ENGINE WITH VARIABLE AREA INTAKE PASSAGES

Abstract: An internal combustion engine (10) is provided with an induction system having intake runners (33) of conical or equivalent configuration in which flow control cones (39) or elements are axially moved to vary the effective cross-sectional area of the runner passages and thereby control the flow velocity and inertia of the incoming charge to improve various operating parameters such as combustion and charging efficiency.

Description: Technical Field This invention relates to internal combustion engines and, more particularly, to variable area induction system passages to intermittently feed intake charges to individual engine cylinders for combustion as specified in the preamble of claim 1, for example as disclosed in FR-A-1,189,338. Background It is known in the art relating to internal combustion engines to provide one or more combustion chambers having inlet ports with openings for intermittently admitting to the chambers charges for combustion therein. In piston engines, the inlet ports commonly include inlet openings controlled by poppet valves and fed through inlet passages. These inlet passages may be defined as comprising the outer, lead-in portions of the cylinder intake ports and the connected runners of associated intake manifolds. In connection with these arrangements, it has been previously recognized that a manifold or induction system designed for free breathing and good high speed performance is generally deficient in providing high engine torque at low speeds or efficient engine operation at part throttle and idle. A known method for improving this condition is to increase the flow velocity and inertia of the incoming air or air-fuel charge. This is sometimes attempted by providing dual manifold runners for each engine intake port, one runner having a relatively large cross-section for free breathing at high speeds and loads and the other runner having a much smaller cross-section to increase the flow velocity and inertia of the charge delivered to the intake ports. Another proposed solution is to provide the manifold runners with flexible walls to allow variation of the cross-sections thereof under differing operating conditions. DE-A-36 26 681 discloses a variable area induction system of an internal combustion engine in which one or more cone-shaped movable valve members co-operate with localized converging portions of the induction system to control the quantities of air or air-fuel mixture being supplied to intake ports of the engine. It is thought that the increased inertia resulting from utilizing intake passages or runners of smaller cross-sectional area during operation with reduced mass flow of the intake charges can result in increased cylinder turbulence and thereby improve combustion efficiency. The higher inertia may also improve volumetric efficiency by overcoming the back flow of a fresh intake charge when the piston begins its compression stroke and the intake valve is still open, a result which occurs predominately at low engine speeds. Summary of the Invention An internal combustion engine according to the present invention is characterised by the features specified in the characterising portion of claim 1. The present invention provides an engine with variable area intake passages. These are so arranged as to take full advantage of the higher charge inertia developed in low cross-sectional area passages at low engine speeds and gas flow conditions whilst allowing substantial increases in the cross-sectional area for free breathing and high performance at high engine speeds and load conditions where induction charge flow rates are sufficiently high. The invention provides intake passages, including manifold runners and/or intake port sections, having surrounding wall portions with consistently converging inner surfaces. These include, for example, frusto-conical surfaces leading from the outer portions of the manifold to a point preferably close to the engine combustion chamber, or the associated intake valve if utilized. Flow control elements in the passages are also provided having outer surface portions which are generally parallel with and opposed to the converging inner surfaces of the intake passages. The elements are movable along the direction of fluid flow towards and away from the valve or port opening to vary the effective passage flow area and, thereby, the rate and inertia of fluid flow through the passages and into the intake port. Suitable means for actuating the flow control elements in unison so as to similarly control flow in the various intake passages are also provided. These and other features and advantages of the invention will be more fully understood from the following description of certain specific embodiments of the invention taken together with the accompanying drawings. Brief Drawing Description In the drawings: Figure l is an end view of an internal combustion engine according to the invention having portions broken away to illustrate the cross-sectional configuration of an induction system having variable area intake passages and fuel injection means; Figure 2 is a view similar to Figure l but showing an alternative embodiment of engine having an induction system fed by a unitized charge-forming device, such as a carburettor; Figure 3 is a cross-sectional view through one of the conical induction passages shown in Figure 2 showing circular cross-sections from the plane indicated by the line 3-3 of Figure 2; Figure 4 is a cross-sectional view similar to Figure 3 but showing an alternative embodiment of passage configuration wherein the cross-sections are oval or elliptical in shape; Figure 5 is a cross-sectional view similar to Figure 3 but showing an alternative embodiment wherein the induction passage cross-sections are rectangular and the passages form frustums of pyramids, and Figure 6 is a view similar to Figure 3 but showing an alternative embodiment wherein the passage cross-sections are rectangular and the passages are wedge-shaped. Detailed Description Referring now to the drawings in detail, numeral l0 generally indicates an internal combustion engine of the reciprocating piston type, although the present invention is not so limited. Engine l0 conventionally includes a cylinder block ll including a plurality of cylinders l2, only one of which is shown. The cylinders are closed at one end by a cylinder head l4 which is carried by the block. Pistons l5 are reciprocably carried within the cylinders and co-operate with the block and the cylinder head to define variable volume working and combustion chambers l6 at the cylinder