JP2012093017A - Refrigerating cycle device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power-recovery type refrigeration cycle device having a simple structure.SOLUTION: The refrigeration cycle device 100 includes a compressor 2, a heat radiator 3, a positive displacement fluid machine 4, an evaporator 7, and an injection flow path 10f. The positive displacement fluid machine 4 executes the steps of: (i) sucking a refrigerant; (ii) expanding and overexpanding the sucked refrigerant; (iii) supplying the refrigerant through an injection port 30 to a work chamber, and mixing the supplied refrigerant with the excessively expanded refrigerant; (iv) recompressing the mixed refrigerant by using power recovered from the refrigerant in the step (ii); and (v) discharging the recompressed refrigerant from the work chamber. The injection port 30 is provided to a position to be able to prevent occurrence of the excessive overexpansion in the step (ii).

Description

  The present invention relates to a refrigeration cycle apparatus.

  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. 17, 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 503 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 upstream of the main compressor 501, the load on the motor 501a of 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 JP 2006-046257 A

  The refrigeration cycle apparatus 500 shown in FIG. 17 requires two positive displacement fluid machines, that is, an expander 503 and a sub compressor 505. Therefore, the cost tends to be higher than that of a normal refrigeration cycle apparatus using an expansion valve. As described in Patent Document 2, an expander configured to transmit recovered power directly to a compressor is also known, but its structure is complicated and inevitably increases in cost.

  An object of the present invention is to provide a power recovery type refrigeration cycle apparatus having a simple structure.

In order to achieve the above object, in Japanese Patent Application No. 2010-143046 (filing date: June 23, 2010) preceding the present application, the present inventors:
A compressor for compressing the refrigerant;
A radiator for cooling the refrigerant compressed by the compressor;
An operating chamber and an injection port; (i) a step of sucking the refrigerant cooled by the radiator into the working chamber at a first pressure; and (ii) a refrigerant sucked in the working chamber in the first chamber. A step of expanding to a second pressure lower than the second pressure and further overexpanding to a third pressure lower than the second pressure; and (iii) applying the third pressure to the working chamber through the injection port. A step of supplying the refrigerant having, and mixing the supplied refrigerant with the overexpanded refrigerant, and (iv) using the power recovered from the refrigerant in the step (ii), and mixing the refrigerant to the second pressure A positive displacement fluid machine configured to perform a step of recompressing in the working chamber; and (v) a step of discharging the recompressed refrigerant from the working chamber;
An evaporator for heating the refrigerant discharged from the positive displacement fluid machine;
An injection flow path for supplying the refrigerant having the third pressure to the injection port of the positive displacement fluid machine;
A refrigeration cycle apparatus comprising:

  According to the basic configuration, in the step (ii), the refrigerant having the first pressure is expanded to the second pressure lower than the first pressure, and further increased to the third pressure lower than the second pressure. Inflate. When the pressure in the working chamber decreases to the third pressure, the refrigerant having the third pressure is supplied to the working chamber through the injection port (injection stroke). However, if the injection port does not open to the working chamber when the pressure in the working chamber drops to the third pressure, the overexpansion stroke proceeds excessively without moving to the injection stroke. As a result, energy recovery is reduced. Therefore, the present inventors propose a configuration for suppressing a decrease in energy recovery amount due to excessive overexpansion.

That is, the present invention
With the above basic configuration,
The ratio (Ve / V1) of the volume Ve of the working chamber in the expansion stroke or the overexpansion stroke to the suction volume V1 of the working chamber is the density of the refrigerant at the first pressure with respect to the density ρ3 of the refrigerant at the third pressure. Provided is a refrigeration cycle apparatus in which the injection port opens into the working chamber when the ratio is equal to or smaller than the ratio of ρ1 (ρ1 / ρ3).

In addition, the location of the injection port is a problem. Therefore, the present invention provides
With the above basic configuration,
The positive displacement fluid machine comprises:
A cylinder,
A piston disposed inside the cylinder so as to form a space between itself and the cylinder;
A vane that divides the space into a suction space and a discharge space;
A suction port for supplying a refrigerant to the suction space;
A discharge port for discharging refrigerant from the discharge space;
A closing member that closes an end surface of the cylinder,
Provided is a refrigeration cycle apparatus in which the injection port is provided in the closing member.

  According to the refrigeration cycle apparatus of the present invention, the following process is performed by the positive displacement fluid machine. First, the refrigerant sucked into the working chamber is expanded and overexpanded. Next, a refrigerant having the same pressure as the overexpanded refrigerant is injected into the working chamber through the injection flow path, and the injected refrigerant and the overexpanded refrigerant are mixed in the working chamber. Furthermore, the mixed refrigerant is recompressed using the power recovered when the refrigerant is expanded and overexpanded. 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.

  In the present invention, in particular, the stroke (ii), the stroke (iii), and the stroke (iv) 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 above steps can be performed using a positive displacement fluid machine having a simpler structure. Thereby, the manufacturing cost of the refrigeration cycle apparatus can be suppressed.

  Furthermore, in the present invention, when the ratio (Ve / V1) is equal to or smaller than the ratio (ρ1 / ρ3), the injection port opens into the working chamber. Thus, the injection stroke (stroke (iii)) starts immediately when the pressure of the refrigerant in the working chamber drops to the third pressure. That is, since it can prevent that a refrigerant | coolant overexpands too much, the reduction | decrease of the energy recovery amount based on excessive overexpansion can be suppressed.

The block diagram of the refrigerating-cycle apparatus which concerns on 1st 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. Cross-sectional view along the line XX of the positive displacement fluid machine shown in FIG. Cross-sectional view along Y-Y line of positive displacement fluid machine shown in FIG. Schematic showing the positional relationship between the communication hole and the injection port Enlarged view of check valve to prevent refrigerant backflow Cross-sectional view along the Z-Z line of the positive displacement fluid machine shown in FIG. Perspective view of valve stop 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 the relationship between working chamber volume and pressure Graph showing the relationship between working chamber volume and working chamber pressure in the event of excessive overexpansion The block diagram of the refrigerating-cycle apparatus which concerns on 2nd Embodiment of this invention. Longitudinal sectional view of positive displacement fluid machine according to modification FIG. 14 is a cross-sectional view taken along the line W-W of the positive displacement fluid machine. Operational principle diagram of the positive displacement fluid machine 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.

(First embodiment)
FIG. 1 is a configuration diagram of a refrigeration cycle apparatus according to the first embodiment. The refrigeration cycle apparatus 100 includes a compressor 2, a radiator 3, a positive displacement fluid machine 4, a gas-liquid separator 5, an expansion valve 6, and an evaporator 7. These components are connected to each other by flow paths 10 a to 10 f so as to form the refrigerant circuit 10. The flow paths 10a to 10f are typically constituted by refrigerant pipes. The refrigerant circuit 10 is filled with a refrigerant such as hydrofluorocarbon or carbon dioxide as a working fluid. Other components such as an accumulator may be provided in the flow paths 10a to 10f.

