JP5959209B2 - Internal heat exchanger - Google Patents

Description

  The present invention relates to an internal heat exchanger in a refrigeration cycle in which refrigerant is circulated in four steps of evaporation, compression, condensation, and expansion.

  In general, a refrigerant circuit of a vehicle air conditioner forms a refrigeration cycle in which a refrigerant such as carbon dioxide is circulated in four steps of evaporation, compression, condensation, and expansion. In this refrigerant circuit, an internal heat exchanger that exchanges heat between a high-temperature and high-pressure refrigerant and a low-temperature and low-pressure refrigerant is used. This internal heat exchanger performs heat exchange between the high-temperature and high-pressure refrigerant condensed by the condenser and the low-temperature and low-pressure refrigerant returned to the compressor.

  In this type of conventional internal heat exchanger, a high-pressure side flat tube and a low-pressure side flat tube, each of which has a refrigerant flow path, are laminated and brazed. Further, in this type of internal heat exchanger, in order to lengthen the refrigerant flow path in a limited space, the high-pressure side flat tube and the low-pressure side flat tube are formed in a U shape, The refrigerant inlet side end and the refrigerant outlet side end of the side flat tube are joined to the header tank (see, for example, Patent Documents 1 and 2).

  Among these, in the thing of patent document 1, the cross section which the U shape cut | disconnected by the plane orthogonal to the refrigerant | coolant distribution direction in a header tank forms in the shape which consists of a curve which connects these three straight parts. The high-pressure side strip tube is placed inside the low-pressure side strip tube and molded.

  Moreover, in the thing of patent document 2, the tube body which brazed the 1st flow path layer of the high voltage | pressure side which respectively arranged the refrigerant flow path and the 2nd flow path layer of the low voltage | pressure side is bent in U shape. To form an internal heat exchanger.

JP 2002-340485 A (Claim 4, paragraphs 0016, 0035, FIG. 3) JP 2002-98486 (paragraph 0090, FIG. 8)

  However, in the U-shaped internal heat exchanger described in Patent Document 1, a cross section in which the U-shape is cut by a plane perpendicular to the refrigerant flow direction in the header tank connects the three straight portions to each other. Since it is formed in a curved shape, it is necessary to widen the occupied space in order to lengthen the refrigerant flow path. Moreover, since the refrigerant flow path is composed of three straight portions and a curve connecting them, there is a risk of refrigerant pressure loss.

  In addition, the U-shaped internal heat exchanger described in Patent Document 2 has a curvilinear portion smaller than that described in Patent Document 1, so that pressure loss of the refrigerant can be suppressed. However, the heat exchanger of Patent Document 2 is bent by bending because a tube body in which the first flow path layer on the high pressure side and the second flow path layer on the low pressure side are brazed is formed into a U shape. There is a possibility that distortion is accumulated in the portion, and this distortion causes an increase in pressure loss due to breakage or flow path deformation.

  The present invention has been made in view of the above circumstances, and provides a small-sized internal heat exchanger excellent in heat exchange efficiency with suppressed pressure loss.

