Swirl Generating Arrangement for an Internal Combustion Engine

1. Field of the Invention

The present invention relates generally to an internal combustion engine and more particularly to a swirl generating arrangement for an internal combustion engine which enables the controllable generation of swirl about the combustion chamber which will persist even to the end of the compression stroke.

2. Description of the Prior Art

In a known arrangement a vane has been disposed in the induction passage and arranged to be essentially parallel to the cylinder axis. This vane is movable to vary the cross sectional area of the induction passage and accordingly increase the velocity of the incoming charge under given operating conditions and direct the charge into the combustion chamber so as to swirl about the axis of the cylinder. However, this arrangement has suffered from the drawback that the variable opening through which the charge flows is substantially rectangular and oriented with the longitudinal axis thereof essentially parallel with the cylinder axis. This accordingly introduces the charge into the combustion chamber with a relatively weak flow component in the plane normal to the cylinder axis. This has lead to the formation of a swirl within the combustion chamber which all but disappears as the piston approaches TDC during the compression stroke, at which time the swirl has the most value in promoting efficient combustion.

The present invention features an essentially rectangular swirl generating vane which is disposed in a rectangular cross-sectional portion of the induction passage in a manner to accelerate the charge and cause it to assume a jet stream which has a flow component maximized in the plane perpendicular to the cylinder axis. The induction passage is oriented with respect to the cylinder to introduce the jet stream into the combustion chamber tangentially with respect to the cylinder wall and accordingly produce a strong swirl which will persist even when the piston approaches TDC during the compression stroke. The vane is curved at the trailing end to promote laminar flow therepast and operatively connected to a control device which preferably takes the form of the engine throttle valve so that the vane can be moved in accordance with the induction of the engine and maintain the maximum velocity of the jet stream without any reduction in charging efficiency.

Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.

The features and advantages of the present invention will become more clearly appreciated from the following description taken in conjunction with the accompanying drawings in which like reference numerals denote corresponding elements, and in which

FIG. 1 is a sectional view showing a first embodiment of the present invention;

FIG. 2 is a view as seen in the direction of arrow A shown in FIG. 1;

FIGS. 3, 4, and 5 are schematic plan views showing possible induction port arrangements which can be used in conjunction with the swirl generating arrangement of the present invention;

FIG. 6 is a sectional view showing a second embodiment of the present invention; and

FIG. 7 is a schematic plan view showing a third embodiment wherein the swirl generating arrangement of the present invention is combined with a fuel injector.

Turning now to the drawings and more specifically to FIGS. 1 and 2 a first embodiment of the present invention is shown. In FIG. 1 the numeral 10 denotes an internal combustion engine having a cylinder 12 formed therein and a cylinder head 14 disposed so as to close one end of the cylinder. A piston 16 is reciprocatively disposed in said cylinder to define a variable volume combustion chamber 18. Leading from the combustion chamber to the ambient atmosphere is an induction passage 20. An intake valve 22 is disposed in a well known manner to control the communication between the combustion chamber 18 and the induction passage. A spark plug 24 or the like is disposed through the cylinder head 14 for the purposes of igniting the combustible mixture compressed in the combustion chamber during the compression stroke. A swirl generating vane 26 pivotally mounted on a shaft 30 is disposed in the induction passage 20 for the purposes of deflecting the incoming charge and directing same into the combustion chamber 18 with a strong swirl component in the plane normal to the cylinder axis 28. As best shown in FIG. 2 the vane is essentially rectangular and is disposed in a portion of the induction passage having a rectangular cross section having a width approximately the same as the vane to reduce the amount of charge which can flow past the lateral edges of said vane. In this embodiment the shaft 30 is disposed in a branch 32 of an induction manifold 34 so that the vane extends from the shaft to terminate in the induction port passage 36 formed in the cylinder head 14. As shown in FIG. 1 the vane 26 is arranged to approach the combustion chamber as closely as practical so that at the maximum deflection the trailing edge 37 thereof closely juxtaposes the intake valve guide sleeve 38. The trailing edge 37 is as shown in FIG. 1, smoothly curved to induce substantially laminar flow therepast and in the minimum deflection position defines a variable cross section elongate rectangular window as best seen in FIG. 2 the longest dimension of which extends in the direction a.

A linkage system 40 for controlling the angular displacement of the vane is provided and which takes the form of a lever 42 and a suitable shaft or cable 43, interconnects the rotatable shaft 30 and vane 26 with a suitable control device which in this case preferably takes the form of the throttle valve 44 of a carburetor 46. However, the device is not limited to the throttle valve and/or accelerator pedal and may take the form of any suitable control arrangement.

