JP4842022B2 - Vapor compression refrigeration circuit and vehicle air conditioning system using the circuit - Google Patents

Description

  The present invention relates to a vapor compression refrigeration circuit and a vehicle air conditioning system using the refrigeration circuit.

The refrigeration circuit is used in, for example, a vehicle air conditioning system, and includes a circulation channel through which a refrigerant circulates. In general, a compressor, a radiator (condenser or gas cooler), a decompressor (expansion valve), and an evaporator are sequentially inserted in the circulation channel in the flow direction of the refrigerant.
In addition, a gas-liquid separator that separates a gas phase component and a liquid phase component in the refrigerant is inserted in the circulation channel, and the gas-liquid separator is disposed downstream of the radiator or downstream of the evaporator. .

By the way, in recent years, a refrigeration circuit using a refrigerant with a small global warming potential has been developed from the viewpoint of environmental issues. As an example of this type of refrigerant, non-toxic and non-flammable natural CO ₂ (carbon dioxide) has been proposed. The refrigeration circuit using CO ₂ as a refrigerant is a transcritical cycle because the critical temperature of CO ₂ is as low as about 31 ° C. On the high pressure side of the refrigeration circuit, the refrigerant is in a supercritical state at a pressure of about 7.4 MPa, for example. Become. In such a refrigeration circuit, CO ₂ does not condense in the radiator, so the accumulator as a gas-liquid separator is inserted downstream of the evaporator in the circulation channel.

In addition, in a refrigeration circuit using CO ₂ , an internal heat exchanger may be interposed in the circulation channel in order to improve the refrigeration coefficient of performance (COP) (see, for example, Patent Document 1). Specifically, the internal heat exchanger is interposed between a high-temperature portion inserted in a circulation channel portion extending between the radiator and the decompressor, and a circulation channel portion extending between the accumulator and the compressor. And a low temperature part to be inserted. In the internal heat exchanger, heat exchange is performed between the high-pressure refrigerant flowing in the high-temperature part and the low-pressure refrigerant flowing in the low-temperature part, and the enthalpy of the refrigerant at the inlet of the evaporator is reduced. As a result, the enthalpy change amount of the refrigerant in the evaporator is increased, and the refrigeration performance coefficient of the refrigeration circuit is improved.
Japanese Patent Laid-Open No. 11-193967

A conventional refrigeration circuit includes a compressor, a radiator, a decompressor, an evaporator, and an accumulator as main devices, and a pipe extending between the main devices as a connection part for connecting between the entrances and exits of these main devices. And a joint member for connecting the device and the pipe.
For this reason, there are a large number of main devices and connecting parts that make up the refrigeration circuit, and the assembly of the refrigeration circuit, especially the work of installing the refrigeration circuit in the vehicle as part of the vehicle air conditioning system, requires space in the engine room. It is complicated because it tends to decrease.

Further, in a refrigeration circuit using CO ₂ as a refrigerant, the pressure on the high pressure side is higher than that in the case of using a conventional HFC-based refrigerant, and there is a concern about refrigerant leakage around the joint member.
In addition, when an internal heat exchanger is used in the refrigeration circuit, not only worse mounting on the vehicle and increased concern about refrigerant leakage, but also the refrigerant temperature at the inlet and outlet of the compressor rises and compression occurs. The heat insulation efficiency (compression efficiency) of the machine decreases.

  The present invention has been made on the basis of the above-described circumstances, and the object of the present invention is to reduce the number of main devices and connecting parts to prevent refrigerant leakage and to make the vapor compression refrigeration easy to assemble. An object is to provide a vehicle and an air conditioning system for a vehicle using the refrigeration circuit.

In order to achieve the above object, according to the present invention, a high temperature of a compressor, a radiator, and an internal heat exchanger that are inserted in a circulation flow path through which the refrigerant circulates and sequentially inserted in the flow direction of the refrigerant. A vapor compression refrigeration circuit including a low-temperature part of the internal pressure exchanger, the decompressor, the evaporator, the accumulator, and the internal heat exchanger, wherein the decompressor, the accumulator, and the internal heat exchanger are formed integrally with each other , Superheating degree reducing means for exchanging heat between the liquid phase component of the refrigerant stored in an accumulator and the gas phase component of the refrigerant flowing out from the low temperature part of the internal heat exchanger, the superheat degree reducing means includes A pipe inserted in a portion of the circulation flow path extending between the low temperature portion of the internal heat exchanger and the compressor and passing through a bottom portion of the accumulator, and the pipe is formed on an inner wall surface of the accumulator. Has a connection to an inlet end and an outlet end, the position of the outlet end of the pipe, is higher than the liquid level of the liquid phase component of the refrigerant stored in the high and the accumulator than the position of the inlet end A vapor compression refrigeration circuit is provided (claim 1).

