GB2121473A

GB2121473A - Intake manifold for an internal combustion engine

Info

Publication number: GB2121473A
Application number: GB08215848A
Authority: GB
Inventors: John Robert Humphries; Trevor Whitmore Biddulph
Original assignee: Ford Motor Co
Current assignee: Ford Motor Co
Priority date: 1982-06-01
Filing date: 1982-06-01
Publication date: 1983-12-21

Abstract

The path length along which air travels through the manifold from an inlet to outlets (8) may be varied by means of a respective flap valve (10) or each of the air valves which allow air from a first plenum chamber (4) to pass either directly into a conduit (7) connected to the air outlet (8) or via a passage (5) connecting the first plenum chamber with a second plenum chamber (6) to which the conduit (7) is connected. The valves (10) are actuated in accordance with engine speed or load to provide short path lengths at high loads or speeds and long path lengths at low loads or speeds, thereby optimising engine performance. <IMAGE>

Description

SPECIFICATION Intake manifold for an internal combustion engine This invention relates to intake manifolds for internal combustion engines.

Conventional intake manifolds comprise at least one air inlet, and a plurality of air outlets of fixed length communicating with the, or at least one, air inlet.

According to the present invention there is provided an intake manifold for an internal combustion engine comprising at least one air inlet and a plurality of air outlets communicating with the, or at least one air inlet, and means for varying the path length along which air travels through the manifold to the air outlets.

We have found that the performance of an internal combustion engine is influenced by the dimensions of the path, especially the length of the path along which air travels through the manifold to the air outlets. Thus, long intake path lengths produce higher torque and power at low engine speeds than at higher engine speeds, whereas short intake path lengths produce higher torque and power at high engine speeds than at lower engine speeds. By varying the intake path length in accordance with engine speed, it is possible to improve the overall performance of the engine.

In one convenient construction, each air outlet communicates with the, or one, air inlet along two paths of different lengths, and the means for selectively varying the path length comprises means for selectively directing air along one or other of the two paths to each outlet.

Preferably the air inlet or inlets communicate with a first plenum chamber, each air outlet communicates with a duct connected to the first plenum chamber via two entrances spaced along its length to define the two paths of different length, and the means for selectively directing air along the paths comprises valve means for selectively permitting air to flow into the duct through one or other of the entrances. For example, the valve means may comprise a valve member positioned at the entrance nearer the air outlet with which the duct communicates, and is movable between a first position, in which the entrance is closed, and a second position in which the entrance is open and the part of the duct upstream from the entrance is closed.

In the preferred embodiment of the engine, each duct comprises a conduit, a second plenum chamber common to all the ducts with which the conduits communicate, and a passage common to all the ducts effecting communication between the first and second plenum chambers.

Two embodiments of the invention will now be described, by way of example, only with reference to the accompanying drawings, in which: Figure 1 is a plan of a first inlet manifold in accordance with the invention.

Figure 2 is a cross-section taken along the line A-A of Figure 1.

Figure 3 is a plan of a second inlet manifold in accordance with the invention.

Figure 4 is a cross-section taken along line B B of Figure 3, and Figure 5 is a graph illustrating the performance of an engine incorporating an inlet manifold in accordance with the invention.

Referring to Figures 1 and 2 of the drawings an inlet manifold 1 for a V-6 engine comprises a single air inlet 2, which may be closed by a butterfly valve 3 and which communicates with a first plenum chamber 4. A passage 5 leading from the first plenum chamber 4 communicates with a second plenum chamber 6. Six conduits 7 lead from the second plenum chamber 6, pass through the first plenum chamber (as best seen in Figure 2) and terminate in air outlets 8 which can be connected to inlet ports of an internal combustion engine in a conventional manner.

Each conduit 7 communicates with the interior of the first plenum chamber 4 via an entrance port 9 which may be opened and closed by a flap valve 10.

Each flap valve 10 is movable between a first position (shown in full lines) in which the entrance port 9 is closed and a second position (shown in broken lines) in which the entrance port 9 is open, and the part of the conduit 7 upstream from the entrance port 9 is closed. The conduits 7 are arranged in two groups of three, along two parallel lines, and the flap valves 10 for each group of three conduits are mounted for movement about a common axis 11, 12 by means of common drive members 13, 14, e.g.

meshing gear sections, on the outside of the first plenum chamber 4. The drive members are operated by a conventional control device (not shown) such as a solenoid motor or a vacuum motor in response to signals indicating the performance of the engine, e.g. engine speed or load.

