature with a first reference temperature and a second reference temperature, wherein the second reference temperature is lower than the first reference temperature; controlling a bypass passage, wherein the bypass passage is connected in parallel with a resistance passage having a diameter larger than that of the resistance passage, the resistance passage for increasing a pressure of refrigerant discharged from the outlet by connecting the connection outlet and the outdoor heat exchanger; a control return channel, wherein the return channel branches between the outlet and the resistance channel and is connected with the inlet of the compressor, and has a diameter larger than that of the resistance channel; and a control injection passage, wherein the injection passage is branched between an expansion valve of the compressor and an indoor heat exchanger connected to the expansion valve and connected to the inlet.

In response to the discharge temperature being greater than or equal to the second reference temperature and less than the first reference temperature, the return passage may be closed and the injection passage may be opened at a predetermined opening degree.

In response to the discharge temperature being greater than or equal to the first reference temperature, the bypass passage may be opened, the return passage may be closed, and the injection passage may be opened at a predetermined opening degree.

According to an aspect of another exemplary embodiment, there is provided a control method of an air conditioner, including: measuring an outdoor temperature of a location where the compressor is disposed; comparing the outdoor temperature with a predetermined low control temperature; measuring a discharge pressure of refrigerant discharged from an outlet of the compressor and an inflow pressure of refrigerant flowing into an inlet of the compressor; comparing a compression ratio calculated by dividing the discharge pressure by the inflow pressure with a predetermined reference value; comparing the discharge pressure to a first reference pressure and a second reference pressure, wherein the second reference pressure is greater than the first reference pressure; controlling a bypass passage, wherein the bypass passage is connected in parallel with a resistance passage and has a diameter greater than that of the resistance passage, the resistance passage for increasing a pressure of refrigerant discharged from the outlet by connecting the outlet and the outdoor heat exchanger; and a control return channel, wherein the return channel branches between the outlet and the resistance channel and is connected with the inlet of the compressor and has a diameter larger than that of the resistance channel.

In response to the outdoor temperature being greater than or equal to the low control temperature or the compression ratio being greater than or equal to the reference value, the bypass passage may be opened and the return passage may be closed.

The bypass passage may be closed and the return passage may be opened in response to the outdoor temperature being less than the low control temperature and the compression ratio being less than the reference value, and in response to the discharge pressure being less than the first reference pressure.

The bypass passage may be opened and the return passage may be opened in response to the outdoor temperature being less than the low control temperature and the compression ratio being less than the reference value, and in response to the discharge pressure being greater than or equal to the first reference pressure and less than the second reference pressure.

The bypass passage may be opened and the return passage may be closed in response to the outdoor temperature being less than the low control temperature and the compression ratio being less than the reference value, and in response to the discharge pressure being greater than or equal to the second reference pressure.

The control method may further include: the discharge pressure and the inflow pressure are re-measured, and the bypass passage may be opened and the return passage may be closed in response to a pressure difference between the re-measured discharge pressure and the re-measured inflow pressure being greater than or equal to a predetermined value.

The control method may further include: the discharge pressure and the inflow pressure are remeasured, and in response to a compression ratio calculated by dividing the remeasured discharge pressure by the remeasured inflow pressure being greater than or equal to a predetermined value, the bypass passage may be opened and the return passage may be closed.

Additional and/or other aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.

Drawings

The above and/or other aspects of the present disclosure will become more apparent by describing certain exemplary embodiments thereof with reference to the attached drawings, in which:

fig. 1 is a view showing a schematic configuration of an air conditioner according to an exemplary embodiment;

fig. 2 and 3 are views illustrating a control flow of temperature protection control according to the air conditioner shown in fig. 1;

fig. 4 and 5 are views illustrating a control flow of low-temperature outdoor air control according to the air conditioner shown in fig. 1;

fig. 6 is a view showing experimental data indicating the effects achieved by the low-temperature outdoor air control shown in fig. 4 and 5;

fig. 7 is a view showing a schematic configuration of an air conditioner according to another exemplary embodiment;

fig. 8 is a view showing a schematic configuration of an air conditioner according to another exemplary embodiment;

fig. 9 is a view showing a schematic configuration of an air conditioner according to another exemplary embodiment; and

fig. 10 is a graph illustrating an effect of the air conditioner shown in fig. 9.

