JP5895683B2 - Refrigeration equipment - Google Patents

Description

  The present invention relates to a refrigeration apparatus, and more particularly to a refrigeration apparatus including a refrigerant container for storing refrigerant sucked into a compressor.

  Conventionally, some refrigeration apparatuses such as an air conditioner and a hot water supply apparatus are provided with an accumulator. The accumulator is provided on the suction side of the compressor and plays a role of temporarily storing the refrigerant returned to the compressor from the evaporator of the refrigeration apparatus and suppressing the liquid refrigerant from being sucked into the compressor.

  In the compressor of the refrigerating apparatus, there is a problem of rising oil that a part of the refrigerating machine oil stored in the compressor is discharged to the outside of the compressor together with the compressed gas refrigerant. In the refrigeration apparatus having the accumulator, the refrigeration oil discharged to the outside of the compressor together with the gas refrigerant is accumulated in the accumulator together with the liquid refrigerant before returning to the compressor through the refrigeration circuit.

  In such an accumulator, as described in Patent Document 1 (Japanese Patent Application Laid-Open No. 2004-263395), refrigerating machine oil is supplied to the compressor at the lowermost part of the outlet pipe for guiding the gas refrigerant to the compressor. An oil return hole is formed so as to return. Even if the refrigeration oil and the liquid refrigerant are separated into two layers, the refrigeration apparatus of Patent Document 1 returns the refrigeration oil to the compressor through the oil return hole at the bottom by stirring with hot gas. Yes.

  However, it takes time to perform such agitation to return the refrigeration oil to the compressor. If refrigerating machine oil is quickly returned without sufficient agitation, a large amount of liquid refrigerant is supplied to the compressor from the bottom oil return hole, resulting in a wet operation, and liquid compression occurs in the compressor. There is a fear.

  An object of the present invention is to suppress a liquid refrigerant that returns to the compressor, while quickly returning a large amount of refrigeration oil to the compressor.

  A refrigerating apparatus according to a first aspect of the present invention includes a compressor and an evaporator provided in the front stage of the compressor, and circulates a refrigerating machine oil used in the compressor, a refrigerating circuit including the compressor and the evaporator. A refrigeration system operated in an environment where two layers can be separated into a lower refrigerant-rich layer and an upper oil-rich layer when refrigerant is mixed, and is disposed between an evaporator and a suction port of a compressor. A refrigerant container for storing the refrigerant in the internal space; a refrigerant container that is inserted into the internal space of the refrigerant container to guide the refrigerant to the suction port of the compressor and sucks the gas refrigerant in the internal space; A pipe having an oil return hole formed at a position above the liquid level and below the suction port, and above a position of the oil return hole when a predetermined condition is satisfied, and Strengthen the liquid level of the refrigerant container below the suction port position Further comprising to a control device which performs automatically the oil-return operation for moving refrigerating machine oil in the liquid surface level adjacent to the suction port of the compressor through the oil return holes in the pipe is raised, the.

  In the refrigeration apparatus according to the first aspect, the liquid level is forced when the refrigerant and the refrigerating machine oil are separated into two layers in the refrigerant container and the lower refrigerant rich layer and the upper oil rich layer exist. And the oil rich layer of refrigeration oil can be returned to the compressor inlet through the oil return hole.

Further, the refrigeration apparatus according to the first aspect further includes an expansion mechanism provided at the front stage of the evaporator in the refrigeration circuit, and a condenser provided at the front stage of the expansion mechanism and at the rear stage of the compressor. In order to forcibly raise the liquid level of the refrigerant container in the oil return operation, the degree of supercooling on the front side of the condenser is set to a value lower than the target value of the degree of supercooling during steady operation of the refrigeration system. Control.

Further, in the refrigeration apparatus according to the first aspect, the liquid level can be significantly increased by forcibly lowering the target value of the degree of supercooling, so that the position of the oil return hole is higher than the liquid level during steady operation. The liquid refrigerant can be sufficiently prevented from entering the pipe from the oil return hole during steady operation.

Refrigeration system according to a second aspect of the present invention is the refrigeration apparatus of the first view point, the control device that the predetermined time has elapsed since the start of operation of the refrigeration system with predetermined conditions.

In the refrigeration apparatus according to the second aspect, the oil return operation can be periodically performed every time a predetermined time elapses.

In the refrigeration apparatus according to the third aspect of the present invention, in the refrigeration apparatus according to the first aspect or the second aspect , the pipe is formed at a predetermined position below the liquid level of the refrigerant container during steady operation of the refrigeration apparatus. And another oil return hole having an opening area smaller than that of the oil return hole.

In the refrigeration apparatus according to the third aspect, when the two-layer separation is not performed, the oil return can be performed using another oil return hole, so that it is possible to omit the control for forcibly increasing the liquid level when the two-layer separation is not performed.

In the refrigeration apparatus according to the fourth aspect of the present invention, in the refrigeration apparatus according to the third aspect , the control device is configured such that a predetermined time elapses from the start of operation of the refrigeration apparatus and that the temperature around the refrigerant container is equal to or lower than the predetermined temperature. Is a predetermined condition.

In the refrigeration apparatus according to the fourth aspect , by setting the predetermined temperature to a temperature at which two layers can be separated, the oil level operation can be performed by raising the liquid level when the two layers are separated.

  In the refrigeration apparatus according to the first aspect, the liquid level of the refrigerant container is forcibly raised above the position of the oil return hole and below the position of the suction port, so that the liquid level of the refrigerant container during steady operation Since the refrigeration oil in the oil-rich layer can be returned to the suction port of the compressor from the oil return hole formed above and below the suction port, the liquid refrigerant returning to the compressor is suppressed. Many refrigeration oils can be quickly returned to the compressor.

Further, in the refrigeration apparatus according to the first aspect, the control of returning the liquid refrigerant to the compressor becomes easy.

