Outlet/inlet piping structure for intercooler

Abstract

An outlet/inlet piping structure of an intercooler according to the invention has a construction in which an outlet/inlet piping 5 is branched in such a fashion as to possess a plurality of flow passages from one of the flow passages of a distal end position 5a spaced apart from a header tank 4 of an intercooler to a connection portion 5b to the header tank so that a fluid pressure loss does not substantially occur in the flow between the distal end position and the connection portion. In other words, a ratio of a sectional area of the flow passage of the connection portion to a sectional area of the connection portion of the far end portion is at least 78%.

Description

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] This invention relates to an outlet/inlet piping structure for an intercooler for causing high-pressure air from a supercharger to flow into an intercooler, cooling the high-pressure air and sending the high-pressure air to an engine main body in a feed system of an internal combustion engine (engine).

[0003] 2. Description of the Related Art

[0004] To improve an engine output, it has generally been a customary practice to send a large quantity of air into an engine using a supercharger. Because air is compressed in the supercharger, however, the air temperature rises and the air changes to high-pressure air having a temperature of about 180.degree. C., for example. An intercooler (cooler) is used to increase the air density by cooling this high-pressure air before it is fed to the engine main body.

[0005] The intercooler generally includes a heat exchange core 3 formed by alternately stacking a large number of flat tubes 1 and a large number of corrugated fins 12 as shown in FIG. 7 and header tanks 4 are arranged on both sides of this heat exchange core 3. The header tank 4 is constituted by a core plate 41, to which a large number of tubes 1 are connected, and a tank plate 42 having a U-shaped sectional shape for forming a tank space, as shown in FIG. 8. An inlet piping 5 is connected to the substantial top of the header tank in the case of an inlet side header tank 4, for example, and an outlet piping 5 (not shown in the drawing) is connected in the case of an outlet side header tank (not shown).

[0006] In the intercooler having such a construction, the high-pressure air pressurized by the supercharger enters the inlet side header tank 4 through the inlet piping 5, then enters the outlet side header tank through a large number of flat tubes 1 and is discharged from this outlet side header tank through the outlet piping to the engine. On the other hand, external air, due to the movement of a car and a cooling fan, flows orthogonally to the flowing direction of the high-pressure air outside the tubes 1, thereby causing a heat exchange and cooling the high-temperature and high-pressure air. In this way, the intercooler generally employs a high-pressure air flow of single pass system.

[0007] Therefore, to improve heat exchange efficiency, it is necessary to allow the high-pressure air from the inlet piping 5 to flow in a broader range and to uniformly distribute the high-pressure air to a large number of flat tubes 1. In the intercoolers of the prior art, the tip end of the inlet piping 5 is shaped into a flat shape as shown in FIG. 7 and is connected to the header tank 4. (Incidentally, this is fundamentally the same in the case of the outlet piping, too). In this way, the high-pressure air is allowed to flow uniformly through each tube 1.

[0008] To cope with the environmental pollution, the exhaust gas regulation of Diesel engines has become more severe in recent years. In the case of large trucks, for example, the NOx value of the exhaust gas in Europe has changed from 5 (g/kwh) in EURO3 to 3.5 (g/kwh) in EURO4 and is expected to be 2 (g/kwh) in EURO5 which is scheduled to start from 2008. The PM (floating particulate matter) value is reduced from 0.1 (g/kwh) of EURO3 to 0.02 (g/kwh) in EURO5.

[0009] To avoid these regulation limits, it is necessary to improve the pressure of the high-pressure air outgoing from the existing superchargers from 1.8 (kgf/cm.sup.2) through 2.7 (kgf/cm.sup.2) to a final target value of 3.6 (kgf/cm.sup.2) and to raise the temperature of the high-pressure air from 180.degree. C. to 204.degree. C. to 239.degree. C.

[0010] As described above, both the supercharging pressure and the temperature have been drastically increased in the intercoolers for the large scale trucks owing to exhaust gas regulations.

[0011] In the outlet/inlet piping structure (particularly the inlet piping structure) according to the prior art in which the tip end of the outlet/inlet piping (connection portion with the header tank) has a flat shape, however, the possibilities occur, with the rise of the supercharging pressure and temperature owing to tightening of the exhaust gas regulation, that the strength becomes insufficient and the outlet/inlet piping undergoes deformation.