In order to achieve the above object, an internal heat exchanger according to the present invention is used in a refrigeration cycle in which refrigerant circulates in four strokes of evaporation, compression, condensation, and expansion, and a high-pressure side in which high-pressure side refrigerant flow paths are arranged. An internal heat exchanger comprising a flat tube and a low-pressure side flat tube in which low-pressure side refrigerant flow paths are arranged, wherein the high-pressure side flat tube is bent in a U shape and has refrigerant on both ends. Both the inlet side end and the refrigerant outlet side end are provided in the same direction so as to incline in a straight line through the arc portion, the low-pressure side flat tube is bent in a U shape, and the refrigerant flow at both ends is provided. An inlet side end and a refrigerant outflow side end are provided to be inclined in a straight line in opposite directions via an arc portion, and the high pressure side flat tube is disposed inside the low pressure side flat tube, and the high pressure side each refrigerant flow inlet end and a coolant outlet side end header pie flat tube and the low-flat tube Through the slits provided in the inserted in the header pipe, the header pipe being connected to the coolant inlet side end portion of the high-pressure side flat tubes, are connected to the refrigerant flow outlet side end portion of the low-pressure side flat tubes A header pipe connected to a refrigerant outlet side end of the high-pressure side flat tube and a refrigerant of the low-pressure side flat tube A header pipe connected to the end on the inlet side is connected by a connector that is positioned substantially on the same line and can be attached to the expansion valve. The high pressure side flat tube, the low pressure side flat tube , the header pipe, and the connector are made of brazing material. it is integrally joined via, the amount insertion into the header pipe of the refrigerant inlet port side end portion of the high pressure side flat tubes and the low-pressure side flat tubes, der 15% to 35% of the inner diameter of the header pipe The thickness of the high-pressure side flat tube and the low-pressure side flat tube is 8 mm or less, and the ratio of the thickness and width of the flat tube is 1: 4 to 1: 6, and the bending radius of the high-pressure side flat tube is (R), the relationship between the thickness (t1) of the high-pressure side flat tube and the thickness (t2) of the low-pressure side flat tube is 2.5 ≦ R / (t1 + t2) /2≦4.5, and 1 ≦ t2 / t1 ≦ 3/2 (Claim 1).

  With this configuration, the high-pressure side flat tube and the low-pressure side flat tube are bent in a U shape in advance, and distortion is accumulated in the bent portion by bending, but the high pressure side flat tube bent in the U shape in advance. Distortion is removed by the annealing effect by heating when brazing the tube and the low-pressure side flat tube.

The present invention smell Te, the insertion amount is less than 15% of the inner diameter of the header pipe, clogging flows are braze the refrigerant flow path of the flat tube. Also, if the insertion amount is larger than 35% of the inner diameter of the header pipe, the refrigerant turbulently flows at the portion flowing from the header pipe to the flat pipe, and the pressure loss increases. Increases beyond the pressure loss caused by.

According to the first aspect of the present invention, the brazing material does not flow into the refrigerant flow path of the flat tube and clogging occurs, and the turbulent flow of the refrigerant flowing into the flat tube from the header pipe is suppressed. Can do.

In the present invention, when the thickness of the high-pressure side flat tube and the low-pressure side flat tube exceeds 8 mm, the refrigerant present at a position away from the surface where the high-pressure side and low-pressure side flat tubes contact each other is exchanged with the ambient temperature. As a result, it becomes difficult to obtain the desired heat exchange performance, resulting in a large variation in performance. On the other hand, when the thickness of the flat tube is closer than 4 times the width, the disturbance becomes large and the variation in performance increases. When the thickness of the flat tube is more than 6 times the width, the refrigerant does not flow properly to each flow channel of the flat tube, and the refrigerant concentrates in a specific flow channel and the heat exchange capability decreases.

According to invention of Claim 1, the variation in heat exchange performance can be suppressed, and heat exchange performance can be stabilized.

In this invention, when the ratio of the bending radius (R) of the high-pressure side flat tube to the thickness (t1) of the high-pressure side flat tube and the thickness (t2) of the low-pressure side flat tube is less than 2.5, the ratio As the value becomes smaller than 2.5, the elongation rate outside the flat tube increases, cracks and channel collapse occur, and the pressure loss increases. Moreover, when the said ratio is larger than 4.5, size will become huge and processing efficiency will fall.

According to invention of Claim 1, while being able to suppress a pressure loss, size reduction of an apparatus and improvement of processing efficiency can be aimed at.

In the present invention, the area (A1) of the refrigerant flow path arranged in the high-pressure side flat tube and the area (A2) of the refrigerant flow path provided in the low-pressure side flat pipe are 1 ≦ A2 / A1. It is better that ≦ 4 (Claim 2 ).