  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 gas-liquid separator 5 is a device for separating the refrigerant discharged from the positive displacement fluid machine 4 into a gas refrigerant and a liquid refrigerant. The gas-liquid separator 5 is provided with a liquid refrigerant outlet, a refrigerant inlet, and a gas refrigerant outlet. The expansion valve 6 is a valve whose opening degree can be changed, for example, an electric expansion valve. The evaporator 7 is a device for applying heat to the liquid refrigerant separated by the gas-liquid separator 5, 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. The flow path 10 b connects the radiator 3 and the positive displacement fluid machine 4 so that the refrigerant flowing out of the radiator 3 is supplied to the positive displacement fluid machine 4. The flow path 10 c connects the positive displacement fluid machine 4 and the gas-liquid separator 5 so that the refrigerant discharged from the positive displacement fluid machine 4 is supplied to the vapor-liquid separator 5. The flow path 10 d connects the gas-liquid separator 5 and the compressor 2 so that the gas refrigerant separated by the gas-liquid separator 5 is supplied to the compressor 2. The flow path 10 e connects the gas-liquid separator 5 and the evaporator 7 so that the liquid refrigerant separated by the gas-liquid separator 5 is supplied to the evaporator 7. The flow path 10f connects the evaporator 7 and the positive displacement fluid machine 4 so that the gas refrigerant flowing out of the evaporator 7 is supplied (injected) to the positive displacement fluid machine 4. The cycle described in this specification can be formed by the components such as the compressor 2 and the flow paths 10a to 10f. Hereinafter, the channel 10f is referred to as an “injection channel 10f”.

  In the present embodiment, the expansion valve 6 (pressure reducing valve) is provided on the flow path 10e connecting the gas-liquid separator 5 and the evaporator 7. According to the expansion valve 6, it is possible to reduce the pressure of the refrigerant separated by the gas-liquid separator 5 and heated by the evaporator 7. Thereby, the refrigerant that has flowed out of the evaporator 7 can be smoothly sucked into the positive displacement fluid machine 4 through the injection flow path 10f.

  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. The cooled refrigerant is decompressed to an intermediate pressure by the positive displacement fluid machine 4 and becomes a gas-liquid two-phase. The gas-liquid two-phase refrigerant flows into the gas-liquid separator 5 and is separated into a gas refrigerant and a liquid refrigerant. The gas refrigerant is sucked into the compressor 2. The liquid refrigerant is decompressed by the expansion valve 6 and supplied to the evaporator 7. In the evaporator 7, the refrigerant is heated and evaporated. The gas refrigerant flowing out of the evaporator 7 is sucked into the positive displacement fluid machine 4 and preliminarily compressed to an intermediate pressure. The gas refrigerant compressed to the intermediate pressure is again sucked into the compressor 2 through the gas-liquid separator 5. By increasing the pressure of the refrigerant sucked in 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.

  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 XX and YY, respectively. The positive displacement fluid machine 4 includes a sealed container 23, a shaft 15, an upper bearing 18 (first closing member), a first cylinder 11, a first piston 13, a first vane 20, an intermediate plate 25, a second cylinder 12, and a second cylinder 12. It has a piston 14, a second vane 21, and a lower bearing 19 (second closing member). The positive displacement fluid machine 4 is configured as a two-stage rotary fluid machine. Each component such as a cylinder is accommodated in a sealed container 23.

  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 an upper bearing 18 and a lower bearing 19. The rotation axis of the shaft 15 coincides with each center of the first cylinder 11 and the second cylinder 12. The second cylinder 12 is arranged concentrically with respect to the first cylinder 11, and is separated from the first cylinder 11 by an intermediate plate 25. The first cylinder 11 is closed by the upper bearing 18 and the middle plate 25, and the second cylinder 12 is closed by the middle plate 25 and the lower bearing 19.

  As shown in FIG. 3A, the first piston 13 has a ring shape in a plan view, and the first piston 13 forms a crescent-shaped first space 16 between itself and the first cylinder 11. It is arranged in the 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 is attached to the first vane groove 40 so that the first vane 20 can slide. The first vane 20 partitions the first space 16 along the circumferential direction of the first piston 13. As a result, a first suction space 16 a and a first discharge space 16 b are formed inside the first cylinder 11.

  As shown in FIG. 3B, the second piston 14 has a ring shape in plan view, and the second piston 14 forms a crescent-shaped second space 17 between itself and the second cylinder 12. It is arranged in the 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 is attached to the second vane groove 41 so that the second vane 21 can slide. 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.

  With respect to the rotation direction of the shaft 15, the protruding direction of the first eccentric portion 15a coincides with the protruding direction of the second eccentric portion 15b. With respect to the rotation direction of the shaft 15, the angular position where the first vane 20 is disposed coincides with the angular position where the second vane 21 is disposed. Therefore, the timing of the top dead center of the first piston 13 coincides with the timing of the top dead center of the second piston 14. The “timing of the top dead center of the piston” means the timing at which the vane is pushed into the vane groove to the maximum by the piston.

  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. 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.

  As shown in FIG. 2, the positive displacement fluid machine 4 further includes a suction pipe 22, a suction port 24, a discharge pipe 26, a discharge port 27, an injection port 30, and an injection suction pipe 29. Through the suction port 24, the refrigerant can be supplied to the first space 16 (specifically, the first suction space 16a). Through the discharge port 27, the refrigerant can be discharged from the second space 17 (specifically, the second discharge space 17b). A suction pipe 22 and a discharge pipe 26 are connected to the suction port 24 and the discharge port 27, respectively. The suction pipe 22 constitutes a part of the flow path 10b in the refrigerant circuit 10 (FIG. 1). The discharge pipe 26 constitutes a part of the flow path 10 c in the refrigerant circuit 10. 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 suction port 24 and the discharge port 27 are formed in the upper bearing 18 and the lower bearing 19, respectively. However, the suction port 24 may be formed in the first cylinder 11, and the discharge port 19 may be formed in the second cylinder 12.

  The intermediate plate 25 is provided with a communication hole 25a (communication flow path). The communication hole 25a penetrates the intermediate plate 25 in the thickness direction. The first discharge space 16b of the first cylinder 11 communicates with the second suction space 17a of the second cylinder 12 through the communication hole 25a. Thereby, the 1st discharge space 16b, the communicating hole 25a, and the 2nd suction space 17a can function as one working chamber. Since the volume of the second space 17 is larger than the volume of the first space 16, the refrigerant confined in the first discharge space 16b, the communication hole 25a, and the second suction space 17a expands while rotating the shaft 15. .

  In the positive displacement fluid machine 4, the “working chamber” is formed by the first space 16, the second space 17, and the communication hole 25 a. The working chamber expands the refrigerant by increasing the volume and compresses the refrigerant by decreasing the volume. Specifically, the first suction space 16a functions as a working chamber for sucking refrigerant, the first discharge space 16b, the communication hole 25a, and the second suction space 17a function as working chambers for expanding and overexpanding the refrigerant, The two discharge spaces 17b function as working chambers for recompressing and discharging the refrigerant. The volume of the first space 16 coincides with the suction volume V1 of the working chamber. The volume of the second space 17 corresponds to the volume V2 of the working chamber at the start of the recompression stroke.

