JP2020134081A - Air conditioning device - Google Patents

Abstract

To provide an air conditioning device capable of surely separating a refrigerator oil from a refrigerant by an oil separator regardless of a rotating speed of a compressor.SOLUTION: A cross sectional area of a discharge pipe 40 is determined to be smaller than a cross sectional area of an outflow pipe 41. Concretely, an inner diameter dimension D1 of the discharge pipe 40 is smaller than an inner diameter dimension D2 of the outflow pipe 41. Here, the inner diameter dimension D1 of the discharge pipe 40 may be determined so that a flow rate of a refrigerant including a refrigerator oil flowing in the discharge pipe 40 becomes a prescribed value in driving a compressor 20 at a lowest rotating speed possible in controlling, in the compressor 20 mounted on an air conditioning device 1. The prescribed value of the flow rate may be determined to achieve magnitude of centrifugal force acting on the refrigerant included in the refrigerator oil inside of a sealed container 21 of an oil separator 21, so that an amount of the refrigerator oil separating from the refrigerant by the oil separator 21 and returning to the compressor 20 becomes an amount to secure lubrication of the compressor 20.SELECTED DRAWING: Figure 2

Description

The present invention relates to an air conditioner in which an oil separator is connected to the refrigerant discharge side of a compressor.

On the refrigerant discharge side of the compressor, there is an air conditioner that connects an oil separator that separates the refrigerating machine oil discharged from the compressor together with the refrigerant from the refrigerant. The oil separator forms a swirling flow in which a refrigerant containing refrigerating machine oil flows into the wall surface of the cylindrical closed container from the tangential direction and flows in the circumferential direction of the wall surface of the closed container. It is common to use a so-called centrifugal oil separator that separates the oil (for example, Patent Document 1).

JP-A-2002-213843

In winter when the outside air temperature is low, the gas refrigerant that stays inside the compressor condenses into a liquid refrigerant, and this liquid refrigerant dissolves in the refrigerating machine oil that stays at the bottom of the compressor, so-called stagnation of the refrigerant may occur. is there. In this way, when the compressor is started to start the heating operation while the refrigerant is lying down, the temperature inside the closed container rises and the liquid refrigerant dissolved in the refrigerating machine oil evaporates rapidly. So-called oil forming in which the refrigerating machine oil foams occurs, and this oil forming causes a large amount of refrigerating machine oil to be discharged from the compressor together with the refrigerant.

Even if a large amount of refrigerating machine oil is discharged from the compressor at the start of heating operation as described above, it is necessary to lubricate the compressor by separating the refrigerating machine oil from the refrigerant with an oil separator and returning the separated refrigerating machine oil to the compressor. If the amount of refrigerating machine oil can be secured, it is possible to prevent the compressor from becoming poorly lubricated. On the other hand, when the heating operation is started in an environment where the outside air temperature is very low (for example, -5 ° C or less), the refrigerant pressure (low pressure) on the suction side of the compressor can be determined uniquely to the compressor. In order not to fall below the lower limit of the pressure range, the compressor slowly increases the rotation speed as compared with the case where the outside air temperature is a normal temperature.

In the above-mentioned centrifugal oil separator, the faster the flow velocity when the refrigerant containing the refrigerating machine oil flows into the oil separator, the stronger the centrifugal force acts, so that the refrigerating machine oil is easily separated from the refrigerant. However, as described above, when the heating operation is started in an environment where the outside air temperature is very low, the rotation speed of the compressor is slowly increased, so that the rotation speed of the compressor is high to some extent immediately after the start of the compressor. Until the number reaches the number, the flow speed when the refrigerant containing the compressor oil flows into the oil separator becomes slow, and it becomes difficult for the oil separator to separate the oil from the refrigerant. As a result, the amount of refrigerating machine oil returning to the compressor decreases, the amount of refrigerating machine oil staying inside the compressor becomes insufficient, and the compressor may cause poor lubrication.

The present invention solves the above-mentioned problems, and an object of the present invention is to provide an air conditioner capable of reliably separating refrigerating machine oil from a refrigerant with an oil separator.

