JP2020060354A - Refrigerator and chiller mounted with the same - Google Patents

Abstract

To provide a refrigerator capable of securing an amount of oil in a compressor without increasing the amount of the oil to be filled therein and curbing a phenomenon that a coolant is returned from an oil separator to the compressor and to provide a chiller mounted with the refrigerator.SOLUTION: A refrigerator comprises: a compressor 10 which compresses a coolant; a condenser 12 which condenses the coolant compressed by the compressor 10; first coolant piping P1 which connects the compressor 10 and the condenser 12; second coolant piping P2 which is branched from the first coolant piping P1 at a branching section 40 and converged thereto again at a section downstream the branching section 40; an oil separator 18 which is installed on the second coolant piping P2 and separates oil from the coolant; oil return piping P6 which returns the oil separated by the oil separator 18 to the compressor 10; an on-off valve 20 which is installed on the oil return piping P6; and a control section 30 which switches between opening and closing of the on-off valve 20 in accordance with a loading state of the compressor 10.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a refrigerator and a chiller device including the refrigerator.

  Generally, the inside of a compressor included in a refrigerant circuit of a refrigerator is filled with lubricating oil in order to suppress wear of sliding parts. Part of the filled oil is discharged into the refrigerant circuit together with the refrigerant discharged from the compressor. At this time, it is necessary to control the amount of oil in the compressor in order to properly lubricate the sliding portion. In addition, if the refrigerant discharged from the compressor contains a large amount of oil, the efficiency of heat exchange in the heat exchanger is reduced. To cope with this, an oil separator may be provided in the refrigerant circuit to collect the oil contained in the refrigerant and then return it to the compressor.

  As an example of a configuration for returning oil to the compressor, Patent Literature 1 describes one oil separator provided for the two compressors in a refrigerant circuit including two compressors. . The oil collected in the oil separator is returned to each compressor via two oil recovery pipes. Further, it is described that one of the two oil recovery pipes is provided with an opening / closing valve, and the opening / closing valve is opened / closed by comparing with the operating frequency of each compressor.

  Further, Patent Document 2 describes one oil separator provided for two compressors in a refrigerant circuit including two compressors. The oil collected in the oil separator is returned to each compressor via two oil recovery pipes. Further, it is described that an electric valve is provided in the two oil recovery pipes, and the opening degree of each electric valve is adjusted according to the operating frequency of each compressor.

JP-A-64-58970 JP, 2013-108649, A

  For example, if the path length of the refrigerant circuit is short, such as in a chiller system, the oil discharged from the compressor together with the refrigerant returns to the compressor relatively quickly, so the oil separator as described above may be omitted. .

  However, if the oil separator is omitted, the refrigerant contains oil. In particular, in an overloaded state in which the compressor is rotating at high speed, the amount of oil contained in the refrigerant discharged from the compressor tends to increase. When the amount of oil contained in the refrigerant is large, the efficiency of heat exchange in the heat exchanger is reduced. In addition, it is necessary to increase the amount of oil to be filled in order to make up for the lack of oil in the compressor.

  On the other hand, when the oil separator is provided, when the oil is returned from the oil separator to the compressor, the oil may contain a part of the refrigerant. The refrigerant is returned to the compressor without performing refrigeration work, which is a loss to the work of the compressor.

  The present invention has been made in view of such circumstances, and secures the amount of oil in the compressor without increasing the amount of oil to be filled, and suppresses the phenomenon that the refrigerant returns from the oil separator to the compressor. The purpose is to

In order to solve the above-mentioned subject, the refrigerator of the present invention and the chiller device provided with it have adopted the following means.
That is, a refrigerator according to an aspect of the present invention includes a compressor that compresses a refrigerant, a condenser that condenses the refrigerant compressed by the compressor, and a first refrigerant that connects the compressor and the condenser. A pipe, a second refrigerant pipe branched from the first refrigerant pipe at a branch portion and joined again to the first refrigerant pipe downstream of the branch portion, and an oil in the refrigerant provided in the second refrigerant pipe An oil separator for separating the oil separator, an oil return pipe for returning the oil separated by the oil separator to the compressor, an on-off valve provided in the oil return pipe, and the on-off valve according to a load state of the compressor And a control unit for switching between opening and closing.

