GB2306195A

GB2306195A - Partitioned engine intake port

Info

Publication number: GB2306195A
Application number: GB9521209A
Authority: GB
Inventors: Thomas Tsoi-Hei Ma
Original assignee: Ford Motor Co
Current assignee: Ford Motor Co
Priority date: 1995-10-14
Filing date: 1995-10-14
Publication date: 1997-04-30
Also published as: GB9521209D0

Abstract

A port 30 associated with one or more intake poppet valves 32 is partitioned by a dividing wall 14 to separate the gases entering the combustion chamber into distinct streams. The dividing wall 14 extends from the outer end 12 of the port to the vicinity of a poppet valve 32 and is defined by an insert 10 that is formed separately from the intake port 30 and shaped to ensure that the dividing wall 14 can only assume a predetermined position within the port 30. The insert 10 is formed of plastics material that is sufficiently rigid to enable the partition wall 14 to withstand deformation during engine operation but is conformable during assembly of the insert 10 into the port 30 to allow the lateral edges of the wall 14 to fit snugly against the inner surface of the port 30 leaving substantially no gap. Walls (14a, 14b, Fig.2) separating gases flowing to respective valves are connected by a resilient bar (12a). The insert 10 may be retained by the intake manifold with walls which engage the upstream ends of the wall 14 and the stiffening ribs 16.

Description

Partitioned Engine Intake Port Field of the invention The present invention relates to an internal combustion engine having a port associated with one or more intake poppet valves and partitioned by a dividing wall to separate the gases entering the combustion chamber into distinct streams, the dividing wall extending from the outer end of the port to the vicinity of a poppet valve.

Background of the invention In a stratified charge engine having a partitioned intake port, it is important that substantially no gap should remain between the dividing wall and the inner surface of the port. Hitherto, two techniques have been proposed for forming such a divided port, the first involving casting the dividing wall as part of the engine cylinder head and the second placing a separately formed insert into the port after it has been cast.

If the dividing wall is cast in situ, the casting process places limitations that make it difficult to make the dividing wall thin or skewed. If a separately formed insert is used, it is difficult to ensure that it can be made in the correct shape to fit snugly inside the port without leaving gaps around the edges of the dividing wall.

Furthermore, in the case of some ports, their internal geometry would preclude a precisely formed dividing wall from being assembled into the port in this manner.

Summary of the invention With a view to mitigating the foregoing disadvantages, the dividing wall in the present invention is defined by an insert that is formed separately from the intake port and shaped to ensure that the dividing wall can only assume a predetermined position within the port and the insert is formed of a material that is sufficiently rigid to enable the partition wall to withstand deformation during engine operation but is conformable during assembly of the insert into the port to allow the lateral edges of the dividing wall to fit snugly against the inner surface of the port leaving substantially no gap.

To ensure that the insert can only adopt a predetermined position within the port, it should make contact with the inner wall of the port in regions which are not rotationally symmetrical about the axis of insertion.

To prevent lateral flapping of the dividing wall, it is desirable to provide stiffening ribs transverse to the plane of the dividing wall.

Advantageously, the stiffening ribs may additionally contact the inner surface of the port to inhibit further any lateral movement of the insert within the port.

While the above steps restrict the position of the insert in two planes, they do not define the extent of penetration of the insert into the port. For this purpose, it is desirable to form a radial stop projection on the outer end of the insert that is clamped by the mating manifold flange against the outer surface of the engine block or cylinder head in which the port is formed.

If the mating manifold is itself partitioned by a dividing wall in the manifold branch, then the conformability of the insert assists in sealing against the dividing wall in the manifold branch to ensure that the separate gas streams do not mix at the joint between the manifold and the engine.

In current manufacture, it is common to define the shape of ports by computer using CAD-CAM (computer aided design and computer aided manufacture). With a CAD-CAM system, the precise shape of the insert to fit snugly in the port can be defined and using laser lithographic techniques the computer data can be converted into a three dimensional master from which further inserts can be mass produced by casting or moulding.

The insert can be made of a high temperature plastics material capable of withstanding the operating temperatures within the port. It is also important that the chemical composition of the insert should prevent it from reacting with the gases entering the combustion chamber which may include both fuel and recirculated exhaust gases.

The plastics material must of necessity be rigid if it is to act as a dividing wall. This requirement does not preclude the insert having a permanent limited degree of elasticity to allow the insert to conform closely to the inner wall of the intake port and to be elastically deformed during insertion into the port. It is, however, alternatively possible in some cases for the insert to be made of a material that is fully rigid during normal use and to render it conformable only during assembly by chemical or physical treatment.

The plane of the dividing wall may either be flat or skewed.

In both cases, it is important that any stiffening ribs should follow the shape of the gas flow past the dividing wall in order not to obstruct such flow.

If the port comprises two siamesed ports, the dividing walls of the two individual ports may be linked at their outer ends, the link being lightly spring-loaded to urge the individual walls against opposite sides of the two siamesed intake ports. The flexibility of the insert can in this case allow the dividing walls to be pressed towards each other for insertion through the narrow mouth of the siamesed port, the walls subsequently springing apart to occupy their correct positions in the respective intake ports.

