JP2012098000A - Refrigeration cycle apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power-recovery type refrigeration cycle apparatus that can be inexpensively manufactured and smoothly started.SOLUTION: The refrigeration cycle apparatus 100 includes: a refrigerant circuit 10 including a compressor 2, a radiator 3, positive displacement machinery 4 and a first evaporator 5; and an injection flow passage 50 including an expansion valve 8 and a second evaporator 7. The positive displacement machinery 4 sucks a refrigerant at a first pressure P1 from a suction port and sucks a refrigerant at a second pressure P2 from an injection port, expands the unified refrigerant of the above refrigerants to a third pressure P3, followed by overexpanding the refrigerant to the second pressure P2, re-compresses the overexpanded refrigerant together with the refrigerant at the second pressure P2 introduced from the injection port, to the third pressure P3, and then ejects the refrigerant through an ejection port.

Description

  The present invention relates to a refrigeration cycle apparatus using a positive displacement fluid machine.

  As described in Patent Document 1, a refrigeration cycle apparatus including an expander that recovers power from a refrigerant and a sub-compressor integrated with the expander is known. The outline of the refrigeration cycle apparatus described in Patent Document 1 will be described with reference to FIG.

  As shown in FIG. 9, the refrigeration cycle apparatus 500 described in Patent Document 1 includes a main compressor 501, a radiator 502, an expander 503, an evaporator 504, and a sub compressor 505. The sub compressor 505 is connected to the expander 505 by a shaft 506.

  The refrigerant is compressed by the main compressor 501 so as to be in a high temperature and high pressure state. The compressed refrigerant is cooled by the radiator 502 and then expanded by the expander 503. The expanded refrigerant changes from the liquid phase to the gas phase in the evaporator 504. The gas-phase refrigerant is compressed from a low pressure to an intermediate pressure by the sub-compressor 505 and sucked into the main compressor 501 again.

  The sub compressor 505 is driven by the power recovered by the expander 503 from the refrigerant. Since the sub compressor 505 preliminarily compresses the refrigerant on the upstream side of the main compressor 501, the load on the motor 501a that drives the main compressor 501 is reduced. As a result, the COP (coefficient of performance) of the refrigeration cycle apparatus 500 is improved.

JP 2004-325019 A

  The refrigeration cycle apparatus 500 shown in FIG. 9 requires two positive displacement fluid machines, which are an expander 503 and a sub-compressor 505, each sucking and discharging refrigerant. Therefore, the cost tends to be higher than that of a normal refrigeration cycle apparatus using an expansion valve. Further, since the expander 503 and the sub compressor 505 are not provided with a motor, the expander 503 and the sub compressor 505 may not be started smoothly.

  An object of the present invention is to provide a power recovery type refrigeration cycle apparatus that can be manufactured at low cost and can be started smoothly.

  That is, the present invention includes a compressor that compresses a refrigerant, a radiator that cools the refrigerant compressed by the compressor, a suction port, an injection port, and a discharge port, and is cooled by the radiator. And a refrigerant having a second pressure lower than the first pressure is sucked from the injection port, and a merged refrigerant combined with the refrigerant is combined with the first pressure and the refrigerant. After being expanded to a third pressure between the second pressures, the third pressure is overexpanded to the second pressure, and the overexpanded refrigerant is introduced together with the refrigerant having the second pressure introduced from the injection port. A positive displacement fluid machine that re-compresses to a pressure of 1 to discharge from the discharge port, a first evaporator that heats the refrigerant discharged from the positive displacement fluid machine, the radiator and the volume Branching from a flow path connecting the suction port of the fluid machine, an injection flow path connected to the injection port of the positive displacement fluid machine, and a refrigerant provided in the injection flow path and cooled by the radiator There is provided a refrigeration cycle apparatus comprising: an expansion valve that depressurizes to the second pressure; and a second evaporator that is provided in the injection flow path and heats the refrigerant depressurized by the expansion valve.

  According to the refrigeration cycle apparatus of the present invention, the following process is performed by the positive displacement fluid machine. First, the refrigerant is sucked separately from the suction port and the injection port (suction stroke). These refrigerants merge with each other to form a merged refrigerant, and then expand and overexpand (expansion / overexpansion stroke). Next, the refrigerant is again introduced from the injection flow path, and this refrigerant is mixed with the overexpanded refrigerant (injection process). Thereafter, the mixed refrigerant is recompressed using the power recovered when the refrigerant is expanded and overexpanded (recompression process). Since the pressure of the refrigerant can be increased by the recovered power, the load on the compressor is reduced. This improves the COP of the refrigeration cycle apparatus. Finally, the recompressed refrigerant is discharged (discharge process).

  In the present invention, in particular, the expansion / overexpansion stroke, the injection stroke, and the recompression stroke are performed as a series of strokes between the suction stroke and the discharge stroke. Therefore, according to the present invention, unlike the refrigeration cycle apparatus described in Patent Document 1, it is not necessary to separately configure the expander and the sub compressor. Therefore, according to the present invention, the functions of the conventional expander and sub-compressor can be realized with a simple structure. Thereby, the manufacturing cost of the refrigeration cycle apparatus can be suppressed.

  Furthermore, according to the present invention, not only injection but also inhalation is performed through the injection port. This means that at least one of a closed space where the suction port is opened and a closed space where the injection port is opened is always formed inside the positive displacement fluid machine as a working chamber for sucking the refrigerant. Therefore, if the high-pressure refrigerant is introduced to both the suction port and the injection port when the refrigeration cycle apparatus is started, the positive displacement fluid machine can be easily started regardless of the state of stoppage.

The block diagram of the refrigerating-cycle apparatus which concerns on one Embodiment of this invention. 1 is a longitudinal sectional view of a positive displacement fluid machine used in the refrigeration cycle apparatus shown in FIG. (A) is a cross-sectional view along the line IIIA-IIIA of the positive displacement fluid machine shown in FIG. 2, and (b) is a cross-sectional view along the line IIIB-IIIB of the positive displacement fluid machine shown in FIG. Operational principle diagram of positive displacement fluid machine shown in FIG. Graph showing the relationship between shaft rotation angle and working chamber volume Graph showing the relationship between shaft rotation angle and working chamber pressure PV diagram showing relationship between working chamber pressure and volume Flow chart of starting control of the refrigeration cycle apparatus shown in FIG. Configuration diagram of conventional refrigeration cycle equipment

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, the present invention is not limited to the embodiments described below. Each embodiment can be combined with each other without departing from the scope of the invention.

  FIG. 1 is a configuration diagram of a refrigeration cycle apparatus 100 according to an embodiment of the present invention. The refrigeration cycle apparatus 100 includes a refrigerant circuit 10 in which a compressor 2, a radiator 3, a positive displacement fluid machine 4, and a first evaporator 5 are connected in this order by flow paths 10a to 10d. The refrigeration cycle apparatus 100 includes an injection flow path 50 in which the expansion valve 8 and the second evaporator 7 are provided. The refrigerant circuit 10 and the injection flow path 50 are filled with a refrigerant such as hydrofluorocarbon and carbon dioxide as a working fluid. The refrigerant circuit 10 and the injection flow path 50 may be provided with other components such as an accumulator.

