JP5595025B2 - Air conditioner and refrigerant amount detection method for air conditioner - Google Patents

Description

  The present invention relates to an air conditioner that can always be filled with an optimal amount of refrigerant during 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 equipped with a cooling expansion valve, an indoor fan, and the like are connected locally via a gas refrigerant pipe and a liquid refrigerant pipe. 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.

  In the technique disclosed in Patent Document 1, 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 means are provided in the bypass circuit. Further, the technique disclosed in Patent Document 2 is provided with an on-off valve, a pressure reducing mechanism, a heating unit, and a temperature detection unit in a bypass circuit, and when a saturated gas refrigerant is taken out from a receiver to the bypass circuit. And when the saturated liquid refrigerant is taken out, the refrigerant temperature after depressurization is measured, and by detecting that the liquid refrigerant of a predetermined liquid level has accumulated in the receiver from the temperature difference, the refrigerant amount Is determined.

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

  However, in the case of what is 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 certain conditions, when a saturated gas refrigerant is taken out and depressurized, a gas-liquid two-phase state may occur.In this case, a sudden temperature drop of the refrigerant is detected, and the liquid refrigerant reaches a predetermined liquid level. There is a possibility that it may be erroneously determined that it has arrived, and there is a problem that detection accuracy cannot be secured.

  On the other hand, in order to solve the above problem, the one disclosed in Patent Document 2 is provided with a heating means for heating the refrigerant decompressed by the decompression mechanism in the liquid level detection circuit, 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. It is a thing. 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 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 ensured, and detection is performed. The problem of reduced accuracy is inherent.

  The present invention has been made in view of such circumstances, and it is possible to always detect the refrigerant charging amount with high accuracy without providing a heating means in the liquid level detection circuit, and the refrigerant amount of the air conditioner. An object is to provide a detection method.

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, an air conditioner according to the present invention includes an outdoor unit having a compressor, an outdoor heat exchanger, a heating expansion valve, a receiver for storing liquid refrigerant, and the like, an indoor heat exchanger, a cooling expansion valve, and the like. In an air conditioner that is connected to the compressor by a gas refrigerant pipe and a liquid refrigerant pipe to form a closed-cycle refrigerant circuit, a bypass that connects between a predetermined height position of the receiver and the suction side of the compressor A liquid level detection circuit provided with an on-off valve and a pressure reduction mechanism in the circuit, temperature detection means for detecting the temperature of the refrigerant depressurized by the pressure reduction mechanism flowing through the liquid level detection circuit, and an intermediate pressure in the receiver The pressure is 5 deg or more of the low pressure saturated gas temperature, and the slope of the saturated gas line in the pressure-enthalpy diagram is controlled to a pressure that rises to the right and is taken out from the receiver to the liquid level detection circuit. By detecting the temperature of the refrigerant in the temperature detecting means, characterized in that it comprises a refrigerant quantity detecting means for determining the refrigerant charge, a based on the temperature.

  According to the present invention, there is provided a liquid level detection circuit in which an on-off valve and a pressure reduction mechanism are provided in a bypass circuit that connects a predetermined height position of the receiver and the suction side of the compressor, and a pressure reduction mechanism that flows through the liquid level detection circuit. The temperature detecting means for detecting the temperature of the decompressed refrigerant and the intermediate pressure in the receiver are set to 5 degrees or more of the saturated gas temperature having a low superheat, and the slope of the saturated gas line in the pressure-enthalpy diagram is Refrigerant amount detection means for controlling the pressure in the rising region and detecting the temperature of the refrigerant taken out from the receiver to the liquid level detection circuit by the temperature detection means, thereby determining the refrigerant charge amount based on the temperature In the receiver in which the superheat degree is 5 deg or more of the low pressure saturated gas temperature and the slope of the saturated gas line in the pressure-enthalpy diagram is controlled to an intermediate pressure where the slope rises to the right From saturated moth The refrigerant temperature after depressurization is detected in each of the case where the refrigerant is taken out and the case where the saturated liquid refrigerant is taken out, and it is detected from the temperature difference that liquid refrigerant of a predetermined liquid level is accumulated in the receiver. Can do. Therefore, the refrigerant filling amount can be detected with high accuracy by ensuring a sufficient temperature difference without being influenced by the refrigerant discharge side pressure (high pressure) and without providing the refrigerant heating means. It is possible to stably operate the air conditioner by filling the optimal amount of refrigerant without any shortage.