In operation when the engine is idling or operating at light load with the throttle valve 44 almost closed the interconnection between same and the vane 26 causes the vane to assume a position similar to that illustrated in FIG. 1. Accordingly as the air and/or air-fuel charge flows through the induction passage 20 it is deflected and accelerated by the vane. The flow after having passed the vane assumes a jet stream having a substantially rectangular cross section. This jet stream then flows through the clearance between the bevelled head 48 of the intake valve 22 and the valve seat 50 into the combustion chamber 18. As illustrated in FIG. 1 the center line C of the induction passage is arranged to be as close to parallel with the plane normal to the cylinder axis so as to transfer the charge toward the combustin chamber substantially horizontally as long as possible. Further as shown in FIG. 3 the induction passage is also arranged to introduce the charge into the combustion chamber tangentially with respect to the cylinder wall which, in combination with the horizontal nature of the induction passage with respect to the cylinder axis wherein the extrapolation of the bottom thereof passes between the bevelled intake valve head and the valve seat (when the intake valve is open) and the flow vane producing a jet stream with a rectangular cross section as previously described, causes the charge to be introduced into the combustion chamber to swirl therein with a strong horizontal (with respect to the "vertical" cylinder axis) flow component. Due to this strong horizontal flow component the swirl will persist even though the piston rises to approach its TDC position.

FIGS. 4 and 5 show alternate arrangements for introducing the charge into the combustion chamber tangentially with respect to the cylinder wall.

As the demand on the engine increases and the throttle valve is opened, the vane 26 is accordingly moved to increase the cross sectional area through which the charge can flow. However, as the increased opening of the throttle valve allows a greater volume of air to flow through the induction passage the effect of the swirl vane is maintained and without any unwanted flow restriction which would result in a loss in charging efficiency. Hence, under all operating conditions the optimal flow velocity past the vane is maintained.

FIG. 6 shows a second embodiment of the present invention. In this embodiment the shaft 30 is mounted to the cylinder head 14. With this arrangement accurate setting of the minimum cross sectional area of the rectangular window is facilitated as different from the first embodiment wherein the vane is mounted to the induction manifold and arranged to extend into the induction port passage. However, with the second embodiment the linkage between the control device (throttle valve) and the lever 42 must be disconnected upon disassembly of the engine as compared with the arrangement of the first embodiment.

The trailing edge of the vane in the second embodiment is curved to terminate in a flat portion, the extrapolation which extends slowly towards and intersects with an extrapolation of the bottom of the induction port passage which also extends between the bevelled head 48 of the intake valve and the valve seat 50 (when the intake valve is open) to accordingly induce smooth flow therepast and direct the rectangular cross-sectional flow between the bevelled head of the intake valve and the valve seat into the combustion chamber. This in combination with the arrangement of the induction passages with respect to the cylinder (see FIGS. 3 to 5) introduces the charge into the combustion chamber tangentially with respect to the cylinder wall and with a strong horizontal flow component which sets up a strong swirl which will persist even to the end of the compression stroke.

The operation of the second embodiment is the same as the first and as such requires no description.

FIG. 7 shows a third embodiment of the present invention. In this embodiment, the engine is fuel injected and equipped with a fuel injector 54 disposed to inject fuel toward the head of the intake valve 22 and accordingly into the rectangular cross-sectioned jet stream. This arrangement promotes intimate mixing of the air and the injected fuel which is subsequently swirled about the axis of the cylinder. Stable operation of the engine especially during the start up mode is promoted by this arrangement. In this figure the numeral 56 denotes an exhaust port passage.

Further in all of the embodiments described hereinbefore, the trailing edge of the vane can be formed with a curvature or curvatures which promote laminar flow therepast and minimize any eddy currents which would reduce the velocity and the effectiveness of the jet stream. The curvature(s) of course must be designed with the intended purpose of the engine in mind and the dimensions of the particular induction passage.

Further, with the present invention due to the presence of a strong swirl within the combustion chamber at the time of ignition of the charge therein, the flame propagation speed is increased, extending the lean burn limit of the engine and/or increasing the amount of exhaust gas recirculation thus enabling a reduction in the NOx, CO and HC emissions. The strong swirl in all cases promotes stable combustion at engine start up due to the particularly strong horizontal flow component which is not possible with the prior art.

Thus in summary, the present invention features a device which provides a variable cross section opening upstream of the combustion chamber which opening produces a jet stream having a strong flow component in a plane normal or perpendicular to the cylinder axis. This in combination with the itroduction of the stream into the cylinder tangentially with respect to the wall of the cylinder produces a strong swirl which persists up until the end of the compression stroke. Further, the cross sectional area of the opening is varied in accordance with the induction demands of the engine to maintain the maximum possible velocity of the stream without incurring any charging efficiency losses. The strong swirl accordingly established allows the extension of the lean burn limit and/or the increase in EGR (exhaust gas recirculation) tolerance.

The foregoing description of the preferred embodiments of the invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and its practical application to thereby enable others skilled in the art to best utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto.