Air-conditioner

This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2003-149589 filed on May 27, 2003; the entire contents of which are incorporated herein by reference.

The present invention relates to an air conditioner which adjusts temperature in a vehicle compartment.

A related air conditioner includes a condenser as disclosed in a patent document (Japanese Patent Application Laid-open No. 2003-21432). This condenser includes a core having tubes and fins which are stacked on one another. The condenser includes a tank to which ends of the tubes are connected. The tank includes an inlet and an outlet for refrigerant. The refrigerant flows through tubes and is cooled by heat transferred to the core and is condensed. The tank is in fluid communication with a receiver which separates the refrigerant into a vapor phase and a liquid phase. The core includes a condensing section which condenses the refrigerant. The core also includes a subcooling section which cools the liquid phase refrigerant separated by the receiver. The subcooling section includes a tube or a fin, and a shape thereof is different from that of the tube or the fin of the condensing section. This structure enhances the cooling efficiency of the refrigerant.

The condenser of the related technique has a complicated structure and this increases the productive costs. In the related technique, the refrigerant is separated into the vapor phase and the liquid phase, and the outer size of the receiver is large, which deteriorates the assembling performance of the air conditioner.

The present invention is directed to an air conditioner having a sufficient refrigerant cooling performance and a simplified structure.

The first aspect of the invention provides the following air-conditioner. The air-conditioner includes a compressor configured to compress and discharge a refrigerant. The air-conditioner includes a condenser configured to cool the refrigerant with air outside of a vehicle compartment. The air-conditioner includes a throttle configured to expand the refrigerant. The air-conditioner includes an evaporator configured to cool air inside of the vehicle compartment to eliminate moisture from the air by the expanded refrigerant. The air-conditioner includes a first refrigerant passage having the condensed refrigerant between the condenser and the throttle. The air-conditioner includes a second refrigerant passage having the evaporated refrigerant between the evaporator and the compressor. The air-conditioner includes a refrigerant pipe located between the first and second passages and configured to exchange heat between the condensed and evaporated refrigerants.

The refrigerant pipe may separate the condensed refrigerant into gaseous and liquid refrigerants through the first refrigerant passage.

The refrigerant pipe may include a heat-transfer member longitudinally located thereof and configured to allow refrigerants in the first and second refrigerant passages to exchange heat with each other through the heat-transfer member.

The heat-transfer member integrally interconnects an outer peripheral surface of the second refrigerant passage and an inner peripheral surface of the first refrigerant passage.

The refrigerant pipe may include a double-tube structure. The double-tube structure includes an outer tube in fluid communication with one of the first and second refrigerant passages. The double-tube structure includes an inner tube located inside of the outer tube and is in fluid communication with the other one of the first and second refrigerant passages.

The inner tube may be in fluid communication with the second refrigerant passage. The outer tube is in fluid communication with the first refrigerant passage.

The heat-transfer member may integrally interconnect an outer peripheral surface of the first passage and an outer peripheral surface of the second passage.

The heat-transfer may separate the first and second refrigerant passages from each other.

The heat-transfer member may integrally interconnect the first and second refrigerant passages. The refrigerant pipe is mountable in various directions.

The first refrigerant passage may be located lower than a refrigerant outlet of the condenser.

The second aspect of the invention provides the following air-conditioner. The air-conditioner includes a condenser configured to cool a first refrigerant by air-flow during running of a vehicle to be discharged as a second refrigerant. The air-conditioner includes an expansion valve configured to expand the second refrigerant to be discharged as a third refrigerant. The air-conditioner includes an evaporator configured to evaporate the third refrigerant to be discharged as a fourth refrigerant, cooling air inside of a vehicle compartment. The air-conditioner includes a compressor configured to compress the fourth refrigerant to be discharged as the first refrigerant. The air-conditioner includes a heat exchanger configured to exchange heat between the second and fourth refrigerants.