Brief description of the drawings The invention will now be described further, by way of example, with reference to the accompanying drawings, in which : Figure 1 shows an insert (shown in solid lines) for a single intake port leading to a poppet valve (shown in dotted lines), and Figure 2 shows an insert for two siamesed intake ports that share a common mouth but lead to different poppet valves of the same cylinder.

Detailed description of the preferred embodiments In Figure 1 there is shown an insert 10 for partitioning an intake port 30 leading to a poppet valve 32. At its outer end 12 remote from the poppet valve 32 the insert 10 has two bars of oval cross-section that extend vertically and horizontally. The ends of the bars have tapered radial projections to rest against a conical surface at the mouth of the intake port to limit the degree of insertion of the insert 10 into the intake port 30.

Two dividing walls 14 and 16 extend from the bars towards the closed end of the intake port 30. The wall 14 divides the intake port vertically while the wall 16 divides the intake port horizontally. Both walls can be used as dividing walls and make contact with the inner surface of the intake port 30 along their lateral edges. Each of the walls also acts as a stiffening rib for the other and the cruciform cross-section prevents lateral deflection of both walls.

To permit the insert 10 to be assembled into the port, it is formed of a plastics material that has sufficient resilience to be deformable and to conform to the surface of the intake port 30. The plastics material must of course be suitable for withstanding the environmental conditions within the intake port including the temperature and the chemical vapours.

The insert 10 is in use clamped between the flange of the intake manifold and the mating surface of the engine. The same insert can be used for vertical or horizontal partitioning of the port to achieve either swirl or tumble stratification in the intake charge. The intake manifold will have a dividing wall that sealingly mates with the insert 10 along one of the lines A-A and B-B in the drawing.

The other wall will not act as a partition for the separate intake streams but it will act as stiffening to prevent lateral deflection of the dividing wall and will also streamline the flow in each stream. Of course it is not essential that both the walls 14 and 16 should make contact with the inner surface of the intake port, it being sufficient for either one of them to make such contact depending on the desired orientation of the partition. The advantage of the illustrated insert is that it will permit either orientation.

The insert of Figure 2 is specifically designed for a siamesed intake port and comprises two vertical dividing walls 14a and 14b. A common resilient horizontal bar 12a connects the two walls at their outer ends and stiffening ribs are provided only on the sides of the walls 14a and 14b that face away from each other. The bar 12a can be bent to allow the inner ends of the walls 14a and 14b to come towards each other so that they can be inserted through the narrow siamesed mouth of the intake ports but after insertion the walls 14a and 14b are resiliently urged apart to make contact with the inner surfaces of the respective ports. The absence of stiffening ribs from the sides of the walls facing each other affords an unobstructed channel through which fuel may be targeted and a minimum surface area to which fuel droplets may adhere.

Claims

1. An internal combustion engine having a port associated with one or more intake poppet valves and partitioned by a dividing wall to separate the gases entering the combustion chamber into distinct streams, the dividing wall extending from the outer end of the port to the vicinity of a poppet valve, wherein the dividing wall is defined by an insert that is formed separately from the intake port and shaped to ensure that the dividing wall can only assume a predetermined position within the port and the insert is formed of a material that is sufficiently rigid to enable the partition wall to withstand deformation during engine operation but is conformable during assembly of the insert into the port to allow the lateral edges of the dividing wall to fit snugly against the inner surface of the port leaving substantially no gap.

2. An engine as claimed in claim 1, wherein, in order to ensure that the insert can only adopt a predetermined position within the port, the insert makes contact with the inner wall of the port in regions which are not rotationally symmetrical about the axis of insertion.

3. An engine as claimed in claim 1 or 2, wherein in order to prevent lateral flapping of the dividing wall, stiffening ribs are provided transverse to the plane of the dividing wall.

4. An engine as claimed in claim 3, wherein the stiffening ribs additionally contact the inner surface of the port to inhibit further any lateral movement of the insert within the port.

5. An engine as claimed in any preceding claim, wherein a radial stop projection is formed on the outer end of the insert that is clamped by the mating flange of an intake manifold against the outer surface of the engine block or cylinder head in which the port is formed, thereby limiting the degree of penetration of the insert into the port.

6. An engine as claimed in claim 5, wherein the mating manifold is itself partitioned, the dividing wall in the branch of the intake manifold being aligned with and making sealing contact against the edge of the dividing wall in the intake port.

7. An engine as claimed in any preceding claim, wherein the insert is formed of a material that permanently retains a degree of flexibility and deformability.

8. An engine as claimed in any of claims 1 to 6, wherein the insert is formed of a rigid material and is temporarily rendered flexible and deformable during assembly into the intake port by chemical or physical treatment.

9. An engine as claimed in any preceding claim, wherein the plane of the dividing wall is flat.

10. An engine as claimed in any of claims 1 to 8, wherein the plane of the dividing wall is skewed.

11. An engine as claimed in any preceding claim, wherein the intake port comprises two siamesed ports sharing a common mouth, and the dividing walls of the insert into the two individual ports are linked at their outer ends, the link being lightly spring-loaded to urge the individual walls against opposite sides of the two siamesed intake ports.

12. An engine having an intake port constructed substantially as herein described with reference to and as illustrated in the accompanying drawings.