JP5927633B2 - Air conditioner - Google Patents

Description

  The present invention relates to an air conditioner.

  A technique using an HFC-based refrigerant as a refrigerant of an air conditioner and using an ether oil compatible with the refrigerant as a refrigerating machine oil is known (Patent Document 1). Further, R32, which is an HFC-based refrigerant, has a compressor discharge temperature of 10 to 15 ° C. higher than that of the conventional refrigerant R410A. Therefore, in order to suppress the discharge temperature, the refrigerant inlet degree at the compressor inlet is 0.65 or more and There is also known a technique of making the value 0.85 or less (Patent Document 2).

JP-A-11-325620 Japanese Patent No. 3956589

  R32, which is an HFC-based refrigerant, is expected as an environmentally friendly refrigerant because it has a low global warming potential GWP (Global Warming Potentia). However, paying attention to the mixing characteristics of the refrigerant R32 and the lubricating oil, there is a region where the compatibility is lowered and the lubricating oil and the liquid refrigerant are separated into two layers when the mixing ratio of the lubricating oil is small.

  Further, the refrigerant R32 controls the refrigerant inlet side refrigerant degree to be smaller than that of the conventional refrigerant R410A. Therefore, when R32 is used, the lubricating oil mixing ratio of the liquid mixture of the liquid refrigerant and the lubricating oil in the accumulator provided on the compressor inlet side becomes small. For this reason, the liquid refrigerant and the lubricating oil are easily separated into two layers in the accumulator, and the lubricating oil is difficult to return to the compressor. As a result, the lubricating oil in the compressor becomes insufficient, causing poor lubrication and the reliability is lowered.

  Accordingly, an object of the present invention is to provide an air conditioner that can prevent liquid refrigerant and lubricating oil from separating into two layers and reduce the occurrence of insufficient lubrication.

  In order to solve the above-described problems, an air conditioner according to the present invention connects an indoor unit and an outdoor unit through a pipe and circulates the refrigerant. A mixed refrigerant containing at least mass percent is used, and the compressor of the outdoor unit is supplied with a refrigerant mixed with a lubricating oil of a predetermined value or more so that two-layer separation between the liquid refrigerant and the lubricating oil does not occur. ing.

  The outdoor unit is connected to a compressor and a discharge side of the compressor, and is connected to an oil separator that separates and recovers oil in the refrigerant discharged from the compressor. The liquid refrigerant is separated and accumulated, and the accumulator for supplying the gas refrigerant to the compressor and the lubricating oil separated by the oil separator are returned to the accumulator, so that the liquid refrigerant and the lubricating oil accumulated in the accumulator And a supply oil amount adjusting unit for adjusting the lubricating oil mixing ratio in the mixed liquid to a predetermined value or more.

  According to the present invention, occurrence of two-layer separation between the liquid refrigerant and the lubricating oil can be suppressed, and insufficient lubrication can be reduced to increase reliability.

It is a circuit block diagram of an air conditioner. It is a longitudinal cross-sectional view of an accumulator. It is a figure which shows the mixing characteristic of refrigerant | coolant R32 and lubricating oil.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In this embodiment, as will be described in detail below, when a refrigerant containing at least a predetermined mass percent of R32, which is an HFC refrigerant, is used, a refrigerant mixed with a lubricating oil of a predetermined value or more is supplied to the compressor. Specifically, in the mixed liquid (mixed liquid of liquid refrigerant and lubricating oil) accumulated in the accumulator connected to the inflow side of the compressor, the mixing ratio of the lubricating oil is adjusted to a predetermined value or more. In order to adjust the mixing ratio of the lubricating oil in the mixed liquid in the accumulator, the lubricating oil separated by the oil separator connected to the discharge side of the compressor is returned to the accumulator so as to satisfy a predetermined condition. Here, in this embodiment, a mixed refrigerant containing 70 mass% or more of R32 is used. This is because, when the ratio of R32 is 70 mass percent or more, characteristics such as GWP value, wetness of suction, compatibility with oil, and the like become equivalent to R32.

  According to this embodiment, the liquid refrigerant and the lubricating oil are prevented from being separated into two layers in the accumulator by adjusting the mixing ratio of the lubricating oil in the mixed liquid of the refrigerant R32 and the lubricating oil in the accumulator. Can do. As a result, the amount of lubricating oil contained in the refrigerant supplied from the accumulator to the compressor can be increased, reducing the occurrence of a shortage of lubricating oil in the compressor, and improving the reliability of the compressor and the air conditioner. Can be improved.