In the refrigeration apparatus according to the second aspect, the oil return operation can be performed periodically, and the refrigerating machine oil can be prevented from being insufficient.

In the refrigeration apparatus according to the third aspect, the control for forcibly increasing the liquid level can be omitted, and the number of times of interrupting the air conditioning operation can be reduced to efficiently perform heat exchange.

In the refrigeration apparatus according to the fourth aspect , when the two layers are separated, the liquid level can be raised and the oil return operation can be performed, so that the refrigeration oil does not run short while reducing the number of times of interrupting the air conditioning operation. Oil return operation can be performed.

The circuit diagram which shows an example of a structure of the air conditioning apparatus which concerns on one Embodiment of this invention. The front view which shows an example of the utilization side heat exchanger used with the air conditioning apparatus of FIG. The perspective view which shows an example of the heat source side heat exchanger used with the air conditioning apparatus of FIG. Schematic which shows an example of the refrigerant | coolant storage tank used with the air conditioning apparatus of FIG. The conceptual diagram for demonstrating the liquid level at the time of the steady operation of a refrigerant | coolant storage tank. The conceptual diagram for demonstrating the liquid level at the time of the oil return operation | movement of a refrigerant | coolant storage tank. The block diagram which shows an example of the apparatus connected to the control apparatus of the air conditioning apparatus of FIG. Schematic which shows the other example of the refrigerant | coolant storage tank which concerns on the modification of this invention.

  Hereinafter, an embodiment of an air conditioner will be described with reference to the drawings, taking an air conditioner as an example of a refrigeration apparatus according to the present invention.

(1) Outline of Configuration of Air Conditioner FIG. 1 is a refrigeration circuit diagram showing an outline of a configuration of an air conditioner according to an embodiment of the present invention. The air conditioner 10 is a refrigeration apparatus capable of performing a cooling operation as a cooling operation and a heating operation as a heating operation by performing a vapor compression refrigeration cycle. The air conditioner 10 includes, for example, a heat source side unit 20 installed outside the room and a use side unit 30 installed inside the room, for example. The heat source side unit 20 and the use side unit 40 are connected by the liquid side refrigerant communication pipe 12 and the gas side refrigerant communication pipe 13 to constitute the refrigeration circuit 11 in which the refrigerant circulates. Then, a refrigerant is sealed in the air conditioner 10, and a refrigeration cycle operation is performed in which the refrigerant is compressed, cooled, decompressed, heated and evaporated, and then compressed again as described later. It is like that. For example, R32 is used as the refrigerant. Various devices constituting the air conditioner 10 are controlled by the control device 15. The control device 15 includes a heat source side control unit 16 disposed in the heat source side unit 20 and a use side control unit 17 disposed in the use side unit 40, and these heat source side control unit 16 and use side control. The unit 17 is connected to each other by a communication line 14.

(1-1) Usage Side Unit The usage side unit 40 includes a usage side refrigerant circuit 40a that constitutes a part of the refrigeration circuit 11, and the usage side heat exchanger 42 is included in the usage side refrigerant circuit 40a. The use side unit 40 further includes a use side fan 44. The usage-side fan 44 is a fan capable of changing the air volume of the air supplied to the usage-side heat exchanger 42, and is rotationally driven by a usage-side fan motor 44a composed of a DC fan motor or the like. Air is taken into the use side unit 40 by the use side fan 44 and blown to the use side heat exchanger 42, and heat exchange between the refrigerant in the use side heat exchanger 42 and the air taken into the use side unit 40 is performed. Promoted. In the usage-side fan 44, for example, a centrifugal fan or a multiblade fan is driven by the usage-side fan motor 44a in order to send air to the usage-side heat exchanger.

  Further, the use side unit 40 is provided with a use side control unit 17, a use side liquid pipe temperature sensor 45, a use side gas pipe temperature sensor 46, and a use side environment temperature sensor 47. Data on the temperatures measured by the use side liquid pipe temperature sensor 45, the use side gas pipe temperature sensor 46 and the use side environment temperature sensor 47 are transmitted to the use side control unit 17.

(1-1-1) Use side heat exchanger The use side heat exchanger 42 is a cross fin type heat exchanger, and the air passing through the heat transfer fins 421 and the heat transfer tubes 423 shown in FIG. Heat exchange is performed with the refrigerant flowing inside. With this function, the use side heat exchanger 42 functions as a refrigerant evaporator during cooling operation to cool the air taken into the use side unit 40, and functions as a refrigerant condenser during heating operation. The air taken into the use side unit 40 is heated. In FIG. 2, the heat transfer fins 421 are thin aluminum flat plates, and a plurality of through holes are formed in one heat transfer fin 421. The heat transfer tube 423 includes a straight tube 423a inserted into a through hole of the heat transfer fin 421, and a first U-shaped tube 423b and a second U-shaped tube 423c that connect ends of adjacent straight tubes 423a.

  The straight pipe 423 a is inserted into the through-holes of the heat transfer fins 421, and then pipe-expanded by a pipe expander to be in close contact with the heat transfer fins 421. The straight tube 423a and the first U-shaped tube 423b are integrally formed. The second U-shaped tube 423c is formed by welding or the like after the straight tube 423a is inserted into the through hole of the heat transfer fin 421 and expanded. Connected to the end of 423a.

(1-2) Heat Source Side Unit The heat source side unit 20 includes a heat source side refrigerant circuit 20 a that constitutes a part of the refrigeration circuit 11. The heat source side refrigerant circuit 20a includes a compressor 21, a four-way switching valve 22, a heat source side heat exchanger 23, an expansion mechanism 24, a refrigerant storage tank 50, a liquid side closing valve 26, a gas side closing valve 27, and a gas-liquid separation. And a heat source side unit refrigerant pipe 31 for connecting these devices. The heat source side unit 20 is disposed so as to face the heat source side heat exchanger 23, and has a heat source side fan 35 for promoting heat exchange between air and the refrigerant. The heat source side fan 35 sucks air into the unit, exchanges heat with the refrigerant in the heat source side heat exchanger 23, and discharges the air after heat exchange to the outside of the unit. The heat source side fan 35 is a blower fan capable of changing the air volume of air supplied to the heat source side heat exchanger 23. For example, a propeller fan driven by a heat source side fan motor 35a composed of a DC fan motor or the like. Etc.