[0012] In other words, the flat tip end of the outlet/inlet piping is likely to swell into a round shape. The deformation of the tip end of the outlet/inlet piping may result in the problems that a tank plate 42 and a core plate 41 are pulled as indicated by dash line in FIG. 8 and deform and, eventually, a large stress acts on a tube root R connecting the core plate and the tube by brazing, etc, and results in a fracture. The intercoolers according to the prior art employ the wide pipe shape so as to let the supercharging air flow in a broader range but the pressure receiving area is large and deformation is more likely to occur.

SUMMARY OF THE INVENTION

[0013] In view of the problems described above, the present invention aims to provide an outlet/inlet piping structure of an intercooler that can uniformly supply a fluid to each tube connected to a header tank, has strength sufficient to suppress deformation against the fluid that is highly pressurized, and can reduce the stress on a tube root.

[0014] According to one aspect of the present invention, an outlet/inlet piping structure of an intercooler has a construction in which outlet and inlet piping 5, 5A and 5B are divided in such a fashion as to possess a plurality of flow passages from one flow passage at a distal end position 5a spaced apart from header tanks 4, 4A, 4B of the intercooler to a connection portion 5b to the header tanks, and a fluid pressure loss does not substantially occur between the distal end position 5a and the connection portion 5b. Accordingly, the pressure reception area can be reduced without decreasing a flow passage sectional area, the strength of the outlet/inlet piping 5A, 5B can be increased, its deformation can be suppressed and damage to, and fracture of, the tube root R of the intercooler can be prevented. The fluid can be uniformly supplied to each tube connected to the header tanks.

[0015] In the outlet/inlet piping structure according to the invention, a ratio of a sectional area of the flow passage of the connection portion 6b to a sectional area of the flow passage of the distal end position 5a is at least 78%. The outlet/inlet sectional area ratio of the outlet/inlet piping is measured by a pressure loss of supercharging air but a measurement error of .+-.5% generally exists in the measurement of the pressure loss. Therefore, the invention employs an outlet/inlet sectional area ratio of at least 78% corresponding to +5% as the upper limit at which the difference becomes clear. This is equivalent to a construction in which the pressure loss basically does not occur in the outlet/inlet piping.

[0016] In the outlet/inlet piping structure according to the invention, the outlet/inlet piping 5, 5A, 5B is formed by combining half split members divided into a plurality of units in an axial direction of tubes with one another and fixing them. Therefore, production is easy and a production cost can be reduced.

[0017] An intercooler according to another aspect of the invention includes two header tanks 4A and 4B on the inlet side and the outlet side, an inlet piping 5A provided in the inlet side header tank 4A, a heat exchange core 3 connected to both header tanks 4A and 4B, and an outlet piping 5B provided in the outlet side header tank 4B, wherein at least one of both piping 5A and 5B is branched in such a fashion as to possess a plurality of flow passages from one of the flow passages of the distal end position 5a spaced apart from the inlet side header tank 4A to the connection portion 5b to the inlet side header tank 4A so that a fluid pressure loss does not substantially occur between the distal end position 5a and the connection portion 5b. Consequently, it is possible to acquire an intercooler including an inlet piping having improved pressure resistance.

[0018] The present invention may be more fully understood from the description of preferred embodiments of the invention, as set forth below, together with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In the drawings:

[0020] FIG. 1A is a view showing an upper half structure of an intercooler equipped with an outlet/inlet piping structure according to an embodiment of the present invention;

[0021] FIG. 1B an explanatory view useful for explaining deformation of an outlet/inlet piping at a connection portion;

[0022] FIG. 2 is a graph showing the relation between an outlet (connection side)/inlet (distal end portion side) sectional area ratio and a supercharging pressure loss of the intercooler;

[0023] FIG. 3 is a front view of an intercooler equipped with an outlet/inlet piping structure according to another embodiment of the invention;

[0024] FIG. 4 is an explanatory view useful for explaining difficulties in processing of an outlet/inlet piping structure having completely branched flow passages according to the embodiment of the invention;

[0025] FIG. 5 is a sectional view showing an outlet/inlet piping structure in each embodiment (a) to (d) and taken along a line V-V in FIG. 4;

[0026] FIGS. 6A and 6B show outlet/inlet piping structures according to two more embodiments of the invention;

[0027] FIG. 7 is an upper half view of an intercooler equipped with an outlet/inlet piping structure according to the prior art;

[0028] FIG. 8 is an explanatory view useful for explaining deformation of a header tank of the outlet/inlet piping structure of the prior art before and after pressurization; and

[0029] FIG. 9 is a graph useful for explaining a trend of an exhaust gas regulation value in EURO (Europe) and the change of pressure and temperature of high-pressure air after supercharging.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] An outlet/inlet piping structures of intercoolers according to preferred embodiments of the invention will be hereinafter explained with reference to the accompanying drawings.