  Embodiments will be described with reference to FIGS. FIG. 1 shows a configuration example of a refrigeration cycle of an air conditioner 1 according to the present embodiment.

  The refrigeration cycle of the air conditioner 1 includes at least one outdoor unit 100 and at least one indoor unit 200. In FIG. 1, a plurality of indoor units 200 </ b> A and 200 </ b> B are shown. Although FIG. 1 shows an example in which one outdoor unit 100 and two indoor units 200 are connected, the present invention is not limited to this, and a configuration in which two or more outdoor units 100 and three or more indoor units 200 are connected is also possible. Good.

  The outdoor unit 100 includes, for example, an outdoor heat exchanger 101, an outdoor fan 102, an outdoor expansion valve 103, a compressor 104, an accumulator 105, an oil separator 106, an oil return capillary 107, a four-way valve 108, a supercooling heat exchanger 109, The cooling bypass expansion valve 110 and the pipes 112 to 117 are included.

  The indoor unit 200 includes, for example, an indoor heat exchanger 201, an indoor fan 202, and an indoor expansion valve 203. The outdoor unit 100 and the indoor unit 200 are connected by a liquid pipe 121 and a gas pipe 302.

  Here, in the present embodiment, a refrigerant composed of only R32 or a mixed refrigerant containing R32 in an amount of 70% by mass or more is used. Next, the operation will be described.

  The compressor 104 includes, for example, a crankcase and a compressor main body (both not shown) provided in the crankcase, and lubricating oil is accumulated on the bottom side of the crankcase. During the compression operation by the compressor main body, the lubricating oil in the crankcase is sucked up by a pump action and supplied to a portion requiring lubrication. A part of the lubricating oil is discharged to the discharge pipe 112 together with the refrigerant.

  A low-pressure gaseous refrigerant flows into the compressor 104 through the pipe 117 from the accumulator 105. The compressor 104 compresses the refrigerant to discharge a high-temperature and high-pressure gaseous refrigerant from the discharge port. The high-pressure gaseous refrigerant discharged from the discharge port of the compressor 104 into the pipe 112 flows into the oil separator 106 as an “oil separator” through the pipe 112. Lubricating oil is mixed in the high-temperature and high-pressure gaseous refrigerant discharged from the compressor 104.

  The oil separator 106 collects the lubricating oil contained in the high-pressure gaseous refrigerant and returns the collected lubricating oil to the accumulator 105 through the oil return capillary 107 and the pipe 116. The pipe 116 is a pipe line for connecting the port on the compressor inlet side of the four-way valve 108 and the inlet of the accumulator 105. An oil return capillary 107 as an example of a “supply oil amount adjusting unit” is a device for adjusting the flow rate and pressure of lubricating oil returned from the oil separator 106 to the accumulator 105.

  The four-way valve 108 is a direction switching valve for switching whether the high-pressure gaseous refrigerant is led to the outdoor heat exchanger 101 or the indoor heat exchanger 201 in the outdoor unit 200. The four-way valve 108 allows a high-pressure gaseous refrigerant to flow in the direction of the arrow C in FIG. The high-pressure gaseous refrigerant flows into the outdoor heat exchanger 101 that functions as a condenser via a pipe 113 that connects the outdoor heat exchanger side port of the four-way valve 108 and the inlet side of the outdoor heat exchanger 101.

  While passing through the outdoor heat exchanger 101, the high-temperature and high-pressure gaseous refrigerant is condensed by exchanging heat with outdoor air sent by the outdoor fan 102 to become a high-temperature and high-pressure liquid refrigerant (liquid refrigerant). The high-temperature and high-pressure liquid refrigerant flows into the outdoor expansion valve 103 via the pipe 114 connected to the outlet side of the outdoor heat exchanger 101. The low-pressure liquid refrigerant flowing out of the outdoor expansion valve 103 branches, and a part of the liquid refrigerant flows into the supercooling bypass expansion valve 110. The other liquid refrigerant is further cooled via the supercooling heat exchanger 109 and flows into the pipe 301. The pipe 301 is a pipe that connects the heat exchanger 101 of the outdoor unit 100 and the heat exchanger 201 of the indoor unit 200.