In particular, in the present embodiment, the ratio (V2 / V1) of the volume V2 of the second space 17 to the volume V1 of the first space 16 indicates that the refrigerant sucked into the positive displacement fluid machine 4 is the first discharge space 16b, It is adjusted to a value that allows expansion and overexpansion in the working chamber constituted by the communication hole 25a and the second suction space 17a. That is, the volume V2 is much larger than the volume V1. The volume ratio (V2 / V1) is, for example, approximately the ratio (V _SEP / V _GC ) of the refrigerant volume flow rate V _SEP at the inlet of the gas-liquid separator 5 to the refrigerant volume flow rate V _{GC at} the outlet of the radiator 3. Designed to be equal.

  In the present embodiment, the injection port 30 opens toward the second space 17. According to this configuration, the refrigerant (injection refrigerant) vaporized by the evaporator 7 is directly supplied to the second suction space 17a without passing through the communication hole 25a. Therefore, pressure loss that may occur when passing through the communication hole 25a can be avoided. Further, since the injection port 30 is provided in the lower bearing 19 and the suction port 24 is provided in the upper bearing 18, the injection port 30 is separated from the suction port 24. Therefore, it is possible to prevent the refrigerant (suction refrigerant) to be sucked into the first suction space 16a from being cooled by the injection refrigerant, that is, decrease in the enthalpy of the refrigerant in the suction port 24. This is advantageous for improving the power recovery efficiency. Furthermore, it is possible to prevent the injection refrigerant from being heated by the suction refrigerant, that is, the volumetric efficiency from being reduced due to expansion of the injection refrigerant. It is also possible to form the injection port 30 so as to open toward the first space 16 or the communication hole 25a.

  In the present embodiment, the upper bearing 18 closes the end surface of the first cylinder 11 at a position facing the intermediate plate 25. Further, the lower bearing 19 closes the end surface of the second cylinder 12 at a position facing the intermediate plate 25. The lower bearing 19 is provided with an injection port 30. When the lower bearing 19 is provided with the injection port 30, the injection port 30 can be opened and closed by the end face of the second piston 14, so that the sealing performance is improved and leakage of the refrigerant through the injection port 30 can be reduced. Furthermore, the dimension of the injection port 30 and the freedom of arrangement (design freedom) are also high. Note that the injection port 30 may be formed in the second cylinder 12.

As shown by a broken line in FIG. 3B, the communication hole 25 a has an opening facing the second cylinder 12. As shown in FIG. 4, it includes a rotation axis O of the shaft 15, and two virtual planes defines a first plane pair M ₁ in contact with the opening of the communication hole 25a. Wherein the rotation axis O of the shaft 15, and two virtual planes defines a second plane pair M ₂ in contact with the injection port 30. In the present embodiment, the angle range R ₁ sandwiched by the first plane pair M ₁ overlaps the angle range R ₂ sandwiched by the second plane pair M ₂ around the shaft 15. According to such a positional relationship, the injection port 30 opens (exposes) the second suction space 17a substantially simultaneously with the first discharge space 16b communicating with the second suction space 17a through the communication hole 25a. It becomes possible to guide the refrigerant to the space 17a. That is, the injection port 30 opens (exposes) into the second suction space 17a substantially simultaneously with the start of expansion of the suction refrigerant. As soon as the pressure in the second suction space 17a drops to the pressure in the injection flow path 10f, the refrigerant is supplied from the injection port 30 to the second suction space 17a. Therefore, excessive overexpansion can be prevented under a wide range of operating conditions.

  In the present embodiment, with respect to the rotation direction of the shaft 15, the position where the second vane 21 is disposed (the position of the second vane groove 41) is defined as a “reference position” having an angle of 0 degrees. Since the position where the first vane 20 is arranged matches the position where the second vane 21 is arranged, the position where the first vane 20 is arranged also coincides with the reference position.

  The suction port 24 is provided in a range of 0 to 40 degrees, for example. The communication hole 25a is provided in a range of 0 to 40 degrees, for example, when viewed from the second cylinder 12 side. The discharge port 27 is provided in the range of 320 to 360 degrees, for example.

  As can be understood from the positional relationship among the suction port 24, the communication hole 25a, and the injection port 30, the injection port 30 is connected to the suction port 24 via the working chamber (the first space 16, the communication hole 25a, and the second space 17). It is provided in the position which does not communicate with.

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 injection flow path 10f is very large. 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 in a liquid phase (alternative chlorofluorocarbon) or a supercritical state (CO ₂ ), its volume flow rate 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.

  As shown in FIG. 2, the lower bearing 19 is formed with an internal flow path 19 c that guides the refrigerant from the injection flow path 10 f (injection pipe 29) to the injection port 30. A check valve 34 is provided in the internal flow path 19c. The check valve 34 opens when the pressure in the second suction space 17a falls below the pressure in the injection flow path 10f (pressure in the injection suction pipe 29). When the pressure in the second suction space 17a is equal to or higher than the pressure in the injection flow path 10f, the check valve 34 is closed. In other words, the check valve 34 plays a role of preventing the reverse flow of the refrigerant from the second suction space 17a or the second discharge space 17b to the injection flow path 10f. In the present embodiment, since the injection port 30 is provided in the lower bearing 19, a space for arranging the check valve 34 can be secured in the lower bearing 19 relatively easily.

  As shown in FIGS. 2 and 5, in the present embodiment, the lower bearing 19 is configured by a first portion 19 a that is in contact with the second cylinder 12 and a second portion 19 b that is separated from the second cylinder 12. ing. In the first portion 19a, a recess 19g for arranging the check valve 34 is formed as a part of the internal flow path 19c.

  As shown in FIG. 5, the check valve 34 includes a valve port 33, a valve body 31, and a valve stop 32. The valve body 31 is made of, for example, a metal thin plate (reed valve), and a differential pressure between the pressure of the injection flow path 10f and the pressure of the second space 17 (working chamber) so as to open and close the valve port 33. Moved by. The valve stop 32 plays a role of limiting the movement of the valve main body 31. Specifically, the valve stop 32 has a support surface 32p that limits the amount of displacement (lift amount) of the valve body 31. The support surface 32p is configured by a gently curved surface. The valve stop 32 has a shape along the shape of the recess 19g so as to reduce the volume of the space from the valve port 33 to the injection port 30. In this embodiment, as shown in FIG. 7, the valve stop 32 has a shoe-like shape as a whole. The valve main body 31 and the valve stop 32 are fixed to the lower bearing 19 (second portion 19b) with bolts 35.

  As shown in FIG.5 and FIG.6, the valve stop 32 has a dimension a little smaller than the dimension of the recessed part 19g. A gap SH through which the refrigerant can flow is secured around the valve stop 32. By displacing the valve body 31 to the position indicated by the broken line in FIG. 5, the refrigerant can flow from the internal flow path 19 c to the second space 17 (working chamber) through the gap SH and the injection port 30. According to the valve stop 32, the volume of the gap SH between the recess 19g and the check valve 34 can be reduced to a necessary and sufficient volume while ensuring a sufficient movable range of the valve body 31.