  The compressor 2 is driven by a motor 2a. The compressor 2 and the motor 2a are accommodated in the sealed container 2b. The compressor 2 compresses the refrigerant and discharges the compressed refrigerant to the internal space of the sealed container 2b. The compressor 2 is a positive displacement compressor such as a rotary compressor or a scroll compressor. The radiator 3 is a device for removing heat from the refrigerant compressed by the compressor 2, and typically includes a water-refrigerant heat exchanger or an air-refrigerant heat exchanger. The positive displacement fluid machine 4 has a function of expanding the refrigerant and a function of compressing the refrigerant. The first evaporator 5 is a device for applying heat to the refrigerant discharged from the positive displacement fluid machine 4, and typically includes an air-refrigerant heat exchanger.

  The flow path 10 a connects the compressor 2 and the radiator 3 so that the refrigerant compressed by the compressor 2 is supplied to the radiator 3. Specifically, the flow path 10a is comprised by the airtight container 2b and piping which one end opens in the airtight container 2b. The flow path 10b includes a radiator 3 and a later-described suction port 24 (see FIG. 2) of the positive displacement fluid machine 4 so that a part of the refrigerant flowing out of the radiator 3 is supplied to the positive displacement fluid machine 4. Is connected. The flow path 10c has a discharge port 27 (see FIG. 2), which will be described later, of the positive displacement fluid machine 4 and the first evaporator so that the refrigerant discharged from the positive displacement fluid machine 4 is supplied to the first evaporator 5. 5 is connected. The flow path 10 d connects the first evaporator 5 and the compressor 2 so that the refrigerant flowing out from the first evaporator 5 is supplied to the compressor 2.

  The injection flow path 50 branches from the flow path 10b and is connected to an injection port 30 (see FIG. 2) described later of the positive displacement fluid machine 4. Specifically, the injection flow path 50 includes an upper flow path 50a and a lower flow path 50b. The upper flow path 50 a is in contact with the flow path 10 b and the second evaporator 7 so that a part of the refrigerant flowing out of the radiator 3 is supplied to the second evaporator 7. An expansion valve 8 is disposed in the upper flow path 50a. The lower flow path 50b connects the second evaporator 7 and the injection port 30 of the positive displacement fluid machine 4 so that the refrigerant flowing out of the second evaporator 7 is supplied (suctioned or injected) to the positive displacement fluid machine 4. Connected.

  The expansion valve 8 is a valve whose opening degree can be changed, for example, an electric expansion valve. The expansion valve 8 depressurizes the refrigerant having the first pressure P1 that has flowed out of the radiator 3 to a second pressure P2 that is lower than the first pressure P1. The refrigerant is decompressed by the expansion valve 8 and then flows into the second evaporator 7. The second evaporator 7 is a device for applying heat to the refrigerant decompressed by the expansion valve 8 and is typically composed of an air-refrigerant heat exchanger.

  The first evaporator 5 and the second evaporator 7 are arranged on the flow path of the heat medium so that the heat medium (for example, air) cooled by the first evaporator 5 is further cooled by the second evaporator 7. ing. The direction indicated by arrow A in FIG. 1 is the flow direction of the heat medium. Since the refrigerant having the third pressure P3 between the first pressure P1 and the second pressure P2 is discharged from the positive displacement fluid machine 4, the temperature of the refrigerant in the first evaporator 5 is the second evaporator 7. Higher than the temperature of the refrigerant. Accordingly, as shown in FIG. 1, when the first evaporator 5 is disposed upstream of the flow path of the heat medium and the second evaporator 7 is disposed downstream, the heat medium (air), the refrigerant, As if to form a counter flow. Thereby, the heat exchange efficiency between the refrigerant and the heat medium in the evaporators 5 and 7 is improved. Further, since the refrigerant flowing out of the second evaporator 7 is boosted by the positive displacement fluid machine 4, the COP of the refrigeration cycle apparatus 100 is improved.

  The refrigeration cycle apparatus 100 further includes a controller 102. The controller 102 controls the motor 2 a that drives the compressor 2 and the expansion valve 8. The controller 102 is typically composed of a microcomputer having an internal memory and a CPU. When an instruction to start the operation of the refrigeration cycle apparatus 100 (for example, turning on the start switch) is given to the controller 102, a predetermined control program stored in the internal memory of the controller 102 is executed by the CPU. The predetermined control program includes a program related to activation control described later with reference to FIG.

  The refrigeration cycle apparatus 100 further includes an activation detector 104 for detecting the activation of the positive displacement fluid machine 4. The controller 102 switches the control method of the refrigeration cycle apparatus 100 from start control to normal control based on the detection result of the start detector 104. In the activation control, the expansion valve 8 is fully opened so that the high-pressure (first pressure P1) refrigerant is guided to the positive displacement fluid machine 4 through the injection flow path 50. Thereby, the positive displacement fluid machine 4 can be started smoothly. After the positive displacement fluid machine 4 is started, the expansion valve 8 is closed to a predetermined opening degree so that a low-pressure (second pressure P2) refrigerant is guided to the positive displacement fluid machine 4 through the injection flow path 50 according to normal control. Details of the activation detector 104 will be described later.

  First, the basic configuration of the refrigeration cycle apparatus 100 and the specific configuration of the positive displacement fluid machine 4 that can establish the basic operation will be described. Thereafter, start-up control of the refrigeration cycle apparatus 100 will be described.

  The compressor 2 sucks in the refrigerant and compresses the sucked refrigerant. The compressed refrigerant is cooled by the radiator 3 while maintaining a high pressure. In the middle of flowing through the flow path 10b, the cooled refrigerant is distributed into a part that flows through the flow path 10b (DC component) and a part that flows through the injection flow path 50 (divided part). Part of the cooled refrigerant (DC component) is directly sucked into the positive displacement fluid machine 4 through the flow path 10b. The refrigerant sucked into the positive displacement fluid machine 4 is decompressed to an intermediate pressure (third pressure P3) by the positive displacement fluid machine 4 and becomes a gas-liquid two-phase. The refrigerant discharged from the positive displacement fluid machine 4 flows into the first evaporator 5 through the flow path 10c. The refrigerant flowing into the first evaporator 5 is heated by the first evaporator 5 and then sucked into the compressor 2 through the flow path 10d. On the other hand, the remaining portion (divided flow) of the refrigerant cooled by the radiator 3 is reduced to a low pressure by the expansion valve 8 and changed into a gas-liquid two-phase, and then supplied to the second evaporator 7 through the upper flow path 50a. The refrigerant that has flowed into the second evaporator 7 is heated by the second evaporator 7 and then supplied to the positive displacement fluid machine 4 through the lower flow path 50b. The refrigerant supplied to the positive displacement fluid machine 4 is sucked and injected into the positive displacement fluid machine 4 and is increased to an intermediate pressure. The gas refrigerant whose pressure has been increased to the intermediate pressure is again sucked into the compressor 2 through the first evaporator 5. By raising the intake refrigerant of the compressor 2 to an intermediate pressure, the load on the compressor 2 is reduced, and thereby the COP of the refrigeration cycle apparatus 100 is improved.