  The liquid refrigerant flowing into the supercooling bypass expansion valve 110 is decompressed by the supercooling bypass expansion valve 110 and flows into the supercooling heat exchanger 109. The liquid refrigerant that has flowed into the supercooling heat exchanger 109 evaporates by exchanging heat with other liquid refrigerant while passing through the supercooling heat exchanger 109 to become a low-pressure gaseous refrigerant. The low-pressure gaseous refrigerant flows into the accumulator 105 via a return pipe line 115 connected to the pipe 116.

  The low-pressure liquid refrigerant sent to the indoor unit 200 is decompressed by the indoor expansion valve 203 and flows into the indoor heat exchanger 201. The low-pressure liquid refrigerant that has flowed into the indoor heat exchanger 201 evaporates by exchanging heat with the indoor air sent by the indoor fan 202 while passing through the indoor heat exchanger 201, and a gaseous refrigerant (gas refrigerant). Become.

  When the low-pressure liquid refrigerant is vaporized in the indoor heat exchanger 201, the indoor air is cooled and the room is cooled. The gas refrigerant flowing out from the indoor heat exchanger 201 is sent to the outdoor unit 100 via the gas pipe 302.

  The gas refrigerant that has entered the outdoor unit 100 flows into the accumulator 105 through the four-way valve 108 and the pipe 116. The accumulator 105 prevents the liquid refrigerant from flowing into the compressor 104 by accumulating the liquid refrigerant that has not evaporated. This is because if the compressor 104 compresses the liquid refrigerant, parts of the compressor 104 may be damaged.

  A gaseous refrigerant, liquid refrigerant, and lubricating oil returned from the oil separator 106 flow into the accumulator 105. The gas refrigerant and lubricating oil are mixed in the accumulator 105 and sent to the compressor 104. The liquid refrigerant stays in the accumulator 105.

  The operation during heating operation will be described. The flow of the refrigerant during the heating operation is indicated by an arrow line H. The high-temperature and high-pressure gas refrigerant discharged from the compressor 104 is sent to the gas pipe 302 through the four-way valve 108 after the lubricating oil is separated by the oil separator 106. The lubricating oil separated by the oil separator 106 is sent to the accumulator 105 through the oil return capillary 107.

  The high-temperature and high-pressure gas refrigerant from the outdoor unit 100 is sent to the indoor unit 200 via the gas pipe 302. While flowing through the indoor heat exchanger 201, the high-temperature gas refrigerant that has entered the indoor unit 200 exchanges heat with the indoor air sent by the indoor fan 202 and becomes liquid refrigerant. The liquid refrigerant exits the indoor unit 200 through the indoor expansion valve 203. Heating is performed by heat exchange between the high-temperature and high-pressure gas refrigerant and room air in the indoor heat exchanger 200.

  The liquid refrigerant that has exited the indoor unit 200 flows to the outdoor unit 100 via the liquid pipe 301. The liquid refrigerant that has entered the outdoor unit 100 passes through the outdoor expansion valve 103 and then branches into two. A part of the liquid refrigerant flows to the supercooling bypass expansion valve 110 and is sent to the accumulator 105 via the pipes 115 and 116.

  The other liquid refrigerant is decompressed by the outdoor expansion valve 103 and then flows into the outdoor heat exchanger 101. The liquid refrigerant that has flowed into the outdoor heat exchanger 101 evaporates by exchanging heat with outdoor air sent by the outdoor fan 102 while flowing through the outdoor heat exchanger 101, and becomes a gas refrigerant. The gas refrigerant passes through the four-way valve 108 and flows into the accumulator 105 through the pipe 116. As described above, the gas refrigerant and the lubricating oil flow into the accumulator 105 and mix, and the gas refrigerant in which the lubricating oil is dissolved is sent to the compressor 104.

  FIG. 2 shows the accumulator 105 shown in the outdoor unit 100 of the refrigeration cycle of FIG.

  In the accumulator 105, an introduction pipe 116 (introduction pipe) and a lead-out pipe 117 (outlet pipe) are inserted and attached. The introduction pipe 116 is a pipe for introducing a gas refrigerant and / or lubricating oil into the accumulator 105.