Each of the air outlets 8 therefore communicates with the air inlet 2 via the first plenum chamber 4 and a duct which comprises one of the conduits 7, the passage 5 and the second plenum chamber 6, the passage 5 and second plenum chamber 6 being common to all the ducts. Each duct has two entrances, namely the entrance port 9 and the mouth 1 5 of the passage 5. Since these two entrances are spaced from each other the two entrances provide path lengths for the air through the manifold of different lengths.

Figures 3 and 4 illustrate another inlet manifold 1 in accordance with the invention. This manifold is suitable for a 4-cylinder in-line engine.

Its construction is similar to that of the inlet manifold 1 of Figures 1 and 2 and similar parts have been identified by like reference numerals.

Since the conduits 7' are arranged in a single line, all the flap valves 10 can be operated from a single drive member (not shown).

The operation of the inlet manifold and its effect on the performance of the engine to which it is secured is illustrated with reference to Figure 5, which is a graph illustrating the variation of torque (Nm) and power (kW) of the engine with engine speed (R).

Considering the variation of torque with engine speed, when the flap valves 10 are in their first positions, the path length for the intake air through the inlet manifold is relatively long since the air must pass through the first plenum chamber 4, the passage 5, the second plenum chamber 6 and the part of the conduit 7 upstream from the entrance port 9. This produces a maximum torque at relatively low speeds, as indicated by the continuous line A B C D in Figure 5. When the flap valves 10 are in their second positions, the path length for the intake air through the manifold is relatively short since the air in the first plenum chamber can pass directly into the conduits 7 via the entrance ports 9, bypassing the second plenum chamber and the passage 5.This produces an increase in the torque at higher engine speeds compared with the torque of the engine when the flap valves 10 are in their first positions, as indicated by the dashed line A E C F.

Considering the variation of power w7th engine speed, when the flap valves 10 are in their first positions, the variation of power with engine speed follows the chain-dotted line G K C I J.

With the flap valves 10 in their second position, the variation of power with engine speed follows the dotted line G H C L M. Again therefor, it can be seen that long intake paths increase the power of the engine at lower engine speeds, whereas short intake paths increase the power of the engine at higher engine speeds.

Accordingly by controlling the positions of the flap valves 10 in accordance with engine speed it is possible to obtain the benefits of the short intake path iength-at high speeds and the long intake paths at low speeds so that the torque of the engine follows the path A B C F, and the power follows the path G K C L M.

In practice the precise shape of the curves illustrated in Figure 5 will vary with the sizes, shapes and relative configurations of the plenum chamber 4, 6, passage 5 and conduits 7.

Accordingly, to optimise the benefit of the engine it will be necessary to adjust or "tune" these shapes and sizes to suit each individual engine.

Additionally, since engine load also has an effect on the shapes of the curves in Figure 5, it may be desirable to include a control mechanism, such as a vacuum-operated servo-motor, which operates in response to changes in engine load to open and close the flap valves 10.

In an alternative construction (not shown) the second plenum chamber is divided into two subchambers each sub-chamber supplying half the conduits 7. Valve means is provided for preventing the flow of air into one of the subchambers so that half the cylinders of the engine can be deprived of air. This allows the engine to be driven from the remaining cylinders only in accordance with a conventional cylinder firing control mechanism which selectively deactivates certain cylinders of the engine under low-load conditions.

Claims

1. An intake manifold for an internal combustion engine comprising at least one air inlet and a plurality of air outlets communicating with the, or at least one, air inlet, and means for varying the path length along which air travels through the manifold to the air outlets.

2. A manifold according to claim 1 wherein each air outlet communicates with the, or one, air inlet or inlets along two paths of different lengths, and the said means for varying the path length comprises means for selectively directing air along one or other of the two paths to each air outlet.

3. A manifold according to claim 2 wherein the air inlet or inlets communicate with a first plenum chamber, each air outlet communicates with a duct connected to the first plenum chamber via two entrances spaced along its length, to define two paths of different length along the duct, and the means for selectively directing air along the paths comprises valve means for selectively permitting air to flow into the duct through one or other of the entrances.

4. A manifold according to claim 3 wherein the valve means comprises a valve member at the entrance nearer the air outlet with which the duct communicates, and is movable between a first position in which the said entrance is closed, and a second position in which the said entrance is open and the part of the duct upstream of the said entrance is closed.

5. A manifold according to claim 3 or claim 4 wherein each duct comprises a conduit, a second plenum chamber common to all the ducts which the conduits communicate, and a passage common to all the ducts effecting communication between the second plenum chamber and the first plenum chamber.

6. An intake manifold substantially as hereinbefore described and as illustrated in Figures 1 and 2 or Figures 3 and 4 of the drawings.

7. An internal combustion engine incorporating an intake manifold in accordance with any one of the preceding claims.