  Furthermore, the air conditioner of the present invention is the above air conditioner, wherein the refrigerant amount detection means is an intermediate pressure sensor, a temperature sensor that detects a refrigerant temperature taken out by the liquid level detection circuit, or a high pressure sensor, An outdoor unit that detects the intermediate pressure from a detection value from a temperature sensor or the like that detects the degree of refrigerant supercooling at the outlet of the outdoor heat exchanger or a converted value thereof, and vents the outdoor air to the rotational speed of the compressor and the outdoor heat exchanger It is configured to control the intermediate pressure in the receiver to the pressure by controlling the rotation speed of the fan or the opening degree of the heating expansion valve.

  According to the present invention, the refrigerant amount detection means detects the refrigerant supercooling degree at the intermediate pressure sensor, the temperature sensor that detects the refrigerant temperature taken out by the liquid level detection circuit, or the high-pressure sensor and the outdoor heat exchanger outlet. The intermediate pressure is detected from the detected value from the sensor etc. or its converted value, and the rotational speed of the compressor, the rotational speed of the outdoor fan that vents the outdoor air to the outdoor heat exchanger, the opening degree of the expansion valve for heating, etc. are controlled. Since the intermediate pressure in the receiver is controlled to the above-mentioned pressure, the intermediate pressure in the receiver is set to the rotation speed of the compressor, the rotation speed of the outdoor fan that ventilates the outdoor air to the outdoor heat exchanger, or heating. By controlling the opening of the expansion valve, etc., the degree of superheat is 5 deg or more of the low pressure saturated gas temperature, and the slope of the saturated gas line in the pressure-enthalpy diagram becomes an upwardly rising region. Control to intermediate pressure It can be. Therefore, it is possible to accurately detect the refrigerant filling amount by detecting the refrigerant temperature after decompression by the liquid level detection circuit without adding the refrigerant heating means in hardware, and to fill the optimum amount of refrigerant without excess or deficiency. Can do.

  Furthermore, the air conditioner of the present invention is the above air conditioner, wherein hot gas discharged from the compressor is introduced between the discharge side of the compressor and the receiver, and the inside of the receiver is A hot gas bypass circuit for raising the intermediate pressure of the gas to the pressure is provided.

  According to the present invention, a hot gas bypass circuit is provided between the discharge side of the compressor and the receiver for introducing hot gas discharged from the compressor and increasing the intermediate pressure in the receiver to the above pressure. Therefore, for example, even when the intermediate pressure in the receiver does not rise to the above pressure under a low outside air temperature condition, by introducing a part of the hot gas to the receiver via the hot gas bypass circuit, The intermediate pressure can be controlled to the above pressure. Therefore, the refrigerant filling amount can be accurately detected even under a low outside air temperature condition, and the optimum amount of refrigerant can be filled. In addition, this makes it possible to easily increase the pressure even under a low outside air temperature condition, and can be effectively applied to high pressure control or the like during cooling at a low outside air temperature.

  Further, the refrigerant amount detection method for an air conditioner according to the present invention includes an outdoor unit having a compressor, an outdoor heat exchanger, a heating expansion valve, a receiver for storing liquid refrigerant, an indoor heat exchanger, and a cooling expansion. In an air conditioner refrigerant amount detection method in which an indoor unit having a valve or the like is connected by a gas refrigerant pipe and a liquid refrigerant pipe to form a closed-cycle refrigerant circuit, the intermediate pressure in the receiver during refrigerant charging operation Is controlled to a pressure where the degree of superheat is not less than 5 deg. Of the saturated gas temperature of the low pressure and the slope of the saturated gas line in the pressure-enthalpy diagram is in an upwardly rising region. The refrigerant charge amount is determined by detecting the temperature of the refrigerant taken out from the height position to the liquid level detection circuit connected to the compressor suction side and decompressed to a low pressure state in the liquid level detection circuit. Features.

  According to the present invention, during the refrigerant charging operation, the intermediate pressure of the refrigerant in the receiver is equal to or greater than 5 deg of the saturated gas temperature with a low superheat degree, and the slope of the saturated gas line in the pressure-enthalpy diagram rises to the right. The intermediate pressure refrigerant is taken out from the predetermined height position of the receiver to the liquid level detection circuit connected to the compressor suction side, and reduced to a low pressure state in the liquid level detection circuit. Since the refrigerant charging amount is determined by detecting the temperature of the refrigerant, the degree of superheat is 5 deg or more of the low pressure saturated gas temperature, and the slope of the saturated gas line in the pressure-enthalpy diagram rises to the right. In the case where the saturated gas refrigerant is taken out from the receiver controlled to the intermediate pressure in the region of the above and in the case where the saturated liquid refrigerant is taken out, the refrigerant temperature after depressurization is detected, and the temperature difference is detected. In the receiver It is possible to detect that the accumulated predetermined liquid level of the liquid refrigerant. Therefore, the refrigerant filling amount can be detected with high accuracy by ensuring the temperature difference sufficiently without being influenced by the refrigerant discharge side pressure (high pressure) and without providing a means for heating the refrigerant. It is possible to fill the air conditioner with an optimal amount of refrigerant without excess or deficiency.