  The lead-out pipe 117 has a substantially U shape at the tip side, and is a pipe for sending a gas refrigerant mixed with lubricating oil from the accumulator 105 to the compressor 104. The lead-out tube 117 is attached so that the U-shaped curved portion is positioned on the bottom side of the accumulator 105. As a result, the U-shaped curved portion of the outlet pipe 117 is immersed in the liquid refrigerant accumulated in the accumulator 105.

  A first liquid return port 121 </ b> A is formed in the U-shaped curved portion of the outlet pipe 117. Further, the outlet pipe 117 is formed with a second liquid return port 121B located above the first liquid return port 121A. A pressure equalizing hole 122 for adjusting the pressure in the outlet pipe 117 is formed on the upper side of the outlet pipe 117 and is positioned on the upper side in the accumulator 105.

  The refrigerant and lubricating oil flowing into the accumulator 105 from the introduction pipe 116 are separated into liquid and gas. The gas refrigerant is sent to the compressor 104 through the outlet pipe 117. Due to the circulation of the gas refrigerant, the liquid is sucked into the outlet pipe 117 from the first liquid return port 121A and is sent from the accumulator 105 to the compressor 104 at a predetermined liquid mixing ratio.

  When the liquid level of the accumulator 105 is positioned above the second liquid return port 121B, the liquid is also sucked from the second liquid return port 121B, and the liquid mixing rate increases. The liquid mixing ratio is adjusted by the hole diameters of the two liquid return ports 121A and 121B and the hole diameter of the pressure equalizing hole 122.

  Here, in this embodiment, the refrigerant is changed from the conventional R410A to R32 having a smaller warming coefficient. When R32 is used as a refrigerant, the discharge temperature of the compressor 104 increases by 10 to 15 ° C. In the present embodiment, in order to suppress an increase in the discharge temperature, the entrance degree of the compressor 104 is set to be smaller than that in the prior art.

  Therefore, the accumulator 105 of the present embodiment accumulates more liquid refrigerant than the conventional refrigerant R410A. When the accumulator 105 accumulates more liquid refrigerant than before, the lubricating oil mixing ratio in the mixed liquid that accumulates in the lower part of the accumulator 105 decreases.

  FIG. 3 shows the mixing characteristics of refrigerant and lubricating oil when R32 is used as the refrigerant. In the refrigerant R32, when the mixing ratio of the lubricating oil is 40% or less, a two-layer separation region of the liquid refrigerant and the lubricating oil appears in the low temperature region. That is, the liquid refrigerant is accumulated below the accumulator 105, and a lubricating oil layer is formed on the liquid refrigerant layer.

  When the condition of the two-layer separation zone is satisfied, the mixed liquid is separated into the liquid refrigerant and the lubricating oil below the accumulator 105. If the density of the lubricating oil is smaller than the density of the liquid refrigerant, the lubricating oil will float upward. When the lubricating oil floats above the liquid refrigerant, the lubricating oil is not sucked into the outlet pipe 117 from the first liquid return port 121A, and the amount of lubricating oil supplied to the compressor 104 decreases. If the amount of lubricating oil sent to the compressor 104 decreases, problems such as poor lubrication may occur and reliability may decrease.

  Therefore, in this embodiment, the shape (pipe area, pipe length, etc.) of the oil return capillary 107 is set so that the lubricating oil recovered by the oil separator 106 returns to the accumulator 105 by a predetermined amount or more. The adjustment method is shown below.

  The ratio of the liquid flowing from the accumulator 105 to the compressor 104 is R (= (refrigerant liquid flow rate + lubricating oil flow rate) / (refrigerant total flow rate), and the two-layer separation limit of the mixed liquid of the liquid refrigerant and the lubricating oil in the accumulator 105 (mixing) The lubricating oil mixing rate in the liquid dissolution zone and the separation zone) is n (= lubricating oil amount / refrigerant liquid amount), and the lubricating oil return rate x (= lubricating oil flow rate / refrigerant total flow rate) flowing through the oil return capillary 107. ), And the lubricating oil circulation rate y (= lubricating oil flow rate / refrigerant total flow rate) flowing from the oil separator 106 to the refrigeration cycle.

