GB2210665A

GB2210665A - Engine intake system

Info

Publication number: GB2210665A
Application number: GB8723584A
Authority: GB
Inventors: Keith Gordon Hall
Original assignee: Individual
Current assignee: Individual
Priority date: 1987-10-07
Filing date: 1987-10-07
Publication date: 1989-06-14
Anticipated expiration: 2007-10-07
Also published as: GB8723584D0; GB2210665B

Abstract

An internal combustion engine comprises two or more cylinders in which the air intake pipes to each cylinder 13, 14 consist of one or more pairs 2, 8; 3, 9 of inner pipes 8, 9 and outer pipes 2, 3 whose junctions are attached to a connecting valve or valves 7 whose operation permits air flow between the junctions. The intake pipes to the cylinders not in the induction phase form a volume reservoir for the intake pipe to the cylinder in its induction phase. Preferably the air intake pipes form a cluster around the connecting valve Figs. 3a, 3b. The volume reservoir formed by the combination of the intake pipes may be augmented by inclusion of the central space inside the cluster and additional external volume. The order of attachment of the intake pipes to the connecting valve is such that air flow direction reversals are avoided in the intake system. <IMAGE>

Description

ENGINE INTAKE SYSTEM This invention relates to air intake systems for internal combustion,sengines and a method of controlling them.

The design of the air intake system influences the breathing of an internal combustion engine and thus engine performance. There are two important parameters within the tuned intake pipe that influence the engine's breathing; (a) the inertia of the a.ir stream, and (b) the acoustic waves within the air stream. When both parameters are optimised a supercharge effect is achieved.

Conventional engines with fixed valve timing and fixed geometry intakes can only achieve this supercharge effect over a minor part of the engine speed range. in order to extend the range of the supercharge effect either the valve timing or the intake system geometry should be automatically variable There are two types of variable geometry air intake systems (1) continuously variable and (2) incrementally variable.

Incrementally variable geometry intake systems function by changing from one tuned pipe length to another. To effect this change in length the intake pipe must be interupted at the appropriate short length and a connection made to a volume reservoir. Proposed methods to achieve variable geometry systems have involved the use of either the original volume reservoir (plenum chamber) or a secondary plenum chamber. Systems of this nature are described in GS A 2 121 473 which take up a considerable amount of engine volume. This invention is concerned with a simple compact incrementally variable intake system.

An object of the invention is to provide a compact high inertia intake system achieving near optimum engine breathing over most of the engine's speed range even though the valve timing remains fixed.

Another object is to provide an air intake system whose performance is equivalent to a modestly supercharged engine achieving high torquf high power, lower specific fuel consumption and the potential to attain higher engine speeds.

A further object of the invention is to prevent flow reversals taking place in the air intake system.

According to the invention there is provided an internal combustion engine having two or more cylinders, characterised in that the air intake pipes to each cylinder consist of two or more pairs of inner and outer pipes whose junctions are attached to a connecting valve or valves whose operation permits air flow between the junctions.

A novel feature of this invention is that the intake pipes to the other cylinders become the volume reservoir for the intake pipe for the cylinder undergoing its induction phase Hence. a simpler more compact incrementally variable intake system is achieved with the potential of optimising engine breathing throughout the speed range.

In a preferred embodiment the air intake pipes form a cluster around the connecting valve. The volume reservoir formed by the combination of the intake pipes may be augmented by inclusion of the central space inside the cluster and additional external volume.

In order that the invention may be clearly understood it will now be described with reference to the accompanying drawings in which: Figure 1 is a schematic diagram of an air intake system according to the invention for two cylinders, Figure 2 is a schematic diagram of an air intake system according to the invention adapted for four cylinders, Figure 3. a and b, is a vertical cross sectional view of a two-positional air switching valve for use with the air intake system shown in Figure 2, Figure 4 is a horizontal cross sectional view of the two positional air switching valve shown in Figure 3, and Figure 5 is a schematic diagram. of an air intake system according to the invention adapted for five cylinders.

An incrementally variable geometry air intake system for two cylinders. see Figure 1. consists of two pairs of inner and outer pipes. An outer pipe 2 and an inner pipe 8 supply cylinder 13. A second pair of pipes consisting of an outer pipe 3 and an inner pipe 9 supply cylinder 14.