Preferably, the decompressor and the accumulator are adjacent to each other (Claim 2) .

Preferably, the degree of superheat reduction further includes a concavo-convex portion formed on at least one of an inner peripheral surface and an outer peripheral surface of the pipe (claim 3 ).
Preferably, the pipe has an oil return hole for sucking lubricating oil stored in the accumulator (claim 4).

Preferably, the refrigerant is CO ₂ (Claim 5 ).
According to the present invention, there is provided a vehicle air-conditioning system comprising the vapor compression refrigeration circuit according to any one of claims 1 to 5 (claim 6 ).

  In the vapor compression refrigeration circuit according to the first aspect of the present invention, the decompressor, the accumulator and the internal heat exchanger are integrally formed with each other. That is, the decompressor, the accumulator, and the internal heat exchanger constitute one module. For this reason, the number of main equipments constituting the refrigeration circuit is reduced, and the pipes for connecting between the pressure reducer and the accumulator and the internal heat exchanger and the joint members attached to the pipes are reduced and connected. The number of parts can be reduced. As a result, the vapor compression refrigeration circuit is not only easy to assemble, but also can be miniaturized.

Moreover, in this vapor compression refrigeration circuit, the risk of refrigerant leakage from the periphery of the joint member is reduced by reducing the number of joint members.
The superheat reduction means performs heat exchange between the liquid phase component of the refrigerant stored in the accumulator and the gas phase component of the refrigerant flowing out from the low temperature portion of the internal heat exchanger. Thereby, the temperature of the refrigerant | coolant in the inlet_port | entrance of a compressor falls, and the heat insulation efficiency (compression efficiency) of a compressor improves. In addition, the power required to compress the refrigerant decreases due to a decrease in the degree of superheat of the refrigerant at the inlet of the compressor. As a result, COP is improved in this refrigeration circuit.
The superheat reduction means includes a pipe, and the pipe is inserted into a portion of the circulation flow path extending between the low temperature portion of the internal heat exchanger and the compressor, and passes through the bottom of the accumulator. In this refrigeration circuit, a simple configuration of a pipe passing through the bottom of the accumulator allows a liquid phase component of the refrigerant stored in the accumulator and a gas phase component of the refrigerant flowing out from the low temperature part of the internal heat exchanger. Heat exchange is ensured.
Furthermore, since the outlet end of the pipe of the superheat reduction means is higher than the inlet end, the pipe also extends in the vertical direction in the accumulator, and the contact area between the liquid phase component of the refrigerant stored in the accumulator and the pipe Becomes larger. As a result, heat exchange through the pipe is efficiently performed, and the COP of the refrigeration circuit is further improved.
Further, since the outlet end of the pipe is positioned higher than the inlet end, the liquid refrigerant is prevented from flowing out from the accumulator, and the occurrence of liquid compression in the compressor is prevented.
In the vapor compression refrigeration circuit according to the second aspect, since the pressure reducer and the accumulator are adjacent to each other, further miniaturization can be achieved.
Further, in this vapor compression refrigeration circuit, heat exchange is performed between the decompressor and the accumulator, so that the amount of heat exchange in the internal heat exchanger may be small. As a result, the internal heat exchanger can be downsized, and the refrigeration circuit itself can be further downsized.

In the vapor compression refrigeration circuit according to the third aspect, the superheat degree reducing means further includes an uneven portion formed on at least one of the inner peripheral surface and the outer peripheral surface of the pipe. The surface area of the pipe is increased by the uneven portion, whereby heat exchange through the pipe is efficiently performed, and the COP of the refrigeration circuit is further improved.
In the vapor compression refrigeration circuit according to the fourth aspect , the pipe of the superheat reduction means has an oil return hole for sucking the lubricating oil stored in the accumulator. As a result, the lubricating oil is reliably returned to the compressor, and the durability of the compressor is ensured.