  The cycle specified in each of the above stages is equivalent to a so-called “ejector cycle”. An ejector cycle well known to those skilled in the art uses an “ejector” which is a type of non-displacement fluid machine. On the other hand, according to the refrigeration cycle apparatus 100 of the present embodiment, a cycle equivalent to an ejector cycle can be constructed by using the positive displacement fluid machine 4. Specifically, as shown in FIGS. 5 and 6, the positive displacement fluid machine 4 is configured to execute an intake stroke, an expansion / overexpansion stroke, an injection stroke, a recompression stroke, and a discharge stroke.

  FIG. 2 is a longitudinal sectional view of the positive displacement fluid machine 4 shown in FIG. 3A and 3B are cross-sectional views of the positive displacement fluid machine 4 taken along lines IIIA-IIIA and IIIB-IIIB, respectively. The positive displacement fluid machine 4 is configured as a two-stage rotary fluid machine and is accommodated in a sealed container 23. Lubricating oil is stored inside the sealed container 23.

  The positive displacement fluid machine 4 includes an upstream rotary mechanism 4 a and a downstream rotary mechanism 4 b that are connected to each other by a shaft 15. In the present embodiment, the axial direction of the shaft 15 is a vertical direction, and the downstream rotary mechanism 4b is located above the upstream rotary mechanism 4a. However, the downstream rotary mechanism 4b may be positioned below the upstream rotary mechanism 4a, and the axial direction of the shaft 15 may be a horizontal direction. Further, the positive displacement fluid machine 4 includes a middle plate 25 disposed between the upstream rotary mechanism 4a and the downstream rotary mechanism 4b, a lower bearing 18 disposed below the upstream rotary mechanism 4a, and a downstream rotary. And an upper bearing 19 disposed above the mechanism 4b.

  The upstream rotary mechanism 4 a includes a first cylinder 11, a first piston 13 and a first vane 20, and the downstream rotary mechanism 4 b includes a second cylinder 12, a second piston 14 and a second vane 21.

  As shown in FIG. 2, the shaft 15 has a first eccentric portion 15a and a second eccentric portion 15b. Each of the first eccentric portion 15a and the second eccentric portion 15b protrudes outward in the radial direction. The shaft 15 penetrates through the first cylinder 11 and the second cylinder 12 and is rotatably supported by the lower bearing 18 and the upper bearing 19. The rotation axis of the shaft 15 coincides with each center of the first cylinder 11 and the second cylinder 12. The first cylinder 11 is closed by a lower bearing 18 and an intermediate plate 25, and the second cylinder 12 is closed by an intermediate plate 25 and an upper bearing 19.

  As shown in FIG. 3A, the first piston 13 has a ring shape in plan view, and forms a crescent-shaped first space 16 between itself and the first cylinder 11. Are disposed in the first cylinder 11. Inside the first cylinder 11, the first piston 13 is attached to the first eccentric portion 15 a of the shaft 15. A first vane groove 40 is formed in the first cylinder 11, and the first vane 20 is inserted into the first vane groove 40 so as to be slidable. The first vane 20 partitions the first space 16 along the circumferential direction of the first piston 13. Thereby, the 1st suction space 16a and the 1st discharge space 16b are formed in the inside of the 1st cylinder 11 (refer to Drawing 4).

  As shown in FIG. 3B, the second piston 14 has a ring shape in plan view, and forms a crescent-shaped second space 17 between itself and the second cylinder 12. Is disposed in the second cylinder 12. Inside the second cylinder 12, the second piston 14 is attached to the second eccentric portion 15b of the shaft 15. A second vane groove 41 is formed in the second cylinder 12, and the second vane 21 is inserted into the second vane groove 41 so as to be slidable. The second vane 21 partitions the second space 17 along the circumferential direction of the second piston 14. As a result, a second suction space 17 a and a second discharge space 17 b are formed inside the second cylinder 12.

  The second space 17 has a volume that is larger than the volume of the first space 16. Specifically, in the present embodiment, the second cylinder 12 has a thickness that is greater than the thickness of the first cylinder 11. Further, the second cylinder 12 has an inner diameter larger than the inner diameter of the first cylinder 11. The dimensions of each component are appropriately adjusted so that the second space 17 has a volume larger than the volume of the first space 16.

  As shown in FIGS. 3A and 3B, a first spring 42 is disposed behind the first vane 20, and a second spring 43 is disposed behind the second vane 21. Yes. The first spring 42 and the second spring 43 push the first vane 20 and the second vane 21 toward the center of the shaft 15, respectively. Lubricating oil stored in the closed container 23 is supplied to the first vane groove 40 and the second vane groove 41. In addition, the 1st piston 13 and the 1st vane 20 may be comprised by the single component, what is called a swing piston. Further, the first vane 20 may be engaged with the first piston 13. The same applies to the second piston 14 and the second vane 21.

  In the present embodiment, the protruding direction (eccentric direction) of the first eccentric portion 15a is deviated from the rotating direction of the shaft 15 by about 180 degrees with respect to the protruding direction (eccentric direction) of the second eccentric portion 15b. In the axial direction of the shaft 15, the position where the first vane 20 is disposed coincides with the position where the second vane 21 is disposed. Accordingly, the first rotational position of the shaft 15 when the first vane 20 is retracted most radially outward (that is, when the first piston 13 is located at the top dead center), the second vane 21 is most radially outward. It is displaced by about 180 degrees from the second rotational position of the shaft 15 when it is located (that is, the second piston 14 is located at the top dead center).

  However, in order to shift the first rotation position and the second rotation position, the protruding direction of the first eccentric portion 15a and the protruding direction of the second eccentric portion 15b are made the same, and the arrangement position of the first vane 20 and the second The arrangement position of the vane 21 may be shifted. Further, the deviation angle between the first rotational position and the second rotational position is not necessarily 180 degrees, but the angle at which the shaft 15 rotates from the first rotational position to the second rotational position (the point A in FIG. 5). The phase difference at point L) is preferably in the range of 30 to 270 degrees. More preferably, the angle at which the shaft 15 rotates from the first rotation position to the second rotation position is in the range of 45 to 180 degrees.

  As shown in FIG. 2, the positive displacement fluid machine 4 further includes a suction port 24, a discharge port 27, and an injection port 30. In the present embodiment, the suction port 24 is provided in the lower bearing 19, and the discharge port 27 is provided in the upper bearing 19. However, the suction port 24 may be provided in the first cylinder 11, for example, and the discharge port 19 may be provided in the second cylinder 12, for example.

