GB2218152A

GB2218152A - I.C. engine air and mixture intake system

Info

Publication number: GB2218152A
Application number: GB8810597A
Authority: GB
Inventors: Chuen Fu; Edison Tao Ling Fu
Original assignee: Individual
Current assignee: Individual
Priority date: 1988-05-05
Filing date: 1988-05-05
Publication date: 1989-11-08
Also published as: GB8810597D0

Abstract

The intake valve 16 or the two-stroke engine port (128, Figs, 3 and 4) of an air and fuel intake passage of a cylinder 12 of the engine 10 is closed when secondary air is being drawn into the downstream end 28 of the intake passage 18 through the secondary air intake system 30. The air replaces carburetted fuel-air mixture thereby forming a fresh stratified charge at the downstream of the intake passage which is to be drawn into the cylinder during the following intake operation. <IMAGE>

Description

AIR AND FUEL SYSTEM OF AN INTERNAL COMBUSTION ENGINE This invention relates in general to an air and fuel system of an internal combustion engine and in particular to an improved air and fuel intake system of an internal combustion engine, It is an object of the present invention to provide an air and fuel system for use in an internal combustion engine which allows air and fuel mixture to shuttle within the intake manifold of the air and fuel system of the engine.

It is another object of the present invention to provide a stratified charge internal combustion engine of higher charge density and higher compress ion ratio.

It is yet another object of the present invention to produce a stratified charge internal combuston engine having a relatively simple construction and yet of high engine efficiency.

In accordance with the present invention, there is provided an air and fuel system for use in an internal combustion engine of the type having a secondary air intake system in which the intake valve or port of an air and fuel Intake passage of a cylinder of the engine is closed when secondary air is being drawn into the downstream of the intake passage of a cylinder through the secondary air intake system replacing the carburetted fuel-air mixture which is being drawn backward in a direction away from the cylinder by suction or intake operation of the engine thereby forming a fresh stratified charge at the downstream of the intake passage which is to be drawn into the cylinder during the following intake operation.

During the intake of the stratified charge, the first intake portion of the charge consisting mostly of secondary air from the secondary air intake system is generally positioned in a region directly on top of the piston head whilst the last intake portion of the stratified charge consisting mostly of carburetted fuel-air mixture is generally positioned in an area adjacent the cylinder head where a spark plug is located.

In accordance with the present invention, there is provided also an internal combustion engine of the type having a secondary air intake system comprislng an air and fuel intake passage for intaking carburetted fuel mixture into a cylinder of the engine, and an air intake means for intaking secondary air into the intake manifold.

The air intake means opens at one end to the downstream of the intake passage and at the other end to the atmosphere. At least a portion of the intake passage defines a temporary storing space for the storage of the intake secondary air before it enters the cylinder of the engine.

The intake passage also defines a passageway along which air and fuel mixture are shuttling in both directions during the operation of the engine.

The internal combustion engine characterized in that the intake valve or port of an intake passage of a cylinder of the engine is closed when secondary air is being drawn into the downstream of the intake passage of said cylinder through the secondary air intake system replacing the carburetted fuel-air mixture which is being drawn backward in a direction away from the cylinder by suction or intake operation of the engine thereby forming a fresh stratified charge at the downstream of the intake passage which is to be drawn into said cylinder during the following intake operation, and that during the intake of the stratified charge the first intake portion of the charge consisting mostly of secondary air from the secondary air intake system is generally positioned in a region directly on top of the piston head whilst the last intake portion of the stratified charge consisting mostly of carburetted fuelair mixture is generally positioned in an area adjacent the cylinder head where a spark plug is located.

In order that the invention may be fully understood, it will now be described with reference to the accompanying drawings, wherein: Figure 1 is a diagrammatic vertical section of a four-stroke cycle engine showing a secondary air intake system; Figure 2 is a diagrammatic vertical section of the four-stroke cycle engine of Figure 1 showing another embodiment of a secondary air intake system; Figure 3 is a diagrammatic vertical section of a two-stroke cycle engine in operation with a secondary air intake system during an exhaust/compression stroke when the piston is being driven to the top of the cylinder and the leaf valve of the secondary air intake system is in an open position; and Figure 4 is a diagrammatic vertical section of the two-stroke cycle engine of Figure 3 during an power/intake stroke when the piston is being driven to the bottom of the cylinder and the leaf valve of the secondary air intake system is in a closed position.

