GB2321671A

GB2321671A - I.c. engine inlet manifold with branches of equal length

Info

Publication number: GB2321671A
Application number: GB9719360A
Authority: GB
Inventors: Micheal Crowson
Original assignee: Perkins Ltd
Current assignee: Perkins Ltd
Priority date: 1997-01-31
Filing date: 1997-09-11
Publication date: 1998-08-05
Anticipated expiration: 2017-09-11
Also published as: GB9702028D0; GB2321671A8; GB9719360D0; GB2321671B

Abstract

An inlet manifold 12 for a three-cylinder internal combustion engine has a common inlet spout 22 which is segmentally divided to provide respective inlet ports for three tracts 1,2,3 communicating with respective engine intake ports 16,18,20. The central tract 2 is arched over or under the two outer tracts 1,3 in order to provide the central tract 2 with a length generally equal to the lengths of the two outer tracts which each extend sideways away from the inlet spout 22. The length of the central tract 2 is therefore increased to equal that of the other tracts but in a manner which does not adversely affect fluid flow through said tract. The mouth of the inlet spout 22 may be directed away from the side of the engine to which the manifold is attached. The invention can be applied to engines with a multiple of three cylinders, eg with in-line or Vee six-cylinder engines and to engines with four, or multiples of four, cylinders. In a four-cylinder engine, the two central tracts are arched over the two outer tracts.

Description

1 2321671 An Inlet Manifold For An Internal Combustion Engine The present

invention relates to an air or air/fuel inlet manifold for an internal combustion (i.c.) engine and, in particular, to an inlet manifold for an i.c. engine having three cylinders or multiples thereof.

In compression-ignition and spark-ignition i.c. engines having three cylinders, it can be desirable to feed the combustion chambers with air or an air/fuel mix via a branched inlet manifold having a single inlet port and three outlet ports. This can provide both economy of installation and manufacture and an improved engine envelope, which would be advantageous when mounting the engine in the available space of an engine bay, when compared with an engine including an inlet manifold having three separate inlet ports and three outlet ports. A three-branched inlet manifold as aforesaid may also be used on engines having multiples of three cylinders, such as in-line or vee-type six cylinder engines, where each block of three cylinders may be fed via a respective inlet manifold having a single inlet port.

A disadvantage of an inlet manifold having one common inlet port and three outlet ports is that a central tract connecting the inlet port to a central outlet port will generally be shorter than the outer tracts on either side thereof. This will lead to imbalances in gas velocities in the various tracts and hence in-cylinder filling, resulting in imbalances in power production and a loss of smoothness of running between the cylinders of the engine.

2 Such imbalances may also be detrimental to engine exhaust emissions and specific fuel consumption.

To avoid the abovementioned imbalance problem, it is known for a central inlet tract to be deliberately lengthened to provide a roughly equivalent length to the outer tracts, but the resultant contortion of the central tract, necessary in order to accommodate it between the manifold inlet port and the respective engine cylinder inlet port, will compromise fluid flow efficiency.

Contortion of the central tract can also complicate the manufacture of the manifold, so making it more expensive to produce, and the routing of the tract may obstruct access to manifold fasteners or other engine components which might otherwise be accessed between the branches of the manifold.

It is an object of the present invention to provide a multi-branch air or air/fuel inlet manifold for an i.c. engine that provides tracts of generally equal length and of generally equal cross-sectional area over their lengths in a manner which has a minimal deleterious effect on fluid flow characteristics and inlet manifold manufacturing costs and which limits the obscuration of manifold fasteners or other local engine components.

According to a first aspect of the present invention, there is provided an inlet manifold for an i.c. engine comprising an inlet spout, at least three tracts of substantially equal length, each tract communicating between the inlet spout and a respective one of an equal 3 number to the tracts of generally coplanar outlet ports, inlet spout being segmentally divided to provide respective inlet ports for said tracts wherein a portion of at least one of said tracts is arched with respect to at least two of the other tracts and said inlet spout and at least part of each of said two other tracts are angled away from said arched tract.