In order to solve the above problems, the air conditioner of the present invention uses a compressor, an oil separator, a flow path switching valve, a discharge pipe, an outflow pipe, a suction pipe, and an oil return pipe as an outdoor unit. Have. The refrigerant discharge side of the compressor and the oil separator are connected by a discharge pipe, the oil separator and the flow path switching valve are connected by an outflow pipe, the compressor and the flow path switching valve are connected by a suction pipe, and the oil separator and The suction pipe is connected to the oil return pipe. The oil separator is a centrifugal oil separator that separates the refrigerant and the refrigerating machine oil by centrifugal force using the refrigerant containing the refrigerating machine oil flowing into the oil separator as a swirling flow, and the flow path cross section of the discharge pipe is the outflow pipe. It is made smaller than the flow path cross section of.

In the air conditioner of the present invention as described above, the flow path cross-sectional area of the discharge pipe connecting the compressor and the oil separator is smaller than the flow path cross-sectional area of the outflow pipe connecting the oil separator and the outdoor heat exchanger. To do. As a result, the flow velocity of the refrigerant containing the refrigerating machine oil flowing into the oil separator becomes faster, and the refrigerating machine oil is easily separated from the refrigerant by the oil separator, so that a sufficient amount of refrigerating machine oil is compressed from the oil separator to lubricate the compressor. It can be returned to the machine.

It is a refrigerant circuit diagram of the air conditioner according to the embodiment of this invention. It is a drawing which shows the connection state of a compressor and an oil separator in embodiment of this invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. As an embodiment, an air conditioner in which 10 indoor units are connected in parallel to the outdoor unit and all the indoor units can be simultaneously cooled or heated will be described as an example. The present invention is not limited to the following embodiments, and various modifications can be made without departing from the gist of the present invention.

As shown in FIG. 1, the air conditioner 1 in the present embodiment includes one outdoor unit 2 and 10 indoor units 5-1 connected in parallel to the outdoor unit 2 by a liquid pipe 8 and a gas pipe 9. ~ 5-10 (in FIG. 1, only two indoor units 5-1 and 5-10 are drawn). More specifically, the closing valve 25 of the outdoor unit 2 and the liquid pipe connecting portion 53 of each indoor unit 5 are connected by a liquid pipe 8. Further, the closing valve 26 of the outdoor unit 2 and the gas pipe connecting portion 54 of each indoor unit 5 are connected by a gas pipe 9. In this way, the outdoor unit 2 and the 10 indoor units 5 are connected by the liquid pipe 8 and the gas pipe 9, and the refrigerant circuit 10 of the air conditioner 1 is formed.

<Outdoor unit configuration>
First, the outdoor unit 2 will be described. The outdoor unit 2 includes a compressor 20, an oil separator 21, a four-way valve 22 which is a flow path switching valve, an outdoor heat exchanger 23, an outdoor unit expansion valve 24, and a closing valve 25 to which a liquid pipe 8 is connected. A closing valve 26 to which the gas pipe 9 is connected, an accumulator 27, and an outdoor unit fan 28 are provided. Then, each of these devices except the outdoor unit fan 28 is connected to each other by each refrigerant pipe described in detail below to form an outdoor unit refrigerant circuit 20 forming a part of the refrigerant circuit 10.

The compressor 20 is a variable capacity compressor whose operating capacity can be changed by being driven by a motor (not shown) whose rotation speed is controlled by an inverter. The refrigerant discharge side of the compressor 20 is connected to the oil separator 21 described later by a discharge pipe 40. Further, the refrigerant suction side of the compressor 20 is connected to the refrigerant outflow side of the accumulator 27 by a suction pipe 42.

The oil separator 21 is a centrifugal oil separator having a cylindrical closed container 21a. As shown in FIG. 2, the upper surface portion 21aa of the closed container 21a of the oil separator 21 and the port a of the four-way valve 22 described later are connected by an outflow pipe 41. Specifically, a part of the outflow pipe 41 penetrates the upper surface portion 21aa of the closed container 21a and is arranged inside the closed container 21a, and the open end of the outflow pipe 41 is from the central portion in the height direction of the closed container 21a. Placed below. Further, one end of an oil return pipe 47, which will be described later, is connected to the lower surface portion 21ab of the closed container 21a of the oil separator 21. Specifically, a part of the oil return pipe 47 penetrates the lower surface portion 21ab of the closed container 21a and is arranged inside the closed container 21a, and the open end of the oil return pipe 47 is the open end of the outflow pipe 41 described above. It is arranged lower and facing the open end of the outflow pipe 41. The other end of the oil return pipe 47 is connected to the suction pipe 42, and the oil return pipe 47 is provided with a capillary tube 29.

