JP2005345069A - Air conditioner and its operation control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an air conditioner capable of keeping a proper overcooling degree. <P>SOLUTION: This air conditioner for conditioning the air in a room by circulating a refrigerant compressed by a compressor 1 between an indoor heat exchanger 6 and an outdoor heat exchanger 20, comprises an electronic expansion valve 33 for throttling a part of the refrigerant from the outdoor heat exchanger 20, an overcooling heat exchanger 17 for cooling the refrigerant from the outdoor heat exchanger by the throttle refrigerant, a pressure meter (pressure detecting means) 31 for detecting an inlet-side refrigerant pressure of the compressor 1, a thermistor (temperature detecting means) 30 for detecting an inlet-side refrigerant temperature of the compressor 1, and a control part 35 for controlling the electronic expansion valve 33 on the basis of the detection outputs of the pressure meter 31 and the thermistor 30 to control the overcooling degree in the overcooling heat exchanger 17. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an air conditioner and an operation control method thereof, and more particularly, to an air conditioner with supercooling control and an operation control method thereof.

FIG. 2 shows a refrigerant circuit diagram of a conventional air conditioner disclosed in Patent Document 1 below. The air conditioner includes an outdoor unit 22 and an indoor unit 23.
The outdoor unit 22 includes a compressor 1 that compresses a refrigerant, a four-way valve 2 that switches a refrigerant flow path between a cooling operation and a heating operation, an outdoor heat exchanger 20 that exchanges heat between outdoor air and the refrigerant, and a gas-phase refrigerant. And an accumulator 21 for feeding the compressor 1 to the compressor 1.
The indoor unit 23 includes an indoor heat exchanger 6 that performs indoor air conditioning by exchanging heat between the refrigerant and room air, and an expansion mechanism 9 that throttles the refrigerant during heating operation.

  The outdoor unit 22 and the outdoor unit 23 are connected by connecting the indoor / outdoor connection pipes 4, 12 between the pipe joints 3, 5, 11, 13.

  During the cooling operation, the high-temperature and high-pressure refrigerant gas discharged from the compressor 1 enters the outdoor heat exchanger 20 via the four-way valve 2. Here, the heat is dissipated and condensed to form a high-pressure liquid refrigerant, and the circuit passes through the distribution pipes 19 a, 19 b, 19 c for each circuit and is merged by the distributor 18 and enters the supercooling heat exchanger 17. The high pressure liquid refrigerant is supercooled by the supercooling heat exchanger 17. That is, the refrigerant depressurized and cooled by the flow rate adjusting pipe 16 is caused to flow through the supercooling heat exchanger 17, thereby supercooling the high-pressure refrigerant. The refrigerant enters the expansion mechanism 15 after being supercooled. The pressure is reduced by the expansion mechanism 15 to become a low-pressure / low-temperature liquid-gas two-phase refrigerant, and enters the distributor 8 through the pipe joint 13, the indoor / outdoor connection pipe 12, the pipe joint 11, and the check valve 10. The refrigerant is distributed by the distributor 8 and enters the indoor heat exchanger 6 through distribution pipes 7a and 7b. Here, the heat is absorbed and evaporated, and enters the accumulator 21 through the pipe joint 5, the indoor / outdoor connection pipe 4, the pipe joint 3, and the four-way valve 2. Here, the liquid non-evaporated refrigerant accumulates in the lower part, and the separated gas refrigerant is sucked into the compressor 1 through the suction pipe 28 and compressed.

  Furthermore, a technique for adjusting the degree of supercooling based on the suction side temperature and the suction side pressure of the compressor using a flow rate adjustment valve instead of the flow rate adjustment pipe 16 is disclosed (paragraph [0026] and FIG. 2). . That is, the degree of supercooling is adjusted so that the degree of superheat obtained by the suction side temperature and the suction side pressure is constant.

As described above, the air conditioner disclosed in Patent Document 1 uses the expansion mechanism 15 provided in the outdoor unit 22 to convert the liquid-gas two-phase refrigerant into the liquid-gas two-phase refrigerant and then sends the refrigerant to the indoor unit 23. Even if it becomes longer, it has the advantage that the amount of additional refrigerant is reduced.
Further, since the supercooling degree is adjusted using the flow rate adjusting valve so that the suction superheat degree is constant, there is an advantage that a wide range of operation is possible.