According to the refrigerator of the present aspect, the first refrigerant pipe can guide the refrigerant from the compressor to the condenser, and the second refrigerant pipe can guide a part of the refrigerant to the oil separator. In addition, for example, when the compressor is in a load state during normal operation (hereinafter referred to as “normal load state”) or a load state lower than that, the on-off valve provided in the oil return pipe is closed and the compressor is normally operated. The on-off valve can be opened when the load is overloaded rather than the load. At this time, for example, by setting the diameter of the first refrigerant pipe to be equal to or larger than the diameter of the second refrigerant pipe, most of the refrigerant is guided from the compressor to the condenser by the first refrigerant pipe under any load condition. The amount of the refrigerant introduced to the oil separator by the second refrigerant pipe can be reduced compared to that.
The oil separated by the oil separator may slightly contain the refrigerant compressed by the compressor. That is, when the oil is returned to the compressor as it is, the compressed refrigerant is inevitably returned from the oil separator to the compressor through the oil return pipe. This unavoidably returned refrigerant is a loss to the work of the compressor because it does not exchange heat in the condenser. However, when the oil return pipe is shut off by the opening / closing valve, a phenomenon in which some of the refrigerant returns from the oil separator to the compressor is suppressed, so that the loss of the work of the compressor can be suppressed. At this time, since the amount of oil discharged from the compressor (the oil contained in the refrigerant and discharged) is small in a normal load state or a low load state, the oil return pipe is shut off by the opening / closing valve to send the oil to the compressor. Even if it is not returned, the effect on the compressor (for example, oil shortage) can be ignored. On the other hand, when the overload state is higher than the normal load state, a large amount of oil is discharged from the compressor. For this reason, if the on-off valve shuts off the oil return pipe, an oil shortage occurs in the compressor. However, for example, by opening the open / close valve provided in the oil return pipe when the load is overloaded rather than the normal load, it is possible to return the oil accumulated in the oil separator to the compressor. The amount of oil can be secured. Therefore, it is not necessary to increase the amount of oil to be filled in the compressor in order to compensate for the lack of oil in the compressor that occurs during an overload condition.
Further, if the entire amount of the refrigerant passes through the oil separator, the oil will be accumulated in the oil separator in a short time. Therefore, in order to reduce the oil, it is necessary to frequently return the oil from the oil separator to the compressor. On the other hand, most of the refrigerant is introduced from the compressor to the condenser through the first refrigerant pipe, and the amount of the refrigerant introduced to the oil separator is smaller than that, so that the oil is collected in the oil separator. The time required for can be extended. That is, in order to reduce the amount of oil accumulated in the oil separator, the frequency of returning the oil from the oil separator to the compressor can be reduced. As a result, the frequency of the phenomenon in which the refrigerant returns from the oil separator to the compressor can be reduced, so that the loss of the work of the compressor can be suppressed.

  Further, in the refrigerator according to an aspect of the present invention, the control unit closes the on-off valve when the compressor is in a load state during normal operation or a load state lower than that, and the compressor The open / close valve is opened when the load is overloaded rather than the load during normal operation.

  According to the refrigerator of the present aspect, in the case of a normal load state in which the amount of oil discharged from the compressor is small or a load state lower than that, it is possible to close the on-off valve provided in the oil return pipe. Therefore, the phenomenon that some of the refrigerant returns from the oil separator to the compressor is suppressed, and the loss of the work of the compressor can be suppressed. On the other hand, when the amount of oil discharged from the compressor is large, it is possible to open the open / close valve in the case of an overload condition than that in the normal load condition. Therefore, the amount of oil in the compressor can be secured.

  In the refrigerator according to one aspect of the present invention, the first refrigerant pipe has a pipe diameter equal to or larger than that of the second refrigerant pipe.

  According to the refrigerator of this aspect, the amount of the refrigerant flowing through the first refrigerant pipe can be made equal to or more than the amount of the refrigerant flowing through the second refrigerant pipe. That is, the main flow of the refrigerant flow can be on the first refrigerant pipe side.

  Further, in the refrigerator according to an aspect of the present invention, a switching unit capable of switching a flow direction at the branch portion of the first refrigerant pipe is provided, and the control unit supplies the refrigerant when the opening / closing valve is in a closed state. The switching means is controlled so as not to be guided to the second refrigerant piping side, and the switching means is controlled so as to guide the refrigerant to the second refrigerant piping side when the on-off valve is in the open state.