A discharge pipe 40 is connected to the upper portion of the side surface portion 21ac of the closed container 21a of the oil separator 21. Specifically, a part of the discharge pipe 40 penetrates the upper part of the side surface portion 21ac of the closed container 21a and is arranged inside the closed container 21a, and the open end of the discharge pipe 40 faces the inner wall surface of the closed container 21a. Have been placed. By connecting the discharge pipe 40, the outflow pipe 41, and the oil return pipe 47 to the closed container 21a of the oil separator 21 in this way, the discharge pipe 20 is discharged from the compressor 20 and the closed container 21a is discharged via the discharge pipe 40. The refrigerant containing the refrigerating machine oil that has flowed into the inside is separated into the refrigerant and the refrigerating machine oil inside the closed container 21a, the separated refrigerating machine oil returns to the compressor 20 via the oil return pipe 47, and the separated refrigerant is returned to the compressor 20. It flows out to the outflow pipe 41. Although the refrigerant flows into the oil return pipe 47 together with the refrigerating machine oil, the amount of the refrigerant flowing into the compressor 20 is regulated by the capillary tube 29 provided in the oil return pipe 47.

The separation of the refrigerant and the refrigerating machine oil in the oil separator 21 will be described in detail later.

The four-way valve 22 is a valve for switching the flow direction of the refrigerant in the refrigerant circuit 10, and includes four ports a, b, c, and d. As described above, the port a is connected to the closed container 21a of the oil separator 21 by the discharge pipe 40. The port b is connected to one of the refrigerant inlets and outlets of the outdoor heat exchanger 23 by a refrigerant pipe 43. The port c is connected to the refrigerant inflow side of the accumulator 27 by a refrigerant pipe 46. The port d is connected to the closing valve 26 by the outdoor unit gas pipe 45.

The outdoor heat exchanger 23 exchanges heat between the refrigerant and the outside air taken into the outdoor unit 2 by the rotation of the outdoor unit fan 28 described later. As described above, one refrigerant inlet / outlet of the outdoor heat exchanger 23 and the port b of the four-way valve 22 are connected by a refrigerant pipe 43. Further, the other refrigerant inlet / outlet of the outdoor heat exchanger 23 and the closing valve 25 are connected by an outdoor unit liquid pipe 44. The outdoor heat exchanger 23 functions as a condenser when the air conditioner 1 performs a cooling operation, and functions as an evaporator when the air conditioner 1 performs a heating operation.

The outdoor unit expansion valve 24 is provided in the outdoor unit liquid pipe 44. The outdoor unit expansion valve 24 is an electronic expansion valve driven by a pulse motor (not shown), and the amount of refrigerant flowing into the outdoor heat exchanger 23 or the amount of refrigerant flowing into the outdoor heat exchanger 23 by adjusting the opening degree according to the number of pulses given to the pulse motor, or , The amount of refrigerant flowing out from the outdoor heat exchanger 23 is adjusted. The opening degree of the outdoor unit expansion valve 24 is the temperature of the refrigerant discharged from the compressor 21 when the air conditioner 1 is performing the heating operation, and the discharge temperature is the temperature of the indoor units 5-1 to 5-1. The opening degree is adjusted so that the target temperature is determined based on the heating capacity required for each. Further, the opening degree of the outdoor unit expansion valve 24 is fully opened when the cooling operation is performed.

As described above, in the accumulator 27, the refrigerant inflow side is connected to the port c of the four-way valve 22 by the refrigerant pipe 46, and the refrigerant outflow side is connected to the refrigerant suction side of the compressor 20 by the suction pipe 42. The accumulator 27 separates the refrigerant flowing into the accumulator 28 from the refrigerant pipe 46 into a gas refrigerant and a liquid refrigerant, and causes the compressor 20 to suck only the gas refrigerant.

