Condenser assembly structure

Abstract: The condenser assembly structure is disclosed. The opening of the outgoing pipe is positioned below the upper openings of the heat transfer tubes in the inner space of the upper header pipe. Cutouts are formed in the upper ends of heat transfer tubes, which are located within an upper header pipe. A lubricant mixed in a refrigerant is introduced from the inside of the upper header pipe into the heat transfer tubes by way of the cutouts. Alternatively, the outgoing pipe defining is attached to the lower header pipe at a position close to its end. A total passage area of first heat transfer tubes through which the refrigerant flows downward is larger than that of second heat transfer tubes through which the refrigerant flows upward. The total passage area of the second heat transfer tubes is smaller than that of third heat transfer tubes through which the refrigerant flows downward.

Description: The present invention relates to a condenser inserted between a compressor and an evaporator in a vapor compression type refrigerator, which is used for an automobile air conditioner. The condenser receives the refrigerant from the compressor, condenses and liquefies the refrigerant by causing it to radiate heat, and sends the liquefied refrigerant to an evaporator by way of a liquid tank. A vapor compression type refrigerator is incorporated into an automobile air conditioner for cooling and dehumidifying the inside of an automobile. A circuit diagram showing the concept of the vapor compression type refrigerator, disclosed in Japanese Patent Publication No. Hei. 4-95522, is shown in Fig. 14. A compressor 1 discharges a gaseous refrigerant that is high in temperature and pressure to a condenser 2. When passing through the condenser 2, a heat exchanging is performed between the refrigerant and air. The gaseous refrigerant drops in temperature and is condensed into a liquid refrigerant. The liquid refrigerant is temporarily impounded in a liquid tank 3. Then, it is sent through an expansion valve 4 to an evaporator 5 where it is evaporated. Temperature of the evaporator 5 drops because the evaporator loses the latent heat of vaporization. Therefore, when air for air ccnditioning is circulated through the evaporator 5, the air is cooled and dehumidified. The refrigerant is evaporated into a gaseous refrigerant in the evaporator 5, and sucked by and into the compressor 1, and compressed again therein. In this way, the refrigerating cycle is repeated. Fig. 15 shows a condenser 2 to which the present invention is applied. As shown, the condenser 2 includes a couple of upper and lower header pipes 6a and 6b arranged horizontally and in parallel. Refrigerant vertically flows between the upper and lower header pipes 6a and 6b. The condenser 2 is of the so-called vertical flow type. Attempt is made to use fins for the cores of both the condenser 2 and a radiator 26 located adjacent to the condenser, and to realize a compact assembly of the condenser 2 and the radiator 26. One to a plural number of partitioning walls are provided within the header pipes 6a and 6b of the condenser 2, whereby the inner parts of the header pipes 6a and 6b are air- and liquid-tightly partitioned into a plural number of chambers. The inner part of the upper header pipe 6a is partitioned, by an upper partitioning wall 13, into a first upper chamber 15 and a second upper chamber 16. The inner part of the lower header pipe 6b is partitioned, by a lower partitioning wall 14, into a first lower chamber 17 and a second lower chamber 18. In the core 9 of the condenser 2, a plural number of heat transfer tubes 7 are vertically arranged between the upper and lower header pipes 6a and 6b. Fins 8 are located between and supported by the heat transfer tubes 7 located adjacent to each other. Those heat transfer tubes 7 are classified into three types of heat transfer tubes, first heat transfer tubes 19, second heat transfer tubes 20, and third heat transfer tubes 21. The first heat transfer tubes 19 are opened at the upper ends into the first upper chamber 15, and at the lower ends into the first lower chamber 17. The second heat transfer tubes 20 are opened at the upper ends into the second upper chamber 16, and at the lower ends into the first lower chamber 17. The third heat transfer tubes 21 are opened at the upper ends into the second upper chamber 16, and at the lower ends into the seccnd lower chamber 18. The heat transfer tubes 7 are grouped into the first to third hoat transfer tubes 19, 20 and 21 with respect to the upper and lower partitioning walls 13 and 14. The first heat transfer tubes 19 are located moat upstream in the core, and feeds the refrigerant downward. The second heat transfer tubes 20 are located at the central portion of the core, and feeds the refrigerant upward. The third heat transfer tubes 21 are located most downstream in the core, and feeds the refrigerant downward. Side plates 10a and 10b are located on both sides of the core 9 including the heat transfer tubes 7 and the fins 8. The first, second and third heat transfer tubes 19, 20 and 21 are different in number. A total passage area S19 of the first heat transfer tubes L9 is larger than a total passage area S20 of the second heat transfer tubes 20, and the total passage area S20 is larger than a total passage area S21 of the third heat transfer tubes 21. That is, S19 > S20 > S21. In the case of a condenser 2 shown in Fig. 16, S19 = S20 = S21, and the first, second and third heat transfer tubes 19, 20 and 21 are equal in number. That is, the total passage area of one group (upward group or downward group) of the heat transfer tubes is generally decreased as the refrigerant flows downward because the refrigerant is more condensed as flowing downward so that the volume of the refrigerant is more decreased. An incoming block 11 is brazed to the upper side of right end (in Fig. 15) of the upper header pipe 6a. The incoming block 11 includes incoming ports 12 continuous to the inside of the first upper chamber 15. Refrigerant that comes in through the incoming ports 12 flows vertically between the upper and lower header pipes 6a and 6b in the direction of arrows in Fig. 15. An outgoing pipe 22 through which the refrigerant goes out is firmly attached to the lower side of the left end (in Fig. 15) of the lower header pipe 6b, viz., the lower surface of the leftmost chamber (second lower chamber 18) located most downstream in the condenser. The upper end of the outgoing pipe 22 is opened into the second lower chamber 18 at a position close to the lower partitioning wall 14. The refrigerant flows into the condenser 2, flows through the condenser 2 in the direction of the