  Further, the heat source side unit 20 is provided with a heat exchanger inlet / outlet temperature sensor 32, a heat exchanger temperature sensor 33, an environmental temperature sensor 34, a discharge pressure sensor 36, a discharge temperature sensor 37, a suction pressure sensor 38, and a suction temperature sensor 39. It has been. As the heat exchanger inlet / outlet temperature sensor 32, the heat exchanger temperature sensor 33, the environmental temperature sensor 34, the discharge temperature sensor 37, and the suction temperature sensor 39, for example, a thermistor is used. And the data regarding the temperature measured by these temperature sensors 32-34, 37, 38 are transmitted to the heat source side control part 16. FIG.

(1-2-1) Compressor The compressor 21 sucks gas refrigerant through the gas-liquid separator 28, compresses the sucked gas refrigerant to a high pressure in the refrigeration cycle, and discharges it from the discharge side. The gas-liquid separator 28 is a container having a function of storing liquid refrigerant in order to supply gas refrigerant to the compressor 21. In other words, the gas-liquid separator 28 is an accumulator attached to the compressor 21. The compressor 21 has a sealed structure in which a compressor motor 21b, a drive shaft 21c, and a compression element 21d are accommodated in a compressor casing 21a. The compressor motor 21b drives the compression element 21d via the drive shaft 21c. For example, the rotation speed of the compressor motor 21b is controlled by an inverter, and the compressor 21 is configured to be able to vary the operating capacity. Refrigerating machine oil for maintaining good lubricity of the compression element 21d and the like is stored in a lower portion in the compressor casing 21a of the compressor 21.

(1-2-2) Four-way switching valve The four-way switching valve 22 is a mechanism for switching the refrigerant flow direction in the refrigeration circuit 11. The four-way switching valve 22 connects the discharge side of the compressor 21 and the gas side of the heat source side heat exchanger 23 during the cooling operation, and connects the suction side of the compressor 21 and the gas side closing valve 27 to a gas-liquid separator. 28 and the refrigerant storage tank 50 are connected. That is, during the cooling operation, the four-way switching valve 22 is controlled by the heat source side control unit 16 and is in the solid line state of FIG. The four-way switching valve 22 connects the discharge side of the compressor 21 and the gas side shut-off valve 27 and connects the suction side of the compressor 21 and the gas side of the heat source side heat exchanger 23 during heating operation. . That is, during the heating operation, the four-way switching valve 22 is controlled by the heat source side control unit 16 to be in the dotted line state of FIG.

(1-2-3) Heat source side heat exchanger The heat source side heat exchanger 23 performs heat exchange between the air taken in from the outside of the heat source side unit 20 and the refrigerant flowing inside. Here, a so-called laminated heat exchanger is used as the heat source side heat exchanger 23. Since the capacity of the heat source side heat exchanger 23 is smaller than the capacity of the use side heat exchanger 42, the amount of refrigerant in the refrigeration circuit 11 is reduced. In addition, although an excessive refrigerant | coolant generate | occur | produces at the time of air_conditionaing | cooling operation, since the excessive refrigerant | coolant is accommodated in the refrigerant | coolant storage tank 50, it will be prevented that a refrigerant | coolant control will be obstructed.

  In FIG. 3, the heat source side heat exchanger 23 includes a flat tube 231, a corrugated fin 233, and a header 235. The flat tube 231 is formed of aluminum or an aluminum alloy, and has a flat portion 231a serving as a heat transfer surface and a plurality of internal flow paths (not shown) through which a refrigerant flows. The flat tubes 231 are arranged in a plurality of stages with the flat portion 231a facing up and down.

  The corrugated fins 233 are aluminum or aluminum alloy fins bent into a corrugated shape. The corrugated fin 233 is disposed in a ventilation space sandwiched between upper and lower flat tubes 231, and a valley portion and a mountain portion are in contact with the flat portion 231 a of the flat tube 231. In addition, the trough part, the peak part, and the plane part 231a are brazed and welded.

  The header 235 is connected to both ends of the flat tubes 231 arranged in a plurality of stages in the vertical direction. The header 235 has a function of supporting the flat tube 231, a function of guiding the refrigerant to the internal flow path of the flat tube 231, and a function of collecting the refrigerant that has come out of the internal flow path.

  In the front view of the heat source side heat exchanger 23, the refrigerant flowing from the inlet 235 a of the right header 235 is distributed almost evenly to each internal flow path of the uppermost flat tube 231 and flows toward the left header 235. The refrigerant that has reached the left header 235 is evenly distributed to each internal flow path of the second-stage flat tube 231 and flows toward the right header 235. Thereafter, the refrigerant in the odd-numbered flat tubes 231 flows toward the left header 235, and the refrigerant in the even-numbered flat tubes 231 flows toward the right header 235. Then, the refrigerant in the flat tube 231 at the lowest level and the even number level flows toward the right header 235, gathers at the right header 235, and flows out from the outlet 235b.

  When the heat source side heat exchanger 23 functions as an evaporator, the refrigerant flowing in the flat tube 231 absorbs heat from the air flow flowing in the ventilation space via the corrugated fins 233. When the heat source side heat exchanger 23 functions as a condenser, the refrigerant flowing in the flat tube 231 radiates heat to the air flow flowing in the ventilation space via the corrugated fins 233.

