The present invention relates to molded polymer intake manifolds for internal combustion engines; more particularly, to a multiple-part injection molded intake manifold; and most particularly, to a three-piece injection molded intake manifold wherein the walls of a seal groove are parallel to each other and are perpendicular to a mating engine head surface, and wherein the parts may be formed and die drafted without the use of auxiliary slides.
Intake manifolds formed by injection molding of polymers are well known in the engine arts. A manifold assembly typically comprises an upper manifold, containing the air entry and control apparatus and an air plenum, and a lower manifold, containing individual runners for supplying air distributed from the upper manifold to the individual intake valve ports in the engine head. The upper and lower manifolds typically are formed separately and are joined as by vibration welding prior to being assembled to an engine. A lower manifold typically is further manufactured by injection molding of a top shell and a bottom shell which are subsequently joined as by vibration welding.
In forming a lower manifold for a V-style engine, a serious manufacturing problem is encountered, which problem is solved by the present invention. In the prior art, the bottom shell is formed as a single unit having a die draft direction that must be along the vertical axis of the shell in order for the mold to exit both left and right banks of the runners. Such a lower manifold is said to be of “two-piece” construction (upper and lower shells). The required die draft direction and split core mold construction restricts the individual runners to substantially rectangular cross-sections which shape is sub-optimal for air delivery and fuel/air mixing.
Further, in order to avoid the use of auxiliary molding slides, which can result in significant increases in cost, molding cycle time, and risk in a productive environment, the seal groove in the manifold face that mates with an engine head must be formed with divergent walls to permit removal of the part from the mold. This groove geometry is not optimal because a ring seal is not reliably retained in the groove during engine assembly without resort to adhesives or mechanical retention devices. Optimally, the groove walls are parallel to each other and perpendicular to the mating faces of the manifold and the engine head to spontaneously retain a seal ring during engine assembly, but such grooves cannot be formed by die drafting along the shell axis without use of an auxiliary molding slide.
What is needed in the art is a method and apparatus of forming a lower shell for a V-style intake manifold wherein the seal groove walls are parallel to each other and perpendicular to the mating faces of the manifold and the engine head without use of an auxiliary molding slide.
It is a principal object of the present invention to provide a lower shell for a V-style intake manifold wherein the seal groove walls are parallel to each other and perpendicular to the mating faces of the manifold and the engine head.
Briefly described, a lower manifold for a V-style internal combustion engine comprises at least three shells: a top shell for mating with an upper manifold; a left shell for mating with a left engine head; and a right shell for mating with a right engine head. Prior art lower manifolds are formed in two pieces comprising a top shell and a bottom shell. In the present invention, the three shells are formed independently by injection molding and are joined as by vibration welding when aligned in a welding jig. The molds for the left and right shells are formed such that the seal ring groove has a rectangular cross-section having sidewalls perpendicular to the lower shell surface because each left and right shell has its own draft angle perpendicular to its lower shell surface. The method and apparatus of the invention permits runner cross-sections to be significantly rounded, which improves air flow characteristics of the runners.
The present invention will now be described, by way of example, with reference to the accompanying drawings, in which:
Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate preferred embodiments of the invention, and such exemplifications are not to be construed as limiting the scope of the invention in any manner.
An improved apparatus and method in accordance with the invention for forming an injection-molded lower intake manifold can be better appreciated by first considering a prior art apparatus and method.
Referring to
A groove 36 is formed in shell mating surface 38 for retaining a seal ring (not shown) to form a gasket around each runner 11a,11b between manifold portion 22a,22b and engine head 24a,24b. As noted above, an unwanted consequence of having to draw the one-piece lower mold in direction 28 is that groove wall 40 must be formed parallel to direction 28. As seen specifically in circle 1, because the opposing groove wall 42 is formed preferably orthogonal to surface 44 of head 24a, the resulting groove 36 has undesirably non-parallel, divergent walls in the longitudinal direction of lower manifold 10 (although the groove walls obviously may be mutually parallel and orthogonal to the surface 44 in the manifold-transverse direction).
Referring now to
As seen specifically in circle 2, drafting in centerline direction 128a,128b permits a seal groove 136 having desirably parallel walls 140,142 which also are parallel to direction 128a,128b. However, undesirably, the walls are not perpendicular to either shell surface 138 or head surface 44. Further, forming the portion shown in circle 2 undesirably requires use of an additional slide (not shown) in molding because a fixed mold portion forming surface 150 cannot be drawn past the enlarged shell portion 152 shown in circle 2.
Referring to
As seen specifically in circle 3, drafting in direction 228a,228b permits a seal groove 236 having desirably parallel walls 240,242 parallel to direction 228a,228b. Further, the walls are perpendicular to both of shell surface 238a and head surface 44a. Further, forming the portion shown in circle 3 does not require an additional slide in molding because a fixed mold portion forming surface 250 can be drawn past the enlarged portion 252 having a surface 254 parallel to direction 228a.
While the invention has been described by reference to various specific embodiments, it should be understood that numerous changes may be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the described embodiments, but will have full scope defined by the language of the following claims.