JP2012154509A - Air conditioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent air conditioning performance from being degraded without causing a closing period where refrigeration oil is not returned to a compressor.SOLUTION: An oil return passage 10a provides connection between an oil separator 2 and an intake side of a compressor 1, thus defining a bypass passage. An oil return passage 10b provides connection between the oil separator 2 and a refrigerant inflow side of an accumulator 7, thus defining a bypass passage.

Description

  The present invention relates to an air conditioner having an oil return path, and more particularly to opening / closing control of the oil return path.

  As a conventional method for controlling the oil return path for returning the refrigeration oil in the refrigerant to the compressor, there has been disclosed one that includes a plurality of compressors and switches the position for returning the refrigeration oil separated by the oil separator (for example, Patent Document 1).

JP 2010-156512 A (page 13, FIG. 1)

  In the conventional method, a mechanism for switching between a plurality of oil return paths is provided, but any oil return path is a path that is directly injected into the compressor, and is compressed in the state of heated high-temperature refrigerant and refrigeration oil. Will be injected into the machine. For this reason, there is a problem that the density of the suction refrigerant is lowered, the flow rate of the discharged refrigerant is lowered, and the air conditioning capacity is lowered.

  As another method, it is conceivable to have one oil return path and an opening / closing mechanism on the path, but in that case, the oil return path itself is closed by the opening / closing mechanism. The oil will not return to the compressor during the closing period.

  The present invention has been made to solve the above-described problem, and an object of the present invention is to obtain an air conditioner that does not generate a closing period in which refrigeration oil does not return to the compressor and suppresses a decrease in air conditioning capability. And

  The air conditioner according to the present invention includes a compressor, a four-way valve, a heat source side heat exchanger, a throttling device, a use side heat exchanger, and a refrigeration cycle configured by connecting accumulators with a refrigerant pipe, and the compression An oil separator that is installed between the compressor and the four-way valve and separates refrigeration oil from the refrigerant discharged from the compressor, and connects the oil separator and the inlet side of the compressor, A first oil return path on which a first on-off valve and a first throttle mechanism are installed is connected to the inflow side of the oil separator and the accumulator, and a second on-off valve and a second throttle are connected to the path. A second oil return path in which a mechanism is installed; and a control device that controls the opening and closing of the first on-off valve and the second on-off valve. The first oil return path includes the first on-off valve When in the open state, it is separated from the refrigerant by the oil separator. Refrigeration oil is sucked into the suction port of the compressor, and when the second on-off valve is in the open state, the second oil return path allows the refrigerating machine oil separated from the refrigerant by the oil separator to be stored in the accumulator. The control device causes the first opening and closing of the first opening and closing so that an oil concentration, which is a concentration of refrigeration oil contained in the refrigerant sucked into the compressor, is equal to or higher than an allowable oil concentration of the compressor. By controlling the opening and closing of the valve and the second on-off valve, a path through which the compressor oil separated by the oil separator is sucked into the compressor is selected from the first oil return path and the second oil return path. It is something to switch to.

  According to the present invention, the compression is performed by switching the path for returning the refrigeration oil directly to the compressor and the path for returning to the compressor via the accumulator so that the oil concentration is not less than the permissible oil concentration without causing the compressor to fail. Machine failure can be prevented, and a decrease in air conditioning capability can be suppressed.

It is a block diagram of the refrigerant circuit of the air conditioner which concerns on Embodiment 1 of this invention. It is an internal block diagram of the accumulator 7 of the air conditioner concerning Embodiment 1 of this invention. It is a figure which shows the relationship between the oil concentration in each oil return path | route of the air conditioner which concerns on Embodiment 1 of this invention, and a liquid level height. It is a figure which shows the relationship between the suction temperature of the compressor 1 in each oil return path | route of the air conditioner which concerns on Embodiment 1 of this invention, and a liquid level height. It is a control block diagram in switching operation | movement of the oil return path | route 10a and the oil return path | route 10b of the air conditioner which concerns on Embodiment 1 of this invention. It is a figure which shows the control flow of switching operation | movement of the oil return path | route 10a of the air conditioner which concerns on Embodiment 1 of this invention, and the oil return path | route 10b. It is a block diagram of the refrigerant circuit of the air conditioner which concerns on Embodiment 2 of this invention. It is a figure which shows an example of a structure of the database 30 which the control apparatus 20 of the air conditioner concerning Embodiment 2 of this invention has memorize | stored. It is a figure which shows the relationship between the refrigerant | coolant flow rate of the compressor 1 of the air conditioner which concerns on Embodiment 2 of this invention, and the oil concentration in each oil return path | route. It is a control block diagram in switching operation | movement of the oil return path | route 10a and the oil return path | route 10b of the air conditioner which concerns on Embodiment 2 of this invention. It is a figure which shows the control flow of switching operation | movement of the oil return path | route 10a of the air conditioner which concerns on Embodiment 2 of this invention, and the oil return path | route 10b. It is a figure which shows an example of a structure of the database 31 with which the temperature and density of the refrigerant | coolant which flow into a throttle mechanism were linked | related. It is a figure which shows the relationship between the control pulse output to a throttle mechanism, and a flow coefficient.