In the vapor compression refrigeration circuit of claim 5 , since CO ₂ is used as the refrigerant, it is friendly to the global environment. Further, in this refrigeration circuit, since the number of joint members is reduced, leakage of the refrigerant is prevented even when CO ₂ whose pressure is increased is used as the refrigerant.
Since the vehicular air conditioning system according to the sixth aspect uses the vapor compression refrigeration circuit according to the first to fifth aspects, it can be easily mounted on the vehicle.

FIG. 1 shows an outline of a refrigeration circuit of a vehicle air conditioning system according to an embodiment. The refrigeration circuit is a vapor compression type and is used for cooling or dehumidifying an air flow sent to a passenger compartment 2.
The refrigeration circuit has a circulation flow path 4, and CO ₂ refrigerant (R-744), which is a natural refrigerant, circulates in the circulation flow path 4 with a small amount of lubricating oil as refrigerating machine oil included. The circulation channel 4 passes from the engine room 6 through the partition wall 8 to the front part of the vehicle compartment 2, and the front part of the vehicle compartment 2 is partitioned as an instrument space 12 by the instrument panel 10.

  In the circulation channel 4, a compressor 14, a radiator 16 and an evaporator 18 are inserted, and an internal heat exchanger module 20 is further inserted. The module 20 is configured by integrally forming a decompressor (expansion valve), an accumulator (gas-liquid separator), and an internal heat exchanger. For this reason, the circulation flow path 4 substantially includes a compressor 14, a radiator (gas cooler) 16, a high temperature part (high pressure part) of an internal heat exchanger, a decompressor, an evaporator 18, an accumulator, and an internal heat exchanger. The low temperature part is inserted sequentially.

Hereinafter, the module 20 will be described.
As shown in FIGS. 2 and 3, the module 20 includes a rectangular parallelepiped block 22 and a box-shaped casing 24. The block 22 and the casing 24 are joined to each other by brazing, and the joined body of the block 22 and the casing 24 forms one rectangular parallelepiped shape. That is, the front and back surfaces of the block 22 and the casing 24 are positioned flush with each other.

Two adapters 26 and 26 are joined to the back surface of the joined body of the block 22 and the casing 24 by brazing, and each adapter 26 has an oval shape having a predetermined thickness. Both ends of a U-shaped heat exchange tube 28 are joined to each outer surface of the adapter 26 by brazing.
Four ports 30, 32, 34, and 36 are opened on the front surface of the joined body. Of these, two ports 30, 32 are formed on the block 22 so as to be spaced apart from each other, and the remaining two ports. 34 and 36 are formed in the casing 24 so as to be spaced apart from each other in the vertical direction. Of the two ports 30 and 32 formed in the block 22, although not shown, a pipe extending from the outlet of the radiator 16 is connected to the lower port 32 via a joint member, and the upper port 30 is connected to the upper port 30. A pipe extending from the inlet of the evaporator 18 is connected via a joint member.

  Of the ports 34 and 36 formed in the casing 24, a pipe extending from the inlet of the compressor 14 is connected to the lower port 36 via a joint member, and the evaporator 18 is connected to the upper port 34. A pipe extending from the outlet is connected via a joint member. The ports 30 and 34 on the upper side of the block 22 and the casing 24 have the same vertical position, and these ports 30 and 34 have two pipes extending from the evaporator 18 by one joint member. Connected.

  As shown in FIG. 4, the block 22 is formed with a first internal flow path 38 that extends straight from the lower port 32 to the back surface. The first internal flow path 38 has an open end that opens to the back surface of the block 22, and the open end of the first internal flow path 38 is on the surface (inner surface) on the block 22 side of the lower adapter 26. One end of the formed groove (central groove) 40 is continuous. The central groove 40 extends in the longitudinal direction of the adapter 26, and the other end of the central groove 40 communicates with a central hole 42 that penetrates the center of the adapter 26 in the thickness direction. The central hole 42 has an open end that opens to the surface (outer surface) of the adapter 26 opposite to the block 22.

