Patent Application
20050155570
The present invention relates to internal combustion engines; more particularly, to devices for inducing flow tumble in intake manifold runners for internal combustion engines; and most particularly, to a tumble control rotary valve having a pivot at a lower edge.
Multiple cylinder internal combustion engines are well known. Such an engine typically includes an intake air manifold for collecting combustion air through a common intake valve into a plenum and distributing the air to each of the individual combustion cylinders via air channels known in the art as “runners.” Intake manifolds are intended to optimize the flow of air into the cylinders through appropriate plenum volume and shape, runner lengths and cross-sectional shapes, and overall manifold layout and geometry. Typically, a manifold has a fixed geometry that is optimized for a certain range of engine speeds and thus represents a compromise for other conditions. So-called active tuned manifolds employ valves or other active elements to overcome or reduce such compromises by dynamically changing the manifold geometry to be more closely optimized for each operating condition.
One known type of active tuning involves dynamically changing the geometry in one or more of the manifold runners to induce added turbulence into air flowing through the runners at a point just ahead of the intake valves. Such turbulence is known in the art as “tumble.” Added tumble improves the in-cylinder mixing of air and fuel and thus promotes more efficient combustion.
In the prior art, tumble is typically induced by placing a movable valve, such as a rotary valve having a “butterfly” damper, in the runner and rotating the valve to partially block the air passage in the runner. Typically, the valve cross-shaft is asymmetrically disposed on the butterfly damper such that when the valve is forced closed the bottom section of the runner is blocked, forcing the air to flow up and over the upper part of the valve. The air, after being biased to the top of the runner, enters the cylinder in a manor that causes the charge to tumble around an axis perpendicular to the centerline of the engine cylinder. In a typical prior art multi-cylinder engine, each of the runners includes a tumble valve, and several individual valves share a common pivotable cross-shaft that runs through the centers of the runners. Pivoting this shaft allows the valves to be rotated together from an open position, wherein the butterflies are aligned with the direction of air flow, to a closed position, wherein the butterflies are perpendicular to the flow direction. Typically, each butterfly damper is shaped such that, in fully closed position, the damper does not fully occlude the runner. The top section of the runner remains open to flow while the middle and bottom sections are closed to flow.
Although a prior art tumble valve can induce tumble in the closed position, a shortcoming of such a valve is that it creates an unwanted air flow restriction when in the open position. Such a flow restriction reduces engine efficiency and power. Flow losses in prior art engines may be as high as 15% of the possible total air flow at wide open engine throttle.
What is needed in the art is a runner tumble valve that can provide required degrees of air tumble when desired and can also cause little or no tumble or air flow restriction when no tumble is required.
It is a principal object of the present invention to improve the fuel efficiency and power of an internal combustion engine.
Briefly described, a tumble valve in accordance with the invention for variably impeding air flow in a manifold runner includes a pivot-shaft located at, or recessed into, a wall of the runner. Preferably, the cross-sectional shape of the runner in the region of the pivot-shaft is generally rectangular or rectanguloid. A similarly rectangular or rectanguloid butterfly damper is attached along one edge thereof to the pivot-shaft.
This shaft location allows the valve to be closed to a position that creates a desired degree of tumble in air flowing through the runner, but also allows the shaft and damper to be recessed to or into the runner wall when in the open position. Recessing the valve thusly eliminates any parasitic flow restriction when the valve is open, as the shaft and damper are not in the flow path. A valve in accordance with the invention is a further improvement over the prior art in that, in any partially-closed position, the lower area of the runner is always blocked because the valve pivots from below. All air is forced up and over the upper edge of the damper, thus increasing tumble over that obtainable with a prior art valve at any non-zero damper angle to the air flow direction. This permits fuel optimization over an increased range of engine speeds.
The present invention will now be described, by way of example, with reference to the accompanying drawings, in which:
Referring to
As already mentioned above, a shortcoming of a prior art tumble valve such as valve 22 is that even when wide open, as shown in
Referring to
Preferably, the cross-sectional shape of valve sub-assembly 40 is generally rectangular, as is the plan shape of damper 26′, to permit the damper to lie flat against, or within a recess in, wall 44.
A distinguishing feature of a tumble valve in accordance with the invention is that the shaft is disposed in the sidewalls of the runner or sub-assembly such that no air flow is permitted between the shaft and wall 44 at any position of the damper 26′. Thus damper 26′ has no counterpart to prior art butterfly portion 27b, and all the air passing through the runner passes between shaft 24′ and wall 42. The degree of tumble provided by valve 22′ may be continuously varied by varying the open angle of the valve between about 0° (fully open,
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.