  As shown in FIGS. 5 and 7, the position of the upper surface of the valve stop 32 matches the position of the top surface of the bolt 35 with respect to the axial direction of the bolt 35. The shape of the head of the bolt 35 follows the shape of the bolt hole formed in the valve stop 32. As shown in FIG. 6, the cross-sectional area (flow path area) of the gap SH around the valve stop 32 is equal to the cross-sectional area (flow path area) of the injection port 30. According to such a configuration, it is possible to reduce a pressure loss when the refrigerant flows through the gap SH while suppressing an increase in dead volume.

  Next, detailed operations of the positive displacement fluid machine will be described with reference to FIGS. FIG. 8 is an operation principle diagram of the positive displacement fluid machine. The upper left view, upper right view, lower right view, and lower left view of FIG. 8 show the positions of the first piston 13 and the second piston 14 when the shaft 15 is rotated by 90 degrees, respectively. FIG. 9 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. 10 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. 11 is a graph showing the relationship between the volume of the working chamber and the pressure (refrigerant pressure and volume).

  As shown in the upper left diagram and the upper right diagram in FIG. 8, when the shaft 15 rotates from the 0 degree position to the 90 degree position, the first cylinder 11 has a new first suction space 16 a adjacent to the suction port 24. To occur. 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 of the first space 16). Thereby, the suction stroke is completed.

  In FIG. 9, line AB represents a change in the volume of the first suction space 16a in the suction stroke. The suction stroke ends at the point B, and the volume V1 at the point B corresponds to the volume of the first space 16 of the first cylinder 11. In FIG. 10, 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 suction pressure P1 (first pressure).

  Next, as shown in the upper left diagram and the upper right diagram in FIG. 8, when the shaft 15 rotates from a position of 360 degrees to a position of 450 degrees, the first suction space 16a changes to the first discharge space 16b. In the second cylinder 12, a second suction space 17a is newly created adjacent to the communication hole 25a. The first discharge space 16b communicates with the second suction space 17a through the communication hole 25a. The first discharge space 16b, the communication hole 25a, and the second suction space 17a form one working chamber that is not in communication with any of the suction port 24 and the discharge port 27. As the shaft 15 rotates, the refrigerant expands to the discharge pressure P2 (second pressure) in the working chamber formed by the first discharge space 16b, the communication hole 25a, and the second suction space 17a (expansion stroke). .

  The amount of increase in the volume of the second suction space 17a when the shaft 15 is rotated by a unit angle is very large compared to the amount of decrease in the volume of the first discharge space 16b. Therefore, the refrigerant expands rapidly, and the pressure of the refrigerant is lower than the discharge pressure P2 when the shaft 15 occupies a position of 450 degrees. As the shaft 15 rotates, the refrigerant overexpands to a pressure P3 (third pressure) lower than the discharge pressure P2 (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.

  When the refrigerant overexpands and the pressure in the second suction space 17a falls below the pressure inside the injection suction pipe 29, that is, the evaporation pressure in the evaporator 7, the refrigerant overexpansion stops. At the same time, the refrigerant having the pressure P3 is supplied to the second suction space 17a through the injection port 30. In the second suction space 17a, the supplied refrigerant is mixed with the overexpanded refrigerant (injection stroke).

  Thereafter, as shown in the lower right diagram and the lower left diagram in FIG. 8, the refrigerant having the pressure P3 continues to be supplied to the second suction space 17a through the injection port 30 until the rotation angle of the shaft 15 reaches 720 degrees. As shown in the upper left diagram of FIG. 8, when the shaft 15 rotates to a position of 720 degrees, the volume of the second suction space 17a reaches the maximum volume (= volume of the second space 17). Thereby, the injection process ends.

  In FIG. 9, the change in the volume of the first discharge space 16b in the expansion stroke, the overexpansion stroke, and the injection stroke is indicated by a broken line BI. The change in the volume of the second suction space 17a is indicated by a broken line JE. A change in the volume of the working chamber constituted by the first discharge space 16b, the communication hole 25a, and the second suction space 17a is indicated by a line BE. The expansion stroke, the overexpansion stroke, and the injection stroke end at the point E, and the volume V2 at the point E corresponds to the volume of the second space 17 of the second cylinder 12.

  In FIG. 10, the expansion stroke, the overexpansion stroke, and the injection stroke are indicated by a line BC, a line CD, and a line DE, respectively. The pressure in the working chamber formed by the first discharge space 16b, the communication hole 25a, and the second suction space 17a decreases with the rotation of the shaft 15 from the pressure P1 at the start of the expansion stroke. As described above, the ratio (V2 / V1) of the volume V2 of the second space 17 to the volume V1 of the first space 16 is very large. Therefore, if it is assumed that the injection port 30 does not exist, the pressure in the working chamber decreases along the broken line DH on the extension line of the line BCD even after the pressure in the evaporator 7 decreases to the refrigerant pressure P3. 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 pressure P3, the pressure flowing out from the evaporator 7 through the injection port 30. The refrigerant of P3 is supplied to the second suction space 17a. Therefore, the pressure drop in the working chamber stops, and the refrigerant having the pressure P3 continues to be supplied to the working chamber until the volume of the working chamber reaches the volume V2 specified by the point E in FIG. Thereby, an expansion stroke, an overexpansion stroke, and an injection stroke are completed.

  Next, as shown in the upper left diagram and the upper right diagram in FIG. 8, when the shaft 15 rotates from the position of 720 degrees to the position of 810 degrees, the second suction space 17a changes to the second discharge space 17b. The discharge port 27 faces the second discharge space 17b. 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 second discharge space 17b until the pressure in the second discharge space 17b exceeds the pressure in the discharge pipe 26, that is, the suction pressure of the compressor 2 (recompression process). The refrigerant compressed in the second discharge space 17 b includes a fraction sucked into the positive displacement fluid machine 4 through the suction port 24 and a fraction sucked into the positive displacement fluid machine 4 through the injection port 30. It is.

  In order to compress the refrigerant in the recompression stroke, the power recovered from the refrigerant in the expansion stroke and the overexpansion stroke is used. As can be understood from the upper left view and the upper right view of FIG. 8, when the recompression stroke is performed in the second discharge space 17b, the newly generated second suction space 17a undergoes an expansion stroke and an overexpansion stroke. Yes. The power recovered from the refrigerant in the expansion stroke and the overexpansion stroke is consumed as energy for compressing the refrigerant in the recompression stroke.

  According to the present embodiment, in the expansion stroke and the overexpansion stroke, the pressure in the second suction space 17a is changed from the time when the first discharge space 16b and the second suction space 17a are communicated with each other through the communication hole 25a. Continue until a time point that coincides with the pressure P3 (third pressure) of 10f. In the recompression stroke, the pressure in the second discharge space 17b is changed to the pressure P2 (second pressure) of the flow path 10c from the time when the communication between the first discharge space 16b and the second suction space 17a through the communication hole 25a is cut off. Continue until a point in time that matches the pressure. In the period in which the shaft 15 rotates once, at least a part of the period in which the expansion stroke and the overexpansion stroke are performed overlaps the period in which the recompression stroke is performed. According to such a configuration, torque unevenness of the shaft 15 is unlikely to occur. This contributes to stable operation of the positive displacement fluid machine 4.

