GB2280931A

GB2280931A - Four-stroke engine.

Info

Publication number: GB2280931A
Application number: GB9316867A
Authority: GB
Inventors: Edwin Seymour Marsden
Original assignee: Individual
Current assignee: Individual
Priority date: 1993-08-13
Filing date: 1993-08-13
Publication date: 1995-02-15
Also published as: AU7349894A; WO1995005533A1; GB9316867D0

Abstract

The intake valve 50 and the exhaust valves 36 and 52 are closed during an initial part of the induction stroke to produce a vacuum in the combustion chamber 34. Fuel is drawn or injected prior to, during or after opening of the valve 50 during the induction stroke to provide vaporisation. The valve 52 is opened towards the end of the power stroke and the valve 35 during the exhaust stroke. Fuel may be drawn through a cylinder port 38. <IMAGE>

Description

INTERNAL COMBUSTION ENGINE AND METHOD OF OPERATION the present invention relates to an internal combustion engine and to a method of operating an internal combustion engine.

It is known to operate an internal combustion engine in a four-stroke cycle during which a vapourised fuel/air mixture is ignited to produce a power stroke. However, in the past, in order to ensure that the fuel/air mixture is efficiently vapourised over a wide range of temperature conditions it has been the practice to employ fuels having relatively high vapour pressures. This is not only costly in the sense that fuels having high vapour pressures are typically more expensive to produce but such a practice is also harmful to the environment.

The evapouration of automotive fuels from carborretors, fuel tanks and fuel transfer facilities is a major contributor to the increase in recent years of atmospheric hydrocarbons which in turn give rise to smog.

This problem will only be exacerbated by the continued use of fuels having high vapour pressures. It would therefore clearly be advantageous to provide a method of operating an internal combustion engine in which the need to use such fuels was removed. This would not only enable the engine concerned to run on a cheaper fuel but also slow down the generation of atmospheric hydrocarbons.

According to a first aspect of the present invention there is provided a method of operating an internal combustion engine in a four-stroke cycle comprising the steps of reducing the pressure within the combustion chamber during a first part of the induction stroke and admitting fuel into the reduced pressure environment within the combustion chamber during a second part of the induction stroke so as to facilitate the vapourisation of the fuel.

Advantageously the fuel may be drawn into the combustion chamber solely as a result of the suction force generated by the reduced pressure existing within the combustion chamber.

Advantageously air may be admitted to the combustion chamber after the fuel and at a time when a reduced pressure exists within the combustion chamber so as to facilitate the mixing of the air with the vapourised fuel.

Alternatively, air may be admitted to the combustion chamber at substantially the same time as the fuel so as to again facilitate the mixing of the air with the vapourised fuel. In another arrangement air may be admitted to the combustion chamber prior to the fuel and at a time when a reduced pressure exists within the combustion chamber.

Preferably the air may be drawn into the combustion chamber solely as a result of the suction force generated by the reduced pressure existing within the combustion chamber.

Advantageously the internal combustion engine may be of the type comprising a piston adapted for reciprocal movement within a cylinder, air intake port means for admitting air into the cylinder, fuel intake port means for admitting fuel into the cylinder and exhaust port means, and the pressure within the combustion chamber may be reduced by causing the piston to move for at least a proportion of the induction stroke while all of said air intake port means, said fuel intake port means and said exhaust port means are closed. Preferably the piston may be caused to move at least half the length of the induction stroke while all of said air intake port means, said fuel intake port means and said exhaust port means are closed.

Advantageously the exhaust port means may comprise an exhaust port disposed within a side wall of the cylinder and located close to the bottom of the travel of the piston, the exhaust port being opened toward the end of the power stroke so as to enable the cylinder to be purged of exhaust gases. Alternatively, or in addition, the exhaust port means may also comprise an exhaust port disposed within the cylinder head, this exhaust port being opened during the exhaust stroke to again enable the cylinder to be purged of exhaust gases.

According to a second aspect of the present invention there is provided a four stroke internal combustion engine comprising a piston adapted for reciprocal movement within a cylinder and which with the cylinder defines a combustion chamber, means for reducing the pressure within the combustion chamber during a first part of the induction stroke, and means for admitting the fuel into reduced pressure environment within the combustion chamber during a second part of the induction stroke so as to facilitate the vapourisation of the fuel.

Advantageously means may be provided to admit air to the combustion chamber after the fuel and at a time when a reduced pressure exists within the combustion chamber so as to facilitate the mixing of the air with the vapourised fuel. Alternatively, means may be provided to admit air to the combustion chamber at substantially the same time as the fuel so as to again facilitate the mixing of the air with the vapourised fuel. In another arrangement means may be provided to admit air to the combustion chamber prior to the fuel and at a time when a reduced pressure exists within the combustion chamber.

