Patent ID: 12241436

DETAILED DESCRIPTION

FIG.1shows a vehicle100in which the invention may be used. In this example, the vehicle100is a car, but the invention is equally applicable to other vehicles driven by a lean-burn gasoline engine110. As mentioned above, it is to be noted that air intake port according to the invention and as described herein can be advantageously used in engines burning other fuels or fuel mixtures than gasoline. For example, the air intake port would be useful in a hydrogen burning internal combustion engine. In this vehicle100, the lean-burn gasoline engine110is positioned in the front and coupled to a drivetrain to drive the front and/or rear wheels of the vehicle100. The energy needed for driving the vehicle100is provided by burning fuel in the engine's cylinders causing the cylinder pistons to drive a crankshaft that is mechanically connected to the vehicle's drivetrain.

Compared to classic internal combustion engines, the lean-burn engine110of this vehicle100burns the fuel with an excess of air in the air-fuel mixture. Lean-burn engines may mix air and fuel in proportions of, for example, 20:1 (lambda>1.3) or even 30:1 (lambda>2). Advantages of lean-burn engines include more efficient fuel use and lower exhaust hydrocarbon emissions than conventional gasoline engines.

In order to enable the lean burning of fuel over a large portion of the engine map, i.e. in a large range of different engine speeds as well as engine output power or torque, the engine110is designed in such a way to enable a large air flow into the combustion chamber and a good mixing with the relatively small amount of fuel that is to be burnt to ensure a reliable combustion process that will effectively burn all fuel, despite the oxygen rich conditions.

FIG.2shows an air intake port10according to an embodiment of the invention. The air intake port10has an air inlet14and two air outlets15a,15b. An air channel connects the air inlet14to the two air outlets15a,15b. The first, upstream portion of the air channel, starting at the air inlet14forms a common duct11. Ata bifurcation point13, at a downstream end of the common duct11, the common duct11branches off in two port legs12a,12bthat provide the two respective air outlets15a,15b. The terms upstream and downstream are used to refer to parts of the air intake port10relative to flow of air through the air intake port10in its normal use with a lean-burn gasoline engine110. The predominant air flow direction is from an upstream position to a downstream position. It follows that in normal use the engine110is downstream of the air intake port10. The air outlets15a,15bare configured to connect to two respective inlets of the combustion chamber. Near the downstream ends of the port legs12a,12b, two valve guides16a,16are provided, each being configured to receive a valve stem that is used for controlling the valve that selectively opens and closes the combustion chamber inlets.

FIG.3schematically shows a bottom view of the air intake port10ofFIG.2. In addition to what has already been shown in and described with reference toFIG.2,FIG.3shows the air outlets15a,15b, and a sloped portion132in the common duct floor which leads to the bifurcation point13.FIG.3further shows a plane IV-IV through the air intake port10, from which the views on the inside of the air intake port10as shown inFIGS.4aand4bare. In addition thereto,FIG.3indicates, with three arrows33, the direction from which the cross section is viewed in the view ofFIGS.4aand4b.

The side views shown inFIGS.4aand4bthus show the inside of the air intake port10as seen from the plane IV-IV indicated inFIG.3. As will be explained below,FIGS.4aand4bshow two slightly different embodiments of the sharp bifurcation angle133according to the invention. From this viewpoint inside the common duct11, we look directly upon a side wall43of the common duct11and a side wall44of one of the leg ports12a. In addition to a side walls43,44, the common duct11and the port legs12a,12bmay have a ceiling41, a floor42, and another side wall (not shown). It is noted that the common duct11and the port legs12aare preferably not rectangularly shaped. Depending on the exact shape of the air intake port10, the boundaries of its floor42, side walls43,44, and ceiling41may not be easy to define. The common duct11and the port legs12a,12bmay, e.g., be tubular, oval, rectangular with rounded corners, or have flat floors42and/or ceilings41with curved side walls. Combinations and variations of such shapes are possible too. In preferred embodiments, however, at least the floor42of the common duct11is substantially flat.

In prior art air intake ports with one air intake and two air outlets, the bifurcation point is typically formed as a straight and substantially vertical wall or pillar that connects the air intake floor42to the air intake ceiling41. This vertical wall is situated centrally in the air intake port10, at the end of the common duct11. From there, the two port legs12a,12band there opposing inner walls diverge.

In this case, as can be seen in the side views ofFIGS.4aand4b, the bifurcation is a gradual transition and not, as in the prior art, a straight wall perpendicular to the air flow34through the common duct11. In a transition zone134at the downstream end of the common duct11, and in or around the centreline of the common duct11, the ceiling41and the floor42of the common duct11start approaching each other, until the sloped portions131,132of the ceiling41and the floor42meet each other in the bifurcation point13. If these sloped portions131,132are sufficiently long, they make a sharp bifurcation angle133at this bifurcation point13. The inventors have found that with such a sharp bifurcation angle, the air flow34is allowed to split in two, with far less disturbance than if the bifurcation is formed by a simple vertical wall (or an approximation thereof). In order to achieve this advantageous effect, a bifurcation angle133of less than 90° is preferred, however even better results may be obtained with even sharper bifurcation angles of, e.g., less than 75° 55°, or 45°.

