WO2011070954A1

WO2011070954A1 - Air conditioner and refrigerant amount detection method for air conditioner

Info

Publication number: WO2011070954A1
Application number: PCT/JP2010/071481
Authority: WO
Inventors: 隆博加藤; 篤塩谷
Original assignee: 三菱重工業株式会社
Priority date: 2009-12-10
Filing date: 2010-12-01
Publication date: 2011-06-16
Also published as: JP2011122767A; CN102472542B; EP2511630A4; CN102472542A; EP2511630B1; JP5582773B2; EP2511630A1

Abstract

Provided are an air conditioner and refrigerant amount detection method for an air conditioner, which make it possible to constantly detect the amount of charged refrigerant with high accuracy without a heating means specially provided in a liquid level detecting circuit and even under low external temperature. An air conditioner (1), which is provided with a supercooling circuit (20), comprises: a first liquid level detecting circuit (40) which connects one position at a predetermined height inside a receiver (15) to the inlet side of a compressor (10) via the supercooling circuit (20); a second liquid level detecting circuit (45) which is branched from a bypass circuit (41) of the first liquid level detecting circuit (40) and acts as a bypass for leading, to the supercooling circuit (20), the refrigerant that has been taken out from the receiver (15); a temperature detecting unit (44) which detects the temperature of the refrigerant that has been depressurized by passing through the first liquid level detecting circuit (40) or the second liquid level detecting circuit (45); and a refrigerant amount detecting unit (48) which detects, by the temperature detecting unit (44), the post-depressurization temperature of the refrigerant that has been taken out from the receiver (15) via the first liquid level detecting circuit (40) or the second liquid level detecting circuit (45), and determines the amount of charged refrigerant on the basis of the thus detected temperature.

Description

Air conditioner and refrigerant amount detection method for air conditioner

The present invention relates to an air conditioner that can always be filled with an optimum amount of refrigerant at the time of installation, and a refrigerant amount detection method for the air conditioner.

A multi-type air conditioner used for air conditioning of buildings and the like includes a compressor, a four-way switching valve, an outdoor heat exchanger, an expansion valve for heating, a receiver and an outdoor fan, an indoor heat exchanger, A plurality of indoor units including a cooling expansion valve, an indoor fan, and the like are connected locally by gas refrigerant pipes and liquid refrigerant pipes. In such an air conditioner, a pipe length that connects between the outdoor unit and the indoor unit when the outdoor unit is preliminarily filled with a predetermined amount of refrigerant and the air conditioner is installed in the field and then trial run is performed. In addition, an insufficient amount of refrigerant is additionally charged according to the number of indoor units connected.

In such an air conditioner, in order to always be able to charge an appropriate amount of refrigerant without depending on the local construction level, the amount of refrigerant to be added is always stored in the receiver in the refrigerant circuit during the refrigerant charging operation. A liquid level detection circuit is provided for detecting that the incoming liquid refrigerant has reached a predetermined liquid level, and the liquid level detection circuit detects that the liquid refrigerant of the predetermined liquid level has accumulated in the receiver. Thus, Patent Documents 1 and 2 disclose techniques for determining that a necessary amount of refrigerant is filled in the refrigerant circuit.

This Patent Document 1 shows a technique in which a bypass circuit is connected from the predetermined height position of the receiver to the compressor suction side, and an on-off valve, a pressure reducing mechanism, and a temperature detection unit are provided in the bypass circuit. Further, Patent Document 2 is provided with an on-off valve, a pressure reducing mechanism, a heating unit, and a temperature detection unit in the bypass circuit. When the saturated gas refrigerant is taken out from the receiver to the bypass circuit, When the liquid refrigerant is taken out, the refrigerant temperature after depressurization is measured, and the refrigerant amount is determined by detecting that the liquid refrigerant of the predetermined liquid level has accumulated in the receiver from the temperature difference. Show the technology.

JP 2002-350014 A (see FIG. 1) Japanese Patent No. 3719246 (see FIG. 1)

However, in the case of the technique disclosed in Patent Document 1, the outside air temperature is high, the discharge side pressure (high pressure) of the compressor is high, and the slope of the saturated gas line on the pressure-enthalpy diagram increases to the left. Under pressure conditions, a gas-liquid two-phase state may occur when a saturated gas refrigerant is taken out and decompressed. In this case, a sudden temperature drop of the refrigerant is detected, and it may be erroneously determined that the liquid refrigerant has reached a predetermined liquid level, and there is a problem that the detection accuracy cannot be ensured.

On the other hand, in the technique disclosed in Patent Document 2, in order to solve the above problem, the liquid level detection circuit is provided with heating means for heating the refrigerant decompressed by the decompression mechanism, and the refrigerant taken out from the receiver is in a gas state. The temperature rise due to heating is large, and in the liquid state, the heat energy from heating is consumed as latent heat of evaporation and the temperature rise is small, so that a sufficient temperature difference can be secured to improve detection accuracy. I have to. However, since it is indispensable to install a heating means in the liquid level detection circuit, there is a problem that the configuration becomes complicated. Also, in any of the techniques disclosed in Patent Documents 1 and 2, if the discharge side pressure (high pressure) is not sufficiently increased at low outside air temperature, the degree of superheat of the gas refrigerant taken out from the receiver cannot be secured, and detection is performed. The problem of reduced accuracy is inherent.

The present invention has been made in view of such circumstances, and is an air that can always detect the refrigerant charging amount with high accuracy without providing any special heating means in the liquid level detection circuit and even under low outside air temperature conditions. It aims at providing the refrigerant | coolant amount detection method of a conditioner and an air conditioner.