Embodiment 1 FIG.
(Configuration of air conditioner)
FIG. 1 is a configuration diagram of a refrigerant circuit of an air conditioner according to Embodiment 1 of the present invention.
As shown in FIG. 1, the air conditioner according to the present embodiment includes a compressor 1, an oil separator 2, a four-way valve 3, a heat source side heat exchanger 4, expansion devices 5 a to 5 c, and use side heat exchangers. 6a to 6c, an accumulator 7, oil return paths 10a and 10b, and a control device 20. The refrigeration cycle of the air conditioner according to the present embodiment includes a compressor 1, an oil separator 2, a four-way valve 3, a heat source side heat exchanger 4, expansion devices 5a to 5c, utilization side heat exchangers 6a to 6c, and four sides. The valve 3, the accumulator 7, and the compressor 1 are again connected in this order by refrigerant piping.

  Moreover, as shown in FIG. 1, the expansion device 5a and the use side heat exchanger 6a, the expansion device 5b and the use side heat exchanger 6b, and the expansion device 5c and the use side heat exchanger 6c connected in series are Connected in parallel. The oil separator 2 and the suction port side of the compressor 1 are connected by an oil return path 10a to form a bypass path. Further, the oil separator 2 and the refrigerant inflow side of the accumulator 7 are connected by an oil return path 10b to form a bypass path. Further, the accumulator 7 is provided with a liquid level detecting unit 7e for detecting the liquid level of the liquid refrigerant stored therein, and the liquid level detecting unit 7e is electrically connected to the control device 20. It is connected.

  The compressor 1 compresses the sucked gas refrigerant, discharges it as a high-temperature and high-pressure gas refrigerant, and circulates the refrigerant in the refrigeration cycle.

  The oil separator 2 separates the refrigerating machine oil discharged simultaneously with the gas refrigerant discharged from the compressor 1 into a refrigerant and refrigerating machine oil. However, although most of the refrigeration oil is separated from the refrigerant by the oil separator 2, a part of the refrigeration oil is not completely separated, and the refrigeration oil that has not been separated is transferred to the four-way valve 3 together with the refrigerant. Head and circulate through the refrigeration cycle.

  The four-way valve 3 switches the refrigerant flow path in the refrigeration cycle. The switching of the flow path of the four-way valve 3 is performed based on the drive signal output from the control device 20, and the flow path for sending the refrigerant flowing out from the oil separator 2 to the heat source side heat exchanger 4 or the oil separator 2 is switched to a flow path for sending the refrigerant flowing out of the refrigerant to the use side heat exchangers 6a to 6c.

  The heat source side heat exchanger 4 is installed in the outdoor unit of the air conditioner according to the present embodiment, and performs heat exchange between the refrigerant flowing in and the outside air. The heat source side heat exchanger 4 is provided with an outdoor blower (not shown), and outside air is sent to the heat source side heat exchanger 4 by the outdoor blower. The heat source side heat exchanger 4 may be configured to exchange heat with water, such as a plate type or a double tube type.

  The expansion devices 5a to 5c are installed in the indoor unit of the air conditioner according to the present embodiment, and expand and depressurize the inflowing refrigerant.

  The use side heat exchangers 6a to 6c are installed in the indoor unit of the air conditioner according to the present embodiment, and between the refrigerant flowing in and the indoor air of the room in which the indoor unit is installed. Heat exchange is performed. Each of the use side heat exchangers 6a to 6c is provided with an indoor fan (not shown), and indoor air is sent to each of the use side heat exchangers 6a to 6c by the indoor fan.

Further, the expansion device 5a and the use side heat exchanger 6a, the expansion device 5b and the use side heat exchanger 6b, and the expansion device 5c and the use side heat exchanger 6c connected in series are respectively separate indoor units (that is, In FIG. 1, it is provided in three indoor units). These indoor units may be provided in the same room, or may be provided in a separate room.
In addition, as shown in FIG. 1, each of the expansion devices 5 a to 5 c and the use side heat exchangers 6 a to 6 c is provided with three units, that is, three indoor units are provided. It is not limited, and other numbers may be installed.

  The accumulator 7 is disposed on the refrigerant suction side of the compressor 1, stores the gas refrigerant, liquid refrigerant, and refrigeration oil to the compressor 1, and stores excess liquid refrigerant. It has a function not to send to the compressor 1 excessively. Further, the accumulator 7 is provided with the liquid level detection unit 7e for detecting the liquid level of the stored liquid refrigerant as described above. The other structure about the accumulator 7 is later mentioned in FIG.

The oil return path 10a includes an on-off valve 9a and a throttle mechanism 8a from the oil separator 2 side, and returns the refrigerating machine oil separated from the refrigerant by the oil separator 2 directly to the suction port of the compressor 1. It is. At this time, the refrigerant and the refrigerating machine oil are not completely separated by the oil separator 2, and the refrigerating machine oil returned to the compressor 1 through the oil return path 10a contains a certain amount of refrigerant. When returning the refrigeration oil to the compressor 1 via the oil return path 10a, the throttle mechanism 8a serves to adjust the flow rate so that the high-temperature and high-pressure refrigerant contained in the refrigeration oil does not return to the compressor 1 excessively. It is what you have. Accordingly, it is possible to suppress a decrease in the density of the suction refrigerant and a decrease in the discharge refrigerant flow rate due to the return of the high-temperature and high-pressure refrigerant to the compressor 1, and it is possible to suppress a decrease in the air conditioning capability. The on-off valve 9a is electrically connected to the control device 20 (not shown) and is controlled to open and close by a drive signal output from the control device 20, and is separated by the oil separator 2 only in the open state. Circulate refrigeration oil. Details of the opening / closing control will be described later.
The throttle mechanism 8a, the on-off valve 9a, and the oil return path 10a correspond to the “first expansion mechanism”, “first on-off valve”, and “first oil return path” of the present invention, respectively.