  When the pressure in the second discharge space 17b exceeds the pressure inside the discharge pipe 26, the discharge valve 28 opens. Thus, the refrigerant is discharged from the second discharge space 17b to the discharge pipe 26 through the discharge port 27 (discharge process). As the shaft 15 rotates, the volume of the second discharge space 17b decreases. When the shaft 15 rotates to a position of 1080 degrees, the second discharge space 17b disappears. Thereby, the discharge stroke is completed.

  In FIG. 9, 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. 10, the recompression stroke and the discharge stroke are indicated by lines EF and FG, respectively. Immediately after the end of the expansion stroke and the overexpansion stroke, the refrigerant pressure P3 is lower than the pressure P2 inside the discharge pipe 26. At this time, the discharge valve 28 is closed. As the volume of the second discharge space 17b decreases, the refrigerant is recompressed to the pressure P2. 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. 11 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 expansion stroke is indicated by line BC, the overexpansion stroke is indicated by line 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. The energy that the positive displacement fluid machine 4 recovers from the refrigerant corresponds to the area of the region surrounded by the point ABCDLG, and the work required to recompress the refrigerant after overexpansion is the area of the region surrounded by the point LDEFCG. Equivalent to. 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. Since the area surrounded by the point CDLG is common to the recovered energy and the work required for recompression, it can be offset. Eventually, energy corresponding to the area of the region surrounded by the point ABCG is recovered from the refrigerant, and using the recovered energy, work corresponding to the area of the region surrounded by the point CDEF is performed on the refrigerant.

  In this embodiment, the ratio (Ve / V1) of the working chamber volume Ve in the expansion stroke or overexpansion stroke to the suction volume V1 is the ratio of the refrigerant density ρ1 at the pressure P1 to the refrigerant density ρ3 at the pressure P3 (ρ1 / When equal to or smaller than ρ3), the injection port 30 opens into the working chamber. In this way, it is possible to prevent excessive overexpansion from occurring under conditions that contribute most to annual efficiency, so that the refrigeration cycle apparatus 100 can be operated with high efficiency. More specifically, the injection port 30 is provided in the range of 0 to 270 degrees (or 0 to 180 degrees), for example, with respect to the rotation direction of the shaft 15. The density ρ3 of the refrigerant means the density when the refrigerant sucked into the positive displacement fluid machine 4 at the pressure P1 and the density ρ1 is adiabatically expanded until the pressure P3 is reached.

When the volume of the working chamber (the first discharge space 16b, the communication passage 25a, and the second suction space 17a) at the time when the injection port 30 opens into the working chamber is V _i , the volume V _i is the point D in FIG. It is desirable to be equal to or smaller than the volume V _D. The reason will be described with reference to FIG. FIG. 12 is a graph showing the relationship between the volume of the working chamber and the pressure of the working chamber when V _i > V _D , in other words, when excessive overexpansion occurs.

  The refrigerant sucked into the positive displacement fluid machine 4 expands and overexpands as the working chamber volume increases, and reaches the pressure P3 (point D). Here, the point D is referred to as a “supercharging switching point”. The supercharging switching point is a point at which the magnitude relationship between the pressure in the working chamber and the pressure in the injection flow path 10f is switched. When the volume of the working chamber is smaller than the supercharging switching point, the pressure of the working chamber is higher than that of the injection flow path 10f, and when the volume of the working chamber is large, the pressure of the working chamber is lower than the pressure of the injection flow path 10f.

Therefore, when V _i > V _D , the refrigerant is not supplied from the injection port 30 to the working chamber even when the supercharging switching point is reached, and the volume of the working chamber continues to increase. That is, the overexpansion stroke proceeds excessively, and the pressure in the working chamber continues to decrease. As a result, as shown in FIG. 12, energy loss corresponding to the area of the region surrounded by the point DRS occurs. This loss is substantially zero when V _i ≦ V _D is satisfied.

The supercharging switching point varies depending on operating conditions. However, it is not always necessary to satisfy V _i ≦ V _D for all operating conditions. It can be designed to satisfy V _i ≦ V _D under at least one of all possible operating conditions, for example, the operating condition that contributes most to the annual operating efficiency of the refrigeration cycle apparatus 100. For example, when the refrigeration cycle apparatus 100 is applied to a heat pump hot water heater, a condition that contributes most to the annual efficiency is a winter condition.

  As described above, according to the present embodiment, the expansion stroke, the overexpansion 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 34 is provided adjacent to the injection port 30, it is possible to prevent the refrigerant from flowing back from the second discharge space 17b to the injection flow path 10f 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 work for recompressing and discharging the refrigerant can be reduced. When the discharge valve 28 is not provided, the second discharge from the discharge pipe 26 (flow path 10c) at the moment when the discharge port 27 faces the second discharge space 17b after the rotation angle of the shaft 15 passes the position of 720 degrees. There is a possibility that the refrigerant flows back into the space 17b. When the reverse flow of the refrigerant occurs, the recompression stroke and the discharge stroke are indicated by a line EKFG in FIG. 10 and a line EKFCG in FIG. That is, an extra work corresponding to the area of the region surrounded by the point EKF is required for recompression and ejection. By providing the discharge valve 28, this disadvantage can be avoided, so the work for recompressing and discharging the refrigerant can be reduced, and the efficiency of the positive displacement fluid machine 4 is also improved. Further, it is possible to prevent the generation of a plosive sound by directly connecting the suction pipe 26 filled with the refrigerant having the pressure P3 to the second discharge space 17b filled with the refrigerant having the pressure P2. Therefore, noise and vibration of the positive displacement fluid machine 4 can be suppressed.

  In the present embodiment, the positive displacement fluid machine 4 has a structure of a two-stage rotary fluid machine. The expansion stroke and the overexpansion stroke proceed in the working chamber constituted by the first discharge space 16b, the communication hole 25a and the second suction space 17a, and the recompression stroke and the discharge stroke proceed in the second discharge space 17b. That is, in the positive displacement fluid machine 4, the expansion stroke and the overexpansion stroke proceed simultaneously with the recompression stroke and the discharge stroke. Therefore, energy recovery from the refrigerant and compression work on the refrigerant can be performed simultaneously. When energy recovery and compression work are performed simultaneously, fluctuations in the rotational speed of the shaft 15 are reduced as compared with the case where these are performed alternately. Thereby, the positive displacement fluid machine 4 can be operated stably, and noise and vibration of the positive displacement fluid machine 4 are also reduced. Further, when the refrigerant circulation amount in the refrigerant circuit 10 is small, it is possible to prevent the shaft 15 from decelerating and stopping due to fluctuations in the rotation speed of the shaft 15.

  In the present embodiment, when the volume of the working chamber (volume of the second space 17) at the start of the recompression stroke is V2, the ratio of the volume V2 to the suction volume V1 (V2 / V1) is the second pressure. It is larger than the ratio (ρ1 / ρ2) of the density ρ1 of the refrigerant at the first pressure P1 to the density ρ2 of the refrigerant at P2. According to this configuration, it is possible to reliably cause overexpansion.