The junction between the pipes 2 and 8 is connected to one entry port of a connecting valve 7 and the junction between the pipes 3 and 9 to the other entry port of the valve 7.

The valve is shown as a simple on/off solenoid operated valve with linear motion.

At low engine speeds the valve 7 is closed and each pair of pipes. 2/8 and 3/9, functions as a long individual pipe with tuned lengths of pipe 2 together with 8 and pipe 3 together with 9 respectively. At high engine speeds the valve 7 is opened allowing flow through it between the junctions of the pairs of pipes 2/8 and 3/9. Providing the volume made available is large enough to achieve sufficient damping between pipes 2 and 8 and pipes 3 and 9.

the tuned pipe length will now be that of pipe 8 for cylinder 13 and pipe 9 for cylinder 14. The direction of flow through through the valve 7 connecting the junctions 4 and 6 will aiternate according to which cylinder is sucking.

A schematic arrangement of an engine 17 having four cylinders 13. 14. 15 and 16. see Figure 2. uses a single connecting valve 7 to achieve an incrementally variable geometry air intake system.

Theconnecting valve may have a linear or rotary motion or a combination of both. The valve is so configured that its ports are arranged in a cluster in order to minimise the installation bulk of the air intake system.

A group of four pairs of pipes run from an air cleaner plenum chamber 1 to the cylinders 13. 14. 15 and 16.

Upper pipes 2 and 3 join pipes 8 and 9 respectively connected to the cylinders 13 and 14. Lower pipes 4 and 5. concealed by the upper pipes in the diagram. join pipes 10 and 11 respectively connected to the cylinders 15 and 16. The junctions between each pair of pipes are connected to a rotary sleeve connecting valve 7 and form a cluster around it.

The connecting valve 7. see Figures 3a. 3b and 4, consists of a body 21 and a rotor 18 which is attached to a rotor sleeve 19. A bearing 26 provides radial and axial location for the rotor 18. The valve carries four ports 22. 23. 24 and 25 which are closed when the rotor sleeve 19 is in its first position. see Figure 3a, and open when the rotor sleeve 19 is in its second position. see Figure 3b allowing entry to a central space 27. The upper portion of the space 27 is shown closed by an optional wall 28 between it and the centre section 29 of the cluster of pipes. The ports 22. 23. 24 and 25 act as the junctions between the pipe pairs 2/8. 3/9. 4/10 and 5/11 respectively.

When the connecting valve 7 is closed air flows to each cylinder 13. 14. 15 and 16 through its respective pairs of pipes. 2/8. 3/9. 4/10 and 5/11 and the ports 22. 23. 24 and 25 joining them. The rotor 18 prevents any flow from the between the pipe pairs. Hence in this configuration long intake pipes of large volume may be used to optimise engine performance at low speeds.

Turning the rotor 18 to the open position. see Figure 3b.

the ports 22. 23. 24 and 25 are connected to the central space 27 within the valve. Hence the intake pipe undergoing induction. exemplified by 10. see Figure 4, draws air from the other intake pipes. Additional flow may be drawn through the centre section 29 of the cluster of outer pipes 2. 3. 4. 5 by eliminating the optional wall 28. In principle the introduction of a reservoir volume partway along the original intake pipe shortens the tuned length and reduces the volume of the tuned length. This enables the high speed engine performance to be optimised.

Moreover. as all the outer pipes 2, 3, 4. 5 now feed each inner pipe during the induction then the outer flow area has effectively been increased and flow losses from pipe friction thus reduced.

Interference between pipes with overlapping induction periods reduces cylinder filling below a critical speed which is dependant on the length of the path between the interfering cylinders and the speed of sound in the airstream. Once above this critical speed the connecting valve 7 can be opened without detriment to cylinder filling. In fact when the engine valve timing is optimised for medium or low speeds then at high speeds the inlet valve closes too soon and a pressure head builds up in the intake pipe behind the closed inlet valve. This pressure head may then be used by the following cylinder.