In order to solve the above-described problems, the air conditioner and the refrigerant amount detection method for the air conditioner of the present invention employ the following means.
That is, the air conditioner according to the first aspect of the present invention shunts a compressor, a compressor, an outdoor heat exchanger, a heating expansion valve, a receiver that stores liquid refrigerant, and a part of the liquid refrigerant, An outdoor unit equipped with a supercooling circuit, etc., which exchanges heat with liquid refrigerant in a supercooling heat exchanger and returns to the suction side of the compressor after decompressing the refrigerant with a decompression mechanism, an indoor heat exchanger, and an expansion valve for cooling In an air conditioner that configures a closed-cycle refrigerant circuit by connecting an indoor unit equipped with a gas refrigerant pipe and a liquid refrigerant pipe to the indoor unit including the receiver and the like via the predetermined height position of the receiver and the supercooling circuit A first liquid level detection circuit having an on-off valve and a pressure reducing mechanism interposed in a bypass circuit connecting to the suction side of the compressor; and a refrigerant branched from the bypass circuit and taken out from the receiver Bypass to the inlet side of the decompression mechanism A second liquid level detection circuit provided with a valve closing; and a temperature detection unit that detects the temperature of the refrigerant decompressed through the first liquid level detection circuit or the supercooling circuit including the second liquid level detection circuit; The temperature detection unit detects the temperature after depressurization of the refrigerant taken out from the receiver via the first liquid level detection circuit or the second liquid level detection circuit, and determines the refrigerant filling amount based on the temperature And a refrigerant amount detection unit.

In the air conditioner according to the first aspect, a bypass circuit connecting a predetermined height position of the receiver and a suction side of the compressor via a supercooling circuit is provided with an opening / closing valve and a pressure reducing mechanism. A liquid level detection circuit; a second liquid level detection circuit including an on-off valve that bypasses the refrigerant branched from the bypass circuit and taken out from the receiver to the inlet side of the decompression mechanism of the supercooling circuit; and the first liquid level detection A temperature detection unit that detects the temperature of the decompressed refrigerant through the circuit or the subcooling circuit including the second liquid level detection circuit, and the first liquid level detection circuit or the second liquid level detection circuit that is taken out from the receiver A refrigerant amount detection unit that detects the temperature of the refrigerant after being depressurized by a temperature detection unit and determines a refrigerant charge amount based on the temperature; Therefore, under a temperature condition of about the cooling rating, by flowing the refrigerant from the receiver into the first liquid level detection circuit, when the saturated gas refrigerant is taken out from the receiver, and when the saturated liquid refrigerant is taken out, It is possible to detect the refrigerant temperature after depressurization and reliably detect that the liquid refrigerant of a predetermined liquid level has accumulated in the receiver from the temperature difference. On the other hand, under low outside air temperature conditions, when the pressure of the receiver decreases due to a decrease in high pressure and saturated gas refrigerant is taken out, it is not possible to secure a sufficient degree of superheat even if the refrigerant temperature after decompression is detected. There was a possibility that the liquid refrigerant could not be distinguished from the case where it was taken out and could be misjudged. However, even under such conditions, the saturated gas refrigerant taken out from the receiver was excessively passed through the second liquid level detection circuit. By flowing into the cooling circuit, heat is exchanged with the liquid refrigerant in the supercooling heat exchanger and heating is performed, and the degree of superheat can be sufficiently increased.Therefore, the predetermined liquid level is set in the receiver from the temperature difference from when the saturated liquid refrigerant is taken out. It is possible to reliably detect that the liquid refrigerant has accumulated. Therefore, it is possible to detect the refrigerant charge amount with high accuracy by ensuring sufficient temperature difference under a wide range of temperature conditions without being affected by high pressure fluctuations due to outside air temperature, etc. It becomes possible to fill the amount of refrigerant and to stably operate the air conditioner. Further, since the refrigerant can be heated using the supercooling circuit, it is not necessary to provide a heating means specially on the first liquid level detection circuit side, and the configuration can be simplified.

An air conditioner according to a second aspect of the present invention is the air conditioner described above, wherein the air conditioner is closed in the vicinity of a branch portion from the refrigerant circuit of the supercooling circuit during the refrigerant charging operation and opened during the normal air conditioning operation. An electromagnetic on-off valve is provided.

The air conditioner according to the second aspect is provided with an electromagnetic on-off valve that is closed during the refrigerant charging operation and opened during the normal cooling / heating operation near the branch portion from the refrigerant circuit of the supercooling circuit. Therefore, it is possible to easily switch between the refrigerant charging operation and the normal cooling / heating operation only by opening / closing the electromagnetic opening / closing valve. Therefore, the supercooling circuit can be used in combination as a liquid level detection circuit during the refrigerant charging operation, in addition to the improvement in the capacity during the normal operation, and can contribute to an improvement in the detection accuracy of the refrigerant filling amount.

An air conditioner according to a third aspect of the present invention includes an outdoor unit including a compressor, an outdoor heat exchanger, a heating expansion valve, and a receiver for storing liquid refrigerant, an indoor heat exchanger, and a cooling expansion valve. Are connected to each other by a gas refrigerant pipe and a liquid refrigerant pipe to form a closed-cycle refrigerant circuit, the predetermined height position of the receiver and the suction side of the compressor A liquid level detection circuit having an on-off valve and a pressure reducing mechanism interposed in a bypass circuit connecting between them, and an on-off valve and a pressure reducing mechanism capable of introducing a part of hot gas from the discharge side to the suction side of the compressor A hot gas bypass circuit, a temperature detection unit capable of detecting the temperature of the refrigerant that has passed through the liquid level detection circuit or a mixture of the refrigerant and the hot gas introduced through the hot gas bypass circuit, and the receiver in front A temperature after decompression of the refrigerant taken out by the liquid level detection circuit or a mixed refrigerant of the refrigerant and the refrigerant introduced through the hot gas bypass circuit is detected by the temperature detection unit, and the refrigerant filling amount based on the temperature A refrigerant amount detection unit for determining whether or not.