The oil return path 10b includes an opening / closing valve 9b and a throttle mechanism 8b from the oil separator 2 side, and is a path for sending the refrigeration oil separated from the refrigerant by the oil separator 2 to the inflow side of the accumulator 7. is there. At this time, as described above, the refrigerant and the refrigerating machine oil are not completely separated by the oil separator 2, and a certain amount of refrigerant is contained in the refrigerating machine oil sent to the accumulator 7 through the oil return path 10b. include. When the refrigerating machine oil is returned to the compressor 1 via the oil return path 10b and the accumulator 7, the throttle mechanism 8b adjusts the flow rate so that the high-temperature and high-pressure refrigerant contained in the refrigerating machine oil is not returned to the compressor 1 excessively. Have a role to play. Accordingly, it is possible to suppress a decrease in the density of the suction refrigerant and a decrease in the discharge refrigerant flow rate due to the return of the high-temperature and high-pressure refrigerant to the compressor 1, and it is possible to suppress a decrease in the air conditioning capability. The on-off valve 9b is electrically connected to the control device 20 (not shown), controlled to open / close by a drive signal output from the control device 20, and separated by the oil separator 2 only in the open state. Circulate refrigeration oil. This open / close control will be described later in the same manner as the open / close valve 9a described above.
The throttle mechanism 8b, the on-off valve 9b, and the oil return path 10b correspond to the “second expansion mechanism”, “second on-off valve”, and “second oil return path” of the present invention, respectively.

  The control device 20 performs the rotational speed control of the compressor 1, the flow path switching control of the four-way valve 3, the opening control of the expansion devices 5a to 5c, the open / close control of the open / close valves 9a and 9b, and the like.

  As shown in FIG. 1, the oil return path 10a and the oil return path 10b are arranged in the order of the on-off valve and the throttle mechanism from the oil separator 2 side, but are not limited to this. The order may be reversed.

(Structure of accumulator 7)
FIG. 2 is an internal configuration diagram of the accumulator 7 of the air conditioner according to Embodiment 1 of the present invention.
As shown in FIG. 2, the accumulator 7 includes an inflow pipe 7a, an outflow pipe 7b, a float 7d, and a liquid level detection unit 7e.

  The inflow pipe 7 a is connected to the four-way valve 3 and is a pipe through which the refrigerant that has passed through the four-way valve 3 flows into the accumulator 7. Of the refrigerant flowing in from the inflow pipe 7a, the refrigeration oil and the liquid refrigerant contained in the refrigerant fall and accumulate in the lower part, and the gas refrigerant flows out of the accumulator 7 through the outflow pipe 7b and is sucked into the compressor 1. Further, as shown in FIG. 2, an orifice 7c is provided at the lowermost portion of the outflow pipe 7b on the U-shape. A part of the refrigerating machine oil and the liquid refrigerant accumulated in the lower part of the accumulator 7 flows into the outflow pipe 7b from the orifice 7c, flows out of the accumulator 7, and is sucked into the compressor 1. By this orifice 7 c, the refrigerating machine oil and the liquid refrigerant accumulated in the lower part of the accumulator 7 flow into the outflow pipe 7 b by a predetermined amount and are sent to the compressor 1. Thus, by sending a predetermined amount of liquid refrigerant and refrigerating machine oil from the orifice 7c to the compressor 1, there is an effect of suppressing the compressor 1 from being overheated.

  A float 7d floats on the liquid level of the refrigerating machine oil and the liquid refrigerant accumulated in the lower part of the accumulator 7, and moves up and down according to the liquid level. A liquid level detection unit 7e is installed above the float 7d. When the liquid level reaches a predetermined height, the float 7d comes into contact with the liquid level detection unit 7e and reaches a predetermined height. A signal indicating that the error has occurred is transmitted from the liquid level detector 7e to the control device 20. The predetermined height may be set in the range of 14300 / A to 22900 / A [mm], where A is the horizontal sectional area of the accumulator 7, for example.

(Cooling operation)
Next, the cooling operation of the air conditioner according to the present embodiment will be described with reference to FIG.
When the cooling operation is performed, the control device 20 switches the flow path of the four-way valve 3 in advance so that the refrigerant flowing out from the oil separator 2 flows to the heat source side heat exchanger 4. After the high-temperature and high-pressure gas refrigerant compressed by the compressor 1 is discharged, most of the refrigerating machine oil contained in the refrigerant is separated in the oil separator 2. The refrigerant separated by the oil separator 2 flows into the heat source side heat exchanger 4 through the four-way valve 3. The refrigerant that has flowed into the heat source side heat exchanger 4 undergoes heat exchange with the outside air sent by the outdoor blower, condenses, and flows out of the heat source side heat exchanger 4 as a high-pressure liquid refrigerant. The liquid refrigerant flowing out from the heat source side heat exchanger 4 branches and flows into the expansion devices 5a to 5c, respectively. The liquid refrigerant that has flowed into the expansion devices 5a to 5c is expanded and depressurized to become a low-pressure refrigerant, and flows into the use side heat exchangers 6a to 6c, respectively. The refrigerant that has flowed into the use side heat exchangers 6a to 6c undergoes heat exchange with the indoor air sent by the indoor blower, evaporates, or becomes a refrigerant having a high dryness and becomes a use side heat exchanger. It flows out from 6a-6c. At this time, indoor air that has been subjected to heat exchange and is cooled is blown out from the indoor units each including the use side heat exchangers 6a to 6c, and the room is cooled. The refrigerant that has flowed out of the use side heat exchangers 6 a to 6 c merges and flows into the accumulator 7 via the four-way valve 3. The refrigerant flowing into the accumulator 7 is separated into a gas refrigerant and a liquid refrigerant, and the liquid refrigerant is stored in the lower part of the accumulator 7, and the gas refrigerant is sent to the compressor 1 and compressed again. The above operation is repeated.

