INTERNAL COMBUSTION ENGINE WITH CYLINDER INTAKE PORT

Abstract: A cylinder intake port (32) in an internal combustion engine (l0) which provides a combination of high swirl and flow efficiency. The port (32) features roof ramps (62,63) of differing angles leading on opposite sides of a valve axis (50) into a swirl chamber (66) with a shelf portion (64) above a port throat (39). The flow path below the ramp (62) of lower angle is generally tangential with an outer portion of the cylinder (l2) and yields a positive swirl component, whilst the flow areas on the opposite sides of a valve stem (49) remain relatively unrestricted.

Description: Technical Field This invention relates to internal combustion engines and more particularly to cylinder intake ports for such engines. In particular the invention relates to intake ports in cylinder heads configured to impart swirl to intake charges directed into associated engine combustion chambers and to port configurations for obtaining high flow efficiency combined with swirl. An "intake charge" is the quantity of fuel/air mixture drawn into an engine cylinder during an intake stroke of a piston in that cylinder. Background Many configurations of engine cylinder intake ports, or cylinder head inlet ports, have been designed and/or utilized to create rotation or swirl of intake charges supplied to the combustion chamber or cylinder. In general however, intake port, or passage, configurations which have been effective in creating significant charge swirl have also resulted in reducing the mass of charge flowing into each cylinder on an intake stroke of a piston in that cylinder so as to result in what is called "reduced volumetric effeciency". This implies a reduction in the charge volume when calculated at standard temperature and pressure. In view of a renewed interest among engine designers in recent years in utilizing increasing amounts of charge swirl in spark-ignited internal combustion engines, such as gasoline engines, a large number of proposals for swirl-producing intake ports have been made. These have included both fixed geometry intake ports and variable geometry ports which have incorporated one or more movable components intended to provide a high degree of swirl under low engine load conditions and a reduced degree of swirl with improved charging and volumetric efficiency under high load conditions where a maximum cylinder charge is desired. However, a need remains for a simple fixed geometry intake port which can provide a substantial degree of swirl together with high volumetric charging efficiency. Summary of the Invention The present invention provides a fixed geometry engine cylinder intake port for use in internal combustion engines to provide cylinder charge swirl combined with a high degree of cylinder charging, or volumetric, efficiency. The improved intake port construction avoids the use of projecting vanes and side walls or other devices which restrict the flow of intake charges toward one side of the intake port and, instead, provides ramps of differing downward sloping angles on the upper wall of an intake port to direct flow into a swirl bowl under a shelf portion to the intake port at differing degrees of tangency, thereby creating swirl in the bowl portion and through the throat into the adjoining cylinder and combustion chamber. Preferably also, the port configurations in planes normal to the valve axis is such as to provide a relatively staighter flow path into the swirl bowl on the outer side of the valve axis under the shallower angled ramp and a more offset flow path into the swirl bowl on the inner side of the valve axis under the steeper angled ramp. The construction may also include a depending valve guide, with or without a leading edge fairing or guide wing to encourage laminar flow in the port, and is applicable to both curved and relatively straight upstream intake passage configurations. These and other features and advantages of the invention will be more fully understood from the following description of a preferred emodiment taken together with the accompanying drawings. Brief Drawing Description In the drawings: Figure l is a fragmentary lower plan view of a cylinder head of an eingine having an intake port in accordance with the invention as seen from the plane indicated by the line l-l of figure 2; Figure 2 is a cross-sectional view of the engine through the cylinder head intake port showing a lower angled ramp from the plane indicated by the line 2-2 of Figure l; Figure 3 is a cross-sectional view of the engine through the cylinder head intake port showing a higher angled ramp from the plane indicated by the line 3-3 of Figure l; Figure 4 is a cross-sectional view through the cylinder head of Figure l as seen from the plane indicated by the line 4-4 of Figure l; Figure 5 is a side view of an intake port core for forming a port according to the invention as seen from a plane indicated by line 5-5 of Figure 6; Figure 6 is a top