JP2008151394A - Air conditioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize an air conditioner improving a degree of freedom in control of a refrigerating cycle, and capable of stably continuing operation of a compressor. <P>SOLUTION: The compressor 1, an outdoor heat exchanger 2, expansion valves 3, 4, and an indoor heat exchanger 5 are connected by piping circulating a coolant to form the refrigerating cycle, and a control means 9 is provided for controlling a heat exchange amount of the indoor heat exchanger 5 to compose the air conditioner 10. The indoor heat exchanger 5 is formed by providing a plurality of distribution passages 13, 14 connected in parallel with each other, and the expansion valves 3, 4 are respectively provided in the distribution passages 13, 14. In the control means 9, when at least one of a temperature or a pressure of the coolant becomes larger than a set value, one of the expansion valves 3, 4 is closed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an air conditioner that forms a refrigeration cycle.

  In conventional air conditioners, for example, when the indoor air temperature is high during cooling operation, the compressor suction side pressure increases and exceeds the allowable pressure range of the compressor, causing problems such as abnormal stoppage. there were. Similarly, when the outdoor air temperature is high during cooling operation, the pressure on the discharge side of the compressor increases and exceeds the allowable pressure range of the compressor. It was.

  For example, it is known to reduce the compressor capacity by controlling the rotational speed by an inverter, etc., and to reduce the discharge side pressure of the compressor below an allowable value. As a result, the problem remains that the suction pressure of the compressor becomes higher than the allowable suction pressure of the compressor.

  Therefore, as described in Patent Document 1, it is known to forcibly reduce the opening of the expansion valve to reduce the suction pressure of the compressor.

Japanese Patent Laid-Open No. 8-200355

  However, in the technique described in Patent Document 1 described above, there are cases where the operation of the compressor cannot be stably continued.

  That is, for example, when the air temperature inside the room is high, if the expansion valve opening is forcibly throttled, the suction side pressure of the compressor cannot be sufficiently reduced to the allowable pressure range, and the compressor may stop. . In addition, since it is necessary to control in a narrow range of the low opening range with the expansion valve opening reduced, it becomes difficult to control the refrigeration cycle stably when subjected to external changes such as compressor capacity changes. Cases are also conceivable.

  The subject of this invention is improving the freedom degree of control of a refrigerating cycle, and implement | achieving the air conditioner which can continue the driving | operation of a compressor stably.

  In order to solve the above problems, an air conditioner of the present invention forms a refrigeration cycle by connecting a compressor, an outdoor heat exchanger, an expansion valve, and an indoor heat exchanger with a pipe that circulates a refrigerant. Control means for controlling the heat exchange amount of the indoor heat exchanger is provided. The indoor heat exchanger has a plurality of distribution passages connected in parallel, and an expansion valve is provided in each of the distribution passages. At least one of the temperature and pressure of the refrigerant is controlled by the control means. When larger than the set value, a part of the plurality of expansion valves is closed.

  That is, by closing some of the plurality of expansion valves, for example, during cooling operation, the refrigerant does not flow into some of the plurality of distribution channels of the indoor heat exchanger that serves as an evaporator, and the heat exchange area Therefore, the evaporative heat exchange capacity itself is reduced, and the evaporation pressure is reduced. As a result, the suction pressure of the compressor can be reduced. Further, since the refrigerant flow rate is reduced by partially closing the expansion valve, the pressure on the compressor discharge side can be reduced.

  In this manner, by making it possible to control the heat exchange capacity of the indoor heat exchanger, for example, even when the indoor air temperature is high, the intake pressure of the compressor can be controlled within an allowable pressure range, and the outdoor temperature can be controlled. Since the discharge pressure of the compressor can be controlled within the allowable pressure range even when the pressure is high, the operation of the compressor can be continued stably.

  In this case, the temperature of the refrigerant is detected by a temperature detector provided on at least one of the suction side and the discharge side of the compressor, and the pressure of the refrigerant is provided on at least one of the suction side and the discharge side of the compressor. It can be detected by a pressure detector.

  Further, after performing the above-described control, the control means increases the valve opening degree of the closed expansion valve when at least one of the temperature and pressure of the refrigerant becomes equal to or lower than the set value, and enters the normal refrigeration cycle state. Can be returned.