Detailed Description

Hereinafter, exemplary embodiments will be described in detail with reference to the accompanying drawings. In order to understand the technical features of the present disclosure, the exemplary embodiments described below will be described based on the most appropriate embodiments, but the technical features of the present disclosure are not limited by the embodiments disclosed herein, and it is stated that the present disclosure can be implemented as in the embodiments described below.

Therefore, various changes may be made in the embodiments described below within the technical scope of the present disclosure, and it should be noted that the changes to the embodiments belong to the technical scope of the present invention. In addition, with respect to reference numerals described in the drawings, related components among components performing the same operation in various embodiments may be denoted by the same or similar reference numerals to help the embodiments be thoroughly understood.

Fig. 1 is a view showing a schematic configuration of an air conditioner 100 according to an exemplary embodiment.

As shown in fig. 1, an air conditioner 100 according to an exemplary embodiment may include an indoor unit 10, an outdoor unit 20, and a heat pump cycle 200, the heat pump cycle 200 being configured to allow refrigerant to flow in the indoor unit 10 and the outdoor unit 20.

The refrigerant used in the air conditioner 100 may be R32 refrigerant or a mixed refrigerant including R2 refrigerant. Thereby, a discharge temperature of the refrigerant discharged from the compressor 23 may be increased, and accordingly, an effect of the air conditioner 100 may be enhanced.

The indoor unit 10 may include

decompressors

11A and 11B and

indoor heat exchangers

12A and 12B, wherein the

decompressors

11A and 11B are connected (coupled) in parallel with each other, and the

indoor heat exchangers

12A and 12B are connected to the

decompressors

11A and 11B in series, respectively.

The outdoor unit 20 may include a four-way valve 21, an accumulator 22, a compressor 23, an outdoor heat exchanger 24, a distributor 25, an expansion valve 26, and an outdoor auxiliary heat exchanger 27.

The heat pump cycle 200 may include a main line 201 in which the

decompressors

11A and 11B, the

indoor heat exchangers

12A and 12B, the four-way valve 21, the outdoor heat exchanger 24, the distributor 25, the expansion valve 26, and the outdoor auxiliary heat exchanger 27 are sequentially connected to each other, and a compression line 202 in which the accumulator 22, the compressor 23, and the four-way valve 21 are sequentially connected to each other.

The configuration of the heat pump cycle 200, the main line 201, and the compression line 202 described above may be changed in various ways, for example, by connecting the above-described components, omitting some of the above-described components, or replacing some of the components with other components.

The heat pump cycle 200 may further include an injection passage 203 that causes some of the refrigerant flowing from the

decompressors

11A and 11B to the expansion valve 26 to branch from the above-described main line 201, thereby guiding some or at least a portion of the refrigerant to the compressor 23 without guiding (not guiding) the at least a portion of the refrigerant to the outdoor heat exchanger 24.

Specifically, the injection passage 203 may be branched between the expansion valve 26 and the

indoor heat exchangers

12A and 12B, and may be connected to an inlet of the compressor 23 to allow the refrigerant to flow into the compressor 23.

In addition, an injection valve (EV) may be provided to open and close the injection passage 203, and some or at least a portion of the refrigerant flowing between the expansion valve 26 and the

indoor heat exchangers

12A and 12B may flow into the inlet of the compressor 23 through the injection passage 203 in response to the injection valve (EV) being opened.