  According to the present invention, according to the air conditioner and the refrigerant amount detection method of the air conditioner, the degree of superheat is not less than 5 deg of the low pressure saturated gas temperature, and the slope of the saturated gas line in the pressure-enthalpy diagram rises to the right. When the saturated gas refrigerant is taken out from the receiver controlled to the intermediate pressure that becomes the region of the above and when the saturated liquid refrigerant is taken out, the refrigerant temperature after depressurization is detected, and the difference in temperature is detected in the receiver. Since it is possible to detect that the liquid refrigerant of a predetermined liquid level has accumulated, the above temperature difference is sufficiently ensured without being influenced by the refrigerant discharge side pressure and without providing the refrigerant heating means. Thus, the refrigerant charge amount can be detected with high accuracy, and the optimum amount of refrigerant can be charged without excess or deficiency, and the air conditioner can be operated stably.

It is a refrigerant circuit figure of the air conditioner concerning a 1st embodiment of the present invention. It is the refrigerant circuit figure which abbreviate | omitted a part of modification of the air conditioner shown in FIG. It is the refrigerant circuit figure which abbreviate | omitted a part of another modification of the air conditioner shown in FIG. In the air conditioner shown in FIG. 1, it is a pressure-enthalpy diagram at the time of making the pressure in a receiver into the enthalpy maximum vicinity with a saturated gas line. In the air conditioner shown in FIG. 1, it is a pressure-enthalpy diagram at the time of making the intermediate pressure in a receiver into the enthalpy maximum vicinity with a saturated gas line by intermediate pressure control. 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.

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 storing condensed liquid refrigerant, etc. 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.

  Inside the indoor unit 3, an indoor heat exchanger 20, an indoor fan 21 that circulates indoor air through the indoor heat exchanger 20, a cooling electric expansion valve (cooling expansion valve) 22, and the like are disposed. The indoor unit 3 and the outdoor unit 2 are connected via a gas refrigerant pipe 23 and a liquid refrigerant pipe 24, whereby a closed-cycle refrigerant circuit 25 is configured. The plurality of indoor units 3 are connected in parallel to each other via the gas refrigerant pipe 23 and the liquid refrigerant pipe 24 branched from the gas refrigerant pipe 23 and the liquid refrigerant pipe 24.

  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 cooling electric expansion valve 22, the indoor heat exchanger 20, and the four-way switching valve 11. By circulating the 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 20 functions as an evaporator so that a cooling operation can be performed. On the other hand, the refrigerant discharged from the compressor 10 is circulated to the indoor heat exchanger 20 side via the four-way switching valve 11, and the receiver 15, the heating electric expansion valve 14, the outdoor heat exchanger 12, the four-way switching valve 11, and By circulating counterclockwise in the order of the compressor 10, the indoor heat exchanger 20 functions as a condenser and the outdoor heat exchanger 12 functions as an evaporator so that heating operation can be performed.

  In the air conditioner 1, the lengths of the gas refrigerant pipe 23 and the liquid refrigerant pipe 24 that connect 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 liquid level detection circuit 30 and refrigerant amount detection means 35 are incorporated in order to always be able to charge an appropriate amount of refrigerant without depending on the construction level at the site. Yes.

  The liquid level detection circuit 30 includes a bypass circuit 31 that can take out the refrigerant from a predetermined height position in the receiver 15 to the suction side of the compressor 10, and a capillary tube, an expansion valve, and the like provided in the bypass circuit 31. And a temperature sensor (temperature detection means) 34 such as a thermistor for detecting the refrigerant temperature after being taken out by the bypass circuit 31 and decompressed by the decompression mechanism 32. .

