GB2267124A

GB2267124A - I.c.engine valve gear.

Info

Publication number: GB2267124A
Application number: GB9209124A
Authority: GB
Inventors: Harry Leslie James Dixon
Original assignee: Individual
Current assignee: Individual
Priority date: 1992-04-28
Filing date: 1992-04-28
Publication date: 1993-11-24
Anticipated expiration: 2012-04-28
Also published as: GB2267124B; GB9209124D0

Abstract

The cylinder has a primary port 1 controlled by a primary valve 2 that remains open for both admission and exhaust. A secondary valve 3 is positioned in the duct to and from the primary port 1 but in close proximity so that the secondary valve 3 sweeps across the mouth of the primary port 1 moving residue gas away from the common flow space 7. The secondary valve 3 alternately connects the inlet 11 and exhaust 10 to the primary port 1. The primary valve may be a poppet valve (19, Fig. 3) with the secondary valve in two pans (22, Fig. 4) which pass on either side of the valve stem. The secondary valve may be a piston valve (15, Fig. 2). <IMAGE>

Description

INTERNAL COMBUSTION ENGINE VALUE GEAR AND CYLINDER HEAD This invention relates to internal combustion engine valve gear and cylinder head.

It is current practice in four stroke internal combustion engines to provide a minimum of two valves per cylinder, one for admission and one for exhaust.

To improve breathing, there are increasing examples of three or more valves per cylinder adding to the complexity of design and manufacture.

Another approach made to improve breathing has been to use a single valve, alternatively called a primary valve, for the dual function of admission and exhaust of gases.

A secondary valve positioned outside the combustion chamber, is required to connect the primary valve sequentially with the inlet system and exhaust system.

The chamber between the primary valve and secondary valve is hereinafter termed an intervalve space.

The major advantage of the single valve concept is it only requires half the area in the cylinder head combustion space when compared to an equivalent conventional engine. Therefore, by increasing the single valve area, it is easier to achieve improved breathing by this concept. This advantage is often outweighed in this type of arrangement where the secondary valve is positioned such that some of the residue gases remain in the intervalve space.

For example, burnt gases remain in the intervalve space at the end of the exhaust stroke and are then drawn again into the cylinder during the first part of the induction stroke resulting in loss of engine efficiency. A number of indirect methods have been proposed to clear the intervalve space, for example, compressed air or exhaust pipe tuning, but a more positive solution now follows.

According to the present invention there is provided an internal combustion engine where each cylinder has a primary port controlled by a primary valve that remains open for both admission and exhaust. A secondary valve positioned outside the combustion chamber in the duct from the primary valve port but in close proximity so that the secondary valve sweeps across the mouth of the primary valve port moving residue gas away from the intervalve space, that is inlet gas back to the inlet system and the exhaust gas towards the exhaust system.

In order that the invention may be clearly understood, three embodiments of the invention will now be described by way of example with reference to the accompanying drawings in which : Figure 1 is a schematic section through a cylinder head of an engine constructed to a first embodiment.

Figure 2 is a schematic section through a cylinder head of an engine constructed to a second embodiment.

Figure 3 is a schematic section through a cylinder head of an engine constructed to a third embodiment.

Figure 4 is a side view showing a schematic section through the secondary valve used in the third embodiment.

Figure 5 is a side view of the inlet system sealing faces used in the third embodiment.

Figure 6 is a plan view showing a schematic section through the primary valve and guide used in the first embodiment.

Figure 7 is a front view showing a schematic section through the primary valve and guide used in the first embodiment.

Figure 8 is a stroke diagram showing diagrammatically the positions of the primary and secondary valves.

The invention can be applied to all types of internal combustion engines, for example, spark ignition engines, spark ignition gas engines and diesel engines.

Referring to Figure 8, this is a diagrammatic representation of the valve timing versus cycle position.

This illustrates that the primary valve is closed and stationary for just under one engine revolution and for a similar period when the valve is open.

The secondary valve has the function of connecting the primary valve to either the inlet or exhaust systems and various valve timing arrangements are possible, for example, if the secondary valve closes after the primary valve, the timing 39 and speed 40 of return of the secondary valve to close the inlet and open exhaust is not critical.

Referring to figure 1, the slide valve 2 (solid without an aperture) is moved by valve operating gear (not shown) in a direction at right angles to the piston 5 travel allowing the valve 2 to remain open for the exhaust and induction strokes, then closed for the compression and power strokes. The flap valve 3, moved by the valve operating gear (not shown) moves across the mouth of the primary port 1 connecting either the inlet or exhaust systems to the primary port 1 in accordance to the cycle requirements.