The refrigerant flowing into the inlet of the compressor 23 through the injection passage 203 may have a reduced temperature because it passes through the outdoor auxiliary heat exchanger 27, and thus, the temperature of the refrigerant flowing into the compressor 23 through the injection passage 203 may be lower than that of the refrigerant discharged from the outlet of the compressor 23.

The injection passage 203 may include an injection pipe (La) having one end connected to an inlet of the compressor 23 and the other end connected between the expansion valve 26 and the

decompressors

11A and 11B, an injection valve (EV) disposed on the injection pipe (La), and an outdoor auxiliary heat exchanger 27 disposed on the injection pipe (La) between the compressor 23 and the injection valve (EV).

The injection valve (EV) may be an electrically operated valve as a flow rate control valve.

In addition, the outdoor auxiliary heat exchanger 27 may be disposed above the main line 201 and the injection passage 203.

As shown in fig. 1, the compression circuit 202 may include a resistance passage 30 connected to an outlet of the compressor 23.

A resistance passage 30 may be provided between the outlet of the compressor 23 and the outdoor heat exchanger 24 to increase the pressure of the refrigerant discharged from the outlet of the compressor 23.

In addition, a resistance passage 30 may be provided between the outlet of the compressor 23 and the four-way valve 21.

Specifically, the resistance passage 30 may include a small hole tube or a capillary tube connected to the outlet pipe (Lc) of the compressor 23, and the diameter of the small hole tube or the capillary tube may be smaller than the diameter of the outlet or the outlet pipe (Lc) of the compressor 23. Thereby, the refrigerant discharged from the outlet of the compressor 23 may have a pressure increased by the resistance passage 30, and thus, a pressure difference of the compressor 23 may be secured.

The compression circuit 202 may include a bypass passage 204 that branches off from the upstream (or compressor outlet) side of the resistance passage 30 on the outlet duct (Lc) and joins the downstream (toward the outdoor heat exchanger) side of the resistance passage 30 on the outlet duct (Lc).

Thus, the bypass passage 204 may be connected in parallel with the resistance passage 30.

For example, the bypass passage 204 may branch from between the resistance passage 30 and the outlet of the compressor 23, and at the same time, may be connected between the resistance passage 30 and the outdoor heat exchanger 24.

In addition, a bypass valve (SV1) may be provided to open and close the bypass passage 204, and the bypass valve (SV1) may include an electric valve or the like, for example.

In addition, the diameter of the bypass passage 204 may be greater than the diameter of the resistance passage 30, and thus, in response to the bypass valve (SV1) being open, the flow rate of refrigerant through the bypass passage 204 may be greater than the flow rate of refrigerant through the resistance passage 30. Additionally, in response to the bypass valve (SV1) being open, refrigerant may not pass through the resistance passage 30.

The air conditioner 100 may further include a return passage 205 having one end connected to an upstream (or compressor outlet) side of the resistance passage 30 on the outlet duct (Lc) and the other end connected to an inlet of the compressor 23 at the same time, thereby returning some or at least a portion of the refrigerant discharged from the compressor 23 to the compressor 23.

The return channel 205 may branch from between the outlet of the compressor 23 and the resistance channel 30, and may be connected to the inlet of the compressor 23.

In addition, a return valve (SV2) may be provided to open and close the return passage 205, and for example, the return valve (SV2) may be an electric valve.

In addition, the diameter of the return passage 205 may be larger than the diameter of the resistance passage 30, and thus, some of the refrigerant discharged from the outlet of the compressor 23 may be returned to the inlet of the compressor 23 through the return passage 205 in response to the return valve (SV2) being opened.

Specifically, the return passage 205 may include a connection pipe (Lb) connecting the above-described injection pipe (La) and the outlet pipe (Lc), and the return passage 205 to the inlet of the compressor 23 is formed by a portion of the injection pipe (La).

In addition, the injection passage 203 may be configured such that one end thereof branches from between the expansion valve 26 and the

indoor heat exchangers

12A and 12B, and the other end thereof opposite to the one end branches from the return passage 205.