  The refrigerant amount detection means 35 is for determining whether or not an appropriate amount of refrigerant has been filled based on the temperature detected by the temperature sensor 34. During the refrigerant filling operation, the liquid refrigerant is present in the receiver 15. When the liquid level reaches the height position at which the bypass circuit 31 opens and the saturated liquid refrigerant is taken out to the bypass circuit 31, the detected temperature from the temperature sensor 34 and the liquid refrigerant are at a predetermined level. Whether the gas refrigerant in the saturated state has been taken out from the receiver 15 to the bypass circuit 31 until reaching the position, based on the temperature difference from the temperature detected from the temperature sensor 34, was the appropriate amount of refrigerant filled? It can be determined whether or not.

  Further, the refrigerant amount detection means 35 has an intermediate pressure in the receiver 15 at the time of refrigerant filling operation, the superheat degree is not less than 5 deg. Of the saturated gas temperature, and the slope of the saturated gas line in the pressure-enthalpy diagram is right. It has a function to control the pressure to become a shoulder rise area. This is because, for example, the intermediate pressure detected by the intermediate pressure sensor 36 is 5 deg or more of the saturated gas temperature of the low pressure on the pressure-enthalpy diagram, and the slope of the saturated gas line rises to the right. The pressure is controlled by adjusting the rotational speed of the compressor 10, the rotational speed of the outdoor fan 13, or the opening degree of the heating electric expansion valve 14 so that the pressure becomes the same pressure.

  It should be noted that the intermediate pressure in the receiver 15 is obtained by replacing the intermediate pressure sensor 36 with the detected temperature from the temperature sensor 37 provided in the refrigerant take-out portion of the bypass circuit 31, as shown in FIG. As shown in FIG. 3, the pressure may be detected by converting into pressure, or provided at the outlet of the high pressure sensor 38 and the outdoor heat exchanger 12 provided in the discharge pipe of the compressor 10. On the basis of the detected value from the temperature sensor 39 that detects the degree of supercooling of the refrigerant being stored, it may be calculated by converting into a saturated liquid pressure having a constant enthalpy.

Next, the refrigerant filling operation and the refrigerant filling amount detection method will be described in more detail with reference to FIG. 4 and FIG.
In the refrigerant charging operation, the refrigerant circuit 25 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 20, a predetermined superheat degree is given to the refrigerant. The opening degree of the electric expansion valve 22 is controlled. Thereby, the refrigerant can be filled in the refrigerant circuit 25 in a state where the liquid refrigerant pipe 24 is filled with the liquid refrigerant having a predetermined density. At this time, the electromagnetic opening / closing valve 33 of the liquid level detection circuit 30 is open.

  When the operation is continued in this state, the refrigerant circulation amount in the refrigerant circuit 25 is gradually increased, and the liquid level of the refrigerant in the receiver 15 gradually increases. This is because the amount of refrigerant evaporated in the indoor heat exchanger 20 and the amount of refrigerant condensed in the outdoor heat exchanger 12 are balanced, and the receiver 15 is filled with the amount of refrigerant charged from the outside. Liquid refrigerant gradually accumulates. At this time, the saturated gas refrigerant in the receiver 15 flows to the bypass circuit 31 until the liquid refrigerant is accumulated in the receiver 15 up to a height position where the bypass circuit 31 of the liquid level detection circuit 30 is opened. That is, when the liquid level of the liquid refrigerant rises to the height position where the bypass circuit 31 is opened, the saturated liquid refrigerant flows into the bypass circuit 31.

  The saturated gas refrigerant or saturated liquid refrigerant is decompressed to a low pressure state by the decompression mechanism 33, and the temperature drops. By detecting the temperature of the refrigerant with the temperature sensor 34, the refrigerant amount detecting means 35 is configured to look at the temperature difference between the temperature drop from the saturated gas refrigerant state and the temperature drop from the saturated liquid refrigerant state. It is determined that the liquid refrigerant of a predetermined liquid level has accumulated in the receiver 15, and it is determined that the required amount of refrigerant has been filled. At this point, the refrigerant filling operation is terminated.

  Here, in order to accurately detect that the appropriate amount of refrigerant has been charged, it is desirable that the temperature difference is sufficiently secured. Normally, the saturated liquid refrigerant that has flowed into the bypass circuit 31 is decompressed by the decompression mechanism 33 to become a gas-liquid two-phase state and evaporates, so that the temperature detected by the temperature sensor 34 rapidly decreases. On the other hand, the refrigerant flowing in the saturated gas state increases the discharge side pressure of the compressor 10 due to, for example, an increase in the outside air temperature, and the slope pressure of the saturated gas line in the pressure-enthalpy diagram increases to the left. Under the circumstances, there is a case where a gas-liquid two-phase state occurs when the pressure is reduced by the pressure reducing mechanism 33. In this case, a sudden temperature drop due to the evaporation of the refrigerant is detected, and the refrigerant amount detecting means 35 is The liquid refrigerant may erroneously be determined to have reached a predetermined liquid level.

