Internal heat exchanger

TECHNICAL FIELD

0001The present invention relates to an internal heat exchanger provided in a refrigeration cycle of a vehicular or building air conditioner.

BACKGROUND ART

0002In recent years, a natural refrigerant such as carbon dioxide having a low global warming potential is used in a refrigeration cycle in the air conditioner of this type so that even if the refrigerant leaks outside, the influence on environment is small.

0003In the refrigeration cycle, a lubricant for lubricating a compressor is discharged from the compressor together with the refrigerant.

0004Therefore, it is not possible to avoid a case that a portion of the lubricant adheres to an inner surface of a fluid path of a heat exchanger incorporated in a refrigeration cycle as an oil film, and this oil film deteriorates a heat exchange amount between a refrigerant flowing inside of the flow path and a pipe wall of the flow path.

0005Japanese Patent Application Laid-open No. <patcit id="pcit0001" dnum="JPH2293570B"><text>H2-293570</text></patcit> (hereinafter, Patent Document 1) for example proposes a refrigeration cycle having a compressor 101, a condenser 102, an accumulator 103, a decompression unit 104 and an evaporator 105, in which an oil separating unit is provided in a refrigerant inflow chamber of the condenser 102, and the separated oil is returned to the compressor 101 from an oil return passage 108 through a decompression valve 109.

0006However, the technique described in Patent Document 1 has an adverse possibility that a liquid refrigerant flows into the compressor 101.

0007Therefore, it is an object of the present invention to provide an internal heat exchanger capable of suppressing adhesion of an oil film to an inner surface of a flow path, preventing a heat exchange amount from being reduced, and preventing a liquid refrigerant from flowing into a compressor.

DISCLOSURE OF INVENTION

0008To achieve the above object, the invention according to claim 1 provides an internal heat exchanger provided in a refrigeration cycle comprising a radiator which discharges, to outside, heat of a refrigerant circulating in the cycle for cooling the refrigerant, an evaporator which allows the refrigerant circulating in the cycle to absorb heat of outside and which evaporates the refrigerant, a compressor which sucks a refrigerant flowing out from the evaporator, which compresses the refrigerant and discharges the same toward the radiator, and a decompression unit which decompresses the refrigerant flowing out from the radiator and which introduces the same to the evaporator, in which the internal heat exchanger includes a high pressure side flow path through which a high temperature and high pressure refrigerant flowing into the decompression unit from the radiator flows, and a low pressure side flow path through which a low temperature and low pressure refrigerant flowing into a suction side of the compressor from the evaporator flows, and in which heat is exchanged between the high temperature and high pressure refrigerant and the low temperature and low pressure refrigerant, wherein at least one of an inlet portion of the high pressure side flow path and an inlet portion of the low pressure side flow path is provided with oil separating unit which separates oil included in the refrigerant passing through the inlet portion.

0009Claim 2 provides the internal heat exchanger according to claim 1, wherein the inlet portion of the high pressure side flow path and the inlet portion of the low pressure side flow path are provided with a high pressure side inlet header and a low pressure side inlet header, respectively, and at least one of the high pressure side inlet header and the low pressure side inlet header is provided therein with the oil separating unit.

0010Claim 3 provides the internal heat exchanger according to claim 1 or 2, wherein the oil separating unit is provided at its downstream side with an oil returning mechanism which returns oil located on the side of one of the flow paths separated by the oil separating unit toward the other flow path.