In the refrigerator according to this aspect, the control unit can switch whether to guide the entire amount of the refrigerant to the oil separator or to bypass the refrigerant, and when the on-off valve is in the open state, the refrigerant is on the second refrigerant pipe side. So that the refrigerant is not guided to the second refrigerant pipe side when the on-off valve is closed. Thus, when the on-off valve is in the closed state (that is, when the load is under the normal load state and the oil is not returned from the oil separator to the compressor), the entire amount of the refrigerant bypasses the oil separator. For this reason, since the oil does not collect in the oil separator, it is not necessary to periodically return the oil from the oil separator to the compressor, and the frequency of the phenomenon that the refrigerant returns from the oil separator to the compressor can be further reduced.
On the other hand, when the open / close valve is in the open state (that is, when the oil is returned from the oil separator to the compressor in the overload state), the entire amount of the refrigerant is guided to the oil separator. As a result, the oil can be collected in the oil separator in a short time. Therefore, the amount of oil required in the compressor can be secured in a short time. In addition, even in an overloaded state in which a large amount of oil is discharged from the compressor, the oil contained in the refrigerant can be separated by the oil separator, so the heat in the heat exchanger (for example, a condenser) installed downstream is reduced. It is possible to suppress a decrease in exchange efficiency.
The switching means may be, for example, a three-way valve provided at a branch portion of the first refrigerant pipe, a first refrigerant pipe between the branch portion and the joining portion, and a second refrigerant pipe between the branch portion and the oil separator. There are two on-off valves installed in.

  Further, in the refrigerator according to the aspect of the present invention, the oil return pipe includes a bypass pipe that connects the upstream side and the downstream side of the on-off valve.

  In the refrigerator according to this aspect, the oil return pipe includes a bypass pipe that connects the upstream side and the downstream side of the on-off valve. This forms a circuit that bypasses the on-off valve. By setting the bypass pipe to a pipe diameter such that only oil flows, only oil can be returned from the oil separator to the compressor. Therefore, the frequency of returning the oil from the oil separator to the compressor on a regular basis can be reduced.

  Further, the control unit determines that the compressor is in a load state during normal operation or a load state lower than that when the rotation speed of the compressor is equal to or lower than a predetermined rotation speed, and exceeds the predetermined rotation speed. At this time, it is determined that the compressor is in an overload state rather than a load state during normal operation.

  The control unit can acquire the load state of the compressor from the rotation speed of the compressor.

  Further, the control unit determines that the compressor is in a load state during normal operation or a load state lower than that when the pressure difference between the suction side and the discharge side of the compressor is less than or equal to a predetermined pressure, and the predetermined When the pressure is exceeded, it is determined that the compressor is in an overload state rather than a load state during normal operation.

  The control unit can obtain the load state of the compressor from the pressure difference between the suction side and the discharge side of the compressor.

  A chiller facility according to one aspect of the present invention includes the above-mentioned refrigerator.

  According to the refrigerator and the chiller device including the same according to the present invention, it is possible to secure the amount of oil in the compressor without increasing the amount of oil to be filled, and suppress the phenomenon that the refrigerant returns from the oil separator to the compressor. .

It is the figure which showed the refrigerant circuit of the refrigerator which concerns on 1st Embodiment of this invention. It is the figure which showed the refrigerant circuit of the refrigerator which concerns on 2nd Embodiment of this invention. It is the figure which showed the modification of the refrigerant circuit of the refrigerator which concerns on 2nd Embodiment of this invention.

  A refrigerator according to an embodiment of the present invention will be described below with reference to the drawings. The refrigerator of the present embodiment is, for example, a refrigerator used in a chiller facility.

[First Embodiment]
First, the refrigerator according to the first embodiment of the present invention will be described.

  FIG. 1 shows a refrigerant circuit of a refrigerator according to this embodiment. The refrigerant circuit of the refrigerator is discharged from the compressor 10 that compresses the refrigerant, the condenser 12 that condenses the refrigerant, the expansion valve 14 that expands the refrigerant, the evaporator 16 that evaporates the refrigerant, and the compressor 10. And an oil separator 18 for separating oil contained in the refrigerant. In the refrigerant circuit, these devices are connected by a refrigerant pipe P1, a refrigerant pipe P2, a refrigerant pipe P3, a refrigerant pipe P4, a refrigerant pipe P5, and an oil return pipe P6. In addition, the refrigerator includes a control unit 30 that can communicate with each device and control each device.

