GB2381293A

GB2381293A - I.c. engine charge motion control valve

Info

Publication number: GB2381293A
Application number: GB0126077A
Authority: GB
Inventors: Thomas Tsoi Hei Ma
Original assignee: Individual
Current assignee: Individual
Priority date: 2001-10-25
Filing date: 2001-10-30
Publication date: 2003-04-30
Also published as: GB0125630D0; GB0126077D0

Abstract

A charge motion control valve (20, 22) is described mounted for independent movement of and coaxially with a poppet valve (12) both inside an intake port (10) of an internal combustion engine. The charge motion control valve is rotatable about the poppet valve stem (14) to different angular positions and is shaped such that it blocks a variable part of the port in close proximity to a variable segment of the circumference of the poppet valve opening (16) and thereby forces the flow to change its main direction as the flow leaves the poppet valve opening (16) depending on the angular position of the control valve. The charge motion control valve of the invention may be designed to produce either swirl or tumble within the combustion chamber of a poppet-valved internal combustion engine. In the latter case, it may be designed to vary the direction and the intensity of tumble.

Description

CHARGE MOTION CONTROL VALVE Field of the invention The present invention relates to a control valve located inside an intake port of an internal combustion engine for varying either the swirl or the tumble charge motion within the combustion chamber of the engine.

Background of the invention It is known in an internal combustion engine having intake and exhaust poppet valves and operating according to a four-stroke engine cycle, to introduce either tumble motion or swirl motion within the combustion chamber for promoting mixture turbulence and/or charge stratification during the intake and compression phases of the four-stroke cycle. It is also known in an internal combustion engine having intake and exhaust poppet valves and operating according to a two-stroke engine cycle, to introduce tumble motion within the combustion chamber for promoting loop scavenging of the cylinder charge during the gas exchange phase of the two-stroke cycle. Tumble is herein defined as the rotation of the cylinder charge in a plane parallel with the longitudinal axis of the engine cylinder. Swirl is defined as the rotation of the cylinder charge about the longitudinal axis of the engine cylinder.

In the case of a poppet-valved four-stroke engine, the tumble motion may take the form of either forward tumble in which the flow from the intake port is directed immediately across the roof of the combustion chamber before being deflected by the cylinder wall towards the piston, or reverse tumble in which the flow from the intake port is directed away from the roof of the combustion chamber and is deflected immediately by the cylinder wall towards the piston. Either direction of tumble motion is effective for

promoting mixture turbulence and/or charge stratification, but other considerations, such as avoiding wetting of the fuel on the cylinder wall, favour the choice of forward tumble in order to reduce exhaust emissions.

In the case of a poppet-valved two-stroke engine, on the other hand, forward tumble is to be avoided because of the risk of short-circuiting of the intake air directly into the exhaust port without scavenging the cylinder contents when the intake and exhaust valves are simultaneously open during the gas exchange phase. It is therefore important to introduce reverse tumble in a poppet-valved two-stroke engine to ensure effective loop scavenging.

Whilst it is possible to design the engine intake port to produce a pre-determined swirl or tumble motion, it is desirable to vary, either or both, the direction and the intensity of the charge motion selectively according to engine operating conditions. A known device for varying the intensity of the charge motion comprises a butterfly throttle mounted in the intake port as close as possible to the poppet valve and adjustable between two positions, a first position where the flow is restricted to concentrate along one side of the intake port when a strong charge motion is required, and a second position where the flow is permitted to pass unobstructed through the entire crosssection of the intake port when maximum flow efficiency is required. Such a device however is not very effective because of the unavoidable separation between the butterfly throttle and the poppet valve in practice. It is also not capable of varying the direction of tumble motion to produce either forward tumble or reverse tumble selectively according to engine operating conditions.

Summary of the invention One aim of the present invention is to provide a charge motion control valve capable of varying the direction and the intensity of tumble within the combustion chamber of an internal combustion engine. Another aim is to provide a charge motion control valve capable of varying the intensity of swirl within the combustion chamber.

According to the present invention, there is provided a charge motion control valve mounted for independent movement of and coaxially with a poppet valve both inside an intake port of an internal combustion engine, wherein the charge motion control valve is rotatable about the poppet valve stem to different angular positions and is shaped such that it blocks a variable part of the port in close proximity to a variable segment of the circumference of the poppet valve opening and thereby forces the flow to change its main direction as the flow leaves the poppet valve opening depending on the angular position of the control valve.