  When the area ratio is less than 1 and the area (A2) of the refrigerant flow path provided in the low-pressure side flat tube becomes larger, the flatness is obtained when the high-pressure side flat tube is taken as a reference under the same refrigerant mass flow rate. Since the cross-sectional area of the flow path is small with respect to the volume of the refrigerant that is going to pass through the pipe, the friction between the refrigerant and the flat pipe increases, the pressure loss increases, and the efficiency of the refrigeration cycle decreases. Moreover, when the low-pressure side flat tube is taken as a reference, the flow passage cross-sectional area of the high-pressure side flat tube is too large, causing a pressure drop due to the volume expansion of the refrigerant, resulting in a pressure loss and improving the efficiency of the refrigeration cycle. Reduce. Further, when the area ratio exceeds 4 and the area (A1) of the refrigerant flow path arranged in the high pressure side flat tube is large, the reverse of the above occurs and the efficiency of the refrigeration cycle is reduced.

Further, in the present invention, the header pipes is better brazing material is clad preferred (claim 3). Thereby, it is possible to easily and reliably braze the header pipe to the high-pressure side and low-pressure side flat tubes.

  Since the present invention is configured as described above, the following effects can be obtained.

(1) According to the first aspect of the present invention, the high-pressure side flat tube and the low-pressure side flat tube are bent in a U shape in advance, and distortion is accumulated in the bent portion by the bending process. The header pipe connected to the refrigerant inlet side end portion and the refrigerant outlet side end portion of the high pressure side flat tube and the low pressure side flat tube , which are connected by the connector, can be brazed integrally. Since the distortion is removed by the annealing effect due to the heating, durability can be improved and downsizing can be achieved.

(2) According to the invention described in claim 1 , the brazing material does not flow into the refrigerant flow path of the flat tube and clogging occurs, and the disturbance of the refrigerant flowing into the flat tube from the header pipe Since the flow can be suppressed , the pressure loss of the refrigerant can be further suppressed and the heat exchange efficiency can be improved.

(3) According to the invention described in claim 1 , since the variation in heat exchange performance can be suppressed and the heat exchange performance can be stabilized , the heat exchange efficiency can be further improved.

(4) According to the invention described in claim 1 , the pressure loss can be further suppressed, and the apparatus can be downsized and the processing efficiency can be improved.

(5) According to invention of Claim 2 , in addition to said (1)-(4), the improvement of the efficiency of the refrigerating cycle provided with the internal heat exchanger can be aimed at.

It is a schematic block diagram which shows the piping state of the internal heat exchanger which concerns on this invention. It is a front view which shows an example of the internal heat exchanger which concerns on this invention. It is a top view of the said internal heat exchanger. It is a right view of the said internal heat exchanger. It is the I section enlarged view (a) of FIG. 2, and the II section enlarged view (b) of FIG. It is an enlarged front view which shows the bending part of the high voltage | pressure side flat tube and low pressure side flat tube in this invention. It is an expanded sectional view which follows the III-III line of FIG. It is an expanded sectional view (a) of a high-pressure side flat tube in this invention, and an expanded sectional view (b) of a low-pressure side flat tube. It is a front view which shows the state before joining of the said high voltage | pressure side flat tube and a low voltage | pressure side flat tube. It is a piping diagram which shows an example of the piping structure of the internal heat exchanger which concerns on this invention. It is a piping diagram which shows the example of another piping structure of the internal heat exchanger which concerns on this invention.

    Embodiments of an internal heat exchanger according to the present invention will be described below in detail with reference to the accompanying drawings. Here, the case where the internal heat exchanger which concerns on this invention is applied to the refrigerant circuit of a vehicle air conditioner is demonstrated.

  The vehicle air conditioner moves the low temperature side heat to the high temperature side and uses the cold heat and heat for air conditioning. As shown in FIG. 1, the evaporator 1, the compressor 2, the condenser 3, and the expansion valve 4 are used. However, the circulation of the refrigerant to the internal heat exchanger 6 according to the present invention is added to a general refrigeration cycle in which the refrigerant is circulated through the pipe 5.