  Here, as shown in FIG. 5, the heat exchange tube 28 has a coaxial double tube structure and functions as an internal heat exchanger. That is, the heat exchange tube 28 includes a small diameter tube 44, and the small diameter tube 44 is surrounded by a coaxial large diameter tube 46. In the heat exchange tube 28, the inside of the small diameter tube 44 is secured as a flow path (high temperature part) 48, and the internal flow path 48 and the central hole 42 of the upper and lower adapters 26 communicate with each other.

  Further, in the heat exchange tube 28, a substantially cylindrical tubular shape is provided between the small-diameter pipe 44 and the large-diameter pipe 46 by the columnar portion 50 that integrally connects the small-diameter pipe 44 and the large-diameter pipe 46. A flow path (low temperature part) 52 is secured. An upper hole 54 and a lower hole 56 are formed in the adapter 26 above and below the central hole 42, and the upper hole 54 and the lower hole 56 also penetrate the adapter 26 in the thickness direction. The open ends of the upper hole 54 and the lower hole 56 that open to the outer surfaces of the upper and lower adapters 26 are connected to the cylindrical flow path 52 of the heat exchange tube 28. An upper groove 58 and a lower groove 60 are formed on the inner surface of the adapter 26. The upper groove 58 and the lower groove 60 are directed from the upper hole 54 and the lower hole 56 toward the side opposite to the central groove 40 in the longitudinal direction of the adapter 26. It extends.

  A second internal channel 62 formed in the block 22 is connected to one end of the central groove 40 formed in the inner surface of the upper adapter 26. The second internal flow path 62 extends horizontally from the back surface of the block 22 toward the front, and the inner end of the second internal flow path 62 is connected to the lower end of the valve hole 64 extending vertically in the block 22. ing. The upper end of the valve hole 64 is connected to the inner end of the third internal flow channel 66 extending partway from the upper port 30 of the block 22 toward the back.

  The upper end portion of the valve hole 64 is formed as a spherical seat, and a spherical valve body 68 sits on the spherical seat from above. The spherical seat and the valve body 68 constitute a pressure reducer. A compression coil spring 70 is disposed above the valve body 68, and the compression coil spring 70 always urges the valve body 68 downward. On the other hand, a rod 72 extending vertically in the block 22 is connected to the lower side of the valve body 68, and a lower end portion of the rod 72 is positioned in the first internal flow path 38. The rod 72 expands and contracts according to the temperature of its lower end (temperature sensing part). Therefore, the lift amount of the valve body 68 from the spherical seat, that is, the valve opening of the decompressor is determined so that the urging forces of the rod 72 and the compression coil spring 70 are balanced.

On the other hand, as shown in FIGS. 6 and 7, the casing 24 has a box shape in which the side surface on the block 22 side is open, and the opening edge of the casing 24 is joined to the peripheral edge of the side surface of the block 22 by brazing. Yes.
Four connecting holes 72, 74, 76, and 78 that are spaced apart from each other are formed in the rear wall of the casing 24, and the connecting holes 72, 74, 76, and 78 are located at the center in the width direction of the casing 24. It penetrates. The connection holes 72, 74, 76, and 78 form a pair, and the opening ends of the pair of connection holes 72, 74, 76, and 78 that are opened on the back surface of the casing 24 are formed on the inner surface of each adapter 26. One end of the upper groove 58 or the lower groove 60 is continuous. Accordingly, the connection holes 72, 74, 76, 78 are connected to the cylindrical flow path 52 of the heat exchange tube 28 through the adapter 26.

  Inside the casing 24, a pipe (heat transfer tube) 80 for heat exchange, also referred to as a low fin tube, is arranged. As shown in detail in FIG. A spirally extending protrusion 82 is integrally formed. The outlet end of the pipe 80 is joined to the inner surface of the front wall of the casing 24 by brazing, and the lower port 36 is opened in the area of the front wall surrounded by the outlet end. The inlet end of the pipe 80 is joined to the inner surface of the rear wall of the casing 24 by brazing, and a pair of lower connection holes 76 and 78 are opened in the region of the rear wall surrounded by the inlet end. ing.

  Here, although the pipe 80 extends in the bottom of the rectangular space 84 surrounded by the casing 24, the position of the inlet end of the pipe 80 is lower than the position of the outlet end in the vertical direction. For this reason, the pipe 80 extends not only horizontally but also vertically. Although the liquid phase components of the lubricating oil and the refrigerant are stored at the bottom of the space 84, the outlet end of the pipe 80 is positioned higher than the liquid surface 86 of the liquid phase component.

