Metal working – Method of mechanical manufacture – Prime mover or fluid pump making
Reexamination Certificate
1999-08-06
2001-01-30
Cuda, I. (Department: 3726)
Metal working
Method of mechanical manufacture
Prime mover or fluid pump making
C029S890124, C029S890127, C164S113000
Reexamination Certificate
active
06178632
ABSTRACT:
FIELD OF THE INVENTION
This application is an application for patent which relates to air intake systems for internal combustion engines, particularly internal combustion engines for automobiles. More particularly, it relates to intake manifolds and air assist rails and methods for making the same.
BACKGROUND OF THE INVENTION
Fuel injectors are often designed to use air under pressure to assist the atomization of fuel by the injectors. Since each injector in an engine requires air assist, each injector is connected to a supply of pressurized air.
Traditionally, since the injectors are in predetermined positions with respect to each other, the air is supplied to a bank of injectors by an external pod or rail. This pod is rigid and is attached to a row of injectors along a single bank. Thus, for in-line engines, there would be a single pod that extends the length of the engine connecting to all the cylinders. For engines with two banks of cylinders, such as “V”-type engines or horizontally opposed pancake engines, two pods are provided where each pod is connected to the injectors for a single bank of cylinders. In another arrangement, the air assist passageway is not provided by an external pod, but is formed as a passageway internal to the intake manifold.
While the external pod requires additional piping and connections for each of the injectors, it also permits a passageway with optimum air pressure and air distribution. It also permits the intake manifold and cylinder head geometry to be kept simple.
Air assist passageways formed internal to the manifold are significantly constrained in their design. For example, they are either molded using pins, or are formed by gun-drilling the manifold after it is molded. As a result, the air assist passageways typically have a circular cross section with a relatively constant cross sectional area, and a straight longitudinal axis. Their diameter is typically limited to fit between and around the injector pockets and the air induction ports for each cylinder. The longitudinal axes of the air assist passageways formed in the manifold are typically offset to one side of the fuel injector pockets such that they intersect the air injector pockets on one side.
These constraints cause several problems. First, there are significant air assist pressure drops from injector to injector as the assist air travels the length of the air assist passageway. Second, when the injectors operate, they generate pressure pulses that travel down the air assist passageways. Depending upon the geometry of the air assist passageways, these pressure pulses may cause injectors to be starved for assist air, or alternatively have too much assist air applied to the injectors. This is commonly called “cross-talk” between injectors and negatively affects the atomization of the fuel. In addition, fuel from an upstream injector can be introduced into the air assist passageways and can be transmitted to neighboring air injectors. Third, the drilling process for forming air assist passageways leaves metal or plastic particles as well as thin flanges of metal where the air assist passageways intersect the injector pockets that can break off during operation and damage the engine. Finally, in the process of molding offset air assist passageways, the pins forming the air assist passageways can be easily deflected away from injector pocket bosses. This leaves a gap between the pins and the bosses that can be filled with the molded material thus blocking the flow of air from the air assist passageway to the fuel injector pocket.
The problems are compounded by supplying assist air to an end of the internal air assist passageway. Typically, a connection is provided on one end of the air assist passageway into which the assist air is supplied. Thus, for example, the air assist passageways on a V-8 engine (having two banks of four cylinders) would be fed from an air line connected to an end of the air assist passageway. To reach the fuel injector at the far end of the engine, the passageway would have to pass three fuel injectors, all of them introducing pressure pulsations into the system that would affect the end cylinder. In a straight six-cylinder engine, the air assist passageway would pass five fuel injectors before reaching the last fuel injector in the bank of cylinders. Five fuel injectors introduce their pressure pulsations into the air assist passageway that would affect that last fuel injector.
What is needed therefore is an improved method and apparatus for supplying assist air to an engine having a plurality of fuel injectors. It is an object of this invention to provide such an apparatus and method.
SUMMARY OF THE PRESENT INVENTION
In accordance with a first embodiment of the invention, a method of manufacturing air assist passageways and injector pockets is provided including the steps of providing first and second closeable and openable mold portions configured to define an outer surface of an air assist passageway and injector pockets, wherein the air assist passageway extends between and couples the injector pockets and further wherein the second mold portion has a plurality of inwardly extending bosses defining an inner surface of each of the plurality of injector pockets, closing the first and second mold portions to define a mold cavity that defines the outer surface of the air assist passageway and injector pockets, inserting at least one air assist passageway pin through apertures in the injector pockets to define an interior surface of the air assist passageway that extends through and couples the injector pockets, filling the mold cavity with molten material, solidifying the molten material to form a solid part having the air assist passageway and injector pockets, withdrawing the at least one air assist passageway pin from the solid part, and opening the mold. The method may include the steps of inserting at least one additional air assist passageway pin through at least one aperture in another of the injector pockets, and withdrawing the at least one additional air assist passageway pin from the solid part. The method may further include the step of engaging an end of the at least one air assist passageway pin with an end of the at least one additional air assist passageway pin to form an elongate tubular body therefrom. The method may further include the step of plugging an open end of an air assist passageway in the solid part, or plugging a second open end of the air assist passageway in the solid art. The step of inserting may include the step of inserting the at least one air assist passageway pin through apertures in the injector pocket bosses such that at least a length of the pin is completely surrounded by the injector pocket bosses. The step of inserting may also include the step of inserting the at least one air assist passageway pin through a longitudinal axis of the injector pocket bosses.
In accordance with the second embodiment of the invention, a method of manufacturing an intake manifold for a “V” style internal combustion engine having first and second banks of cylinders, the manifold including, for each bank of cylinders, a plurality of fuel injector pockets and an air assist passageway extending between the plurality of fuel injector pockets, the manifold also including a plurality of induction air passageways, each of the plurality of induction air passageways being associated with each of the plurality of fuel injector pockets, where the method includes the steps of providing first and second closeable and openable mold portions configured to define when closed an outer surface of the intake manifold including the outer surface of the fuel injector pockets, the induction air passageways, and the air assist passageways, wherein the second mold portion has a plurality of inwardly extending injector pocket bosses defining an inner surface of each of the plurality of fuel injector pockets, closing the first and second mold portions to create a mold cavity defining the outer surface of the manifold, inserting the first air assist passage
Nally Debora
Schwarzpech Karl Robert
Worrel Christine C.
Cuda I.
Siemens Canada Limited
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