  The vehicle air conditioner operates as follows. That is, the refrigerant returned from the evaporator 1 is sucked into the compressor 2 through the internal heat exchanger 6 and compressed at high pressure. Next, the refrigerant discharged from the compressor 2 is sent to the condenser 3. The refrigerant sent to the condenser 3 is liquefied through heat exchange with the outside air, and reaches the expansion valve 4 via the internal heat exchanger 6. Next, the refrigerant is decompressed in the expansion valve 4 in which the evaporation temperature and flow rate can be electronically controlled. Thereafter, the refrigerant reaches the evaporator 1. Finally, the liquid refrigerant supplied to the evaporator 1 absorbs heat and becomes a gaseous refrigerant. The space in which the evaporator 1 is provided is cooled independently by the heat absorption of the refrigerant. And a refrigerant | coolant is attracted | sucked by the compressor 2 via the internal heat exchanger 6 from the evaporator 1, returns, and a circulation driving | operation is repeated.

  As described above, the internal heat exchanger 6 according to the present invention is connected between the condenser 3 and the expansion valve 4 and between the evaporator 1 and the compressor 2. The internal heat exchanger 6 is for exchanging heat between the high-pressure refrigerant flowing into the expansion valve 4 of the refrigeration cycle and the low-pressure refrigerant sucked by the compressor 2. Here, the high-pressure side refrigerant is a refrigerant that flows from the outflow side of the condenser 3 to the inflow side of the expansion valve 4, and the low-pressure side refrigerant is that from the outflow side of the evaporator 1 to the inflow side of the compressor 2. It is a flowing refrigerant.

  Next, the internal heat exchanger 6 will be described with reference to FIGS. As shown in FIG. 9, the internal heat exchanger 6 includes a high-pressure side flat tube 10 and a low-pressure side flat tube 20 that are each bent in advance in a U shape, and the high-pressure side flat tube 10 is a low-pressure side flat tube. 20 and at least the refrigerant flow of the refrigerant inlet side end portions 13 and 23 and the refrigerant outlet side end portions 14 and 24 of the high pressure side flat tube 10 and the low pressure side flat tube 20, respectively. In a state where the inlet side end portions 13 and 23 are inserted into the header pipes 30A to 30D through the slits 31 provided in the header pipes 30A to 30D, the high pressure side flat tube 10, the low pressure side flat tube 20, and the header pipe 30A-30D is brazed. In addition, it is more preferable to use what the brazing | wax material is clad for header pipe 30A-30D.

  In this case, the header pipe 30A that connects the refrigerant inlet side end 13 of the high-pressure side flat tube 10 and the header pipe 30D that connects the refrigerant outlet side end 24 of the low-pressure flat tube 20 have the mounting holes 41. The alloy connectors 40 are arranged in the vertical direction. A header pipe 30B connecting the refrigerant outlet side end 14 of the high pressure side flat tube 10 and a header pipe 30C connecting the refrigerant inlet side end 23 of the low pressure side flat tube 20 are arranged in the horizontal direction by the connector 40. Has been.

  The high-pressure side flat tube 10 and the low-pressure side flat tube 20 are each formed of an extruded product made of aluminum alloy, and the high-pressure side flat tube 10 is formed with six refrigerant channels 11 via partition walls 12. The low-pressure side flat tube 20 is formed with eight refrigerant channels 21 through partition walls 22 (see FIGS. 7 and 8). In addition, an uneven strip is provided on the inner wall surface of the refrigerant flow path 11 of the high-pressure side flat tube 10. Since the contact area can be increased by providing the uneven strips in this way, the efficiency of heat transfer can be increased.

  Further, the high-pressure side flat tube 10 has a refrigerant inlet side end portion 13 and a refrigerant outlet side end portion 14 both of which are bent in a U-shape, both in the same direction (left direction in the figure) via an arc portion. The refrigerant inlet side end 13 and the refrigerant outlet side end 14 are inserted into the header pipes 30A and 30B through slits 31 provided in the header pipes 30A and 30B, respectively. Has been.

  On the other hand, in the low-pressure side flat tube 20, the refrigerant inlet side end 23 and the refrigerant outlet side end 24 on both ends bent in a U-shape are provided so as to incline in a straight line through arc portions in opposite directions. The refrigerant inlet side end 23 and the refrigerant outlet side end 24 are inserted into the header pipes 30C and 30D via slits 31 provided in the header pipes 30C and 30D, respectively.

