Intake manifold

Abstract: An intake manifold (10) comprising a main pipe (20) made of wrought aluminum material and having an open end, a closed end opposite to the open end, a plurality of holes (21) formed in its peripheral wall and outward tubular projections (22) integral with the peripheral wall and each formed around each of the holes, and a plurality of branch pipes (30) made of wrought aluminum material and each having one end fitting in and joined to each of the tubular projections. The manifold is smooth-surfaced in its interior, diminished in resistance to air and improved in air intake efficiency. The manifold requires no finishing procedure unlike those prepared by casting.

Description: The present invention relates to an intake manifold according to the preamble of claim 1. The term "aluminum" as used herein and in the appended claims includes pure aluminum, commercial aluminum containing a small amount of impurities and aluminum alloys. Further the term "wrought aluminum material" as used herein and in the appended claims includes products prepared by plastic working. Intake manifolds have heretofore been prepared entirely by casting for use in motor vehicle gasoline engines equipped with an electronically controllable fuel injection system. However, since the cast product has a rough surface, the conventional intake manifold must be made smooth-surfaced at least in its interior by a cumbersome finishing procedure in order to assure diminished air resistance and thereby achieve an improved air intake efficiency. Further it is impossible to finish the entire interior surface of the intake manifold because of its configuration and therefore to fully reduce the air resistance for efficient air intake. Moreover, there is a limitation to the reduction of its weight. The EP-A-0 181 548 discloses a manifold consisting of a tube having a longitudinally protruding part. Apertures 32 having a fastening flange at their free end are provided in intervals along the protruding part. Although the title of the document refers to a manifold in general, it is clear from the description that the document is concerned with a manifold for heat exchangers only. This document, however, shows a manifold according to the preamble of claim 1. It is an object of the present invention is to overcome the above problems and to provide an intake manifold which is diminished in resistance to the flow of air therethrough and improved in air intake efficiency. Another object of the invention is to provide an intake manifold which is internally smooth-surfaced and needs not be smoothened for finishing. Still another object of the invention is to provide an intake manifold having a smaller weight than conventional cast intake manifolds. Further, an other object of the invention is to reduce the intake noise in producing a muffling effect in the manifold. To comply with these objects, the intake manifold according to the invention is characterized by the features of claim 1. The present invention will be described below in greater detail with reference to the accompanying drawings. Fig. 1 is a perspective view showing an intake manifold embodying the invention; Fig. 2 is a fragmentary plan view partly broken away and showing the manifold; Fig. 3 is a view in section taken along the line III-III in Fig. 2; Fig. 4 shows a process for preparing a main pipe stepwise; Fig. 5 shows another process for preparing the main pipe stepwise; Fig. 6 shows the main pipe and a branch pipe before they are joined together; Fig. 8 is a view showing another mode of connection between the main pipe and the branch pipe according to the invention, the view being in section along a plane containing the axes of the two pipes; Fig. 9 is a view similar to Fig. 8 and showing another embodiment of the invention; and With reference to Figs. 1 to 3 showing an intake manifold 10 embodying the invention, the manifold 10 comprises a main pipe 20 made of wrought aluminum material and having an open end, a closed end opposite to the open end, a plurality of holes 21 formed in its peripheral wall and outward tubular projections 22 integral with the peripheral wall and each formed around each of the holes 21, and a plurality of branch pipes 30 made of wrought material and each having one end fitting in and joined to each of the tubular projections 22. A throttle body 40 in the form of a cast aluminum member is fixedly joined to the open end of the main pipe 20. An air duct from an unillustrated air cleaner is connected to the throttle body 40. The other ends of the branch pipes 30 are collectively connected to a support flange 50, via which the branch pipes 30 communicate with the respetive cylinder heads of an unillustrated engine. The closed end of the main pipe 20 has an outwardly bulging semispherical closing wall 23 having a concave spherical inner surface, which produces a muffling effect. The tubular projection 22 is