arrows (Fig. 15), and reaches the second lower chamber 18 of the lower header pipe 6b. Then, the refrigerant goes out of the outgoing pipe 22, flows through the liquid tank 3 and the expansion valve 4, and goes to the evaporator 5 (Fig. 14). In Fig. 16, the outgoing pipe 22 is omitted. In the inner part of the thus constructed condenser 2, the refrigerant that comes in from the compressor 1 (Fig. 14) flows while being condensed into a liquid refrigerant. Specifically, the refrigerant comes in the condenser 2 through the incoming ports 12, and during the passing of it through the condenser 2, a heat exchange is carried out between the refrigerant and air that flows through the core 9 in the direction from one side to the other side of the core 9, and temperature of the refrigerant drops. Thus, the gaseous refrigerant comes in the condenser 2 is separated into a liquid refrigerant and a gaseous refrigerant. Therefore, the liquid refrigerant and the gaseous refrigerant coexist in the third heat transfer tubes 21. Fig. 17 shows another example of the conventional condenser 2. In this condenser, the outgoing pipe 22 is attached to the upper side of the left end of the upper header pipe 6a, viz., the upper surface of the leftmost chamber located most downstream in the condenser. That is, two upper partitioning walls 13 are provided in the upper header pipe 6a. In the condenser 2 shown in Fig. 17, the outgoing pipe 22 is inserted into the upper header pipe 6a through an connection hole 30, which is formed in the upper side of the upper header pipe 6a, and is opened into the upper header pipe 6a. The outer circumferential surface of the outgoing pipe 22 is air- and liquid-tightly coupled with the inner circumferential edge of the connection hole 30 by brazing as shown in Fig. 18. The upper ends of the heat transfer tubes 7 are inserted into the upper header pipe 6a through the connection hole 31 formed in the lower side of the upper header pipe 6a. The upper opening 33 of each heat transfer tube 7 is positioned at the middle of the upper header pipe 6b when viewed in cross section. When an amount of the liquid refrigerant staying in the upper header pipe 6a is small (at high load), a liquid level L1 of the liquid refrigerant is below the opening 32 of the outgoing pipe 22 (Fig. 18). When the liquid refrigerant is large (at low load), a liquid level L2 of the refrigerant reaches the opening 32 of the outgoing pipe 22. A similar construction is shown in US-A-5178211. Here, the term "high load" means a state that a difference between a set temperature in the air conditioner and an actual temperature in the car is large, and the refrigerant frequently circulates in the air conditioner. The term "low load" means a state that a difference between the set temperature and the actual temperature is small, and the refrigerant infrequently circulates in the air conditioner. When the liquid refrigerant staying in the upper header pipe 6a is small in amount, the liquid level L1 of the refrigerant is below the opening 32 of the outgoing pipe 22. Therefore, no refrigerant flows into the outgoing pipe 22. The result is that the amount of the liquid refrigerant fed from the condenser 2 to the expansion valve 4 is reduced, temperature drop of the evaporator 5 (Fig. 14) is small, and hence the air conditioner exhibits insufficiently its cooling capability. When the liquid refrigerant staying in the upper header pipe 6a is large in amount, the liquid level L2 of the refrigerant is above the opening 32 of the outgoing pipe 22. The air conditioner does not suffer from the above problem, but suffers from the following problem. Since the liquid level L2 of the refrigerant increases above the upper openings 33 of each heat transfer tube 7, the gaseous refrigerant that has ascended through the heat transfer tubes 7 flows into the upper header pipe 6a while pushing aside the liquid refrigerant that stays in the upper header pipe 6a. Since a viscosity of the liquid refrigerant is larger than that of the gaseous refrigerant, the liquid refrigerant exhibits a large resistance to the thrust by the gaseous refrigerant. Therefore, when the refrigerant ascends through the heat transfer tubes 7 and flows into the upper header pipe 6a, it undergoes an increased impedance. In other words, a resistance of the condenser 2 is increased. The increase of the resistance of the condenser 2 leads to degradation of the performances of the vapor compression type refrigerator having the condenser 2 incorporated thereinto. EP-A-0622599 discloses a heat exchanger assembly in which the upper ends of the heat transfer tubes are attached to the inner upper surface of the upper header pipe in order to improve its strength. The outlet pipe extends horizontally from the header pipe and a communication path is provided in the side surface at the upper end of each heat transfer tube to allow refrigerant to pass between the header pipe and the tubes. Further, a lubricant is mixed into the refrigerant to lubricate the compressor. In the conventional condensers constructed as aforementioned, the lubricant tends to be gathered in the condenser 2, to possibly lessen the amount of the lubricant that circulates through the refrigerating cycle in the vapor compression type refrigerator. The lubricant mixed into the refrigerant circulates, together with the refrigerant, through the refrigerating cycle in the refrigerator while lubricating the compressor. The opened, upper ends of the heat transfer tubes 7 of the core 9 of the condenser 2 are protruded into the inside of the upper header pipe 6a and their tips are positioned at the mid position therein when viewed in cross-section (Figs. 19 and 20). The lubricant 34 that is mixed into the refrigerant flows into the upper header pipe 6a and tends to be gathered on the bottom of the upper header pipe 6a. The lubricant mixed into the refrigerant will gradually be separated from the refrigerant with time. After separating from the refrigerant in the upper header pipe 6a, the lubricant 34 (in Figs. 19 and 20) is gathered in the space between the bottom surface of the upper header pipe 6a and the upper end openings of the heat transfer tubes 7, viz., on the bottom of the upper header pipe 6a. The lubricant 34 that is gathered on the bottom of the upper header pipe 6a a little flows in the direction of refrigerant flow. Therefore, the amount of lubricant 34 that circulates through the refrigerating cycle in the vapor compression type refrigerator is reduced by the amount of the lubricant gathered on the bottom of the upper header pipe 6a. In an extreme case, the amount of the lubricant 34 that circulates through the refrigerating cycle in the vapor compression