  However, in this embodiment, as shown in FIG. 4, the intermediate pressure of the refrigerant in the receiver 15 is equal to or higher than 5 deg. Of the saturated gas temperature of the low pressure, and the saturated gas line on the pressure-enthalpy diagram. Since the saturated gas refrigerant in this state is taken out to the bypass circuit 31 and is depressurized to lower the temperature, the saturation of the refrigerant depressurized to low pressure is controlled. It is possible to always secure a superheat degree SH of 5 deg or more with respect to the gas temperature.

  That is, in FIG. 4, when the temperature is reduced from the saturated gas state to the point A where the temperature is reduced due to the reduced pressure from the saturated liquid refrigerant, in the case where the gas-liquid two-phase state is brought about by the reduced pressure, Even when the temperature drops on the saturated gas line and the degree of superheat is large, the temperature may only be 2 to 3 ° C. In this case, a sufficient temperature difference cannot be ensured, resulting in erroneous determination. However, in the case of this embodiment, the temperature can always be lowered to the point B at which the degree of superheating SH of at least 5 deg or more can be secured, so that erroneous determination can be reliably eliminated.

  FIG. 4 is a pressure-enthalpy diagram when the pressure in the receiver 15 is near the maximum enthalpy with a saturated gas line. Using R410A refrigerant, the refrigerant is taken out from the vicinity of 2 MPa to the bypass circuit 31 and the temperature drops. FIG. 5 shows a pressure-enthalpy diagram at the time of actual refrigerant charging operation. That is, although the discharge side pressure of the compressor 10 is higher than the intermediate pressure in the receiver 15, the intermediate pressure in the receiver 15 flows into the intermediate pressure sensor 36 and the bypass circuit 31 without being influenced by this high pressure. The intermediate pressure is detected from the detected value from the temperature sensor 37 for detecting the temperature, the temperature sensor 39 for detecting the degree of refrigerant supercooling at the outlet of the high pressure sensor 38 and the outdoor heat exchanger 13 or the converted value thereof. By controlling the rotational speed, the rotational speed of the outdoor fan 13 that ventilates the outdoor air to the outdoor heat exchanger 12, or the opening degree of the heating expansion valve 14, etc., the liquid refrigerant in the receiver 15 is controlled by the above pressure. It is on the saturated liquid line.

The saturated gas refrigerant or the saturated liquid refrigerant is taken out from the receiver 15 to the bypass circuit 31, and is reduced in pressure by the pressure reducing mechanism 33, and the temperature is decreased by detecting the temperature by the temperature sensor 34, thereby detecting the refrigerant amount from the temperature difference. The amount of refrigerant can be accurately detected via the means 35.
Therefore, according to the present embodiment, the temperature difference is sufficiently reduced without being influenced by the refrigerant discharge side pressure (high pressure) affected by the outside air temperature or the like, and without providing the refrigerant heating means in the bypass circuit 31. It is possible to secure and detect the refrigerant filling amount with high accuracy, and to fill the optimum amount of refrigerant without excess and deficiency and to operate the air conditioner stably.

[Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to FIG.
This embodiment is different from the first embodiment described above in that a hot gas bypass circuit 40 is added. 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, a part of the hot gas discharged from the compressor 10 can be introduced into the receiver 15 between the discharge pipe from the compressor 10 and the receiver 15. The hot gas bypass circuit 40 is provided. The hot gas bypass circuit 40 is provided with an electromagnetic on-off valve 41 and a pressure reducing mechanism 42 such as a capillary tube or an expansion valve.

  As described above, the hot gas bypass circuit 40 in which the electromagnetic on-off valve 41 and the pressure reducing mechanism 42 are interposed is provided between the discharge side of the compressor 10 and the receiver 15, and is discharged from the compressor 10 into the receiver 15. By allowing a part of the hot gas to be introduced, the electromagnetic on-off valve 41 can be used even when the intermediate pressure in the receiver 15 does not rise to the above-described pressure during the refrigerant charging operation, for example, under a low outside air temperature condition. Is opened, and hot gas is introduced into the receiver 15 via the hot gas bypass circuit 40, whereby the intermediate pressure in the receiver 15 can be controlled to the above-described pressure.