  The control means closes at least one of the plurality of expansion valves and opens at least one of the expansion valves that are not closed when at least one of the temperature and pressure of the refrigerant becomes greater than a set value. The degree can be increased.

  According to this, since the refrigerant flow rate to the evaporator flow path that is not closed is increased, a rapid change in the refrigerant flow rate can be suppressed, and a rapid change in the evaporator capacity can be prevented. Therefore, it is possible to prevent the suction pressure from greatly decreasing transiently and to perform stable pressure control.

  After performing this control, if at least one of the temperature and pressure of the refrigerant falls below the set value, the valve opening of the expansion valve is increased while the valve opening of the closed expansion valve is increased. , And the valve opening degree of both expansion valves can be matched to return to the normal refrigeration cycle state.

  According to this, it is possible to prevent a sudden increase in the refrigerant flow rate to the evaporator due to the opening of the closed expansion valve, to prevent a large increase in the suction pressure transiently, and to enable stable pressure control. .

  Further, the indoor heat exchanger is configured by two distribution flow paths connected in parallel, and an expansion valve is provided in each of the distribution flow paths, and the control means has at least one of the temperature and pressure of the refrigerant at a set value. When it becomes larger, one of the two expansion valves is closed, and the opening degree of the other expansion valve is increased by 1.1 to 2.0 times to suppress a rapid change in the refrigerant flow rate. .

  Further, after this control, when at least one of the temperature and the pressure of the refrigerant becomes equal to or lower than the set value, the valve opening of the closed expansion valve is increased and the valve opening of the other expansion valve is set to 0.1 to It is possible to stably control the refrigeration cycle by reducing the refrigerant flow rate by a factor of 0.9.

  ADVANTAGE OF THE INVENTION According to this invention, the freedom degree of control of a refrigerating cycle can be improved, and the air conditioner which can continue the driving | operation of a compressor stably is realizable.

  Hereinafter, embodiments of an air conditioner to which the present invention is applied will be described with reference to FIGS. This embodiment will be described by taking an air conditioner as an example. Applicable.

  FIG. 1 is a diagram illustrating a refrigeration cycle of an air conditioner according to first to fourth embodiments of the present invention. As shown in FIG. 1, an air conditioner 10 includes a compressor 1, a condenser 2, expansion valves 3 and 4, an evaporator 5, and an accumulator 6, which are sequentially connected by refrigerant piping. Is formed. For example, during the cooling operation, the condenser 2 serves as an outdoor heat exchanger, and the evaporator 5 serves as an indoor heat exchanger. Moreover, when switching to heating operation using a four-way valve (not shown), the indoor heat exchanger becomes the condenser 2 and the outdoor heat exchanger becomes the evaporator 5.

  Further, a pressure sensor 7 for detecting the pressure of the refrigerant on the suction side of the compressor 1 and a pressure sensor 8 for detecting the pressure of the refrigerant on the discharge side are provided, and pressure detection signals from the pressure sensors 7 and 8 are received. Control means 9 for controlling the refrigeration cycle by a microcomputer is provided. A temperature sensor for detecting the temperatures on the suction side and the discharge side of the compressor 1 may be provided, and these detection signals may be input to the control means 9.

  As shown in the figure, the characteristic configuration of the present invention is that the evaporator 5 has two distribution passages 13 and 14 connected in parallel, and each of the distribution passages 13 and 14 has an expansion valve 3. 4 is provided.

  Next, the basic operation of the air conditioner 10 of the present invention will be described. For example, during the cooling operation, the high-temperature and high-pressure refrigerant gas discharged from the compressor 1 condenses in the condenser 2 to become a high-temperature and high-pressure liquid refrigerant, is decompressed by the expansion valves 3 and 4, and is evaporated by the evaporator 5 to become a low temperature. It becomes a low-pressure gas refrigerant and returns to the compressor 1 through the accumulator 6. A predetermined amount of room air that is cooled by exchanging heat with the refrigerant when the refrigerant evaporates is sucked into the evaporator 5 and blown out into the room for cooling. Normally, in this refrigeration cycle, the control means 9 drives the compressor 1 at an operating frequency determined by a control condition such as the room temperature.