The outdoor unit fan 28 is made of a resin material and is arranged in the vicinity of the outdoor heat exchanger 23. The outdoor unit fan 28 is rotated by a fan motor (not shown) to take in outside air from a suction port (not shown) into the outdoor unit 2 and exchange heat with the refrigerant in the outdoor heat exchanger 23 from an outlet (not shown) to the outside. It is released to the outside of the machine 2.

In addition to the configuration described above, the outdoor unit 2 is provided with various sensors. As shown in FIG. 1, the discharge pipe 40 has a discharge pressure sensor 31 that detects the discharge pressure, which is the pressure of the refrigerant discharged from the compressor 20, and a discharge that detects the temperature of the refrigerant discharged from the compressor 20. A temperature sensor 33 is provided. In the vicinity of the refrigerant inlet of the accumulator 28 in the refrigerant pipe 46, a suction pressure sensor 32 that detects the suction pressure, which is the pressure of the refrigerant sucked into the compressor 20, and the temperature of the refrigerant sucked into the compressor 20 are detected. A suction temperature sensor 34 is provided.

The temperature of the refrigerant flowing into the outdoor heat exchanger 23 or the temperature of the refrigerant flowing out of the outdoor heat exchanger 23 is detected between the outdoor heat exchanger 23 and the outdoor unit expansion valve 24 in the outdoor unit liquid pipe 44. A heat exchange temperature sensor 35 is provided for this purpose. An outside air temperature sensor 36 for detecting the temperature of the outside air flowing into the inside of the outdoor unit 2, that is, the outside air temperature is provided in the vicinity of the suction port (not shown) of the outdoor unit 2.

<Configuration of each indoor unit>
Next, 10 indoor units 5-1 to 5-10 will be described. The 10 indoor units 5-1 to 5-10 all have the same configuration, and include an indoor heat exchanger 51, an indoor unit expansion valve 52, a liquid pipe connecting portion 53, a gas pipe connecting portion 54, and the like. It is equipped with an indoor unit fan 55. Each of these components except the indoor unit fan 55 is connected to each other by the refrigerant pipes described in detail below to form an indoor unit refrigerant circuit 50 that forms a part of the refrigerant circuit 10.

The indoor heat exchanger 51 exchanges heat between the refrigerant and the indoor air taken into the interior of the indoor unit 5 from a suction port (not shown) by the rotation of the indoor unit fan 55 described later. One refrigerant inlet / outlet of the indoor heat exchanger 51 and the liquid pipe connecting portion 53 are connected by the indoor unit liquid pipe 71, and the other refrigerant inlet / outlet and the gas pipe connecting portion 54a are connected by the indoor unit gas pipe 72. The indoor heat exchanger 51 functions as an evaporator when the air conditioner 1 performs a cooling operation, and functions as a condenser when the air conditioner 1 performs a heating operation. The liquid pipe connecting portion 53 and the gas pipe connecting portion 54 are connected to each refrigerant pipe by welding, flare nuts, or the like.

The indoor unit expansion valve 52 is provided in the indoor unit liquid pipe 71. The indoor unit expansion valve 52 is an electronic expansion valve, and when the indoor heat exchanger 51 functions as an evaporator, that is, when the indoor unit 5 performs a cooling operation, the opening degree thereof is the refrigerant outlet of the indoor heat exchanger 51 ( The degree of refrigerant superheat at the gas pipe connection portion 54 side) is adjusted to be the target degree of refrigerant superheat. Further, when the indoor unit expansion valve 52 functions as a condenser, that is, when the indoor unit 5 performs a heating operation, the opening degree of the indoor unit expansion valve 52 is the refrigerant outlet (liquid pipe connection) of the indoor heat exchanger 51. The degree of refrigerant supercooling on the unit 53 side) is adjusted to be the target degree of refrigerant supercooling. Here, the target refrigerant superheat degree and the target refrigerant supercooling degree are the refrigerant superheat degree and the refrigerant supercooling degree necessary for each of the indoor units 5-1 to 5-10 to exhibit sufficient cooling capacity or heating capacity. Is.