[0031] FIG. 1A shows an upper half structure of an intercooler equipped with an outlet/inlet piping structure according to an embodiment of the invention, and FIG. 1B is an explanatory view useful for explaining deformation of an outlet/inlet piping at a connection portion. Though the invention will be explained with regard to an intercooler for cooling high-pressure air from a supercharger and sending it to an internal combustion engine (engine), the invention can be appropriately applied to heat exchangers other than an intercooler.

[0032] FIG. 1A shows only the upper half structure of the intercooler because the lower half has substantially the same structure. Therefore, the lower half is omitted from the drawing.

[0033] As shown in FIG. 1A, the intercooler includes a heat exchange core 3 that is formed by alternately stacking a large number of flat tubes 1 and a large number of corrugated fins (corrugate fins) 2, and header tanks 4 that are arranged on both sides of this heat exchange core 3. Each header tank 4 includes a core plate 41 to which a large number of tubes 1 are connected and a tank plate 42 having a U-shaped sectional shape that defines a tank space. Incidentally, the side surface of the header tank 4 is closed by a side plate. Incidentally, a large number of flat tubes 1 constituting the heat exchange core 3 are generally arranged with the longitudinal direction of the flat section of the tube 1 being in conformity with the flowing direction of a fluid (external air) flowing outside the tubes 1, but are aligned in parallel in a direction crossing at right angles the flow in this embodiment.

[0034] Both header tanks 4 to be connected at both ends of the flat tubes 1 are arranged in the vertical direction of a car. An inlet piping 5A is connected to the upper end of the inlet side header tank 4A and an outlet piping 5B (not shown in the drawing) is connected to the upper end of an outlet side header tank 4B, not shown (at the lower end when depicted in FIG. 1A). Incidentally, both header tanks 4 may be arranged in the transverse direction of the car. The inlet piping 5A and the outlet piping 5B generally have the same shape for the sake of production and the term "outlet/inlet piping structure" used in the embodiments generically represents both of inlet piping 5A and outlet piping 5B. As high-pressure air is pressurized by the supercharger, the air density increases when the air is cooled by the intercooler. Because the pressure and temperature conditions are severe for the inlet piping 5A and are mitigated on the side of the outlet piping 5B, their structure need not always be the same, but the outlet/inlet piping structure according to this embodiment must be employed for at least the side of the inlet piping 5A.

[0035] The other end of the inlet piping 5A is connected to the piping on the supercharger side for passing the high-pressure air from the supercharger and the other end of the outlet piping 5B is connected to an engine side piping for sending the high-pressure air to the engine main body.

[0036] In the intercooler having the construction described above, air (feed air) pressurized by the supercharger enters the inlet side header tank 4A through the inlet piping 5A, flows from thence into the outlet side header tank 4B through the tubes 1 of the heat exchange core 3 and is sent to the engine main body through the outlet piping 5B. On the other hand, external air sucked by a cooling fan (not shown) and driving wind taken in when the car is running flow outside the tubes 1 in such a fashion as to penetrate the drawing sheet from the front side of the sheet to the back side thereof and a cross the high-pressure air flow inside the tubes 1. In consequence, the high-pressure air and the external air exchange heat, and the high-pressure air that is about 180.degree. C. on the inlet side of the intercooler, for example, is cooled to about 50.degree. C. on the outlet side. Therefore, as the high-pressure air is cooled, its density increases, the packing efficiency of the air fed to the engine increases and the output is improved.

[0037] Next, the outlet/inlet piping structure as the feature of the present invention will be explained. The intercooler is of the type in which the high-pressure air passes only once between both header tanks 4A and 4B (single pass type) and the high-pressure air must be uniformly fed to each tube 1. Therefore, the connection portion at which the outlet/inlet piping 5 is connected to the header tank 4 is shaped into the flat shape. When the piping 5 is shaped into the flat shape, however, the pressure receiving area increases as shown in FIG. 7, so that the pressure resistance drops and the connection portion undergoes great deformation, thereby inviting possible damage and fracture of the tube root R.

