INLET DUCTS IN INTERNAL COMBUSTION ENGINES

Abstract: An inlet duct construction in a cylinder head of an internal combustion engine supplies fuel and air through an inlet port controlled by a streamlined poppet valve head (12). The inlet duct comprises at least two inlet tracts (9A, 9B) which may each include a respective throttle (14A, 14B) and a respective fuel injection (15A, 15B). The throttles and/or injectors are individually controllable to give a stratified fuel-air charge. The tracts may discharge through the port with a tangential component.

Description: INLET DUCTS IN INTERNAL COMBUSTION ENGINES The present invention relates to inlet ducts in internal combustion engines. A conventional inlet duct for supplying air or fuel-air mixture to a combustion chamber through an inlet port which includes an annular valve seat for a poppet valve member having a head and a stem. Since the valve stem has to be guided in a valve guide mounted in the sylinder head, the inlet tract leading to the port has to be curved. As a result, the incoming charge of gases tends to flow through the port only on that side of the valve head which corresponds to the least departure from a straight line from the inlet tract. Thus, only part of the annular area between the valve head and its seat is effectively used when the valve is open. It has already been proposed in British Patent specification no. 1225245 to overcome this problem # by providing two or more inlet tracts- distributed around the axis of the inlet valve converging on the inlet port so that the combined momentum of gas streams entering the inlet port from the tracts is parallel with the valve axis. According to the invention, there is provided an inlet duct construction for an internal combustion engine in which an inlet duct comprises a plurality of inlet tracts distributed around r.hc axis of an inlet poppet valve member cooperating with a valve seat defining an inlet port, characterised by means for individually controlling the amounts of air and/or fuel in individual ones of the inlet tracts. The invention will now be further described by way of example with reference to the accompanying diagrammatic drawings, in which : Figure 1 is a vertical section through an inlet duct portion of a cylinder head, of conventional design, - Figure 2 is a similar view of a known modification, Figures 3 to 6 are views similar to Figures 1 and 2 of four embodiments of the invention, and Figures 7 and 8 show, respectively, aligned and tangentially offset dispositions of the inlet tracts. relative to the inlet port of Figure 6. Figure 1 of the drawings shows a conventional inlet ^ duct for supplying air or fuel-air mixture to a combustion chamber 1 through an inlet port 2 which includes an annular valve seat 3 for a poppet valve member 4 having a head 5 and a stem 6. Since the stem 6 has . to be guided in a valve guide 7 mounted in the cylinder head 8, the inlet tract 9 leading to the port 2 has to be curved. As a result, the incoming charge of gases tends to flow through the port 2 on one side only of the valve head 5 (the left-hand side as shown in Figure 1) which corresponds to the least departure from a straight line from the inlet tract 9. This flow path is indicated by the arrows 10 in Figure 1. Thus, with the conventional arrangement shown in Figure 1, only part of the annular area between the valve head 5 and its seat 3 is effectively used when the valve is open. Figure 2 of the drawings shows an arrangement of the kind known from British Patent specification no. 1225245 having two symmetrically disposed inlet tracts 9A and 9B leading into the port 2. In accordance with one aspect of the " present invention, as illustrated in Figure 3 of the accompanying drawings, the flow pattern through the port 2 is further enhanced by an appropriate aerodynamical shaping of the back surface 11 of the valve head 12. This is possible since it is no longer necessary, with a plurality of inlet tracts 9, to make the valve head as thin as possible. The lift of the valve 12 may be variable in accordance with engine load and/or speed, or as a power-control throttle. The valve lift is advantageously such as to result in inlet gas speeds of about 120 metres per second. In the arrangement shown in Figure 4, means are provided for individually controlling the amount of air and/or fuel in individual ones of the inlet tracts. In Figure 4 the two inlet tracts 9A and 9B have individually controlled throttle valves 14A and 14B which may be operated for example by stepper motors individually controlled by a microrpocessor-operated engine management system. With this arrangement, at least under some conditions a greater quantity of air or fuel/air mixture may be supplied along one tract then along the other. If the mixture supplied along one tract is , richer than the other (which may even be plain air) the flow patterns past the valve head 5 or 12 imposed by the settings of the throttle 14A and 14B are such as to produce a stratified charge of mixture within the combustion chamber, for the purpose, for example, of ensuring a suf iciently rich mixture adjacent a spark plug to ensure Ignition while the remainder of the mixture is leaner and more economical. Figure 5 shows an alternative arrangement In accordance with the two aspects of the invention where each inlet tract 9A and 9B has its own fuel injector 15A, 15B orientated to deliver fuel to the air flows passing on each side of the valve head through the inlet port 2. Here again, the two fuel injectors 15A and 15B are individually controlled to deliver Individually determined amounts of fuel to their respective inlet tracts in accordance with varying operating conditions such as speed and load of the engine and/or provide a stratified charge. Figure 6 shows ' a combination of the features of Figures 4 and 5 in an arrangement in which the axis of the valve and thus the axis of symmetry of the inlet tracts is inclined relative to the axis of the cylinder bore 17 to enhance the formation of a stratified charge. Figure 7 is a schematic plan view of an inlet port arrangement in which the axes of the two tracts 9A and 9B intersect the axis of the valve member whereas in Figure 8 these axes are offset to give the gases entering the combustion chamber a tangential swirl component. In one development of the invention, the number of inlet tracts 9 is such that they together form an almost continuous annular convergent inlet duct with the support structure for the valve guide 7 forming a spider.

Claims: CLAIMS : 1. An inlet duct construction for an internal combustion engine in which an inlet duct comprises a plurality of inlet tracts (9A,9B) distributed around the axis of an inlet poppet- valve member (5,12) cooperating with a valve seat (3) defining an inlet port (2), characterised by means (14A,B; 15A,B) for individually controlling the amounts of air and/or fuel in individual ones of the inlet tracts (9A.9B). . ' 2. An inlet duct construction according to claim 1, characterised in that the back surface (11) of the head of the valve member (12) is aerodynamicall shaped, for example for streamline flow in the region of the port. 3. An inlet duct construction according to claim 1, characterised. in that each tract has an individually controllable throttle valve (14A,B). 4. An inlet duct construction according to claim 1, characterised in that each. tract has an individually controllable fuel injection (15A, 15B). 5. An inlet duct construction according to claim 1, characterised in that each tract has an individually controllable throttle valve (14A,B) and an individually controllable fuel injector (15A, 15B) . 6. An inlet duct construction for an internal combustion engine in which an inlet duct comprises a plurality of inlet tracts (9A,9B) distributed around the axis of an inlet poppet valve member (5,12) cooperating with a valve seat (3) defining an Inlet port (2), characterised in that the back surface (11) of the head of the valve member (12) Is aerodynamically shaped, for example for streamline flow, in the region of the port.

Inventors: HENROTTE GEORGE ARTHUR, HENROTTE, GEORGE, ARTHUR
Applicants: PIPER LTD F M, PIPER F M LIMITED
Application year: 1985
Main classification: F02F1
IPC codes: F02F1