The indoor unit fan 55 is made of a resin material and is arranged in the vicinity of the indoor heat exchanger 51. The indoor unit fan 55 is rotated by a fan motor (not shown) to take indoor air into the indoor unit 5 from a suction port (not shown), and an outlet (not shown) that exchanges heat with the refrigerant in the indoor heat exchanger 51. Is released into the room.

In addition to the configuration described above, the indoor unit 5 is provided with various sensors. A liquid side temperature sensor 61 that detects the temperature of the refrigerant flowing into or out of the indoor heat exchanger 51 between the indoor heat exchanger 51 and the indoor unit expansion valve 52 in the indoor unit liquid pipe 71. Is provided. The indoor unit gas pipe 72 is provided with a gas side temperature sensor 62 that detects the temperature of the refrigerant flowing out of the indoor heat exchanger 51 or flowing into the indoor heat exchanger 51. An indoor temperature sensor 63 that detects the temperature of the indoor air flowing into the interior of the indoor unit 5 is provided in the vicinity of the suction port (not shown) of the indoor unit 5.

<Operation of refrigerant circuit>
Next, the flow of the refrigerant and the operation of each part in the refrigerant circuit 10 during the air conditioning operation of the air conditioning device 1 in the present embodiment will be described with reference to FIG. In the following description, first, a case where the air conditioner 1 performs a heating operation will be described, and then a case where the air conditioner 1 performs a cooling operation will be described. The solid arrow in FIG. 1 indicates the flow of the refrigerant during the heating operation. Further, the broken line arrow in FIG. 1 indicates the flow of the refrigerant during the cooling operation.

<Heating operation>
As shown in FIG. 1, when the air conditioner 1 performs the heating operation, the four-way valve 22 is in a state shown by a solid line, that is, so that the port a and the port d of the four-way valve 22 communicate with each other and the port b. And port c are switched so as to communicate with each other. As a result, the refrigerant circuit 10 becomes a heating cycle in which each indoor heat exchanger 51 functions as a condenser and the outdoor heat exchanger 23 functions as an evaporator.

When the compressor 20 is driven while the refrigerant circuit 10 functions as a heating cycle, the refrigerant discharged from the compressor 20 flows through the discharge pipe 40 and flows into the oil separator 21 and flows from the oil separator 21 to the outflow pipe 41. And flow into the four-way valve 22. Then, the refrigerant flowing out from the four-way valve 22 flows through the outdoor unit gas pipe 45 and flows into the gas pipe 9 through the closing valve 26. In the oil separator 21, the refrigerating machine oil discharged from the compressor 20 together with the refrigerant is separated from the refrigerant, and the separated refrigerating machine oil flows out from the oil separator 21 and is returned to the oil as shown by the alternate long and short dash line arrow in FIG. It flows through the pipe 47 and is returned to the compressor 20 via the suction pipe 42.

The refrigerant flowing through the gas pipe 9 is distributed to the indoor units 5-1 to 5-10 via each gas pipe connecting portion 54. The refrigerant that has flowed into the indoor units 5-1 to 5-10 flows through each indoor unit gas pipe 72 and flows into each indoor heat exchanger 51. The refrigerant flowing into each indoor heat exchanger 51 exchanges heat with the indoor air taken into each indoor unit 5 by the rotation of each indoor unit fan 55 and condenses.

In this way, each indoor heat exchanger 51 functions as a condenser, and each indoor heat exchanger 51 exchanges heat with the refrigerant, and the heated indoor air is blown into the room from an outlet (not shown). The room in which the indoor units 5-1 to 5-10 are installed is heated.

The opening degree of the refrigerant flowing from each indoor heat exchanger 51 into each indoor unit liquid pipe 71 is adjusted so that the degree of refrigerant supercooling on the refrigerant outlet side of each indoor heat exchanger 51 becomes the target degree of refrigerant supercooling. The pressure is reduced when passing through each indoor unit expansion valve 52. Here, the target refrigerant supercooling degree is determined based on the heating capacity required for each of the indoor units 5-1 to 5-10. Further, the heating capacity is determined in each indoor unit 5-1 to 5-10 based on the temperature difference between the set temperature and the detected indoor temperature.