  The suction port 24 is formed to open to the first suction space 16a in the vicinity of the first vane 20 (for example, within a range from the first vane 20 to 40 degrees in the rotation direction of the shaft 15). Thereby, the refrigerant can be supplied to the first suction space 16 a through the suction port 24. A suction pipe 22 constituting a part of the flow path 10 b is connected to the suction port 24 through the sealed container 23. The discharge port 27 is formed so as to open to the second discharge space 17b in the vicinity of the second vane 21 (for example, within a range from the second vane 21 to 40 degrees in the direction opposite to the rotation direction of the shaft 15). . Thereby, the refrigerant can be discharged from the second discharge space 17 b through the discharge port 27. A discharge pipe 26 constituting a part of the flow path 10 c is connected to the discharge port 27 through the sealed container 23. Further, the discharge port 27 is provided with a discharge valve 28 (a check valve) that prevents the refrigerant from flowing backward from the flow path 10c to the second discharge space 17b. The discharge valve 28 is typically a reed valve made of a thin metal plate. When the pressure in the second discharge space 17b exceeds the pressure inside the discharge pipe 26 (pressure in the flow path 10c), the discharge valve 28 opens. When the pressure in the second discharge space 17b is equal to or lower than the pressure inside the discharge pipe 26, the discharge valve 28 is closed.

  The intermediate plate 25 is provided with a communication passage 25a that guides the refrigerant from the first discharge space 16b to the second suction space 17a or the second discharge space 17b. In the present embodiment, the communication passage 25 a passes through the intermediate plate 25 obliquely with respect to the axial direction of the shaft 15. However, as described above, the communication path 25a can be made parallel to the axial direction of the shaft 15 by changing the protruding direction of the eccentric portions 15a and 15b and the arrangement position of the vanes 20 and 21. An upstream end 25b, which is an opening on the lower side of the communication path 25a, is disposed in the vicinity of the first vane 20 (for example, within a range from the first vane 20 to 40 degrees in the direction opposite to the rotation direction of the shaft 15). . Further, the upstream end 25b of the communication passage 25a has an arc shape that is completely closed by the first piston 13 when the first piston 13 is located at the top dead center. For this reason, the upstream end 25b of the communication path 25a is closed only at the moment when the shaft 15 passes through the first rotation position, and opens to the first discharge space 16b during other periods.

  On the other hand, the downstream end 25c, which is the upper opening of the communication passage 25a, opens into the second discharge space 17b before the shaft 15 passes through the first rotation position, and after the shaft 15 passes through the first rotation position. 2 It is configured to open to the suction space 17a. In the present embodiment, the downstream end 25 c of the communication path 25 a is disposed at a position substantially opposite to the discharge port 26 with the rotation axis of the shaft 15 interposed therebetween. For example, the center of the downstream end 25 c of the communication path 25 a may be located at a position away from the center line of the second vane 21 by about 160 to 180 degrees in the rotation direction of the shaft 15. Further, the downstream end 25c of the communication passage 25a is completely blocked by the second piston 14 when the shaft 15 is in the first rotational position (in this embodiment, when the second piston 14 is located at the bottom dead center). It has such an arc shape. For this reason, the shaft 15 is closed only at the moment when it passes through the first rotational position, and opens to the second discharge space 17b or the second suction space 17a during the other period.

  That is, the continuous space constituted by the first discharge space 16b, the communication passage 25a and the second suction space 17a, and the continuous space constituted by the first discharge space 16b, the communication passage 25a and the second discharge space 17b are shown in FIG. As shown in FIG. 4, a working chamber whose volume changes continuously is formed. Since the volume V2 of the second space 17 is larger than the volume V1 of the first space 16, the volume of the working chamber gradually increases from the first rotation position (360 degrees in FIG. 5), and the second rotation position ( In FIG. 5, the maximum is in the vicinity of 540 degrees), and then gradually decreases to the first rotational position (720 degrees in FIG. 5). Note that the timing at which the volume of the working chamber becomes maximum depends on the relationship between the volume V1 of the first space 16 and the volume V2 of the second space 17 and the deviation angle between the first rotation position and the second rotation position. It is earlier than the second rotation position or coincides with the second rotation position. The expansion / overexpansion stroke and the injection stroke are performed while the volume of the working chamber is increased, and the recompression stroke and a part of the discharge stroke are performed while the volume of the working chamber is decreased. Thereafter, the working chamber is constituted by the second discharge space 17b, and the remainder of the discharge stroke is performed. Further, in the suction stroke before the expansion / over-expansion stroke, the first suction space 176a and the second suction space 17a each constitute a working chamber. Thus, the “working chamber” means a space that holds the refrigerant from suction to discharge.

In particular, in this embodiment, the ratio (V3 / V1) of the maximum volume V3 of the working chamber to the volume V1 of the first space 16 is such that the refrigerant sucked into the positive displacement fluid machine 4 is in the first discharge space 16b, the communication path. It is adjusted to a value that allows expansion and overexpansion in the working chamber constituted by 25a and the second suction space 17a. That is, the volume V2 of the second space 17 is much larger than the volume V1. Specifically, the volume ratio (V3 / V1) is approximately the ratio of the refrigerant volume flow rate V _SC at the inlet of the compressor 2 to the refrigerant volume flow rate V _{GC at} the outlet of the radiator 3 (V _SC / V _GC ). Designed to be equal.

  The injection port 30 is formed at a position where the refrigerant can be supplied to the second suction space 17a. Specifically, an injection port 30 is formed in the second cylinder 12. However, the injection port 30 may be formed in the upper bearing 19, for example. The injection port 30 is disposed between the second vane 21 and the downstream end 25c of the communication path 25a in the rotation direction of the shaft 15. An injection pipe 29 that constitutes a part of the lower flow path 50 b of the injection flow path 50 is connected to the injection port 30 through the hermetic container 23. In addition, the injection port 30 is provided with a check valve 31 for preventing the refrigerant from flowing backward from the second suction space 17a or the second discharge space 17b to the injection flow path 50. The check valve 31 is typically a reed valve made of a thin metal plate.

  Specifically, the second cylinder 12 is provided with a recess 30 a that faces the second space 17. The injection port 30 is open to the recess 30a, and a check valve 31 is fixed to the recess 30a so that the injection port 30 can be opened and closed. The check valve 31 opens when the pressure in the second suction space 17a falls below the pressure inside the injection pipe 29 (pressure in the injection flow path 50). When the pressure in the second suction space 17a and the second discharge space 17b is equal to or higher than the pressure inside the injection pipe 29, the check valve 31 is closed.

  Hereinafter, in the present embodiment, the first rotation position of the shaft 15 when the first piston 13 is located at the top dead center is defined as a “reference position” in which the rotation angle of the shaft 15 is 0 degrees.

