GB2408999A

GB2408999A - Cylinder head for an internal cumbustion engine

Info

Publication number: GB2408999A
Application number: GB0328805A
Authority: GB
Inventors: Timothy Morris; Anthony E Cole; Stephen L Clark
Original assignee: Ford Global Technologies LLC
Current assignee: Ford Global Technologies LLC
Priority date: 2003-12-12
Filing date: 2003-12-12
Publication date: 2005-06-15
Also published as: GB0328805D0

Abstract

A cylinder head 11 for an internal combustion engine comprises a combustion face 12, a portion of which forms a boundary for an engine cylinder, a valve inlet seat 20 and port 14 being mounted within. The port 14 extends as a single duct before branching into two conjoined ducts 21, 22 having mouths 16 connectable to an air intake manifold at an external and upstream surface 13. The single duct may flow into a helical form preferably extending up to one complete turn about the valve seat 20, clockwise or anticlockwise, the duct preferably tapering towards the seat 20. The conjoined ducts may have a partition wall comprising an insert located in the cylinder head. The cylinder head 11 may provide a method of introducing two air streams to a single inlet in a swirled manner, where air is supplied separately to the streams, where either one may be deactivated.

Description

Cylinder Head for an Internal Combustion Engine

Field

This invention relates to cylinder heads as part of the combustion chambers of internal combustion engines, and in particular to the air feed ports passing through the cylinder head of a diesel engine.

Background of the Invention

The typical multi-cylinder internal combustion engine will be provided with at least one inlet valve and one exhaust valve per combustion chamber and more modern high performance engines may have two or more inlet valves and two or more exhaust valves.

It is known that that in order to achieve maximum fuel efficiency with a compression ignition engine that the fuel is atomised by spraying the fuel into the combustion chamber at high velocity and that the air entering the combustion chamber is given a degree of swirl and turbulence so the air is distributed around the fuel to enhance combustion.

Prior art combustion chambers have been provided with two air inlet valves and two exhaust valves which provides various directions of swirl in the combustion chamber.

Each inlet valve may be connected by a respective port to a respective air intake manifold, so that the two inlet ports are each independently provided with an air flow to their respective inlet valves for the combustion chambers. The multiple inlet ports improve engine efficiency and improve the correct air motion characteristics required for the engine to produce the desired exhaust emissions.

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The present invention provides a cylinder head with a single inlet valve port which has at least some of the benefits of an engine having two inlet valve ports, and may also be applied to a two inlet port per cylinder engine to achieve even greater flow and motion control.

Statements of Invention

According to the present invention there is provided a cylinder head for an internal combustion engine, the head comprising a combustion face having a least one respective portion thereof which in use forms a boundary for a respective cylinder of the engine, the portion of the combustion face having mounted therein at least one inlet valve seat opening into an inlet valve port and extending upstream to an external surface of the cylinder head, the valve inlet port comprising a single duct adjacent the valve seat and branching upstream into two conjoined ducts having respective mouths at the external surface of the cylinder head connectable in use to an air intake manifold.

An internal combustion engine may be fuelled by petrol or gasoline, liquid petroleum gas, and diesel oil.

The air intake manifold may also be utilised for the recirculation of exhaust gases.

The path between the mouths and the respective inlet valve seat may form a down draught inlet port, or alternatively a cross head inlet port depending upon the design requirements. The mouths of the two conjoined ducts may be connected to respective air intake manifolds allowing either of the two ducts to be de-activated.

Preferably, the two conjoined ducts extend side by side from the mouths to their conjunction, and the duct dovvnstearn of the conjunction, that is extending from the conjunction to the valve seat, has a helical form with the two conjoined ducts entering the helix substantially at a tangent thereto. The helical portion may extend for up to one complete turn around the valve seat.

The duct downstream of the conjunction gradually tapers from a larger cross-sectional area down to a smaller cross-sectional area adjacent the inlet valve seat.