Figure 1 shows the cylinder 4 on the exhaust stroke where piston 5 moves in cylinder 4 towards the cylinder head 6 containing a slide valve 2 in the open position 13 and the inlet system is closed off by the flap valve 3 at position 8. The piston 5 moves the exhaust gas through the primary port 1 to the intervalve space 7 and out through the exhaust system 10. Exhaust gas flow is improved by the smooth path through primary port 1 and exhaust passage 7 and 10.

At the end of the exhaust stroke, the slide valve 2 remains open at position 13 and the flap valve 3, moved by the valve operating gear (not shown), sweeps across the primary port 1 to close off the exhaust system at 9. The effect of the flap valve 3 movement is to push the residue exhaust gases in the intervalve space 7 towards the exhaust outlet 10 and draw inlet gases 11 into the intervalve space 7 towards primary port 1. The inlet gas flow is drawn into the cylinder 4 by the piston 5 moving away on the induction stroke. Inlet gas flow is improved by the smooth path through the intervalve space 7 and primary port 1.

At the end of the induction stroke, valve operating gear (not shown) closes the slide valve 2 to 12, shuttingoff the primary port 1. The flap valve 3 sweeps across the primary port 1 to close off the inlet system at 8. The effect of the flap valve movement is to push the residue inlet gases in the intervalve space 7 back to the inlet system 11.

With the slide valve 2 closing the primary port at 12, the cycle continues on the compression and power strokes.

Figure 2 shows a slide valve (with aperature) 14 as primary and a piston valve 15 as secondary moved by a connecting rod 16 and valve operating gear (not shown). The connecting rod 16 is shown operating from the inlet side 11, alternatively it can operate from the exhaust system side 10.

The valve operation is similar to the first embodiment, for example, the cylinder 4 is on the exhaust stroke where piston 5 moves in cylinder 4 towards the cylinder head 6 containing a slide valve 14 in the open position 13 and the inlet system is closed off by the piston valve 15 at position 17.

The exhaust gases have a smooth path through primary port 1, intervalve space 7 to exhaust system 10. At the end of the exhaust stroke, the slide valve 14 remains open at position 13 and the piston valve 15, moved by connecting rod 16, sweeps across the primary port 1 to close off the exhaust system at position 18. The effect of the piston valve 15 movement is to push the residue exhaust gases in the intervalve space 7 towards the exhaust outlet 10 and draw inlet gases 11 into the intervalve space 7 towards primary port 1.

The cycle continues as the first embodiment.

Figure 3 is a third embodiment showing a poppet valve 19 as primary and a two part flap valve 22 as secondary. The popularity of the poppet valve in internal cumbustion engines is due to its excellent sealing characteristics under high temperatures and pressures.

To adapt a flap valve 22 to work with a poppet valve 19 requires the flap valve 22 to be divided along its vertical centreline to provide a gap to clear the poppet valve 19 stem and head contours to permit the flap valve 22 to sweep across the primary port 1. The method of operation is similar to the first and second embodiments, except that in comparison, the gas flow is deflected around the poppet valve 19, for example, on the exhaust stroke the gas flow moves around the mushroom head and stem 7 to exhaust system 10.

Also, the fLap valve 22 centre gap allows some pollution of inlet and exhaust gases when valve 22 moves from one system to the other.

Figure 4 is a side view of a two part flap valve 22 used in the third embodiment. The poppet valve 19 stem (not shown) passes between the two parts of the flap valve 22 in the space 29 and through the valve guide bush 27 The flap valve pivot bosses 25 are in two parts, each supported between pivot bearings in the valve guide bush 30 and cylinder head 31. The effective cross-sectional area of the flap valve 22 should approximate to the primary poIt t 1 area and formed to any suitable shape, for example, circular or elliptical.

Figure 5 shows the inlet system sealing surfaces on the peripheral face 34 and vertical centre seal 35 matching the two part flap valve 22 and gap (figure 4 item 29). The exhaust system will have a similar construction. Figure 4, the flap valve 22 is operated either by two arms 26 and 33 or by arm 26 and a joining brace 32 for the pivot bosses.

In comparing the slide valve with its main rival the poppet valve, the major advantages of the slide valve are absence of obstructions in the cylinder head, primary port and intervalve space and quieter in operation.

The potential slide valve problem areas when this type of valve is used in high speed internal combustion engines can be improved as follows:1. Figure 6 shows a plan view of a solid slide valve 2 in the open position 13. Slide valves generally have apertures in the valve to match the ports in the cylinder or cylinder head but these increase the valve (Figure 2 item 14) length and mass, an alternative is to make the valve solid without aperture.