Referring now in more detail to the drawing, Figure 1 depicts an internal combustion engine designated generally by reference numeral 10. The internal combustion engine 10, being illustrated as a four-stroke cycle engine, includes as in conventional a cylinder 12, a piston 14 adapted to move reciprocally within the cylinder 12, an intake valve 16 and an intake manifold 18 in communication with a conventional carburetter from which carburetted fuel-air mixture is fed into the cylinder 12 during an intake stroke. An exhaust valve and an exhaust manifold (not shown), being disposed In juxtaposition and adjacent t the intake valve 16 and the intake manifold 18, are also provided to allow exhausted gases to escape from the cylinder 12 during an exhaust stroke.

Although the engine 10 has been illustrated in the drawing as being an inclined engine, it is contemplated that the engine 10 may be of other arrangement.

Furthermore, the intake and exhaust valves have been shown as overhead type, yet it is appreciated that the intake and exhaust valves may be disposed in other position without departing from the scope of the invention.

The engine 10 comprises a number of cylinders 12 each having communication with a branch of the intake manifold 18 and each being covered by a cylinder head 20.

Each of the branches of the intake manifold 18 has a generally S-shaped longitudinal section as shown in Figure 1 and has communication with one another through passageway 26.

An intake port 22 is valved by the inclined intake valve 16 which opens down over the cylinder 12 and -is operated by a valve-operating cam mechanism (not shown). A downstream portion 28 of the intake manifold 18 is adapted to receive secondary air drawn into the intake manifold 18 from a secondary air intake system generally represented by reference numeral 30. Details of the secondary air intake system 30 will now be described.

As shown in Figure 1, the secondary air intake system 30 comprises-an air nozzle 32 incorporated to the cylinder head 20. The air nozzle 32 directs secondary air into the intake manifold 18 in such a manner that the secondary air is positioned at an area immediately adjacent to the intake port 22 of the intake manifold 18 and that the secondary air is stratifily positioned in relation to the carburetted fuel-air mixture within the intake manifold 18.

To accomplish this, the air nozzle 32 is engaged to one end of an extending bore 34 extending through the cylinder head 20. The extending bore 34 has a relatively small dimension as compared with that of the intake manifold 18. One end of the extending bore 34 opens to the downstream portion 28 of the intake manifold 18 while the other end, extending to and termInating at a communication tube 38 integrally provided on the intake manifold 18, opens to the atmosphere.

The air nozzle 32 is so positioned that the nozzle tip 36 of the air nozzle 32 is abutted against and directing the intake air to an inner surface of a generally curved wall at the downstream portion 28 of the intake manifold 18. This renders the intake air to enter smoothly into the intake manifold 18 and replace the fuel mixture without mixing up therewith.

It Is illustrated In Figure 1 that the air nozzles 32 of the respective cylinders 12 are connected by means of the communication tube 38 which is in turn connected to an air filter or cleaner (not shown) to filter the intake air before it enters the inner body of the engine 10. The air nozzle 32 is securely engaged to the cylinder head 20 as depicted in Figure 1 and optionally it may be removably connected to the cylinder head 20 for easy replacement.

Secondary air is drawn through the air nozzle 32 and into the intake manifold 18 of a cylinder 12 by the partial vaccum produced in the course of intaking action of other cylinder or cylinders 12 of the engine 10. Pump means may be provided on the secondary air intake system to facilitate the intake of secondary air into the system.

The air and fuel system for use in the internal combustion engine hereinbefore described characterized in that the air and fuel mixture are adapted to shuttle in two directions within the system in a self-regulating and a well-balance manner. This is quite different from commonly known air and fuel system which usually directs air and fuel mixture to flow in one direction. This counter-flow air and fuel system is best coupled to an internal combustion engine of counter-flow type.

According to the air and fuel system of the internal combustion engine of the present invention, the intake valve 16 is closed when secondary air enters the intake manifold 18 and is open during the intake operation of the cylinder 12. A partial vaccum is created as the piston 14 moves downward thereby drawing the air and fuel mixture into the cylinder 12. The secondary air immediately adjacent to the intake port 22 enters the cylinder 12 first following by the carburetted fuel-air mixture.