Note that an oil return hole 88 is formed in the pipe 80 so as to penetrate the bottom of the peripheral wall.
Hereinafter, the operation of the above-described refrigeration circuit will be described with reference to the Moliere diagram (ph diagram) of FIG.
In this refrigeration circuit, the compressor 14 supplied with power from the engine sucks the low-temperature and low-pressure gas-phase refrigerant flowing out from the port 36 of the module 20. The state of the refrigerant at the inlet of the compressor 14 is indicated by a point a in FIG.

The compressor 14 compresses the sucked refrigerant to a supercritical state of high temperature and pressure, and then discharges it toward the radiator 16. In other words, the compressor 14 executes the refrigerant suction, compression, and discharge steps, whereby the refrigerant is circulated in the circulation flow path 4. The state of the refrigerant at the outlet of the compressor 14 is indicated by a point b.
When the refrigerant flowing out of the compressor 14 passes through the radiator 16, it is air-cooled by the wind from the front of the vehicle or from the fan, and its temperature decreases. The state of the refrigerant at the outlet of the radiator 16 is indicated by a point c.

  The refrigerant flowing out of the radiator 16 flows into the module 20 through the port 32. The refrigerant flowing into the module 20 sequentially flows through the first internal flow path 38 of the block 22, the central groove 40 and the central hole 42 of the lower adapter 26, and then flows into the internal flow path 48 of the heat exchange tube 28. . In the heat exchange tube 28, heat exchange is performed between the refrigerant flowing through the internal flow path 48 and the refrigerant flowing through the cylindrical flow path 52. For this reason, the enthalpy of the refrigerant that has flowed out of the internal flow path 48 is lower by Δh2 than before flowing into the internal flow path 48, and the state of the refrigerant that has flowed out of the internal flow path 48 is indicated by a point d. .

  The refrigerant that has passed through the internal flow path 48 of the heat exchange tube 28 flows into the second internal flow path 62 of the block 22 through the central hole 42 and the central groove 40 of the upper adapter 26. Then, the refrigerant flows through the valve hole 64 and the third internal flow channel 66 and once flows out of the module 20 through the port 30. Here, the cross-sectional area of the flow path at the upper end portion of the valve hole 64 is reduced by the spherical seat and the valve body 68 constituting the decompressor, and the refrigerant expands when passing through the upper end portion of the valve hole 64. Along with this expansion, the pressure of the refrigerant decreases and becomes below the critical pressure. The state of the refrigerant at the port 30 is a gas-liquid mixed state and is represented by a point e.

When the liquid phase component contained in the refrigerant in the gas-liquid mixed state passes through the evaporator 18, it evaporates and takes heat of vaporization from the surroundings, whereby the air flow flowing outside the evaporator 18 becomes cold air. The cold air flows into the passenger compartment 2 so that the passenger compartment 2 is cooled or dehumidified. The state of the refrigerant at the outlet of the evaporator 18 is represented by a point f.
The refrigerant in which the liquid phase component is almost evaporated in the evaporator 18 flows into the casing 24 of the module 20 through the port 34. The refrigerant flowing into the casing 24 flows through the space 84 and then flows into the connection holes 72 and 74. However, the liquid phase component slightly remaining in the refrigerant does not flow into the connection holes 72 and 74 but flows into the connection holes 72 and 74. It collides with and adheres to the inner surface. The liquid phase component of the adhering refrigerant flows down the inner surface as it is and is stored at the bottom of the space 84.

  On the other hand, the gas phase component of the refrigerant that has passed through the space 84 flows into the cylindrical flow path 52 of the heat exchange tube 28 through the upper groove 58 and the lower groove 60, the upper hole 54, and the lower hole 56 of the upper adapter 26. As described above, the refrigerant flowing through the cylindrical flow path 52 is heated by heat exchange with the refrigerant flowing through the internal flow path 48, and the enthalpy increases by Δh1. The state of the refrigerant that has passed through the cylindrical flow path 52 at the inlet of the pipe 80 is indicated by a point g. From the first law of thermodynamics, Δh1≈Δh2.

