JP2015014372A - Air conditioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an air conditioner that restrains the discharge gas temperature of a compressor while preventing liquid from entering the compressor.SOLUTION: An air conditioner comprises: an injection pipe for connecting a pipe located between an indoor heat exchanger and an expansion valve to a compressor; an injection valve provided in the injection pipe; a compressor outlet temperature sensor for detecting the outlet temperature of the compressor; a suction tank inlet temperature sensor for detecting the inlet temperature of a suction tank; and a suction tank outlet temperature sensor for detecting the outlet temperature of the suction tank. The compressor or the expansion valve is controlled so that the temperature detected by the suction tank outlet temperature sensor is higher than the temperature detected by the suction tank inlet temperature sensor, and the injection valve is controlled so that the temperature detected by the compressor outlet temperature sensor is equal to or less than a first predetermined value.

Description

  The present invention relates to an air conditioner.

  For example, when operating an air conditioner in a very cold region, the temperature difference between the outdoors and indoors is large, the compression ratio of the compressor must be increased, and the discharge gas temperature of the compressor rises. Then, deterioration of the resin material of the compressor, the magnet, and the refrigerating machine oil proceeds, and there is a risk that the long-term reliability of the air conditioner may be reduced.

  In order to solve such a problem, a liquid injection method is known as means for suppressing the discharge gas temperature.

  Patent Document 1 discloses a liquid refrigerating apparatus that controls a discharge gas temperature by liquid-injecting a part of a high-pressure liquid refrigerant into an intermediate pressure chamber that is being compressed, and controls liquid injection operation according to a change in the discharge gas temperature of the compressor. It discloses changing the temperature.

Japanese Patent Laid-Open No. 8-200247

  In Patent Document 1, liquid injection is controlled only by the discharge gas temperature of the compressor. The state of the refrigerant sucked into the compressor cannot be grasped and controlled.

  However, since the compressor used for the air conditioner cannot compress the liquid, in order to maintain the reliability of the compressor, the refrigerant is gasified at the outlet of the evaporator and the liquid does not enter the compressor. It is necessary to control.

  Then, an object of this invention is to provide the air conditioner which suppresses the discharge gas temperature of a compressor, preventing a liquid from entering a compressor.

  In order to solve the above problems, an air conditioner according to the present invention includes a cycle channel in which a refrigerant circulates by connecting a compressor, an indoor heat exchanger, an expansion valve, an outdoor heat exchanger, and a suction tank in order by a pipe. A pipe located between the indoor heat exchanger and the expansion valve or a pipe located between the outdoor heat exchanger and the expansion valve, an injection pipe connecting the compressor, an injection valve provided in the injection pipe, and a compressor A compressor outlet temperature sensor for detecting the outlet temperature of the suction tank, a suction tank inlet temperature sensor for detecting the inlet temperature of the suction tank, and a suction tank outlet temperature sensor for detecting the outlet temperature of the suction tank. The compressor or expansion valve is controlled so that the temperature detected by the suction tank becomes higher than the temperature detected by the suction tank inlet temperature sensor. , Controls the injection valve as detected by the compressor exit temperature sensor temperature is below a first predetermined value.

  ADVANTAGE OF THE INVENTION According to this invention, the air conditioner which suppresses the discharge gas temperature of a compressor can be provided, preventing a liquid from entering a compressor.

Air conditioner liquid injection cycle refrigerant circuit configuration diagram Configuration diagram of compressor, suction tank and temperature detection means Operation control diagram of liquid injection cycle Air conditioner supercooling injection cycle refrigerant circuit configuration diagram

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings as appropriate.

  FIG. 1 is a configuration diagram of a liquid injection cycle refrigerant circuit of an air conditioner. The air conditioner 1 includes a main circuit 10 in which a compressor 2, a flow path switching valve (for example, a four-way valve) 3, an outdoor heat exchanger 4, an expansion valve 5, an indoor heat exchanger 6, and a suction tank 7 are connected in an annular shape, An injection pipe 11 branched from the main circuit 10 between the indoor heat exchanger 6 and the expansion valve 5 and connected to the compressor 2 in the middle of compression through a decompression means 8 such as a capillary tube and an injection valve 9 of the circuit. Consists of. In order to control the air conditioner 1, the controller 50, the compressor outlet temperature sensor 51, the suction tank inlet temperature sensor 52, the suction tank outlet temperature sensor (compressor inlet temperature sensor) 53, and the outdoor heat exchanger temperature sensor 54. And an indoor heat exchanger temperature sensor 55.