BRIEF DESCRIPTION OF DRAWINGS

0011<ul id="ul0001" list-style="none" compact="compact"><li>[<figref idref="f0001">Fig. 1] Fig. 1</figref> is a circuit diagram showing an example of a conventional refrigeration cycle.</li><li>[<figref idref="f0002">Fig. 2] Fig. 2</figref> is a circuit diagram of a carbon dioxide refrigeration cycle having an internal heat exchanger according to a first embodiment of the present invention.</li><li>[<figref idref="f0003">Figs. 3] Figs. 3</figref> show a structure of the internal heat exchanger of the first embodiment of the present invention, where (a) is a front view and (b) is a sectional view taken along the line I-I' in (a).</li><li>[<figref idref="f0004">Figs. 4] Figs. 4</figref> show a structure of an internal heat exchanger according to a second embodiment of the present invention, where (a) is a front view, (b) is a sectional view taken along the line II-II' in (a), and (c) is a side view as viewed from the arrow III in (a).</li><li>[<figref idref="f0005">Figs. 5] Figs. 5</figref> show a structure of an internal heat exchanger according to a third embodiment of the present invention, where (a) is a front view, (b) is a sectional view taken along the line IV-IV' in (a), and (c) is a side view as viewed from the arrow V in (a).</li><li>[<figref idref="f0006">Fig. 6] Fig. 6</figref> is an exploded perspective view of an internal heat exchanger according to a fourth embodiment of the present invention.</li><li>[<figref idref="f0007">Fig. 7] Fig. 7</figref> is an exploded perspective view of an internal heat exchanger according to a fifth embodiment of the present invention.</li></ul>

BEST MODES FOR CARRYING OUT THE INVENTION

0012Embodiments of the present invention are explained below with reference to the drawings. An example in which the present invention is applied to a carbon dioxide refrigeration cycle for a vehicular air conditioner is explained.

(First Embodiment)

0013<figref idref="f0002">Fig. 2</figref> is a circuit diagram of a carbon dioxide refrigeration cycle having an internal heat exchanger according to a first embodiment.

0014The refrigeration cycle includes a compressor 1 which compresses a refrigerant, a radiator 2 which exchanges heat between outside air and the high temperature refrigerant whose pressure is increased by the compressor 1, an expansion valve (decompressing unit) 3 which decompresses the refrigerant cooled by the radiator 2, an evaporator 4 which evaporates the refrigerant decompressed by the expansion valve 3, an accumulator 5 which separates the refrigerant which passed through the evaporator 4 into gas and liquid and which sends only a vapor phase refrigerant to the compressor 1, and an internal heat exchanger 10 which exchanges heat between the high pressure refrigerant cooled by the radiator 2 and a low pressure refrigerant returning to the compressor 1.

0015The compressor 1 obtains a driving force from a motor or an engine (not shown), compresses a vapor phase carbon dioxide refrigerant (hereinafter, where appropriate, referred to as carbon dioxide or refrigerant), and discharges a high temperature and high pressure refrigerant.

0016The radiator 2 radiates heat of the high temperature and high pressure refrigerant discharged from the compressor 1 to outside air, thereby cooling the refrigerant to a temperature close to the outside air temperature. An electric fan is driven to blow outside air to the radiator 2. Heat is exchanged between the outside air blown by the electric fan and the high temperature and high pressure refrigerant passing through the radiator 2, thereby cooling the high temperature and high pressure refrigerant to a predetermined temperature.

0017The internal heat exchanger 10 exchanges heat between the refrigerant cooled by the radiator 2 and a low temperature and low pressure refrigerant evaporated by the evaporator 4, thereby further cooling the refrigerant which is sent from the radiator 2 to the expansion valve 3.

0018The expansion valve 3 expands (decompresses) a medium temperature and high pressure refrigerant which is cooled by the internal heat exchanger 10, and sends the same to the evaporator 4 as a low temperature and low pressure gaseous refrigerant.

0019The evaporator 4 is a heat exchanger which exchanges heat between a low temperature and low pressure refrigerant decompressed by the expansion valve 3 and air supplied from a blower fan (not shown) . The refrigerant whose temperature and pressure are reduced by the expansion valve 3 draws heat of supplied air and vaporizes (evaporates) when the refrigerant passes through the evaporator 4. The supplied air whose heat is absorbed by the refrigerant in the evaporator 4 is cooled and dehumidified and becomes air conditioned air, and is sent to a vehicle room.

0020The accumulator (gas/liquid separator) 5 separates the refrigerant discharged from the evaporator 4 into gas and liquid, sends out the gas phase refrigerant (gaseous refrigerant) into the internal heat exchanger 10, and temporarily stores the liquid phase refrigerant (liquid refrigerant).

0021In <figref idref="f0002">Fig. 2</figref>, the high temperature and high pressure carbon dioxide discharged from the compressor 1 exchanges heat with air while passing through the radiator 2 and the temperature of the carbon dioxide is lowered. The carbon dioxide whose temperature is lowered exchanges heat with a low temperature and low pressure refrigerant which returns to the compressor 1 while the carbon dioxide passes through the internal heat exchanger 10 and the temperature of the carbon dioxide is further lowered and the carbon dioxide is sent to the expansion valve 3. While the carbon dioxide passes through the expansion valve 3, the carbon dioxide expands and the temperature thereof is lowered and as a result, the temperature of the evaporator 4 provided downstream of the expansion valve 3 is lowered. Therefore, air passing through the evaporator 4 is cooled, water vapor included in this air is removed, and it is possible to cool and dehumidify air.

0022The low temperature carbon dioxide (low temperature and low pressure side refrigerant B) which passed through the evaporator 4 passes through the accumulator 5 and is sent to the internal heat exchanger 10. The carbon dioxide exchanges heat in the internal heat exchanger 10 with carbon dioxide (high temperature and high pressure side refrigerant A) which is sent out from the radiator 2 and which is still warm, and is again returned to the compressor 1 and compressed. The accumulator 5 also functions to prevent the liquid carbon dioxide from being sent to the compressor 1.

0023<figref idref="f0003">Figs. 3</figref> show a structure of the internal heat exchanger of the first embodiment, where (a) is a front view and (b) is a sectional view taken along the line I-I' in (a). The internal heat exchanger 10 exchanges heat between the high temperature and high pressure side refrigerant A flowing through the high pressure side flow path 11 and the low temperature and low pressure side refrigerant B flowing through a low pressure side flow path 12.

0024In the present embodiment, the high pressure side flow path 11 and the low pressure side flow path 12 have porous pipe portions 11c and 12c in which a plurality of rows of flow paths (not shown) each having a circular cross section are formed, and a refrigerant flows through each flow path.

0025In the present embodiment, the high pressure side flow path 11 has an inlet portion 11a and an outlet portion 11b which are respectively provided with a high pressure side inlet header 21 and a high pressure side outlet header 22. The low pressure side flow path 12 has an inlet portion 12a and an outlet portion 12b which are respectively provided with a low pressure side inlet header 31 and a low pressure side outlet header 32. These headers 21, 22, 31, and 32 are provided uprightly, and respectively connected to ends of the porous pipe portions 11c and 12c of the high pressure side flow path 11 and the low pressure side flow path 12. A high pressure side inlet pipe 21a and a low pressure side inlet pipe 31a are connected to upper ends (upstream sides) of the high pressure side inlet header 21 and the low pressure side inlet header 31, respectively. A high pressure side outlet pipe 22a and a low pressure side outlet pipe 32a are connected to lower ends (downstream sides) of the high pressure side outlet header 22 and the low pressure side outlet header 32, respectively.

0026An oil separating unit 50 is incorporated in each of the high pressure side inlet header 21 and the low pressure side inlet header 31 at upper positions therein. A mesh or a bunch made of metal, resin or fiber such as ceramic, or a porous body made of such material can be used as the oil separating unit 50. When a mesh is used as the oil separating unit and the refrigerant which flew into the headers 21, 31 passes through the oil separating unit, oil included in a vapor phase refrigerant adheres to the mesh, and this is separated into the vapor phase refrigerant and oil.

0027Since oil separated by the oil separating unit 50 has greater density than that of the refrigerant, the oil moves downward, and is stored in lower portions of the inlet headers 21 and 31 and flows toward the outlet headers 22 and 32 through flow paths provided below the porous pipe portions 11c and 12c of the high pressure side flow path 11 and the low pressure side flow path 12. That is, the refrigerant passes through the upper flow path and oil flows through the lower flow path and flows into the outlet headers 22 and 32. In this case, the flow path through which oil flows is limited to flow paths located below the porous pipe portions 11c and 12c, and this can prevent oil from adhering to an inner surface of the flow path through which the refrigerant flows. Therefore, it is possible to prevent the deterioration of the heat exchange amount which is caused by adhesion of oil to the inner surface of the flow path through which the refrigerant flows.