  In this case, the insertion amount S1 of the refrigerant inlet side end 13 of the high-pressure side flat tube 10 into the header pipe 30A is set to 15% to 35% of the inner diameter D1 of the header pipe 30A (FIG. 5). (See (a)). The insertion amount S2 into the header pipe 30C of the refrigerant inlet side end 23 of the low-pressure side flat tube 20 is set to 15% to 35% of the inner diameter D2 of the header pipe 30C (FIG. 5 ( b)).

  As described above, the insertion amounts S1 and S2 of the refrigerant inlet side end portions 13 and 23 of the high-pressure side flat tube 10 and the low-pressure side flat tube 20 into the header pipes 30A and 30C are used as the inner diameter D1 of the header pipes 30A and 30C. The reason for setting D2 to 15% to 35% is based on the evaluation experiment shown in Table 1.

In other words, the insertion amount of the flat tube to the inner diameter of the header pipe is 10%, 15%, 20%, 25%, 30%, 35%, 40%, 50%, and whether the flat tube is clogged (○, ×) When the presence / absence of increase in pressure loss (◯, ×) with the same area circular pipe as a reference was examined, the results shown in Table 1 were obtained. The experiment was performed under conditions equivalent to a vehicle speed of 10 km / hr.

  From the above results, when the insertion amounts S1, S2 are less than 15% of the inner diameters D1, D2 of the header pipes 30A, 30C, the brazing material flows into the refrigerant channels 11, 21 of the high-pressure side and low-pressure side flat tubes 10, 20. Clogging occurs. Further, when the insertion amounts S1 and S2 are larger than 35% of the inner diameters D1 and D2 of the header pipes 30A and 30C, the refrigerant is disturbed in the portions flowing from the header pipes 30A and 30C to the high-pressure side and low-pressure side flat tubes 10 and 20. It has been found that the flow loss causes an increase in pressure loss that increases beyond the pressure loss caused by a typical circular tube.

  In the present embodiment, the thickness t1 of the high-pressure side flat tube 10 and the thickness t2 of the low-pressure side flat tube 20 are 8 mm or less, and the ratio between the thicknesses t1 and t2 of both the flat tubes 10 and 20 and the width. Is set to 1: 4 to 1: 6.

  As described above, the thicknesses t1 and t2 of the high-pressure side and low-pressure side flat tubes 10 and 20 are set to 8 mm or less, and the ratio of the thicknesses t1 and t2 of both the flat tubes 10 and 20 to the width is 1: 4 to The reason for setting 1: 6 is based on the evaluation experiments shown in Tables 2 and 3.

That is, when the variation of the heat exchange performance when the thickness of the flat tube was 2 mm, 5 mm, 7 mm, 8 mm, and 10 mm was examined, the results shown in Table 2 were obtained. The experiment was performed under conditions equivalent to a vehicle speed of 10 km / hr.

  From the above results, when the thickness of the flat tubes 10 and 20 is 10 mm exceeding 8 mm, the refrigerant present at a position away from the surface where the high-pressure side and low-pressure side flat tubes contact each other exchanges heat with the ambient temperature. It was found that the disturbance became large, it was difficult to obtain the heat exchange performance as intended, and the variation in performance became large.

Next, the heat exchange performance when the ratio of thickness t1, t2 and width of the flat tubes 10, 20 is 1: 3, 1: 4, 1: 5, 1: 6, 1: 6, 1: 8. As a result, the results shown in Table 3 were obtained. The experiment was performed under conditions equivalent to a vehicle speed of 10 km / hr.

  From the above results, it was found that when the ratio of the thicknesses t1 and t2 of the flat tubes 10 and 20 to the width is 1: 3 which is closer to 1: 4 (4 times), the disturbance is increased and the variation in performance is increased. . Further, when the ratio of the thicknesses t1 and t2 of the flat tubes 10 and 20 to the width is 1: 7 or 1: 8 far from 1: 6 (six times), the refrigerant flows into each flow path of the flat tubes 10 and 20. It was found that the refrigerant flow concentrated in a specific flow path and the heat exchange capacity was lowered without a good flow split.