  The operation of each device of the air conditioner 1 will be described with reference to FIGS. 1 and 2. When the operation mode of the air conditioner 1 is “cooling”, the refrigerant flows in the direction of the solid arrow in FIG. 1 by switching the four-way valve 3. In this embodiment, since the liquid injection during cooling is not performed, the injection valve 9 is closed and the refrigerant does not flow into the injection pipe 11. The refrigerant discharged from the compressor 2 is supplied to the outdoor heat exchanger 4 through the flow path indicated by the solid line of the four-way valve 3. The refrigerant discharged from the outdoor heat exchanger 4 is decompressed and expanded by the expansion valve 5 and supplied to the indoor heat exchanger 6. The refrigerant discharged from the indoor heat exchanger 6 returns to the suction tank 7 and the compressor 2 through the flow path indicated by the solid line of the four-way valve 3.

  When the operation mode of the air conditioner 1 is “heating”, the refrigerant flows in the direction of the broken-line arrow in FIG. 1 by switching the four-way valve 3. The refrigerant discharged from the compressor 2 is supplied to the indoor heat exchanger 6 through the flow path indicated by the broken line of the four-way valve 3. The refrigerant discharged from the outdoor heat exchanger 6 is decompressed and expanded by the expansion valve 5 and supplied to the outdoor heat exchanger 4. The refrigerant discharged from the outdoor heat exchanger 4 returns to the suction tank 7 and the compressor 2 through the flow path indicated by the broken line of the four-way valve 3.

  During normal heating operation, the injection valve 9 is closed, and the refrigerant does not flow into the injection pipe 11. On the other hand, liquid injection is performed under conditions where the discharge temperature is high. When performing liquid injection, the injection valve 9 is opened. Liquid refrigerant flows into the injection pipe 11 and is injected and evaporated during the compression of the compressor 2, thereby suppressing an increase in the discharge temperature of the compressor 2. In the outdoor heat exchanger 4 and the indoor heat exchanger 7, heat is exchanged between the flowing refrigerant and air.

  For example, the heat exchanger is configured in the form of a fin tube, and heat is transferred by passing air through a propeller fan, a cross-flow fan, or the like on the fin side and flowing a refrigerant through the pipe side. The control unit 50 acquires information such as the temperature detection means 51 to 54 and switches the four-way valve 3 and the opening degree of the expansion valve 5, the rotation speed of the compressor 2, the outdoor heat exchanger 4 and the indoor heat exchanger 6. This controls the amount of exchange heat on the air side. The suction tank 7 is provided in order to prevent the refrigerant from being compressed by the compressor 2 in the liquid state at the start of operation and the like from being impaired.

  FIG. 2 is a configuration diagram of the compressor, the suction tank, and the temperature detecting means. The compressor 2 is a positive displacement compressor. In the present embodiment, the compressor 2 is a compressor whose rotational speed is variable. The compressor 2, the suction tank 7, and the temperature detection means will be described with reference to FIG. A is a pipe for discharging the refrigerant, B and C are pipes for sucking the refrigerant, and parts having the same numbers as those in FIG. 1 are the same.

  In the present embodiment, temperature detection means for detecting the temperature of the suction refrigerant is installed in the temperature detection means 52 on the upstream side of the suction tank and the temperature detection means 53 on the upstream side of the compressor suction. In particular, since the temperature detection means 53 on the upstream side of the compressor suction needs to detect the temperature of the low-temperature suction refrigerant in the vicinity of the high-temperature compressor body, it is not affected by the heat from the compressor body. Location is desirable. It is also effective to make the suction pipe for detecting the temperature a material which is not easily affected by the heat from the compressor body and to cover the temperature detecting means 53 with a heat insulating material.

  The compressor 2 compresses gas with a positive displacement compressor as described above. Therefore, when the refrigerant is sucked, if the refrigerant is a liquid, the liquid with almost no volume change is compressed, so that a large load is applied to the compression chamber and the reliability is impaired. For this reason, the refrigerant needs to be gas at least at the position C.

  A specific control method of the operation described above will be described with reference to FIG. FIG. 3 is an operation control diagram of the liquid injection cycle. The control of this embodiment is not applied at the start of operation because the discharge temperature Td is low. During operation (100), comparison between the target value (target Td) of the discharge temperature determined by the outside air temperature, the compressor speed, and the operation requested by the user, and a predetermined upper limit temperature (upper limit Td) for ensuring reliability When the target Td becomes larger than the upper limit Td, the control is switched to the liquid injection control (101). If the target Td is smaller than the upper limit Td, the operation is continued (104).

  When the control is switched to the liquid injection control, it is first determined whether the compressor suction refrigerant state is gas (102). This is performed in order to prevent instability of the cycle due to the refrigerant state of the compressor suction being in a two-phase or liquid state and liquid refrigerant due to liquid injection flowing into the compressor.