In this example, the bifurcation point13is located centrally in the common duct11, i.e. midway between the two side walls and at equal distances from the floor42and the ceiling41. However, other, less symmetric configurations may be provided without departing from the scope of the invention. For example, the bifurcation point13may be positioned somewhat closer to the floor42, the sloped portion131at the ceiling41being steeper and/or longer than the sloped portion132near the floor42. In other embodiments the bifurcation point13may be somewhat rounded to further reduce air flow disturbances and/or because manufacturing constraints. It is noted that in the event of a slightly rounded bifurcation point13, the bifurcation angle133may be defined as the angle between the duct floor42and the duct ceiling41measured at a point beyond the rounded edge, e.g. at a position of 5 mm in front of the bifurcation point.

The sloped portions131,132in the floor and ceiling of the common duct11may be substantially straight or curved. In addition to a slope in the longitudinal direction, i.e. in the direction of the air flow, the sloped portions131,132are preferably sloped in the transverse direction too, thereby forming an aerodynamically shaped wedge-like structure.

According to the invention, the air channel floor42of the air intake port10ofFIGS.4aand4bis at least substantially flat in a direction of flow in a region adjacent to the air outlet15a,15b, but preferably along the whole port leg15a,15band part or the whole common duct11too. The purpose of this flat and even air channel floor42is to achieve a stable and undisturbed high-volume air flow that detaches from the underlying surface42and is launched into the combustion chamber when reaching the end of the air intake port10. The term ‘substantially flat’ may herein, e.g., be defined as having a difference between a minimum inclination and a maximum inclination that is less than 5 degrees.

Preferably, the flat portion of the air channel floor is designed such that the difference between the minimum and maximum inclination is less than 2, or even 1, degrees. In the example shown, the flat air channel floor42is a completely straight floor42with a constant inclination. In the event of a non-rectangular air channel, it may be difficult to distinguish the exact transition between the floor42, walls43,44, and ceiling41of the air channel. To obtain the described benefits of the described flat floor42, at least the central and lowest portion of the air channel is designed to be flat. Preferably, however, the floor42has a similar flatness in the direction of flow over at least half or even the full width of the air intake port10. With an air channel floor42that is at least substantially flat in a direction of flow in a region adjacent to the air outlet15a,15b, flow separation at the combustion chamber inlet significantly improved, thereby allowing the incoming air to first flow across the chamber before descending into the chamber. As a result, the desired tumble is achieved. This tumble is shown and discussed in more detail with reference toFIG.5.

It is noted that while the embodiments shown inFIGS.4aand4b, have this sloped or curved portion132that provides for a smooth transition towards the bifurcation point13, this will still allow for the floor42of the common duct11to be at least substantially flat in a direction of air flow. The portions132that are sloped or curved part of the side wall44separating the two port legs12a,12b. The air flow at either side of that side wall44can still follow a substantially flat floor42in the air flow direction. It is further to be noted that the now presented design of the bifurcation13and the substantially flat duct floor42both help to provide a stable and undisturbed high-volume air flow that detaches from the underlying surface42and is launched into the combustion chamber50when reaching the end of the air intake port10. Both measures add to the same technical effect that is already obtained by the use of a substantially flat floor42in at least a downstream portion of the port legs12a,12b. However, the advantageous effects of a substantially flat floor42in the common duct can also be obtained with a vertical wall type bifurcation.

FIG.5shows a cross section of a combustion chamber50with a retracted piston54and a closed inlet valve51. A dotted line59provides a simplified2D representation of the preferred air flow into and through the combustion chamber50. It is noted that the air flow into the combustion chamber50is not possible with a closed inlet valve51but is shown for the purpose of illustration only, shows a cross section of a combustion chamber50with a retracted piston54and a closed inlet valve51.

With the valve51and air inlet design of this embodiment, it is possible to create a tumble motion of the incoming air, first along the roof of the combustion chamber50towards the opposite wall, under the outlet valve55that closes off the exhaust outlet56, and then down along that opposing wall, back over the top surface of the piston54and up along the combustion chamber wall in the direction of the inlet valve51again. This tumble is preferably kept in motion during the full intake stroke and at least a portion of the compression stroke of the piston54moving through the combustion chamber50. The thus produced tumble helps to obtain an optimal distribution of air and fuel inside the combustion chamber50that can then break down into turbulence to facilitate the subsequent combustion process.

In order to create the desired tumble, the valve51and the air inlet of the combustion chamber50are designed such that the air flow entering the combustion chamber50is promoted to detach from the floor of the port leg12a,12bof the air intake port10and to flow along the ceiling of the combustion chamber50. Some of the specific design features that can help to promote the desired tumble are discussed below with reference toFIGS.6,7a, and7b.