The direction of twist of the helical portion may be clockwise or anticlockwise depending upon the required air motion in the combustion chamber.

The two side by side conjoined ducts have a partition wall therebetween which may be integrally cast with the cylinder head, or may be an insert therein. The shape and length of the partition wall may be configured to produce a desired air flow through the two ducts. For engines requiring air supplied in a tumble motion, for example gasoline engines, the two ducts may be stacked, that is arranged one above the other.

The invention also provides an internal combustion engine, preferably a diesel engine, including a cylinder head according to the present invention. The engine is preferably a multi cylinder engine, and a respective portion of the combustion face provides the boundary for each cylinder.

According to a further aspect of the invention, in an internal combustion having at least one cylinder, there is provided a method of providing air to each respective combustion chamber, the method comprising supplying air in two air streams, merging the two air streams into a single combined air flow, and feeding the combined air flow to the combustion chamber via a single inlet valve.

The combined air stream is caused to swirl helically clockwise or anticlockwise to achieve a particular form of swirl.

Description of the Drawings

The invention will be described by way of example and with reference to the accompanying drawings in which: Fig. 1 is an isometric view of a cylinder head according to the present invention, 1 S Fig. 2 is an isometric view on a cut plane on the line shown in Fig. 1 and as viewed in the direction of the arrows II-II, with water jacket removed to aid clarity, Fig.3 is an isometric view on the same cut line as Fig.2 but viewed in the opposite direction as shown by the arrows III- III, Fig.4 is an isometric view of a model of a twin tract port as is shown in Figs. 1 Fig.5 is a second view of the model shown in Fig 4, Fig. 6 is a side view of another model of a second twin tract port, Fig.7 is an isometric view of the model shown in Fig. 6, and Fig.8 is a view of the model shown in Fig 6 and Fig.7 showing the mouths of the twin ducts.

Detailed Description of the Invention

With reference to Fig. 1, there is shown a cylinder head 11 for an internal combustion engine, in this example a four cylinder diesel engine. The head 11 has a combustion face 12 and a manifold face 13. The respective portions of the combustion face 12 each form a boundary for each respective cylinder. A plurality of valve ports, one inlet port 14 per cylinder and one exhaust port 15 per cylinder, open via respective valve seats 20 & onto the respective portions of the combustion face 12. The exhaust valve ports extend through the head 1 I to the manifold face 13 and the mouth 17 of each exhaust port is connectable to an exhaust manifold (not shown) in the conventional manner. The inlet valve ports 14 also extend through the head 11 to the manifold face 13 and each comprises a single duct 23 adjacent the valve seat 20 (see Fig. 2) which then branches into two ducts or tracts 21, 22 terminating in a pair 16 of side by side mouths 1 6A, 1 6B open to the manifold face 13. Each valve port 14 and 15 in use co-operates with a poppet valve (not shown) for opening and closing the valve ports in the conventional manner.

With reference now to Figs. 2, 3 and 4 also, each pair of mouths 16 comprise mouths 1 6A, 1 6B each of which opens into one of the pair of conjoined ducts or tracts 21, 22 respectively. The mouths 16 are connected to at least one air inlet manifold (not shown) for the supply of air or an air based gaseous mixture to the combustion chamber. In some engines the two ducts 21, 22 may be connected to respective air intake manifolds allowing either of the two ducts to be de-activated if desired.

In the present cylinder head 11, the two ducts 21, 22 form the upstream portion an air inlet valve port 14, which in this example of cylinder head is a down draught air inlet port.

Referring now to Figs 4 and 5, there is shown a model of one air inlet port 14 extending between the valve seat 20 and the manifold face 13. The two ducts 21 & 22 extend side by side into the head away from the manifold face 13 and then merge into the single duct 23 extending towards, and opening to, the valve seat 20. The single duct 23 describes a downward helix which passes around the valve guides 25 for the respective valve (not shown) which seals against the valve seat 20. The duct 23 has a gradually narrowing cross-section and is shaped to produce a desired air flow and swirl. The helix may be clockwise or anti- clockwise depending upon the particular swirl that is desired. The helix is fully or partially included to further influence air motion. The air inlet port 14 shown in Figs. 4 and 5 has a duct 23 with an anti-clockwise helix around the valve seat. The two ducts 21, 22 preferably join together at a tangent to the helix to form the single duct 23 which then extends for up to one turn before delivering air to the valve seat 20.