  In addition, as shown in FIG. 6, the bending radius of the high-pressure side flat tube 10 is R, and whether the flat tube is broken or not in relation to the thickness t1 of the high-pressure side flat tube 10 and the thickness t2 of the low-pressure side flat tube. When (○, ×) and an evaluation experiment on processing efficiency and size were performed, the results shown in Tables 4 and 5 were obtained.

That is, whether R / (t1 + t2) / 2 is 1, 2, 2.5, 3, 4, 4.5, 5, 6 or not (◯, x) and whether or not the processing efficiency and size are acceptable. When an evaluation experiment was performed on (◯, ×), the results shown in Table 4 were obtained. The experiment was performed under conditions equivalent to a vehicle speed of 10 km / hr.

  From the above results, when the ratio of the bending radius R of the high-pressure side flat tube to the thickness t1 of the high-pressure side flat tube 10 and the thickness t2 of the low-pressure side flat tube 20 is smaller than 2.5, the ratio is smaller than 2.5. It has been found that the elongation rate outside the flat tube becomes higher, causing cracks and channel collapse and increasing the pressure loss. Further, when the ratio is larger than 4.5, the shape becomes easy to process, but the size becomes enormous. Further, it was found that when the bending R is increased at a predetermined heat exchange rate, bending for branching the header pipe becomes more difficult and the processing efficiency is lowered.

Next, in the case where t2 / t1 is 0.5, 1, 1.5, 2, 3, whether the high-pressure side flat tube 10 (thickness t1) and the low-pressure side flat tube 20 (thickness t2) are damaged (◯ , X) When an evaluation experiment was conducted, results shown in Table 5 were obtained. The experiment was performed under conditions equivalent to a vehicle speed of 10 km / hr.

  As a result of the evaluation experiment, the relationship among the bending radius R of the high-pressure side flat tube 10, the thickness t1 of the high-pressure side flat tube 10 and the thickness t2 of the low-pressure side flat tube 10 is 2.5 ≦ R / (t1 + t2) / 2. It was found that ≦ 4.5 and 1 ≦ t2 / t1 ≦ 3/2 are preferable.

  Further, the presence / absence of pressure loss (in relation to the area (A1) of the refrigerant flow path 11 arranged in the high pressure side flat tube 10 and the area (A2) of the refrigerant flow path 21 provided in the low pressure side flat tube 20) The results shown in Table 6 were obtained when ◯ and X) were examined.

  That is, the area ratio (A2 / A1) of the area (A1) of the refrigerant flow path 11 arranged in the high pressure side flat tube 10 and the area (A2) of the refrigerant flow path 21 provided in the low pressure side flat pipe 20 is , 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4 and 5 were evaluated for the presence or absence of pressure loss (O, X). The results shown were obtained.

The experiment was performed under conditions equivalent to a vehicle speed of 10 km / hr.

  As a result of the evaluation experiment, pressure loss may occur when the area ratio (A2 / A1) is 0.5 smaller than 1 and when the area ratio (A2 / A1) is 5 larger than 4. understood. That is, when the area ratio (A2 / A1) is smaller than 1, the volume of the refrigerant that is about to pass through the flat tubes 10 and 20 when the high-pressure side flat tube 10 is taken as a reference under the flow rate of the same refrigerant mass. On the other hand, since the flow path cross-sectional area is small, the friction between the refrigerant and the flat tubes 10 and 20 increases, the pressure loss increases, and the heat exchange efficiency decreases. Further, when the low-pressure side flat tube 20 is taken as a reference, the flow passage cross-sectional area of the high-pressure side flat tube 10 is too large, causing a pressure drop due to the volume expansion of the refrigerant, resulting in a pressure loss and heat exchange efficiency. Reduce. Moreover, when the said area ratio (A2 / A1) exceeded 4 and it was large, it turned out that the reverse of the above-mentioned happen and heat exchange efficiency falls. Therefore, it is preferable that 1 ≦ A2 / A1 ≦ 4.