The secondary air enters the cylinder 12 and is positioned at the bottom portion of the combustion chamber 24 right on top of the piston head. Whereas, the carburetted fuel-air mixture which has been shuffled to the direction away from the cylinder 12 now moves towards and enters the cylinder 12 and is positioned substantially at the top portion of the combustion chamber 24 right underneath the cylinder head 20 where a spark plug (not shown) is located.

This introduction of secondary air in stratified form gives rise to a higher charge density which results in a higher compression ratio and engine efficiency.

Combustion takes place when the fuel mixture positioned underneath the cylinder head 20 is ignited by the spark plug. The burning gas then mixes with the secondary air which is positioned above the piston head and which is served to complete the combustion process so that nearly all of the intake fuel is burnt during combustion. This leads to a more complete combustion and results therefore In cleaner engine as well as higher- engine performance.

Figure 2 is a similar sectional view of the four-stroke cycle engine of Figure 1 showing a second embodiment of the secondary air intake system embodying the invention. The construction of the engine is basically equivalent to that of Figure 1 in which like reference numerals with addition of a prime representing like parts.

The engine 10' is provided with a secondary air intake system generally indicated by reference numeral 40.

This secondary air intake system 40 comprises an air nozzle 42 having a hold down screw 94 at one end and a nozzle tip 46 at the other end directing secondary air to a downstream portion 28' of the intake manifold 18'.

The tubular body 48 of the air nozzle 42 has communication with a communication tube 50 through an opening 49. The communication tube 50 connects the air nozzles 42 of the respective cylinders 12' of the engine 10' and opens to the atmosphere. Similarly, an air cleaner or filter is connected to the communication tube 50 to filter the intake air. The intake air enters the intake manifold 18' through the air nozzle 42.

Although the secondary air intake system 40 has been shown, according to the present embodiment, as being incorporated to an end portion of the branches of the intake manifold 18', it is'appreciated that the secondary air intake system 40 may be incorporated to the cylinder head 20'..

The principle of stratified charge internal combustion engine hereinbefore disclosed may also apply to two-stroke cycle engines. This application will now be described in detail with reference to Figures 3 and 4 of the accompanying drawings.

Referring to Figure 3, reference numeral 110 generally represents a two-stroke cycle engine. This twostroke cycle engine 110 includes as in conventional a cylinder 112, a piston 114, an intake port or passage 116, an exhaust port or passage 118 and a transfer canal 120 to transfer air and fuel mixture from a crankcase 150 to the cylinder 112. In addition, a secondary air intake system generally indicated by reference numeral 122 is provided on the engine 110. The secondary air intake system 122 comprises an air chamber 124 integrally provided on the side wall 130 of the engine 110 adjacent to the transfer canal 120. Air chamber 124 communicates with the transfer canal 120 through an orifice 126 which directs intake air to flow from the air chamber 124 toward one end of the transfer canal 120 remote from the crankcase 150.The flow of air through the orifice 126 can be controlled by adjusting screw or valve means (not shown). Secondary air enters the air passage 124 through an air inlet 138 which is valved by a springy reed valve or a leaf valve 140.

A low pressure or partial vaccum is created within the crankcase 150 when the piston 114 moves to the top of the cylinder 112 as illustrated in Figure 3. The greater atmospheric pressure outside rushes through a carburetter (not shown) drawing fuel-air mixture into the crankcase 150 through the intake passage 116 as indicated by crosses in Figure 3. At the same time, atmospheric pressure rushes into the secondary air intake system 122, pushing open the leaf valve 140, filling the air chamber 124 with secondary air. The secondary air further enters the transfer canal 120 through the orifice 126, substantially filling up the transfer canal 120 as indicated by dots in Figure 3, pushing the fuel-air mixture backward into the crankcase 150.

According to the present air and fuel intake arrangement, carburetted fuel-air mixture enters and occupies the crankcase 150 from one side of the engine 110 whilst the secondary air enters and occupies the transfer canal 120 from an opposite side of the engine 110 in such a manner that the secondary air and carburetted fuel-air mixture are separately positioned.

As the piston 114 moves downward to a position as shown in Figure 4 during an power/intake stroke, the secondary air is forced into the combustion chamber 148 first and is positioned at a far side from the intake port 128 of the transfer canal 120 as represented by dots in Figure 4. The carburetted fuel-air mixture within the crankcase 150 is then forced into the combustion chamber 148 through the transfer canal 120 and is positioned at a vicinity to the intake port 128 of the transfer canal 120 as indicated by crosses in Figure 4.