According to the air conditioner according to the third aspect, a liquid level detection circuit including an open / close valve and a pressure reducing mechanism in a bypass circuit connecting between a predetermined height position of the receiver and the suction side of the compressor; A hot gas bypass circuit having an on-off valve and a pressure reducing mechanism capable of introducing a part of hot gas from the discharge side to the suction side of the compressor, and the refrigerant passing through the liquid level detection circuit or the refrigerant and the hot gas bypass circuit The temperature detection unit capable of detecting the temperature of the refrigerant mixed with the introduced hot gas, and the refrigerant taken out from the receiver to the liquid level detection circuit or the refrigerant and the refrigerant introduced via the hot gas bypass circuit A refrigerant amount detection unit that detects the temperature of the refrigerant after being depressurized by a temperature detection unit and determines a refrigerant charge amount based on the temperature; Therefore, under the temperature condition of about the cooling rating, the refrigerant temperature after decompression is detected when the saturated gas refrigerant is taken out from the receiver to the liquid level detection circuit and when the saturated liquid refrigerant is taken out, respectively. From the temperature difference, it can be detected that liquid refrigerant of a predetermined liquid level has accumulated in the receiver. On the other hand, under low outside air temperature conditions, when the pressure in the receiver decreases due to a decrease in high pressure and saturated gas refrigerant is taken out, the degree of superheat cannot be secured even if the refrigerant temperature after decompression is detected. Although it could not be distinguished from the case where the liquid refrigerant was taken out, there was a possibility of erroneous determination, but even under such conditions, the saturated gas refrigerant taken out from the receiver was introduced via the hot gas bypass circuit. Heating is performed by mixing hot gas, and a sufficient degree of superheat can be secured, so that it is possible to detect that liquid refrigerant of a predetermined liquid level has accumulated in the receiver from the temperature difference from when saturated liquid refrigerant is taken out. . Therefore, the refrigerant charge amount can be detected with high accuracy by sufficiently ensuring the temperature difference under a wide range of temperature conditions without being affected by fluctuations in high pressure due to the outside air temperature, and there is no excess or deficiency. It is possible to fill the optimal amount of refrigerant and to stably operate the air conditioner.

The refrigerant quantity detection method for an air conditioner according to a fourth aspect of the present invention is the above-described refrigerant quantity detection method for an air conditioner, wherein the second liquid level is measured under a temperature condition of a cooling rating during the refrigerant charging operation. A detection circuit is closed by the on-off valve and the first liquid level detection circuit is used. Under a low outside air temperature condition, the first liquid level detection circuit is closed by the on-off valve, and the second liquid level detection circuit The liquid level is detected by using each of the above.

According to the fourth aspect, in the air conditioner described above, the second liquid level detection circuit is closed by the on-off valve and the first liquid level detection circuit is closed under the temperature condition of the cooling rating during the refrigerant charging operation. In use, under a low outside air temperature condition, the first liquid level detection circuit is closed by an on-off valve, and the liquid level detection is performed using the second liquid level detection circuit. As a result, the saturated gas refrigerant is taken out under a wide range of temperature conditions by using either the first liquid level detection circuit or the second liquid level detection circuit without being influenced by the outside air temperature. From the temperature difference from the case where the saturated liquid refrigerant is taken out, it is possible to detect that the liquid refrigerant of the predetermined liquid level has accumulated in the receiver, and to detect the refrigerant filling amount with high accuracy. Therefore, it is possible to fill the optimum amount of refrigerant with no excess or deficiency with respect to the air conditioner.

The refrigerant quantity detection method for an air conditioner according to a fifth aspect of the present invention is the above-described refrigerant quantity detection method for an air conditioner, wherein the liquid level detection circuit is used in a refrigerant charging operation under a temperature condition of about a cooling rating. The liquid level detection is performed using both the liquid level detection circuit and the hot gas bypass circuit under a low outside air temperature condition.

According to the fifth aspect, in the air conditioner described above, only the liquid level detection circuit is used under the temperature condition of the cooling rating during the refrigerant charging operation, and the liquid level detection circuit is used under the low outside air temperature condition. And the hot gas bypass circuit are used to detect the liquid level. As a result, when saturated gas refrigerant is taken out under a wide range of temperature conditions by using either the liquid level detection circuit or the liquid level detection circuit and the hot gas bypass circuit, regardless of the outside air temperature. And when the saturated liquid refrigerant is taken out, it can be detected that the liquid refrigerant of a predetermined liquid level has accumulated in the receiver, and the refrigerant filling amount can be detected with high accuracy. Therefore, it is possible to fill the optimum amount of refrigerant with no excess or deficiency with respect to the air conditioner.

According to the air conditioner and the refrigerant amount detection method of the air conditioner of the present invention, the saturated gas refrigerant is taken out from the receiver by flowing the refrigerant from the receiver into the first liquid level detection circuit under a temperature condition of about the cooling rating. And when the saturated liquid refrigerant is taken out, it is possible to detect the refrigerant temperature after depressurization and reliably detect that the liquid refrigerant of a predetermined liquid level has accumulated in the receiver from the temperature difference. it can. On the other hand, under a low outside air temperature condition, the saturated gas refrigerant taken out from the receiver flows into the supercooling circuit via the second liquid level detection circuit, so that heat is exchanged with the liquid refrigerant in the supercooling heat exchanger. In addition, since the degree of superheat can be sufficiently increased, it is possible to reliably detect that the liquid refrigerant of a predetermined liquid level has accumulated in the receiver from the temperature difference from the case where the saturated liquid refrigerant is taken out. As a result, the refrigerant charge amount can be detected with high accuracy by ensuring a sufficient temperature difference under a wide range of temperature conditions without being affected by fluctuations in high pressure due to the outside air temperature, and there is no excess or deficiency. It is possible to fill the optimal amount of refrigerant and to stably operate the air conditioner. Further, since the refrigerant can be heated using the supercooling circuit, it is not necessary to provide a heating means specially on the first liquid level detection circuit side, and the configuration can be simplified.