  The determination (102) is made based on the difference between the suction tank inlet temperature Tstin detected by the suction tank inlet temperature sensor 52 and the suction tank outlet temperature Tstout detected by the suction tank outlet temperature sensor 53. If Tstout−Tstin> 0, It is determined that the suction refrigerant state is not gas, and the expansion valve 5 is adjusted (105).

  If Tstout−Tstin> 0, the compressor outlet temperature Td (actual Td) detected by the compressor outlet temperature sensor 51 is compared with the upper limit Td (103).

  If the actual Td−the upper limit Td <0, the process returns to the determination (101) for comparing the target Td and the upper limit Td. If the actual Td−the upper limit Td <0 is not satisfied, the injection valve 9 is adjusted to lower the actual Td (106). By opening the injection valve 9, liquid refrigerant flows in the middle of compression of the compressor 2, the compression chamber is cooled, and the discharge temperature Td is also lowered.

  For example, it is assumed that the target Td calculated from the outside air temperature and the compressor rotation speed in the heating operation is 100 ° C. If the predetermined upper limit Td is 80 ° C., it is switched to the liquid injection control in the determination (101). The upper limit Td determined here is set lower than the actual upper limit temperature that affects the reliability of the compressor in consideration of the amount of overshoot during control.

  At this time, if the suction tank inlet temperature Tstin is −5 ° C. and the suction tank outlet temperature Tstout is −7 ° C., for example, it is determined by the determination (102) that the suction state is not gas, and the expansion valve 5 is set to −5. It adjusts so that it may become larger than ° C (105). After the adjustment, if Tstout−Tstin> 0 is satisfied in determination (102), it is determined that the suction state is gas. At this time, the actual Td increases.

  As a result of determination (103), since actual Td-upper limit Td <0 is not satisfied, the injection valve 9 is opened (106), liquid refrigerant flows in during compression of the compressor 2, the compression chamber is cooled, and actual Td also decreases.

  Here, for example, it is assumed that the actual Td is lowered from 105 ° C. to 75 ° C. By the determination (102) and the adjustment (105) of the expansion valve 5, the refrigerant sucked in the compressor is adjusted to a gas state. For this reason, for example, it is assumed that the actual Td becomes 78 ° C.

  Again, in the determination (104), the actual Td is compared with the upper limit Td, and the actual Td is 78 ° C. with respect to the upper limit Td of 80 ° C. Therefore, the operation state is maintained until the target Td falls below the upper limit Td. (101).

  As described above, the air conditioner according to the present embodiment includes the injection pipe 11 that connects the pipe located between the indoor heat exchanger 4 and the expansion valve 5 and the compressor 2, and the injection provided in the injection pipe 11. The valve 9, the compressor outlet temperature sensor 51 for detecting the outlet temperature Td of the compressor 2, the suction tank inlet temperature sensor 52 for detecting the inlet temperature Tstin of the suction tank 7, and the outlet temperature Tstout of the suction tank 7 are detected. A suction tank outlet temperature sensor 53, and the outlet temperature Tstout of the suction tank 7 detected by the suction tank outlet temperature sensor 53 is compressed so that the inlet temperature Tstin of the suction tank 7 detected by the suction tank inlet temperature sensor 52 becomes higher. Controls the machine 2 or expansion valve 5 and exits the compressor Outlet temperature Td of the compressor 2 detected in degrees sensor 51 to control the injection valve 9 so as to be less than the first predetermined value.

  By controlling in this way, the compressor 2 is cooled, and the discharge temperature Td does not continue to operate at a temperature higher than a predetermined upper limit temperature, and long-term reliability due to deterioration of the resin material, magnet, and refrigeration oil constituting the refrigeration cycle. It can prevent a decline in sex. Furthermore, since the suction side refrigerant of the compressor 2 is in a gas state, an efficient operation can be performed.

  In addition, an outdoor heat exchanger temperature sensor 55 that detects the temperature of the outdoor heat exchanger 4 is provided so that the temperature detected by the suction tank outlet temperature sensor 53 is higher than the temperature detected by the suction tank inlet temperature sensor 52. Injection that controls the compressor 2 or the expansion valve 5 so that the difference between the temperature detected by the compressor outlet temperature sensor 51 and the condensation temperature detected by the outdoor heat exchanger temperature sensor 4 is less than or equal to a second predetermined value. The valve 9 may be controlled.

  In addition, this control is particularly effective for air conditioning applications such as R32, in which a refrigerant having a relatively high discharge temperature is used and can be operated in an operating range where reliability cannot be ensured due to high temperatures.