The secondary air is positioned generally at a central area of the combustion chamber 148 separating the fuel-air mixture and the undischarged exhausted gases. The secondary air serves the purpose of diluting the undischarged exhausted gases.

When the piston 114 moves upward during an exhaust/compression stroke, the gases within the combustion chamber 148 are compressed so that the fuel-air mixture is positioned in a region of a spark plug. This compression stage is shown in Figure 3.

Similar to a four-stroke cycle engine, combustion of a two-stroke cycle engine takes place when the compressed fuel-air mixture is ignited by the spark plug.

The burning gas then mixes with the secondary air which helps to complete the combustion process so that nearly all of the intake fuel is burnt during the combustion.

Exhausted gases escape from the cylinder 112 through the exhaust passage 118 which becomes uncovered when the piston 114 moves downward. A portion of the exhausted gases, being represented by primes in Figure 3, remains in the cylinder 112 at an area adjacent to the exhaust passage 118.

Although the two-stroke cycle engine has been illustrated as in a common construction, it is understood by one skilled in the art that the two-stroke cycle engine may be of other constructions. For example, the intake port or passage for thelcarburetted fuel-air mixture may be disposed at the bottom end of the crankcase.

It is appreciated that the four-stroke cycle and the two-stroke cycle engines above-mentioned for producing stratification of air and fuel mixture within a combustion chamber are exceedingly simple in structure. Since no complicated valves or passages or extra parts are employed, the manufacturing cost of the engines of the present invention is comparatively low.

The stratified charge engine of the present invention is designed to perform most efficiently under partial load condition. In view of the fact that most of our daily operating vehicles work 90% of their lifetime under partial load condition, the engine disclosed hereinbefore is believed to be a remarkable engine having the results of improving . combustion, Increasing compression ratio and enhancing the possibilities for making the reciprocating engine cleaner and more efficient.

Claims

1. An air and fuel system for use in an internal combustion engine having a secondary air intake system, whe re i n an intake valve or port of an air and fuel intake passage of a cylinder of the engine is closed when secondary air is being drawn into the downstream of the intake passage of said cylinder through. the secondary air intake system replacing the carburetted fuel-air mixture which is being drawn backward in a direction away from the cylinder by suction or intake operation of the engine thereby forming a fresh stratified charge at the downstream of the intake passage which is to be drawn into said cylinder during the following intake operation, and wherein during the intake of the stratified charge the first intake portion of the charge consisting mostly of secondary air from the secondary air intake system is generally positioned in a region directly on top of the piston head whilst the last intake portion of the stratified charge consisting mostly of carburetted fuel-air mixture is generally positioned in an area adjacent to the cylinder head where a spark plug is located.

2. An air and fuel system as claimed in claim 1, wherein said air and fuel intake passage defines a channel along which air and fuel mixture are shuttling in both directions during the operation of the engine.

3. An air and fuel system as claimed In claims 1 or 2, where In at least a portion of said air and fuel intake passage further defines a storing chamber for temporary storage of secondary air from the secondary air intake system.

4. An air and fuel system as claimed in claims 1 to 3, wherein said engine is a four-stroke cycle engine.

5. An air and fuel system as claimed in claims 1 to 3, wherein said engine is a two-stroke cycle engine.

6. An air and fuel system as claimed in claims 1 to 4, wherein the secondary air intake system comprises an air nozzle incorporated to the cylinder for directing secondary air to a downstream end portion of said intake passage adjacent to the intake port thereof.

7. An air and fuel system as claimed in claim 6, wherein said air nozzle is provided with metering or adjusting means for regulating the flow of intake air.

8. An air and fuel system as claimed in claims 1 or 2, wherein the secondary air is drawn into the intake passage of a cylinder by means of partial vaccum produced in the course of intake operation of other cylinder or cylinders of the engine.

9. An air and fuel system as claimed in claims 1 to 3 and claim 5, wherein said air and fuel intake passage defines a transfer canal within the engine for the transfer of air and fuel mixture from a crankcase to a cylinder of the engine.