Further, according to the air conditioner and the air conditioner refrigerant amount detection method of the present invention, under the temperature condition of the cooling rating, when the saturated gas refrigerant is taken out from the receiver to the liquid level detection circuit, When the liquid refrigerant is taken out, it is possible to detect the refrigerant temperature after depressurization and to detect that a predetermined level of liquid refrigerant has accumulated in the receiver from the temperature difference. On the other hand, under low outside air temperature conditions, the saturated gas refrigerant taken out from the receiver can be heated by mixing the hot gas introduced through the hot gas bypass circuit, and the degree of superheat can be sufficiently increased. It is possible to detect that the liquid refrigerant of the predetermined liquid level has accumulated in the receiver from the temperature difference from when the is taken out. Therefore, the refrigerant charge amount can be detected with high accuracy by sufficiently ensuring the temperature difference under a wide range of temperature conditions without being affected by fluctuations in high pressure due to the outside air temperature, and there is no excess or deficiency. It is possible to fill the optimal amount of refrigerant and to stably operate the air conditioner.

It is a refrigerant circuit figure of the air conditioner concerning a 1st embodiment of the present invention. FIG. 2 is a pressure-enthalpy diagram when saturated gas refrigerant is bypassed through a first liquid level detection circuit at a high temperature in the air conditioner shown in FIG. 1. FIG. 2 is a pressure-enthalpy diagram when saturated liquid refrigerant is bypassed through a first liquid level detection circuit at a high temperature in the air conditioner shown in FIG. 1. FIG. 2 is a pressure-enthalpy diagram when the saturated gas refrigerant is bypassed through the first liquid level detection circuit at a low temperature in the air conditioner shown in FIG. 1. FIG. 2 is a pressure-enthalpy diagram when the saturated gas refrigerant is bypassed through the second liquid level detection circuit at a low temperature in the air conditioner shown in FIG. 1. It is a refrigerant circuit diagram (a part of which is omitted) of an air conditioner according to a second embodiment of the present invention. 7 is a pressure-enthalpy diagram when a mixed refrigerant of saturated gas refrigerant and hot gas is bypassed through a liquid level detection circuit and a hot gas bypass circuit at a low temperature in the air conditioner shown in FIG. 7 is a pressure-enthalpy diagram when a mixed refrigerant of saturated liquid refrigerant and hot gas is bypassed through a liquid level detection circuit and a hot gas bypass circuit at a low temperature in the air conditioner shown in FIG.

Embodiments according to the present invention will be described below with reference to the drawings.
[First Embodiment]
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. 1 to 5.
FIG. 1 shows a refrigerant circuit diagram of an air conditioner according to the first embodiment of the present invention.
The air conditioner 1 is a multi-type air conditioner that is applied to air conditioning of buildings and the like, and includes an outdoor unit 2 and a plurality of indoor units 3 connected in parallel to each other (FIG. 1 shows only one unit). It is composed of).

Inside the outdoor unit 2, a compressor 10 that compresses the refrigerant, a four-way switching valve 11 that switches the circulation direction of the refrigerant, an outdoor heat exchanger 12 that exchanges heat between the outside air and the refrigerant, and the outside air are passed through the outdoor heat exchanger 12. An outdoor fan 13 for heating, an electric expansion valve for heating (heating expansion valve) 14, a receiver 15 for accumulating condensed liquid refrigerant, and the like are disposed, and a compressor 10, a four-way switching valve 11, an outdoor heat exchanger 12, The outdoor refrigerant circuit 17 is configured by sequentially connecting the heating electric expansion valve 14 and the receiver 15 via the refrigerant pipe 16.

A part of the liquid refrigerant is divided into the outdoor refrigerant circuit 17, and the liquid refrigerant is decompressed by the supercooling expansion valve (decompression mechanism) 18, and then sucked into the compressor 10 through the supercooling heat exchanger 19. By returning to the side, a supercooling circuit 20 for providing supercooling to the liquid refrigerant in the supercooling heat exchanger 19 is provided.

Inside the indoor unit 3, an indoor heat exchanger 30, an indoor fan 31 that circulates indoor air through the indoor heat exchanger 30, an electric expansion valve for cooling (an expansion valve for cooling) 32, and the like are disposed. The indoor unit 3 and the outdoor unit 2 are connected through a gas refrigerant pipe 33 and a liquid refrigerant pipe 34, whereby a closed cycle refrigerant circuit 35 is configured. The plurality of indoor units 3 are connected in parallel to each other via a gas refrigerant pipe 33 and a liquid refrigerant pipe 34 branched from the gas refrigerant pipe 33 and the liquid refrigerant pipe 34.