The refrigerant decompressed by each indoor unit expansion valve 52 flows out from each indoor unit liquid pipe 71 to the liquid pipe 8 via each liquid pipe connection portion 53. The refrigerant that merges in the liquid pipe 8 and flows into the outdoor unit 2 through the closing valve 25 flows through the outdoor unit liquid pipe 44, and the opening degree is adjusted so that the discharge temperature of the compressor 20 becomes the target temperature. The pressure is further reduced as it passes through the valve 24.

The refrigerant decompressed by the outdoor unit expansion valve 24 flows through the outdoor unit liquid pipe 44, flows into the outdoor heat exchanger 23, and is taken into the outdoor unit 5 by the rotation of the outdoor unit fan 28, which is the maximum rotation speed. It evaporates by exchanging heat with the outside air. The refrigerant flowing from the outdoor heat exchanger 23 into the refrigerant pipe 43 flows in the order of the four-way valve 22, the refrigerant pipe 46, the accumulator 27, and the suction pipe 42, is sucked into the compressor 20, and is compressed again.

<Cooling operation>
When the air conditioner 1 performs the cooling operation, as shown in FIG. 1, the four-way valve 22 is in a state shown by a broken line, that is, so that the port a and the port b of the four-way valve 22 communicate with each other and the port c. And port d are switched so as to communicate with each other. As a result, the refrigerant circuit 10 becomes a heating cycle in which each indoor heat exchanger 51 functions as an evaporator and the outdoor heat exchanger 23 functions as a condenser.

When the compressor 20 is driven in a state where the refrigerant circuit 10 functions as a cooling cycle, the refrigerant discharged from the compressor 20 flows through the discharge pipe 40 and flows into the oil separator 21 and flows from the oil separator 21 to the outflow pipe 41. And flow into the four-way valve 22. Then, the refrigerant flowing out of the four-way valve 22 flows through the refrigerant pipe 43 and flows into the outdoor heat exchanger 23. The refrigerant that has flowed into the outdoor heat exchanger 23 exchanges heat with the outside air taken into the outdoor unit 2 by the rotation of the outdoor unit fan 28 and condenses. The refrigerant flowing out from the outdoor heat exchanger 23 to the outdoor unit liquid pipe 44 passes through the outdoor unit expansion valve 24 having a fully opened opening, and flows out to the liquid pipe 8 through the closing valve 25. In the oil separator 21, the refrigerating machine oil discharged from the compressor 20 together with the refrigerant is separated from the refrigerant, and the separated refrigerating machine oil flows out from the oil separator 21 and is returned to the oil as shown by the alternate long and short dash line arrow in FIG. It flows through the pipe 47 and is returned to the compressor 20 via the suction pipe 42.

The refrigerant flowing through the liquid pipe 8 flows into the indoor units 5-1 to 5-10 via each liquid pipe connecting portion 53. The refrigerant flowing into the indoor units 5-1 to 5-10 flows through each indoor unit liquid pipe 71, and the opening degree is such that the refrigerant superheat degree at each refrigerant outlet of each indoor heat exchanger 51 becomes the target refrigerant superheat degree. Is depressurized as it passes through each of the adjusted indoor unit expansion valves 52. Here, the target refrigerant superheat degree is determined based on the cooling capacity required for each of the indoor units 5-1 to 5-10. Further, the cooling capacity is determined in each indoor unit 5-1 to 5-10 based on the temperature difference between the set temperature and the detected indoor temperature.

The refrigerant flowing from each indoor unit liquid pipe 71 into each indoor heat exchanger 51 exchanges heat with the indoor air taken into the indoor units 5-1 to 5-10 by the rotation of each indoor unit fan 55. Evaporate. In this way, each indoor heat exchanger 51 functions as an evaporator, and the indoor heat exchanger 51 exchanges heat with the refrigerant to blow out the cooled indoor air from an outlet (not shown) into the room. The room in which the indoor units 5-1 to 5-10 are installed is cooled.

The refrigerant flowing out from each indoor heat exchanger 51 to each indoor unit gas pipe 72 flows out to the gas pipe 9 via each gas pipe connecting portion 54. The refrigerant that merges at the gas pipe 9 and flows into the outdoor unit 2 via the closing valve 26 flows in the order of the outdoor unit gas pipe 45, the four-way valve 22, the refrigerant pipe 46, the accumulator 27, and the suction pipe 42, and is sucked into the compressor 20. And compressed again.