  The compressor 10 is a device that compresses the refrigerant introduced from the evaporator 16. The compressor 10 is previously filled with oil for lubrication of the sliding portion. The discharge port of the compressor 10 is connected to the refrigerant inlet of the condenser 12 via the first refrigerant pipe P1.

  The condenser 12 is a heat exchanger that condenses the refrigerant compressed by the compressor 10 by heat exchange. The refrigerant outlet of the condenser 12 is connected to the refrigerant inlet of the expansion valve 14 via the refrigerant pipe P3.

  The expansion valve 14 is a device that expands the refrigerant condensed in the condenser 12. The refrigerant outlet of the expansion valve 14 is connected to the refrigerant inlet of the evaporator 16 via a refrigerant pipe P4.

  The evaporator 16 is a heat exchanger that evaporates the refrigerant expanded by the expansion valve 14 by heat exchange. The refrigerant outlet of the evaporator 16 is connected to the inlet of the compressor 10 via a refrigerant pipe P5.

  A second refrigerant pipe P2 is connected to the first refrigerant pipe P1 in the middle thereof. The connecting portion between the first refrigerant pipe P1 and the second refrigerant pipe P2 is a branch portion 40. The second refrigerant pipe P2 branched from the first refrigerant pipe P1 at the branch portion 40 is connected again to the first refrigerant pipe P1 at the joining portion 42 on the downstream side of the branch portion 40. In addition, it is preferable that the pipe diameter of the first refrigerant pipe P1 be equal to or larger than the pipe diameter of the second refrigerant pipe P2.

  An oil separator 18 is provided in the middle of the second refrigerant pipe P2. The second refrigerant pipe P2 is divided into an upstream second refrigerant pipe P2A and a downstream second refrigerant pipe P2B on the upstream side and the downstream side of the oil separator 18. In the following description, when it is necessary to distinguish the second refrigerant pipe P2 between the upstream side and the downstream side of the oil separator 18, the term "upstream second refrigerant pipe P2A" or "downstream second refrigerant pipe P2B" is used. To use. On the other hand, when the distinction is not necessary, the term “second refrigerant pipe P2” is simply used.

  The oil separator 18 is a device that separates the oil contained in the refrigerant discharged from the compressor 10 from the refrigerant. The outlet of the oil separator 18 is connected to the compressor 10 via an oil return pipe P6. An on-off valve 20 is provided in the oil return pipe P6.

  The control unit 30 is a device capable of communicating with the above-described devices and executing control, and includes, for example, a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), and a computer-readable device. It is composed of various storage media. A series of processes for realizing various functions are stored in a storage medium or the like in the form of a program as an example, and the CPU reads the program into a RAM or the like to execute information processing / arithmetic processing. As a result, various functions are realized. The program is installed in a ROM or other storage medium in advance, provided in a state of being stored in a computer-readable storage medium, or delivered via wired or wireless communication means. Etc. may be applied. The computer-readable storage medium is a magnetic disk, a magneto-optical disk, a CD-ROM, a DVD-ROM, a semiconductor memory, or the like.

Next, the flow of the refrigerant in the refrigerant circuit will be described.
The refrigerant compressed by the compressor 10 is guided to the first refrigerant pipe P1. A part of the refrigerant reaching the branch portion 40 flows through the upstream second refrigerant pipe P2A and is guided to the oil separator 18. On the other hand, the remaining refrigerant flows through the first refrigerant pipe P1 as it is and is guided to the condenser 12.

  At this time, as described above, by setting the pipe diameter of the first refrigerant pipe P1 to be equal to or larger than the pipe diameter of the second refrigerant pipe P2, the amount of the refrigerant guided to the condenser 12 is set to the upstream side second refrigerant pipe P2A ( That is, the amount of the refrigerant introduced to the oil separator 18) can be made larger. That is, the main flow of the refrigerant can be on the first refrigerant pipe P1 side instead of the second refrigerant pipe P2 side.

  The refrigerant guided to the condenser 12 is heat-exchanged and condensed by the condenser 12. The refrigerant condensed in the condenser 12 flows through the third refrigerant pipe P3 and is guided to the expansion valve 14.