The mutual wall 26 between the two side by side ports 21, 22 may be formed integrally with the head casting or may be an insert. The length and shape of the mutual wall is adapted for the correct air flow characteristics required for the engine to produce the desired exhaust emissions signature.

The twin tract air inlet ports 14 enable the engine to operate the combustion chambers using a single inlet valve and obtain some of the benefits of an engine having two independent air inlet ports and valves. Air can be supplied independently, or conjointly, to the two tracts 21, 22, and by closing one or other of the tracts the air motion of one tract will produce a range of air flow movements, including swirls, tumbles, or combinations thereof. The resultant air motion will depend upon which tract is shut-off i.e the outer tract feeding the helix or the inner tract. The resultant air movement from the tracts will also be influenced by the geometric relationship of the tracts to the valve seat 20, which in itself may be influenced by the engine package and the locus of the lower duct 23 around the valve guide.

With reference now to Figs. 6-8, there is shown a model of a second form of air inlet port 44 which is a cross draught inlet port in which the single duct 53 describes a clockwise helix around the valve guide 55 before opening to the valve seat 40. The two tracts or ducts 41, 42 extend side by side as before with a common partition wall 46 extending therebetween. In this case the two ducts 41, 42 join at a confluence 54 which is proximate the valve guide 55.

Claims

Claims 1. A cylinder head for an internal combustion engine, the head

comprising a combustion face having at least one respective portion thereof which in use forms a boundary for a respective cylinder of the engine, the portion of the combustion face having mounted therein at least one inlet valve seat opening into a valve inlet port and extending upstream to an external surface of the cylinder head, the valve inlet port comprising a single duct adjacent the valve seat and branching upstream into two conjoined ducts having respective mouths at the external surface of the cylinder head connectable in use to an air intake manifold.
2. A cylinder head as claimed in Claim 1, wherein the path of the port between the mouths of the conjoined ducts and the respective inlet valve seat provides one of a down draught port and a cross head port.
3. A cylinder head as claimed in Claim I or 2, wherein the two conjoined ducts extend side by side from their mouths to their conjunction, and the portion of the inlet port downstream of the conjunction takes on a helical form with the two conjoined ducts entering the helix substantially at a tangent thereto.
4. A cylinder head as claimed in Claim 3, wherein the helical portion of the port extends for up to one complete turn around the valve seat.
5. A cylinder head as claimed in any one of claims 1 to 4, wherein the two conjoined ducts form a single duct downstream of their conjunction, which single duct gradually tapers from a larger cross-sectional area down to a smaller cross-sectional area adjacent the inlet valve seat.
6. A cylinder head as claimed in any one of Claims 3 to 5 as dependent on claim 3, wherein the helical portion has one of a clockwise or anticlockwise helix.
7. A cylinder head as claimed in Claim 3, wherein the two side by side conjoined ducts have a partition wall therebetween comprising an insert located in the cylinder head.
8. An internal combustion engine including a cylinder head according to any one of Claims 1 to 7.
9. An engine as claimed in Claim 8, which engine comprises a diesel engine.
10. In an internal combustion engine having at least one cylinder, a method of providing air to each respective combustion chamber, the method comprising supplying air in two air streams, merging the two air streams into a single combined air flow, and feeding the combined air flow to the combustion chamber via a single inlet valve.
A method as claimed in Claim 10, wherein the combined air flow is caused to swirl helically clockwise or anti-clockwise.
12. A method as claimed in Claim 10 or I 1, wherein air is supplied to the two air streams separately to allow either of the two air streams to be de-activated.