  In the present embodiment, the capacity of the heat source side heat exchanger 23 is smaller than the capacity of the use side heat exchanger 42 by using the heat source side heat exchanger 23 as a stacked heat exchanger as described above. . This is because the heat source side heat exchanger and the use side heat exchanger are both cross fin type heat exchangers, and only the heat source side heat exchanger is changed to a stacked heat exchanger having equivalent heat exchange performance. This is because the heat source side heat exchanger capacity / use side heat exchanger volume ratio is less than 1.0 when replaced. That is, the capacity of the stacked heat exchanger (the heat source side heat exchanger 23) is not only smaller than the volume of the conventional heat source side heat exchanger of the cross fin type, but the cross fin type connected thereto is used. It becomes smaller than the capacity of the side heat exchanger 42. Therefore, surplus refrigerant is generated during the cooling operation. Therefore, in the refrigeration circuit 11 of the present embodiment, the excess refrigerant is accommodated in the refrigerant storage tank 50. In addition, when the heat source side heat exchanger capacity / use side heat exchanger volume ratio is 0.3 to 0.9, it is preferable to use the refrigerant storage tank 50 that stores surplus refrigerant, but the heat source side heat exchanger capacity / Use of the refrigerant storage tank 50 enables stable refrigerant control even when the use side heat exchanger volume ratio is 1.0.

(1-2-4) Expansion Mechanism The expansion mechanism 24 is disposed in the heat source side unit refrigerant pipe 31 between the heat source side heat exchanger 23 and the liquid side shut-off valve 26 in order to adjust the refrigerant pressure and the refrigerant flow rate. Is done. The expansion mechanism 24 is an electric valve whose opening degree is adjusted according to a command from the control device 15.

(1-2-5) Shut-off valve and refrigerant communication pipe The liquid-side shut-off valve 26 and the gas-side shut-off valve 27 are manual valves that are manually opened and closed, and the liquid-side refrigerant communication pipe 12 and the gas-side refrigerant communication pipe, respectively. 13 is connected. The liquid side refrigerant communication pipe 12 connects between the liquid side of the usage side heat exchanger 42 of the usage side unit 40 and the liquid side closing valve 26 of the heat source side unit 20. The gas side refrigerant communication pipe 13 connects between the gas side of the usage side heat exchanger 42 of the usage side unit 40 and the gas side closing valve 27 of the heat source side unit 20.

(1-2-6) Refrigerant storage tank, inlet piping, and outlet piping FIG. 4 is a conceptual diagram showing a schematic configuration of the refrigerant storage tank. As shown in FIG. 1, the refrigerant storage tank 50 is disposed on the upstream side of the refrigerant flow of the compressor 21, particularly on the upstream side of the gas-liquid separator 28 attached to the compressor 21. This is a container capable of performing gas-liquid separation and temporary storage of the refrigerant sucked in. As shown in FIG. 2, an inlet pipe 51 and an outlet pipe 52 are inserted into the refrigerant storage tank 50.

  The refrigerant storage tank 50 is a vertical cylindrical container extending in the vertical direction, and includes a cylindrical trunk portion 50a, and a bowl-shaped upper collar portion 50b and a lower collar portion 50c that close an opening in the vertical direction of the trunk portion 50a. Consists of. Then, the refrigerant that has passed through the four-way switching valve 22 flows into the internal space S of the refrigerant storage tank 50 through the inlet pipe 51. The refrigerant storage tank 50 stores the liquid refrigerant in the lower part of the internal space S and stores the gas refrigerant in the upper part of the internal space S, so that the gas-liquid two-phase refrigerant is converted into the gas refrigerant and the liquid refrigerant. It is comprised so that it may isolate | separate. The separated gas refrigerant flows through the outlet pipe 52 to the gas-liquid separator 28 attached to the compressor 21. For example, the gas-liquid separator 28 includes an oil return hole similar to the conventional one, and has a configuration that allows oil return without performing an oil return operation.

  The inlet pipe 51 is a pipe that extends from the four-way switching valve 22 to the refrigerant storage tank 50. The inlet pipe 51 is inserted into the internal space S through the upper flange portion 50b downward. The inlet 51 a of the inlet pipe 51 is disposed in an upper space of the internal space S of the refrigerant storage tank 50. During steady operation, the upper space of the internal space S is filled with the gas refrigerant, and the liquid refrigerant does not reach the inlet 51a in a normal state. Accordingly, the liquid refrigerant in the gas-liquid two-layer refrigerant flowing into the internal space S from the inflow port 51a falls below the internal space S, while the gas refrigerant in the gas-liquid two-layer refrigerant is in the inner space. Expands into the upper space of S.

  The outlet pipe 52 is a pipe extending from the refrigerant storage tank 50 to the gas-liquid separator 28. The outlet pipe 52 extends from the inner space S toward the outside of the refrigerant storage tank 50 through the upper flange portion 50b from the lower side to the upper side, and is bent in a U shape in the inner space S. The suction port 52 a of the outlet pipe 52 is disposed so as to be positioned in the upper space of the internal space S of the refrigerant storage tank 50 with its opening facing upward. During steady operation, the upper space of the internal space S is filled with the gas refrigerant, and the liquid refrigerant does not reach the suction port 52a in a normal state. Therefore, the refrigerant flowing out of the suction port 52a is only the gas refrigerant separated from the gas-liquid two-layer refrigerant.

  The outlet pipe 52 is provided with an oil return hole 52b. The oil return hole 52b is provided above a position lowering by a length L1 than the suction port 52a. That is, the oil return hole 52b is a hole different from the pressure equalization hole formed in the outlet pipe of a general accumulator that plays the role of preventing the liquid refrigerant from returning when the compressor 21 is stopped. The pressure equalization hole serves to balance the pressure in the accumulator and the pressure in the downstream pipe, and adjusts the number and opening diameter to adjust the flow rate of the gas refrigerant flowing in the downstream pipe. Therefore, the liquid refrigerant is arranged at a very high position where it does not reach. Therefore, as will be described later, the oil return hole 52b disposed at a position where the liquid refrigerant reaches when returning oil is different from the pressure equalizing hole, and although not shown, the pressure equalizing hole is the oil return hole 52b. It is provided separately.