(Heating operation)
Next, the heating operation of the air conditioner according to the present embodiment will be described with reference to FIG.
When the heating operation is performed, the control device 20 switches the flow path of the four-way valve 3 in advance so that the refrigerant flowing out from the oil separator 2 flows to the use side heat exchangers 6a to 6c. After the high-temperature and high-pressure gas refrigerant compressed by the compressor 1 is discharged, most of the refrigerating machine oil contained in the refrigerant is separated in the oil separator 2. The refrigerant separated by the oil separator 2 passes through the four-way valve 3 and then branches to flow into the use side heat exchangers 6a to 6c. The refrigerant that has flowed into the usage-side heat exchangers 6a to 6c undergoes heat exchange with the indoor air sent by the indoor blower, condenses, and becomes high-pressure liquid refrigerant, thus the usage-side heat exchangers 6a to 6c. Spill from. At this time, heat is exchanged from the indoor units provided with the use side heat exchangers 6a to 6c, and heated indoor air is blown out to heat the room. The liquid refrigerant that has flowed out of the use side heat exchangers 6a to 6c flows into the expansion devices 5a to 5c, expands and depressurizes, becomes a low pressure refrigerant, and flows out of the use side heat exchangers 6a to 6c. . The refrigerant that has flowed out of the use side heat exchangers 6 a to 6 c merges and flows into the heat source side heat exchanger 4. The refrigerant that has flowed into the heat source side heat exchanger 4 evaporates through heat exchange with the outside air sent by the outdoor blower, or flows out of the heat source side heat exchanger 4 as a refrigerant having a high degree of dryness. The refrigerant flowing out from the heat source side heat exchanger 4 flows into the accumulator 7 via the four-way valve 3. The refrigerant flowing into the accumulator 7 is separated into a gas refrigerant and a liquid refrigerant, and the liquid refrigerant is stored in the lower part of the accumulator 7, and the gas refrigerant is sent to the compressor 1 and compressed again. The above operation is repeated.

(Refrigerating machine oil behavior)
FIG. 3 is a diagram showing the relationship between the oil concentration and the liquid level in each oil return path of the air conditioner according to Embodiment 1 of the present invention, and FIG. 4 shows each oil return of the air conditioner. It is a figure which shows the relationship between the suction temperature of the compressor 1 in a path | route, and a liquid level height.

First, the behavior of refrigerating machine oil contained in the refrigerant sent from the compressor 1 to the oil separator 2 will be described with reference to FIG.
Most of the refrigerating machine oil discharged together with the refrigerant from the compressor 1 is separated from the refrigerant by the oil separator 2 as described above. When the on-off valve 9a is open and the on-off valve 9b is closed, the refrigerating machine oil separated by the oil separator 2 passes through the on-off valve 9a and the throttle mechanism 8a (that is, the oil return path). 10a) and returned to the compressor 1. At this time, as described above, the throttle mechanism 8a has a role of expanding and depressurizing a high-temperature and high-pressure refrigerant partially contained in the separated refrigerating machine oil to return it to the compressor 1 as a low-temperature and low-pressure refrigerant.

  In addition, when the on-off valve 9a is closed and the on-off valve 9b is in the open state, the refrigerating machine oil separated by the oil separator 2 passes through the on-off valve 9b and the throttle mechanism 8b (that is, the oil After being sent to the accumulator 7 (via the return path 10b), it is returned to the compressor 1. At this time, the diaphragm mechanism 8b has the same role as the diaphragm mechanism 8a.

  The refrigerating machine oil that has not been separated toward the oil return path 10a or the oil return path 10b by the oil separator 2 circulates in the refrigeration cycle together with the refrigerant, as shown in the cooling operation and heating operation described above. It will be.

Next, referring to FIG. 3, the oil concentration in the refrigerant that flows out from the outflow pipe 7 b of the accumulator 7 and is sucked into the compressor 1, and the refrigerating machine oil and liquid refrigerant liquid stored in the accumulator 7. The relationship with the surface height will be described.
FIG. 3 shows the case where the refrigeration oil separated by the oil separator 2 is returned to the compressor 1 via the oil return path 10a and returned to the compressor 1 via the oil return path 10b. The relationship between the concentration and the liquid level in the accumulator 7 is shown. As shown in FIG. 3, in any case, the higher the liquid level, the lower the oil concentration. When the liquid level is the same, the oil concentration when the refrigeration oil is returned to the compressor 1 by the oil return path 10b is lower than the oil concentration when the oil level is returned to the compressor 1 by the oil return path 10a. Here, the oil concentration of the refrigerating machine oil sucked into the compressor 1 has an allowable lower limit value (hereinafter referred to as “allowable oil concentration”). When the oil concentration falls below this lower limit value, the compressor 1 breaks down. there is a possibility. Therefore, it is necessary to monitor the liquid level so that the oil level in the oil return path 10a and the oil return path 10b is equal to or lower than the liquid level corresponding to the allowable oil concentration. However, as shown in FIG. 3, the accumulator 7 has a maximum liquid level height, that is, the maximum amount of refrigerating machine oil and liquid refrigerant that can be stored inside the accumulator 7, and is usually determined by the oil return path 10a. When refrigerating machine oil is returned, the maximum liquid level is designed so that the oil concentration is equal to or higher than the allowable oil concentration. Therefore, when refrigerating machine oil is returned through the route of the oil return route 10a, the compressor 1 does not normally fail even if the liquid level is not monitored. In the case where the refrigeration oil is returned to the compressor 1 by the oil return path 10b, the liquid level height corresponding to the above-described allowable oil concentration is hereinafter referred to as “allowable liquid level height”.