Advantageouly the engine may comprise air intake port means for admitting air into the cylinder, fuel intake port means for admitting fuel into the cylinder and exhaust port means and said means for reducing the pressure within the combustion chamber during the first part of the induction stroke may comprise means for causing the piston to move for at least a proportion of the induction stroke while all of said air intake port means, said fuel intake port means and said exhaust port means are closed.Preferably said means for causing the piston to move for at least a proportion of the industion stroke while all of said air intake port means, said fuel intake port means and said exhaust port means are closed may comprise means for causing the piston to move through at least half the length of the induction stroke while all of said air intake port means, said fuel intake port means and exhaust port means are closed.

Advantageously one or both of the fuel intake port means and the air intake port means may be provided within the cylinder head. Alternatively, one or both of the fuel intake port means and the air intake port means may be provided within a side wall of the cylinder.

Advantageously the exhaust port means may comprise an exhaust port disposed within a side wall of the cylinder and located close to the bottom of the travel of the piston, the exhaust port being opened towards the end of the power stroke so as to enable the cylinder to be purged of exhaust gases. Alternatively, or in addition, the exhaust port means may also comprise an exhaust port disposed within the cylinder head, this exhaust port being opened during the exhaust stroke to again enable the cylinder to be purged of exhaust gases. Preferably the exhaust port disposed within the cylinder head may comprise a rotatable exhaust valve.

An embodiment of the present invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is a schematic cross-sectional view of a cylinder of an internal combustion engine operating by a method in accordance with an embodiment of the present invention; Figure 2 is schematic cross-sectional view of the cylinder of Figure 1 in which the piston has moved through a porportion of the induction stroke while all of the air intake port, the fuel intake port, the exhaust port and the exhaust valve are closed; Figure 3 is a schematic cross-sectional view of the cylinder of Figure 1 in which the piston has moved through a larger proportion of the induction stroke so as to uncover the fuel intake port and the fuel intake port has been opened;; Figure 4 is a schematic cross-sectional view of the cylinder of Figure 1 in which the piston has moved through a still larger proportion of the induction stroke so as to uncover the air intake port and the air intake port has been opened; Figure 5 is a schematic cross-sectional view of the cylinder of Figure 1 in which the piston has moved through the compression stroke to compress the vapourised fuel/air mixture; Figure 6 is a schematic cross-section view of the cylinder of Figure 1 in which the compressed fuel/air mixture is ignited to produce a power stroke; Figure 7 is a schematic cross-sectional view of the cylinder of Figure 1 in which the piston has moved through the power stroke so as to uncover the exhaust port and the exhaust port has been opened; and Figure 8 is a schematic cross-sectional view of the cylinder of Figure 1 in which the piston has moved through the exhaust stroke and the exhaust valve has been opened.

Whilst the accompanying drawings only illustrate a single cylinder of an internal combustion engine, it will be understood that each cylinder of a typically multi-cylindered engine has a number of common features and that each may be operated in accordance with the same sequence all be it perhaps in different phases. For this reason the following description will be restricted to a describing method of operating a single cylinder of an internal combustion engine.

Referring to Figure 1, there is shown a piston 10 adapted for reciprocal movement within a cylinder 12. In particular, the piston 10 can be seen to comprise an upper surface 14 surrounded by a depending side wall or skirt 16. The piston 10 is pivotally connected to one end 18 of a connecting rod 20, while at an end 22 remote from the piston 10, the connecting rod 20 is pivotally connected to a crank shaft 24.

By contrast, the cylinder 12 comprises a side wall 26 closed at one end by a cylinder head 28. Within the cylinder head 28 there is provided a bore 30 which communicates both with an exhaust pipe 32 and with a combustion chamber 34 located within the cylinder 12 and defined by the upper surface of the piston 14, the side wall of the cylinder 26 and the cylinder head 28. A rotatable exhaust valve 36 is disposed within the bore 30 and is adapted for rotation between a first position in which the exhaust valve 36 serves to close the bore 30 and a second position in which the exhaust valve is open and the combustion chamber 34 communicates with the exhaust pipe 32.

In addition to the exhaust valve 36, the cylinder 12 is also provided in the side wall 26 with a fuel intake port 38, an air intake port 40 and an exhaust port 42. The fuel intake port 38 is disposed at a location spaced from the cylinder head 28 but above the air intake port 40 and communicates by means of a fuel line 44 with a fuel supply (not shown). The fuel line 44 is provided with a metering valve 46 such that when the fuel intake port 38 is opened only a predetermined quantity of fuel is admitted to the combusion chamber 34.