type refrigerator is reduced below a necessary amount of the lubricant. And a durability of the compressor will be impaired. The durability impairing problem may be solved by increasing an amount of lubricant to be put into the refrigerating cycle by a lubricant amount equal to the amount of the lubricant that will be gathered on the bottom of the upper header pipe 6a. However, the increase of the lubricant amount creates another problem; films of the lubricant tend to be formed on the inner surfaces of the heat transfer tubes which form a heat exchanger (including the evaporator and the condenser). Presence of the lubricant films on the heat transfer tubes hinder the heat exchanging of the refrigerant flowing through the heat transfer tubes with the heat transfer tubes. The result is that the performance of the heat exchanger is degraded. The increase of the lubricant amount further increases the cost to manufacture the vapor compression type refrigerator having the condenser 2 incorporated thereinto. To reduce the amount of the lubricant 34 gathered on the bottom of the upper header pipe 6a, a structure as shown in Figs. 21 and 22 is known. In the structure, the bottom of the upper header pipe 6a is flat. A protrusion of the upper ends of the heat transfer tubes 7 from the flat bottom 35 is reduced. However, the structure suffers from the following problems. In the structure, the bottom 35 is large in area and a depth of the gathered lubricant 34 is not large, but the amount of the lubricant 34 gathered on the bottom of the upper header pipe 6a is increased. When the flat bottom 35 receives a high pressure refrigerant that is fed to the upper header pipe 6a, it is easily deformed. Therefore, where the structure is used, it is difficult to make a compromise between the high durability and the reduction of the condenser weight by thinning the upper header pipe 6a. There is another problem in the condenser in Fig. 15. The lower end openings of the third heat transfer tubes 21, which are located closer to the center (closer to the right-hand side in Fig. 15) of the core 9, are confronted with the upper end opening of the outgoing pipe 22. Therefore, more of the liquid refrigerant tends to flow through those third heat transfer tubes 21 closer to the core center. The reason for this follows. The liquid refrigerant that flows toward the left end (in Fig. 15) of the upper header pipe 6a in the second upper chamber 16 will flow downward by its weight. As a result, a more amount of the liquid refrigerant flows into the third heat transfer tubes 21 that are located closer to the center of the core 9 and in the higher part of the refrigerant flow in the second upper chamber 16. The liquid refrigerant that flows into the third heat transfer tubes 21 straightforwardly reaches the upper end opening of the outgoing pipe 22, and discharged out of the condenser 2. Meanwhile, the gaseous refrigerant is high in a high velocity of flow, and less affected by its weight. Therefore, the gaseous refrigerant flows to reach the end of the second upper chamber 16 that is located downstream in the core, and flows downward through the third heat transfer tubes 21 (laid out in the cross-hatched portion in Fig. 15) located close to the left end of the core 9, and reaches the left end portion (in Fig. 15) of the second lower chamber 18. The gaseous refrigerant then flows to the center in the second lower chamber 18, and goes out of the condenser 2, through the outgoing pipe 22. If the liquid refrigerant and the gaseous refrigerant that pass through the third heat transfer tubes 21 and reach the second lower chamber 18 are mixed in the chamber and go out of the outgoing pipe 22, no problem arises in particular. The gaseous refrigerant that reaches the left end of the second lower chamber 18 and its near portion, swiftly moves to a portion near to the upper end of the outgoing pipe 22. Sometimes, the gaseous refrigerant is obstructed by the liquid refrigerant temporarily staying at a portion close to the right end of the second lower chamber 18, and fails to reach the upper end opening of the outgoing pipe 22. The gaseous refrigerant that fails to reach the upper end opening of the outgoing pipe 22 and stays in the second lower chamber 18, increases to be in excess of a given amount of gaseous refrigerant. At this time, the gaseous refrigerant rushes into the outgoing pipe 22 by its increased pressure. Where this phenomenon is repeated, only the liquid refrigerant and the mixture of the liquid refrigerant and the gaseous refrigerant are alternatively discharged through the outgoing pipe 22. The refrigerant discharging operation from the outgoing pipe 22 is unstable. The result is the impairing of the temperature control function of the automobile air conditioner. Further, there is still another problem in the condenser in Figs. 15 and 16. The lubricant tends to gather at a portion B (shaded in Figs. 15 and 16) within the lower header pipe 6b which is close to the lower partitioning wall 14 which partitions the inner space of the lower header pipe 6b into the first lower chamber 17 and the second lower chamber 18. The reason for this is that after flowing through the first heat transfer tubes 19 into the first lower chamber 17, the refrigerant flows to the second heat transfer tubes 20 while pushing the lubricant against the lower partitioning wall 14, and flows upward through the second heat transfer tubes 20. If the flow velocity of the refrigerant flowing through the first lower chamber 17 to the lower partitioning wall 14 is large, it pushes the lubricant into the second heat transfer tubes 20. In the structure of either condenser of Figs. 15 and 16, the flow velocity is not sufficiently large. Therefore, when the refrigerant flows upward through the second heat transfer tubes 20, the lubricant mixed into the refrigerant remains in the vicinity of the lower partitioning wall 14. The lubricant fed to the compressor is reduced by an amount of the lubricant staying in the condenser 2, and deficient in amount. This problem frequently arises particularly when the amount of the refrigerant discharged out of the compressor is small and a reduced amount of the refrigerant flows through the condenser 2, for example, when the engine is idling, and when the compressor of the variable capacity type is reduced in its capacity. Accordingly, the invention consists in a condenser assembly structure comprising: an upper header pipe arranged horizontally; a lower header pipe arranged parallel to said upper header pipe; a plural number of heat transfer tubes arranged vertically between said upper and lower header pipes, upper and lower ends of said heat transfer tubes opening