  The refrigerant does not flow into the second space 17 through the injection port 30 unless the pressure in the second space 17 is lower than the pressure inside the injection pipe 29. Therefore, the position of the injection port 30 is not particularly limited. However, in order to apply a driving force to the second piston 14 at a small rotation angle from the reference position with a high-pressure refrigerant guided from the injection port 30 at the time of startup, the injection port 30 is positioned near the second vane 21 (for example, 45 Less). This is also for preventing the second suction space 17a from being evacuated because the downstream end 25c of the communication passage 25a is located away from the second vane 21.

  The opening area of the suction port 24, the opening area of the injection port 30, and the opening area of the discharge port 27 should be appropriately designed in consideration of the flow rate (volume flow rate) of the refrigerant passing through each port. In the refrigeration cycle apparatus 100, the volume flow rate of the refrigerant flowing through the lower flow path 50 b of the injection flow path 50 is very large because it is after passing through the second evaporator 7. That is, the volume flow rate of the refrigerant passing through the injection port 30 is very large. On the other hand, since the refrigerant passing through the suction port 24 is a gas-liquid two-phase, its volume flow rate is relatively small. Similarly, the volume flow rate of the refrigerant passing through the discharge port 27 is relatively small. Therefore, it is desirable to make the opening area of the injection port 30 larger than the opening area of the suction port 24 from the viewpoint of reducing pressure loss. Further, it is desirable that the opening area of the injection port 30 is larger than the opening area of the discharge port 27 from the viewpoint of reducing pressure loss.

  Next, the detailed operation of the positive displacement fluid machine 4 will be described with reference to FIGS. FIG. 4 is an operation principle diagram of the positive displacement fluid machine 4. The positions of the first piston 13 and the second piston 14 when the shaft 15 is rotated by 90 degrees are respectively shown in the upper left view, upper right view, lower right view, and lower left view of FIG. FIG. 5 is a graph showing the relationship between the rotation angle of the shaft from the reference position and the volume of the working chamber. FIG. 6 is a graph showing the relationship between the rotation angle of the shaft from the reference position and the pressure in the working chamber. FIG. 7 is a graph showing the relationship between the pressure and volume of the working chamber (refrigerant pressure and volume).

  As shown in the upper left diagram and the upper right diagram in FIG. 4, when the shaft 15 rotates from the 0 degree position (first rotational position) to the 90 degree position, the upstream rotary mechanism 4 a is adjacent to the suction port 24. A first suction space 16a is newly created. As a result, the refrigerant cooled by the radiator 3 is sucked into the first suction space 16a through the suction port 24 (suction stroke). As the shaft 15 rotates, the volume of the first suction space 16a increases. When the shaft 15 rotates 360 degrees, the volume of the first suction space 16a reaches the maximum volume (= volume V1 of the first space 16). Thereby, the suction stroke is completed.

  In FIG. 5, a line AB represents a change in the volume of the first suction space 16a in the suction stroke. The inhalation stroke ends at point B. In FIG. 6, the suction stroke is indicated by a line AB. The refrigerant sucked into the first suction space 16a in the suction stroke is a refrigerant cooled while maintaining a high pressure in the radiator 3, and has a first pressure P1.

  On the other hand, in the downstream rotary mechanism 4b, the second suction space 17a is generated from a position of 180 degrees (second rotational position). While the shaft 15 rotates from the position of 180 degrees to the position of 360 degrees, the downstream end 25c of the communication path 25a does not open to the second suction space 17a, so that the refrigerant is introduced into the second refrigerant space 17a only from the injection port 30. Inhaled (second inhalation stroke). In FIG. 5, a line LJ represents a change in the volume of the second suction space 17a in the second suction stroke. The second suction stroke ends at point J. In FIG. 6, the second suction stroke is indicated by a line LJ. The refrigerant sucked into the second suction space 17a in the second suction stroke is a low-pressure refrigerant heated by the second evaporator 7, and has a second pressure P2.

  When the shaft 15 passes through the position of 360 degrees, the first suction space 16a changes to the first discharge space 16b. The first discharge space 16b communicates with the second suction space 17a through the communication passage 25a. By this communication, the refrigerant in the first discharge space 16b (the refrigerant cooled while maintaining a high pressure in the radiator 3) and the refrigerant in the second suction space 17a (a low-pressure refrigerant heated in the second evaporator 7). And join. Due to this merging, the refrigerant changes in a stepwise manner to a refrigerant state having a pressure P ′ lower than that of the first discharge space 16b and higher than that of the second suction space 17a. In other words, the refrigerant in the first discharge space 16b expands into the second suction space 17a due to the pressure difference. Thereby, the check valve 31 is closed, and the supply of the refrigerant from the injection port 30 is stopped. 5 and 6, the state of the working chamber immediately after joining is indicated by a point B '.

  Next, as shown in the upper left, upper right, and lower right diagrams of FIG. 4, when the shaft 15 rotates from a 360 degree position to a 540 degree position, the first discharge space 16b, the communication passage 25a, and the second suction space One working chamber that does not communicate with either the suction port 24 or the discharge port 27 is formed by 17a. The merged refrigerant formed by the above merge expands to the third pressure P3 and further expands to the second pressure P2 in the working chamber as the shaft 15 rotates (expansion and overexpansion stroke). ).

  In the process of expansion and overexpansion, the refrigerant releases pressure energy. Pressure energy released from the refrigerant is converted into torque of the shaft 15 via the pistons 13 and 14. That is, the positive displacement fluid machine 4 recovers power from the refrigerant.

  On the other hand, when the refrigerant overexpands and the pressure in the working chamber falls below the second pressure P2, the check valve 31 opens again, and the refrigerant at the second pressure P2 is introduced from the injection port 30 into the second suction space 17a. Is done. Thereby, the refrigerant is prevented from overexpanding and the refrigerant supplied through the injection port 30 is mixed with the overexpanded refrigerant (injection process). The introduction of the refrigerant into the working chamber through the injection port 30 continues until the rotation angle of the shaft 15 reaches around 540 degrees. When the volume of the working chamber reaches the maximum, the injection stroke ends and the recompression stroke starts.

  In FIG. 5, the change in the volume of the first discharge space 16b in the expansion / overexpansion stroke and the injection stroke is indicated by a broken line BI. A change in the volume of the second suction space 17a is indicated by a broken line JM. A change in the volume of the working chamber constituted by the first discharge space 16b, the communication passage 25a, and the second suction space 17a is indicated by a line B'E. The expansion / overexpansion stroke to the injection stroke end at the point E, and the volume V3 of the working chamber at the point E is the volume of the second suction space 17a at the point M and the first discharge space 16b at the point I and the communication passage 25a. This is equivalent to the sum of the volumes.