Additionally. the positioned ports 22. 23. 24. 25 (figure 3a/3b) enable the inner intake pipes 8. 9 10. 11 to be connected to the connecting valve body 21 in the sequence that is the same as the engine firing order.

Hence. when the connecting valve 7 is open (figure 3b) flow passes through the central space 27 with a continuous corkscrew swirling motion (clockwise in this example).

Hence. flow reversals are eliminated and cylinder filling further enhanced. The connecting valve rotor may be moved between its two positions either quickly or progressively dependant on engine characteristics.

Theoretically it can be shown that for a given engine valve timing a performance window for optimum engine breathing exists that is dependent on an inertia ram parameter and a wave ram parameter. The geometry of the intake system can be so arranged as to combine the inertia ram peak with the first. third and fifth harmonics of the wave ram resonances. all within the optimum performance window.

First of all for the low speed range (long pipes. valve closed) and secondly for the high speed range (short pipes.

valve open). An additional connecting valve would endow an engine with three speed ranges of optimum breathing.

An air intake system according to the invention adapted for five cylinders. see Figure 5. uses a connecting valve 7 in which inner pipes 8. 9. 10. ii and 12 are connected around the body of the valve 7 in a sequence according to the engine s firing order. Five individual outer pipes 2. 3.

4. 5 and 6 feed air from the air cleaner plenum chamber 1 to the connecting valve 7. The inner pipes are depicted passing over the cylinder head of the engine. The set of pipes forms a cluster around the valve body to minimise the volume taken up by the system.

A typical system for a six cylinder engine may comprise a single cluster of six pipes or two separate clusters of three pipes. each with their associated connecting valve.

In principle the number of ports in the connecting valve may be further reduced by pairing together non-interfering inner pipes in order to further reduce the size of the intake system. However. some negative acoustic waves would be introduced from the closed pipes1 thus diminishing the overall gains in engine breathing.

The practical high inertia intake system according to the invention enhances an engine's idling performance (a critical legislative requirement) while maintaining an adequate valve timing period necessary for maximum engine power.

The air intake system according to the invention has been illustrated without reference to the fuel supply. The embodiments shown are suitable for use with a spark ignited petrol engine using fuel injection or with a diesel engine.

The long pipe lengths involved are unsatisfactory for use with a single carburetter. However the system could be used satisfactorily for the air intakes of a multi-point carburation system.

The invention has been described with respect to four stroke engines but it may equally be applied to two stroke engines. As illustrated the air intake system is shown supplied from the air cleaner plenum chamber in an engine.

In the case of very high performance engines the air may be supplied by a turbo-supercharger.

The invention has been described in detail with particular reference to preferred embodiments thereof. but'it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

Claims

1. An internal combustion engine having two or more cylinders."characterised in that the air intake pipes to each cylinder consist of two or more pairs of inner and outer pipes whose junctions are attached to a connecting valve or valves whose operation permits air flow between the junctions.

2. An internal combustion engine according to claim 1.

characterised in that the connecting valve and outer pipes form an air reservoir without the necessity for a separate plenum chamber when the valve is open.

3. An internal combustion engine according to claims 1 or 2. characterised in that the pairs of pipes themselves become. between their induction periods. the volume reservoir for the intake pipe undergoing its induction period.

4. An internal combustion engine according to any of the preceding claims. characterised in that the engine has at least three cylinders and the outer pipes form a cluster.

5. An internal combustion engine according to claim 4.

characterised in that the engine has four cylinders and the outer pipes form a cluster.

6. An internal combustion engine as claimed in claim 4 or claim 5. characterised in that the centre section of the pipe cluster is associated with the connecting valve and forms part of the air reservoir when the valve is open.

7. An internal combustion engine according to any of the preceding claims. characterised in that the order of attachment of the intake pipes to the connecting valve is so arranged that air flow direction reversals are eliminated in the intake system.

8. An internal combustion engine according to any of the preceding claims. characterised in that the combination of the connecting valve and intake pipe geometries integrate the inertia ram peak and the multiple wave ram peaks together whereby optimum engine breathing is maintained over the major part of the engine speed range.

9. An internal combustion engine according to any of the preceding claims. characterised in that the connecting valve is a sleeve valve.

10. Internal combustion engines according to claim 1 and as herein described.