  Thereafter, the refrigerant that has passed through the cylindrical flow channel 52 flows into the pipe 80 through the upper hole 54 and the lower hole 56, the upper groove 58 and the lower groove 60, and the connection holes 76 and 78 of the lower adapter 26. Heat exchange is also performed between the refrigerant passing through the pipe 80 and the liquid phase component of the refrigerant in contact with the outer peripheral surface of the pipe 80, and the enthalpy of the refrigerant is reduced by Δh3. The state of the refrigerant passing through the pipe 80 at the port 36 is indicated by a point a.

Then, the refrigerant that has passed through the pipe 80 flows out of the module 20 through the port 36 and is sucked into the compressor 14 again. Note that the lubricating oil accumulated at the bottom of the space 84 due to the flow of the refrigerant in the pipe 80 is sucked into the pipe 80 through the oil return hole 88. For this reason, the lubricating oil is also returned to the compressor 14 together with the refrigerant.
In the above-described refrigeration circuit, the decompressor, the accumulator, and the internal heat exchanger are integrally formed to constitute one module 20 that cannot be separated from each other. For this reason, the number of main equipments constituting the refrigeration circuit is reduced, and the pipes for connecting between the pressure reducer and the accumulator and the internal heat exchanger and the joint members attached to the pipes are reduced and connected. The number of parts can be reduced. As a result, the refrigeration circuit is not only easy to assemble but also downsized, and the vehicle air conditioning system using the refrigeration circuit can be easily mounted on a vehicle.

Moreover, in this refrigeration circuit, the risk of refrigerant leakage from the vicinity of the joint member is reduced by reducing the number of joint members.
Further, in the module 20 used in this refrigeration circuit, the block 22 incorporating the pressure reducer and the casing 24 constituting the accumulator are adjacent (surface contact) with the side surface as a boundary, and have a left and right two-layer structure. Miniaturization is achieved.

  Further, according to the module 20 used in this refrigeration circuit, heat exchange is performed between the pressure reducer and the accumulator, so that the amount of heat exchange in the internal heat exchanger may be small. As a result, the heat exchange tube 28 as an internal heat exchanger can be downsized, and the refrigeration circuit itself can be further downsized. In the heat exchange tube 28, the flow direction of the refrigerant in the internal flow path 48 and the flow direction of the refrigerant in the cylindrical flow path 52 are preferably opposite to each other. This is because the temperature difference of the refrigerant can be increased between the internal channel 48 and the cylindrical channel 52, and the efficiency of heat exchange can be increased.

  In addition, the module 20 used in this refrigeration circuit has a pipe 80 as superheat reduction means. Through this pipe 80, heat exchange is performed between the liquid phase component of the refrigerant stored in the accumulator and the gas phase component of the refrigerant flowing out from the low temperature portion of the internal heat exchanger, so that the compressor 14 The temperature of the refrigerant at the inlet is lowered, the heat insulation efficiency (compression efficiency) of the compressor 14 is improved, and the power required for refrigerant compression is reduced. That is, in the case of an isentropic change in the compressor, the smaller the refrigerant superheat, the smaller the inclination in the Moliere diagram, and the compressor power decreases. As a result of these, the COP is improved in this refrigeration circuit.

The configuration of the superheat degree reducing means is not particularly limited, but the pipe 80 is preferably used. This is because the simple configuration of the pipe 80 ensures the heat exchange between the liquid phase component of the refrigerant stored in the accumulator and the gas phase component of the refrigerant flowing out from the low temperature portion of the internal heat exchanger. .
Further, it is preferable that the superheat degree reducing means has irregularities such as protrusions 82 on at least one of the inner peripheral surface and the outer peripheral surface of the pipe 80. This is because the heat exchange through the pipe 80 is efficiently performed by increasing the surface area, and the COP of the refrigeration circuit is further improved.

Further, the pipe 80 preferably has an oil return hole 88. In this case, the lubricating oil is reliably returned to the compressor 14, and the durability of the compressor 14 is ensured.
Moreover, the outlet end of the pipe 80 is preferably higher than the inlet end. As a result, the pipe 80 also extends in the vertical direction in the accumulator, and the contact area between the liquid phase component of the refrigerant stored in the accumulator and the pipe increases. As a result, heat exchange through the pipe 80 is efficiently performed, and the COP of the refrigeration circuit is further improved.