In a preferred embodiment of the invention, the charge motion control valve comprises a thin plate mounted above the poppet valve head and dividing the port section above the valve head, wherein the plate is rotatable about the poppet valve stem to different angular positions and is shaped such that it blocks a variable flow section of the port corresponding to a segment of the circumference of the poppet valve opening behind the plate and thereby forces the flow to pass predominantly through another segment of the circumference of the poppet valve opening in front of the plate depending on the angular position of the control valve.

In this embodiment, the charge motion control valve may be designed to reverse the direction of tumble by deflecting the flow frontally. Alternatively, it may be designed to

produce swirl by deflecting the flow slantingly. The plate may be flat, curved or twist-shaped. Of course the plate may be rotated to an angular position where it causes the minimum flow obstruction so that the full circumference of the poppet valve opening may be utilised when required.

In another embodiment of the invention, the charge motion control valve comprises a lip segment mounted in close proximity to the circumference of the poppet valve opening, wherein the lip segment is rotatable about the poppet valve stem to different angular positions and is shaped such that it blocks a variable flow section of the port corresponding to a segment of the circumference of the poppet valve opening close to the lip and thereby forces the flow to pass predominantly through another segment of the circumference of the poppet valve opening further away from the lip depending on the position of the control valve.

In this embodiment, the charge motion control valve may be designed to produce tumble by shrouding the poppet valve opening directly across the intake port. Alternatively, it may be designed to produce swirl by shrouding the poppet valve opening on one side of the intake port.

In a further embodiment of the invention, the charge motion control valve comprises a thin shell mounted above the poppet valve head and conforming substantially to the hollow end shape of the intake port, wherein the shell is rotatable about the poppet valve stem to different angular positions and is shaped such that it blocks a variable flow section from one side of the intake port extending from near the circumference of the poppet valve opening and combines with the end volume of the intake port to form a vortex chamber above the poppet valve head with a tangential flow opening into the chamber from the other side of the intake port, and thereby forces the flow to rotate at a variable angular velocity within the port before the flow leaves the

poppet valve opening depending on the angular position of the control valve.

In this embodiment, the charge motion control valve modifies the flow inside the intake port in an analogous manner to that of a conventional helical port design, but has the advantage that the effect is variable capable of producing very high swirl when the control valve is nearly closed and very low swirl with direct through flow when the control valve is fully open.

In the present invention, the charge motion control valve may be secured rotatably to the roof of the intake port, or to the end of a valve guide fitted to the intake port for guiding the movement of the poppet valve. The securing means may be a forked bracket, a rotatable spring clip or by magnetic force.

It should be noted that although the charge motion control valve is mounted so that it is rotatabe about the poppet valve stem, it is not essential for it to be in direct contact with the valve stem. On the other hand, it is preferred to provide a close fit between the control valve and the poppet valve stem so that the control valve is located accurately by the valve stem while the poppet valve moves freely through its operating cycle.

An actuation linkage may be connected to the charge motion control valve for rotating the valve and holding it at different angular positions according to engine operating conditions. The linkage may preferably be arranged to pass along the primary flow duct of the intake port to an actuator outside the port. Furthermore, a return spring may preferably be provided for biasing the charge motion control valve towards a default angular position against an end-stop so that the actuation linkage only needs to operate in one direction against the return spring.

Brief description of the drawing The invention will now be described further, by way of example, with reference to the accompanying drawings in which: Figures la and 1b are schematic part-sectional drawings of a preferred embodiment of the invention, Figures 2a and 2b are schematic part-sectional drawings of another embodiment of the invention, and Figures 3a and 3b are schematic part-sectional drawings of a further embodiment of the invention.

Detailed description of the preferred embodiment In all the Figures, an intake port 10 is shown with a poppet valve 12 for an internal combustion engine where the poppet valve 12 is guided along its valve stem 14 by a valve guide 18-During the intake phase, the charge enters via the intake port 10 and passes through a circumferential valve flow area 16 when the poppet valve 12 is open.

Figures la and 1b show a charge motion control valve comprising a wing plate 22 fixed to a sleeve 20 which is mounted for rotation about the poppet valve stem 14 and is butted towards the end of the valve guide 18. The wing plate 22 is located directly above the poppet valve head 12 thus bisecting the port section above the valve head 12. A magnetic washer 24 is provided between the valve guide 18 and the sleeve 20 (both made of ferrous materials) so that the sleeve 20 will remain attached rotatably to the valve guide 18 while the poppet valve 12 moves through its operating cycle. An actuation linkage 26 shown only in the plan view of Figure 1b is connected to the charge motion control valve for rotating the valve between two positions shown separately in Figures la and 1b respectively. The linkage 26 is arranged to pass along the primary flow duct 10 of the intake port to an actuator 28 outside the port.