view of the core of Figure 5, and Figure 7 is a pictorial view of the core of Figure 5. Detailed Description Referring now to the drawing in detail, numeral l0 generally indicates an internal combustion engine formed in accordance with the invention. Engine l0 conventionally includes a cylinder block ll having a plurality of cylinders l2, only one of which is shown. Pistons l4 are provided, one in each of the cylinders, and connecting rods l5 connecting the respective pistons with a crankshaft, not shown, supported in the cylinder block. A cylinder head l6 is mounted upon an upper end wall l8 of the cylinder block to close adjacent ends l9 of the cylinders. The cylinder head includes end walls 20, first and second side walls 22, 23 respectively and top and bottom walls 24, 26 respectively, the latter being seated upon the engine block upper end wall l8. At each cylinder location, a combustion chamber recess 27 is formed in the cylinder head bottom wall 26 at the end l9 of each cylinder opposite the top of its piston l4. The piston, cylinder and cylinder head, inculding the recess 27, from a variable volume working and combustion chamber 28. Connecting with the combustion chamber in the recess 27 are: a spark plug opening 30, an exhaust port 3l and an intake port 32 formed in accordance with the invention. The spark plug opening 30 conventionally receives a spark plug, not shown, having a spark gap within the combustion chamber recess. The exhaust port 3l extends from a circular exhaust valve seat 34 and throat 35, which open to the combustion chamber, along a curved flow path to an exhaust opening 36 through the second side wall 23 of the cylinder head for connection to an exhaust manifold, not shown. The intake port 32 extends from a circular intake valve seat 38 and adjacent throat portion 39 along a path, to be subsequently further described, to an inlet opening 40 through the first side wall 22 of the cylinder head for connection with an intake manifold, not shown. Poppet intake and exhaust valves 4l, 42, shown only in Figures 2 and 3 are provided for the intake and exhaust ports 32, 3l respectively. The exhaust valve 42 includes a circular head 43 that is seatable on the valve seat 34 and is supported by a valve stem 44 carried in a valve guide 46 mounted within the top wall 24 of the cylinder head. A spring 47 and conventional valve actuating mechanism, not shown, are provided to actuate the exhaust valve in timed relation to the engine crankshaft rotation. The intake valve 4l likewise includes a head 48 which is seatable upon the valve seat 38 to close and open flow through the intake port 32. A valve stem 49 extends on an axis 50 of reciprocation from the head of the intake valve and is reciprocably carried in a valve guide 5l mounted in the cylinder head top wall 24 in suitable guide bosses 52, 54. Like the exhaust valve, the intake valve 4l is acuated by suitable valve gear, not shown, in timed relation with engine crankshaft rotation. The valves 4l, 42 operate in conventional fashion to open and close the intake and exhaust port, respectively, to gas flow. In accordance with the invention, the shape of the intake port 32 is such as to develop charge swirl in the cylinder intake charges without unduly restricting the maximum flow of intake charges into the respective engine cylinder. In order to adequately visualize the shape of the intake port shown within the cylinder head illustrated in Figures l-4, the drawings further illustrate, in Figures 5-7, the configuration of a core usable for casting an inlet port according to the desired shape. In enumerating the features of construction of the port 32, the corresponding features of the core will be given identical numerals to clearly illustrate the relationship of these features. Therefore, it should be understood that the reference numerals used in Figures 5,6 and 7 illustrating the core actully refer to the corresponding features of the intake port which is formed by core. Extending from the inlet opening 40, the port 32 includes a passage-surrounding surface which may, for descriprive purposes, be divided into four walls including an upper wall 55, a lower wall 56 and left and right side walls 58, 59 respectively. The shape of the inlet opening 40 is essentially circular and the various top, bottom and side walls are connected with one another by generous arcuate surfaces and are formed with both single and compound curvatures to extend smoothly inward from the inlet opening 40. Thus, it will be understood that the separation or dividing lines between the connecting walls are not well defined and that the differing numerals are utilized primarily for purposes of description rather than otherwise. It should also be understood that the particular shape of the walls in the inlet portion of the port is not critical as affecting features of the invention, except that it is desirable that a smooth flow path be provided for inlet charges directed toward the engine