into inner parts of said upper and lower header pipes; and an outgoing pipe coupled to said upper header pipe, wherein a refrigerant flows through said upper and lower header pipes and said heat transfer tubes and flows out through an opening in said outgoing pipe, characterised in that the opening of said outgoing pipe is positioned below the upper openings of said heat transfer tubes in the inner space of said upper header pipe. The opening of the outgoing pipe, which is coupled with the upper header pipe, is positioned below the upper openings of the heat transfer tubes horizontally adjacent to each other. The opening of the outgoing pipe is lower than the liquid level of the liquid refrigerant in the upper header pipe even when the liquid refrigerant accumulating in the upper header pipe is relatively small, whereby the liquid refrigerant can be fed into the outgoing pipe. Further, the upper openings of the heat transfer tubes are always higher than the liquid level of the liquid refrigerant staying on the upper header pipe. Therefore, the liquid refrigerant staying in the upper header pipe does not resist a flow of the refrigerant that is discharged from the heat transfer tubes into the upper header pipe. Thus, the fluid resistance of the condenser is set at a low value of resistance. Where the tip of the outgoing pipe is abutted against the bottom of the upper header pipe, the support of the outgoing pipe by the upper header pipe is more reliable. According to a preferred aspect of the invention, a fluid passage is formed at an upper end of at least one of the heat transfer tubes, the fluid passage is located below the upper end of the heat transfer tube and just above an inner bottom portion of the upper header pipe so as to guide a fluid accumulated at the inner bottom portion of the upper header pipe into the heat transfer tube. In the thus constructed condenser, a fluid passage is formed in the upper part of at least one heat transfer tube. Therefore, the lubricant staying on the bottom of the upper header pipe is introduced into the heat transfer tube having the passage, through the passage. The fluid flows downward through the heat transfer tube to the lower header pipe. It never happens that much lubricant stays on the bottom of the upper header pipe. Therefore, the amount of the lubricant circulating in the vapor compression type refrigerator with the condenser incorporated thereinto is increased correspondingly. The shape of the cross section of the upper header pipe remains circular. Therefore, an enough pressure resistance of the upper header pipe can be secured even if the upper header pipe is thinned. According to a further preferred aspect of the invention, said plural number of heat transfer tubes are classified into upward-flow heat transfer tubes or downward-flow heat transfer tubes, through which a refrigerant including a lubricant flows upward or downward respectively, and groups of said upward-flow heat transfer tubes and groups of said downward-flow heat transfer tubes are distributed alternatively in a horizontal direction, and wherein the total passage area of a group of said upward-flow heat transfer tubes is equal to or smaller than the total passage area of a group of said downward-flow heat transfer tubes which is located downstream of said group of upward-flow heat transfer tubes. In the condenser, the structure thereof forcibly flows the refrigerant from the lower header pipe to the upper header pipe. Therefore, the lubricant as well as the refrigerant is efficiently fed into the heat transfer tubes. BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings: Fig. 1 is a cross-sectional view taken along line V-V in Fig. 17, the view showing a jointing structure including an outgoing pipe, upper header pipe, and heat transfer tube according to the present invention; Fig. 2 is a cross-sectional view taken along line I-I in Fig. 1; Fig. 3 is a perspective view showing the end of an outgoing pipe used in a first possible modification to the present invention; Fig. 4 is a cross-sectional view taken along line IV-IV in Fig. 15, the view showing a jointing structure including an upper header pipe and a heat transfer tube, which constitutes a second possible modification to the present invention; Fig. 5 is a cross-sectional view taken along line II-II in Fig. 4; Fig. 6 is a cross-sectional view of another jointing structure including an upper header pipe and a heat transfer tube, which constitutes a third possible modification to the present invention; Fig. 7 is a perspective view showing a condenser which is a fourth possible modification to the present invention; Fig. 8 is a perspective view showing a condenser which is a fifth possible modification to the present invention; Fig. 9 is a perspective view showing a condenser which is a first comparative example to the present invention; Fig. 10 is a perspective view showing a condenser which is a second comparative example to the present invention; Fig. 11 is a perspective view showing a condenser which is a third comparative example to the present invention; Fig. 12 is an enlarged view showing a portion A in Fig. 11; Fig. 13 is a perspective view showing a condenser which is a fourth comparative example to the present invention; Fig. 14 is a circuit diagram showing a vapor compression type refrigerator having a compressor incorporated thereinto; Fig. 15 is a perspective view showing an example of the conventional condenser; Fig. 16 is a perspective view showing another conventional condenser; Fig. 17 is a perspective view showing a condenser to which the present invention is directed; Fig. 18 is a cross sectional view taken along line V-V in Fig. 17, the view showing a conventional jointing structure including an outgoing pipe, upper header pipe and a heat transfer tube; Fig. 19 is a cross sectional view taken along line IV-IV in Fig. 15, the view showing a conventional jointing structure including an upper header pipe and a heat transfer tube; Fig. 20 is a cross-sectional view taken along line VI-VI in Fig. 19; Fig. 21 is a cross-sectional view taken along line IV-IV in Fig. 15, the view showing another conventional jointing structure including an upper header pipe and a heat transfer tube; and Fig. 22 is a cross-sectional view taken along line VII-VII in Fig. 21. DETAILED DESCRIPTION OF A PARTICULAR EMBODIMENT Figs. 1 and 2 cooperatively show a particular embodiment of the present invention. A basic construction of the condenser to which the invention is applied is substantially the same as of the conventional condensers as shown in Fig. 17. The condenser constructed according to the invention is different from the conventional one in a relative position