[0038] Therefore, this embodiment employs the structure in which the outlet/inlet piping 4 is divided into a plurality of units. In other words, the distal end portion 5a of the outlet/inlet piping 5 far spaced apart from the header tank 4 has only one flow passage but the outlet/inlet piping 4 is divided into a plurality of units at the connection portion 5b of the outlet/inlet piping 5 connected to the header tank 4 in such a fashion as to possess a plurality of flow passages 52 and 53 that are integrally formed with one another. In this case, the sectional shape of the flow passage of the distal end portion 5a is round for the connection with the supercharger piping whereas the sectional shape of the flow passages 52 and 53 of the connection portion 5b may be round but is more preferably elliptic. When the sectional shape of the flow passages 52 and 53 of the connection portion 5b is elliptic (flat), the distribution factor of the high-pressure air to each tube 1 can be improved. As the outlet/inlet piping 4 is divided into a plurality of flow passages 52 and 53 at the connection portion 5b as shown in FIG. 1B, the pressure receiving area per flow passage 52, 53 becomes smaller, the degree of deformation of the flow passages 52 and 53 decreases and the stress of the tube root can be reduced.

[0039] It is also necessary to employ the construction that does not create the pressure loss of the fluid in the flow passage extending from the distal end portion 5a of the outlet/inlet piping 4 to the connection portion 5b. Therefore, the sectional area is substantially the same in the full flow passage from the distal end portion 5a to the connection portion 5b or is greater on the side of the connection portion 5b. In this case, measurement of the pressure loss is executed by measuring the proportion of the sectional area of the flow passage of the distal end portion 5a to the sectional area of the flow passage of the connection portion 5b. In such a measurement of the pressure loss, a measurement error of about .+-.5% generally exists. FIG. 2 is a graph showing the relation between the outlet (connection side)/inlet (distal end portion side) sectional area ratio and the supercharging pressure loss of the intercooler. According to this graph, the outlet/inlet sectional area is preferably at least 78% that corresponds to +5% as the upper limit at which the error becomes remarkable. In other words, the outlet/inlet piping structure is employed in which the sectional area of the flow passages 52 and 53 of the connection portion 5b to the sectional area of the flow passage of the distal end portion 5a in the outlet/inlet piping 5 is at least 78%.

[0040] FIG. 3 shows an outlet/inlet piping structure of an intercooler according to another embodiment of the present invention. The foregoing embodiment has been explained on the assumption that the structure of the inlet piping 5A is substantially the same as that of the outlet piping 5B but in this embodiment, their piping structures are different. In other words, there is the possibility that only the piping on the inlet side is an end protrusion pipe owing to the space limitation inside the engine compartment when the intercooler is mounted to the car. In such a case, the inlet piping 5A is connected to the side surface of the inlet side header tank 4A (on the right side of the inlet side header tank 4A in FIG. 3) so that the inlet side of the high-pressure air is arranged on one of the sides of the direction orthogonally crossing the direction of the tube axis of the flat tubes 1 as shown in FIG. 3. This inlet piping 5A is a piping having a single structure that is not branched.

[0041] On the other hand, the outlet piping 5B connected to the outlet side header tank 4B has a split structure of a plurality of tubes in the same way as in the foregoing embodiment and is connected to the upper part of the outlet side header tank 4B. In this way, only one of the inlet piping 5A and the outlet piping 5B of the outlet/inlet piping structure may be branched. Incidentally, the construction of other members such as the tubes 1, the fins 2 and the heat exchange core 3 is the same as in the foregoing embodiment and its explanation will be omitted.

[0042] In the foregoing embodiment, the outlet/inlet piping 5 has the completely branched structure (refer also to FIG. 5A) as shown in FIG. 4. In this case, there remain the problems that an inner portion 51 of the branched piping (represented by thick solid line in FIG. 4) must be bonded by welding or brazing and that drawing must be excessively applied by pressing during shaping with the result of the drop of the processing factor.

[0043] Therefore, a structure, in which the outlet/inlet piping 5 is not completely branched may be employed.

[0044] FIG. 5 is a sectional view taken along a line V-V in FIG. 4 and showing an embodiment of the structure that is completely branched structure and an embodiment of the structure that is not completely branched. FIG. 5(a) shows the section of the outlet/inlet piping 5 having the completely branched flow passages 52 and 53. FIG. 5(b) shows the section of the outlet/inlet piping 5 that has branched flow passages 52 and 53 and a flow passage 54 connecting both flow passages 52 and 53, and the construction that is not completely branched. The flow passage 54 is shaped into a flat shape and can restrict deformation of the branched flow passages 52 and 53. In this case, however, as the flow passages 52 and 53 are not completely branched, the deformation restriction effect is smaller than when the flow passages 52 and 53 are completely branched, but is superior, in processing factor, to the case where they are completely branched.