In contrast to the fuel intake port 38, the air intake port 40 is spaced close to the bottom of the travel of the piston 10 where it is closed by a first sleeve valve 50. The exhaust port 42 is also located close to the bottom of the travel of the piston 10 and, like the air intake port 40, is closed by a second sleeve valve 52.

In use, the piston 10 is moved by virtue of the rotation of the crank shaft 24 from the position shown in Figure 1 where it occupies Top Dead Centre (TDC) to the position shown in Figure 2. During this movement the rotatable exhaust valve 36, the fuel intake port 38, the air intake port 40 and the exhaust port 42 remain closed.

As a result the small quantity of gas contained within the combustion chamber 34 when the piston 10 is at TDC is subjected to a rapid decrease in pressure.

When the downward movement of the piston 10 reaches the position shown in Figure 3, the predetermined quantity of fuel that is passed by the metering valve 46 is sucked into the cylinder 12 through the fuel intake part 38 where it is rapidly vaporised on account of the reduced pressure existing within the combustion chamber 34.

Thus it can be seen that the provision of a reduced pressure within the cylinder 12 serves a twofold purpose.

Not only does it facilitate the vaporisation of the fuel, thereby enabling the use as fuels of substances having a lower than normal vapour pressure such as, for example, Kerosene or Light Gas Oil, but it also eliminates the need for a complicated fuel injection system capable of both injecting and vaporising a predetermined quantity of fuel into the combustion chamber within a sufficiently short time interval.

As the piston 10 nears Bottom Dead Centre (BDC) as shown in Figure 4, the first sleeve valve 50 is opened to admit air into the cylinder 12 through the air intake port 40. Although the previously admitted fuel exhibits a partial pressure of its own, the combustion chamber 34 will still be at a reduced pressure compared with the air intake and as a result air will be sucked into the cylinder 12 where it will rapidly mix with the already vaporised fuel.

Having reached BDC, continued rotation of the crank shaft 24 causes the piston 10 to move upwardly within the cylinder towards TDC. The first sleeve valve 50 is closed and the fuel/air mixture within the combustion chamber 34 compressed until the piston reaches the position shown in Figure 5. At or near TDC, as shown in Figure 6, the fuel/air mixture is ignited, whether by spark ignition or otherwise, causing a rapid expansion in the volume of the ignited mixture and driving the piston 10 from TDC to BDC in a power stroke.

As the piston 10 nears BDC the second sleeve valve 52 is opened thereby allowing the preliminary removal of the burnt gases from the cylinder 12 through the exhaust port 42 as shown in Figure 7. Having reached BDC, the second sleeve valve 52 is closed and the piston 10 returns to TDC in an exhaust stroke. At the same time, the exhaust valve 36 is rotated from the closed position to the open position so that as the piston 10 moves upwardly within the cylinder 12, as shown in Figure 8, it drives out any remaining exhaust gases through the bore 30.

Once the piston has reached TDC the exhaust valve 36 is rotated back to its closed position enabling the described four-stroke cycle to begin again.

Whilst the fuel intake port 38 and the air intake port 40 have been described as being provided within a side wall 26 of the cylinder 12, it will be apparent to those skilled in the art that this need not necessarily be the case. Instead, both the fuel intake port 38 and the air intake port 40 may, for example, be provided within the cylinder head 28.

Likewise, whilst the cylinder has been described as having both an exhaust valve 36 and an exhaust port 42, it will be apparent to those skilled in the art that the cylinder 12 may also be operated having only one such exhaust port means.

Although the method of operating the cylinder has been described in terms of admitting the fuel to the combustion chamber 34 prior to the admission of the air, this again need not necessarily be the case. However, it is to be noted that if air is admitted to the combustion chamber 34 prior to the admission of the fuel, then the partial pressure of the air within the cylinder 12 will raise the pressure within the combustion chamber and so hinder the ease with which the fuel might otherwise be drawn into the cylinder and subsequently vapourised.

One of the advantages of the described method is that it dispenses with the need to provide complicated apparatus for the injection of either the fuel or the air into the combustion chamber 34. It will be apparent however, that some form of injection apparatus might also be used in conjunction with either the fuel or the air intake ports 38 and 40 without detracting from the other advantages associated with the use of fuels having lower than normal vapour pressures.

A further advantage of the described method, and one that has not been specifically mentioned thus far, is that the engine cycle is capable of operating in either rotary direction of the crank shaft 24.

Claims

1. A method of operating an internal combustion engine in a four-stroke cycle comprising the steps of reducing the pressure within the combustion chamber during a first part of the induction stroke and admitting fuel into the reduced pressure environment within the combustion chamber during a second part of the induction stroke so as to facilitate the vapourisation of the fuel.