10. An air and fuel system as claimed in claims 1 to 3, claim 5 and claim 9, wherein the secondary air intake system comprises an air chamber having communication with said air and fuel intake passage through an orifice provided on a side wall of the engine, and an air inlet being provided on said air chamber generally at an opposite side to said orifice, said air inlet being valved by a leaf valve through which secondary air enters.

11. An air and fuel system as claimed in claims 1 to 10, wherein the secondary air intake system is connected to a filter means for filtering the intake air.

12. An internal combustion engine having a secondary air intake system comprising: an intake passage for the intake of carburetted fuel-alr mixture into a cylinder of the engine, said intake passage defines a channel along which air and fuel mixture are shuttling in both directions during operation of the engine, and at least a portion of said intake passage further defines a storing chamber for temporary storage of secondary air from the secondary air intake system, and an air intake means for the intake of secondary air Into said intake passage at a downstream end portion thereof, said air intake means opening at one end to the downstream of said intake passage and at the other end to the atmosphere, where In the intake valve of said intake passage of the cylinder is closed when secondary air is being drawn into the downstream of said intake passage of the cylinder through the secondary air intake system replacing the carburetted fuel-air mixture which is being drawn backward in a direction away from the cylinder by the intake operation of the cylinder or cylinders of the engine thereby forming a fresh stratified charge at the downstream of the intake passage which is to be drawn into said cylinder during the following intake operation, and wherein during the intake of the stratified charge the first intake portion of the charge consisting mostly of secondary air from the secondary air intake system is generally positioned in a region directly on top of the piston head whilst the last intake portion of the stratified charge consisting mostly- of carburetted fuel-air mixture is generally positioned in an area adjacent the cylinder head where a spark plug is located.

13. An internal combustion engine as claimed in claim 12, wherein said air intake means is in the form of an air nozzle.

14. An internal combustion engine as claimed in claim 13, where In said air nozzle is incorporated to the cylinder head of the cylinder.

15. An internal combustion engine as claimed in claim 13, wherein said air nozzle is incorporated to the intake manifold of the engine at an immediate vicinity to the cylinder head.

16. An internal combustion engine as claimed in claims 13 to 15, wherein said air nozzle Is provided with metering or adjusting means for regulating the flow of intake air.

17. An internal combustion engine as claimed in claims 12 and 13, wherein the air intake means of respective cylinders are connected to one another by means of a communication tube.

18. An Internal combustion engine as claimed In claims 12 to 17, wherein the air intake means are connected to a filter means for filtering the intake air.

19. An internal combustion engine having a secondary air intake system comprising: a transfer passage for the transfer of carburetted fuel-air mixture from a crankcase into a cylinder of the engine, said transfer passage defines a channel along which air and fuel mixture are shuttling in both directions during the operation of the engine and at least a portion of said transfer passage further defines a storing chamber for temporary storage of secondary air from the secondary air intake system, an air chamber having communication with said transfer passage through an orifice provided on a side wall of the engine, and an air inlet being provided on said air chamber generally at an opposite side to said orifice, said air inlet being valved by a leaf valve through which secondary air may enter, wherein the intake port of said transfer passage is closed when secondary air is being drawn into said transfer passage through said orifice replacing the carburetted fuel-air mixture which is being drawn backward into the crankcase of the engine thereby forming a fresh stratified charge to be drawn into the; cylinder during the following intake operation, and wherein during the intake of the stratified charge the first intake portion of the charge consisting mostly of secondary air from the secondary air intake system is generally positioned at a far side from the intake port of said tranfer passage whilst the last portion of the charge consisting mostly of carburetted fuel-air mixture is generally positioned at a vicinity to the intake port of said transfer passage.

20. An internal combustion engine as claimed in claim 19, wherein a valve means is operatively engaged to said orifice for regulating the flow of intake air.

21. An internal combustion engine as claimed in claim 19, wherein said air chamber Is connected to a filter means for filtering the intake air.

22. An air and fuel system for use in an internal combustion engine of the type substantially as hereinbefbre described with reference to and as illustrated in the accompanying drawings.

23. An internal combustion engine substantially as hereinbefore described with reference t-e and as illustrated in Figures 1 and 2 of the accompanying drawings.

24. An internal combustion engine substantially as hereinbefore described with reference to and as illustrated in Figures 3 and 4 of the accompanying drawings.