The air conditioner 1 circulates the refrigerant discharged from the compressor 10 to the outdoor heat exchanger 12 side via the four-way switching valve 11, and receives the receiver 15, the supercooling heat exchanger 19, the cooling electric expansion valve 32, By circulating the indoor heat exchanger 30, the four-way switching valve 11 and the compressor 10 in the clockwise direction, the outdoor heat exchanger 12 functions as a condenser and the indoor heat exchanger 30 functions as an evaporator so that the cooling operation can be performed. It has become. During this time, in the supercooling heat exchanger 19, heat is exchanged between the liquid refrigerant and the refrigerant that is diverted to the supercooling circuit 20 and decompressed by the supercooling expansion valve (decompression mechanism) 18, thereby supercooling the liquid refrigerant. Thus, the cooling capacity can be improved.

On the other hand, the refrigerant discharged from the compressor 10 is circulated to the indoor heat exchanger 30 side via the four-way switching valve 11, and the supercooling heat exchanger 19, the receiver 15, the heating electric expansion valve 14, the outdoor heat exchanger. 12, the four-way switching valve 11 and the compressor 10 are circulated in the counterclockwise direction so that the indoor heat exchanger 30 functions as a condenser and the outdoor heat exchanger 12 functions as an evaporator, so that a heating operation can be performed. .

In the air conditioner 1, the lengths of the gas refrigerant pipe 33 and the liquid refrigerant pipe 34 connecting the outdoor unit 2 and the indoor unit 3 vary depending on the environment in which the air conditioner 1 is installed. For this reason, when the outdoor unit 2 is preliminarily filled with a predetermined amount of refrigerant and the air conditioner 1 is installed in the field, the length of the pipe connecting the outdoor unit 2 and the indoor unit 3 when the test operation is performed Insufficient amount of refrigerant must be charged according to the number of indoor units 3 connected. When the refrigerant is additionally charged, the following first liquid level detection circuit 40 and second liquid level detection circuit 45 described below are used so that an appropriate amount of refrigerant can be always charged without depending on the construction level at the site. In addition, a refrigerant amount detection unit 48 is incorporated.

The first liquid level detection circuit 40 includes a bypass circuit 41 that can take out a refrigerant from a predetermined height position in the receiver 15 to the suction side of the compressor 10, a capillary tube provided in the bypass circuit 41, an expansion The bypass circuit 41 is connected and joined to the supercooling circuit 20 near the connection portion where the supercooling circuit 20 is connected to the suction pipe of the compressor 10. ing. A thermistor or the like that detects the temperature of the refrigerant depressurized by the depressurization mechanism 42 or the depressurization mechanism 18 that flows through the bypass circuit 41 and the subcooling circuit 20 at a position closer to the suction pipe side of the compressor 10 than the connection junction of the bypass circuit 41 A temperature sensor (temperature detection unit) 44 is installed.

The second liquid level detection circuit 45 is branched from a position before the decompression mechanism 42 in the bypass circuit 41 constituting the first liquid level detection circuit 40, and is a subcooling expansion valve (decompression mechanism) of the supercooling circuit 20. The circuit connected to the 18 inlet side is provided with an electromagnetic on-off valve 46. The second liquid level detection circuit 45 passes through the supercooling expansion valve (decompression mechanism) 18 and the supercooling heat exchanger 19 in the supercooling circuit 20 for the refrigerant taken out from the receiver 15 during the refrigerant charging operation. 10 is a circuit that returns to the suction side. At this time, an electromagnetic on-off valve 47 is provided near the branch portion of the supercooling circuit 20 in order to stop the liquid refrigerant from being diverted to the supercooling circuit 20.

The refrigerant amount detector 48 is for determining whether or not an appropriate amount of refrigerant has been charged based on the temperature detected by the temperature sensor 44. During the refrigerant charging operation, liquid refrigerant accumulates in the receiver 15, Detection from the temperature sensor 44 when the liquid level reaches the height position where the bypass circuit 31 is opened and the saturated liquid refrigerant is taken out by the first liquid level detection circuit 40 or the second liquid level detection circuit 45. Detection from the temperature sensor 44 when the saturated gas refrigerant is taken out by the first liquid level detection circuit 40 or the second liquid level detection circuit 45 until the temperature and the liquid refrigerant reach a predetermined height position. Based on the temperature difference from the temperature, it is possible to determine whether or not an appropriate amount of refrigerant has been charged.

The refrigerant amount detection unit 48 closes the electromagnetic on-off valve 47 provided in the supercooling circuit 20 during the refrigerant charging operation, and the first liquid level detection circuit 40 or the first level according to the outside air temperature, the high pressure side pressure, or the like. When deciding which of the two liquid level detection circuits 45 is to be used for liquid level detection, it has a function of controlling opening and closing of the electromagnetic on-off

valves

43 and 46. That is, when using the first liquid level detection circuit 40, the electromagnetic switching valve 43 is opened and the electromagnetic switching valve 46 is closed. When using the second liquid level detection circuit 45, the electromagnetic switching valve 43 is closed and the electromagnetic switching valve is closed. The valve 46 is opened.

Next, the refrigerant filling operation and the refrigerant filling amount detection method will be described in more detail with reference to FIGS.
In the refrigerant charging operation, the refrigerant circuit 35 is operated as a cooling cycle. At this time, the outdoor fan 13 is controlled so that the condensation pressure in the outdoor heat exchanger 12 becomes a predetermined value, and at the outlet of the indoor heat exchanger 30, a predetermined superheat degree is given to the refrigerant. The opening degree of the electric expansion valve 32 is controlled. Thereby, the refrigerant can be filled in the refrigerant circuit 35 in a state where the liquid refrigerant pipe 34 is filled with the liquid refrigerant having a predetermined density.