Further, since the outlet end of the pipe 80 is positioned higher than the inlet end, the liquid refrigerant is prevented from flowing out from the accumulator, and the occurrence of liquid compression in the compressor 14 is prevented.
On the other hand, since this refrigeration circuit uses CO ₂ as a refrigerant, it is friendly to the global environment. Further, in this refrigeration circuit, since the number of joint members is reduced, leakage of the refrigerant is prevented even when CO ₂ whose pressure is increased is used as the refrigerant.

The present invention is not limited to the above-described embodiment, and various modifications are possible. For example, the refrigerant is not limited to CO ₂ .
In the above-described embodiment, although the material of each component constituting the module 20 is not particularly limited, in order to increase the heat exchange efficiency between the pressure reducer and the accumulator, for example, it has excellent thermal conductivity such as copper and aluminum. It is preferable to use a metal.

In the above-described embodiment, the heat exchange tube 28 having a double tube structure is used. However, as shown in FIG. 9, for example, the heat formed by laminating, for example, three flat tubes 92 each having a plurality of pores 90. An exchange tube 94 may be used. According to the heat exchange tube 94, heat exchange efficiency can be improved by alternately laminating the high pressure side and the low pressure side.
In the above-described embodiment, the decompressor of the module 20 is a temperature type expansion valve in which the valve opening degree varies depending on the temperature, but may be a variable orifice in which the valve opening degree varies depending on the flow rate of the refrigerant.

It is a schematic block diagram of the refrigerating circuit of the vehicle air conditioning system which concerns on one Embodiment of this invention. It is a perspective view which shows the outline of the module applied to the refrigeration circuit of FIG. FIG. 3 is a plan view of the module of FIG. 2, where (a) is a top view, (b) is a front view, (c) is a side view, and (d) is a rear view. It is sectional drawing which follows the IV-IV line of Fig.3 (a). It is a figure which shows the state which joined one adapter to the heat exchange tube used for the module of FIG. It is sectional drawing which follows the VI-VI line of Fig.3 (a). It is sectional drawing which follows the VII-VII line of FIG.3 (c). It is a fragmentary sectional view shown in detail in the state which extended the pipe used for the module of FIG. FIG. 2 is a Mollier chart for explaining the operation of the refrigeration circuit of FIG. 1. It is a perspective view which shows the heat exchange tube of a modification.

Explanation of symbols

4 Circulation channel
14 Compressor
16 Heatsink
18 Evaporator
20 modules

Claims (6)

A compressor, a radiator, a high-temperature part of an internal heat exchanger, a decompressor, an evaporator, an accumulator, and the internal heat exchange inserted in a circulation flow path through which the refrigerant circulates and sequentially inserted in the flow direction of the refrigerant In the vapor compression refrigeration circuit with the low temperature part of the vessel,
The decompressor, the accumulator and the internal heat exchanger are formed integrally with each other ,
Comprising a superheat degree reducing means for exchanging heat between a liquid phase component of the refrigerant stored in the accumulator and a gas phase component of the refrigerant flowing out from a low temperature portion of the internal heat exchanger;
The degree of superheat reduction includes a pipe that is inserted into a portion of the circulation flow path that extends between a low temperature portion of the internal heat exchanger and the compressor and passes through a bottom portion of the accumulator,
The pipe has an inlet end and an outlet end connected to an inner wall surface of the accumulator, and a position of the outlet end of the pipe is higher than a position of the inlet end and a liquid of the refrigerant stored in the accumulator. A vapor compression refrigeration circuit characterized by being higher than the liquid level of the phase component .   The vapor compression refrigeration circuit according to claim 1, wherein the decompressor and the accumulator are adjacent to each other. 3. The vapor compression refrigeration circuit according to claim 1, wherein the degree of superheat reduction further includes a concavo-convex portion formed on at least one of an inner peripheral surface and an outer peripheral surface of the pipe. The vapor compression refrigeration circuit according to any one of claims 1 to 3, wherein the pipe has an oil return hole for sucking lubricating oil stored in the accumulator. Vapor compression refrigeration circuit according to any one of claims 1 to 4, wherein the refrigerant is CO _2. A vehicular air conditioning system comprising the vapor compression refrigeration circuit according to any one of claims 1 to 5 .

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