JP-A-5-256527 (paragraphs [0021] to [0026], FIGS. 1 and 2)

However, in the case where a system in which high-pressure refrigerant is squeezed by an expansion valve provided on the indoor unit 23 side without using the expansion mechanism 15 employed in the air conditioner described in Patent Document 1, the interior of the indoor / outdoor connection pipe 12 is used. The liquid phase refrigerant will flow. When the plurality of indoor units 23 are arranged with the head difference h as shown in FIG. 4, pressure loss based on the head difference h occurs. This pressure loss is about 101 kPa per 10 m. Thus, in the case of liquid refrigerant, a pressure loss that cannot be ignored is caused by the head difference h.
When pressure loss occurs, as shown in the ph diagram of FIG. 3, the pressure difference is reduced as indicated by symbol a in FIG. The degree of cooling is lost, and the liquid refrigerant flashes (becomes mixed with gas). For this reason, the expansion valve cannot perform sufficient throttling, and the cooling capacity is reduced. Further, noise is generated due to rapid expansion by the expansion valve.

On the other hand, as shown in FIG. 4, in the case of a multi-type air conditioner in which a plurality of indoor units 23 are connected to one outdoor unit 22, supercooling is performed in accordance with the outdoor unit 22 having a large head difference h. Then, the degree of supercooling becomes too large for the indoor unit 23 having a small head difference h.
In this case, the refrigerant cannot completely evaporate in the indoor heat exchanger 6, and a liquid back phenomenon occurs in which the liquid returns to the compressor 1, thereby reducing the life of the compressor 1.

  The present invention has been made in view of the above circumstances, and for a multi-type air conditioner equipped with a plurality of indoor units having head differences, the air conditioning capacity is improved by maintaining an appropriate degree of supercooling, and the compression is performed. An object of the present invention is to provide an air conditioner capable of improving the reliability of a machine.

In the present invention, the following means are adopted in order to solve the above problems.
The invention described in claim 1 includes an outdoor unit having a compressor that compresses refrigerant, an outdoor heat exchanger that exchanges heat between the refrigerant and outdoor air, an expansion valve that expands the refrigerant, and refrigerant and indoor air. A plurality of indoor units having an indoor heat exchanger for exchanging heat with each other, and in the air conditioner in which the outdoor unit and the indoor unit are arranged at different heights, discharge from the outdoor heat exchanger An electronic expansion valve that squeezes a part of the refrigerant, a supercooling heat exchanger that cools the refrigerant discharged from the outdoor heat exchanger by the squeezed refrigerant, and detects the refrigerant pressure on the inlet side of the compressor Pressure detecting means for detecting, temperature detecting means for detecting the refrigerant temperature on the inlet side of the compressor, and the supercooling heat exchange by controlling the electronic expansion valve based on detection outputs of the pressure detecting means and the temperature detecting means. In a vessel Characterized by comprising a control unit for adjusting the degree of subcooling.

  During the cooling operation, the refrigerant compressed in the outdoor unit and condensed and liquefied in the outdoor heat exchanger is sent to the indoor units of different heights in the liquid state and expanded by the expansion valve. Guided to heat exchanger. The outdoor unit and the indoor unit are installed at different heights, and a pressure loss due to a head difference that cannot be ignored is added to the liquid refrigerant. In the present invention, in consideration of the pressure loss of the liquid refrigerant, for example, the degree of superheat of the refrigerant on the compressor inlet side is obtained from the inlet side pressure (low pressure) and the temperature of the compressor. The supercooling degree in the supercooling heat exchanger is adjusted so that this superheating degree is appropriate.

  The invention described in claim 2 includes an outdoor unit having a compressor that compresses refrigerant, an outdoor heat exchanger that exchanges heat between the refrigerant and outdoor air, an expansion valve that expands the refrigerant, and refrigerant and indoor air. A plurality of indoor units having an indoor heat exchanger for exchanging heat with each other, wherein the outdoor unit and the indoor unit are disposed at different heights in the operation control method of the air conditioner, wherein the compressor The refrigerant pressure and the refrigerant temperature on the inlet side of the refrigerant are detected, and the degree of supercooling in the supercooling heat exchanger is adjusted by controlling the throttle amount of the electronic expansion valve based on these detection results.

  In the present invention, for example, the degree of superheat of the refrigerant on the compressor inlet side is obtained from the inlet side pressure (low pressure) and the temperature of the compressor. The supercooling degree in the supercooling heat exchanger is adjusted so that this superheating degree is appropriate.

  By adjusting the degree of supercooling in the supercooling heat exchanger, it is possible to maintain an appropriate degree of supercooling even in an installation environment having a head difference between the outdoor unit and the indoor unit. And the reliability of the compressor can be improved.