In the first angular position of the plate 22 as shown in Figure la, the plate 22 is perpendicular to the direction of the primary flow duct 10 of the intake port such that it blocks a section of the port corresponding to one half of the circumference of the poppet valve opening 16 behind the plate 22 and thereby forces the flow to pass predominantly through the remaining half of the circumference of the poppet valve opening 16 in front of the plate 22.

In the second angular position of the plate 22 as shown in Figure lb, the plate 22 is parallel with the direction of the primary flow duct 10 of the intake port such that the plate 22 permits unobstructed flow through both halves of the circumference of the poppet valve opening 16 on either side of the plate 22.

The charge motion control valve shown in Figures la and 1b may be used to produce reverse tumble in one angular position and forward tumble in another angular position depending on the orientation of the intake port 10 relative to the cylinder wall of the combustion chamber. It may also be used to produce swirl by rotating the plate 22 to an intermediate angular position between the positions shown in Figures la and lb.

The control valve position shown in Figure la may also be applied in the exhaust port of a poppet-valved two-stroke internal combustion engine. In this case, the function of the control valve is not to vary the charge motion before combustion, but to improve the loop scavenging of exhaust gases by allowing the outflow to pass through only one half of the circumference of the exhaust valve opening.

Figures 2a and 2b show another charge motion control valve comprising a lip segment 32 fixed to a sleeve 30 which is mounted for rotation about the poppet valve stem 14 and is butted towards the end of the valve guide 18. The lip 32

is located in close proximity to the circumference of the poppet valve opening 16. The sleeve 30 is secured rotatably to the end of the valve guide 18 by a spring clip 34 which holds the sleeve 30 while the poppet valve 12 moves through its operating cycle. An actuation linkage 36 shown only in the plan view of Figure 2b is connected to the charge motion control valve for rotating it between two positions shown separately in Figures 2a and 2b respectively. The linkage 36 is arranged to pass along the primary flow duct 10 of the intake port to an actuator 38 outside the port.

In the first angular position of the lip segment 32 as shown in Figure 2a, the lip 32 protrudes into the primary flow duct 10 of the intake port such that it blocks a rim section of the port corresponding to a segment of the circumference of the poppet valve opening 16 close to the lip segment 32 and thereby forces the flow to pass across the port to the opposite side of the circumference of the poppet valve opening 16 further away from the lip 32.

In the second angular position of the lip segment 32 as shown in Figure 2b, the lip 32 is not protruding into the primary flow duct 10 but lies close to the side wall of the intake port surrounding the poppet valve head 12 thereby permitting unobstructed flow past the full circumference of the poppet valve opening 16.

The charge motion control valve shown in Figures 2a and 2b may be used to vary the intensity of tumble without changing the direction of tumble. It may also be used to produce swirl by rotating the lip segment 32 to an intermediate angular position between the positions shown in Figures 2a and 2b.

Figures 3a and 3b show a further charge motion control valve comprising a thin shell 42 fixed to a sleeve 40 which is mounted for rotation about the poppet valve stem 14 and

is butted towards the end of the valve guide 18. The shell 42 is mounted above the poppet valve head 12 and conforms substantially to the hollow end shape of the intake port 10. A forked bracket 44 is provided for rotatably supporting the sleeve 40 by engaging with a flange formed at the end of the sleeve 40 while the poppet valve 12 moves through its operating cycle. An actuation cable 46 shown only in the plan view of Figure 3b is connected to the charge motion control valve for rotating the valve between two positions shown separately in Figures 3a and 3b respectively. The cable 46 is arranged to pass along the primary flow duct 10 of the intake port to an actuator 48 outside the port. A return spring 50 is also shown in the plan view of Figure 3b for biasing the control valve towards a default angular position against an end-stop (not shown). In this case, the actuation cable 46 needs only to pull in one direction against the return spring 50 for setting the control valve.

In the first angular position of the shell 42 as shown in Figure 3a, and position 42"in dash line additionally shown in the plan view of Figure 3a, the shell 42 (42") blocks a substantial section of the intake port 10 from one side of the port wall extending from near the circumference of the poppet valve opening 16. This creates a vortex chamber above the poppet valve head 12 formed by a combination of the end wall of the intake port 10 and the hollow shell 42 (42"). In this position, flow enters the vortex chamber via a narrow tangential opening from the other side of the port wall creating a strong rotation within the port volume above the poppet valve head 12.