  In order to produce the internal heat exchanger 6 of the above embodiment, first, as shown in FIG. 9, the high-pressure side flat tube 10 and the low-pressure side flat tube 20 are separately bent and bent into a U shape, Both ends of the high-pressure side flat tube 10 and the low-pressure side flat tube 20 are bent as described above to process the refrigerant inlet side end portions 13 and 23 and the refrigerant outlet side end portions 14 and 24. In this case, as a method of bending the high-pressure side flat tube 10 and the low-pressure side flat tube 20, for example, there is a roll bender method. The roll bender is a method in which three rolls are arranged in a triangle, and the high pressure side flat tube 10 or the low pressure side flat tube 20 passing between the rolls is continuously pressed and rotated to bend.

  Next, as shown in FIG. 9, the high-pressure side flat tube 10 bent into a U shape as described above is disposed inside the low-pressure side flat tube 20. Then, the refrigerant inlet side end 13 of the high pressure side flat tube 10 is inserted into the header pipe 30A through the slit 31 provided in the header pipe 30A, and the refrigerant outlet side end 14 of the high pressure side flat tube 10 is inserted. It inserts into the header pipe 30B through the slit 31 provided in the header pipe 30B. At this time, the insertion amount S1 of the refrigerant inlet side end 13 of the high pressure side flat tube 10 into the header pipe 30A is set to 15% to 35% of the inner diameter D1 of the header pipe 30A (FIG. 5A). reference).

  Further, the refrigerant inlet side end portion 23 of the low pressure side flat tube 20 is inserted into the header pipe 30C through the slit 31 provided in the header pipe 30C, and the refrigerant outlet side end portion 24 of the low pressure side flat tube 20 is inserted. It inserts in header pipe 30D through the slit 31 provided in header pipe 30D. At this time, the insertion amount S2 into the header pipe 30C of the refrigerant inlet side end 23 of the low pressure side flat tube 20 is set to 15% to 35% of the inner diameter D2 of the header pipe 30C (FIG. 5 ( b)).

  Next, in a state where the header pipes 30A and 30D are connected by the connector 40 and the header pipes 30B and 30C are connected by the connector 40, the header pipes 30B and 30C are carried into a furnace (not shown) and heated at a predetermined temperature. The internal heat exchanger 6 is manufactured by brazing the low-pressure side flat tube 20 and the header pipes 30A, 30B, 30C, and 30D together.

  According to the heat exchanger of the above-described embodiment, the high-pressure side flat tube 10 and the low-pressure side flat tube 20 are bent in a U shape in advance, and distortion is accumulated in the bent portion by bending, but the bent in a U shape in advance. The distortion is removed by the annealing effect by heating when brazing the high-pressure side flat tube 10 and the low-pressure side flat tube 20. Therefore, the pressure loss of the refrigerant flowing through the flat tubes 10 and 20 can be suppressed, and the heat exchange efficiency can be improved with a small size. In addition, since the brazing material is clad in the header pipes 30A, 30B, 30C, and 30D, brazing can be easily and reliably performed.

  The insertion amounts S1 and S2 of the refrigerant inlet side end portions 13 and 23 of at least the high-pressure side flat tube 10 and the low-pressure side flat tube 20 into the header pipes 30A and 30C are the inner diameters D1 and D2 of the header pipes 30A and 30C. Therefore, the brazing material does not flow into the refrigerant flow paths 11 and 21 of the flat tubes 10 and 20 and clogging occurs. Further, the flat tubes 10 are supplied from the header pipes 30A and 30C. , 20 can suppress the turbulent flow of the refrigerant flowing into the part.

  In the above embodiment, the refrigerant inlet side end portions 13 and 23 and the refrigerant outlet side end portions 14 and 24 of the high pressure side flat tube 10 and the low pressure side flat tube 20 are provided in the slits 31 provided in the header pipes 30A to 30D. However, at least the refrigerant inlet side end portions 13 and 23 of the high-pressure side flat tube 10 and the low-pressure side flat tube 20 are connected to the header pipes 30A and 30C. It inserts in header pipe 30A, 30C through the provided slit 31, and insertion amount S1, S2 should just be set to 15%-35% of inner diameter D1, D2 of header pipe 30A, 30C.