combustion chamber. Approaching the valve stem 49 from the inlet opening 40, the intake port upper wall 55 is interrupted by the downwardly-extending valve guide boss 54 which has an upstream fairing, sometimes called a guide vane 60, which extends upwardly along the centre of the upper wall 55 to provide a smooth division of flow passing along the upper wall on either side of the valve guide and stem. The guide vane 60 includes an upstream edge 6l connected with the valve guide boss 54 by two faces 6la, 6lb which lie generally parallel with the direction of flow on the opposite sides of the guide boss with which these faces are respectively tangential to and connected. The presence or absence of a depending valve guide boss and/or an attached guide vane on the leading edge thereof, is also not critical to the concepts involved in the present invention, although shown and utilised in the illustrated embodiment. Along the upper wall, on either side of the guide boss and associated guide vane 60, the intake port is proveded with downwardly-angled outer and inner ramp portions 62, 63 respectively. The outer ramp portion 62 is so referred to by virtue of the fact that it extends downwardly over and in nearly tangential relation with, as viewed from above or below, the adjacent portion of the wall of the associated engine cylinder. The inner ramp portion 63 extends on the other side of the valve boss and guide vane and is angled generally towards the central portion of the combustion chamber. An essential feature of the invention is that the angles of the two ramp portions differ substantially. Thus, the inner ramp portion 63 is at a substantially steeper angle (up to l0° or more) than that of the outer ramp portion 62 as measured from a plane parallel with the bottom wall 26 of the cylinder head. At their lower ends, the ramp portions 62, 63 merge with a shelf portion 64 extending smoothly from the ends of the ramp portions at locations on generally opposite sides of the valve guide and associated valve axis. The shelf portion extends beyond the ramp ends in a direction generally parallel with the cylinder head bottom wall 26 and occupies a position spaced from and in generally opposing relation to the throat portion 39 of the intake port. At the port end below the shelf portion and around the axis of the intake valve 4l, an open bowl swirl chamber 66 is provided. The swirl chamber is generally centred on the valve axis and defined by convergence of the left and right side walls 58, 59 in cylindrical fashion around the valve axis to meet at the distal end 67 of the port. The lower portion of the swirl chamber is tapered inwardly to merge with the throat portion 39. It should be noted that due to a slight angularity of the valve axis with respect to the cylinder axis in the illustrated embodiment, the port configuration as seen in Figure l is slightly off-centre from the valve axis and extends farther towards the outer edge of the cylinder than toward the centre. However, Figures 5-7 show that the flow area on either side of the valve guide boss are approximately equal to one another. The differing angular slopes of the ramp portions 62, 63 have the effect of extending the length of the shallower outer ramp portion 62 and shortening the length of the steeper inner ramp portion 63. Accordingly, the ramps intersect the shelf portion 64 at staggered locations on opposite sides of the valve axis as indicated by diagonal lines 70 of Figures l, 6 and 7, which roughly indicate the intersections of the ramps with the shelf on either side of the valve boss. As a result of this construction, intake charge flow guided by the outer ramp portion 62 is led relatively far and somewhat tangentially into the swirl chamber 66 of the port on the outer side of the valve stem to cause swirl in a counterclockwise direction as viewed from the top of the port (clockwise as viewed from the bottom, as in Figure l). Flow guided by the steeper inner ramp portion 63 is forced in a more downwardly direction towards the intake port throat 39 on the inner side of the valve stem. Thus, the steeper slope of the inner ramp portion 63 not only reduces the rate of gas flow slightly on the inside of the port (by virtue of a greater change of direction) but also directs this flow in a more downwardly direction so that it has less of an effect on gas swirl. Accordingly, the overall effect of the ramp portions is to create counterclockwise swirl whilst providing large, relatively unimpeded flow paths on both sides of the intake valve stem and guide boss to permit relatively unrestricted flow of intake charge when the wide-open throttle or full load conditon is in effect. Preferably, the port configuration as viewed from a plane normal to the intake valve axis, or the cylinder axis as shown in Figures l and 6, is such as to provide relatively straight line flow in the port from the portion just upstream of the valve guide, or guide wing, to the outer side of the