The lubricating oil return rate x flowing through the return oil capillary 107 is obtained by the following equation (1).
x ≧ n × R−y (1)

In the case of the characteristics shown in FIG. 3, if the mixing ratio of the lubricating oil is 40% (n = 0.4) or more, preferably 50% (n = 0.5) or more, the occurrence of two-layer separation can be suppressed. Conceivable. Therefore, the above equation (2) is
x ≧ 0.5 × R−y (2)
It becomes.

  The ratio R of the liquid flowing from the accumulator 105 to the compressor 104 is adjusted by the hole diameters of the liquid return ports 121A and 121B of the outlet pipe 117 of the accumulator 105 and the hole diameter of the pressure equalizing hole 122. The lubricating oil circulation rate y flowing from the oil separator 106 to the refrigeration cycle is determined by the characteristics of the compressor 104 and the oil separator 106.

  Thus, when R32 is used as the refrigerant, it is necessary to increase the amount of liquid refrigerant accumulated in the accumulator 105, and as a result, the lubricating oil mixing ratio is lowered. However, in this embodiment, since the lubricating oil recovered by the oil separator 106 is returned to the accumulator 105 more than before, the lubricating oil mixing ratio in the accumulator 105 is set to a predetermined value (40% or more, preferably 50% or more). Can be increased. Therefore, according to the present embodiment, it is possible to prevent the generation condition of the two-layer separation zone in the accumulator 105 from being satisfied, thereby suppressing the separation of the liquid refrigerant and the lubricating oil, and sufficient lubricating oil for the compressor 104. Can be sent in.

  In addition, this invention is not limited to the Example mentioned above. A person skilled in the art can make various additions and changes within the scope of the present invention. For example, the means for returning the lubricating oil from the oil separator to the accumulator is not limited to the oil return capillary, and other means may be used. Further, the present invention provides, for example, “an outdoor unit used in an air conditioner, wherein R32 alone or a mixed refrigerant containing R32 in a predetermined mass percentage or more is used as the refrigerant, and the compressor is a liquid refrigerant. It can also be expressed as an outdoor unit for an air conditioner that supplies a refrigerant mixed with a lubricating oil of a predetermined value or more so that two-layer separation between the lubricating oil and the lubricating oil does not occur.

  1: air conditioner, 100: outdoor unit, 101: outdoor heat exchanger, 103: outdoor expansion valve, 104: compressor, 105: accumulator, 106: oil separator, 107: oil return capillary, 108: four-way valve, 109 : Supercooling heat exchanger

Claims (4)

In an air conditioner that connects an indoor unit and an outdoor unit via a pipe and circulates a refrigerant,
As the refrigerant, R32 single refrigerant or a mixed refrigerant containing R32 in a predetermined mass percent or more,
The compressor of the outdoor unit is supplied with a refrigerant mixed with a lubricating oil of a predetermined value or more so that two-layer separation between the liquid refrigerant and the lubricating oil does not occur.
Air conditioner. The outdoor unit is
The compressor;
An oil separator connected to the discharge side of the compressor and separating and recovering oil in the refrigerant discharged from the compressor;
An accumulator connected to the inflow side of the compressor, separating and storing liquid refrigerant from the refrigerant, and supplying gas refrigerant to the compressor;
Supply oil for adjusting the lubricating oil mixing ratio in the mixed liquid of the liquid refrigerant and lubricating oil accumulated in the accumulator to the predetermined value or more by returning the lubricating oil separated by the oil separator to the accumulator An amount adjustment unit;
An air conditioner according to claim 1. X (x = lubricant oil flow rate / refrigerant total flow rate), the return rate of the lubricating oil returned from the oil separator to the accumulator by the supply oil amount adjustment unit,
The ratio of the mixed liquid flowing from the accumulator to the compressor is R (R = (liquid refrigerant flow rate + lubricant oil flow rate) / refrigerant total flow rate),
N (n = lubricating oil amount / liquid refrigerant amount), the limit lubricating oil mixing ratio at which the mixed liquid of the liquid refrigerant and lubricating oil in the accumulator is separated into two layers,
When the circulation ratio of the lubricating oil flowing from the oil separator to a refrigeration cycle was y (y = lubricating oil flow rate / coolant total flow), x ≧ n · R- y is satisfied,
The air conditioner according to claim 2. The value of n is set to 0.4 or more,
The air conditioner according to claim 3.

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