FIGS.6,7a, and7bshows a close-up of the inlet valve51ofFIG.5. As can be seen in all these Figures, the air channel floor42of the port leg12a,12bis flat in the full region up to the air outlet15a,15bof the air intake port10. The flat air channel floor42promotes the detachment of the air flow as soon as it leaves the air intake port10and enters the combustion chamber50, which contributes to the desired tumble.

The movable valve51comprises a bottom surface61that faces the combustion chamber50and a tapered top surface62that faces the air intake port10. The inlet valve51is provided at the end of a valve stem63. This inlet valve51is arranged to move by controlling the position of the valve stem63. The movable valve51may be moved between a closed state (FIG.6) for closing off the combustion chamber inlet and an opened state (FIGS.7aand7b) wherein intake air can flow from the air intake port10into the combustion chamber50. The throat comprises a tapered surface71that is complementary with the tapered top surface62of the movable valve51, such that when the movable valve51is in its closed position, the movable valve51at least partially sinks into the throat.

This tumble is preferably kept in motion during the full intake stroke and at least a portion of the compression stroke of the piston54moving through the combustion chamber50. The complementary tapered surfaces62,71of the intake valve51and the throat together ensure that during the compression stroke, when the intake valve51is closed, no or little air can get trapped behind the valve51or between the valve51and an inner surface of the combustion chamber50while tumbling through the combustion chamber50. The further the valve51is allowed to sink into the throat, the less disturbance it can cause to the desired tumble. In an embodiment of the invention, the bottom surface61of the movable valve51may even be substantially flush with an inner surface of the combustion chamber50when the movable valve51is in its closed position.

Due to the tapered surface of the throat, and because the valve51needs to be able to close off the air inlet, the diameter of the combustion chamber inlet is smaller than the valve diameter. The valve diameter is determined by the bottom surface61of the valve51. In an embodiment of the invention, the diameter of the combustion chamber inlet is less than, e.g., 95% or 90% of a diameter of the bottom surface61of the movable valve51. Not only does this allow for the desired taper71in the throat surface, the protruding upstream portion of the throat also helps to shield of the valve edge, thereby directing the air flow over the top surface62of the valve51(seeFIG.7a) and along the roof of the combustion chamber50instead of around the valve edge and down along the wall closest to the combustion chamber inlet.

This effect can further be enhanced by the protruding upstream portion ending with a sharp edge73that promotes detachment of the air flow. In this example, the sharp edge73coincides with the outer end of the air channel floor42at the air outlet15a,15bof the air intake port10.

While this is the preferred embodiment, the channel floor42may alternatively end at a position in front of or behind the sharp edge73. In preferred embodiments, the angle between the channel floor42and an adjacent portion of the throat is at least 225 degrees. However, angles closer to, or even beyond, 270 degrees are even more preferred. The larger the angle, the smaller the chance that the airflow will adhere to the throat surface and finds a way down into the combustion chamber50immediately upon entering.

Additionally, an optional deflector72is provided at an inner wall of the combustion chamber50and protruding radially therefrom. The deflector72is positioned underneath an outer edge of the bottom surface61of the movable valve51. This deflector72is arranged such that an air flow moving up along the inner wall of the combustion chamber50is deflected radially inward and away from the outer edge of the bottom surface61of the movable valve51. As a result, the risk of any air being trapped behind the valve51when in a closed or almost closed position is reduced. This useful deflector72, on top of that, brings the additional advantage that during the intake stroke, when the valve51is at least partially open and air is drawn into the combustion chamber50, any air unintentionally bouncing of the top surface62of the valve51will be prevented from flowing down along the nearest inner wall of the combustion chamber50. Instead, the deflector72will block this astray air flow back into the chamber50, and in the direction of the desired tumble.

In a preferred embodiment of this lean-burn gasoline engine110, the air intake port10and the valve51are arranged such that when the valve51is in its opened position, the complete bottom surface of the valve51is positioned below the air intake port10. This allows the separated air flow leaving the air intake port10to flow along the roof of the combustion chamber50and towards the opposite chamber wall with minimal disturbance by the valve51it has to pass. In an even more preferred embodiment, the complete bottom surface61of the valve51is already positioned below the air intake port10when the valve51is only half-way between its closed position and its opened position. This further allows reduced flow disturbance by the valve51while the valve is still opening, thereby facilitating the creation of the desired tumble as soon as the valve51is opened. In alternative embodiments, the complete bottom surface61drops below the air intake port10when the valve is, e.g., 60% open.

In a further embodiment, the air intake port10and the valve51are arranged such that when the valve51is in its opened position, also the complete top surface62of the valve51is positioned below the air intake port10, with the tapered angle of the top surface62at a similar angle as the port floor, which leads to even less disturbance of the air flow, and helps to direct the air flow across the top of the chamber, with a more prominent and stable tumble as a result. The top surface62may be inclined slightly upward at the point where the air flow may hit the valve51in order to lift the air flow up in the direction of the chamber ceiling and/or the top end of the opposing wall.

It will be appreciated that various changes and modifications can be made to the present invention without departing from the scope of the present application.