end. The cylinder head l4 further includes exhaust and intake ports l7, l8 for each of the cylinders. The intake ports l8 include combustion chamber openings l9 which terminate in valve seats 20 on which are seatable the heads 22 of intake poppet valves 23. The valves 23 are carried in the cylinder head l4 and have stems 24 actuated in conventional manner through valve gear, not shown, to periodically admit intake charges to the associated combustion chambers. The intake ports l8 further include delivery chambers 26 that surround the valve stems upstream of the openings l9 and port passages 27 that extend from a mounting surface 28 on the cylinder head side wall to their connection with respective delivery chambers 26 near one side of the associated valve stems 24. The intake ports and valves form part of an engine cylinder charge induction system which further includes an intake manifold generally indicated by numeral 30. The manifold is, for convenience, made in two sections: a runner section 3l and a plenum and connector section 32. The runner section 3l is mounted on the cylinder head mounting surface 28 and extends outwardly therefrom to define a plurality of runners 33, one for each intake port. These runners, as shown in Figure l, preferably join with the port passages 27 to define frusto-conical inner wall surfaces 34 extending from the far ends of the runner section into the port passages, to positions as close as possible to the associated valve stems. The plenum and connector section 32 is mounted on the outer end of the runner section and includes an enlarged plenum 35 having an inlet 36 for connection with a filter or other source of clean air. The plenum connects through individual connecting legs 38 with the runners 33 of the runner section 3l so as to provide, in combination, a plenum-type manifold with runners or intake passages, the engine-connected portions of which are conical, converging in the direction of flow towards the engine. The lengths of the manifold passages from the plenum to the intake ports may be selected to provide tuning of the induction system for maximum power or efficiency. To provide variation, in accordance with the invention, of the cross-sectional areas of the intake passages over an extended length immediately upstream of the intake valves, each of the conical intake passages is provided with a flow control element in the form of a movable cone 39. Each of the cones has frusto-conical outer surfaces 40 which are positioned generally parallel with an opposing the conically-converging inner surfaces 34 of the induction system intake passages. The cones 39 are supported on rods 42 that are carried in guides 43 in the connector section of the manifold. The rods preferably include rack teeth 44 which engage associated pinion gears 46 that are actuated together on a common shaft 47 to move the positions of the control cones 39, in unison between inner and outer locations. Alternatively, other suitable means could be provided for mounting and moving the cones. In the inner location, shown in solid lines in Figure l, the effective cross-sectional flow areas of the intake passages are at a minimum. Further, the effective flow areas decrease from the large ends of the cones to their smaller ends, at the locations where the parallel tapered surfaces of the associated intake passages terminate, by reason of the decreasing diameters of the annular flow areas, which are, preferably, of constant radial thickness. When the cones are in their outer positions, as shown in dashed lines in Figure l, the cross-sectional flow areas of the passages are at a maximum so as to allow free breathing during high speed and/or load operation of the engine. In the embodiment of Figure l, fuel is provided to the intake charges through electronic fuel injectors 48 mounted in the cylinder head, or manifold if desired, and spraying through ducts 49 into their respective intake ports near the location of the valve stems and preferably directed at or near the valve heads. These multi-point fuel injectors may be connected and actuated in accordance with current fuel system technology. The embodiment of Figure 2 is fundamentally similar to that of Figure l, the engine 50 differing primarily in that the fuel injectors and ducts are omitted and the intake manifold 5l is modified. For simplicity, like numerals are used to identify like parts. The modified intake manifold 5l has a runner section 3l which is fundamentally the same as that of the Figure l embodiment, differing only as required to mount upon the cylinder head at a location closer to the valves, in view of the absence of injectors. Outward of the runner section 3l, a log section 52 replaces the plenum and connector section of Figure l. Log section 52 extends logitudinally, connecting with each of the runners 33 of the runner section 3l. In addition, the log section 52 includes a flange 54 on which is mounted a carburettor 55, or an alternate charge forming-device such as a throttle body injection unit. The log section 52 also carries the pinion gears 46 and the rack-toothed rods 42 of the cone-shaped control elements 39 as in the embodiment of Figure l. In operation of either of the embodiments, fluid entering the manifold from the plenum intake or the carburettor is delivered to each of the cone-shaped runners 33 upstream of the flow control cones 39. When the intake valve 23 of each cylinder is open, downward motion of the respective piston draws the charge of fluid through the respective manifold runner 33, passing through the variable conical annulus between the flow control cone 39 and the associated inner wall surfaces 34 of the manifold and/or the associated port passage 27. In high speed and load operation of the engine, the cones 39 are positioned in or near their dashed line positions, which maximizes the annular thickness and the resulting effective cross-sectional passage area, to allow free passage of all or air-fuel mixture through the manifold and port into the engine cylinder. However, when the engine is operated at reduced speed and/or load with a reduced air flow requirement, the flow of mixture through the manifold is maintained at a high speed, or accelerated, by moving the flow control cones 39 towards the position shown in solid lines in Figures l and 2, thus reducing the effective flow area and increasing the flow velocity and inertia of the mixture or fluid passing through the manifold and into the intake port. The flow control cones are designed so that, in their inner, low engine speed, positions, they extend beyond the end of the manifold and into the ports as close to