According to a second aspect of the present invention, there is provided an i.c. engine including an inlet manifold in accordance with the first aspect of the invention.

According to a third aspect of the present invention, there is provided an internal combustion engine including an inlet manifold comprising an inlet spout, at least three tracts of substantially equal length, each tract communicating between the inlet spout and a respective one of an equal number to the tracts of generally coplanar outlet ports, a portion of at least one of said tracts being arched with respect to at least two of the other tracts and said inlet spout and at least part of each of said two other tracts being angled away from said arched tract, wherein the outlet ports of the manifold abut engine inlet ports on a side of the engine and the manifold is arranged such that a mouth of the inlet spout is generally directed away from said side of the engine and the tracts are substantially accommodated in a space between the inlet spout and the side of the engine.

Further features of the present invention are as 4 defined in the appended claims.

The foregoing and further features of the present invention will be more readily understood from the following description of preferred embodiments, by way of example thereof, with reference to the accompanying drawings of which:- Figure 1 is a crosssectional plan elevation of a known unbalanced three branch inlet manifold for an i.c. engine; Figure 2 is a cross-sectional plan elevation of a known balanced three branch inlet manifold; Figure 3 is a cross-sectional plan elevation of the balanced three branch inlet manifold in accordance with a f irst embodiment of the present invention, representing section C-C of figure 4; Figure 4 is a cross-sectional front elevation of the inlet manifold in accordance with the first embodiment of the present invention, representing section A-A of figures 3 and 5; Figure 5 is a cross-sectional side elevation of the manifold in accordance with the first embodiment of the present invention, representing section B-B of figure 4; Figure 6 is a section through the leading edge of each inlet tract, typified by section D-D of figure 5; and Figure 7 is a side elevation of an inlet manifold similar to that shown in figures 3 to 5 but having a downwardly directed inlet in accordance with a second embodiment of the present invention.

Referring to the drawings, figure 1 shows a sectional plan view of a three branched inlet manifold 4 of known type, wherein the lengths of the tracts 6 are not balanced and therefore the flow of air or air/fuel mix into the engine cylinders (not shown) is also unbalanced leading, as described above, to probable deleterious effects on power production, smoothness of engine operation, engine exhaust emissions and specific fuel consumption.

Figure 2 shows a sectional plan view of a three branched inlet manifold 8 of known type, wherein the tracts 10 are of generally equal length and therefore provide a better balance of air or air/fuel mix flow into the engine cylinders (not shown). The necessary extra length of the central tract has, in this example, been contained relatively compactly by configuring the tract as a tight S' form. Allowance has to be made, however, for the obstruction to flow by the tight bends of the central tract. It can also be envisaged that the central tract may well obstruct access to manifold securing fasteners (not shown) or to other local engine components (not shown).

Rather than a tight IS' form, the central tract of the known inlet manifold of figure 2 could be more gently curved, but this would necessarily increase the room needed to accommodate it and the characteristics of fluid flowing through said tract would still be compromised to an extent which may not be acceptable. Further, a gently curved central tract, in necessarily extending outside of 6 a tight engine envelope, would complicate manufacture of the manifold.

Figure 3 shows a cross-sectional plan view through a three branched inlet manifold 12 in accordance with a first embodiment of the present invention, said manifold 12 being attached to a cylinder head 14 of an engine having three inlet ports (16, 18, 20). Figures 4, 5 and 6 show further sections through the manifold 12 of the first embodiment. The invention will be understood from the following description with particular reference to figures 3, 4 and 5 in which, for ease of reference, the manifold tracts have been numbered 1, 2, 3 respectively to represent the engine cylinders (not shown) to be fed with air or an air/fuel mix, the central numbered 2.