[0045] FIG. 5(c) shows the section of the outlet/inlet piping 5 having a construction which is not completely branched and in which a support pole 55 is arranged in the flat flow passage 54 connecting the branched flow passages 52 and 53. Because the support pole 55 is disposed, the strength of the flat flow passage 54 can be improved and the deformation restriction effect of the branched flow passages 52 and 53 can be improved.

[0046] FIG. 5(d) shows the section of the outlet/inlet piping 5 having a construction which is not completely branched and in which the flow passage 54 connecting the branched flow passages 52 and 53 is narrowed until it comes into contact (by bringing the upper and lower inner surfaces of the flow passage 54 into mutual contact) and is bonded by spot welding W, etc, to close the flow passage 54. In this case, the deformation restriction effect is substantially equal to that of the outlet/inlet piping 5 having the completely branched structure and the processing factor can be improved.

[0047] FIGS. 6A and 6B show outlet/inlet piping structures according to two embodiments of the invention. In these embodiments, the outlet/inlet piping 5 is formed by combining half split members that are equally split into two units in the axial direction of the tube, and fixing them by welding, brazing, or the like. FIG. 6A shows an outlet/inlet piping 5 in which a connection portion 5b has two branched flow passages and FIG. 6B shows an outlet/inlet piping 5 in which a connection portion 5b has three branched flow passages. In these embodiments, the two half split members are fixed and integrated to give the outlet/inlet piping 5 but the outlet/inlet piping 5 may well be integrated from the beginning by casting or like means. Examples of the materials of the outlet/inlet piping 5 are stainless steel, iron, aluminum (inclusive of aluminum alloys) and copper (inclusive of copper alloys).

[0048] As explained above, the present invention can decrease the pressure receiving area per flow passage of the outlet/inlet piping at the connection portion with the header tank at which the pressure receiving area attains the maximum in the prior art products, and can reduce the deformation amount at the connection portion.

[0049] As the degree of deformation at the connection portion of the outlet/inlet piping can thus be reduced, deformation of the tank plate and the core plate that are pulled by the outlet/inlet piping can be limited and the tube root stress can be reduced.

[0050] While the invention has been described by reference to specific embodiments chosen for purposes of illustration, it should be apparent that numerous modifications could be made thereto by those skilled in the art without departing from the basic concept and scope of the invention.

Claims

1. An outlet/inlet piping structure of an intercooler for causing high-pressure air from a supercharger to flow into an intercooler and sending the high-pressure air, the air density of which is increased upon cooling, from said intercooler to an engine main body, wherein at least one of an inlet piping and an outlet piping has a construction such that it is divided into a plurality of flow passages from one flow passage at a distal end position spaced apart from a header tank of said intercooler to a connection portion to said header tank, and a fluid pressure loss does not substantially occur between said distal end position and said connection portion.

2. An outlet/inlet piping structure of an intercooler according to claim 1, wherein a sectional area of the flow passage of said connection portion to a sectional area of the flow passage of said distal end position is at least 78%.

3. An outlet/inlet piping structure of an intercooler according to claim 1, wherein said outlet/inlet piping structure is formed by combining half split members divided into a plurality of units in an axial direction of tubes with one another and fixing them.

4. An outlet/inlet piping structure of an intercooler according to claim 1, wherein a flat flow passage connecting said divided flow passages is provided.

5. An outlet/inlet piping structure of an intercooler according to claim 4, wherein a support pole is arranged in said flat flow passage.

6. An intercooler comprising: two header tanks on an inlet side and an outlet side so arranged as to oppose each other; an inlet piping connected to a supercharger side piping for passing high-pressure air from a supercharger and provided in said inlet side header tank; a heat exchange core connected to both of said header tanks, for cooling the high-pressure air flowing in from said inlet piping and increasing an air density; and an outlet piping connected to an engine side piping for sending the high-pressure air to the engine main body and provided on said outlet side header tank; wherein at least one of said inlet piping and said outlet piping is branched in such a fashion as to possess a plurality of flow passages from one of the flow passages of a distal end position spaced apart from said inlet side header tank to a connection portion to said inlet side header tank so that a fluid pressure loss does not substantially occur between said distal end position and said connection portion.