  In FIG. 6, the expansion / overexpansion stroke and the injection stroke are indicated by a line B′CD and a line DE, respectively. The pressure of the refrigerant in the working chamber formed by the first discharge space 16b, the communication passage 25a, and the second suction space 17a decreases from the pressure P ′ at the start of the tension stroke as the shaft 15 rotates. As described above, the ratio (V3 / V1) of the maximum volume V3 of the working chamber to the volume V1 of the first space 16 is very large. Accordingly, when it is assumed that the injection port 30 does not exist, the broken line on the extension line of the line B′CD even after the pressure in the working chamber has decreased to the refrigerant pressure (second pressure P2) in the second evaporator 7. Decreases along DH. However, since the positive displacement fluid machine 4 used in the refrigeration cycle apparatus 100 of the present embodiment has the injection port 30, when the pressure in the working chamber decreases to the second pressure P2, the second evaporator passes through the injection port 30. The refrigerant having the second pressure P2 flowing out of the refrigerant 7 is supplied to the second suction space 17a. Therefore, the pressure in the working chamber stops decreasing, and the refrigerant having the second pressure P2 continues to be supplied to the working chamber until the volume of the working chamber reaches the volume specified by the point E in FIG.

  Thereafter, when the shaft 15 passes through the position of 540 degrees, the second suction space 17a changes to the second discharge space 17b. The first discharge space 16b communicates with the second discharge space 17b through the communication passage 25a.

  As shown in the lower right view, lower left view and upper left view of FIG. 4, when the shaft 15 rotates from a position of 540 degrees to a position of 720 degrees, the first discharge space 16b, the communication passage 25a, and the second discharge space 17b are configured. A discharge port 27 is opened in the working chamber. However, as described with reference to FIG. 2, the discharge port 27 is provided with the discharge valve 28. Therefore, the refrigerant is compressed in the working chamber until the pressure in the working chamber exceeds the pressure inside the discharge pipe 26, that is, the suction pressure of the compressor 2 (recompression process).

  In order to compress the refrigerant in the recompression stroke, the power recovered from the refrigerant in the expansion / overexpansion stroke is used. According to the present embodiment, the expansion / overexpansion stroke starts from the time when the first discharge space 16b and the second suction space 17a communicate with each other via the communication passage 25a (the timing in the upper left diagram of FIG. 4). The process continues until the pressure in the space 17a coincides with the second pressure P2 in the injection flow path 50. The recompression stroke starts from the point in time when the sum of the spaces of the first discharge space 16b and the second suction space 17a via the communication passage 25a is maximized (the lower right diagram in FIG. 4 or a timing slightly before that). The process continues until the pressure in the second discharge space 17b matches the third pressure P3 in the flow path 10c. That is, the recompression stroke is performed by the inertial force of the shaft 15 rotated by the expansion / overexpansion stroke.

  The positive displacement fluid machine 4 is designed so that at least a part of the period during which the expansion / overexpansion stroke is performed overlaps the period during which the recompression stroke is performed during the period in which the shaft 15 rotates once. It is preferable. According to such a configuration, the power recovered from the refrigerant in the expansion / overexpansion stroke is consumed as it is as energy for compressing the refrigerant in the recompression stroke, so that torque unevenness of the shaft 15 hardly occurs. This contributes to stable operation of the positive displacement fluid machine 4.

  When the shaft 15 passes through the position of 720 degrees, the communication between the second discharge space 17b and the communication passage 25a is released, and the working chamber is formed only by the second discharge space 17b. Although the recompression process is performed after the volume of the working chamber is maximized, it is formed by the first discharge space 16b, the communication passage 25a and the second discharge space 17b, or only by the second discharge space 17b. When the pressure in the working chamber exceeds the pressure inside the discharge pipe 26, the discharge valve 28 opens. As a result, the recompression stroke is completed, and the refrigerant is discharged from the working chamber to the discharge pipe 26 through the discharge port 27 (discharge stroke). As the shaft 15 rotates, the volume of the working chamber decreases. When the shaft 15 rotates to a position of 900 degrees, the second discharge space 17b disappears. Thereby, the discharge stroke is completed.

  In FIG. 5, the change in the volume of the second discharge space 17b in the recompression stroke and the discharge stroke is indicated by a line EG. In FIG. 6, the recompression stroke and the discharge stroke are indicated by lines EF and FG, respectively. Immediately after the end of the injection stroke, the pressure P2 of the refrigerant is lower than the pressure P3 inside the discharge pipe 26. At this time, the discharge valve 28 is closed. As the volume of the working chamber decreases, the refrigerant is recompressed to the pressure P3. Thereafter, the pressure is balanced before and after the discharge valve 28 to open the discharge valve 28, and the refrigerant having the pressure P2 is discharged from the second discharge space 17b to the discharge pipe 26. At point G, the discharge stroke ends.

  FIG. 7 is a PV diagram showing the relationship between the pressure and volume of the working chamber. The suction stroke is indicated by line AB, the second suction stroke is indicated by line LJ, the expansion / overexpansion stroke is indicated by line B'CD, the injection stroke is indicated by line DE, the recompression stroke is indicated by line EF, and the discharge stroke is indicated by line FCG. In the positive displacement fluid machine 4, the recovered energy, work required for recompression, and various losses are balanced. Therefore, the positive displacement fluid machine 4 rotates autonomously without using a motor or the like. Energy corresponding to the area of the region surrounded by the point ABB'CNG is recovered from the refrigerant, and using the recovered energy, work corresponding to the area of the region surrounded by the point CDEF and the point LJNG is performed on the refrigerant. .

  As described above, according to the present embodiment, the expansion / overexpansion stroke, the injection stroke, and the recompression stroke are performed as a series of strokes between the suction stroke and the discharge stroke. Therefore, according to the present embodiment, unlike the refrigeration cycle apparatus described in Patent Document 1, it is not necessary to separately provide an expander and a sub-compressor, and the positive displacement fluid machine 4 having a simple structure is used. Each of the above steps can be performed. The number of parts of the positive displacement fluid machine 4 is smaller than when the expander and the sub compressor are provided separately. Therefore, the manufacturing cost of the refrigeration cycle apparatus 100 can be suppressed.

  Further, since the check valve 31 is provided in the injection port 30, it is possible to prevent the refrigerant from flowing back from the second discharge space 17b to the injection port 30 in the recompression stroke and the discharge stroke. This contributes to improving the efficiency of the positive displacement fluid machine 4.

  Moreover, since the discharge valve 28 is provided in the discharge port 27, the reverse flow of the refrigerant | coolant at the time of recompression can be prevented, and the work for recompressing and discharging a refrigerant | coolant can be reduced.

  The refrigeration cycle apparatus 100 of the present embodiment can be suitably used for a hot water heater or a hot water heater. For the purpose of hot water supply and hot water heating, there is no need to switch between cooling and heating such as an air conditioner. That is, since components such as a four-way valve can be omitted, further cost reduction can be expected.