cylinder being The inlet manifold 12 commences with an inlet spout 22 designed to accept a conventional rubber hose connection (not shown). The spout 22 has an internal cross-sectional area generally equivalent to the sum of the cross-sectional areas of all three engine inlet ports (16, 18, 20). Three independent tracts (1, 2, 3) communicate between the spout 22 and the engine inlet ports, the tracts commencing as three equal segments within the inlet spout 22 and being of equal length. The interior of the inlet spout 22 is divided segmentally by partitions 23 which between them define respective inlet ports 25 for the three tracts (1,2,3). The inlet ports 25 lie in the same plane within the inlet spout 22. When the 7 inlet manifold 12 is attached to the engine cylinder head 14, the manifold outlet ports (24, 26, 28), which lie in the same plane, abut respectively the engine inlet ports (16, 18, 20). Gasket means (not shown) may be provided at the interface between the manifold 12 and the cylinder head 14 to ensure a gas-tight seal. Equivalence in length of the tracts (1, 2, 3) is achieved by running the central tract 2 above the outer tracts (1, 3) and angling the spout 22 and a first part 30 of all three tracts (1, 2, 3) over a calculated angle 1Y1 (see figure 5), thus extending the length of the central tract 2. In the given example, angle 1Y1 is 600, but may be more or less than this depending mainly upon the spacing between the central port 18 and the outer ports (16, 20) of the engine cylinder head 14.

All three tracts (1, 2, 3) have an equal crosssectional area over their full length with a gradual change from a nominally segmental (triangular) section to a nominally rectangular section over length 'X' (see figure 5), this extending from cutting plane 'A-A' shown in figure 5 to the faces of the manifold 12 where the tracts (1, 2, 3) are brought into communication with the engine inlet ports (16, 18, 20). The engine inlet ports should, as conventionally practiced, be balanced so as to maintain even gas flows.

Figure 6 shows the shape of the leading edges 32 of the partitions 23 separating the inlet tracts (1, 2, 3), typically positioned as shown at section D-D of figure 5.

8 The leading edges 32 are all configured to be flow assisting,.

Figure 7 shows a side elevation of an inlet manifold 12 for an i.c. engine in accordance with a second 5 embodiment of the present invention, where the inlet spout 22 is nominally angled 600 downwards rather than upward as in the first embodiment. This is achieved by inverting the tracts (1, 2, 3) so that the central tract 2 arches below the outer tracts (1, 3).

The inlet manifold 12 is preferably formed by casting from a suitable metal or by injection moulding from a suitable plastics material. These processes generally have a cost advantage over metal fabrication for the manufacture of inlet manifolds in mass production quantities. The arrangement of the tracts comprising the manifold 12 is designed such that it presents no particular problems in a metal casting or plastics moulding process.

In a preferred arrangement as depicted in figure 3, the inlet manifold 12 is arranged such that a mouth 33 of the inlet spout is directed generally away from a side of the engine block 14 to which the manifold 12 attaches with the tracts (1,2,3) being substantially accommodated in a space between the inlet spout 22 and the side of the cylinder head 14. This arrangement has the advantage of maintaining the engine envelope size to a minimum whilst achieving the other objects of the invention.

It is envisaged that an inlet manifold for an i.c.

9 engine could be constructed in accordance with the present invention for fitting to a three cylinder engine or for fitting to other engines having multiples of three cylinders. For example, two such inlet manifolds could be 5 fitted to an in-line or a vee-type six cylinder engine. For a vee-type engine, the two such manifolds could be fitted so that their inlet spouts are adjacent to one another or they could be formed as a single unit (not shown) to bridge the valley between the two engine cylinder banks (not shown).

It is also envisaged that an inlet manifold for an i.c. engine could be constructed in accordance with the present invention for fitting to a four cylinder engine or for fitting to other engines having multiples of four cylinders. In such a case, each of the two central tracts of the manifold could be arched over the two outer tracts to provide all tracts with a generally equal length. The central tracts would also be angled outwardly sideways away from the inlet spout in a similar manner to the outer tracts but to a lesser degree.