  In the present embodiment, the refrigerant to be supplied to the injection port 30 of the positive displacement fluid machine 4 through the injection flow path 10f is a gas refrigerant. Specifically, the evaporator 7 receives heat from a low-temperature side heat source (for example, air) and injects the refrigerant after evaporating from liquid to gas into the positive displacement fluid machine 4. Since the work of compressing the refrigerant (liquid refrigerant) that does not contribute to the heat energy absorption from the low-temperature side heat source in the positive displacement fluid machine 4 is reduced, the COP of the refrigeration cycle apparatus 100 is improved. Therefore, the opening degree of the expansion valve 6 (the expansion valve 45 in the second embodiment) is adjusted so that the refrigerant having a dryness of 1.0 or the superheated refrigerant (that is, only the gas refrigerant) is supplied to the injection port 30. It is preferable.

  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.

  When the refrigeration cycle apparatus 100 is used in a hot water heater or a hot water heater, there are the following advantages. When hot water is stored in a tank using nighttime power, the water heater usually performs rated operation. A hot water heater normally performs continuous operation. Since the room temperature becomes constant after a while after the activation, the load of the hot water heater is stabilized. Considering such an operation mode, the ratio of the volume flow rate of the refrigerant at the inlet of the gas-liquid separator 5 to the volume flow rate of the refrigerant at the outlet of the radiator 3 is substantially constant. Therefore, the ratio (V2 / V1) of the volume V2 of the second space 17 to the volume V1 of the first space 16 is easily matched with the ratio of the volume flow rate. Thereby, the effect of power recovery can be obtained more sufficiently.

  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 P1 and the discharge pressure P2 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. Of course, 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.

(Second Embodiment)
FIG. 13 is a configuration diagram of a refrigeration cycle apparatus according to the second embodiment. The refrigeration cycle apparatus 200 includes a compressor 2, a radiator 3, a positive displacement fluid machine 4, an expansion valve 45 (pressure reducing valve), a first evaporator 46, and a second evaporator 47. These components are connected to each other by flow paths 50 a to 50 f so as to form the refrigerant circuit 50.

  The compressor 2, the radiator 3 and the positive displacement fluid machine 4 are the same as those in the first embodiment, as can be understood from the same reference numerals. The expansion valve 45 is a valve whose opening degree can be changed, for example, an electric expansion valve. Each of the first evaporator 46 and the second evaporator 47 is a device for applying heat to the refrigerant, and typically includes an air-refrigerant heat exchanger.

  The flow path 50 a connects the compressor 2 and the radiator 3 so that the refrigerant compressed by the compressor 2 is supplied to the radiator 3. The flow path 50 b connects the radiator 3 and 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. The flow path 50 c connects the positive displacement fluid machine 4 and the first evaporator 46 so that the refrigerant discharged from the positive displacement fluid machine 4 is supplied to the first evaporator 46. The flow path 50 d connects the first evaporator 46 and the compressor 2 so that the refrigerant flowing out from the first evaporator 46 is supplied to the compressor 2. The flow path 50 e connects the radiator 3 and the second evaporator 47 so that a part of the refrigerant flowing out of the radiator 3 is supplied to the second evaporator 47. Specifically, the flow path 50e is a flow path (branch flow path) branched from the flow path 50b and is connected to the flow path 50b between the radiator 3 and the positive displacement fluid machine 4. And a downstream end connected to the second evaporator 47. An expansion valve 45 is disposed on the flow path 50e. The refrigerant is decompressed by the expansion valve 45 and then flows into the second evaporator 47. The flow path 50f connects the second evaporator 47 and the positive displacement fluid machine 4 so that the gas refrigerant flowing out of the second evaporator 47 is supplied (injected) to the positive displacement fluid machine 4.

  The first evaporator 46 and the second evaporator 47 are arranged on the flow path of the heat medium so that the heat medium (for example, air) cooled by the first evaporator 46 is further cooled by the second evaporator 47. ing. The direction indicated by the arrow in FIG. 9 is the flow direction of the heat medium. The temperature of the refrigerant in the first evaporator 46 is higher than the temperature of the refrigerant in the second evaporator 47. Therefore, as shown in FIG. 9, when the first evaporator 46 is arranged upstream of the flow path of the heat medium and the second evaporator 47 is arranged downstream, the heat medium (air), the refrigerant, As if to form a counter flow. This improves the efficiency of heat exchange between the refrigerant and the heat medium in the evaporators 46 and 47. Further, since the refrigerant flowing out from the second evaporator 47 is boosted by the positive displacement fluid machine 4, the COP of the refrigeration cycle apparatus 200 is improved as in the first embodiment.

  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. The cooled refrigerant flows through the two flow paths 50b and 50e. A part of the cooled refrigerant is sucked into the positive displacement fluid machine 4 through the flow path 50b. The refrigerant sucked into the positive displacement fluid machine 4 is decompressed to an intermediate pressure 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 46 through the flow path 50c. The refrigerant flowing into the first evaporator 46 is heated by the first evaporator 46 and then sucked into the compressor 2 through the flow path 50d. On the other hand, the remaining portion of the refrigerant cooled by the radiator 3 is decompressed by the expansion valve 45 and changed into a gas-liquid two-phase, and then supplied to the second evaporator 47 through the flow path 50e. The refrigerant flowing into the second evaporator 47 is heated by the second evaporator 47 and then supplied (injected) to the positive displacement fluid machine 4 through the injection flow path 50f.

(Modification)
In the first and second embodiments, the positive displacement fluid machine 4 has the structure of a two-stage rotary fluid machine. As the positive displacement fluid machine having the same function as the positive displacement fluid machine 4, another type, for example, a scroll type fluid machine may be used. Further, a positive displacement fluid machine having a structure of a single-stage rotary fluid machine having only one cylinder and one piston may be adopted. Such a positive displacement fluid machine is advantageous in reducing the number of parts, miniaturization and cost reduction.

  FIG. 14 is a longitudinal sectional view of a positive displacement fluid machine according to a modification. 15 is a cross-sectional view of the positive displacement fluid machine shown in FIG. 14 taken along the line WW. The positive displacement fluid machine 44 includes a sealed container 59, a shaft 53, an upper bearing 55, a cylinder 51, a piston 52, a vane 57, and a lower bearing 56. As described above, the positive displacement fluid machine 44 has a structure of a single-stage rotary fluid machine.

  As shown in FIG. 14, the shaft 53 has an eccentric portion 53a protruding outward in the radial direction. The shaft 53 passes through the cylinder 51 and is rotatably supported by an upper bearing 55 and a lower bearing 56. The rotation axis of the shaft 53 coincides with the center of the cylinder 51. The cylinder 51 is closed by the upper bearing 55 and the lower bearing 56.