At this time, the electromagnetic on-off valve 47 in the supercooling circuit 20 is closed and, for example, when the outside air temperature is high, such as a cooling rating, the electromagnetic on-off valve 43 is opened, the electromagnetic on-off valve 46 is closed, and the low outside air temperature is low. Sometimes, the electromagnetic on-off valve 43 is closed and the electromagnetic on-off valve 46 is opened. When the operation is continued in this state, the refrigerant circulation amount in the refrigerant circuit 35 is gradually increased, and the liquid level of the refrigerant in the receiver 15 gradually increases. This is because the evaporation amount of the refrigerant in the indoor heat exchanger 30 and the condensation amount of the refrigerant in the outdoor heat exchanger 12 are balanced, and the amount of the refrigerant charged from the outside is in the receiver 15. The condensed liquid refrigerant gradually accumulates.

Here, when the electromagnetic on-off valve 43 is open and the electromagnetic on-off valve 46 is closed when the outside air temperature is high, such as the cooling rating, the liquid refrigerant is placed in the receiver 15 up to a height position where the bypass circuit 41 is open. Until the gas level is accumulated, the saturated gas refrigerant in the receiver 15 flows to the first liquid level detection circuit 40, and when the liquid level of the liquid refrigerant rises to a height position where the bypass circuit 41 is opened, The saturated liquid refrigerant flows into the first liquid level detection circuit 40. When the outside air temperature is high and the high pressure rises, the high pressure may be lowered by controlling the rotation speed of the compressor 10, the rotation speed of the outdoor fan 13, and the like.

The saturated gas refrigerant or saturated liquid refrigerant is decompressed to a low pressure state by the decompression mechanism 43, and the temperature drops. By detecting the temperature of the refrigerant with the temperature sensor 44, the refrigerant amount detection unit looks at the temperature difference between the temperature drop from the saturated gas refrigerant state and the temperature drop from the saturated liquid refrigerant state. 48 detects that the liquid refrigerant of a predetermined liquid level has accumulated in the receiver 15, and determines that the required amount of refrigerant has been filled. At this point, the refrigerant filling operation is terminated.

In order to accurately detect whether or not an appropriate amount of refrigerant has been charged, it is desirable that the temperature difference is sufficiently secured. In the above, when the saturated gas refrigerant is taken out from the receiver 15 to the first liquid level detection circuit 40, as shown in FIG. 2, the pressure in the receiver 15 is around 2 MPa (when the refrigerant is R410A). For example, the pressure is reduced by the pressure reducing mechanism 43, the temperature is lowered to the point A, and a certain degree of superheat SH can be secured. On the other hand, as shown in FIG. 3, when the saturated liquid refrigerant is taken out, depressurized by the depressurization mechanism 43 and evaporated, the degree of superheat of the refrigerant having dropped to the point B is 0 ° C., and the temperature difference exceeds a certain value. Therefore, it is possible to reliably detect that an appropriate amount of refrigerant has been charged.

However, when the outside air temperature is low, the high pressure is reduced and the pressure in the receiver 15 is also reduced. Therefore, when the saturated gas refrigerant is taken out, as shown in FIG. Since the temperature is lowered, the degree of superheat SH can hardly be secured. Accordingly, a sufficient temperature difference cannot be secured with respect to the case where the degree of superheat becomes 0 ° C. due to the saturated liquid refrigerant being taken out and depressurized by the depressurization mechanism 43 to drop in temperature. It becomes. In particular, when the degree of superheat is 2 to 3 ° C. or less, there is a high possibility of erroneous determination.

Therefore, in this embodiment, when the slope of the saturated gas line on the pressure-enthalpy diagram rises to the right at the low outside air temperature at which the high pressure decreases, the electromagnetic on-off valve 43 is closed and the electromagnetic on-off valve 46 is opened. By switching the liquid level detection circuit to the second liquid level detection circuit 45, the refrigerant taken out from the receiver 15 is allowed to flow to the supercooling circuit 20 via the second liquid level detection circuit 45. As described above, the refrigerant taken out to the supercooling circuit 20 via the second liquid level detection circuit 45 is decompressed by the supercooling expansion valve (decompression mechanism) 18, and then is cooled by the supercooling heat exchanger 19. The heat is exchanged and heated, evaporated, and returned to the suction side of the compressor 10.

By detecting the temperature of the refrigerant that has passed through the supercooling circuit 20 with the temperature sensor 44, a temperature difference of a certain value or more is secured between when the saturated gas refrigerant is taken out and when the saturated liquid refrigerant is taken out. Can do. That is, as shown in FIG. 5, the saturated liquid refrigerant is depressurized by the depressurization mechanism 18 and dropped in temperature, then heated and evaporated by the supercooling heat exchanger 19, and the superheat degree is 0 at point D on the saturated gas line. It becomes a refrigerant at ℃. On the other hand, the saturated gas refrigerant is depressurized and drops in temperature to the point C, and then heated by the supercooling heat exchanger 19, whereby the superheat degree SH is increased to the point E. For this reason, a sufficient temperature difference can be ensured, and the refrigerant amount detection unit 48 can reliably detect that an appropriate amount of refrigerant has been charged.

As described above, the saturated gas refrigerant taken out from the receiver 15 is allowed to flow into the supercooling circuit 20 via the second liquid level detection circuit 45 even under conditions where the pressure on the high pressure side cannot be secured at low outside air temperature. Therefore, the supercooling heat exchanger 19 heats the liquid refrigerant for heating, and the degree of superheat can be sufficiently increased. Therefore, the liquid refrigerant of a predetermined liquid level is introduced into the receiver 15 from the temperature difference from when the saturated liquid refrigerant is taken out. Can be reliably detected.
Therefore, the refrigerant charge amount is detected with high accuracy by ensuring a sufficient temperature difference between the saturated gas refrigerant and the saturated liquid refrigerant under a wide range of temperature conditions without being influenced by high pressure fluctuations caused by the outside air temperature. It is possible to fill the optimal amount of refrigerant without excess and deficiency, and to operate the air conditioner 1 stably. Further, since the refrigerant can be heated using the supercooling circuit 20, it is not necessary to provide a heating means specially on the first liquid level detection circuit 40 side, and the configuration can be simplified.

