GB2218734A - I.C. engine intake and exhaust manifolds - Google Patents

Abstract

A valve 26 controlling an opening between branches 12 and 14 of an intake manifold 10 to control pulse charging or between intake and exhaust manifolds to control exhaust recirculation is operated by a diaphragm 20 of a vacuum actuator 18 integrated into the manifold walls. <IMAGE>

Description

VARIABLE GEOMETRY MANIFOLDS The present invention relates to variable geometry manifolds and in particular to the valves used in such manifolds to connect branches of the manifolds under selected conditions.

There have been proposed various intake manifold systems for internal combustion engines in which branches of the manifold adjacent one another are interconnected by valves that may be opened and closed as a function of an operating parameter of the engine. In this way, the effective lengths of the branches may be altered at different speeds to achieve broad band tuning of the intake manifold. One such manifold is shown in PCT Application No. PCT/GB87/00417 but the invention may be applied to other designs.

According to the present invention, there is provided a variable geometry manifold system for an internal combustion engine wherein the manifold has branches which may communicate with an one another through a valve controlled by a vacuum motor, wherein the vacuum motor is contained within the manifold system.

In the prior art, the valve closure member disposed between the two manifold branches was connected to an external vacuum motor ny means of a spindle which passed through the wall of the manifold. Apart from creating sealing problems, it was sometimes not possible to accommodate the external vacuum motor in view of restricted availability of space in the vicinity of the manifold.

In the present invention, by virtue of the vacuum motor being contained within the manifold system, there is no requirement to seal against moving components and sealing presents no particular problem.

Furthermore, the packaging problems are obviated or at least mitigated in that the incorporation of the vacuum motor within the manifold system results in a more compact configuration.

As well as being used in an inlet manifold, the invention can also be applied to exhaust manifold and to the EGR valve which controls passage of gases from the exhaust to the inlet manifold.

The invention will now be described further, by way of example, with reference to the accompanying drawings, in which the single figure shows a section through a manifold system of the invention.

The drawing shows a manifold 10 having two adjacent passages 12 and 14 which can communicate with one another through an opening 16 in the wall between them.

Each of the passages 12 and 14 is connected by a respective pair of primary tubes to two of the engine cylinders and by a larger secondary tube to a plenum chamber common to all the cylinders (not shown). The section of the drawing is taken at the junctions of the primary and secondary tubes. If the passages 12 and 14 are isolated from one another, then for each cylinder the manifold has a resonance frequency determined by the combined lengths of the primary and secondary tubes, whereas if the passages 12 and 14 communicate through the opening 16, then only the columns of air in the primary tubes can resonate. Thus by controlling the opening 16, manifold tuning over different engine speeds can be achieved.

To control the opening 16, a vacuum motor 18 is fitted within the chamber 14. The motor 18 has an external connection 26 through which vacuum can be applied to a chamber 22. The pressure in the chamber 22 acts on a flexible diaphragm 20 which in turns acts on a closure member 26. A return spring 24 is also provided in the chamber 22 to close the urge the closure member into a closed position in the absence of an applied vacuum. In this way, by varying the pressure in the chamber 22, the closure member can be moved from its closed position, shown in full lines in the drawing, to an open position shown in dotted lines.

The vacuum motor 18 is contained within the manifold in that no moving parts need to pass through the walls of the manifold. In particular, the only seal required lies between the housing of the vacuum motor and the manifold wall and the moving parts consisting of the diaphragm 20, the closure member 26 and the spring 24 all lie within the manifold. As compared with the prior art proposal, in which the actuating rod for the closure member 26 passed through the manifold walls, the invention provides both a more reliable and a more compact construction.

The closure member need not form part of the vacuum motor and it is alternatively possible for the opening 16 to be closed by a butterfly valve actuated by a vacuum motor contained within the manifold.

Though the invention has been particularly described by reference to an inlet manifold having a particular configuration, it should be clear that invention can equally be applied to exhaust manifolds and to manifolds having a different layout. The invention can also be used in EGR valves which control exhaust gas recirculation by opening and closing an opening between the inlet and exhaust manifolds.

Claims (3)

1. A variable geometry manifold system for an internal combustion engine wherein the manifold has branches which may communicate with an one another through a valve controlled by a vacuum motor, wherein the vacuum motor is contained within the manifold system.

2. A manifold system as claimed in claim 1, wherein the vacuum motor controlled valve is an EGR valve disposed between the inlet and exhaust manifolds.

3. A variable geometry manifold system constructed, arranged and adapted to operate substantially as herein described with reference to and as illustrated in the accompanying drawing.