of the opening 32 of the outgoing pipe 22, which is coupled with the upper header pipe 6a, to the upper openings 33 of the heat transfer tubes 7 horizontally adjacent to each other. The description which follows will be given placing emphasis on the different portion of the present invention while using like reference numerals for designating like or equivalent portions in the conventional condenser. As shown, while the upper openings 33 of the heat transfer tubes 7 are located substantially in the middle of the inner space of the upper header pipe 6a, the opening 32 of the outgoing pipe 22 is placed in the lower part of the inner space of the upper header pipe 6a. Accordingly, the opening 32 of the outgoing pipe 22 is positioned below the upper openings 33 of the heat transfer tubes 7. Since the opening 32 of the outgoing pipe 22 is placed in the lower part of the inner space of the upper header pipe 6a, the opening 32 of the outgoing pipe 22 is lower than the liquid level L of the liquid refrigerant in the upper header pipe even when the liquid refrigerant staying on the upper header pipe 6a is relatively small. Therefore, it is possible to feed the liquid refrigerant into the outgoing pipe 22 even when the liquid refrigerant staying on the upper header pipe 6a is relatively small. Further, the upper openings 33 of the heat transfer tubes 7 are always positioned above the liquid level of the liquid refrigerant staying in the upper header pipe 6a. Therefore, the refrigerant flowing upward through the heat transfer tubes 7 always flows into the refrigerant vapor in the upper header pipe 6a. Thus, there is no chance that the refrigerant.is discharged from the upper openings 33 of the heat transfer tubes into the liquid refrigerant staying in the lower header pipe. In other words, the liquid refrigerant staying in the upper header pipe does not resist a flow of the refrigerant that is discharged from the heat transfer tubes 7 into the upper header pipe 6a. Thus, the fluid resistance of the condenser 2 is set at a low value of resistance. Further, the jointing structure, which includes the outgoing pipe, the lower header pipe and the heat transfer tubes, prevents the lubricant from staying at and near the end of the upper header pipe 6a which is located most downstream in the direction of flow of the refrigerant. The lubricant is mixed into the refrigerant passing through the condenser 2 to lubricate the compressor 1 (Fig. 14). A velocity of the refrigerant is decreased at and near the end of the upper header pipe 6a which is located most downstream in the direction of flow of the refrigerant since it has been condensed and liquefied, and reduced in its volume. In the jointing structure shown in Fig. 18, the lubricant that has reached the most-downstream end of the upper header pipe 6a and its vicinity, stays on the bottom of the upper header pipe 6a and is hard to be discharged into the outgoing pipe 22, because of reduction of its fluidity. On the other hand, in the jointing structure of the invention, the lubricant that has reached the most-downstream end of the upper header pipe 6a and its vicinity, is efficiently fed into the outgoing pipe 22. The result is that the staying of the lubricant at the most-downstream end of the upper header pipe and its vicinity is lessened to provide a good circulation of the lubricant through the refrigerant cycle in the vapor compression type refrigerator. First Possible Modification Fig.3 shows a first possible modification to the invention. In the modification, a couple of extended portions 36 are axially extended downward from the lower ends of the opening 32 of the outgoing pipe 22. The extended portions 36 are inserted, with their tips 37 first, into the space between the adjacent heat transfer tubes 7 (see Fig. 2) protruded into the inner space of the upper header pipe 6a, while being abutted against the corresponding outer sides of the heat transfer tubes 7 on the bottom thereof, and jointed with the latter by hard soldering. While two extended portions 36 are used in the modification, the use of at least one extended portion 36 suffices. However, a space large enough to allow the liquid refrigerant to pass therethrough must be secured between the root of the extended portion and the bottom of the upper header pipe 6a. In the jointing structure, the outgoing pipe 22 is fixedly supported at two positions, the inner circumferential edge of the connection hole 30 (Figs. 1 and 2) of the upper header pipe 6a and the bottom of the upper header pipe 6a. This ensures a reliable connection of the outgoing pipe 22 to the upper header pipe. The remaining construction and operation of the embodiment are substantially the same as of the invention, and hence the explanation and diagrammatic illustration of them are omitted. The thus constructed condenser of the modification stably exhibits its refrigerating performances independently of the amount of the refrigerant staying in the upper header pipe, and has a low fluid resistance to the flow of the refrigerant, whereby the performance of the automobile air conditioner is improved. Second Possible Modification Figs. 4 and 5 cooperatively show a second possible modification to the present invention. A condenser constructed according to this modification has advantageous features of securing a satisfactory durability of the upper header pipe 6a and reducing an amount of lubricant 34 staying in the upper header pipe 6a. A basic construction of the condenser of this modification is substantially the same as of the conventional one as shown in Figs. 15 to 17. Therefore, the description which follows will be given putting emphasis on the different portion of the present modification whilst using like reference numerals for designating like or equivalent portions in the conventional condenser. A plural number of U-shaped cutouts 38 are formed in the upper ends of a plurality of heat transfer tubes 7, which form a core 9 (Figs. 15 to 17) of a condenser 2. The bottom of each of the cutouts 38 guide a fluid present on and near the bottom of the upper header pipe 6a into the heat transfer tubes 7. With use of the cutouts 38, the lubricant 34 that has reached the bottom of the upper header pipe 6a is introduced into the heat transfer tubes 7 by way of the cutouts 38, and flows downward through the heat transfer tubes 7 to the lower header pipe 6b (Figs. 15 to 17). Since the lower ends of the cutouts 38 are located just above the bottom of the upper header pipe 6a, the lubricant 34 that is left in the upper header pipe 6a after it flows into the heat transfer tubes 7 through the cutouts 38 is small in amount. In the condenser of this modification, the amount of lubricant 