<Effect of the difference in inner diameter between the discharge pipe and the inflow pipe on the separation of refrigerating machine oil by the oil separator>
Next, the separation of the refrigerant and the refrigerating machine oil in the oil separator 21 in the present embodiment will be described in detail mainly with reference to FIG.

As described above, a part of the discharge pipe 40 is arranged inside the closed container 21a through the upper part of the side surface portion 21ac of the closed container 21a of the oil separator 21, and the open end of the discharge pipe 40 is the closed container 21a. It is arranged toward the inner wall surface of. As a result, the refrigerant containing the refrigerating machine oil discharged from the compressor 20, flowing through the discharge pipe 40 and flowing into the closed container 21a of the oil separator 21 flows in the tangential direction of the inner wall surface of the closed container 21a of the oil separator 21. A swirling flow is formed in the circumferential direction of the inner wall surface of the closed container 21a, and the centrifugal force generated by the swirling flow separates the refrigerating machine oil from the refrigerant.

When the refrigerant containing the refrigerating machine oil flows from the discharge pipe 40 into the closed container 21a of the oil separator 21 as described above, the faster the flow velocity, the stronger the centrifugal force acts on the refrigerant containing the refrigerating machine oil, so that the refrigerating machine oil is separated from the refrigerant. It becomes easy to be done. The flow velocity of the refrigerant containing the refrigerating machine oil flowing into the closed container 21a changes depending on the rotation speed of the compressor 20, and the higher the rotation speed of the compressor 20, the faster the flow velocity.

Therefore, when the compressor 20 is driven at a high rotation speed, the refrigerating machine oil is easily separated from the refrigerant by the oil separator 21, so that a large amount of the oil separator 21 is sent to the compressor 20 via the oil return pipe 47. Since the refrigerating machine oil is returned, the compressor 20 does not run out of refrigerating machine oil and the compressor 20 does not cause poor lubrication.

However, when the air conditioner 1 is operating in air conditioning, the compressor 20 is not always operating at a high rotation speed. For example, when the air conditioner 1 starts the heating operation in an environment where the outside air temperature is very low (for example, −5 ° C. or lower), the refrigerant pressure (low pressure) on the suction side of the compressor 20 is unique to the compressor 20. In order not to fall below the lower limit of the usable pressure range defined in the above, the compressor 20 slowly raises the rotation speed as compared with the case where the outside air temperature is a normal temperature.

In this way, when the rotation speed of the compressor 20 is slowly increased, the oil separator 21 contains the refrigerating machine oil from immediately after the start of the compressor 20 until the rotation speed of the compressor 20 reaches a certain high rotation speed. The flow speed when the refrigerant flows in becomes slow, and it becomes difficult for the oil separator 21 to separate the oil from the refrigerant. As a result, the amount of refrigerating machine oil returning from the oil separator 21 to the compressor 20 is insufficient, and the compressor 20 may cause poor lubrication.

In particular, when the refrigerant has fallen inside the compressor 20 in an environment where the outside air temperature is low in winter and a large amount of refrigerating machine oil is discharged together with the refrigerant at the start of the heating operation, the refrigerating machine oil is discharged by the oil separator 21. Poor lubrication due to difficulty in separation is likely to occur. Further, in a device such as the air conditioner 1 of the present embodiment in which a large number of indoor units 5 are connected to one outdoor unit 2, a compressor 20 having a large exclusion volume is mounted on the outdoor unit 2, as described above. Since a large amount of refrigerating machine oil is sealed in the compressor 20 having a large exclusion volume, the amount of refrigerating machine oil staying inside the compressor 20 is reduced due to the difficulty in separating the refrigerating machine oil by the oil separator 21. Therefore, poor lubrication is likely to occur.