Finally the rotating flow enters the engine cylinder through the poppet valve opening 16 and its angular momentum is transferred to the charge inside the cylinder resulting in a strong swirling motion within the cylinder.

In the second angular position of the shell 42 as shown in Figure 3b, the shell 42 does not block the intake port 10

but blends with the end wall of the intake port 10. In this case, there is no vortex above the poppet valve head 12 and a direct through flow will leave the poppet valve opening 16 with a main direction along the direction of the primary flow duct 10 of the intake port.

The charge motion control valve shown in Figure 3a produces swirl in the engine cylinder in an analogous manner to that of a conventional"helical port"design. On the other hand, it can be changed to a conventional"flow port" design when required simply by rotating the shell 42 to the full flow position as shown in Figure 3b. By varying the angular position of the shell 42 (42"), a wide range of swirl intensities may be produced within the cylinder.

When in the swirl position (42"), the charge motion control valve also acts as an individual port throttle with a very small pressure recovery volume between the throttling section and the closed poppet valve. By using it in conjunction with, or in place of, a conventional main throttle for varying the engine load, the control valve of this embodiment has the advantage of significantly reducing the pumping work at low loads hence reducing fuel consumption, and at the same time, increasing mixture turbulence and/or charge stratification hence improving combustion stability and reducing exhaust emissions.

Finally, in order to derive the maximum benefit from the charge motion control valve of the present invention, the shape of the intake port should be designed taking into account the presence of the control valve and the required range of rotation of the valve, so that the control valve may be moved freely and the flow efficiency of the intake port is not compromised.

Claims

1. A charge motion control valve mounted for independent movement of and coaxially with a poppet valve both inside an intake port of an internal combustion engine, wherein the charge motion control valve is rotatable about the poppet valve stem to different angular positions and is shaped such that it blocks a variable part of the port in close proximity to a variable segment of the circumference of the poppet valve opening and thereby forces the flow to change its main direction as the flow leaves the poppet valve opening depending on the angular position of the control valve.

2. A charge motion control valve as claimed in claim 1, wherein the valve comprises a thin plate mounted above the poppet valve head and dividing the port section above the valve head, and wherein the plate is rotatable about the poppet valve stem to different angular positions and is shaped such that it blocks a variable flow section of the intake port corresponding to a segment of the circumference of the poppet valve opening behind the plate and thereby forces the flow to pass predominantly through another segment of the circumference of the poppet valve opening in front of the plate depending on the angular position of the control valve.

3. A charge motion control valve as claimed in claim 1, wherein the valve comprises a lip segment mounted in close proximity to the circumference of the poppet valve opening, and wherein the lip segment is rotatable about the poppet valve stem to different angular positions and is shaped such that it blocks a variable flow section of the intake port corresponding to a segment of the circumference of the poppet valve opening close to the lip and thereby forces the flow to pass predominantly through another segment of the circumference of the poppet valve opening

further away from the lip depending on the angular position of the control valve.

4. A charge motion control valve as claimed in claim 1, wherein the valve comprises a thin shell mounted above the poppet valve head and conforming substantially to the hollow end shape of the intake port, and wherein the shell is rotatable about the poppet valve stem to different angular positions and is shaped such that it blocks a variable flow section from one side of the intake port extending from near the circumference of the poppet valve opening and combines with the end volume of the intake port to form a vortex chamber above the poppet valve head with a tangential flow opening into the chamber from the other side of the intake port, and thereby forces the flow to rotate at a variable angular velocity within the port before the flow leaves the poppet valve opening depending on the angular position of the control valve.

5. A charge motion control valve as claimed in any one of claims 1 to 4, secured rotatably to the roof of the intake port.

6. A charge motion control valve as claimed in any one of claims 1 to 4, secured rotatably to the end of a valve guide fitted to the intake port for guiding the movement of the poppet valve.

7. A charge motion control valve as claimed in any preceding claim, mounted in close fit with the poppet valve stem.

8. A charge motion control valve as claimed in any preceding claim, wherein an actuation linkage is connected to the charge motion control valve for rotating the valve and holding it at different angular positions according to engine operating conditions.

9. A charge motion control valve as claimed in any preceding claim, wherein a return spring is provided for biasing the charge motion control valve towards a default angular position against an end-stop.