The bypass valve (SV1), return valve (SV2), and injection valve (EV) described above may be controlled by a controller (not shown). When the compressor 23 is operated to perform the cooling operation at a low outdoor temperature, the injection valve (EV) provided in the injection pipe (La) and the bypass valve (SV1) provided in the bypass passage 204 are controlled to be closed, and the return valve (SV2) provided in the connection pipe (Lb) is controlled to be opened.

Fig. 2 and 3 are views of a control flow according to the temperature protection control of the air conditioner 100, and fig. 4 and 5 are views showing a control flow according to the low-temperature outdoor air control of the air conditioner 100.

Hereinafter, a control method of the air conditioner 100 will be described with reference to fig. 2 and 3, wherein the control method of the air conditioner 100 can prevent a malfunction of the compressor 23 and the like by adjusting a sudden rise in refrigerant temperature according to an exemplary embodiment. Hereinafter, for convenience of explanation, the control method of the air conditioner 100 for adjusting the sudden rise of the refrigerant temperature will be referred to as temperature protection control.

In fig. 2, at S1001, a discharge temperature of the refrigerant discharged from the compressor 23 is measured. At S1002, the discharge temperature is compared with the first reference temperature and the second reference temperature. In response to the comparison, at S1003, S1004, and S1005, the opening and closing of the bypass passage SV1, the return passage SV2, and the injection passage are controlled to perform the temperature protection control of the air conditioner. The comparison and control operations and the storage of the reference values in the at least one memory may be performed, implemented, by at least one controller (e.g., a machine, an electronic circuit, a hardware processor). In response to the operation of the compressor 23, a discharge temperature (Td) of refrigerant measured by a temperature sensor (not shown) provided at an outlet of the compressor 23 is compared with a predetermined first reference temperature (T1) and a predetermined second reference temperature (T2), and it is determined whether the discharge temperature (Td) is less than the first reference temperature (T1) and the second reference temperature (T2) (S101).

In addition, for example, the first reference temperature (T1) and the second reference temperature (T2) may be set to temperatures for protecting various components such as the compressor 23, refrigerant, oil, and the like, and hereinafter, as an example, the second reference temperature (T2) is set to be lower than the first reference temperature (T1).

In step S101 of determining whether the discharge temperature (Td) is less than the first reference temperature (T1) and the second reference temperature (T2), in response to the discharge temperature (Td) being less than the first reference temperature (T1) and the second reference temperature (T2), the operation of comparing the temperatures as described above is continued.

In the step S101 of determining whether the discharge temperature (Td) is less than the first reference temperature (T1) and the second reference temperature (T2), in response to the discharge temperature (Td) not being less than the first reference temperature (T1) and the second reference temperature (T2), it is determined whether the discharge temperature (Td) is greater than or equal to the second reference temperature (T2) and less than the first reference temperature (T1) (S102).

In response to the discharge temperature (Td) being greater than or equal to the second reference temperature (T2) and less than the first reference temperature (T1), the return valve (SV2) is closed (S200) and the injection valve (EV) is opened at a predetermined opening degree (S300).

Thereby, the refrigerant discharged from the outlet of the compressor 23 may be prevented from returning to the compressor 23 through the return passage 205, and the refrigerant of a low temperature flows into the inlet of the compressor 23 through the injection passage 203, so that the temperature of the refrigerant may be reduced.

Thereafter, the control method returns to step S101 to determine whether the discharge temperature (Td) is less than the first reference temperature (T1) and the second reference temperature (T2), and continues to compare the temperatures as described above.

In step S102 of determining whether the discharge temperature (Td) is greater than or equal to the second reference temperature (T2) and less than the first reference temperature (T1), in response to the discharge temperature (Td) being not greater than or equal to the second reference temperature (T2) and not less than the first reference temperature (T1), that is, in response to the discharge temperature (Td) being greater than or equal to the first reference temperature (T1), the bypass valve (SV1) is opened (S400), the return valve (SV2) is closed (S500), and the injection valve (EV) is opened at a predetermined opening degree (S600).