0028In the internal heat exchanger 10, heat is exchanged also in the above-described flow path through which oil flows. Therefore, when oil flows from the low pressure side inlet header 31 toward the outlet header 32, a liquid refrigerant which was melted in oil evaporates. Thus, it is possible to prevent the liquid refrigerant from being mixed into the compressor 1.

0029As a result of oil separation, the amount of standing oil in the internal heat exchanger 10 is reduced, oil returns into the compressor 1 more effectively, lubricating shortage in the compressor 1 is solved, and lifetime of the compressor 1 can be increased.

(Second Embodiment)

0030In the first embodiment, the adjacent headers 21, 32, 22, and 31 are separated from each other. However, when the adjacent headers 21, 32, 22, and 31 are adjacent to each other through one division wall, a structure of an internal heat exchanger 10B of a second embodiment shown in <figref idref="f0004">Figs. 4</figref> can be employed. <figref idref="f0004">Figs. 4</figref> show the structure of the internal heat exchanger 10B according to the second embodiment, where (a) is a front view, (b) is a sectional view taken along the line II-II' in (a), and (c) is a side view as viewed from the arrow III in (a).

0031In the present embodiment, since a refrigerant flows in a counterflow manner, the high pressure side inlet header 21 and the low pressure side outlet header 32 adjoin each other, and the high pressure side outlet header 22 and the low pressure side inlet header 31 adjoin each other.

0032In this internal heat exchanger 10B, the oil separating unit 50 is provided at an upper location in the high pressure side inlet header 21, the low pressure side inlet header 31 has no oil separating unit 50. Oil chambers 26 and 36 are respectively formed in a downstream side inner bottom portion of the high pressure side outlet header 22 and a downstream side inner bottom portion of the low pressure side inlet header 31. The oil chambers 26 and 36 are respectively partitioned from the upper side portion of the high pressure side outlet header 22 and the low pressure side inlet header 31 by division walls 25 and 35. These oil chambers 26 and 36 are in communication with each other through a communication hole (e.g., fine hole) 28 formed in a partition wall 27 which partitions the headers 22 and 31 from each other. The communication hole 28 has a decompression function. The high pressure side outlet pipe 22a is connected to the upper side portion of the high pressure side outlet header 22 on upper side of the partition wall 25 which defines the upper side of the oil chamber 26.

0033In the internal heat exchanger 10B having such a structure, oil separated by the oil separating unit 50 of the high pressure side inlet header 21 stays in a lower portion of the header 21 and flows toward the high pressure side outlet header 22 through a flow path located below the porous pipe 11c. The oil which flowed to the oil chamber 26 of the lower portion of the high pressure side outlet header 22 flows into the oil chamber 36 at a lower portion of the low pressure side inlet header 31 through the communication hole 28 having the decompression function, and flows into the low pressure side outlet header 32 through a flow path located below the porous pipe 12 from the oil chamber 36. The refrigerant and the oil are mixed in the low pressure side outlet header 32, and the refrigerant in which the oil is mixed from the low pressure side outlet pipe (not shown) flows into the compressor 1.

0034That is, in the present embodiment, the flow path located below the porous pipe 11c, the oil chamber 26 and the communication hole 28 function as an oil returning mechanism located downstream of the oil separating unit 50.

0035In the internal heat exchanger 10B according to the present embodiment, when a refrigerant flows through the porous pipes 11c and 12c, i.e., when a refrigerant flows from the high pressure side inlet header 21 to the high pressure side outlet header 22, and when the refrigerant flows from the low pressure side inlet header 31 to the low pressure side outlet header 32, since the refrigerant and the oil flow in a state where they are separated into an upper layer and a lower layer, it is possible to prevent the oil from adhering to the inner surface of the flow path in a range where the refrigerant flows, and it is possible to avoid a case that the heat exchange amount of the internal heat exchanger 10B is reduced by the adhesion of oil.