Next, embodiments of the present invention will be described with reference to the drawings. In addition, about the structure which is common in the air conditioning apparatus shown in FIG. 2 which is a prior art, the same code | symbol is attached | subjected and the description is abbreviate | omitted.
The air conditioner according to the present embodiment includes one outdoor unit 22 and a plurality of indoor units 23, 23... Connected to the outdoor unit 22. In FIG. 1, only one indoor unit 23 is shown for easy understanding. Actually, as shown in FIG. 4, the plurality of indoor units 23 are installed at different heights from the outdoor unit 22. Each indoor unit 23 is installed in each room on each floor of a building, for example.
The outdoor unit 22 and each outdoor unit 23 are connected by connecting the indoor / outdoor connection pipes 4, 12 between the pipe joints 3, 5, 11, 13.
The indoor / outdoor connection pipe 12 provided between the supercooling heat exchanger 17 of the outdoor unit 22 and the indoor electronic expansion valve 40 of the indoor unit 23 is a pipe through which liquid refrigerant flows.

The outdoor unit 22 includes a compressor 1 that compresses a refrigerant, a four-way valve 2 that switches a refrigerant flow path between a cooling operation and a heating operation, an outdoor heat exchanger 20 that exchanges heat between outdoor air and the refrigerant, and a gas-phase refrigerant. And an accumulator 21 for feeding the compressor 1 to the compressor 1.
The indoor unit 23 includes an indoor heat exchanger 6 that performs indoor air conditioning by exchanging heat between the refrigerant and room air, and an indoor electronic expansion valve 40 that squeezes and expands the refrigerant.

The outdoor unit 22 is provided with a thermistor (temperature detection means) 30 for detecting the refrigerant temperature on the inlet side of the compressor 1 and a pressure gauge 31 for detecting the refrigerant pressure on the inlet side of the compressor 1.
In addition, an electronic expansion valve 33 that throttles the refrigerant flowing into the supercooling heat exchanger 17 is provided.
Furthermore, a control unit 35 is provided that receives the outputs of the thermistor 30 and the pressure gauge 31 and controls the electronic expansion valve 33 based on these output values.

  The controller 35 calculates a saturation temperature from the refrigerant pressure on the inlet side of the compressor 1 during operation, and calculates a superheat degree SH (see FIG. 3) based on the saturation temperature and the temperature detected by the thermistor 30. Based on the degree of superheat SH thus obtained, the electronic expansion valve 33 is adjusted so that the degree of supercooling in the supercooling heat exchanger 17 becomes an appropriate value.

  Specifically, first, before installing the air conditioner, a reference supercooling degree is set, and the opening degree of the electronic expansion valve 33 is initially set. In actual installation, an appropriate degree of supercooling varies depending on the head difference h, the number of operating units, the pipe length, and the like. For this reason, the air conditioner is operated and the degree of supercooling in the supercooling heat exchanger 17 is adjusted according to the state of the refrigerant on the inlet side of the compressor 1. For example, when the degree of supercooling is insufficient, the refrigerant returns to the compressor 1 in an overheated state. When the degree of supercooling is too large, the refrigerant cannot be completely evaporated in the indoor heat exchanger 6 and returns to the compressor 1 in the liquid back state. The control unit 35 controls the electronic expansion valve 33 so that the state of the refrigerant on the inlet side of the compressor 1, that is, the superheat degree SH becomes an appropriate value (for example, 20 ° C.), and the supercooling degree in the supercooling heat exchanger 17 is controlled. adjust.

  In the air conditioning apparatus of the present embodiment adjusted as described above, the high-temperature and high-pressure refrigerant gas discharged from the compressor 1 enters the outdoor heat exchanger 20 via the four-way valve 2 during the cooling operation. Here, it dissipates heat and condenses to become a high-pressure liquid refrigerant, passes through the distribution pipes 19a, 19b, and 19c for each circuit, joins in the distributor 18, and enters the supercooling heat exchanger 17. The high pressure liquid refrigerant is supercooled by the supercooling heat exchanger 17. In other words, the refrigerant that has been partially removed from the outdoor heat exchanger 20 and depressurized and cooled by the electronic expansion valve 33 is allowed to flow through the supercooling heat exchanger 17, thereby supercooling the high-pressure refrigerant. The

  The refrigerant flowing through the supercooling heat exchanger 17 obtains an appropriate degree of supercooling according to the installation / operating conditions such as the head difference h of each indoor unit 23, and the pipe joint 13, the indoor / outdoor connection pipe 12, and the pipe joint. It passes through the section 11 and is led to the indoor unit 23. The refrigerant flowing through the indoor / outdoor connection pipe 12 is pumped up to the indoor unit 23 in a liquid phase state. Therefore, when the liquid refrigerant flows through the indoor / outdoor connection pipe 12, a pressure loss corresponding to the head difference is given.