Thus, the refrigerant discharged from the compressor 23 flows through the bypass passage 204, and thus does not flow through the resistance passage 30. Therefore, the pressure of the refrigerant does not rise, and a temperature rise due to the pressure rise can also be prevented. In addition, by closing the return passage 205, the refrigerant discharged from the outlet of the compressor 23 may be prevented from returning to the compressor 23 through the return passage 205. In addition, the refrigerant of a low temperature flows into the inlet of the compressor 23 through the injection passage 203, so that the temperature of the refrigerant can be reduced.

Through the above-described temperature protection control, the temperature can be maintained even when the compressor 23 is operated and the temperature of the refrigerant rises to a high temperature, thereby preventing malfunctions of various devices (such as the compressor 23), the refrigerant, oil, and the like caused by the high temperature, and various problems of the air conditioner 100 caused by the sudden rise in the temperature of the refrigerant can be prevented in advance.

In addition, the above-described temperature protection control may be performed before the low-temperature outdoor air control (which will be described later) is performed, or may be performed simultaneously.

Hereinafter, a control method of the air conditioner 100 according to a cooling operation at a low outdoor temperature will be described with reference to fig. 4 and 5. Hereinafter, for convenience of description, a control method of the air conditioner 100 according to a cooling operation at a low outdoor temperature will be referred to as a low-temperature outdoor air control.

The low-temperature outdoor air control may be performed in response to an outdoor temperature measured by a temperature measuring sensor (not shown) provided in the outdoor unit 20 being lower than a predetermined low-temperature control temperature and in response to a pressure ratio between a discharge pressure (HP) of refrigerant discharged through an outlet of the compressor 23 and an inflow pressure (LP) of refrigerant flowing through an inlet of the compressor 23 or a pressure difference between the discharge pressure (HP) and the inflow pressure (LP) being less than a predetermined reference value.

Therefore, in response to the outdoor temperature being greater than or equal to the low temperature control temperature or the pressure ratio or the pressure difference between the discharge pressure (HP) and the inflow pressure (LP) being greater than or equal to the reference value, the separate low temperature outdoor air control is not performed, and the bypass passage 204 is opened by opening the bypass valve (SV1) and the return passage 205 is closed by closing the return valve (SV 2). Thus, the air conditioner can flow the refrigerant discharged through the outlet of the compressor 23 without any change by simply operating in a normal manner.

In addition, the discharge pressure (HP) may be measured by a discharge pressure sensor (Pa) provided at an outlet of the compressor 23, and the inflow pressure (LP) may be measured by an inflow pressure sensor (Pb) provided at an inlet of the compressor 23.

The low-temperature outdoor air control may be configured to be performed in response to an outdoor temperature being less than or equal to about 10 degrees celsius and a discharge pressure (HP)/inflow pressure (LP) being less than about 2.1.

In response to performing the low-temperature outdoor air control and operating the compressor 23, it is determined whether the discharge pressure (HP) is less than the first reference pressure (P1) and the second reference pressure (P2) by comparing the discharge pressure (HP) with a predetermined first reference pressure (P1) and a predetermined second reference pressure (P2) (S1).

The first reference pressure (P1) and the second reference pressure (P2) are values that are set in advance based on, for example, the design pressure of the compressor 23, and hereinafter, as an example, the second pressure (P2) is set to be greater than the first reference pressure P1.

In step S1 of determining whether the discharge pressure (HP) is less than the first reference pressure (P1) and the second reference pressure (P2), the bypass filter (SV1) is maintained in a closed state (S2) and the return valve (SV2) is also maintained in an open state (S3) in response to the discharge pressure (HP) being less than the first reference pressure (P1) and the second reference pressure (P2).