Therefore, in the air conditioner 1 of the present embodiment, as shown in FIG. 2, the cross section of the inside of the discharge pipe 40, that is, the flow path through which the refrigerant containing the refrigerating machine oil flows in the discharge pipe 40 (hereinafter, the cross section of the flow path). Is smaller than the flow path cross section of the outflow pipe 41. Specifically, the inner diameter dimension D1 of the discharge pipe 40 is made smaller than the inner diameter dimension D2 of the outflow pipe 41. When the thickness dimension of the pipe wall of the discharge pipe 40 and the outflow pipe 41 is the same, the outer diameter dimension of the discharge pipe 40 may be smaller than the outer diameter dimension of the outflow pipe 41. For example, the outer diameter of the discharge pipe 40 may be 10 mm, and the outer diameter of the outflow pipe 41 may be 13 mm.

In a general air conditioner, when the oil separator 21 is provided on the refrigerant discharge side of the compressor 20, the discharge pipe 40 and the outflow pipe 41 use pipes having the same flow path cross section. On the other hand, in the air conditioner 1 of the present embodiment, the flow path cross section of the discharge pipe 40 is made smaller than the flow path cross section of the outflow pipe 41. As a result, the flow velocity of the refrigerant containing the refrigerating machine oil when flowing through the discharge pipe 40 becomes faster than in the case where the discharge pipe 40 and the outflow pipe 41 have the same flow path cross-sectional area, so that the closed container of the oil separator 21 The centrifugal force acting on the refrigerant containing the refrigerating machine oil inside the 21 becomes large, and the refrigerating machine oil is easily separated from the refrigerant.

The inner diameter dimension D1 of the discharge pipe 40 includes the refrigerating machine oil that flows through the discharge pipe 40 when the compressor 20 mounted on the air conditioner 1 is driven at the lowest rotation speed that can be controlled by the compressor 20. It may be determined so that the flow velocity of the refrigerant becomes a predetermined value. The predetermined value of the flow velocity is the closed container 21 of the oil separator 21 so that the amount of refrigerating machine oil separated from the refrigerant by the oil separator 21 and returned to the compressor 20 is an amount that can always secure the lubrication of the compressor 20. It suffices to determine the magnitude of the centrifugal force acting on the refrigerant containing the refrigerating machine oil inside.

As described above, in the air conditioner 1 of the present embodiment, in the discharge pipe 40 and the outflow pipe 41 connected to the closed container 21a of the oil separator 21, the flow path cross section of the discharge pipe 40 is changed to the flow of the outflow pipe 41. Make it smaller than the road cross section. As a result, the flow velocity when the refrigerant containing the refrigerating machine oil flows through the discharge pipe 40 becomes faster, and the centrifugal force received by the refrigerant containing the refrigerating machine oil flowing into the centrifugal oil separator 21 increases. Refrigerant oil can be easily separated from the refrigerant. Therefore, even if the compressor 20 is driven at a low rotation speed, a sufficient amount of refrigerating machine oil can be returned from the oil separator 21 to the compressor 20, so that the compressor 20 can be prevented from being poorly lubricated.

1 Air conditioner 2 Outdoor unit 5-1 to 5-10 Indoor unit 20 Compressor 21 Oil separator 21a Sealed container 40 Discharge pipe 41 Outflow pipe 47 Oil return pipe D1 Inner diameter dimension of discharge pipe D2 Inner diameter dimension of outflow pipe

Claims (2)

The outdoor unit has a compressor, an oil separator, a flow path switching valve, a discharge pipe, an outflow pipe, a suction pipe, and an oil return pipe.
The refrigerant discharge side of the compressor and the oil separator are connected by the discharge pipe.
The oil separator and the flow path switching valve are connected by the outflow pipe.
The compressor and the flow path switching valve are connected by the suction pipe.
The oil separator and the suction pipe are connected by the oil return pipe, and the oil separator is connected to the suction pipe.
The oil separator is a centrifugal oil separator that separates the refrigerant and the refrigerating machine oil by centrifugal force using the refrigerant containing the refrigerating machine oil flowing into the oil separator as a swirling flow.
The flow path cross section of the discharge pipe is made smaller than the flow path cross section of the outflow pipe.
An air conditioner characterized by that. The flow path cross section of the discharge pipe is determined so that the flow velocity of the refrigerant containing the refrigerating machine oil flowing through the discharge pipe becomes a predetermined value when the compressor is driven at the minimum rotation speed that can be controlled.
The air conditioner according to claim 1.

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