0036Further, it is possible to avoid a case that oil adheres to the evaporator 4 (see <figref idref="f0002">Fig. 2</figref>) connected between the high pressure side outlet header 22 and the low pressure side inlet header 31 and this deteriorates the heat exchange performance.

0037Since heat is exchanged also in a portion (lower flow path) of the internal heat exchanger 10B through which oil flows, a liquid refrigerant melted in the low pressure side oil evaporates, and it is possible to prevent the liquid refrigerant from being mixed into the compressor 1.

0038Since the stay of oil in the internal heat exchanger 10B is reduced by separation of oil, oil returns to the compressor 1 more effectively, lubrication shortage of the compressor 1 is solved, and the lifetime of the compressor 1 can be increased.

(Third Embodiment)

0039Although the counterflow is explained in the second embodiment, the present invention can also be applied to a parallel flow. <figref idref="f0005">Figs. 5</figref> show an internal heat exchanger 10C according to a third embodiment in which the invention is applied to the parallel flow. <figref idref="f0005">Fig. 5(a)</figref> is a front view of the internal heat exchanger of the third embodiment, (b) is a sectional view taken along the line IV-IV' in (a), and (c) is a side view as viewed from the arrow V in (a).

0040Since a refrigerant flows in the parallel manner in the present embodiment, the high pressure side inlet header 21 and the low pressure side inlet header 31 adjoins each other, and the high pressure side outlet header 22 and the low pressure side outlet header 32 adjoin each other.

0041In the internal heat exchanger 10C, the oil separating unit 50 is provided at an upper position in the high pressure side inlet header 21, and the low pressure side inlet header 31 has no oil separating unit 50. Oil chambers 26 and 36 are respectively provided in a downstream side inner bottom portion of the high pressure side inlet header 21 and a downstream side inner bottom portion of the low pressure side inlet header 31. The oil chambers 26 and 36 are respectively partitioned from the upper side portion of the high pressure side inlet header 21 and the low pressure side inlet header 31 by division walls 25 and 35. These oil chambers 26 and 36 are in communication with each other through a communication hole (e. g. , fine hole) 28 provided in a partition wall 27 which partitions the headers 21 and 31 from each other. The communication hole 28 has a decompression function.

0042In the internal heat exchanger 10C having this structure, oil separated by the oil separating unit 50 in the high pressure side inlet header 21 stays in the lower oil chamber 26 of the header 21, and flows into the oil chamber 36 of the low pressure side inlet header 31 through the communication hole 28 having the decompression function as it is. Next, the oil passes through a flow path located below the porous pipe 12 from the oil chamber 36 and flows into the low pressure side outlet header 32. The oil and the refrigerant are mixed in the low pressure side outlet header 32, and the oil mixture coming from the low pressure side outlet pipe (not shown) flows into the compressor 1.

0043That is, in the present embodiment, the oil chamber 26 and the communication hole 28 function as the oil returning mechanism.

0044Also in the present embodiment, the same effect as that of the internal heat exchanger 10B according to the second embodiment can be obtained.

0045In the internal heat exchanger 10B according to the second embodiment shown in <figref idref="f0004">Fig. 4</figref>, the high pressure side inlet header 21 and the low pressure side outlet header 32 immediately adjoin each other, and the high pressure side outlet header 22 and the low pressure side inlet header 31 immediately adjoin each other (they are integrally formed in the illustrated example). Therefore, heat is exchanged also between the adjacent headers 21 and 32, and between the adjacent headers 22 and 31.

0046Also in the internal heat exchanger 10C according to the third embodiment shown in <figref idref="f0005">Fig. 5</figref>, the high pressure side inlet header 21 and the low pressure side inlet header 31 immediately adjoin each other, and the high pressure side outlet header 22 and the low pressure side outlet header 32 immediately adjoin each other (they are integrally formed in the illustrated example). Therefore, heat is exchanged also between the adjacent headers 21 and 31, and between the adjacent headers 22 and 32.