  A supercritical refrigerant typified by carbon dioxide has a large difference between high pressure and low pressure in the refrigeration cycle. Specifically, the difference between the suction pressure (first pressure P1) and the discharge pressure (third pressure P3) in the positive displacement fluid machine 4 is large. Therefore, the power that can be recovered by the positive displacement fluid machine 4 is also large. Therefore, carbon dioxide is suitable as a refrigerant for the refrigeration cycle apparatus 100. However, the type of the refrigerant is not particularly limited, and natural refrigerants other than carbon dioxide, alternative CFCs such as R410A, and low GWP (Global Warming Potential) refrigerants such as R1234yf can be used.

  By using the positive displacement fluid machine 4 in the refrigeration cycle apparatus 100 as means for recovering power from the refrigerant, the recovered power can be used as part of the compression work. Since the difference between the suction pressure and the discharge pressure of the compressor 2 is reduced, the load on the compressor 2 is reduced and the COP of the refrigeration cycle apparatus 100 is improved. However, there is a possibility that the positive displacement fluid machine 4 described in the present embodiment can be used for apparatuses other than the refrigeration cycle apparatus.

  Next, activation control that the controller 102 should perform when the refrigeration cycle apparatus 100 is activated will be described. In the startup control, the pressure of the refrigerant supplied to the positive displacement fluid machine 4 through the injection flow path 50 is changed to the first pressure P1 (that is, the refrigerant pressure at the outlet of the compressor 2) instead of the second pressure P2. It is the control to make the pressure equal to. FIG. 8 is a flowchart of the start-up control of the refrigeration cycle apparatus. The controller 102 performs normal operation after executing the startup control shown in FIG. When the refrigeration cycle apparatus 100 is stopped, the expansion valve 8 is open, and the pressure of the refrigerant in the refrigerant circuit 10 and the injection flow path 50 is substantially uniform.

  When an activation command is input in step S11, a control signal is transmitted to the actuator of the expansion valve 8 so that the expansion valve 8 is fully opened. (Step S12) The “start command” means a command to start the operation of the refrigeration cycle apparatus 100, and is generated when, for example, the start switch of the refrigeration cycle apparatus 100 is turned on.

  Next, power supply to the motor 2a is started and the compressor 2 is started (step S13). The compressor 2 sucks the refrigerant present in the flow path 10d, the first evaporator 5, and the flow path 10c. In response to the activation of the compressor 2, a fan or a pump for flowing a fluid (air or water) to be heat exchanged with the refrigerant to the radiator 3 is activated. Thereby, the excessive raise of the high voltage | pressure of a cycle can be prevented.

  When the compressor 2 starts to suck in the refrigerant, the pressure in the flow path 10d and the like decreases. On the other hand, since the refrigerant compressed by the compressor 2 is discharged, the flow path 10a, the radiator 3 and the flow path 10b in the refrigerant circuit 10, the upper flow path 50a in the injection flow path 50, the second evaporator 7 and The pressure rises in the lower flow path 50b. For this reason, the pressure in the second suction space 17 a of the positive displacement fluid machine 4 also increases through the injection port 30, and a high pressure is applied to the second piston 14. Since the surface area of the second piston 14 is sufficiently larger than the surface area of the first piston 13, the torque for rotating the shaft 15 increases by increasing the pressure in the second suction space 17a. As a result, the positive displacement fluid machine 4 can be easily activated independently.

  In the positive displacement fluid machine 4 of the present embodiment, the top dead center timings of the first piston 13 and the second piston 14 are shifted by about 180 degrees. Therefore, both the first piston 13 and the second piston 14 do not stop at the top dead center at the same time, and at least one of the differential pressure is generated between the upstream side and the downstream side of the positive displacement fluid machine 4. Rotational torque is generated by the piston. Therefore, the high-pressure refrigerant is guided to the suction port 24 and the injection port 30 as in the present embodiment, so that the positive displacement fluid machine 4 can be stopped regardless of the rotation angle position at the end of the operation. It can be activated reliably.

  When it is detected through the activation detector 104 that the positive displacement fluid machine 4 has been activated (YES in step S14), the opening of the expansion valve 8 is adjusted to an opening suitable for normal operation (step S15). After the operation by the start control (start operation) shown in FIG. In normal operation, the low-pressure refrigerant from the second evaporator 7 is guided to the positive displacement fluid machine 4 through the lower flow path 50 b of the injection flow path 50.

  On the other hand, when the positive displacement fluid machine 4 is not started (NO in step S14), the compressor 2 is stopped (step S16). Thereby, it can prevent that the pressure of the flow path 10a, the heat radiator 3, and the flow path 10b increases too much, and can ensure the reliability of the refrigerating-cycle apparatus 100. FIG.

  As described above, the controller 102 executes the control of the expansion valve 6 as the start control. Thereby, the positive displacement fluid machine 4 can be started smoothly. In addition, when switching the control method of the refrigerating cycle apparatus 100 from starting control to normal control, it is preferable to close the expansion valve 8 stepwise (gradually). In this way, load fluctuation when the recompression stroke is performed in the positive displacement fluid machine 4 can be reduced. Since the positive displacement fluid machine 4 can be prevented from stalling due to sudden load fluctuations, the start-up operation can be smoothly switched to the normal operation.

  In order to stop the operation of the refrigeration cycle apparatus 100, for example, the rotational speed of the compressor 2 is gradually decreased. After the compressor 2 is stopped, the refrigerant moves through the compressor 2 and the positive displacement fluid machine 4 over a sufficient time. Therefore, the pressure difference in the refrigerant circuit 10 and the injection flow path 50 is naturally eliminated, and the pressure in the refrigerant circuit 10 and the injection flow path 50 becomes substantially uniform and stable. Thereby, the positive displacement fluid machine 4 also stops naturally.

  Next, the activation detector 104 will be described in detail. As the activation detector 104, a temperature detector, a pressure detector, or the like can be used. The activation detector 104 as a temperature detector includes a temperature detection element such as a thermocouple or a thermistor, for example, and includes an inlet temperature Ti of the positive displacement fluid machine 4, an outlet temperature To of the positive displacement fluid machine 4, and an inlet temperature Ti. A difference ΔT with respect to the outlet temperature To can be detected. The activation detector 104 as a pressure detector includes, for example, a piezoelectric element, and calculates an inlet pressure Pi of the positive displacement fluid machine 4, an outlet pressure Po of the positive displacement fluid machine 4, and a difference ΔP between the inlet pressure Pi and the outlet pressure Po. It can be detected. Further, the activation detector 104 may include a timer that measures an elapsed time from the activation point of the compressor 2. Such a timer can also be provided by the function of the controller 102. That is, the controller 102 itself can serve as the activation detector 104. Further, a contact-type or non-contact-type displacement sensor that detects the rotation of the shaft 15 of the positive displacement fluid machine 4, for example, an encoder, may be provided as the activation detector 104.

  The method for determining whether or not the positive displacement fluid machine 4 is activated differs depending on the type of the activation detector 104 as follows. According to the method described below, the activation of the positive displacement fluid machine 4 can be easily detected.