Furthermore, in the present embodiment, an electromagnetic on-off valve 47 that is closed during the refrigerant charging operation and opened during the normal cooling / heating operation is provided near the branch portion from the refrigerant circuit 35 of the supercooling circuit 20. Switching between the refrigerant charging operation and the normal air conditioning operation can be easily performed only by opening / closing the electromagnetic opening / closing valve 47. Therefore, the supercooling circuit 20 can be used in combination as a liquid level detection circuit during the refrigerant charging operation, in addition to improving the capability during the normal cooling / heating operation, and can contribute to an improvement in the detection accuracy of the refrigerant filling amount. Moreover, since the existing temperature sensor provided in the supercooling circuit 20 can be shared as the temperature sensor 44, a temperature sensor can be saved.

[Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to FIGS.
The present embodiment differs from the first embodiment described above in that a hot gas bypass circuit 50 is provided instead of the second liquid level detection circuit 45. Since other points are the same as those in the first embodiment, description thereof will be omitted.
In the present embodiment, as shown in FIG. 6, similarly to the first liquid level detection circuit 40, a capillary is connected to a bypass circuit 41 that connects a predetermined height position in the receiver 15 and the suction side of the compressor 10. A liquid level detection circuit 40 having a pressure reducing mechanism 42 and an electromagnetic opening / closing valve 43 including a tube, an expansion valve, etc., an electromagnetic opening / closing valve 51 capable of introducing a part of hot gas from the discharge side to the suction side of the compressor 10 Temperature of a hot gas bypass circuit 50 having a pressure reducing mechanism 52 including a capillary tube, an expansion valve, etc., and a refrigerant that has passed through the liquid level detection circuit 40 or a mixture of the refrigerant and hot gas introduced from the hot gas bypass circuit 50 And a temperature sensor 53 for detecting.

In the present embodiment, similarly to the first embodiment, the refrigerant amount detection unit 48 detects that liquid refrigerant of a predetermined liquid level has accumulated in the receiver 15 based on the detection value from the temperature sensor 53, and fills the refrigerant. The amount can be determined. In addition, the refrigerant quantity detection unit 48 determines whether to use only the liquid level detection circuit 40 according to the outside air temperature, the high pressure side pressure, or the like during the refrigerant charging operation, or to perform the liquid level detection using the hot gas bypass circuit 50 together. When the determination is made, the electromagnetic on / off

valves

43 and 51 are controlled to open / close. That is, when only the liquid level detection circuit 40 is used, the electromagnetic switching valve 43 is opened and the electromagnetic switching valve 51 is closed, and when the liquid level detection circuit 40 and the hot gas bypass circuit 50 are used together, the electromagnetic switching is performed. Both

valves

43 and 51 are opened.

As described above, the liquid level detection circuit 40 including the pressure reducing mechanism 42 and the electromagnetic opening / closing valve 43 is provided between the predetermined height position of the receiver 15 and the suction side of the compressor 10, and the discharge side and suction of the compressor 10 are provided. A hot gas bypass circuit 50 in which an electromagnetic on-off valve 41 and a pressure reducing mechanism 42 are interposed is provided between the compressor 10 and the hot gas discharged from the compressor 10 via the hot gas bypass circuit 50. In the case where the saturated gas refrigerant is taken out from the receiver 15 using only the liquid level detection circuit 40 when the outside air temperature is as high as the cooling rating, as in the first embodiment. And when the saturated liquid refrigerant is taken out, a temperature difference of a certain value or more can be ensured, so that the refrigerant amount detector 48 can reliably detect that the appropriate amount of refrigerant has been charged. Kill.

When the outside air temperature is low, the electromagnetic on-off valve 51 is opened, and hot gas decompressed by the decompression mechanism 52 is introduced to the suction side of the compressor 10 via the hot gas bypass circuit 50, so that the hot gas is discharged from the receiver 15. The refrigerant can be mixed with the refrigerant taken out by the surface detection circuit 40 and heated. For this reason, the saturated gas refrigerant taken out from the receiver 15 to the liquid level detection circuit 40 is mixed with hot gas decompressed to the point G after being decompressed and dropped to the point F as shown in FIG. Thus, the degree of superheat SH is raised to the H point. On the other hand, as shown in FIG. 8, the saturated liquid refrigerant taken out from the receiver 15 is depressurized and evaporated, drops in temperature to the I point, and then mixed with the hot gas depressurized to the J point to obtain the K point. However, the degree of superheat cannot be ensured. Therefore, a sufficient temperature difference can be ensured, and the refrigerant amount detection unit 48 can reliably detect that an appropriate amount of refrigerant has been charged.

For this reason, hot gas introduced from the discharge side of the compressor 10 to the suction side via the hot gas bypass circuit 50 is mixed with the refrigerant taken out by the liquid level detection circuit 40 even under a low outside air temperature condition. By heating, it is possible to reliably detect that the liquid refrigerant of a predetermined liquid level has accumulated in the receiver 15 from the temperature difference between when the saturated gas refrigerant is taken out and when the saturated liquid refrigerant is taken out. . Therefore, the refrigerant charging amount can be detected with high accuracy by ensuring a sufficient temperature difference between the saturated gas refrigerant and the saturated liquid refrigerant under a wide range of temperature conditions without being influenced by high pressure fluctuations caused by the outside air temperature. Therefore, the air conditioner 1 can be stably operated by filling an optimal amount of refrigerant without excess or deficiency.