  The refrigerant guided to the expansion valve 14 expands by the expansion valve 14. The refrigerant expanded by the expansion valve 14 flows through the fourth refrigerant pipe P4 and is guided to the evaporator 16.

  The refrigerant guided to the evaporator 16 is heat-exchanged by the evaporator 16 and evaporated. Here, the heat medium (for example, water) that has exchanged heat with the refrigerant is supplied as chiller water. The refrigerant evaporated in the evaporator 16 flows through the fifth refrigerant pipe P5 and is guided to the compressor 10 again.

  The contained oil is separated from the refrigerant introduced into the oil separator 18 through the upstream second refrigerant pipe P2A. The separated oil collects in the lower part of the oil separator 18. In general, when the load state of the compressor 10 is a load state during normal operation (hereinafter referred to as “normal load state”) or a load state lower than the normal load state, the oil discharged from the compressor 10 (included in the refrigerant) A small amount of oil is discharged. On the other hand, the amount of oil discharged from the compressor 10 is larger in the overload state than in the normal load state. In other words, the oil discharged from the compressor 10 increases as the load on the compressor 10 increases.

  The refrigerant from which the oil is removed flows through the upstream second refrigerant pipe P2A and joins the first refrigerant pipe P1 at the joining portion 42. The combined refrigerant is guided to the condenser 12 together with the refrigerant flowing through the first refrigerant pipe P1 without passing through the oil separator 18.

  On the other hand, the oil stored in the lower part of the oil separator 18 can be returned to the compressor 10 via the oil return pipe P6. The oil may contain a small amount of the refrigerant compressed by the compressor 10 without being separated.

  Next, control of the on-off valve 20 provided in the oil return pipe P6 will be described.

  The opening / closing valve 20 is controlled (for example, opened / closed) by the control unit 30 according to the load state of the compressor 10. The load state of the compressor 10 changes depending on, for example, the water temperature set in the chiller facility, the outside air temperature, and the like.

Next, the control of the on-off valve 20 will be described in detail.
The on-off valve 20 is closed when the load state of the compressor 10 is the normal load state or the load state lower than the normal load state. That is, the oil return pipe P6 is shut off, and the oil is not returned to the compressor 10. On the contrary, when the load condition of the compressor 10 is more overloaded than the normal load condition, the on-off valve 20 is opened. That is, the oil return pipe P6 is not shut off, and the oil can be returned to the compressor 10.

Here, the load state of the compressor 10 is determined as follows.
The control unit 30 can acquire the rotation speed of the compressor 10. For example, the rotation speed of the compressor 10 is acquired from an inverter (not shown) that changes the rotation speed of the electric motor that drives the compressor 10. . At this time, when the rotation speed of the compressor 10 is equal to or lower than the predetermined rotation speed, the control unit 30 determines that the compressor 10 is in the normal load state or the low load state. Further, when the rotation speed of the compressor 10 exceeds the predetermined rotation speed, the control unit 30 determines that the compressor 10 is in the overload state. The predetermined rotation speed is, for example, a rotation speed at which the amount of oil contained in the refrigerant discharged from the compressor 10 is about 5% of the total amount (refrigerant and oil), a rotation speed of about 50% of the upper limit rotation speed, or the like. is there. However, these rotational speeds differ depending on the specifications of the compressor 10.

Moreover, the load state of the compressor 10 may be determined as follows.
The control unit 30 is capable of acquiring the pressure on the discharge side and the pressure on the suction port side of the compressor 10. For example, the pressure on the discharge side and the pressure on the suction port side are pressure gauges (not shown) provided in the refrigerant pipe. No.). At this time, when the pressure difference between the discharge port side and the suction port side is equal to or lower than the predetermined pressure, the control unit 30 determines that the compressor 10 is in the normal load state or the low load state. Further, when the differential pressure exceeds the predetermined pressure, the control unit 30 determines that the compressor 10 is in the overload state. The predetermined pressure is, for example, a pressure based on a design pressure ratio of the compressor 10 or a pressure based on a differential pressure (2.0 MPa to 2.2 MPa) under a heating rated condition for the R410 refrigerant (as an example). However, these pressures differ depending on the specifications of the compressor 10.

  The criterion for determining the load state of the compressor 10 is not limited to the above-described criterion, and may be determined based on the water temperature of the heat exchanger or the outside air temperature.