Thereby, the refrigerant discharged through the outlet of the compressor 23 may have its pressure increased by passing through the resistance passage 30, and a pressure difference may be secured. In addition, some of the refrigerant is returned to the compressor 23 through the return passage 205, so that the pressure of the refrigerant can be prevented from abruptly rising.

In addition, by increasing the pressure of the compressor 23, a supercooling phenomenon occurs and an evaporation temperature is lowered by a high condensing capacity, so that the cooling efficiency can be prevented from being deteriorated.

In step S1 of determining whether the discharge pressure (HP) is less than the first reference pressure (P1) and the second reference pressure (P2), in response to the discharge pressure (HP) not being less than the first reference pressure (P1) and the second reference pressure (P2), it is determined whether the discharge pressure (HP) is greater than or equal to the first reference pressure (P1) and less than the second reference pressure (P2) (S4).

In step S4 of determining whether the discharge pressure (HP) is greater than or equal to the first reference pressure (P1) and less than the second reference pressure (P2), in response to the discharge pressure (HP) being greater than or equal to the first reference pressure (P1) and less than the second reference pressure (P2), the bypass valve (SV1) is opened (S5) and the return valve (SV2) is opened (S6).

Thus, among the refrigerant discharged through the outlet of the compressor 23, the flow rate of the refrigerant passing through the bypass passage 204 is greater than the flow rate of the refrigerant passing through the resistance passage 30, and thus the pressure of the refrigerant does not rise, and some of the refrigerant returns to the compressor 23 through the return passage 205, so that the pressure of the refrigerant can be prevented from abruptly changing.

In addition, the pressure of the compressor 23 may be increased only by the refrigerator returned through the return passage 205, and thus, a compression ratio for maintaining the reliability of the compressor 23 optionally according to the environmental conditions and the condensation temperature may be secured.

In step S4 of determining whether the discharge pressure (HP) is greater than or equal to the first reference pressure (P1) and less than the second reference pressure (P2), in response to the discharge pressure (HP) not being greater than or equal to the first reference pressure (P1) and not less than the second reference pressure (P2), that is, in response to the discharge pressure (HP) being greater than or equal to the second reference pressure (P2), the bypass valve (SV1) is opened (S7) and the return valve (SV2) is closed (S8).

This is a case where the pressure difference of the compressor 23 has been ensured, and the refrigerant discharged from the outlet of the compressor 23 may flow into the bypass passage 204 without pressure change by the normal operation of the air conditioner 100.

Next, it is determined whether the low-temperature outdoor air control is completed by the controller (S9).

Specifically, the low temperature outdoor air control may be set to complete in response to a pressure ratio or pressure differential between the re-measured discharge pressure (HP) and the re-measured inflow pressure (LP) being greater than a predetermined reference value.

For example, the method may be responsive to the discharge pressure (HP)/inflow pressure (LP) being greater than or equal to about 2.1 and the discharge pressure (HP) being greater than 15kgf/cm²G, low-temperature outdoor air control is set to be completed.

In step S9 of determining whether to complete the low-temperature outdoor air control, in response to completion of the low-temperature outdoor air control, the bypass valve (SV1) is opened or kept open (as appropriate) (S10) and at the same time the return valve (SV2) is closed or kept closed (as appropriate) (S11). Thereby, the refrigerator discharged from the outlet of the compressor 23 flows into the bypass passage 204 without any pressure change.

In step S9 of determining whether the low temperature outdoor air control is completed, in response to the low temperature outdoor air control not being completed, the control method returns to step S1 of determining whether the discharge pressure (HP) is less than the first reference pressure (P1) and the second reference pressure (P2), and compares the discharge pressure (HP) with the first reference pressure (P1) and the second reference pressure (P2).