34 staying on the bottom of the upper header pipe 6a is reduced. Therefore, the amount of the lubricant 34 circulating in the vapor compression type refrigerator with the condenser incorporated thereinto is increased correspondingly. The shape of the cross section of the upper header pipe 6a remains circular. Therefore, sufficient pressure resistance of the upper header pipe 6a can be secured even if the upper header pipe 6a is thinned. The result is that the weight of the condenser is reduced and the durability thereof is improved. Third Possible Modification Fig. 6 shows a third possible modification to the present invention. A small through-hole 40 is formed in the upper end of each of heat transfer tubes 7. Specifically, a portion of the upper end of the heat transfer tube 7 where the small through-hole 40 is formed is located below the opening of the upper end and just above the bottom surface 39 of the upper header pipe 6a. The small through-holes 40 of the heat transfer tubes guide fluid staying on the bottom of the upper header pipe 6a into the heat transfer tubes 7. The amount of the lubricant 34 staying in the upper header pipe 6a is reduced as in the second modification. In the invention and possible modifications mentioned above, the cutouts 38 or the small through-holes 40 are formed in all the heat transfer tubes 7 forming the core 9. The cutouts 38 or the small through-holes 40 need only be large enough to prevent much lubricant 34 from staying on the bottom of the upper header pipe 6a. For this reason, the cutouts 38 or the small through-holes 14 may be formed only in the heat transfer tubes 7 for guiding the fluid from the upper header pipe 6a to the lower header pipe 6. The cutouts 38 or the small through-holes 40 are not necessarily formed in all the heat transfer tubes 7 for guiding the fluid from the upper header pipe 6a to the lower header pipe 6b. For example, the cutout 38 or the small through-hole 40 may be formed only in one of the heat transfer tubes 7, which guides the fluid from the upper header pipe 6a to the lower header pipe 6b and opened at their upper ends into a chamber in the upper header pipe. This example is able to prevent much lubricant 34 from staying on the bottom of the upper header pipe 6a. Since the condenser of this modification is thus constructed and operated, the contradictive aims of the reducing of the weight and the improving of the durability are well compromised. Therefore, an automobile air conditioner of high performance and low cost is realised. Fourth Possible Modification Fig. 7 shows a condenser which is a fourth modification to the present invention. The basic construction of the condenser that is designated by reference numeral 2 and constructed according to the concept of the invention is substantially the same as of the conventional one as shown in Figs. 15 and 16 except that the positions of the walls for partitioning the upper and lower header pipes are different from those of the conventional one. As shown in Fig. 7, the condenser 2 of the present modification includes a couple of upper and lower header pipes 6a and 6b, an upper partitioning wall 13 for partitioning the inner part of the upper header pipe 6a into a first upper chamber 15 and a second upper chamber 16, and a lower partitioning wall 14 for partitioning the inner part of the lower header pipe 6b into a first lower chamber 17 and a second lower chamber 18. A plural number of heat transfer tubes 7, vertically arranged between the header pipes, are classified into three groups of heat transfer tubes; first heat transfer tubes 19, second heat transfer tubes 20, and third heat transfer tubes 21. The first heat transfer tubes 19 are located most upstream in the direction of a refrigerant current. A refrigerant flows downward through those first heat transfer tubes 19. The second heat transfer tubes 20 is located between the first heat transfer tubes 19 and the third heat transfer tubes 21. The refrigerant flows upward through those second heat transfer tubes 20. The third heat transfer tubes 21 are located most downstream in the direction of a refrigerant current. The refrigerant flows downward through those third heat transfer tubes 21. The number of the first to third heat transfer tubes 19, 20 and 21 in the condenser 2 is different from that of those heat transfer tubes in the conventional one as shown in Figs. 15 and 16. Specifically, a total passage area S19 of the first heat transfer tubes 19 is larger than a total passage area S20 of second heat transfer tubes 20. The total passage area S20 of the second heat transfer tubes 20 is equal to or smaller than a total passage area S21 of third heat transfer tubes 21. The first heat transfer tubes 19 allow the refrigerant to flow downward from the first upper chamber 15 to the first lower chamber 17. The second heat transfer tubes 20 allow the refrigerant to flow upward from the first lower chamber 17 to the second upper chamber 16. The third heat transfer tubes 21 allow the refrigerant to flow downward from the second upper chamber 16 to the second lower chamber 18. The relation of those total passage areas S19, S20 and S21 are: S19 > S20 ≤ S21. It is noted here that the total passage area S20 of the second heat transfer tubes 20 for upward flowing of the refrigerant is smaller than the total passage area S19 of the first heat transfer tubes 19 for downward flowing of the refrigerant and equal to or smaller than the total passage area S21 of the third heat transfer tubes 21 for downward flowing of the refrigerant. Therefore, a velocity of flow of the refrigerant flowing through the second heat transfer tubes 20 is increased. And the lubricant that has reached regions at and near to the lower partitioning wall 14 in the lower header pipe 6b is fed into the second heat transfer tubes 20, together with the refrigerant. The result is that a necessary amount of the lubricant that is fed, together with the refrigerant, to the compressor is secured, and the durability of the compressor is improved. Fifth Possible Modification Fig. 8 shows a condenser which is a fifth modification to the present invention. In the condenser 2, two upper partitioning walls 13 are used, and the heat transfer tubes 7 comprises four groups of heat transfer tubes; first to fourth heat transfer tubes 19, 20, 21 and 23. The fourth heat transfer tubes 23 are located downstream of the third heat transfer tubes 21 and allows the refrigerant to flow upward. A total passage area S19 of the first heat transfer tubes 19 is larger than a total passage area S20 of the second heat transfer tubes 20. The total passage area S20 of the second heat transfer tubes 20 is equal to or smaller than a