The following effects are achieved in this embodiment.
The oil separated by the oil separator 18 may slightly contain the refrigerant compressed by the compressor 10. That is, if the oil is returned to the compressor 10 as it is, the compressed refrigerant is inevitably returned from the oil separator 18 to the compressor 10 via the oil return pipe P6. The refrigerant that is unavoidably returned does not exchange heat in the condenser 12, and thus becomes a loss for the work of the compressor 10. However, when the oil return pipe P6 is shut off by the opening / closing valve 20, a phenomenon in which some of the refrigerant returns from the oil separator 18 to the compressor 10 is suppressed, so that the loss of the work of the compressor 10 can be suppressed.

  Further, in a normal load state or a low load state, since the amount of oil discharged from the compressor 10 (oil contained in the refrigerant and discharged) is small, the on-off valve 20 shuts off the oil return pipe P6 to compress the oil. Even if the compressor 10 is not returned, the influence on the compressor 10 (for example, oil shortage) can be ignored. On the other hand, in the overloaded state, a large amount of oil is discharged from the compressor 10. Therefore, if the on-off valve 20 shuts off the oil return pipe P6, the compressor 10 may run out of oil. However, the oil accumulated in the oil separator 18 can be returned to the compressor 10 by opening the on-off valve 20 provided in the oil return pipe P6 when the load is overloaded rather than the normal load. Therefore, the amount of oil in the compressor 10 can be secured. Therefore, it is not necessary to increase the amount of oil to be filled in the compressor 10 in order to compensate for the lack of oil in the compressor 10 that occurs in the overloaded state.

  Further, if the entire amount of the refrigerant passes through the oil separator 18, the oil will be accumulated in the oil separator 18 in a short time. Therefore, it is necessary to frequently return the oil from the oil separator 18 to the compressor 10 in order to reduce the oil. On the other hand, most of the refrigerant is introduced from the compressor 10 to the condenser 12 through the first refrigerant pipe P1, and the amount of the refrigerant introduced to the oil separator 18 is smaller than that of the oil separator 18. The time required for oil to collect can be lengthened. That is, in order to reduce the oil accumulated in the oil separator 18, the frequency of returning the oil from the oil separator 18 to the compressor 10 can be reduced. As a result, the frequency of the phenomenon in which the compressed refrigerant returns from the oil separator 18 to the compressor 10 can be reduced, so that the loss of the work of the compressor 10 can be suppressed.

[Second Embodiment]
Next, a refrigerator according to the second embodiment of the present invention will be described. The present embodiment is different from the first embodiment in the form near the branch portion 40, and is the same in other respects. Therefore, only the points different from the first embodiment will be described, and other elements will be denoted by the same reference numerals and the description thereof will be omitted.

FIG. 2 shows a refrigerant circuit of a refrigerator according to the second embodiment of the present invention.
Unlike the first embodiment, a three-way valve 22 is provided as a switching unit capable of switching the flow direction at the branch section 40.

  The three-way valve 22 can switch the flow direction so that the refrigerant introduced from the compressor 10 is introduced to either one of the first refrigerant pipe P1 and the upstream second refrigerant pipe P2A. In other words, the refrigerant introduced from the compressor 10 can be switched to bypass or pass through the oil separator 18 (second refrigerant pipe P2).

  When the switching means is provided, the pipe diameter of the first refrigerant pipe P1 does not need to be equal to or larger than the pipe diameter of the second refrigerant pipe P2.

The three-way valve 22 is controlled as follows.
The control unit 30 can acquire the open / closed state of the open / close valve 20. When the on-off valve 20 is in the closed state (that is, when the compressor 10 is in the normal load state or the low load state), the control unit 30 controls the three-way valve 22 so that the refrigerant is not guided to the oil separator 18. On the contrary, when the open / close valve 20 is in the open state (that is, when the compressor 10 is in the overload state), the control unit 30 controls the three-way valve 22 so as to guide the refrigerant to the oil separator 18.

  The switching means capable of switching the flow direction in the branch portion 40 is not limited to the three-way valve 22 described above, and may be two open / close valves 24 and 26 as shown in FIG. 3, for example. . In this case, the one on-off valve 24 is provided in the first refrigerant pipe P1 between the branch portion 40 and the merging portion 42, and the many on-off valves 26 are provided in the upstream second refrigerant pipe P2A.