  Therefore, the refrigerant filling amount can be accurately detected even under a low outside air temperature condition, and the optimum amount of refrigerant can be filled. This also makes it possible to easily increase the pressure even under low outside air temperature conditions. In general, the control for reducing the pressure is easy and the control for increasing the pressure is difficult. However, according to the present embodiment, the pressure control at the low outside air temperature can be facilitated. Furthermore, the hot gas bypass circuit 40 can be effectively applied not only to the refrigerant charging operation but also to high pressure control at the time of cooling at a low outside air temperature, and contributes to the expansion of the cooling operation range by the air conditioner 1. Can do.

  In addition, this invention is not limited to the invention concerning the said embodiment, In the range which does not deviate from the summary, it can change suitably. For example, in the above embodiment, the bypass circuit 31 of the liquid level detection circuit 30 is inserted and connected to the receiver 15 from the upper surface of the receiver 15, but the bypass circuit 31 has a predetermined height in the receiver 15. It is only necessary to be connected so as to be opened at a position, and therefore, it may be inserted so as to be opened from a side surface or a 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 13 Outdoor fan 14 Electric expansion valve for heating (expansion valve for heating)
15 Receiver 20 Indoor Heat Exchanger 22 Electric Expansion Valve for Cooling (Expansion Valve for Cooling)
23 Gas refrigerant pipe 24 Liquid refrigerant pipe 25 Refrigerant circuit 30 Liquid level detection circuit 31 Bypass circuit 32 Pressure reducing mechanism 33 Electromagnetic on-off valve 34 Temperature sensor (temperature detection means)
35 Refrigerant amount detection means 36 Intermediate pressure sensor 37 Temperature sensor 38 High pressure sensor 39 Temperature sensor 40 Hot gas bypass circuit

Claims (4)

An outdoor unit having a compressor, an outdoor heat exchanger, a heating expansion valve and a receiver for storing liquid refrigerant, and an indoor unit having an indoor heat exchanger, a cooling expansion valve, etc. are connected by gas refrigerant pipe and liquid refrigerant pipe. In an air conditioner that connects and configures a closed-cycle refrigerant circuit,
A liquid level detection circuit provided with 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;
Temperature detection means for detecting the temperature of the refrigerant decompressed by the decompression mechanism flowing through the liquid level detection circuit;
The intermediate pressure in the receiver is controlled to a pressure at which the superheat degree is not less than 5 deg. Of the saturated gas temperature at a low pressure, and the slope of the saturated gas line in the pressure-enthalpy diagram is an upwardly rising region. And air amount comprising refrigerant amount detecting means for determining the refrigerant filling amount based on the temperature detected by the temperature detecting means by detecting the temperature of the refrigerant taken out by the liquid level detecting circuit. Harmony machine.   The refrigerant amount detection means includes an intermediate pressure sensor, a temperature sensor that detects a refrigerant temperature taken out by the liquid level detection circuit, a high pressure sensor, and a temperature sensor that detects a refrigerant subcooling degree at the outlet of the outdoor heat exchanger. The intermediate pressure is detected from the detected value or its converted value, and the rotational speed of the compressor, the rotational speed of the outdoor fan that ventilates the outdoor air to the outdoor heat exchanger, or the opening degree of the heating expansion valve is controlled. The air conditioner according to claim 1, wherein the air conditioner is configured to control an intermediate pressure in the receiver to the pressure.   A hot gas bypass circuit is provided between the discharge side of the compressor and the receiver to introduce hot gas discharged from the compressor and raise the intermediate pressure in the receiver to the pressure. The air conditioner according to claim 1 or 2, characterized in that. Gas refrigerant piping and liquid refrigerant piping connect an outdoor unit having a compressor, an outdoor heat exchanger, a heating expansion valve and a receiver for storing liquid refrigerant, and an indoor unit having an indoor heat exchanger, a cooling expansion valve, etc. In the refrigerant amount detection method of the air conditioner that connects and configures the closed-cycle refrigerant circuit,
During the refrigerant charging operation, the intermediate pressure in the receiver is controlled to a pressure at which the superheat degree is 5 deg or more of the saturated gas temperature with a low pressure, and the slope of the saturated gas line in the pressure-enthalpy diagram is in an upwardly rising region. And
The intermediate pressure refrigerant is taken out from a predetermined height position of the receiver to a liquid level detection circuit connected to the compressor suction side,
A refrigerant amount detection method for an air conditioner, characterized in that the refrigerant charge amount is determined by detecting the temperature of the refrigerant decompressed to a low pressure state in the liquid level detection circuit.

Images