total passage area S21 of the third heat transfer tubes 21. A total passage area S23 of the fourth heat transfer tubes 23 is smaller than the total passage area S21 of the third heat transfer tubes 21. A relation among those total passage areas S19, S20, S21 and S23 is: S19 > S20 ≤ S21 > S23. Thus, the total passage area S20 of the second heat transfer tubes 20 for upward flowing of the refrigerant is smaller than the total passage areas S19 and S21 of the first and third heat transfer tubes 19 and 21 for downward flowing of the refrigerant or equal to the total passage area S21. Further, the total passage area S23 of the fourth heat transfer tubes 23 for upward flowing is smaller than the total passage area S21 of the third heat transfer tubes 21 for downward flowing. Therefore, the lubricant, together with the refrigerant, is efficiently fed into the second and fourth heat transfer tubes 20 and 23. The technical idea of this modification is applicable to a case where the number of the lower partitioning walls is increased and the number of the groups of heat transfer tubes 7 forming the core 9 is increased. In this case, the total passage area of each group of the heat transfer tubes for upward flowing is equal to or smaller than that of each group of the heat transfer tubes for downward flowing. In the condenser thus constructed, an amount of the lubricant (mixed into the refrigerant) staying in the vicinity of the lower partitioning wall is reduced. Therefore sufficient lubricant to be fed to the compressor is secured to thereby improve the durability of the automobile air conditioner having the compressor assembled thereinto. In the fourth and fifth modifications, it is merely a requirement that the total passage area (number of tubes) of a group of the upward-flow heat transfer tubes is equal to or smaller than the total area (number of tubes) of a group of the downward-flow heat transfer tubes which is located downstream of the group of upward-flow heat transfer tubes. Further, the number of heat transfer tubes in the group of upward-flow heat transfer tubes is the smallest among all groups of heat transfer tubes. In the above modifications, it is described about the case that the heat transfer tubes are classified to three or four groups. However, the number of groups is not limited to three or four, and it is possible to apply the present invention to the condensers having the various number of groups of the heat transfer tubes. First Comparative Example Fig. 9 shows a condenser which is a first comparative example to the present invention. The basic construction of a condenser 2 of this comparative example is substantially the same as of the conventional condenser as shown in Fig. 15. The position in the horizontal direction where the outgoing pipe 22 defining an outgoing port in the condenser 2 of this example is located is different from that in the conventional condenser as shown in Fig. 15. For simplicity of explanation, description will be given placing emphasis on the different portions of the condenser. In the condenser 2 of this example, the outgoing pipe 22 defining the outgoing port, as shown in Fig. 9, is provided at a position close to the left end (in Fig. 9) of the lower header pipe 6b. The upper end of the outgoing pipe 22 is opened into a portion of the lower header pipe 6b which is coupled with the lower ends of the third heat transfer tubes 21 which are located close to the side plate 10a. The portion (the left end in Fig. 9) is located most downstream in the direction in which the refrigerant flows in the upper header pipe 6a. In the condenser thus constructed, there is no chance that the liquid refrigerant that has flowed down through the third heat transfer tubes 21 located closer to the center (the right-hand side in Fig. 9) of the core 9, directly reaches the upper end opening of the outgoing pipe 22. The liquid refrigerant flows down, through the third heat transfer tubes 21 located close to the center of the core 9, onto the second lower chamber 18, and flows to the left end of the lower header pipe 6b. And the liquid refrigerant is mixed with the gaseous refrigerant which has flowed down onto the second lower chamber 18, through the third heat transfer tubes 21 located close to the left end of the core 9. Therefore, even if the refrigerant that has reached the second lower chamber 18 is a mixture of the liquid refrigerant and the gaseous refrigerant, there is no chance that only the liquid refrigerant flows into the outgoing pipe 22. The result is that the refrigerant flowing into the outgoing pipe 22 is always the mixture of the liquid refrigerant and the gaseous refrigerant, and that the discharging of the refrigerant out of the condenser is stabilized. Second Comparative Example Fig. 10 shows a condenser which is a second comparative example to the present invention. In this example a part of the lower header pipe 6b is extended outward beyond the right side (in the figure) of the core 9 to form an extended part 43. The lower end of an outgoing pipe 44 is coupled with the upper surface of the extended part 43. The upper end of the outgoing pipe 44 is opened to form an outgoing port 24. In the thus constructed condenser 2, as in the first comparative example, there is no chance that the liquid refrigerant that has flowed down, through some of the third heat transfer tubes, into the second lower chamber 18 directly reaches the upper end opening of the outgoing pipe 44. Therefore, the condenser 2 of this example prevents only the liquid refrigerant from going into the outgoing pipe 44, feeds the mixture of the liquid refrigerant and the gaseous refrigerant to the outgoing pipe 44, and hence stabilizes the discharging of the refrigerant from the core. In this example, while the refrigerant is discharged from the lower header pipe 6b, the outgoing port 24 is provided in the upper part of the condenser 2. This structural feature provides an easy piping and improves a layout freedom of the vapor compression type refrigerator. The remaining construction and operation of the present example are substantially the same as of the first comparative example. However, in this example, the flow direction of the refrigerant is different from the aforementioned embodiments. It is a matter of design, and may properly be selected in accordance with the body structure of an automobile to which Third Comparative Example Figs. 11 and 12 show a condenser which is a third comparative example to the present invention. In the condenser 2 of this example, a part of the lower header pipe 6b is extended outward beyond the right side of the core 9 to form an extended part 43, as in the condenser 2 of the second comparative