  The compressor outlet temperature sensor 51 includes a temperature sensor attached to the container of the compressor 2 and a temperature sensor attached to a pipe between the compressor 2 and the indoor heat exchanger 4. The suction tank inlet temperature sensor 52 includes a temperature sensor attached to the container of the suction tank 7 and a temperature sensor attached to a pipe between the suction tank 7 and the outdoor heat exchanger 6. The suction tank outlet temperature sensor 53 includes a temperature sensor attached to the container of the suction tank 7 and a temperature sensor attached to a pipe between the suction tank 7 and the compressor 2. The outdoor heat exchanger temperature sensor 54 measures the condensation temperature, and the indoor heat exchanger temperature sensor 55 measures the evaporation temperature.

  FIG. 4 is a supercooled injection cycle refrigerant circuit configuration diagram of the air conditioner. In the present embodiment, the operation control of the liquid injection cycle has been described. However, the same control can be applied to the operation control of the supercooling injection cycle as shown in FIG. In FIG. 4, the decompression means 8 and the injection valve 9 of FIG. 1 may be replaced with a supercooling heat exchanger 12 and a supercooling injection valve 13. The discharge temperature can be suppressed while suppressing a decrease in capacity due to the supercooling injection, and the efficiency is improved as compared with the liquid injection method.

  In addition, this invention is not limited to an above-described Example, Various modifications are included. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. Further, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Further, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.

  Moreover, although this embodiment demonstrated heating operation, it is applicable also to cooling operation. In the cooling operation, the above-described control is performed by replacing the indoor heat exchanger 4 and the outdoor heat exchanger 6 and the indoor heat exchanger temperature sensor 55 and the outdoor heat exchanger temperature sensor 54 with the four-way valve 3.

DESCRIPTION OF SYMBOLS 1 ... Air conditioner, 2 ... Compressor, 3 ... Flow path switching valve, 4 ... Outdoor heat exchanger, 5 ... Expansion valve, 6 ... Indoor heat exchanger, 7 ... Suction tank, 8 ... Decompression means, 9 ... Injection Valves, 10 ... main circuit, 11 ... injection piping, 12 ... supercooling heat exchanger, 13 ... supercooling injection valve, 50 ... control unit, 51 ... compressor outlet temperature sensor, 52 ... suction tank inlet temperature sensor, 53 ... Suction tank outlet temperature sensor, 54 ... outdoor heat exchanger temperature sensor, 55 ... indoor heat exchanger temperature sensor

Claims (3)

A cycle passage through which a refrigerant circulates by connecting a compressor, an indoor heat exchanger, an expansion valve, an outdoor heat exchanger, and a suction tank in order by piping;
A pipe positioned between the indoor heat exchanger and the expansion valve or a pipe positioned between the outdoor heat exchanger and the expansion valve and an injection pipe connecting the compressor;
An injection valve provided in the injection pipe;
A compressor outlet temperature sensor for detecting an outlet temperature of the compressor;
A suction tank inlet temperature sensor for detecting the inlet temperature of the suction tank;
A suction tank outlet temperature sensor for detecting the outlet temperature of the suction tank;
Controlling the compressor or the expansion valve so that the temperature detected by the suction tank outlet temperature sensor is higher than the temperature detected by the suction tank inlet temperature sensor;
An air conditioner that controls the injection valve so that a temperature detected by the compressor outlet temperature sensor is equal to or lower than a first predetermined value. A cycle passage through which a refrigerant circulates by connecting a compressor, an indoor heat exchanger, an expansion valve, an outdoor heat exchanger, and a suction tank in order by piping;
A pipe positioned between the indoor heat exchanger and the expansion valve or a pipe positioned between the outdoor heat exchanger and the expansion valve and an injection pipe connecting the compressor;
An injection valve provided in the injection pipe;
A discharge gas temperature sensor for detecting a discharge temperature of the compressor;
A suction tank inlet temperature sensor for detecting the inlet temperature of the suction tank;
A suction tank outlet temperature sensor for detecting an outlet temperature of the suction tank;
An outdoor heat exchanger temperature sensor for detecting the temperature of the outdoor heat exchanger,
Controlling the compressor or the expansion valve so that the temperature detected by the suction tank outlet temperature sensor is higher than the temperature detected by the suction tank inlet temperature sensor;
An air conditioner that controls the injection valve so that a difference between a temperature detected by the compressor outlet temperature sensor and a condensation temperature detected by the outdoor heat exchanger temperature sensor is equal to or less than a second predetermined value. The refrigerant is R32;
When the temperature detected by the compressor outlet temperature sensor is equal to or higher than a third predetermined value, the injection valve opens,
The air conditioner according to claim 1 or 2, wherein the injection valve is closed when a temperature detected by the compressor outlet temperature sensor is smaller than a third predetermined value.