  Here, the relationship between the liquid level of the liquid refrigerant mixed with refrigerating machine oil and the height of the oil return hole 52b will be described with reference to FIGS. The position indicated by the symbol LLs in FIG. 5 is the liquid level during steady operation. Here, the operation at the time of oil return is referred to as non-steady time operation (hereinafter referred to as oil return operation), and the operation when the other air conditioner 10 is normally operated is distinguished as the normal time operation. The constant liquid level LLs is defined as the highest liquid level of the liquid refrigerant stored in the internal space S of the refrigerant storage tank 50 during the steady operation of the air conditioner 10. Therefore, in the case of normal operation of the air conditioner 10, the liquid level LLs is not exceeded even though the liquid level LLs may be lower than the steady level. The regular liquid level LLs is determined by conducting various experiments in advance by setting various operating conditions of the air conditioner 10. For example, in the refrigeration circuit 11, the temperature is determined under such a temperature control condition that there are many refrigerants that could not be evaporated by the heat source side heat exchanger 23 or the use side heat exchanger 42 functioning as a refrigerant evaporator. For example, it is determined based on the liquid level of the refrigerant storage tank 50 of the air-conditioning apparatus 10 operated using a predetermined condition such that the environmental temperature is low when the heating operation is performed.

  In the air conditioner 10 in which the liquid level of the liquid refrigerant in the refrigerant storage tank 50 is temporarily increased during the defrost operation or the start operation, the liquid refrigerant is removed from the oil return hole at that time. In the case where it may flow out to 28, such a defrosting operation or a starting operation may be excluded from the steady operation and the steady operation may be defined.

  As shown in FIG. 6, the liquid level LLa during the oil return operation is higher than the oil return hole 52b. 6 is an example of the level of the boundary surface between the oil rich layer and the refrigerant rich layer during the oil return operation. The boundary surface between the oil-rich layer and the refrigerant-rich layer may be visible with the naked eye, such as R32, but may be difficult to distinguish. Further, the liquid level LLb at the boundary surface also varies depending on the amount of refrigerating machine oil. The level LLb at the boundary surface shown in FIG. 6 is an example in the case where the oil rich layer and the refrigerant rich layer are relatively clearly separated and are in a preferable position for returning the refrigeration oil.

  The relationship between the oil return hole 52b, the normal liquid level LLs, the liquid level LLa during the oil return operation, and the boundary level LLb is compared with the height of the suction port 52a as follows. That is, the length L3 from the suction port 52a to the liquid level LLa during the oil return operation <the length L1 from the suction port 52a to the oil return hole 51b <the length from the suction port 52a to the liquid level LLs at the steady state L2 is set so as to hold the relationship. Then, preferably, as shown in FIG. 6, the relationship of length L1 from the suction port 52a to the oil return hole 51b <length L4 from the suction port 52a to the level LLb of the boundary surface is established. is there. However, the liquid level LLa at the time of the oil return operation is set so as not to be higher than the suction port 52a so that the liquid back does not occur.

(2) Control device In order to perform the air conditioning operation correctly and efficiently in the air conditioner 10, the heat source side unit 20 and the use side unit 40 include the heat source side control unit 16 and the use incorporated in each device. It is controlled by the side controller 17. As shown in FIG. 7, the heat source side control unit 16 and the use side control unit 17 constituting the control device 15 are connected to each other via the communication line 14 and transmit / receive data to / from each other. The heat source side control unit 16 and the use side control unit 17 include a CPU (Central Processing Unit), a memory, a peripheral circuit, and the like.

  A heat exchanger inlet / outlet temperature sensor 32 and a heat exchanger temperature sensor 33 are provided around the heat source side heat exchanger 23 of the heat source side unit 20, and flow into the air inlet side of the heat source side unit 20. An ambient temperature sensor 34 is provided for detecting the temperature of the air to be heated (that is, the ambient temperature at which the heat source unit 20 is placed). The heat exchanger temperature sensor 33 measures the temperature of the refrigerant inside the heat source side heat exchanger 23. The heat exchanger inlet / outlet temperature sensor 32 provided at the inlet / outlet of the heat source side heat exchanger 23 measures the temperature of the refrigerant flowing from the heat source side heat exchanger 23 to the use side unit 40. The refrigerant pipe on the discharge side of the compressor 21 is provided with a discharge pressure sensor 36 for detecting the compressor discharge pressure and a discharge temperature sensor 37 for detecting the compressor discharge temperature. The refrigerant pipe on the suction side of the compressor 21 is provided with a suction pressure sensor 38 that detects the suction pressure of the compressor 21 and a suction temperature sensor 39 that detects the temperature of the gas refrigerant sucked into the compressor 21. Yes. The refrigerant pressure data measured by the suction pressure sensor 38 and the discharge pressure sensor 36 are transmitted to the heat source side control unit 16.

  Further, a compressor motor 21b, a four-way switching valve 22, an expansion mechanism 24, and a heat source side fan motor 35a of the compressor 21 are connected to the heat source side control unit 16. The heat source side control unit 16 controls, for example, the rotation speed of the compressor motor 21b and the heat source side fan motor 35a and their operation / stop, controls the switching of the four-way switching valve 22, and controls the opening degree of the expansion mechanism 24. Is controlled.

  The usage-side unit 40 is provided with a usage-side liquid pipe temperature sensor 45 and a usage-side gas pipe temperature sensor 46 for measuring the refrigerant temperature at the inlet / outlet of the usage-side heat exchanger 42. A use-side environmental temperature sensor 47 for measuring the temperature is provided. The temperature data measured by these temperature sensors 45 to 47 is transmitted to the use side control unit 17. In addition, the usage-side control unit 17 is connected to a usage-side fan motor 44 a of the usage-side fan 44, a wind direction adjusting mechanism 48, a display unit 49, and the like. The use side control unit 17 controls, for example, the rotation speed and operation / stop of the use side fan motor 44a. The direction of the conditioned air blown from the outlet of the use side unit 40 is adjusted by the air direction adjustment mechanism 48 changing the angle of a wind direction adjustment plate (not shown) provided in the use side unit 40. The use side control unit 17 outputs a control signal for instructing the display to the display unit 49 to perform various displays.