The heat exchanger may include a first fluid passage having one refrigerant of the second and fourth refrigerants to flow therethrough. The heat exchanger includes a second fluid passage having the other refrigerant of the second and fourth refrigerants to flow therethrough.

The first and second fluid passages may be located concentrically with each other.

The first and second fluid passages may be located eccentrically with each other.

The heat exchanger may include a tube separated into the first and second fluid passages.

The first and second fluid passages may connect longitudinally side-by-side with each other.

The heat exchanger may have an inlet and an outlet for the second refrigerant to flow therethrough. The outlet is positioned lower than the inlet.

FIG. 1A is a schematic diagram of an air-conditioner according to the present invention, where an air-conditioner is adapted to a vehicle;

FIG. 1B is a perspective view of the air-conditioner in FIG. 1A .

FIG. 2A is a schematic diagram of a primary portion of a double-tube structure shown in FIG. 1B ;

FIG. 2B is a schematic diagram of a primary portion of a double-tube structure modified on that in FIG. 2A ;

FIG. 2C is an enlarged sectional view of a coupling in FIG. 2A ;

FIG. 2D is an enlarged sectional view of another coupling in FIG. 2A ;

FIG. 2E is an enlarged sectional view of a coupling modified on that in FIG. 2D ;

FIG. 3A is a perspective view of a double-tube shown in FIG. 1B ;

FIGS. 3B to 3F are perspective views of double-tubes modified on that in FIG. 3A ;

FIG. 4A shows temperature variations of refrigerants along inner and outer tubes of the double-tube structure shown in FIG. 2A ;

FIG. 4B is a T-S (temperature-entropy) diagram of the refrigeration cycle in FIG. 1A , where a dotted line S 1 indicates a vapor-liquid saturation line;

FIG. 5 is schematic view of a double-tube structure modified on that in FIG. 2A , where V 1 indicates a vertical direction and H 1 indicates a horizontal direction;

FIG. 6 is a schematic diagram of a primary portion of a double-tube structure included in an air-conditioner according to a second embodiment, where the inner and outer tubes have a drying agent filled therebetween;

FIG. 7 is a schematic diagram of an air-conditioner according to a third embodiment; and

FIG. 8 is a schematic diagram of a primary portion of a double-tube structure of the air-conditioner shown in FIG. 7 .

The following describes embodiments of the present invention with reference to the accompanying drawings. In the embodiments, like members or parts are designated with like reference characters.

First Embodiment

A vehicle air-conditioner 10 A includes a heat pump type refrigeration cycle 1 A where a refrigerant circulates. The refrigeration cycle 1 A is separated into cycles inside and outside of a vehicle compartment. The refrigeration cycle 1 A includes a compressor 11 which compresses the refrigerant to be discharged. The compressor 11 compresses the refrigerant into a high temperature and high pressure. The refrigeration cycle 1 A includes a condenser 12 which cools the compressed refrigerant with air from the outside of the vehicle compartment. The refrigeration cycle 1 A also includes a throttle 13 A as an expansion valve which expands the refrigerant cooled by the condenser 12 . The refrigeration cycle 1 A includes an evaporator 14 A which cools and dehumidifies the air inside of the compartment by the expanding refrigerant. The evaporator 14 A expands the refrigerant to be reduced in pressure, which is sent into the compressor 11 and is circulated therein.

The condenser 12 and the throttle 13 A include a refrigerant passage 15 therebetween. The evaporator 14 A and the compressor 11 include a refrigerant passage 16 therebetween. The refrigerant passages 15 and 16 include therebetween a refrigerant tube 17 for exchanging heat between refrigerants. The condenser 12 has flexible tubes 18 a and 18 b connected to the inlet and outlet thereof.

In FIG. 2A , the refrigerant tube 17 A includes a metal double-tube structure 20 A with a relatively high thermal conductivity such as aluminum.

The double-tube structure 20 A includes an inner tube 21 A in fluid communication with the refrigerant passage 15 between the condenser 12 and the throttle 13 A. The double-tube structure 20 A includes an outer tube 22 A in fluid communication with the refrigerant passage 16 between the evaporator 14 A and the compressor 11 .