Further, in the present embodiment, the hot gas is directly mixed with the refrigerant from the liquid level detection circuit 40 to heat the refrigerant, so that the temperature can be detected without a time delay, and therefore the refrigerant charge amount is detected. The accuracy can be further increased. Furthermore, since the existing suction temperature sensor provided in the suction pipe of the compressor 10 can be shared as the temperature sensor 53, the temperature sensor can be saved.

The present invention is not limited to the invention according to the above-described embodiment, and can be modified as appropriate without departing from the scope of the invention. For example, although the supercooling circuit 20 is omitted in the second embodiment, the invention according to the second embodiment may be applied to the air conditioner 1 including the supercooling circuit 20. . In the above embodiment, the bypass circuit 41 of the first liquid level detection circuit (liquid level detection circuit) 40 is inserted and connected from the upper surface of the receiver 15. As long as it is connected so as to be opened at a predetermined height position, it may be inserted from the side surface or the lower surface of the receiver 15 so as to be opened at a predetermined height position.

DESCRIPTION OF SYMBOLS 1 Air conditioner 2 Outdoor unit 3 Indoor unit 10 Compressor 12 Outdoor heat exchanger 14 Electric expansion valve for heating (expansion valve for heating)
15 Receiver 18 Supercooling expansion valve (pressure reduction mechanism)
19 Supercooling heat exchanger 20 Supercooling circuit 30 Indoor heat exchanger 32 Electric expansion valve for cooling (Expansion valve for cooling)
33 Gas refrigerant pipe 34 Liquid refrigerant pipe 35 Refrigerant circuit 40 First liquid level detection circuit (liquid level detection circuit)
41 Bypass circuit 42 Pressure reducing mechanism 43 Electromagnetic on-off valve 44 Temperature sensor (temperature detection unit)
45 Second liquid level detection circuit 46 Electromagnetic on-off valve 47 Electromagnetic on-off valve 48 Refrigerant amount detection unit 50 Hot gas bypass circuit 51 Electromagnetic on-off valve 52 Pressure reducing mechanism 53 Temperature sensor (temperature detection unit)

Claims

A compressor, an outdoor heat exchanger, a heating expansion valve, a receiver for storing liquid refrigerant, and a part of the liquid refrigerant are shunted, and after the refrigerant is decompressed by a decompression mechanism, the liquid refrigerant and heat are An outdoor unit provided with a supercooling circuit or the like that is exchanged and returned to the suction side of the compressor, and an indoor unit provided with an indoor heat exchanger, a cooling expansion valve, and the like are connected by a gas refrigerant pipe and a liquid refrigerant pipe, In an air conditioner constituting a closed cycle refrigerant circuit,
A first liquid level detection circuit including an on-off valve and a pressure reducing mechanism in a bypass circuit connecting between a predetermined height position of the receiver and the suction side of the compressor via the supercooling circuit;
A second liquid level detection circuit that includes an on-off valve that bypasses the refrigerant branched from the bypass circuit and taken out from the receiver to the inlet side of the decompression mechanism of the supercooling circuit;
A temperature detection unit for detecting the temperature of the refrigerant decompressed through the supercooling circuit including the first liquid level detection circuit or the second liquid level detection circuit;
The temperature after depressurization of the refrigerant taken out from the receiver through the first liquid level detection circuit or the second liquid level detection circuit is detected by the temperature detection unit, and the refrigerant filling amount is determined based on the temperature. An air conditioner comprising a refrigerant amount detection unit.
The air conditioner according to claim 1, wherein an electromagnetic on-off valve is provided near a branch portion of the supercooling circuit from the refrigerant circuit, which is closed during a refrigerant charging operation and opened during a normal air conditioning operation.
Gas refrigerant piping and liquid refrigerant include an outdoor unit including a compressor, an outdoor heat exchanger, a heating expansion valve, and a receiver that stores liquid refrigerant, and an indoor unit including an indoor heat exchanger, a cooling expansion valve, and the like. In an air conditioner connected by piping and constituting a closed-cycle refrigerant circuit,
A liquid level detection circuit including an on-off valve and a pressure reducing mechanism in a bypass circuit connecting between a predetermined height position of the receiver and a suction side of the compressor;
A hot gas bypass circuit comprising an on-off valve and a pressure reducing mechanism capable of introducing a part of hot gas from the discharge side to the suction side of the compressor;
A temperature detection unit capable of detecting the temperature of the refrigerant that has passed through the liquid level detection circuit or a mixture of the refrigerant and hot gas introduced through the hot gas bypass circuit;
The temperature detection unit detects the temperature after decompression of the refrigerant taken out from the receiver into the liquid level detection circuit or a mixed refrigerant of the refrigerant and the refrigerant introduced through the hot gas bypass circuit, and based on the temperature An air conditioner comprising: a refrigerant amount detection unit that determines a refrigerant charge amount.
In the refrigerant amount detection method of the air conditioner according to claim 1 or 2,
During the refrigerant charging operation, the second liquid level detection circuit is closed by the on-off valve under the temperature condition of the cooling rating, and the first liquid level detection circuit is used. Under the low outside air temperature condition, the first liquid level detection circuit is used. A refrigerant amount detection method for an air conditioner, wherein a liquid level detection circuit is closed by the on-off valve and the liquid level detection is performed using the second liquid level detection circuit.
In the refrigerant | coolant amount detection method of the air conditioner of Claim 3,
During the refrigerant charging operation, only the liquid level detection circuit is used under the temperature condition of the cooling rating, and the liquid level detection circuit and the hot gas bypass circuit are both used under the low outside air temperature condition. A refrigerant amount detection method for an air conditioner that performs detection.