2. A method in accordance with claim 1, wherein the fuel is drawn into the combustion chamber solely as a result of the suction force generated by the reduced pressure existing within the combustion chamber.

3. A method in accordance with claim 1 or claim 2, wherein air is admitted to the combustion chamber after the fuel and at a time when a reduced pressure exists within the combustion chamber so as to facilitate the mixing of the air with the vapourised fuel.

4. A method in accordance with claim 1 or claim 2, wherein air is admitted to the combustion chamber at substantially the same time as the fuel so as to facilitate the mixing of the air with the vapourised fuel.

5. A method in accordance with claim 1 or claim 2, wherein air is admitted to the combustion chamber prior to the fuel and at a time when a reduced pressure exists within the combustion chamber.

6. A method in accordance with any of claims 3 to 5, wherein the air is drawn into the combustion chamber solely as a result of the suction force generated by the reduced presurre existing within the combustion chamber.

7. A method in accordance with any of claims 1 to 6, wherein the internal combustion engine is of the type comprising a piston adapted for reciprocal movement within a cylinder, air intake port means for admitting air into the cylinder, fuel intake port means for admitting fuel into the cylinder and exhaust port means, and the pressure within the combustion chamber is reduced by causing the piston to move for at least a proportion of the induction stroke while all of said air intake port means, said fuel intake port means and said exhaust port means are closed.

8. A method in accordance with claim 7, wherein the piston is caused to move through at least half the length of the induction stroke while all of said air intake port means, said fuel intake port means and said exhaust port means are closed.

9. A method in accordance with claim 7 or claim 8, wherein said exhaust port means comprises an exhaust port disposed within a side wall of the cylinder and located close to the bottom of the travel of the piston, the exhaust port being opened toward the end of the power stroke so as to enable the cylinder to be purged of exhaust gases.

10. A method in accordance with any of claims 7 to 9, wherein the exhaust port means comprises an exhaust port disposed within the cylinder head, the exhaust port being opened during the exhaust stroke to enable the cylinder to be purged of exhaust gases.

11. A four-stroke internal combustion engine comprising a piston adapted for reciprocal movement within a cylinder and which with the cylinder defines a combustion chamber, means for reducing the pressure within the combustion chamber during a first part of the induction stroke, and means for admitting fuel into the reduced pressure environment within the combustion chamber during a second part of the induction stroke so as to facilitate the vapourisation of the fuel.

12. An engine in accordance with claim 11, wherein means are provided to admit air to the combustion chamber after the fuel and at a time when a reduced pressure exists within the combustion chamber so as to facilitate the mixing of the air with the vapourised fuel.

13. An engine in accordance with claim 11, wherein means are provided to admit air to the combustion chamber at substantially the same time as the fuel so as to facilitate the mixing of the air with the vapourised fuel.

14. An engine in accordance with claim 11, wherein means are provided to admit air to the combustion chamber prior to the fuel and at a time when a reduced pressure exists within the combustion chamber.

15. An engine in accordance with any of claims 11 to 14, and comprising air intake port means for admitting air into the cylinder, fuel intake port means for admitting fuel into the cylinder and exhaust port means, wherein said means for reducing the pressure within the combustion chamber during a first part of the induction stroke comprises means for causing the piston to move for at least proportion of the induction stroke while all of said air intake port means, said fuel intake port means and said exhaust port means are closed.

16. An engine in accordance with claim 15, wherein said means for causing the piston to move through at least a proportion of the induction stroke while all of said air intake port means, said fuel intake port means and said exhaust port means are closed comprises means to move the piston through at least half the length of the induction stroke.

17. An engine in accordance with claim 15 or claim 16, wherein one or both of said fuel intake port means and said air intake port means are provided within the cylinder head.

18. An engine in accordance with claim 15 or claim 16, wherein one or both of said fuel intake port means and said air intake port means are provided within a side wall of the cylinder.

19. An engine in accordance with any of claims 15 to 18, wherein said exhaust port means comprises an exhaust port disposed within a side wall of the cylinder and located close to the bottom of the travel of the piston, the exhaust port being opened toward the end of the power stroke so as to enable the cylinder to be purged of exhaust gases.

20. An engine in accordance with any of claims 15 to 19, wherein the exhaust port means comprises an exhaust port disposed within the cylinder head, the exhaust port being open during the exhaust stroke to enable the cylinder to be purged of exhaust gases.

21. An engine in accordance with claim 20, wherein said exhaust port comprises a rotatable exhaust valve.

22. A method of operating an internal combustion engine in a four-stroke cycle substantially as herein described with reference to the accompanying drawings.

23. A four-stroke internal combustion engine substantially as herein described with reference to the accompanying drawings.