Since the air conditioner 100 according to the exemplary embodiment includes the resistance passage 30 at the outlet of the compressor 23, a pressure difference of the compressor 23 may be easily secured during a cooling operation at a low outdoor temperature, and furthermore, a pressure of the refrigerator may be prevented from abruptly rising by returning some of the refrigerator to the compressor 23 through the return passage 205 while the compressor 23 is operating.

Experimental data indicating the effects achieved by the above-described low-temperature outdoor air control are shown in fig. 6.

As can be seen from the experimental data of fig. 6, the compression ratio of the related art compressor is 1.5, and the discharge pressure of the outlet of the compressor 23 is rapidly increased by performing the low temperature outdoor air control of the air conditioner according to the exemplary embodiment, and the compression ratio is also increased to 3.8.

As described above, the formation of the rotation of the compressor 23 (the rotation of the compressor 23) can be ensured by increasing the discharge pressure of the outlet of the compressor 23, and thus the abnormal noise of the compressor 23 can be reduced.

In addition, the return channel 205 is configured by connecting the injection conduit (La) and the outlet conduit (Lc), so that a part of the injection channel 203 can be used as the return channel 205. Accordingly, the overall configuration of the air conditioner 10 may be simplified and also a pressure difference of the compressor 23 may be ensured during a cooling operation at a low outdoor temperature.

In addition, by selectively opening and closing the bypass valve (SV1) of the bypass passage 204 that bypasses the resistance passage 30, the refrigerator discharged from the compressor 23 can be prevented from flowing into the resistance passage 30 when there is no need to increase the discharge pressure of the compressor 23.

The control method of the air conditioner 100 according to the exemplary embodiment is not limited to the above-described embodiment.

In the above embodiment, the air conditioner 100 is applied to a cooling operation at a low outdoor temperature. However, the air conditioner 100 according to the exemplary embodiment may be operated under other conditions in addition to the low outdoor temperature.

In addition, in response to the air conditioner 100 operating in the heating operation mode or the defrosting mode, some of the refrigerators discharged from the compressor 23 are returned to the compressor 23 and the remaining refrigerators are flowed into the

indoor heat exchangers

12A and 12B or the outdoor heat exchanger 24. Therefore, by increasing the temperature of the refrigerant, the performance of rapid heating can be enhanced or the time required for defrosting can be reduced.

In addition, the indoor unit 10 described above includes two indoor heat exchangers connected in parallel with each other. However, the indoor unit 10 may include three or more indoor heat exchangers.

In addition, the air conditioner 100 described above includes a single compressor 23. However, the air conditioner 100 may include a plurality of compressors.

Fig. 7 is a view showing a schematic configuration of an air conditioner according to another exemplary embodiment, and fig. 8 is a view showing a schematic configuration of an air conditioner according to another exemplary embodiment.

Fig. 7 and 8 show a refrigeration circuit of the outdoor unit 20 having two compressors 23. In addition, the compressors 23 may have the same capacity or may have different capacities.

In the course of the cooling operation of the air conditioner shown in fig. 7 and 8 at a low outdoor temperature, any one of the compressors 23 is controlled to operate, and a resistance passage 30 may be provided in the outlet duct (Lc) of the compressor 23, wherein the resistance passage 30 is used in the cooling operation at a low outdoor temperature.

In addition, the air conditioner may include a bypass passage connected to the resistance passage 30 in parallel and a bypass valve (SV1), and the bypass valve may be closed in response to performing the low-temperature outdoor air control (SV 1).

The air conditioner 100 shown in fig. 7 and 8 may include an accumulator 22, a suction pipe (Ld) that sucks the gas refrigerant distributed by the accumulator 22 into each compressor 23, an oil distributor provided at an outlet of each of the compressors 23, an oil distributor that introduces oil separated by the oil distributor 28 and also obtains oil in other compressors 23 different from the compressor 23 corresponding to the oil distributor 28, and an oil obtaining pipe (Le).