When the pressure detector that detects the outlet pressure of the positive displacement fluid machine 4 (pressure of the refrigerant at the outlet of the positive displacement fluid machine 4) Po is used as the activation detector 104, it is obtained experimentally or theoretically, for example. A threshold value P _th is preset in the controller 102. A value obtained by subtracting the outlet pressure Po _n (n: natural number) detected by the pressure detector at a time point that is back by unit time from the current outlet pressure Pon _{+ 1} detected by the pressure detector is a predetermined threshold value P _th . When it exceeds, activation of the positive displacement fluid machine 4 is detected. The controller 102 may be set with a single threshold value P _th , or may be set with a plurality of threshold values P _th associated with the outside air temperature or the like. In the latter case, the controller 102 selects the optimum threshold value P _th based on the outside air temperature or the like. The same applies to other threshold values described below.

In the period after the compressor 2 is started and before the positive displacement fluid machine 4 is started, the outlet pressure Po of the positive displacement fluid machine 4 generally decreases monotonously. When the positive displacement fluid machine 4 starts to move, the outlet pressure Po increases. By capturing this pressure change, the activation of the positive displacement fluid machine 4 can be detected. Specifically, the outlet pressure Po is detected every unit time and stored in the memory of the controller 102. And the outlet pressure Po _n stored in the memory in the most recent past, comparing current and an outlet pressure Po n _{+ 1.} If the current outlet pressure Po n _{+ 1} exceeds recent past the outlet pressure Po _n more than a predetermined value, it can be determined that displacement type fluid machine 4 is started. In other words, it can be determined that the positive displacement fluid machine 4 has started when (Po _{n + 1} −Po _n )> P _th is satisfied. The “unit time” can be arbitrarily set within a time period sufficient for capturing a sudden change in the outlet pressure Po, for example, in the range of 1 to 5 seconds.

It is also possible to use the outlet temperature To instead of the outlet pressure Po. That is, a value obtained by subtracting the outlet temperature To _n (n: natural number) detected by the temperature detector at a time point that is back by unit time from the current outlet temperature To _{n + 1} detected by the temperature detector is a predetermined threshold T. _When it exceeds _th , activation of the positive displacement fluid machine 4 is detected.

  The pressures in the flow path 10c, the gas-liquid separator 5 and the flow path 10d are equal. Therefore, the pressure in the flow path (flow path 10c, first evaporator 5 and flow path 10d) from the outlet of the positive displacement fluid machine 4 to the inlet of the compressor 2 is used as the outlet pressure Po of the positive displacement fluid machine 4. it can. Similarly, the temperature in the flow path from the outlet of the positive displacement fluid machine 4 to the inlet of the compressor 2 can be used as the outlet temperature To of the positive displacement fluid machine 4.

When a timer is used as the activation detector 104, for example, a threshold time t ₁ obtained experimentally or theoretically is preset in the controller 102. If the time t measured by the timer exceeds the threshold time t _1, activation of volume-type fluid machine 4 is detected.

The “threshold time t ₁ ” is described in the activation control program to be executed by the controller 102. For example, the time from when the compressor 2 is started to when the positive displacement fluid machine 4 is started is actually measured under various operating conditions (outside air temperature or the like). In all operating conditions, a time during which it can be determined that the positive displacement fluid machine 4 is reliably started can be set as the “threshold time t ₁ ”. Theoretically, a model of the refrigeration cycle apparatus 100 is constructed, and a time necessary and sufficient for starting the positive displacement fluid machine 4 is calculated. The calculated time can be set as “threshold time t ₁ ”.

  The refrigeration cycle apparatus of the present invention can be used for a water heater, a hot water heater, an air conditioner, and the like.

2 compressor 3 radiator 4 positive displacement fluid machine 4a upstream rotary mechanism 4b downstream rotary mechanism 5 first evaporator 7 second evaporator 8 expansion valves 10a to 10g flow path 11 first cylinder 12 second cylinder 13 first Piston 14 Second piston 15 Shaft 16 First space 16a First suction space 16b First discharge space 17 Second space 17a Second suction space 17b Second discharge space 20 First vane 21 Second vane 24 Suction port 25a Passage 27 Discharge port 30 Injection port 50 Injection flow path 100 Refrigeration cycle apparatus 102 Controller 104 Start-up detector

Claims (6)

A compressor for compressing the refrigerant;
A radiator for cooling the refrigerant compressed by the compressor;
A suction port, an injection port, and a discharge port are provided, the first pressure refrigerant cooled by the radiator is sucked from the suction port, and the second pressure refrigerant lower than the first pressure is sucked from the injection port. The combined refrigerant, which was sucked from the port and merged with the refrigerant, was expanded to a third pressure between the first pressure and the second pressure, and then overexpanded to the second pressure. A positive displacement fluid machine that recompresses the refrigerant together with the refrigerant having the second pressure introduced from the injection port to the third pressure and discharges the refrigerant from the discharge port;
A first evaporator for heating the refrigerant discharged from the positive displacement fluid machine;
An injection flow path branched from a flow path connecting the radiator and the suction port of the positive displacement fluid machine and connected to the injection port of the positive displacement fluid machine;
An expansion valve that is provided in the injection flow path and depressurizes the refrigerant cooled by the radiator to the second pressure;
A refrigeration cycle apparatus comprising: a second evaporator that is provided in the injection flow path and heats the refrigerant decompressed by the expansion valve. The positive displacement fluid machine includes an upstream rotary mechanism including a first space partitioned by a first vane into a first suction space and a first discharge space, and a second suction space and a second discharge by a second vane. A downstream rotary mechanism including a second space partitioned into a space, and a shaft connecting the upstream rotary mechanism and the downstream rotary mechanism,
The first rotational position of the shaft when the first vane is retracted most radially outward is shifted from the second rotational position of the shaft when the second vane is retracted most radially outward. Item 2. The refrigeration cycle apparatus according to Item 1.   The refrigeration cycle apparatus according to claim 2, wherein an angle at which the shaft rotates from the first rotation position to the second rotation position is in a range of 30 to 270 degrees. The positive displacement fluid machine further includes a middle plate disposed between the upstream rotary mechanism and the downstream rotary mechanism, and the middle plate includes the second suction space or the second suction space. A communication path for guiding the refrigerant to the second discharge space is formed;
The downstream end of the communication path opens into the second discharge space before the shaft passes through the first rotation position, and opens into the second suction space after the shaft passes through the first rotation position. The refrigeration cycle apparatus according to claim 2 or 3, wherein the refrigeration cycle apparatus is configured to.   5. The injection port according to claim 4, wherein the injection port is disposed between the second vane and a downstream end of the communication path in the rotation direction of the shaft so as to supply a refrigerant to the second suction space. Refrigeration cycle equipment.   The refrigeration cycle apparatus according to any one of claims 1 to 5, further comprising a controller that fully opens the opening of the expansion valve when the refrigeration cycle apparatus is activated.

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