  In an air conditioner that performs such an operation, for example, when the temperature of the room with the evaporator 5 and the temperature of the room with the condenser 2 are both high, both the discharge pressure and the suction pressure of the compressor 1 increase. Depending on the case, the case where it deviates from the allowable pressure range of the compressor 1 occurs. For example, when the control means 9 detects from the information from the pressure sensor 8 that the discharge pressure has exceeded the allowable value, the control means 9 performs control to lower the operating frequency of the compressor 1 and lower the discharge pressure. . However, when the room is hot, the suction pressure of the compressor 1 further increases by this control, and the suction pressure may deviate from the allowable range of the compressor 1 and the compressor 1 may be abnormally stopped.

  Hereinafter, the control content of the control means 9 which is the characteristic part of the air conditioner of this invention which solves such a problem is demonstrated based on a specific Example.

  FIG. 2 is a view showing the operation of the expansion valves 3 and 4 controlled by the control means 9. Here, the transition of the valve opening degree of the expansion valves 3 and 4 in the case of performing control to reduce the suction pressure of the compressor 1 is shown. The vertical axis is the valve opening of the expansion valves 3 and 4, and the horizontal axis is time.

  As shown in FIG. 2, when the control means 9 detects that the suction pressure input from the pressure sensor 7 exceeds a predetermined value set in advance, one of the expansion valves 3 and 4, here, As an example, an opening degree at which the expansion valve 3 is closed is given.

  According to this, the distribution flow path 13 of the evaporator 5 is blocked and the refrigerant does not flow, and only the distribution flow path 14 performs heat exchange with the room air, and the heat exchange area is reduced. The exchange capacity itself decreases and the evaporation pressure decreases. As a result, the suction pressure of the compressor 1 can be reduced. Further, since the refrigerant flow rate is reduced by closing the expansion valve 3, the pressure on the discharge side of the compressor 1 can also be reduced. Note that the predetermined value of the suction pressure can be appropriately changed.

  In this way, by controlling the heat exchange capacity of the indoor heat exchanger, in this embodiment the evaporator, for example, the compressor suction pressure can be controlled within the allowable pressure range even when the indoor air temperature is high. it can. Moreover, since the discharge pressure of the compressor can be controlled within the allowable pressure range even when the outdoor temperature is high, the operation of the compressor can be continued stably.

  Next, a second embodiment will be described with reference to FIG. FIG. 3 is also a diagram showing the operation of the expansion valves 3 and 4. As shown in the figure, when the control means 9 detects that the suction pressure input from the pressure sensor 7 exceeds a predetermined value, the control means 9 gives an opening degree at which the expansion valve 3 is closed, and at the same time, the expansion valve 3 4, the opening is forcibly increased in the range of 1.1 to 2 times the opening at that time. In this embodiment, this increase ratio is determined in advance according to the refrigeration cycle.

  According to this, since the refrigerant flow rate to the evaporator flow path that is not closed is increased, a rapid change in the refrigerant flow rate can be suppressed, and a rapid change in the evaporator capacity can be prevented. Therefore, it is possible to prevent the suction pressure from greatly decreasing transiently and to perform stable pressure control.

  Next, a third embodiment will be described with reference to FIG. FIG. 4 is a diagram illustrating the operation of the expansion valves 3 and 4. The present embodiment is an operation example of the expansion valves 3 and 4 when releasing the control for reducing the suction pressure as in the first and second embodiments. When the control means 9 detects from the information from the pressure sensor 7 that the suction pressure has become a predetermined value or less, one of the expansion valves 3, 4, which has been closed, here, for example, the expansion valve 3 is opened. The predetermined opening degree which becomes a valve state is given.

  In this embodiment, since the expansion valves 3 and 4 have the same opening during normal operation, the opening of the expansion valve 3 is adjusted to the expansion valve 4. With the above operation, normal refrigeration cycle control can be restored.

  Next, a fourth embodiment will be described with reference to FIG. FIG. 5 shows the operation of the expansion valves 3 and 4. As in the third embodiment, this embodiment is an example of the operation of the expansion valves 3 and 4 when releasing the control for reducing the suction pressure. When the control means 9 detects from the information from the pressure sensor 7 that the suction pressure is less than or equal to a predetermined value, the control means 9 gives an opening at which the expansion valve 3 is opened, and at the same time, The opening is forcibly decreased in the range of 0.1 to 0.9 times the opening at that time.