(3) Operation of Air Conditioner Next, the basic operation of the air conditioner 1 according to the present embodiment will be described. Control in various operations described below is performed by the control device 15.

(3-1) Cooling Operation During the cooling operation, the four-way switching valve 22 is in the state shown by the solid line in FIG. 1, that is, in the use side unit 40, the discharge side of the compressor 21 is the gas of the heat source side heat exchanger 23. And the suction side of the compressor 21 is connected to the gas side of the use side heat exchanger 42 via the gas side shut-off valve 27 and the gas side refrigerant communication pipe 13. During the cooling operation, the liquid side closing valve 26 and the gas side closing valve 27 are opened, and the expansion mechanism 24 of the usage side unit 40 is connected to the outlet of the usage side heat exchanger 42 (that is, the gas of the usage side heat exchanger 42). The degree of opening is adjusted so that the degree of superheat of the refrigerant at the side) becomes a predetermined superheat degree target value. For example, the degree of superheat of the refrigerant at the outlet of the use side heat exchanger 42 of the use side unit 40 is the refrigerant temperature detected by the use side liquid pipe temperature sensor 45 from the refrigerant temperature value detected by the use side gas pipe temperature sensor 46. It is detected by subtracting the value (corresponding to the evaporation temperature). The compressor 21, the heat source side fan 35, and the use side fan 44 are driven in the state of the air conditioner 10, and the low-pressure gas refrigerant is sucked into the compressor 21 and compressed to become a high-pressure gas refrigerant. . Thereafter, the high-pressure gas refrigerant is sent to the heat source side heat exchanger 23 via the four-way switching valve 22, and is heat-exchanged with the air supplied by the heat source side fan 35, condensed, and condensed with the high-pressure liquid refrigerant. Become. The high-pressure liquid refrigerant is decompressed to near the suction pressure of the compressor 21 by the expansion mechanism 24 to become a low-pressure gas-liquid two-phase refrigerant.

  Then, the low-pressure gas-liquid two-phase refrigerant is sent from the heat source side unit 20 to the usage side unit 40 via the liquid side closing valve 26 and the liquid side refrigerant communication pipe 12. The low-pressure gas-liquid two-phase refrigerant enters the usage-side heat exchanger 42 of the usage-side unit 40, exchanges heat with air in the usage-side heat exchanger 42, and is evaporated to become a low-pressure gas refrigerant.

  This low-pressure gas refrigerant is sent to the heat source side unit 20 via the gas side refrigerant communication pipe 13, and again sucked into the compressor 21 via the gas side closing valve 27 and the four-way switching valve 22. . At that time, the excess refrigerant in the refrigeration circuit 11 is stored in the refrigerant storage tank 50. Furthermore, when the low-pressure gas refrigerant sent from the refrigerant storage tank 50 to the gas-liquid separator 28 is still mixed with the liquid refrigerant, the gas refrigerant is separated by the gas-liquid separator 28 and sent to the compressor 21. .

(3-2) Heating Operation During the heating operation, the four-way switching valve 22 is in the state indicated by the broken line in FIG. 1, that is, the discharge side of the compressor 21 is connected via the gas side closing valve 27 and the gas side refrigerant communication pipe 13. It is connected to the gas side of the use side heat exchanger 42 and the suction side of the compressor 21 is connected to the gas side of the heat source side heat exchanger 23. Therefore, the liquid side closing valve 26 and the gas side closing valve 27 are opened. The opening degree of the expansion mechanism 24 is adjusted so that the supercooling degree of the refrigerant at the outlet of the use side heat exchanger 42 becomes a predetermined supercooling degree target value. The degree of supercooling of the refrigerant at the outlet of the use side heat exchanger 42 is calculated by converting the discharge pressure of the compressor 21 detected by the discharge pressure sensor 36 into a saturation temperature value corresponding to the condensation temperature. This is detected by subtracting the refrigerant temperature value detected by the use side liquid pipe temperature sensor 45.

  In the refrigeration circuit 11, first, the low-pressure gas refrigerant is sucked into the compressor 21 and compressed to become high-pressure gas refrigerant, and the high-pressure gas refrigerant becomes the four-way switching valve 22, the gas-side closing valve 27, and the gas-side refrigerant communication pipe. 13 to the use side unit 40. The high-pressure gas refrigerant sent to the use-side unit 40 is heat-exchanged with air in the use-side heat exchanger 42 and condensed to become a high-pressure liquid refrigerant. The high-pressure liquid refrigerant is sent to the heat source side unit 20 via the liquid side refrigerant communication pipe 12 and the liquid side closing valve 26.

  In the heat source side unit 20, when the high-pressure liquid refrigerant passes through the expansion mechanism 24, the pressure is reduced according to the valve opening degree of the expansion mechanism 24. The refrigerant that has passed through the expansion mechanism 24 flows into the heat source side heat exchanger 23. The low-pressure gas-liquid two-phase refrigerant that has flowed into the heat source side heat exchanger 23 is heat-exchanged with the air supplied by the heat source side fan 35 and is evaporated to become a low pressure gas refrigerant. This low-pressure gas refrigerant is again sucked into the compressor 21 via the four-way switching valve 22. At that time, the refrigerant is sent from the four-way switching valve 22 to the compressor 21 via the refrigerant storage tank 50 and the gas-liquid separator 28.

(3-3) Oil Return Operation The control device 15 determines the timing for performing the oil return operation based on, for example, the timer 16a (see FIG. 7) of the heat source side control unit 16 in order to periodically perform the oil return operation. To do. The heat source side control unit 16 measures the time from the start of operation, and when a predetermined time set in advance elapses, the control device 15 switches to control for performing the oil return operation.