  As shown in FIG. 15, the piston 52 has a ring shape in plan view, and is disposed in the cylinder 51 so as to form a crescent-shaped space 54 between itself and the cylinder 51. Inside the cylinder 51, a piston 52 is attached to an eccentric portion 53a of the shaft 53. A vane groove 68 is formed in the cylinder 51, and the vane 57 is attached to the vane groove 68 so as to be slidable. The vane 57 partitions the space 54 along the circumferential direction of the piston 52. As a result, a suction space 54 a and a discharge space 54 b are formed inside the cylinder 51. A spring 69 is disposed behind the vane 57. The spring 69 pushes the vane 57 toward the center of the shaft 53. Lubricating oil stored in the closed container 59 is supplied to the vane groove 68. In addition, the piston 52 and the vane 57 may be configured by a single component, a so-called swing piston. Further, the vane 57 may be engaged with the piston 52.

  As shown in FIG. 14, the positive displacement fluid machine 44 further includes a suction pipe 58, a suction port 60, a discharge pipe 62, a discharge port 63, an injection port 30, and an injection suction pipe 29. The refrigerant can be supplied to the space 54 (specifically, the suction space 54a) through the suction port 60. Through the discharge port 63, the refrigerant can be discharged from the space 54 (specifically, the discharge space 54b). A suction pipe 58 and a discharge pipe 62 are connected to the suction port 60 and the discharge port 63, respectively. The suction pipe 58 constitutes a part of the flow path 10b in the refrigerant circuit 10 (FIG. 1). The discharge pipe 62 constitutes a part of the flow path 10 c in the refrigerant circuit 10. The discharge port 63 is provided with a discharge valve 64 (a check valve) that prevents the refrigerant from flowing backward from the flow path 10c to the discharge space 54b. The discharge valve 64 is typically a reed valve made of a thin metal plate. When the pressure in the discharge space 54b exceeds the pressure inside the discharge pipe 62 (pressure in the flow path 10c), the discharge valve 64 opens. When the pressure in the discharge space 54b is equal to or lower than the pressure inside the discharge pipe 62, the discharge valve 64 is closed.

  The suction port 60 and the discharge port 63 are formed in the cylinder 51 and the lower bearing 56, respectively. However, the suction port 60 may be formed in the upper bearing 55 or the lower bearing 56. The discharge port 63 may be formed in the upper bearing 55 or the cylinder 51.

  The positive displacement fluid machine 44 further includes a suction mechanism 61 that controls the timing at which the refrigerant flows into the space 54 of the cylinder 51 through the suction port 60. In this modification, the suction mechanism 61 is constituted by a solenoid valve including a suction valve 61a and a solenoid 61b. By switching on and off the applied voltage of the solenoid 61b, the opening and closing of the intake valve 61a can be controlled.

  The injection port 30 is formed in the upper bearing 55 so that the refrigerant can be supplied to the suction space 54a. The injection port 30 is provided with a check valve 34 that prevents a reverse flow of the refrigerant from the suction space 54a or the discharge space 54b to the injection flow path 10f. The detailed structures of the injection port 30 and the check valve 34 are as described in the first embodiment.

  In this modification, the position where the vane 57 is disposed (the position of the vane groove 68) with respect to the rotation direction of the shaft 53 is defined as a “reference position” having an angle of 0 degrees. As shown in FIG. 15, the injection port 30 is provided in a range of 0 to 180 degrees (or 0 to 90 degrees), for example, with respect to the rotation direction (clockwise direction) of the shaft 53. Thereby, excessive overexpansion can be prevented. The suction port 60 and the discharge port 63 are provided at positions adjacent to the vane 57.

  In the positive displacement fluid machine 44, the suction space 54a functions as a working chamber for sucking, expanding and overexpanding the refrigerant. The discharge space 54b functions as a working chamber for recompressing and discharging the refrigerant.

  Next, the detailed operation of the positive displacement fluid machine 44 will be described with reference to FIGS. 10 and 16. FIG. 16 is an operation principle diagram of the positive displacement fluid machine 44. In the upper left view, upper right view, lower right view, and lower left view of FIG. 16, the position of the piston 52 when the shaft 53 is rotated by 90 degrees is shown. The intake valve 61a opens, for example, when the rotation angle of the shaft 53 is in the range of 0 to 90 degrees, and thereafter repeats opening and closing with 360 degrees as one cycle.

  As shown in the upper left diagram and the upper right diagram in FIG. 16, when the shaft 53 rotates from the 0 degree position to the 90 degree position, a suction space 54 a is newly created adjacent to the suction port 60. The refrigerant is sucked into the suction space 54a through the suction port 60 (suction stroke). When the shaft 53 rotates from the 0 degree position to the 90 degree position, the suction valve 61a is closed. Thereby, the suction stroke is completed. In FIG. 10, the suction stroke is indicated by a line AB.

  When the suction valve 61a is closed, the refrigerant expands to the discharge pressure P2 in the suction space 54a (expansion stroke). As the shaft 53 rotates, the refrigerant overexpands to a pressure P3 lower than the discharge pressure P2 (overexpansion stroke). In the expansion stroke and the overexpansion stroke, the positive displacement fluid machine 44 recovers power from the refrigerant. In FIG. 10, the expansion stroke and the overexpansion stroke are indicated by a line BCD.

  When the refrigerant overexpands and the pressure in the suction space 54a falls below the pressure inside the injection suction pipe 29, the refrigerant overexpansion stops. At the same time, the refrigerant having the pressure P3 is supplied to the suction space 54a through the injection port 30. In the suction space 54a, the supplied refrigerant is mixed with the overexpanded refrigerant (injection stroke).

  Thereafter, the refrigerant having the pressure P3 continues to be supplied to the suction space 54a through the injection port 30 until the rotation angle of the shaft 53 reaches 360 degrees. As shown in the upper left diagram of FIG. 16, when the shaft 53 rotates to a position of 360 degrees, the volume of the suction space 54a reaches the maximum volume (= the volume of the space 54). Thereby, the injection process ends. In FIG. 10, the injection stroke is indicated by a line DE. The volume V1 of the working chamber (suction space 54a) at the end of the suction stroke is defined by the rotation angle of the shaft 53 at the moment when the suction valve 61a is closed.

  Next, as shown in the upper left view and the upper right view of FIG. 16, when the shaft 53 rotates from the 360 degree position to the 450 degree position, the suction space 54a changes to the discharge space 54b. The discharge port 63 faces the discharge space 54b. However, as described with reference to FIG. 14, the discharge port 63 is provided with the discharge valve 64. Therefore, the refrigerant is compressed in the discharge space 54b until the pressure in the discharge space 54b exceeds the pressure in the discharge pipe 62, that is, the suction pressure of the compressor 2 (recompression process).

  When the pressure in the discharge space 54b exceeds the pressure in the discharge pipe 62, the discharge valve 64 opens. Thus, the refrigerant is discharged from the discharge space 54b to the discharge pipe 62 through the discharge port 63 (discharge process). As the shaft 53 rotates, the volume of the discharge space 54b decreases. When the shaft 53 rotates to a position of 720 degrees, the discharge space 54b disappears. Thereby, the discharge stroke is completed. In FIG. 10, the recompression stroke and the discharge stroke are indicated by lines EF and FG, respectively.