identical with the branch pipe 30 in inside diameter. An enlarged tubular portion 24 having an inside diameter larger than the outside diameter of the branch pipe 30 is formed at the forward end of each tubular projection 22 integrally therewith. The main pipe 20 is prepared from a wrought aluminum material, e.g., an extrusion pipe or an impact extrusion pipe. Fig. 4 (a) shows such an impact extrusion pipe 60 which is open at one end and closed at the other end. To prepare the main pipe 20 from this pipe 60, the closing wall 61 of the pipe 60 is pressed into the outwardly bulging semispherical closing wall 23 as seen in Fig. 4 (b). Next as seen in Fig. 4 (c), the peripheral wall of the pipe 60 is bulged at the portion thereof to be connected to each branch pipe 30 to form a tubular protrusion 62 having a forward end closed with a wall 63. A hole 65 is then formed in the end closing wall 63 of the protrusion 62 centrally thereof except at its peripheral edge portion as shown in Fig. 4 (d). Subsequently as seen in Fig. 4 (e), the remaining portion of the wall 63 defining the hole 65 is outwardly bent flush with the peripheral wall 64 by burring, whereby the protrusion 62 is made into the tubular projection 22, with the hole 21 formed in the peripheral wall of the main pipe. The enlarged tubular portion 24 is formed by diametrically enlarging the forward end of the projection 22 as seen in Fig. 4 (f). Finally, the enlarged tubular portion 24 is sized with a sizing tool to give accurately circular cross-sectional inner and outer two contours to the portion 24. Alternatively, the main pipe 20 is prepared from a pipe 60 by the following process. After the closing wall 61 of the pipe 60 has been pressed into a semispherical form in the same manner as above, a hole 66 smaller than the hole 21 is formed in the peripheral wall of the pipe 60 at the portion thereof to be connected to each branch pipe 30 as seen in Fig. 5 (a). Next, the portion around the hole 66 is outwardly bent by burring to form the tubular outward projection 22 and the hole 21 as shown in Fig. 5 (b). The enlarged tubular portion 24 is thereafter formed in the same manner as above, and the portion 24 is finally sized. When the main pipe 20 is to be prepared from an extruded aluminum pipe, one of the open ends of the extruded pipe is closed, and the same steps as above are thereafter performed. Each branch pipe 30 is connected at its one end to the main pipe 20 by fitting the end into the enlarged tubular portion 24 at the outer end of the projection 22 in alignment therewith, and bonding the pipe end to the tubular portion 24 by brazing. The branch pipe 30 is formed on the outer peripheral surface of the above-mentioned one end with protuberances 31 which are equal in projection height, in contact with the inner peripheral surface of the tubular portion 24 and arranged at a given spacing circumferentially thereof. The branch pipe 30 is aligned with the tubular projection 22 by these protuberances 31, which also form between the inner peripheral surface of the enlarged tubular portion 24 and the outer peripheral surface of the branch pipe 30 a clearance 32 filled with a brazing material 70. The branch pipe 30 is prepared from a wrought aluminum material, e.g., an extruded pipe, by bending the extruded pipe to the shape of a hairpin, sizing the opposite ends with a sizing tool to give accurately circular inner and outer two contours to each end in cross section, and thereafter forming the protuberances 31 by dimpling on the peripheral wall of the end to be connected to the main pipe 20. Preferably, the main pipe 20 and the branch pipes 30 are made of an aluminum material of AA6000 series, such as AA6063 or AA6061, which comprises 0.35 to 1.5 wt. % Mg, 0.20 to 1.2 wt. % Si, and the balance aluminum and inevitable impurities, because if the Mg content is less than the above lower limit, insufficient strength will result, whereas when the content is over the upper limit, the material is likely to be inferior in extrudability, workability and amenability to brazing. Further if the Si content is less than the lower limit, insufficient strength is likely to result, whereas if it is above the upper limit, the material is liable to exhibit poor extrudability and lower workability. While the aluminum materials for use in preparing wrought materials include, besides those of AA6000 series, aluminum materials of AA1000 series, AA2000 series, AA3000 series, AA5000 series and AA7000 series, the materials other than those of AA6000 series have the following drawbacks. Aluminum materials of AA2000 series are low in corrosion resistance and workabilities such as hot extrudability, forgeability and bendability. Those of AA5000 series have good corrosion resistance but are low in hot extrudability, forgeability, bendability and like workabilities and poor in amenability to brazing. Those of AA7000 series are low in resistance to stress