0047Concerning the communication hole 28 having the decompression function provided in each of the second and third embodiments, the headers 21, 22, and 31 can be provided at their outsides with elements having the same functions as the decompression function and these headers may be used instead of the communication hole 28. For example, a communication pipe having a decompression function which brings the oil chambers 26 and 36 into communication with each other may be provided outside of the header.

0048If the fact that the communication pipes may be provided outside of the headers 21, 22, and 31 is taken into account, the structure of the oil chambers 26 and 36 and the communication pipe may be applied also to an internal heat exchanger of a type in which the high pressure and low pressure headers 21, 22, 31, and 32 are separated from each other as shown in <figref idref="f0003">Fig. 3</figref>.

(Fourth Embodiment)

0049Next, an embodiment in which the oil returning structure is simplified is explained. <figref idref="f0006">Fig. 6</figref> is an exploded perspective view of an internal heat exchanger according to a fourth embodiment, and particularly shows the oil returning structures provided in the high pressure side inlet header 21 and the low pressure side outlet header 32. Explanations of the same structures and effects as those of other embodiments will be omitted, and only structures and effects specific to the present embodiment are explained.

0050In the internal heat exchanger 10D according to the present embodiment, since a refrigerant flows in the counterflow manner as in the second embodiment, the high pressure side inlet header 21 and the low pressure side outlet header 32 are adjacent to each other, and a high pressure side outlet header and a low pressure side inlet header (both not shown) are adjacent to each other.

0051In this internal heat exchanger 10D, an oil separating unit (see <figref idref="f0003">Fig. 3(b)</figref>) is provided at an upper position in the high pressure side inlet header 21. The low pressure side inlet header (not shown) has no oil separating unit.

0052A patch end 41 and a plate 42 are provided at lower ends of the adjacent high pressure side inlet header 21 and low pressure side outlet header 32, and the adjacent two headers are connected to each other. The patch end 41 is formed into a box-frame shape. The patch end 41 is provided at its bottom with a groove 41a through which the high pressure side inlet header 21 and the low pressure side outlet header 32 are communicated with each other, and an outlet hole 41b for discharging a refrigerant from a lower end of the low pressure side outlet header 32. A cross section of the groove 41a has a substantially recess shape, and its end is in communication with the outlet hole 41b.

0053A low pressure side outlet pipe 32a is connected to the outlet hole 41b of the patch end 41. The patch end 41 can be formed by cutting, press, forging or the like.

0054By assembling the patch end 41 and the plate 42 to the lower ends of the high pressure side inlet header 21 and the low pressure side outlet header 32, the lower end of the high pressure side inlet header 21 is shut off, and the lower end of the low pressure side outlet header 32 and the low pressure side outlet pipe 32a are brought into communication with each other through the groove 41a. At the same time, the adjacent high pressure side inlet header 21 and the low pressure side outlet header 32 are connected and fixed to each other through the patch end 41 and the plate 42.

0055According to the internal heat exchanger 10D of the present embodiment, oil separated by the oil separating unit (not shown) provided in the high pressure side inlet header 21 is accumulated in the lower portion of the high pressure side inlet header 21, and the oil flows from here to the lower portion of the low pressure side outlet header 32 through the groove 41a of the patch end 41. A refrigerant and oil flowing through the porous pipe 12 in the lower portion of the low pressure side outlet header 32 are mixed, and the refrigerant in which oil is mixed is discharged from the low pressure side outlet pipe 32a and is sent to the compressor 1.

0056That is, in the present embodiment, the patch end 41, the plate 42 and the groove 41a function as the oil returning mechanism provided downstream of the oil separating unit.

0057According to the internal heat exchanger 10D of the present embodiment, oil can be returned by the simple structures formed by the patch end 41 and the plate 42, the number of parts can be reduced and the costs can be reduced.

0058Although the oil returning structure formed by the patch end 41 and the plate 42 is provided at the lower portions of the high pressure side inlet header 21 and the low pressure side outlet header 32 in the present embodiment, the same oil returning structure may be provided at the high pressure side outlet header and the low pressure side inlet header (both not shown) and oil may be returned from the lower portion of the low pressure side inlet header to the high pressure side outlet header. One or both of the headers may be provided with the oil returning structure.