Referring to FIG. 1B , the condenser 12 and the throttle 13 A include the refrigerant passage 15 therebetween which is positioned lower than a refrigerant discharging outlet 12 a of the condenser 12 . The refrigerant passage 15 includes the double-tube structure 20 A with tubes which are disposed in a substantially horizontal position.

Specifically, referring to FIG. 3A , the double-tube structure 20 A includes the outer tube 22 A, and the inner tube 21 A centrally inside of the outer tube 22 A. The outer and inner tube 22 A and 21 A are concentric with each other about the axis. The double-tube structure 20 A includes three heat-transfer members 26 A which integrally interconnect the outer and inner tubes 22 A and 21 A. The heat-transfer members 26 A are arranged at equal angular intervals about the axis. The heat-transfer members 26 A extend radially from the outer peripheral surface 21 A 1 of the inner tube 21 A to the inner peripheral surface 22 A 1 of the outer tube 22 A, and extend longitudinally of the outer and inner tubes 22 A and 21 A. The inner tube 21 A and the outer tube 22 A have refrigerants respectively, which exchange heat with each other through the wall 21 A 2 of the inner tube 21 A and the heat-transfer members 26 A.

In FIGS. 1A and 1B , the double-tube structure 20 A includes a coupling 29 A which interconnects the outer tube 22 A and the refrigerant passage 16 and interconnects the inner tube 21 A and the refrigerant passage 15 .

Referring to FIG. 2A , the coupling 29 A includes a passage 29 A 1 in fluid communication with the inner tube 21 A and the condenser 12 . The coupling 29 A includes a passage 29 A 2 in fluid communication with the outer tube 22 A and the compressor 11 . The coupling 29 A includes a passage 29 A 3 as a recess in fluid communication with the passage 29 A 2 on the side 29 A 4 (refer to FIG. 2C ).

Referring to FIG. 2C , the passage 29 A 1 has a pipe 15 B with the end inserted therein. The pipe 15 B includes a flange 15 B 1 brought in contact with the coupling 29 A. The pipe 15 B has an O-ring 15 B 2 sealing between the passage 29 A 1 and pipe 15 B.

The passage 29 A 2 has a pipe 16 B having the end inserted therein. The pipe 16 B has a flange 16 b 1 brought in contact with the coupling 29 A. The pipe 16 B has an O-ring sealing between the passage 29 A 2 and pipe 16 B.

The passage 29 A 3 has the inner pipe 21 A inserted thereinto. The inner pipe 21 A has an end which is fixed to the entrance periphery of a hole 29 A 6 at the bottom 29 A 5 of the passage 29 A 3 . The inner tube 21 A is in fluid communication with passage 29 A 1 through the hole 29 A 6 . The passage 29 A 3 has an entrance periphery 29 A 7 to which the outer pipe 22 A is fixed.

Referring to FIG. 2D , the double-tube structure 20 A includes a coupling 31 connected therewith at the opposite end. The coupling 31 has a passage 31 a as a recess. The passage 31 a has an entrance periphery 31 a 1 to which the outer pipe 22 A is fixed. The passage 31 a has a side 31 a 2 and a bottom 31 a 3 having holes 31 b and 31 c , respectively. The passage 31 a has the inner pipe 21 A inserted thereinto. The inner pipe 31 b extends longitudinally outward through the hole 31 b at the bottom 31 a 3 . The inner pipe 31 b has another pipe 15 A fitted therewith at the end. The pipe 15 A is in fluid communication with the throttle 13 A through the outlet 24 A.

The coupling 31 is integrated with a pipe 16 A. The pipe 16 A is in fluid communication with the passage 31 a on the side 31 a 2 through the hole 31 c and evaporator 14 A through inlet 25 A. The pipe 16 A extends transversely to the passage 31 a , and curves to extend longitudinally of the passage 31 a.