  The above-described cooling operation or heating operation is a steady operation, and as shown in FIG. 5, the liquid level of the liquid refrigerant in the refrigerant storage tank 50 during the cooling operation or heating operation is below the liquid level LLs. The oil return operation is an unsteady operation, and as shown in FIG. 6, when the operation condition is changed by the control device 15, the liquid level of the liquid refrigerant in the refrigerant storage tank 50 rises. Specifically, under the control of the control device 15, the liquid refrigerant in the refrigerant storage tank 50 rises to the liquid level LLa, and the liquid refrigerant level is above the position of the oil return hole 52b and the suction port 52a. It will be in a state below the position. As a result, the oil return hole 52b faces the oil-rich layer between the liquid level LLL and the liquid level LLb, and a large amount of refrigerating machine oil is discharged to the gas-liquid separator 28 while reducing the return of the liquid refrigerant. 52 can be sent.

  In order to increase the liquid level of the refrigerant storage tank 50, the control device 15 performs the following control, for example. The oil-rich layer and the refrigerant-rich layer as shown in FIG. 6 are separated from the oil-rich layer and the refrigerant-rich layer, for example, when the refrigerant is R32, mainly because the environment temperature of the heat source side unit 20 is low. The operation control will be described. At the time of heating, the user uses the remote controller (not shown) to instruct the user-side control unit 17 to perform the heating operation. Therefore, the air conditioning apparatus 10 starts the heating operation immediately after starting. When the timer 16a of the heat source side control unit 16 reaches a predetermined time after the heating operation starts, the control device 15 stops the heating operation and switches to the oil return operation. In the heating operation, the opening degree of the expansion mechanism 24 is adjusted so that the refrigerant subcooling degree at the outlet of the use side heat exchanger 42 becomes a predetermined supercooling degree target value. In the oil return operation, the expansion mechanism 24 is used during the heating operation. The predetermined target value for the degree of supercooling is changed to a small value. Here, a predetermined supercooling degree target value during heating is referred to as a heating supercooling degree target value Th, a predetermined supercooling degree target value during oil return operation is referred to as an oil return supercooling degree target value To, and Th It is assumed that the relationship> To is established.

  Since the oil return supercooling degree target value To is smaller than the heating supercooling degree target value Th, the liquid refrigerant staying inside the use side heat exchanger 42 is smaller in the oil return operation than in the heating operation. . Therefore, the liquid refrigerant that can no longer stay in the use-side heat exchanger 42 during the oil return operation is accumulated in another part of the refrigeration circuit 11, that is, in the refrigerant storage tank 50. During the oil return operation, the control device 15 switches the supercooling degree target value from the heating supercooling degree target value Th to the oil return supercooling degree target value To, so that the amount of liquid refrigerant in the refrigerant storage tank 50 increases and the liquid level changes. The liquid level LLs changes to the liquid level LLa. The controller 15 continues the oil return operation until the timer 16a measures the end of the oil return operation time after switching to the oil return supercooling degree target value To.

  During the oil return operation, the liquid refrigerant in the oil rich layer flows from the refrigerant storage tank 50 into the gas-liquid separator 28. Even in the gas-liquid separator 28, more refrigeration oil is contained above the stored liquid refrigerant. Therefore, an oil return hole is provided in the space of the gas-liquid separator 28 filled with the liquid refrigerant. By providing, more refrigerating machine oil can be returned from the gas-liquid separator 28 to the compressor 21.

(4) Modifications Although one embodiment of the present invention has been described above, the specific configuration is not limited to the above-described embodiment, and can be modified as follows, for example, without departing from the scope of the invention. It is.

(4-1) Modification A
In the above embodiment, the oil return operation during heating has been described. However, in the same manner as the oil return operation during heating, the operation conditions are changed by the control device 15 during cooling, and the liquid refrigerant level in the refrigerant storage tank 50 is changed. You can also increase the level.

  However, during the cooling operation, unlike the heating operation, the environmental temperature of the heat source side unit 20 is not lowered. For example, when R32 is used as the refrigerant, it is expected that the oil rich layer and the refrigerant rich layer are not separated into two layers. . Therefore, an oil return hole other than the oil return hole 52b may be provided in the outlet pipe 52 in the same manner as in the past so that oil return can be performed in the same manner as in the past during cooling operation.

  As shown in FIG. 8, an oil return hole 52c (another oil return hole) is always formed in the outlet pipe 52A of the refrigerant storage tank 50A according to Modification A. The constant oil return hole 52 c is a hole for returning the refrigeration oil stored together with the liquid refrigerant in the lower portion of the internal space S of the refrigerant storage tank 50 to the compressor 21. In the heating operation of the compressor 21 (compressor motor 21b), there is a concern that a large amount of liquid refrigerant is always returned to the compressor 21 through the oil return hole 52c, and the compressor 21 gets wet. The Therefore, the diameter of the oil return hole 52c is always made smaller than the oil return hole 52b used in the oil return operation so as to reduce the opening area, and smaller than the conventional general oil return hole. Is preferred.

(4-2) Modification B
In the modification A, the case where the control device 15 causes the oil return operation to be performed every time the timer 16a of the heat source side control unit 16 measures the elapse of the predetermined time after starting the heating operation during heating has been described. The condition for causing the oil return operation to be performed in 15 is not limited to such a case. For example, it can be added as a condition that the environmental temperature of the heat source side unit 20 including the compressor 21, that is, the temperature around the refrigerant storage tank 50A is equal to or lower than a predetermined temperature.

  For example, when R32 is used as the refrigerant and the temperature at which the refrigerant-rich layer and the oil-rich layer are separated into two layers is a predetermined temperature, the temperature around the refrigerant storage tank 50A becomes equal to or lower than the predetermined temperature as shown in FIG. A state appears. If the refrigerant stored in the refrigerant storage tank 50A is not separated into two layers, the oil return may be performed through the regular oil return hole 52c shown in FIG.