0059Although the one groove 41a is formed in the bottom of the patch end 41 in the present embodiment, a plurality of grooves 41a may be formed. A groove having the decompression function may be formed by reducing the cross-sectional area.

(Fifth Embodiment)

0060<figref idref="f0007">Fig. 7</figref> is an exploded perspective view of an internal heat exchanger according to a fifth embodiment, and especially shows oil returning structures provided in the high pressure side inlet header 21 and the low pressure side inlet header 32. Explanations of the same structures and effects as those of other embodiments will be omitted, and only structures and effects specific to the present embodiment are explained.

0061According to the internal heat exchanger 10E of the present embodiment, a refrigerant flows in the parallel flow manner as in the third embodiment, the high pressure side inlet header 21 and the low pressure side inlet header 32 are disposed adjacent to each other, and the high pressure side outlet header and the low pressure side outlet header (both not shown) are also disposed adjacent to each other.

0062In the internal heat exchanger 10E, oil separating unit (see <figref idref="f0003">Fig. 3(b)</figref>) (not shown) is provided at an upper position in the high pressure side inlet header 21. The low pressure side inlet header 32 has no oil separating unit.

0063A patch end 43 and a plate 42 are provided at lower ends of the adjacent high pressure side inlet header 21 and low pressure side inlet header 32, and the adjacent two headers are connected to each other. The patch end 43 is formed into a box-frame shape. The patch end 43 is provided at its bottom with a groove 43a through which the high pressure side inlet header 21 and the low pressure side inlet header 32 are communicated with each other. A cross section of the groove 43a has a recess shape.

0064By assembling the patch end 43 and the plate 42 to the lower ends of the high pressure side inlet header 21 and the low pressure side inlet header 32, the lower ends of the high pressure side inlet header 21 and the low pressure side inlet header 32 are shut off, and the lower ends of the headers are in communication with each other through the groove 43a. At the same time, the adjacent high pressure side inlet header 21 and low pressure side inlet header 32 are connected and fixed to each other through the patch end 43 and the plate 42.

0065According to the internal heat exchanger 10E of the present embodiment, oil separated by the oil separating unit (not shown) provided in the high pressure side inlet header 21 is accumulated in the lower portion of the header 21, and the oil flows into the lower portion of the low pressure side inlet header 32 through the groove 43a of the patch end 43, and flows into the low pressure side outlet header (not shown) through a flow path of the porous pipe 12 located below the low pressure side inlet header 32. A refrigerant and oil are mixed in the low pressure side outlet header, and the refrigerant in which oil is mixed is discharged from the low pressure side outlet pipe (not shown) and is sent to the compressor 1.

0066That is, in the present embodiment, the patch end 43, the plate 42 and the groove 43a function as the oil returning mechanism provided downstream of the oil separating unit.

0067Also in the internal heat exchanger 10E according to the present embodiment, oil can be returned by the simple structures formed by the patch end 43 and the plate 42, the number of parts can be reduced and the costs can be reduced.

0068In the present embodiment, the oil returning structure formed by the patch end 43 and the plate 42 is provided at the lower portions of the high pressure side inlet header 21 and the low pressure side inlet header 32, but the oil returning structure as shown in <figref idref="f0007">Fig. 7</figref> or <figref idref="f0006">6</figref> may be provided at the high pressure side outlet header (not shown) and the low pressure side outlet header (not shown), and oil may be returned to the low pressure side outlet header from the lower portion of the high pressure side outlet header. One or both of the headers may be provided with the oil returning structure in this manner.

0069Although one groove 43a is formed in the bottom of the patch end 43 in the present embodiment, a plurality of grooves 43a may be formed. A groove having the decompression function may be formed by reducing the cross-sectional area.

INDUSTRIAL APPLICABILITY

0070According to the present invention, it is possible to provide an internal heat exchanger capable of suppressing the adhesion of oil film on an inner surface of a flow path, preventing a heat exchange amount from being reduced, and preventing a liquid refrigerant from flowing into a compressor.