Next, the relationship between the suction temperature of the refrigerant sucked into the compressor 1 and the liquid level height of the refrigerating machine oil and the liquid refrigerant stored in the accumulator 7 will be described with reference to FIG.
FIG. 4 shows the compression when the refrigeration oil separated by the oil separator 2 is returned to the compressor 1 via the oil return path 10a and when returned to the compressor 1 via the oil return path 10b. The relationship between the suction temperature of the machine 1 and the liquid level in the accumulator 7 is shown. As shown in FIG. 4, in any case, the higher the liquid level, the lower the suction temperature. When the liquid level is the same, the suction temperature when the refrigeration oil is returned to the compressor 1 by the oil return path 10b is lower than the suction temperature when the oil level is returned to the compressor 1 by the oil return path 10a. Here, since the density of the refrigerant | coolant suck | inhaled by the compressor 1 becomes so large that the suction | inhalation temperature is low, the refrigerant | coolant amount discharged from the compressor 1 increases and air-conditioning capability improves. Therefore, the air-conditioning capacity is improved in the case where the refrigeration oil is returned to the compressor 1 by the oil return path 10b than in the case where the refrigeration oil is returned to the compressor 1 by the oil return path 10a. However, when refrigerating machine oil is returned through the oil return path 10b, as described with reference to FIG. 3, there is an allowable liquid level height for preventing the compressor 1 from malfunctioning. The refrigerating machine oil cannot be returned by the return path 10b. Therefore, in the present embodiment, when the float 7d in the accumulator 7 reaches the allowable liquid level, the mounting position of the liquid level detection unit 7e is set so as to contact the liquid level detection unit 7e. Hereinafter, switching control between the oil return path 10a and the oil return path 10b as illustrated in FIGS. 5 and 6 is performed.

(Oil return path switching operation)
FIG. 5 is a control block diagram in the switching operation of the oil return path 10a and the oil return path 10b of the air conditioner according to Embodiment 1 of the present invention, and FIG. 6 is a diagram showing a control flow of the switching operation. is there.
As shown in FIG. 5, the liquid level detection unit 7 e installed in the accumulator 7, the on-off valve 9 a in the oil return path 10 a, and the on-off valve 9 b in the oil return path 10 b are electrically connected to the control device 20. It is connected. When the float 7d in the accumulator 7 comes into contact with the liquid level detector 7e, it is assumed that the liquid level has reached a predetermined height (in the present embodiment, the allowable liquid level). The unit 7e transmits a detection signal to the control device 20. Based on this detection signal, the control device 20 outputs a drive signal to the on-off valve 9a or the on-off valve 9b, and performs on-off control of the on-off valve 9a and on-off valve 9b.

  Hereinafter, the switching operation of the oil return path 10a and the oil return path 10b by the opening / closing control of the on / off valves 9a and 9b will be described with reference to FIG.

(S1)
The liquid level detection unit 7e of the accumulator 7 has a liquid level height that is always a predetermined height during operation of the air conditioner according to the present embodiment (in the present embodiment, an allowable liquid level height). Continue to detect whether or not.

(S2)
The control device 20 determines whether or not the float 7d has reached a predetermined height and has contacted the liquid level detection unit 7e to receive a detection signal. As a result of the determination, when the control device 20 receives a detection signal, the process proceeds to step S3. On the other hand, when the control device 20 does not receive the detection signal, the process proceeds to step S4.

(S3)
The control device 20 determines that the liquid level of the accumulator 7 has become higher than a predetermined height, and based on the drive signal, opens the on-off valve 9a and closes the on-off valve 9b, and the oil separator 2 Control is performed so that the separated refrigerating machine oil is returned to the compressor 1 by the oil return path 10a.

(S4)
The control device 20 determines that the liquid level of the accumulator 7 is equal to or less than a predetermined height, and closes the on-off valve 9a and opens the on-off valve 9b according to the drive signal, and the oil separator 2 The refrigerating machine oil separated by the above is controlled so as to be returned to the compressor 1 by the oil return path 10b.

  Thereafter, the operations in steps S1 to S4 are repeated.

(Effect of Embodiment 1)
As in the above configuration and operation, when the compressor 1 is below the allowable liquid level that does not cause failure, the refrigeration oil separated from the oil separator 2 by the oil return path 10b is returned to the compressor 1. As a result, the suction temperature can be lowered as compared with the case where the refrigeration oil is returned to the compressor 1 by the oil return path 10a, so that the air conditioning capability can be improved.

  Further, when the liquid level of the accumulator 7 exceeds the allowable liquid level, the path for returning the refrigeration oil to the compressor 1 is switched to the oil return path 10a, so that the compressor 1 is prevented from being broken. Can improve safety.