Claims

1 An inlet manifold for an i.c. engine comprising an inlet spout, at least three tracts of substantially equal length, each tract communicating between the inlet spout and a respective one of an equal number to the tracts of generally coplanar outlet ports, said inlet spout being segmentally divided to provide respective inlet ports for said tracts, wherein a portion of at least one of said tracts is arched with respect to at least two of the other tracts and said inlet spout and at least part of each of said two other tracts are angled away from said arched tract.

2. An inlet manifold as claimed in claim 1, wherein internal partitions in the inlet spout segmentally divide it to provide the inlet ports to the tracts.

3. An inlet manifold as claimed in claim 1 or claim 2, wherein the inlet ports to the tracts are generally coplanar.

4. An inlet manifold as claimed in any one of claims 1 to 3, wherein the cross-sectional shape of each tract shape of its claims process 6. claim, changes gradually from a substantially segmented to a substantially rectangular shape over a portion length.

An inlet manifold as claimed in any one of 1 to 4, wherein the manifold is formed by a casting or an injection moulding process.

An inlet manifold as claimed in any preceding wherein the manifold is arranged such that a mouth 11 of the inlet spout, in use, is generally directed away from a side of the engine to which the manifold attaches and the tracts are substantially accommodated in a space between the inlet spout and said side of the engine.

7. An inlet manifold as claimed in any one of claims 2 to 6, wherein leading edge of the internal partitions are shaped so as to be flow assistingwith respect to air flowing through the inlet spout.

8. An inlet manifold as claimed in any one of claims 1 to 7, wherein said portion of said at least one tract arches over said two other tracts and said inlet spout is angled downwards with respect to said outlet ports.

9. An inlet manifold as claimed in any one of claims 1 to 7, wherein said portion of said at least one tract arches under said two other tracts and said inlet spout is angled upwards with respect to said outlet ports.

10. An inlet manifold as claimed in any one of claims 1 to 9, wherein the arched tract communicates between the inlet spout and the central outlet port.

11. An inlet manifold as claimed in any preceding claim, wherein the angle through which the inlet spout is disposed relative to the outlet ports is calculated so as to increase the length of the arched tract to equal that of the other tracts.

12. An inlet wherein the angle disposed relative manifold as claimed in claim 11, through which the inlet spout is to the outlet ports is at least 12 partially dependent upon the spacing between the outlet ports.

13. An inlet manifold as claimed in any preceding claim, wherein the inlet spout is substantially circular in cross section and the outlet ports are substantially rectangular in cross section.

14. An inlet manifold as claimed in any preceding claim, wherein the internal cross section of the inlet spout is generally equal to the sum of the cross-sectional 10 areas of the outlet ports.

15. An inlet manifold as claimed in any preceding claim, wherein each tract has an equal cross sectional area along its entire length.

16. An i.c. engine including an inlet manifold in 15 accordance with any one of claims 1 to 15.

17. An internal combustion engine including an inlet manifold comprising an inlet spout, at least three tracts of substantially equal length, each tract communicating between the inlet spout and a respective one of an equal number to the tracts of generally coplanar outlet ports, a portion of at least one of said tracts being arched with respect to at least two of the other tracts and said inlet spout and at least part of each of said two other tracts are angled away from said arched tract, wherein the outlet ports of the manifold abut engine inlet ports on a side of the engine and the manifold is arranged such that a mouth of the inlet spout is generally directed away from said side of the engine and the tracts are substantially 13 accommodated in a space between the inlet spout and the side of the engine.

18. An inlet manifold substantially as hereinbefore described with reference to figures 3 to 6 of the 5 drawings.

19. An inlet manifold substantially as hereinbefore described with reference to figure 7 of the drawings.

20. An i.c. engine substantially as hereinbefore described with reference to figures 3 to 6 of the 10 drawings.

21. An i.c. engine substantially as hereinbefore described with reference to figure 7 of the drawings.