valve guide, or axis, underneath the shallower ramp portion 62. Flow to the inner side of the valve guide, or axis, under the steeper ramp portion 63 instead requires a slight change or offset in flow direction. This complements the effect of the ramp angle difference and provides a further slowing of flow in slight degree along the inner side of the valve axis as compared to the outer side, thus adding to the swirl developing capability of the port. In the particular example of the intake port configuration illustrated in the drawings, the port inlet opening 40 lies at a height above the throat 39 of about two times the diameter of the valve head 48. The central passage slopes downwardly at an angle of about 30-45°. The ramp portions 62, 63 lie at fairly steep angles of 30-60° with the plane of the cylinder head lower wall 26. The angle of the inner ramp portion 63 preferably exceeds the angle of the outer ramp portion 62 by about l0° or more. In the swirl chamber the diameter is somewhat greater than that of the port throat and the height from the throat 39 or valve seat 38 to the shelf 64 is similar to the diameter of the valve head 48. The flow area on either side of the valve guide is about evenly divided by the valve guide boss and guide vane. Also the shelf area equals about 40-50% of the swirl chamber area in a horizontal plane parallel with the cylinder head bottom wall 26. In flow box tests of a port according to the present design compared with a non-swirl open type port and a conventional helical swirl type port, the present invention developed swirl and flow characteristics superior to both and higher than either one in a substantial portion of the flow range. Among features of the design which are considered important in obtaining this result are the enlarged swirl chamber portion above the port throat partially covered by the flat shelf portion and the connecting ramp portions of differing angular slopes which alter the flow rates of the portions of the charge passing on either side of the valve stem and direct that flow at different angles so as to create a substantial swirl in the swirl chamber portion 66 which carries on through the throat 39 into the combustion chamber. Thus, in the present invention, the differently angled ramp portions 62,63 on the upper wall 55 on either side of the valve stem 49 direct inlet gas flow downward, slowing down said flow on the inner side of the port at the steeper ramp portion 63 and allowing faster flow which is more tangential to the cylinder wall at the shallower ramp portion 62. This creates swirl in the inlet gas flow. The flat shelf portion 64 and swirl chamber 66 beyond the valve stem kept the port open for unrestricted gas flow with high flow efficienty at full throttle.

Claims: 1. An internal combustion engine (l0) comprising a cylinder (l2) closed at one end (l9) and having an axis, an inlet passage (32) which communicates with the cylinder (l2) through the closed end (l9) thereof, and a poppet inlet valve (4l) including a stem (49) and head (48) having a valve axis (50) and disposed in the passage (32) for reciprocation on said valve axis (50) so as to control communication of the inlet passage (32) with the cylinder (l2), characterised in that said inlet passage (32) comprises a throat (39) of generally circular cross-section opening into the cylinder (l2) and adapted to be closed by the inlet valve (4l), an entrance portion (40) spaced from the throat (39) and offset from the valve axis (50), and a fluid flow path extending from the entrance portion (40) towards and around opposite sides of the valve axis (50) and below the valve head (48) when open to the throat (39), said fluid flow path being defined by a top wall (55) including first (62) and second (63) ramp portions and a shelf portion (64) spaced from and opposite the throat (39), said ramp portions (62,63) sloping downwardly and merging with the shelf portion (64) on generally opposite sides of the valve axis (50), the ramp portions (62,63) lying at steep angles to the shelf portion (64) and one (63) of the ramp portions having a substantially steeper angle than the other (62) to slow and direct downwardly fluid flow passing that steeper ramp portion (63) relative to fluid flow passing the other ramp portion (62) at a higher speed and with less downward deflection, whereby preferential entry of swirl-developing fluid flow into the area of the shelf portion (64) from below the ramp portion (62) of lower slope is encouraged. 2. An internal combustion engine (l0) according to claim l, characterised in that said fluid flow path includes a valve guide boss (54) surrounding the valve axis (50) and projecting part way into the flow path, said shelf portion (64) extends from adjacent the end of the valve guide boss (54) in generally spaced and opposing relation to the throat (39), and said ramp portions (62,63) merge with the shelf portion (64) adjacent the valve guide boss (54). 