  In the above description, the liquid level detection unit 7e of the accumulator 7 is attached at a position where it contacts the liquid level detection unit 7e when the float 7d reaches the allowable liquid level. It is not limited. That is, the liquid level detection unit 7e of the accumulator 7 may be attached at a position where the liquid level detection unit 7e contacts the liquid level detection unit 7e when the float 7d is lower than the allowable liquid level by a predetermined amount. . As a result, the refrigeration oil having an allowable oil concentration or higher can be reliably returned to the compressor 1, so that the compressor 1 can be prevented from being broken and further improved in safety.

Embodiment 2. FIG.
The air conditioner according to the present embodiment will be described focusing on differences from the configuration and operation of the air conditioner according to Embodiment 1.
(Configuration of air conditioner)
FIG. 7 is a configuration diagram of the refrigerant circuit of the air conditioner according to Embodiment 2 of the present invention, and FIG. 8 shows an example of the configuration of the database 30 stored in the control device 20 of the air conditioner. FIG.
As shown in FIG. 7, the air conditioner according to the present embodiment includes detection means 1 a that detects the rotation speed, discharge temperature, discharge pressure, and suction pressure of the compressor 1. The detection unit 1 a transmits information on the detected rotation speed, discharge temperature, discharge pressure, and suction pressure of the compressor 1 to the control device 20. The accumulator 7 according to the present embodiment may not include the float 7d and the liquid level detection unit 7e according to the first embodiment. Other configurations are the same as those of the air conditioner according to Embodiment 1 shown in FIG.

  The control device 20 includes, for example, a storage device (not shown), and the storage device stores a database 30 shown in FIG. This database 30 associates the rotation speed, discharge temperature, discharge pressure, and suction pressure of the compressor 1 with the refrigerant flow rate in the compressor 1. The control device 20 can derive the refrigerant flow rate in the compressor 1 by referring to the database 30 from the rotation speed, discharge temperature, discharge pressure, and suction pressure of the compressor 1.

As shown in FIG. 7, the detection means 1a detects all of the rotation speed, discharge temperature, discharge pressure, and suction pressure of the compressor 1, but is not limited to this. A detection means may be provided.
Further, the storage device described above is not necessarily provided in the control device 20, and may be any device that is installed outside the control device 20 and can be accessed from the control device 20.

(Refrigerating machine oil behavior)
FIG. 9 is a diagram showing the relationship between the refrigerant flow rate of the compressor 1 of the air conditioner according to Embodiment 2 of the present invention and the oil concentration in each oil return path. The relationship between the refrigerant flow rate of the compressor 1 and the oil concentration in the refrigerant that flows out from the outflow pipe 7b of the accumulator 7 and is sucked into the compressor 1 will be described with reference to FIG.
As shown in FIG. 9, in any oil return path, the lower the refrigerant flow rate, the lower the oil concentration. When the refrigerant flow rate is the same, the oil concentration when the refrigeration oil is returned to the compressor 1 through the oil return path 10b is lower than the oil concentration when the refrigerant return is returned to the compressor 1 through the oil return path 10a. As described in the first embodiment, the oil concentration of the refrigerating machine oil sucked into the compressor 1 has an allowable oil concentration that is an allowable lower limit value. Hereinafter, the refrigerant flow rate corresponding to the allowable oil concentration is referred to as “allowable refrigerant flow rate”. Therefore, when the refrigeration oil is returned through the oil return path 10b, the refrigerant flow rate must be equal to or higher than the allowable refrigerant flow rate. Further, as described in the first embodiment, the case where the refrigeration oil is returned to the compressor 1 by the oil return path 10b has a higher air conditioning capacity than the case where the refrigeration oil is returned to the compressor 1 by the oil return path 10a. improves. Therefore, when the refrigerant flow rate is equal to or higher than the allowable refrigerant flow rate, the refrigerating machine oil is returned by the oil return path 10b, and when it is less than the allowable refrigerant flow rate, the refrigerating machine oil may be returned by the oil return path 10a. However, even if the refrigerating machine oil is returned by the oil return path 10a, if the refrigerant flow rate decreases, the refrigerant concentration falls below the allowable concentration, which may cause a failure of the compressor 1. Therefore, as shown in FIG. 9, when a lower limit value of the refrigerant flow rate allowed in the case of returning the refrigerating machine oil by the oil return path 10a is set in advance, and when the lower limit value is exceeded, the air conditioner The operation may be stopped. Thereby, failure of the compressor 1 due to a decrease in the oil concentration accompanying a decrease in the refrigerant flow rate can be prevented. The lower limit value of the refrigerant flow rate is hereinafter referred to as “set minimum refrigerant flow rate”.

(Oil return path switching operation)
FIG. 10 is a control block diagram in the switching operation of the oil return path 10a and the oil return path 10b of the air conditioner according to Embodiment 2 of the present invention, and FIG. 11 is a diagram showing a control flow of the switching operation. is there.
As shown in FIG. 10, the detection means 1a for detecting the rotation speed, discharge temperature, discharge pressure, and suction pressure of the compressor 1, the open / close valve 9a in the oil return path 10a, and the open / close valve 9b in the oil return path 10b are as follows. The control device 20 is electrically connected. The detection unit 1 a detects the rotation speed, discharge temperature, discharge pressure, and suction pressure of the compressor 1 during operation of the air conditioner, and transmits each detection information to the control device 20. The control device 20 refers to the database 30 stored in the storage device, and derives the refrigerant flow rate of the compressor 1 based on each detection information received from the detection means 1a. Then, the control device 20 outputs a drive signal to the on-off valve 9a or the on-off valve 9b based on the derived refrigerant flow rate, and performs on / off control of the on-off valve 9a and the on-off valve 9b.

  Hereinafter, the switching operation of the oil return path 10a and the oil return path 10b by the open / close control of the on / off valve 9a and the on / off valve 9b will be described with reference to FIG.

(S11)
The detection unit 1 a detects the rotation speed, discharge temperature, discharge pressure, and suction pressure of the compressor 1 during operation of the air conditioner, and transmits each detection information to the control device 20. The control device 20 refers to the database 30 stored in the storage device, and derives the refrigerant flow rate of the compressor 1 based on each detection information received from the detection means 1a.

(S12)
The control device 20 determines whether or not the derived refrigerant flow rate is greater than or equal to a predetermined flow rate (here, the allowable refrigerant flow rate). As a result of the determination, if the refrigerant flow rate is equal to or higher than the predetermined flow rate, the process proceeds to step S13. On the other hand, when the refrigerant flow rate is less than the predetermined flow rate, the process proceeds to step S14.

(S13)
The control device 20 determines that the derived refrigerant flow rate is equal to or higher than a predetermined flow rate, sets the on-off valve 9a in the closed state and the on-off valve 9b in the open state by the drive signal, and the refrigerating machine oil separated by the oil separator 2 Is returned to the compressor 1 by the oil return path 10b.

(S14)
The control device 20 further determines whether or not the derived refrigerant flow rate is greater than or equal to the set minimum refrigerant flow rate. If the result of this determination is that the refrigerant flow rate is greater than or equal to the set minimum refrigerant flow rate, the routine proceeds to step S15. On the other hand, when the refrigerant flow rate is less than the set minimum refrigerant flow rate, the process proceeds to step S16.

(S15)
The control device 20 determines that the derived refrigerant flow rate is less than the predetermined flow rate and is equal to or greater than the set minimum refrigerant flow rate, and opens and closes the on-off valve 9a and the on-off valve 9b in accordance with the drive signal, thereby separating oil Control is performed so that the refrigerating machine oil separated by the container 2 is returned to the compressor 1 by the oil return path 10a.

(S16)
The control device 20 determines that the derived refrigerant flow rate is less than the set minimum refrigerant flow rate, and stops the operation of the air conditioner.

  In addition, as long as an air conditioner is not stopped by step S16, operation | movement of said step S11-S15 is repeated.

(Effect of Embodiment 2)
When the refrigerant flow is equal to or higher than the allowable refrigerant flow without causing the compressor 1 to fail as in the above configuration and operation, by returning the refrigeration oil separated from the oil separator 2 by the oil return path 10b to the compressor 1, Since the intake temperature can be lowered as compared with the case where the refrigeration oil is returned to the compressor 1 by the oil return path 10a, the air conditioning capability can be improved.

  Further, when the refrigerant flow rate is lower than the allowable refrigerant flow rate, the path for returning the refrigeration oil to the compressor 1 is switched to the oil return path 10a, so that the failure of the compressor 1 can be prevented and the safety is improved. be able to.

  As described above, the control device 20 refers to the database 30 stored in the storage device and derives the refrigerant flow rate of the compressor 1 based on each detection information received from the detection means 1a. However, the present invention is not limited to this. That is, the control device 20 does not include a storage device or does not include the database 30 and derives the refrigerant flow rate of the compressor 1 by calculation based on each detection information received from the detection unit 1a. Good. Accordingly, it is not necessary to provide a storage device, and the cost can be reduced. However, the derivation of the refrigerant flow rate by referring to the database 30 has an advantage that the calculation load can be reduced.

In the above description, the predetermined flow rate is the allowable refrigerant flow rate, but the present invention is not limited to this. That is, the predetermined flow rate may be set larger than the allowable refrigerant flow rate by a predetermined amount. As a result, the refrigeration oil having an allowable oil concentration or higher can be reliably returned to the compressor 1, so that the compressor 1 can be prevented from being broken and further improved in safety.
Further, the predetermined flow rate may be set, for example, in a range of 420 to 500 [kg / h].

  Moreover, although the control apparatus 20 shall derive | lead-out the refrigerant | coolant flow rate of the compressor 1 based on the rotation speed of the compressor 1 detected by the detection means 1a, discharge temperature, discharge pressure, and suction pressure, it is limited to this. Is not to be done. That is, for example, instead of the detection unit 1a, the control device 20 discharges the compressor 1, the suction pressure, the flow coefficient of each of the expansion devices 5a to 5c, and the refrigerant flowing into each of the expansion devices 5a to 5c. Detection means for detecting the density may be provided, and the refrigerant flow rate of the compressor 1 may be derived based on each detection information detected by the detection means. Specifically, for example, the control device 20 includes a storage device that stores a database 31 in which the refrigerant temperature and the refrigerant density are associated as illustrated in FIG. 12, and the detection unit includes the expansion devices 5 a to 5 c. The temperature of the refrigerant flowing into the refrigerant is detected, and the density of the refrigerant corresponding to the refrigerant temperature may be derived with reference to the database 31. When the expansion devices 5a to 5c are electronic expansion valves, the flow coefficient of the expansion devices 5a to 5c has a relationship as shown in FIG. 13 with the control pulse output to the expansion devices 5a to 5c. The control device 20 can derive the flow coefficient of each of the expansion devices 5a to 5c from the control pulse based on the relationship of FIG. And the control apparatus 20 is the following based on the density of the refrigerant | coolant which flows into each of the discharge pressure of the compressor 1 and the suction pressure which were obtained, each flow coefficient of the expansion apparatuses 5a-5c, and each expansion apparatus 5a-5c. The refrigerant flow rate of the compressor 1 can be derived from the equation (1).

Refrigerant flow rate = 27.1 × channel coefficient × {refrigerant density × (discharge pressure−suction pressure)} ^ (1/2)
(1)

  Note that the storage device described above is not necessarily provided in the control device 20, and may be any device that is installed outside the control device 20 and can be accessed from the control device 20.

  DESCRIPTION OF SYMBOLS 1 Compressor, 1a Detection means, 2 Oil separator, 3 Four-way valve, 4 Heat source side heat exchanger, 5a-5c Expansion device, 6a-6c Use side heat exchanger, 7 Accumulator, 7a Inflow pipe, 7b Outflow pipe , 7c Orifice, 7d Float, 7e Liquid level detector, 8a, 8b Throttle mechanism, 9a, 9b Open / close valve, 10a, 10b Oil return path, 20 Controller, 30, 31 Database.

Claims (11)

A compressor, a four-way valve, a heat source side heat exchanger, a throttling device, a use side heat exchanger, and a refrigeration cycle configured by connecting accumulators with refrigerant piping;
An oil separator that is installed between the compressor and the four-way valve and separates refrigeration oil from refrigerant discharged from the compressor;
A first oil return path in which the oil separator and the suction port side of the compressor are connected, and a first on-off valve and a first throttle mechanism are installed on the path;
A second oil return path in which the oil separator and the inflow side of the accumulator are connected, and a second on-off valve and a second throttle mechanism are installed on the path;
A control device for controlling opening and closing of the first on-off valve and the second on-off valve;
With
In the first oil return path, when the first on-off valve is in an open state, the refrigerating machine oil separated from the refrigerant by the oil separator is sucked into the suction port of the compressor,
In the second oil return path, when the second on-off valve is in an open state, the refrigerating machine oil separated from the refrigerant by the oil separator is caused to flow from the inlet of the accumulator,
The control device controls the first on-off valve and the second on-off valve so that an oil concentration, which is a concentration of refrigerating machine oil contained in a refrigerant sucked into the compressor, is equal to or higher than an allowable oil concentration of the compressor. By performing opening / closing control, the path for sucking the compressor oil separated by the oil separator into the compressor is switched to either the first oil return path or the second oil return path. Air conditioner. Liquid level detection means for detecting the liquid level height of the liquid refrigerant stored in the accumulator,
The controller is
If it is determined that the liquid level height is detected by the liquid level height detection means to be equal to or higher than a predetermined height, the first on-off valve is opened, and the second on-off valve is closed,
When it is determined by the liquid level detection means that the liquid level is detected to be less than the predetermined height, the first on-off valve is closed and the second on-off valve is opened. The air conditioner according to claim 1. The air conditioner according to claim 2, wherein the predetermined height is an allowable liquid level height that is the liquid level height corresponding to the allowable oil concentration for the second oil return path. The predetermined height is a value obtained by subtracting a predetermined amount from an allowable liquid level height that is the liquid level corresponding to the allowable oil concentration for the second oil return path. Air conditioner. The air conditioner according to claim 2, wherein the predetermined height is set in a range of 14300 / A to 22900 / A [mm], where A is a horizontal sectional area of the accumulator. A detecting means for detecting the rotation speed, discharge temperature, discharge pressure and suction pressure of the compressor;
The controller is
Deriving the refrigerant flow rate of the compressor based on the rotation speed, the discharge temperature, the discharge pressure and the suction pressure detected by the detection means,
When the refrigerant flow rate is greater than or equal to a predetermined flow rate, the first on-off valve is closed and the second on-off valve is opened, and when the refrigerant flow rate is less than the predetermined flow rate, the first on-off valve is opened. And the said 2nd on-off valve is made into a closed state. The air conditioner of Claim 1 characterized by the above-mentioned. A storage device storing a database that associates the rotational speed, the discharge temperature, the discharge pressure, the suction pressure, and the refrigerant flow rate;
The control device derives the refrigerant flow rate corresponding to the rotation speed, the discharge temperature, the discharge pressure, and the suction pressure with reference to the database stored in the storage device. 6. The air conditioner according to 6. A detection means for detecting a discharge pressure of the compressor, a suction pressure, a flow path coefficient of the throttle device, and a density of the refrigerant flowing into the throttle device;
The controller is
Deriving the refrigerant flow rate of the compressor based on the discharge pressure, the suction pressure, the flow path coefficient and the refrigerant density detected by the detection means,
When the refrigerant flow rate is greater than or equal to a predetermined flow rate, the first on-off valve is closed and the second on-off valve is opened, and when the refrigerant flow rate is less than the predetermined flow rate, the first on-off valve is opened. And the said 2nd on-off valve is made into a closed state. The air conditioner of Claim 1 characterized by the above-mentioned. The said predetermined flow rate is the allowable refrigerant | coolant flow rate which is the said refrigerant | coolant flow rate corresponding to the said permissible oil density | concentration about the said 2nd oil return path | route. The any one of Claims 6-8 characterized by the above-mentioned. Air conditioner. The predetermined flow rate is a value obtained by adding a predetermined amount to an allowable refrigerant flow rate that is the refrigerant flow rate corresponding to the allowable oil concentration for the second oil return path. The air conditioner as described in any one of Claims. The air conditioner according to any one of claims 6 to 8, wherein the predetermined flow rate is set in a range of 420 to 500 [kg / h].

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