With this configuration, the oil separated by each oil distributor 28 is supplied to the compressor 23 different from the compressor 23 corresponding to each oil distributor 28, so that even when a plurality of compressors 23 having different capacities are operated, an oil imbalance phenomenon in which oil is accumulated on a specific compressor 23 can be prevented.

Fig. 9 is a view illustrating a schematic configuration of an air conditioner according to another exemplary embodiment, and fig. 10 is a graph illustrating an effect of the air conditioner illustrated in fig. 9.

In the above embodiments, the air conditioner having the single outdoor heat exchanger has been described. However, the air conditioner 100 shown in fig. 9 may include a plurality of outdoor heat exchangers 24 arranged in parallel.

Further, the air conditioner 100 may include two outdoor heat exchangers 24 having different heat exchange efficiencies.

With the above configuration, the capacity switching function of the outdoor heat exchanger 24 can be used. By selecting the outdoor heat exchanger 24 having low heat exchange efficiency, i.e., the outdoor heat exchanger 24 having a small capacity, as shown in fig. 10, the discharge pressure of the compressor 23 can be further increased, and the temperature operation range of the air conditioner 100 can be expanded.

In addition, by increasing the discharge pressure of the compressor 23 as described above, the cooling operation and the heating operation can be normally performed even when there is a difference in the outdoor heat exchanger 24 and the indoor heat exchanger 12.

In the above description, the various embodiments have been described separately, but the embodiments should not necessarily be implemented independently, and the configuration and operation of the embodiments may be implemented in combination with at least one other embodiment.

While the invention has been shown and described with reference to certain preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. Therefore, the scope of the invention is defined not by the detailed description of the invention but by the appended claims, and all differences within the scope will be construed as being included in the present invention.

Claims

1. An air conditioner, comprising:

a four-way valve having an inlet and a plurality of outlets;

a first compressor;

a heat pump cycle in which the first compressor, at least one outdoor heat exchanger, an expansion valve, and at least one indoor heat exchanger are sequentially coupled to one another, wherein the outdoor heat exchanger is coupled to an outlet among a plurality of outlets of the four-way valve;

a resistance passage provided between an outlet of the first compressor and an inlet of the four-way valve to increase a pressure of the refrigerant flowing from the outlet of the first compressor to the outdoor heat exchanger via the four-way valve;

a bypass channel connected in parallel to the resistance channel;

a bypass valve configured to open and close the bypass passage such that the refrigerant flowing from the outlet of the first compressor to the outdoor heat exchanger via the four-way valve does not pass through the resistance passage based on the bypass valve being opened;

a second compressor having an outlet through which refrigerant flows to an inlet of the four-way valve and then to the outdoor heat exchanger via the four-way valve, the resistance passage not being located between the outlet of the second compressor and the inlet of the four-way valve;

a return passage having one end disposed downstream of an outlet of the first compressor and upstream of the first oil distributor, and the other end of the return passage being branched into a first branch coupled to an inlet of the first compressor and a second branch coupled to an inlet of the second compressor;

a return valve that opens and closes the return passage,

a first oil distributor located at an outlet of the first compressor and upstream of the resistance passage and the bypass passage;

a second oil distributor located at an outlet of the second compressor and upstream of an inlet of the four-way valve;

a first pipe that supplies the oil separated by the first oil distributor to the second compressor; and

a second pipe that supplies the oil separated by the second oil distributor to the first compressor,

wherein the first compressor is controlled to operate in a cooling operation at a lower outdoor temperature than the second compressor.

2. The air conditioner of claim 1, wherein the resistance passage comprises a small bore tube or capillary tube having a diameter smaller than a diameter of the outlet.

3. The air conditioner of claim 1, wherein,

the diameter of the bypass passage is greater than the diameter of the resistance passage, an

In response to the bypass valve opening, a flow rate of refrigerant through the bypass passage is greater than a flow rate of refrigerant through the resistance passage.

4. The air conditioner as claimed in claim 1, wherein the return passage has a diameter greater than that of the resistance passage.