3. An internal combustion engine according to claim 2, characterised in that said inlet passage is configured so that flow on the side of the valve axis (50) below the steeper ramp portion (63) forms a greater angle with fluid flow in the passage (32) immediately upstream of the valve guide boss (54) than does fluid flow on the other side of the valve axis (50) below the shallower ramp portion (62), said greater angle being as measured in a plane normal to the valve axis (50), so that preferential flow into the shelf area from said other side of the valve axis (50) is further encouraged. 4. An internal combustion engine according to claim 3, characterised in that said valve guide boss (54) includes a guide vane (60) having two faces (6la,6lb) tangential to opposite sides of the valve boss (54) and intersecting in an upstream edge (6l), one of said faces (6lb) being associated with fluid flow on said other side of the valve axis (50) and lying substantially parallel to such fluid flow, said one face (6lb) being approximately aligned with fluid flow in the passage (32) immediately upstream of the guide vane (60), and the other (6la) of said faces being disposed at a substantial angle to said fluid flow. 5. An internal combustion engine (l0) comprising a cylinder (l2) having an axis, a cylinder head (l6) closing one end (l9) of the cylinder (l2), an inlet passage (32) through the cylinder head (l6) and communicating with the cylinder (l2) through the closed end (l9), and a poppet inlet valve (4l) having a central axis (50) offset to one side of the cylinder axis and reciprocally disposed in the passage (32) for controlling communication of the inlet passage (32) with the cylinder (l2), characterised in that said inlet passage comprises a throat (39) of generally circular cross-section centred on said valve axis (50) and opening into the cylinder (l2) adjacent one side thereof, said inlet valve (4l) being operative to open and close said throat (39); an entrance portion (40) spaced from the throat (39) and offset from the valve axis (50); and a fluid flow path extending from the entrance portion (40) towards and around opposite sides of the valve axis (50) to the throat (39), said flow path around the valve axis (50) being split into an inner path adjacent the cylinder axis and an outer path adjacent said side of the cylinder (l2), said fluid flow path being defined by a valve guide boss (54) surrounding the valve axis (50) and projecting part way into the flow path between the inner and outer paths thereof, and a top wall (55) including first (62) and second (63) ramp portions and a shelf portion (64), said shelf portion (64) extending from adjacent the end of the valve guide boss (54) in generally spaced and opposing relation to the throat (39), and said ramp portions (62,63) merging with the shelf portion (64) adjacent the valve guide boss (54), said ramp portions (62,63) sloping downwardly on opposite sides of the valve guide boss (54) and at steep angles to the shelf portion (64), one of the ramp portions (63) forming a wall of the inner flow path and having a substantially steeper angle than the other ramp portion (62), so as to slow and direct downwardly fluid flow in said inner path relative to the higher speed of fluid flow, with less downward direction, in the outer path defined in part by the shallower ramp portion (62), whereby preferential entry of swirl-developing fluid flow into the area of the shelf portion (64) from below the ramp portion (62) of lower slope is encouraged. 6. An internal combustion engine (l0) according to claim 5, characrterised in that said inlet passage (32) is configured so that flow in said outer path is substantially tangential with said cylinder side and the flow direction of said inner path forms a substantially greater angle with the direction of fluid flow in the passage (32) immediately upstream of the valve guide boss (54) than does the flow direction in said outer path, said greater engle being measured in a plane normal to the cylinder axis, so that preferential flow into the shelf area from said outer path is further encouraged. 7. An internal combustion engine (l0) according to claim 6, characterised in that said shelf portion (64) lies in a plane substantially normal to the cylinder axis. 8. An internal combustion engine (l0) according to claim 7 characterised in that said valve guide boss (54) includes a guide vane (60) having two faces (6la,6lb) tangential to opposite sides of the valve guide boss (54) and intersecting in an upstream edge (6l), one of said faces (6lb) in part defining said outer path of the flow path and being approximately aligned with the direction of fluid flow in the passage (32) immediately upstream of the guide vane, and the other of said faces (6la) being disposed at a substantial angle to said upstream fluid flow.

Inventors: FURLONG, C. GREGORY
Applicants: GENERAL MOTORS CORPORATION
Application year: 1986
Main classification: F02F1
IPC codes: F02B1, F02B31, F02F1