  The refrigerant flowing into the indoor unit 23 is throttled by the indoor electronic expansion valve 40 and then enters the distributor 8. The refrigerant is distributed by the distributor 8 and enters the indoor heat exchanger 6 through distribution pipes 7a and 7b. In the indoor heat exchanger 6, the refrigerant evaporates by absorbing heat from room air, and then enters the accumulator 21 through the pipe joint 5, the indoor / outdoor connection pipe 4, the pipe joint 3, and the four-way valve 2. Here, the liquid non-evaporated refrigerant is accumulated in the lower part, and the separated gas refrigerant is sucked into the compressor 1 through the suction pipe 28 and compressed.

  Thus, according to the air conditioner according to the present embodiment, there is a head difference because the height of the outdoor unit 22 and each indoor unit 23 is different, and the pressure loss in the indoor / outdoor connection pipe 12 through which the liquid refrigerant flows is reduced. Even if it is not negligible, the degree of supercooling is adjusted using the temperature and pressure on the suction side of the compressor 1 so that the degree of superheating is constant. An appropriate degree of supercooling can be set for the state, and stable operation is possible. That is, the capacity of the indoor unit is improved and the reliability of the compressor is improved.

Further, as a modification of the present embodiment, a refrigerant circuit in which the diameter of the expansion valve that governs the control flow rate is set smaller than a normal one, and an electromagnetic valve and a fixed throttle (capillary) are provided in parallel with the electronic expansion valve. The arrangement to arrange can also be adopted.
Thereby, even if it is a case where it falls below the control range of an expansion valve in control of an indoor heat exchanger exit superheat degree, supercooling adjustment is attained.
Specifically, if the degree of superheat at the outlet of the indoor heat exchanger is small and the expansion valve opening is close to the lower limit value, the supercooling may be too large by closing the solenoid valve and performing superheat control only with the expansion valve. It becomes possible to respond. In addition, when the head difference is large and supercooling is required, it is possible to provide a device that can cope with the magnitude of supercooling by adopting a configuration in which an expansion valve and a fixed throttle are used together.

It is the figure which showed the refrigerant circuit of the air conditioning apparatus shown as one Embodiment of this invention. It is the figure which showed the refrigerant circuit of the conventional air conditioning apparatus. It is a ph diagram of the refrigerating cycle in the air harmony device. It is the figure shown about the head difference of an indoor unit and an outdoor unit.

Explanation of symbols

1 Compressor 17 Supercooling heat exchanger 30 Thermistor (temperature detection means)
31 Pressure gauge (pressure detection means)
33 Electronic expansion valve 35 Control unit

Claims (2)

Compressor for compressing refrigerant, outdoor unit having outdoor heat exchanger for exchanging heat between refrigerant and outdoor air, expansion valve for expanding refrigerant, and room for heat exchange between refrigerant and indoor air A plurality of indoor units having a heat exchanger, and an air conditioner in which these outdoor units and indoor units are arranged at different heights,
In the outdoor unit,
An expansion valve that squeezes a part of the refrigerant discharged from the outdoor heat exchanger, a supercooling heat exchanger that cools the refrigerant discharged from the outdoor heat exchanger by the squeezed part of the refrigerant,
Pressure detecting means for detecting an inlet side refrigerant pressure of the compressor;
Temperature detecting means for detecting the refrigerant temperature on the inlet side of the compressor is provided,
An air conditioner comprising: a control unit that adjusts the degree of supercooling in the supercooling heat exchanger by controlling the expansion valve based on the detection output of the pressure detecting means and the temperature detecting means. Compressor for compressing refrigerant, outdoor unit having outdoor heat exchanger for exchanging heat between refrigerant and outdoor air, expansion valve for expanding refrigerant, and room for heat exchange between refrigerant and indoor air A plurality of indoor units having a heat exchanger, and in an operation control method of an air conditioner in which these outdoor units and indoor units are arranged at different heights,
The refrigerant pressure and refrigerant temperature on the inlet side of the compressor are detected, and the degree of supercooling in the supercooling heat exchanger is adjusted by controlling the throttle amount of the electronic expansion valve based on the detection results. An operation control method for the air conditioner.

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