example. A cap 45 is attached to the end face of the extended part 43 to close the open end of the same. The lower end of the outgoing pipe 44 defining the outgoing port 24 at the upper end is coupled with the upper surface of the extended part 43 with the cap 45 intervening therebetween. Specifically, the lower end of the outgoing pipe 44 is applied across the cap 45 while communicating with the lower header pipe 6b through the cap 45. The outer circumferential surface of the lower end of the outgoing pipe 44 is fastened to the end face of the lower header pipe 6b in a state that the cap 45 is inserted therebetween. Therefore, the structure of the condenser 2 has a higher rigidity against the forces having the directions of arrows (Fig. 12) than the structure of the second comparative example shown in Fig. 10. The remaining construction and operation of this example are substantially the same as of the second comparative example. Fourth Comparative Example Fig. 13 shows a condenser which is a fourth comparative example to the present invention. In the condenser 2 of this example, a part of the lower header pipe 6b is not extended outward beyond the right side of the core 9 to form an extended part 43, unlike the condensers of the second and third examples mentioned above. The lower part of the outgoing pipe 44 is bent to form a corner 46 curved like a 1/4 arc, and the curved corner 46 is further extended horizontally and straightforwardly to form a horizontal part 47. The open end of the horizontal part 47 is brazed to the end of the lower header pipe 6b. In the condenser, the lower header pipe 6b and the outgoing pipe 44, which are different in diameter, are coupled with each other in an end-to-end fashion. To this end, the end of the outgoing pipe 44 having a smaller diameter is flared and the flared end is abutted against the end of the lower header pipe 6b, and bonded to each other by brazing. In an alternative, the end of the lower header pipe 6b is reduced in diameter and the reduced end of the same is abutted against the end of the outgoing pipe 44. The condenser of this example is advantageous in that it is easy to form the connecting part of the lower header pipe 6b and the outgoing pipe 44, and therefore, the cost to manufacture the condenser 2 is reduced. Another advantage of the condenser is that the structure prevents no abrupt change in the refrigerant flow at the connection part, and hence prevents an increase of resistance of the connection part to the refrigerant flow. The condenser thus constructed and operated is able to stabilize the discharging operation of the refrigerant and to improve the performances of the automobile air conditioner. The aforementioned invention and possible modifications can be combined with two or more auxiliarily, and it is possible to adopt various combinations of the aforementioned modifications.

Claims: A condenser (2) assembly structure comprising: an upper header pipe (6a) arranged horizontally; a lower header pipe (6b) arranged parallel to said upper header pipe (6a); a plural number of heat transfer tubes (7) arranged vertically between said upper (6a) and lower (6b) header pipes, upper and lower ends of said heat transfer tubes (7) opening into inner parts of said upper and lower header pipes; and an outgoing pipe (22) coupled to said upper header pipe (6a), wherein a refrigerant flows through said upper (6a) and lower (6b) header pipes and said heat transfer tubes (7) and flows out through an opening (32) in said outgoing pipe (22), characterised in that the opening (32) of said outgoing pipe is positioned below the upper openings (33) of said heat transfer tubes (7) in the inner space of said upper header pipe (6a). The condenser assembly structure according to claim 1, wherein said outgoing pipe (22) is coupled to and passes through an upper side of said upper header pipe (6a). The condenser assembly structure according to claim 2, wherein said outgoing pipe (22) has at least one extended portion (36) extending downward from a circumferential edge of said opening (32) of said outgoing pipe, said at least one extended portion (36) is inserted into a space between the upper ends of adjacent heat transfer tubes (7), and a tip end (37) of said at least one extended portion (36) is abutted against an inner bottom portion (39) of said upper header pipe (6a). A condenser assembly structure as claimed in any one of the preceding claims, wherein a fluid passage (38,40) is formed at an upper end of at least one of said heat transfer tubes (7), said fluid passage (38,40) located below said upper end of said at least one heat transfer tube and just above an inner bottom portion (39) of said upper header pipe (6a) so as to guide fluid accumulated at the inner bottom portion (39) of said upper header pipe (6a) into said at least one heat transfer tube (7). The condenser assembly structure according to claim 4, wherein said fluid passage is a cutout (38) extending from said upper end of said at least one heat transfer tube (7) to just above the inner bottom portion (39) of said upper header pipe (6a). The condenser assembly structure according to claim 4, wherein said fluid passage is a through-hole (40) formed between said upper end of said at least one heat transfer tube (7) and just above the bottom portion (39) of said upper header pipe (6a). A condenser according to any one of the preceding claims, wherein said plural number of heat transfer tubes (7) are classified into upward-flow heat transfer tubes or downward-flow heat transfer tubes, through which a refrigerant including a lubricant flows upward or downward respectively, and groups (20,23) of said upward-flow heat transfer tubes (7) and groups (19,21) of said downward-flow heat transfer tubes (7) are distributed alternatively in a horizontal direction, and wherein the total passage area of a group (20,23) of said upward-flow heat transfer tubes (7) is equal to or smaller than the total passage area of a group (19,21) of said downward-flow heat transfer tubes (7) which is located downstream of said group (20,23) of upward-flow heat transfer tubes (7). The condenser assembly structure according to claim 7, wherein the number of heat transfer tubes (7) said group (20,23) of upward-flow heat transfer tubes (7) is equal to or smaller than the number of heat transfer tubes in said group (19,21) of downward-flow heat transfer tubes (7) which is located downstream of said group (20,23) of upward-flow heat transfer tubes (7).

Inventors: ASANUMA TORU, INABA HIROYUKI, ASANUMA, TORU, INABA, HIROYUKI
Applicants: CALSONIC KANSEI CORP, CALSONIC KANSEI CORPORATION
Application year: 1997
Main classification: F25B39
IPC codes: F25B39, F28F9, F28D1