  Therefore, when the environmental temperature sensor 34 detects that the environmental temperature has become equal to or lower than the predetermined temperature, the control device 15 measures the time elapsed since the timer 16a became equal to or lower than the predetermined temperature. First, when it is detected that the environmental temperature sensor 34 is equal to or lower than a predetermined temperature when the air conditioner 10 is started, an oil return operation is performed. Monitoring of the environmental temperature by the environmental temperature sensor 34 starts again every time a predetermined time has elapsed since the start of the heating operation. Thereafter, the oil return operation is performed every time a predetermined time elapses while the environmental temperature is equal to or lower than the predetermined temperature. Thereby, since oil return can be performed using an oil rich layer, oil return can be performed quickly. Moreover, it is possible to prevent the liquid refrigerant from returning to the compressor 21 by returning the oil using the oil-rich layer.

(4-3) Modification C
In the above embodiment, the gas-liquid separator 28 is provided at the rear stage of the refrigerant storage tank 50, but the gas-liquid separator 28 may be removed.

(5) Features The air-conditioning apparatus 10 described in the above embodiment includes a compressor 21 and a heat source side heat exchanger 23 (evaporator) provided in the preceding stage of the compressor 21 in the heating operation, and the compressor When the refrigerating machine oil used in 21 and the refrigerant circulating through the refrigerating circuit 11 including the compressor 21 and the heat source side heat exchanger 23 are mixed, the lower refrigerant rich layer and the upper oil rich layer can be separated into two layers. It is a refrigeration system operated in the environment. The air conditioner 10 includes a refrigerant storage tank 50 (refrigerant container), an outlet pipe 52, and a control device 15. The refrigerant storage tank 50 is disposed between the heat source side heat exchanger 23 and the suction port of the compressor 21 and stores the refrigerant in the internal space S. The outlet pipe 52 is inserted into the internal space S of the refrigerant storage tank 50 in order to guide the refrigerant to the intake port of the compressor 21, and the intake port 52 a that sucks the gas refrigerant in the internal space S and the air conditioner 10 (refrigeration apparatus) stationary. And an oil return hole 52b formed at a position above the liquid level LLs of the refrigerant storage tank 50 during operation and below the suction port 52a.

  Whenever the timer 16a detects that a predetermined time has elapsed (when a predetermined condition is satisfied), the control device 15 causes the refrigerant to be above the position of the oil return hole 52b and below the position of the suction port 52a. An oil return operation is performed in which the liquid level of the storage tank 50 is forcibly raised to the liquid level LLa and the refrigeration oil near the liquid level LLa is moved to the suction port of the compressor 21 through the oil return hole 52b of the outlet pipe 52. Do it automatically.

  As a result, when the refrigerant and the refrigerating machine oil are separated into two layers in the refrigerant storage tank 50 and the lower refrigerant rich layer and the upper oil rich layer exist, the liquid level is compulsory to the liquid level LLa. And the oil-rich layer of the refrigerating machine oil can be returned to the suction port of the compressor 21 through the oil return hole 52b. Thereby, while suppressing the liquid refrigerant which returns to the compressor 21, many refrigeration oil can be returned to the compressor 21 rapidly.

  Further, the control device 15 can significantly raise the liquid level to the liquid level LLa by forcibly lowering the target value of the supercooling degree to the oil return supercooling degree target value To. The position can be provided sufficiently above the liquid level LLs during steady operation, and liquid refrigerant can be sufficiently prevented from entering the outlet pipe 52 from the oil return hole 52b during steady operation.

DESCRIPTION OF SYMBOLS 10 Air conditioning apparatus 50 Refrigerant storage tank 51 Inlet piping 52 Outlet piping 52a Suction port 52b Oil return hole S Internal space

JP 2004-26395 A

Claims (4)

A compressor (21) and an evaporator (23) provided in front of the compressor are provided, and refrigeration oil used in the compressor and a refrigeration circuit (11) including the compressor and the evaporator are circulated. A refrigeration system that is operated in an environment where two layers can be separated into a lower refrigerant-rich layer and an upper oil-rich layer when mixed with refrigerant,
A refrigerant container (50) disposed between the evaporator and the suction port of the compressor, and storing the refrigerant in an internal space;
The refrigerant that is inserted into the internal space of the refrigerant container to guide the refrigerant to the intake port of the compressor, and sucks the gaseous refrigerant in the internal space, and the refrigerant during steady operation of the refrigeration apparatus A pipe (52) having an oil return hole (52b) formed at a position above the liquid level of the container and below the suction port;
When a predetermined condition is satisfied, the liquid level of the refrigerant container is forcibly raised above the position of the oil return hole and below the position of the suction port, and the refrigeration near the liquid level is reached. A control device (15) for automatically performing an oil return operation for moving machine oil to the suction port of the compressor through the oil return hole of the pipe;
An expansion mechanism provided upstream of the evaporator in the refrigeration circuit; a condenser (42) provided upstream of the expansion mechanism and downstream of the compressor;
Further comprising
In order to forcibly raise the liquid level of the refrigerant container in the oil return operation, the control device is configured such that the degree of supercooling on the front side of the condenser is a target value of the degree of supercooling during steady operation of the refrigeration apparatus. A refrigeration system that controls to a lower value . The control device uses the predetermined condition that a predetermined time elapses from the start of operation of the refrigeration apparatus,
The refrigeration apparatus according to claim 1 . The pipe is formed at a predetermined position below a liquid level of the refrigerant container during steady operation of the refrigeration apparatus, and further includes another oil return hole (52c) having an opening area smaller than the oil return hole. Have
The refrigeration apparatus according to claim 1 or 2 . The control device uses the predetermined condition that a predetermined time elapses from the start of operation of the refrigeration apparatus and that the temperature around the refrigerant container is equal to or lower than a predetermined temperature.
The refrigeration apparatus according to claim 3 .

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