2. Figure 7 shows a solid slide valve 2 in the closed position 12. Sealing under high pressures and temperatures can be improved by fitting a flexible thin ring 37 or solid ring (not shown) at the periphery of the primary port so that the high cylinder pressures forces the ring against the closed face of the slide valve.

Note that the slide valve is stationary during the closed period.

To reduce the effects of carbon deposits, a recess or dimple 38 can be made into the slide valve in the area enclosed by the primary port.

3. The slide valve stroke can be longer than desirable on primary ports that are circular and large to take advantage of the cylinder bore size. The effect of this can be reduced by using alternative primary port shapes, for example, an ellipse and using the shorter axis for the stroke direction. Note that this will also reduce the secondary valve stroke requirements in the first and second embodiments.

The invention can apply to a primary port of any shape that matches the primary valve requirements. There can be single or multiple combinations of primary port, primary valve and secondary valve in each cylinder.

KEY TO DIAGRAMS 1. Primary Port.

2. Slide valve (solid without aperture).

3. Flap valve.

4. Cylinder.

5. Piston.

6. Cylinder head.

7. Intervalve space.

8. Flap valve 3 position - inlet closed/exhaust open.

9. Flap valve 3 position - exhaust closed/inlet open.

10. Exhaust system gas outlet.

11. Inlet system gas inlet.

12. Slide valve position - closed.

13. Slide valve position - open.

14. Slide valve (with aperture).

15. Piston valve.

16. Piston valve 15 connecting rod.

17. Piston valve 15 position - inlet closed/exhaust open.

18. Piston valve 15 position - exhaust closed/inlet open.

19. Poppet valve.

20. Poppet valve 19 position - closed.

21. Poppet valve 19 position - open.

22. Two part flap valve.

23. Flap valve 22 position - inlet closed/exhaust open.

24. Flap valve 22 position - exhaust closed/inlet open.

25. Flap valve 22 Boss.

26. Flap valve 22 Lever arm.

27. Poppet valve 19 Guide.

28. Poppet valve 19 Cam.

29. Clearance gap for poppet valve.

30. Flap valve 22 Pivot bearing - inner location.

31. Flap valve 22 Pivot bearing - outer location.

32. Flap valve 22 Pivot bosses joining brace.

33. Flap valve 22 Second lever arm.

34. Inlet system peripheral face seal.

35. Inlet system Vertical centre seal.

36. Slide valve 2 Connecting rod.

37. Flexible thin ring.

38. Recess or dimple.

39. Secondary valve timing point - inlet closing/exhaust opening.

40. Secondary valve speed of change from inlet closing to exhaust opening.

Claims

1. An internal combustion engine where each cylinder has a primary port controlled by a primary valve that remains open for both admission and exhaust. A secondary valve positioned outside the combustion chamber in the duct from the primary valve port but in close proximity so that the secondary valve sweeps across the mouth of the primary valve port moving residue gas away from the inter valve space, that is inlet gas back to the inlet system and the exhaust gas towards the exhaust system.

2. A system according to Claim 1 where there are multiple combinations of primary port, primary valve and secondary valve in each cylinder.

3. A system according to Claim 1 or 2 wherein the primary valve commences to open at a point in the cycle usual for the opening of the exhaust valve and closes at a point usual for the closing of the inlet valve.

4. A system according to Claim 3 wherein the secondary valve connects the primary valve to either the inlet system or the exhaust system to meet the valve timing requirements of the engine.

5. A system according to Claim 4 wherein the primary valve is a slide valve, either solid or with an aperture, and the primary port can be any suitable shape.

6. A system according to Claim 5 wherein a flexible thin ring or a solid ring is fitted at the periphery of the primary port so that high cylinder pressures forces the ring against the closed face of the slide valve.

7. A system according to Claim 5 or 6 wherein a recess or dimple is made in the slide valve closed face within the primary-valve port area.

8. A system according to Claims 5 to 7 wherein the secondary valve is a flap valve.

9. A system according to Claims 5 to 7 wherein the secondary valve is a piston valve, the connecting rod can be either on the inlet or exhaust system side.

10. A system according to Claim 4 wherein the primary valve is a poppet valve.

11. A system according to Claim 10 wherein the secondary valve is a two part flap valve with the flap valve divided along the centre line to provide a gap to clear the poppet valve stem and head contours.

12. An internal combustion engine having induction and exhaust systems substantially as herein described with reference to Figures 1 to 8 of the accompanying drawings.