corrosion cracking and workabilities such as hot extrudability, forgeability and bendability. Further aluminum materials of AA1000 series and AA3000 series are inferior to those of AA6000 series in mechanical strength after brazing. Examples of such materials are compared in the following table in respect of properties. Property Kind of material AA6063 AA3003 AA1100 Hot extrudability E E E Workability E E E Amenability to brazing G E E Mechanical strength E P VP Forgeability E E E Internal surface smoothness after shaping E E E In the above table, the term "workability" refers to amenability to bulging, burring and bending. The symbols listed stand for the following: E for excellent, G for good, P for poor and VP for very poor. More specifically stated with respect to "mechanical strength" which means the tensile strength of brazed joints, P stands for a tensile strength of 80 and VP for a tensile strength of 60 when the tensile strength represented by E is 100. With reference to Fig. 8 showing another embodiment of the invention, the tubular projection 22 of the main pipe 20 is formed at its forward end with two enlarged tubular portions 80 and 81 which differ in inside diameter, unlike the single tubular portion 24 of the first embodiment. The first enlarged tubular portion 80, which is integral with the projection 22, is adapted for receiving the end of the branch pipe 30 and has an inside diameter approximately equal to the outside diameter of the branch pipe 30. The second enlarged tubular portion 81, which is integral with the first portion 80, is adapted to retain a brazing material 80 therein and has a larger inside diameter than the first portion 80. The present embodiment further differs from the first embodiment in that the end of the branch pipe 30 to be joined to the main pipe 20 is provided with none of the protuberances 31 on its outer periphery. The branch pipe 30 is brazed to the main pipe 20 by fitting the branch pipe end into the first enlarged tubular portion 80 in alignment therewith, placing the brazing material 82 into the second enlarged tubular portion 81 and heating the assembly. With reference to Fig. 9 showing another embodiment of the invention, the tubular projection 22 of the main pipe 20 is integral with a first enlarged tubular portion 83 having an inside diameter which is equal to the outside diameter of the branch pipe 30 plus twice the projection height of the protuberance 31. Integral with the first portion 83 is a second enlarged tubular portion 84 having a larger inside diameter than the first portion 83. The brazing material applied is accommodated inside the second portion 84 and also in the clearance between the inner periphery of the first portion 83 and the outer periphery of the branch pipe 30 except where the protuberances 31 are present. In this embodiment, the branch pipe 30 is brazed to the main pipe 20 in the same manner as in the embodiment of Fig. 8.

Claims: An intake manifold for engines of automobiles, having a plenum chamber (20) being closed at one end and open at the other end and made of wrought aluminum material and a plurality of branch pipes (30), said plenum chamber (20) and branch pipes (30) being separately made, said plenum chamber (20) having a plurality of holes (21) and outward tubular projections (22) provided integrally with and formed out of the material of the peripheral wall and each formed around each of the holes, enlarged tubular portions (24) having an inside diameter larger than the outside diameter of the branch pipes (30) being formed at the forward end of each of the tubular projections (22), characterized in that the inner diameters of the branch pipes (30) and the tubular projections (22) are identical, the branch pipes (30) being made of wrought aluminum and having one end fitting in and joined to each of the enlarged tubular portions (24) of the tubular projections (22), the closed end of the plenum chamber (20) having a concave spherical inner surface. An intake manifold as claimed in claim 1, characterized in that the branch pipes (30) are made of an aluminum material of AA6000 series.

Inventors: AKIYOSHI YASUSHI C O SHOWA ALU, HIRUNUMA NAOHISA C O SHOWA ALU, KANEKO TOYOJI C O SHOWA ALUMIN, NOGAMI TOYOICHIRO C O SHOWA AL, SUKIMOTO MINOBU C O SHOWA ALUM, TAGUCHI SEIJIRO C O SHOWA ALUM, USUI TADASHI C O SHOWA ALUMINU, YAMAZAKI KATSUMI C O SHOWA ALU, AKIYOSHI, YASUSHI, C/O SHOWA ALUMINUM CORPORATION, HIRUNUMA, NAOHISA, C/O SHOWA ALUMINUM CORPORATION, KANEKO, TOYOJI, C/O SHOWA ALUMINUM CORPORATION, NOGAMI, TOYOICHIRO, C/O SHOWA ALUMINUM CORPORATION, SUKIMOTO, MINOBU, C/O SHOWA ALUMINUM CORPORATION, TAGUCHI, SEIJIRO, C/O SHOWA ALUMINUM CORPORATION, USUI, TADASHI, C/O SHOWA ALUMINUM CORPORATION, YAMAZAKI, KATSUMI, C/O SHOWA ALUMINUM CORPORATION
Applicants: SHOWA ALUMINUM CORP, SHOWA ALUMINUM CORPORATION
Application year: 1991
Main classification: F02M35
IPC codes: F02M35, F02B75, F02B1