  In this embodiment, this reduction ratio is determined in advance according to the refrigeration cycle. Further, the opening degree of the expansion valve 3 is set to match the opening degree of the expansion valve 4 that is forcibly changed. By the control as described above, it is possible to avoid a sudden change in the refrigerant circulation amount, and it is possible to avoid a phenomenon in which the suction pressure excessively rises.

  As mentioned above, although the air conditioner of Examples 1-4 was demonstrated, this invention is not limited to these Examples. For example, the configuration may be such that the evaporator is not divided into two systems but is further divided into a large number and an expansion valve is provided in each distribution flow path.

  In addition to detecting the refrigerant pressure on the suction side of the compressor and controlling the valve opening of the expansion valve as in the above-described embodiment, for example, on the discharge side of the compressor correlated with the refrigerant pressure on the suction side. It is also possible to control the opening degree of the expansion valve by detecting the refrigerant pressure, the refrigerant temperature on the suction side of the compressor, the refrigerant temperature on the discharge side of the compressor, and the like.

  Furthermore, as in the above-described embodiment, it is possible to reduce the suction pressure of the compressor by reducing one of the expansion valves by a predetermined opening degree instead of completely closing.

  Further, the present invention can also be applied to a multi-type air conditioner in which an evaporator or a condenser has a plurality of heat exchangers instead of a one-to-one refrigeration cycle as in the above-described embodiment.

It is a figure which shows the refrigerating cycle of the air conditioner which concerns on Examples 1-4 of this invention. FIG. 6 is a diagram for explaining the operation of the expansion valve of the first embodiment. It is a figure explaining operation | movement of the expansion valve of 2nd Example. It is a figure explaining operation | movement of the expansion valve of 3rd Example. It is a figure explaining operation | movement of the expansion valve of 4th Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Compressor 2 Condenser 3, 4 Expansion valve 5 Evaporator 6 Accumulator 7, 8 Pressure sensor 9 Control means 10 Air conditioner 13, 14 Distribution flow path

Claims (6)

Control means for controlling a heat exchange amount of the indoor heat exchanger by connecting a compressor, an outdoor heat exchanger, an expansion valve, and an indoor heat exchanger with piping for circulating a refrigerant to form a refrigeration cycle. In the air conditioner provided,
The indoor heat exchanger has a plurality of distribution passages connected in parallel, and each of the distribution passages is provided with the expansion valve,
The control unit closes a part of the plurality of expansion valves when at least one of a temperature and a pressure of the refrigerant becomes larger than a set value. The temperature of the refrigerant is detected by a temperature detector provided on at least one of the suction side and the discharge side of the compressor, and the pressure of the refrigerant is provided on at least one of the suction side and the discharge side of the compressor. The air conditioner according to claim 1, wherein the air conditioner is detected by a pressure detector. The control means closes at least one of the plurality of expansion valves when at least one of the temperature and pressure of the refrigerant is greater than a set value, and at least one of the expansion valves not closed The air conditioner according to claim 1, wherein the opening degree is increased. 2. The air conditioner according to claim 1, wherein the control unit increases a valve opening degree of the closed expansion valve when at least one of a temperature and a pressure of the refrigerant becomes a set value or less. The control means increases the valve opening of the closed expansion valve and opens the valve of the expansion valve that has increased the valve opening when at least one of the temperature and the pressure of the refrigerant falls below a set value. The air conditioner according to claim 3, wherein the air conditioner is lowered to make the valve openings of both expansion valves coincide. The indoor heat exchanger has two distribution channels connected in parallel, and each of the distribution channels is provided with the expansion valve,
The control means closes one of the two expansion valves when at least one of the temperature and pressure of the refrigerant is larger than a set value, and sets the valve opening of the other expansion valve to 1.1 to 2 Increase by a factor of 0,
When at least one of the temperature and pressure of the refrigerant falls below a set value, the valve opening of the closed expansion valve is increased and the valve opening of the other expansion valve is increased by 0.1 to 0.9 times The air conditioner according to claim 1, wherein the air conditioner is lowered.

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