  As described above, the positive displacement fluid machine 44 of this modification has the same function as the positive displacement fluid machine 4 described in the first embodiment.

  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, 44 Positive displacement fluid machine 5 Gas-liquid separator 6 Expansion valve 7 Evaporator 10a-10f Flow path 11 1st cylinder 12 2nd cylinder 13 1st piston 14 2nd piston 15 Shaft 16 1st Space 16a First suction space 16b First discharge space 17 Second space 17a Second suction space 17b Second discharge spaces 18, 55 Upper bearing (first closing member)
19, 56 Lower bearing (second closing member)
19c Internal passage 19g Recess 20 First vane 21 Second vane 24 Suction port 25a Communication hole 27 Discharge port 30 Injection port 31 Valve body 32 Valve stop 34 Check valve 45 Expansion valve 46 First evaporator 47 Second evaporator 50a -50f Flow path 51 Cylinder 52 Piston 53 Shaft 54 Space 54a Suction space 54b Discharge space 60 Suction port 63 Discharge port 100, 200 Refrigeration cycle apparatus

Claims (12)

A compressor for compressing the refrigerant;
A radiator for cooling the refrigerant compressed by the compressor;
An operating chamber and an injection port; (i) a step of sucking the refrigerant cooled by the radiator into the working chamber at a first pressure; and (ii) a refrigerant sucked in the working chamber in the first chamber. A step of expanding to a second pressure lower than the second pressure and further overexpanding to a third pressure lower than the second pressure; and (iii) applying the third pressure to the working chamber through the injection port. A step of supplying the refrigerant having, and mixing the supplied refrigerant with the overexpanded refrigerant, and (iv) using the power recovered from the refrigerant in the step (ii), and mixing the refrigerant to the second pressure A positive displacement fluid machine configured to perform a step of recompressing in the working chamber; and (v) a step of discharging the recompressed refrigerant from the working chamber;
An evaporator for heating the refrigerant discharged from the positive displacement fluid machine;
An injection flow path for supplying the refrigerant having the third pressure to the injection port of the positive displacement fluid machine;
With
The ratio (Ve / V1) of the volume Ve of the working chamber in the expansion stroke or the overexpansion stroke to the suction volume V1 of the working chamber is the density of the refrigerant at the first pressure with respect to the density ρ3 of the refrigerant at the third pressure. The refrigeration cycle apparatus in which the injection port opens into the working chamber when the ratio is equal to or smaller than the ratio of ρ1 (ρ1 / ρ3). The positive displacement fluid machine comprises:
A first cylinder;
A first piston disposed inside the first cylinder so as to form a first space between itself and the first cylinder;
A first vane that partitions the first space into a first suction space and a first discharge space;
A second cylinder disposed concentrically with respect to the first cylinder;
A second piston disposed inside the second cylinder so as to form a second space having a volume larger than that of the first space between itself and the second cylinder;
A second vane that partitions the second space into a second suction space and a second discharge space;
An intermediate plate disposed between the first cylinder and the second cylinder;
A communication channel provided in the intermediate plate so as to communicate the first discharge space and the second suction space;
A suction port for supplying a refrigerant to the first suction space;
A discharge port for discharging the refrigerant from the second discharge space,
The working chamber is configured by the first space, the second space, and the communication channel,
The refrigeration cycle apparatus according to claim 1, wherein the injection port is open toward the second space. The positive displacement fluid machine closes the end surface of the first cylinder at a position facing the middle plate, and the second closing member closes the end surface of the second cylinder at a position facing the middle plate. A member, and
The refrigeration cycle apparatus according to claim 2, wherein the injection port is provided in the second closing member. The positive displacement fluid machine further includes a shaft that rotates the first piston and the second piston;
The communication channel has an opening facing the second cylinder;
Two virtual planes that include the rotation axis of the shaft and are in contact with the opening are a first plane pair, and two virtual planes that include the rotation axis of the shaft and are in contact with the injection port are a second plane pair. When defined as
The refrigeration cycle apparatus according to claim 2 or 3, wherein an angle range sandwiched between the first plane pairs overlaps an angle range sandwiched between the second plane pairs.   The positive displacement fluid machine further includes an internal flow path for introducing a refrigerant from the injection flow path to the injection port, and a check valve provided in the internal flow path. The refrigeration cycle apparatus described in 1. The positive displacement fluid machine includes a recess for disposing the check valve as a part of the internal flow path,
The check valve restricts the movement of the valve body, the valve body that is moved by the pressure difference between the pressure in the injection flow path and the pressure in the working chamber so as to open and close the valve opening. Composed of a valve stop and
The refrigeration cycle apparatus according to claim 5, wherein the valve stop has a shape along the shape of the recess so as to reduce a volume of a space from the valve port to the injection port. When the volume of the working chamber at the start of the stroke (iv) is V2,
The ratio (V2 / V1) of the volume V2 to the suction volume V1 is larger than a ratio (ρ1 / ρ2) of the density ρ1 of the refrigerant at the first pressure to the density ρ2 of the refrigerant at the second pressure. Item 7. The refrigeration cycle apparatus according to any one of Items 1 to 6.   The injection flow path connects the evaporator and the positive displacement fluid machine so that the refrigerant flowing out of the evaporator is supplied to the positive displacement fluid machine as a refrigerant having the third pressure; The refrigeration cycle apparatus according to any one of claims 1 to 7. A gas-liquid separator that separates the refrigerant discharged from the positive displacement fluid machine into a gas refrigerant and a liquid refrigerant;
A flow path connecting the gas-liquid separator and the compressor so that the gas refrigerant separated by the gas-liquid separator is supplied to the compressor;
A flow path connecting the gas-liquid separator and the evaporator so that the liquid refrigerant separated by the gas-liquid separator is supplied to the evaporator;
The refrigeration cycle apparatus according to claim 8, further comprising:   The refrigeration cycle apparatus according to claim 9, further comprising a pressure reducing valve provided on the flow path connecting the gas-liquid separator and the evaporator. A flow path connecting the radiator and the positive displacement fluid machine so that the refrigerant flowing out of the radiator is supplied to the positive displacement fluid machine;
A branch flow path having an upstream end connected to the flow path between the radiator and the positive displacement fluid machine;
A pressure reducing valve provided on the branch flow path;
A second evaporator to which a downstream end of the branch flow path is connected, and
The injection flow path connects the second evaporator and the positive displacement fluid machine so that the refrigerant flowing out of the second evaporator is supplied to the positive displacement fluid machine as the refrigerant having the third pressure. The refrigeration cycle apparatus according to any one of claims 1 to 7. When the evaporator that heats the refrigerant discharged from the positive displacement fluid machine is the first evaporator,
The refrigeration cycle apparatus further includes a flow path connecting the first evaporator and the compressor so that the refrigerant heated by the first evaporator is supplied to the compressor,
The first evaporator is disposed on the upstream side of the flow path of the heat medium, and the second evaporator is disposed on the downstream side so that the heat medium that has heated the refrigerant in the first evaporator flows into the second evaporator. The refrigeration cycle apparatus according to claim 11.

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