  Further, according to the internal heat exchanger 6 of the above embodiment, the header pipe 30A connecting the refrigerant inlet side end 13 of the high pressure side flat tube 10 and the refrigerant outlet side end 24 of the low pressure side flat tube 20 are provided. A header pipe 30D to be connected is connected by a connector 40, and a header pipe 30B that connects the refrigerant outlet side end 14 of the high-pressure side flat tube 10 and a header that connects the refrigerant inlet side end 23 of the low-pressure side flat tube 20 are connected. Since the pipe 30C is connected by the connector 40, the connector 40 can be directly attached to the expansion valve 4 by an attachment screw (not shown) inserted through the attachment hole 41.

  For example, as shown in FIG. The internal heat exchanger 6 is directly attached to the expansion valve 4 arranged at the boundary with R via a connector 40, the evaporator 1 arranged in the cab C, the engine room E.E. The compressor 2 and the condenser 3 arranged in R can be connected via the pipe 5 and can be attached by almost the same work as the conventional attachment process. Moreover, it can respond to a different vehicle model by replacing the piping 5 as shown in FIG.

DESCRIPTION OF SYMBOLS 1 Evaporator 2 Compressor 3 Condenser 4 Expansion valve 5 Piping 6 Internal heat exchanger 10 High pressure side header pipe 11 Refrigerant flow path 13 Refrigerant inlet side end 14 Refrigerant outlet side end 20 Low pressure side header pipe 21 Refrigerant flow Path 23 Refrigerant inlet side end 24 Refrigerant outlet side end 30A to 30D Header pipe 31 Slit 40 Connector

Claims (3)

Used in a refrigeration cycle in which the refrigerant circulates in four strokes of evaporation, compression, condensation, and expansion. An internal heat exchanger comprising a tube,
The high-pressure side flat tube is bent in a U shape, and both the refrigerant inlet side end and the refrigerant outlet side end on both ends are provided to be inclined in a straight line through the arc portion in the same direction,
The low-pressure side flat tube is bent in a U-shape, and the refrigerant inlet side end and the refrigerant outlet side end on both ends are provided to be inclined in a straight line through the arc portion in opposite directions,
The high-pressure side flat tubes are disposed inwardly relative to the low-pressure side flat tubes, each of the refrigerant inlet port side end portion of the high pressure side flat tubes and the low-flat tube and the refrigerant flow outlet end is provided in the header pipe A header pipe inserted into the header pipe through the slit and connected to the refrigerant inlet side end of the high-pressure flat tube, and a header connected to the refrigerant outlet side end of the low-pressure flat tube A header pipe connected to a refrigerant outlet side end of the high-pressure side flat tube, and a refrigerant inlet of the low-pressure side flat tube, the pipe being connected by a connector that is positioned substantially on the same line and attachable to the expansion valve header pipe connected to the side end, is connected to the expansion valve located on substantially the same line by attachable connector, the high-pressure side flat tubes, low-pressure side flat tubes, header pipes and connectors of the brazing material through It is integrally joined,
The amount of insertion into the header pipe of the refrigerant inlet side end of the high-pressure side flat tube and the low-pressure side flat tube is 15% to 35% of the inner diameter of the header pipe,
The thickness of the high-pressure side flat tube and the low-pressure side flat tube is 8 mm or less, and the thickness to width ratio of the flat tube is 1: 4 to 1: 6.
The relationship between the bending radius (R) of the high-pressure side flat tube, the thickness (t1) of the high-pressure side flat tube, and the thickness (t2) of the low-pressure side flat tube is 2.5 ≦ R / (t1 + t2) / 2 ≦ 4.5 and 1 ≦ t2 / t1 ≦ 3/2.
An internal heat exchanger characterized by that. The internal heat exchanger according to claim 1,
The area (A1) of the refrigerant flow path arranged in the high-pressure side flat tube and the area (A2) of the refrigerant flow path provided in the low-pressure side flat pipe satisfy 1 ≦ A2 / A1 ≦ 4. Features an internal heat exchanger. The internal heat exchanger according to claim 1 or 2,
An internal heat exchanger, wherein the header pipe is clad with a brazing material.

Images