the intake valves as possible. Accordingly, the acceleration of the mixture flow and the higher inertia obtained causes turbulence which preferably persists into the port and through the valve into the cylinder, providing improved operation at low speeds. During low and mid-speed engine operation, the increased turbulence is expected to result in improved charge mixing, increased combustion efficiency, reduced ignition delay, improved lean mixture operation and combustion stability, and increase combustion pressure rise. The increased charge inertia could also reduce exhaust backflow during valve overlap in low speed operation. The variable intake cross-sectional area may also be capable of providing variable tuning to meet different engine speed requirements. While the configuration of the manifold passages and, optionally, the intake port passages may be frusto-conical, as shown in Figures l and 2, it should be recognized that other configurations for the intake passages and the associated flow control element may be utilized. Thus, for example, while the conical portions of the manifold runners and ports as illustrated are shown as arranged along a straight axis for linear movement of the flow control element, it would also be possible to provide for curved passages and a similarly curved flow control element moved in an arcuate fashion. The opposed surface portions of the flow control elements and their corresponding passages would still be arranged generally parallel to one another with the opposed surfaces converging towards the engine so that variations in the passage flow areas would be similarly accomplished. In like manner, the conical configurations of the control elements 39 and manifold runners 33 are shown in Figure 3 to have circular cross sections. However, many other alternative cross-sectional configurations could be used. For example, in Figure 4, an alternative manifold 58 is illustrated having oval runners 59 and flow control elements 60 of oval cross-section. Similarly, in Figure 5, there is illustrated a manifold 62 having runners 63 and flow control elements 64 of square or rectangular cross-section wherein the opposing surfaces form frustums of pyramids. Another alternative configuration is shown in Figure 6 wherein a manifold 66 has runners 67 and flow control elements 68 of rectangular cross section. In this embodiment, side surfaces 70, 7l, as shown in Figure 6, of the runners and control elements are parallel to one another and only upper and lower surfaces 72, 74 of the runners and elements converge in the direction of flow toward the cylinder. Thus, the inner surfaces of the runners and flow elements are wedge-shaped. It is recognized that applications of manifold and intake port induction systems disclosed herein could be made to rotary engines, or other machines utilizing intake ports with or without poppet or other intake valves. The term internal combustion engine or other similar terms which may be used in the specification and claims should be considered to include all forms of engines and other equivalent devices in which variable area intake runner and induction systems may be appropriately applied.

Claims: An internal combustion engine (10) comprising a cylinder intake port (18) including a combustion chamber opening (19), and a variable area induction system connected to the intake port (18), said variable area induction system comprising an intake passage (33) connecting with said intake port (18), said intake passage (33) having wall portions with converging inner surfaces (34), and a flow control element (39) located in the passage (33) and having outer surfce portions (40) opposing said converging inner surfaces (34) of the wall portions of said passage (33), the element (39) being movable along the direction of fluid flow towards and away from the port (18) to vary the flow area, characterised in that said intake passage (33) has a length connected to said intake port (18) upstream of, but closely adjacent said combustion chamber opening (19); the inner surfaces (34) of the wall portions of the intake passage (33) consistently converge towards one another throughout said lenght of intake passage (33); said outer surface portions (40) of the flow control element (39) are maintained generally parallel to said converging inner surface (34) of the wall portions of said passage (33) throughout the movement of the flow control element (39) so as to define a flow area which constantly decreases in the direction of the flow between the element (39) and the intake passage (33); and the element (39) is movable along the direction of fluid flow to and away from a point in the intake port (18) which is near to the combustion chamber opening (19), so as to vary the flow area and thereby the velocity and inertia of fluid flow into the combustion chamber opening (19). An internal combustion engine according to claim 1, characterised in that said combustion chamber opening (19) is controlled by a poppet valve (23); and said intake passage (33) connects with the intake port (18) upstream of the valve (23), and closely adjacent a valve stem (24) of the valve (23). An internal combustion engine according to claim 1, characterised in that the opposing surfaces (34,40) of the passage (33) and the control element (39) have circular lateral cross-sections. An internal combustion engine according to claim 3, characterised in that the opposing surfaces (34,40) of the passage (33) and the control element (39) are frusto-conical in shape. An internal combustion engine according to claim 1, characterised in that the opposing surfaces of the passage (59) and the control element (60) have oval lateral cross-sections. An internal combustion engine according to claim 1, characterised in that the opposing surfaces of the passage (63;67) and the control element (64;68) have rectangular lateral cross-sections. An internal combustion engine according to claim 6, characterised in that the opposing surfaces of the passage (63) and the control element (64) define frustums of a pyramid. An internal combustion engine according to claim 6, characterised in that the opposing surfaces of the passage (67) and the control element (68) are wedge-shaped. An internal combustion engine according to any one of the preceding claims, characterised in that said variable area induction system includes means (42,43,44,46,47) for moving the control element (39) to control the fluid flow.

Inventors: LEE, JORDAN R., MACFARLANE, GLEN R., SMITH, ROSS R.
Applicants: GENERAL MOTORS CORPORATION
Application year: 1989
Main classification: F02B27
IPC codes: F02D9, F02B27