The pipes 15 A and 16 A have a flange 31 interconnecting them and have O-rings 15 A 1 and 16 A 1 on the outsides, respectively.

The following describes the operations of the refrigeration cycle 1 A and the air-conditioner 10 A.

Referring to FIG. 1A , a refrigerant R 1 flows out of the outlet 12 a of the condenser 12 . The refrigerant R 1 flows into the refrigerant tube 17 A of the double tubes as a refrigerant R 2 . The refrigerant R 2 runs through the double-tube structure 20 A, and flows out as a refrigerant R 3 . The refrigerant R 3 flows into the throttle 13 A where the refrigerant is isenthalpic expanded, and flows out as a refrigerant R 4 . The refrigerant R 4 flows into the evaporator 14 A where the refrigerant is evaporated to absorb heat from the air inside of the vehicle compartment, thereby reducing the temperature inside of the vehicle compartment, and flows out as a refrigerant R 5 . The refrigerant R 5 flows into the refrigerant tube 17 A as a refrigerant R 6 . The refrigerant R 6 flows through the double-tube structure 20 A, and flows out as a refrigerant R 7 . The refrigerant R 7 flows into the compressor 11 where the refrigerant is isentropically compressed, and flows out as refrigerant R 8 . The refrigerant R 8 or R 9 flow into the condenser 12 as a refrigerant R 10 where the refrigerant R 10 is condensed to discharge heat, and flows out as the refrigerant R 1 .

The operation of the double-tube structure 20 A is further described with reference to FIG. 2A . The refrigerant R 1 flows from the condenser 12 into the passage 29 A 1 of the coupling 29 A as the refrigerant R 2 . The refrigerant R 2 runs through the inner pipe 21 A via the passage 29 A 3 , flowing out from the outlet 24 A of pipe 15 A toward the throttle 13 A as the refrigerant R 3 . While, the refrigerant R 5 flows from the evaporator 14 A into the inlet 25 A of the pipe 16 A as the refrigerant R 6 . The refrigerant R 6 runs through the coupling 31 and the outer tube 22 A toward the passage 29 A 3 , and flows out of the passage 29 A 2 toward the compressor 11 as the refrigerant R 7 .

Specifically, the refrigerants R 2 and R 6 flow in the opposite directions from each other, and exchange heat with each other. Heat is conducted from the refrigerant R 2 to the refrigerant R 6 through the wall 21 A 1 of the inner tube 21 A and the heat-transfer members 26 A (refer to FIG. 3A ).

Referring to FIG. 4A , the following describes temperature variations of the refrigerants R 2 and R 6 in the inner and outer tubes 21 A and 22 A. As the refrigerant R 2 runs through the inner tube 21 A toward the outlet 24 A of pipe 15 A, the refrigerant R 2 is cooled at a temperature from T 1 to T 3 . While, as the refrigerant R 6 runs through the outer tube 22 A toward the passage 29 A 2 , the refrigerant R 6 is heated at a temperature from T 5 to T 7 .

Referring to FIG. 4B , the refrigerant R 1 to R 10 has variations in state and heat. The refrigerant R 1 in saturated liquid flows into the double-tube structure 20 A, where the refrigerant R 2 is cooled, turning into the refrigerant R 3 in supercooled liquid. The refrigerant R 3 is isenthalpic expanded by the throttle 13 A, turning into refrigerant R 4 in wet saturated vapor having lower pressure and temperature. The refrigerant R 4 is heated under a constant pressure, turning into the refrigerant R 5 in dry saturated vapor. The refrigerant R 5 flows into the double-tube structure 20 A, where refrigerant R 6 is further heated, turning into the refrigerant R 7 in superheated vapor. The refrigerant R 7 is isentropically compressed by the compressor 11 , turning into the refrigerant R 8 in vapor with a higher temperature and pressure. The refrigerant R 8 flows into the condenser 12 , where the refrigerant RIO in dry saturated vapor is cooled by the condenser 12 under a constant pressure, turning into the refrigerant R 1 .