The following effects are achieved in this embodiment.
When the on-off valve 20 is closed (that is, when the compressor 10 is under a normal load condition and oil is not returned from the oil separator 18 to the compressor 10), the entire amount of the refrigerant bypasses the oil separator 18. For this reason, since the oil does not collect in the oil separator 18, there is no need to periodically return the oil from the oil separator 18 to the compressor 10, and the frequency of the phenomenon that the refrigerant returns from the oil separator 18 to the compressor 10 is further reduced. it can.

  On the other hand, when the on-off valve 20 is in the open state (that is, when the compressor 10 is in the overloaded state and the oil is returned from the oil separator 18 to the compressor 10), the entire amount of the refrigerant is guided to the oil separator 18. As a result, the oil can be accumulated in the oil separator 18 in a short time. Therefore, the required amount of oil can be secured in the compressor 10 in a short time. Further, even in an overloaded state in which a large amount of oil is discharged from the compressor 10, the oil contained in the refrigerant can be separated by the oil separator 18, so that the efficiency of heat exchange in the condenser 12 installed downstream is high. The decrease can be suppressed.

  In addition, in the first embodiment and the second embodiment, as shown in FIG. 3, a bypass pipe P7 that connects the upstream side and the downstream side of the on-off valve 20 may be provided. The bypass pipe P7 has a pipe diameter such that only oil flows, and a capillary tube or the like is used, for example. In this case, only oil can be returned from the oil separator 18 to the compressor 10. Therefore, the frequency of returning the oil from the oil separator 18 to the compressor 10 regularly can be reduced.

10 compressor 12 condenser 14 expansion valve 16 evaporator 18 oil separator 20 on-off valve 22 three-way valve (switching means)
24,26 Open / close valve (switching means)
30 control part 40 branching part 42 merging part P1 first refrigerant pipe P2A (P2) upstream second refrigerant pipe (second refrigerant pipe)
P2B (P2) Downstream second refrigerant pipe (second refrigerant pipe)
P3, P4, P5 Refrigerant piping P6 Oil return piping P7 Bypass piping

Claims (8)

A compressor for compressing the refrigerant,
A condenser for condensing the refrigerant compressed by the compressor,
A first refrigerant pipe connecting the compressor and the condenser;
A second refrigerant pipe branched from the first refrigerant pipe at a branch portion and joined again to the first refrigerant pipe downstream of the branch portion;
An oil separator provided in the second refrigerant pipe and for separating oil in the refrigerant;
An oil return pipe for returning the oil separated by the oil separator to the compressor,
An on-off valve provided in the oil return pipe,
A control unit that switches between opening and closing of the open / close valve according to a load state of the compressor;
Refrigerator equipped with.   The control unit closes the on-off valve when the compressor is in a load state during normal operation or a load state lower than that, and the compressor is in an overload state rather than a load state during normal operation. The refrigerator according to claim 1, wherein the on-off valve is opened at times.   The refrigerator according to claim 1 or 2, wherein the first refrigerant pipe has a pipe diameter equal to or larger than that of the second refrigerant pipe. A switching means capable of switching the flow direction at the branch portion of the first refrigerant pipe,
The control unit controls the switching means so that the refrigerant is not guided to the second refrigerant pipe side when the opening / closing valve is closed, and the refrigerant is directed to the second refrigerant pipe side when the opening / closing valve is open. The refrigerator according to any one of claims 1 to 3, wherein the switching means is controlled so as to be guided.   The refrigerator according to claim 1, wherein the oil return pipe includes a bypass pipe that connects an upstream side and a downstream side of the on-off valve.   The control unit determines that the compressor is in a load state during normal operation or a load state lower than that when the rotation speed of the compressor is equal to or lower than a predetermined rotation speed, and when the rotation speed of the compressor exceeds the predetermined rotation speed, The refrigerator according to claim 1, wherein it is determined that the compressor is in an overloaded state rather than a loaded state during normal operation.   When the pressure difference between the suction side and the discharge side of the compressor is less than or equal to a predetermined pressure, the control unit determines that the compressor is in a load state during normal operation or a load state lower than that, and the predetermined pressure is The refrigerator according to claim 1, wherein when it exceeds, it is determined that the compressor is in an overload state rather than a load state during normal operation.   Chiller equipment provided with the refrigerator according to any one of claims 1 to 7.

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