Specifically, the heat-exchange in the double-tube structure 20 A permits a quantity of heat Q 1 to be discharged during the process from the refrigerant R 1 to the refrigerant R 3 , and a quantity of heat Q 2 to be absorbed during the process from the refrigerant R 5 to the refrigerant R 7 . The quantity of heat Q 1 is equal to the quantity of heat Q 2 .

The refrigerant R 4 to R 5 in the refrigeration cycle 1 A absorbs a quantity of heat from air inside of the compartment, which is defined as Q 3 . The quantity of heat Q 3 is equal to integration of temperature at T 5 relative to entropy from refrigerant R 4 to refrigerant R 5 . While, a refrigeration cycle L 1 , R 1 , L 2 , and R 5 represents a cycle without the heat exchange, and a refrigerant absorbs a quantity of heat from air inside of the vehicle compartment, which is defined as Q 4 . The quantity of heat Q 4 is equal to the integration of temperature at T 5 relative to entropy from the refrigerant L 2 to the refrigerant R 5 . As is apparent from FIG. 4B , the quantity of heat Q 3 is greater than the quantity of heat Q 4 . Thus, heat exchange of the double-tube structure 20 A improves the refrigeration cycle 1 A in cooling performance and coefficient of performance (absorption heat of refrigerant/work of compressor).

According to this embodiment, the double-tube structure 20 A includes a heat exchanging function capable of exchanging heat between the refrigerant R 2 in the refrigerant passage 15 between the condenser 12 and the throttle 13 A, and the refrigerant R 6 in the refrigerant passage 16 between the evaporator 14 A and the compressor 11 . The double-tube structure 20 A further includes a gas/liquid separating function of refrigerant in the refrigerant passage 15 between the condenser 12 and the throttle 13 A. This structure eliminates the necessity of a heat exchanging unit and a gas/liquid separating unit, and realizes the air conditioner 10 A having a sufficient refrigerant-cooling performance and a simplified entire structure.

The refrigerant pipe 17 eliminates the necessity of a refrigerant reserving unit such as a liquid tank and a modulator. This reduces the amount of refrigerant to be charged in the pipe.

The double-tube structure 20 A having the relatively simple structure has the heat exchanging function, and the cooling performance of a refrigerant enhances without increasing the productive costs and increasing the entire apparatus in size. The double-tube structure 20 A is made of metal having relatively high thermal conductivity such as aluminum. This structure efficiently transfers the heat between the inner tube 21 A and the outer tube 22 A, endures the refrigerant with a pressure, and forms a tube having high hermeticity. In addition, aluminum having relatively small specific gravity reduces the entire apparatus in weight.

The double-tube structure section is not limited in the mounting direction. This allows the double-tube structure 20 A to be disposed in the tube, without ensuring another place where the double-tube structure 20 A is to be assembled. This structure ensures a sufficient refrigerant cooling function, and facilitates the assembling operation of the air conditioner 10 A.

The refrigerant passage 15 is provided between the condenser 12 and the throttle 13 A and is positioned lower than the refrigerant discharging outlet 12 a . This passage 15 improves the heat exchange efficiency of the condenser 12 without reserving the liquid phase refrigerant in the condenser 12 . The passage 15 further improves the gas/liquid separating function of the refrigerant, and the passage 15 leads the liquid phase refrigerant into the throttle 13 .

A higher pressure liquid phase refrigerant flows through the inner tube 21 A of the double-tube structure 20 A, while a lower pressure gas phase refrigerant flows through the outer tube 22 A. This manner reduces the volume of the entire pipe, and reduces the amount of refrigerant to be charged into the pipe.

As another embodiment, the refrigerant R 2 may pass through the outer tube 22 A and the refrigerant R 6 may pass through the inner tube 21 A.

Referring to FIG. 2B , the refrigerants R 2 and R 6 flow in identical directions in the inner tube 21 A and the outer tube 22 A to exchange heat with each other.

Referring to FIG. 3B , a double-tube structure 20 B includes an outer tube 22 B, and an inner tube 21 B which are eccentric with each other. The inner tube 21 B has an outer surface 21 B 1 joined to the inner surface of the outer tube 22 B. This structure allows refrigerants R 2 and R 6 to exchange heat with each other through the wall 21 B 2 of inner tube 21 B.

Referring to FIG. 3C , a double-tube structure 20 C 1 includes an outer tube 22 C and an inner tube 21 C which are arranged longitudinally side-by-side with each other. The double-tube structure 20 C 1 includes a heat-transfer member 26 B which integrally interconnects the outer and inner tubes 22 C and 21 C. The heat-transfer member 26 B extends longitudinally between the outer and inner tubes 22 C and 21 C. This structure allows refrigerants R 2 and R 6 to exchange heat with each other through the heat-transfer member 26 B.

Referring to FIG. 3D , a double-tube structure 20 C 2 differs from the double-tube structure 20 C 1 in that the outer and inner tubes 22 C and 21 C connect with each other, with the outer surfaces 21 C 1 and 22 C 1 being in contact with each other. This structure 20 C 2 achieves lower productive costs and a smaller size in comparison with the double-tube structure 20 C 1 .

Referring to FIG. 3E , a double-tube structure 20 D 1 includes a tube 22 D having two fluid passages 22 D 1 and 22 D 2 , which are separated from each other by a straight heat-transfer member 26 D 1 . The fluid passage 22 D 1 is in communication with the refrigerant passage 16 , and the fluid passage 22 D 2 is in communication with the refrigerant passage 15 . This structure allows refrigerants R 2 and R 6 in fluid passages 22 D 1 and 22 D 2 to exchange heat with each other through the heat-transfer member 26 D 1 . This structure achieves lower productive costs and a smaller size.

Referring to FIG. 3F , a double-tube structure 20 D 2 differs from the double-tube structure 20 D 1 in that a curved heat-transfer member 26 D 2 separates the interior of the tube 22 D into two fluid passage 22 D 3 and 22 D 4 .

Referring to FIG. 2E , the double-tube structure 20 A includes another coupling 33 in place of coupling 31 . The coupling 33 has a passage 33 a as a recess in fluid communication with the outer pipe 22 A. The coupling 33 has passage 33 b as a hole in fluid communication with the inner tube 21 A and the throttle 13 A. The coupling 33 has passages 33 c and 33 d as a hole in fluid communication with the passage 33 a and the evaporator 14 A.

The passage 33 a has the outer pipe 22 A fixed to the entrance periphery 33 a 1 . The passage 33 a has the inner pipe 21 A inserted thereinto. The inner pipe 21 A is fixed to the entrance periphery of the passage 33 b on the bottom 33 a 2 of passage 33 a.

The passage 33 b is aligned with the passage 33 a . The passage 33 b has a smaller size in cross section than the passage 33 a . The passage 33 c extends transversely from the side 33 a 3 of the passage 33 a . The passage 33 c has an opening at the end, which is closed by a lid 33 e . The passage 33 c communicates with a passage 33 d which extends transversely to the passage 33 c and extends side-by-side with the passage 33 a . The passages 33 b and 33 d have O-rings 33 g and 33 f on the outsides, respectively.

Referring to FIG. 5 , the double-tube structure 20 A inclines downwardly toward the throttle 13 A from the condenser 12 or upwardly toward the compressor 11 from the evaporator 14 A. Specifically, the double-tube structure 20 A is longitudinally inclined relative to a horizontal line H 1 to descend toward the throttle 13 A or evaporator 14 A. The double-tube structure 20 A has longitudinally opposed ends 20 a and 20 b as an outlet and an inlet proximate to throttle 13 A and condenser 12 , respectively. The end 20 a is positioned lower than the end 20 b at a vertical interval h 2 therebetween. This structure further enhances the gas/liquid separating function of a refrigerant, thus allowing the refrigerant to be efficiently separated into gaseous and liquid refrigerants.

Second Embodiment

Referring to FIG. 6 , a double tube structure 20 E includes an outer pipe 22 E, through which a refrigerant flows from the condenser 12 to the throttle 13 A. The double tube structure 20 E includes an inner pipe 21 E, through which a refrigerant flows from the evaporator 14 A to the compressor 11 .

The outer tube 22 E includes a drying agent 23 charged therein such that a refrigerant can flow through the outer tube 22 E. While the refrigerant flows through the outer tube 22 A, the drying agent 23 adsorbs moisture absorbed by the refrigerant during circulating in the refrigeration cycle.

The following describes the operation of air-conditioner 10 E. A refrigerant R 1 flows from the condenser 12 into the outer pipe 22 E as a refrigerant R 2 . While the refrigerant R 2 runs through the drying agent 23 , the agent 23 absorbs moisture from the refrigerant R 2 . The refrigerant R 2 flows out of the outlet 24 E of pipe 15 E toward throttle 13 A as a refrigerant R 3 . While, a refrigerant R 5 flows from the evaporator 14 A into the inlet 25 E of the pipe 16 E as a refrigerant R 6 . The refrigerant R 6 runs through an inner pipe 21 E, where the refrigerant R 6 exchanges heat with refrigerant R 2 through the inner pipe 21 E. The refrigerant R 2 flows out of the pipe or refrigerant passage 16 toward the compressor 11 as a refrigerant R 7 .

According to the embodiment, the inner tube 21 E of the double-tube structure 20 E is in fluid communication with the refrigerant passage 16 between the evaporator 14 A and the compressor 11 . The outer tube 22 E of the double-tube structure 20 E is in fluid communication with the refrigerant passage 15 between the condenser 12 and the throttle 13 A. This structure has sufficient refrigerant cooling performance, and ensures a volume of the passage between the condenser 12 and the throttle relatively easily. This structure further enhances the gas/liquid separating performance of the refrigerant.

The outer tube 22 E includes the charged drying agent 23 through which a refrigerant can flow. While the refrigerant R 2 flows through the outer tube 22 A, the drying agent 23 adsorbs moisture which the refrigerant absorbs during circulating in the refrigeration cycle. This adsorption prevents a refrigerant from becoming deteriorated, and stably maintains the vehicle air conditioner 10 E in cooling performance.

Third Embodiment

Referring to FIG. 7 , a vehicle air conditioner 10 F is different from the vehicle air conditioner 10 A of the first embodiment in that the air conditioner 10 F includes two sets of throttles 13 F ( 13 F 1 and 13 F 2 ) and evaporators 14 F ( 14 F 1 , 14 F 2 ). One set 13 F 1 and 14 F 1 is disposed for a front seat. The other set 13 F 2 and 14 F 2 is disposed for a rear seat. The throttles 13 F 1 and 13 F 2 expand refrigerants cooled by the condenser 12 . The evaporators 14 F 1 and 14 F 2 cool and dehumidify air inside of the vehicle compartment by expanding refrigerants.

The refrigerant passage 15 is branched into two passages at the inlet of the double-tube structure 20 F from the condenser 12 . One of the passages is in fluid communication with the front-seat evaporator 14 F 1 via the front-seat throttle 13 F 1 . The other of the passages is in fluid communication with the rear-seat evaporator 14 F 2 via the rear-seat throttle 13 F 2 . The refrigerant through the front-seat evaporator 14 F 1 and the refrigerant through the rear-seat evaporator 14 F 2 join with each other at the outlet of the double-tube structure 20 F toward compressor 11 .

Specifically, referring to FIG. 8 , the double-tube structure 20 F includes an inner tube 21 F in fluid communication with the front seat evaporator 14 F 1 through a pipe 16 F. The double-tube structure 20 F includes an outer tube 22 F enclosing the inner tube 21 F from the outside. The outer tube 22 F is in fluid communication with the front-seat throttle 13 F 1 through a pipe 15 F. The double-tube structure 20 F includes a coupling 20 F at the end. The coupling 20 F includes a passage 29 F 1 in fluid communication with the refrigerant passage 15 or condenser 12 . The coupling 20 F includes passages 29 F 2 and 29 F 3 separated from the passage 29 F 1 . The passage 29 F 2 is in fluid communication with the outer tube 22 F. The passage 29 F 3 is in fluid communication with the rear-seat throttle 13 F 2 . The coupling 20 F includes a passage 29 F 4 in fluid communication with the rear-seat evaporator 14 F 2 and the inner tube 21 F. The coupling 20 F includes a passage 20 F 5 in fluid communication with the inner tube 21 F and the refrigerant passage 16 or compressor 11 .

The following describes the operations of the refrigeration cycle 1 F and the air conditioner 10 F.

Referring to FIG. 7 , the refrigerant R 1 flows from the condenser 12 into the coupling 29 F. The refrigerant R 1 is separated into refrigerants R 2 and R 7 in the coupling 29 F. The refrigerant R 2 runs through the refrigerant pipe 17 F and flows out toward the front seat throttle 13 F 1 as a refrigerant R 3 . While, the refrigerant R 7 flows out toward the rear seat throttle 13 F 2 . The refrigerants R 3 and R 7 flow into the throttles 13 F 1 and 13 F 2 , respectively, where the refrigerants are isenthalpic expanded therein, and flow out as refrigerants R 4 and R 8 . The refrigerants R 4 and R 8 flow into evaporators 14 F 1 and 14 F 2 , where the refrigerants are evaporated therein to absorb heat from air around the front and the rear seats inside of the vehicle compartment, thus reducing temperatures around the front and rear seats. The refrigerant R 5 flows out of the evaporator 14 F 1 into the refrigerant pipe 17 F, and the refrigerant R 6 runs through the refrigerant pipe 17 F. While, the refrigerant R 9 flows from the evaporator 14 F 2 into the coupling 29 F. The refrigerants R 9 and R 6 join together with each other in the coupling 29 F, flowing out toward the compressor 11 as a refrigerant R 10 . The refrigerant R 10 flows into the compressor 11 , where the refrigerant is isentropically compressed, flowing out as a refrigerant R 11 or R 12 . The refrigerant R 12 flows into the condenser 12 , where the refrigerant R 13 is condensed to discharge heat.

Referring to FIG. 8 , the operation is specifically described in the double-tube structure 20 F. The refrigerant R 1 flows through the passage 29 F 1 of the coupling 29 F. The refrigerant R 1 is separated into the refrigerants R 2 and R 7 at the junction of the coupling 29 F, which run through the passages 29 F 2 and 29 F 3 , respectively.

The refrigerant R 2 runs through the outer tube 22 F, and flows out of the outlet 24 F of the pipe 15 F toward the front-seat throttle 13 F 1 as the refrigerant R 3 . While, the refrigerant R 5 returns into the inlet 25 F of the pipe 16 F as the refrigerant R 6 from the evaporator 14 F 1 . The refrigerant R 6 runs through the outer tube 22 F toward the passage 29 F 5 .

While, the refrigerant R 7 flows out toward the rear-seat throttle 13 F 2 . The refrigerant R 9 returns to the passage 29 F 4 from the evaporator 14 F 2 .

Specifically, the refrigerants R 6 and R 2 flow in the opposite directions from each other, and exchange heat with each other though the inner tube 21 F.

The refrigerants R 6 and R 9 join together with each other at the passage 29 F 5 , and flow out toward the compressor 11 as the refrigerant RIO.

Although the invention has been described above by reference to certain embodiments of the invention, the invention is not limited to the embodiments described above. Modifications and variations of the embodiments described above will occur to those skilled in the art, in light of the above teachings. The scope of the invention is defined with reference to the following claims.