GB2413157A - Intake manifolds for internal combustion engines - Google Patents

Abstract

A hollow, elongate insert 1, eg of plastics, extends part-way into the hollow enclosure of the intake manifold 4. The insert 1 has a flange at one end for connection to the throttle body and has a chamfer at its other end. The insert may have an axial dividing baffle (11, fig.7) to provide channels (12,13) of different lengths. The use of an insert allows different vehicles using the same base engine to be tuned to have different characteristic sound qualities.

Description

Intake Manifolds for Internal Combustion Engines The present invention

relates to intake manifolds for internal combustion engines.

Intake (and exhaust) manifolds have a major effect on engine performance and emissions of noise and pollutants. Requirements for lower noise and pollutant emission levels has further increased the importance of the designs of intake (and exhaust) manifolds.

It is known that the geometry of an intake manifold has an effect on the frequency and amplitude of the sound waves and vibrations issuing from them as noise. Hence intake manifolds are often designed to attenuate the amplitudes of pressure waves and to act on specific frequency components.

One example of an intake manifold designed to improve induction noise quality is described in SAE Technical Paper "The Next Generation Northstar DOHC 4.6L V8 engine with four-cam continuously variable valve timing for Cadillac" by M Bonello et al, 2003, reference number 20031- 0922. Therein is described an intake manifold moulded from glass filled PA66. It is connected at one end to a throttle body. The manifold has a fixed central feed to a plenum for improving induction noise quality. A central feed has the effect of providing nearly equal length gas flow and acoustic paths from the throttle body to the runner entrance to each cylinder.

WO-A-94/04816 discloses a 4-cylinder engine having an intake manifold designed to reduce airborne noise. The manifold comprises an enclosure and a cylindrical air supply pipe connected at one of its ends to an inlet side of the enclosure and extending into the enclosure with its free end terminating at a point equidistant from the inlet parts of the third and fourth cylinders. - 2

Current trends and requirements relating to vehicle styling, front suspension design for improved vehicle ride and handling, and increasing technology content of internal combustion engines sets difficult design and packaging constraints on intake manifolds.

This leads to unique manifold solutions for each vehicle application of an otherwise common base engine. Occasionally a package space is defined prior to the development of an optimum intake manifold geometry for acoustic and flow performance. These factors can lead to a sub-optimal intake manifold design for both acoustic and flow performance, e.g. poor distribution of exhaust gas recirculation and positive crankcase ventilation gases.

Further, undesirable harsh sounds can be generated from the intake orifice as a result of 10sub-optimal design. It has been noted that induction noises of around 600 Hz to 800 Hz sound "thrashy" to the driver.

Using a known fixed feed arrangement as mentioned above requires a unique intake manifold to be designed and built for each different vehicle application even though the same base engine is being used.

15Hence an intake manifold design which overcomes this inflexibility of the known arrangements would be desirable.

The present invention comprises an intake manifold for an internal combustion engine for connection between a throttle body and a cylinder head of the engine, the intake manifold comprising a hollow enclosure and a hollow, elongate insert, which insert has a flange at one of its ends for connection to the throttle body and which extends part-way into the enclosure and whose distal end terminates in a chamfer.

The chamfer has the advantage of ensuring that the cylinders closest to the throttle body are not deprived of air.

The insert may be provided with one or more axial baffles, dividing the insert into two or more portions. The portions may have unequal lengths.

The insert may be made from plastics by a blow or injection moulding process.

It may be made of porous material.

It may be perforated.

Thus, the intake manifold can be "tuned" by choosing an insert with a particular length, porosity and profile to suit different types and styles of vehicle fitted with the same engine.

Different lengths will give different acoustic qualities. For example, tuning the insert so that all gas flow path lengths from throttle body to each cylinder entrance are as near equal as possible (i.e. a centre feed) would give a quieter, smoother sound. Increasing the difference in path lengths would give a more "sporty" or raucous sound. Narrow-band resonances may be "tuned out" by using quarter wave or Helmholtz resonators at suitable locations in the intake system. This technique of using quarter-wave or Helmholtz resonators for this purpose is known and usually also includes a separate duct upstream of the throttle body.

The invention allows for a common intake manifold architecture for an engine commodity whereas with known techniques, a unique intake manifold has to be designed and manufactured for each vehicle application.

The invention also allows for an extra degree of flexibility for styling engineers and for noise, vibration and harshness (NVH) engineers so that they may give vehicles their own sound quality and performance attributes and character.

The invention may be used in V-formation, W-formation or in-line engines.

Inclusion of an insert in accordance with the invention in an intake manifold system allows intake manifold geometry flexibility to tune for sound quality and engine performance. A modular intake manifold design with the inclusion of tunable inserts and - 4 baffles can lead to decreased complexity and cost and can increase the commonality of engine commodities. Allowing a central insert to be a variable for tuning can lead to improved intake orifice sound quality by reducing harsh sounding frequency content above the engine firing frequency. Equalizing the effective path lengths from port to throttle body reduces harsh and thrashy sounds due to multiple resonances in, but not limited, to the 500-1000Hz frequency band. With this design feature the intake manifold can more comfortably conform to the vehicle package (e.g. preserving bonnet line for styling) while allowing acoustic and performance optimization. This invention increases the level of tunability for intake manifolds and contributes to reducing NVH. For V8 engine applications, the equal effective path lengths from port to throttle body reduces harsh and thrashy sounds in the 600-800Hz range that adversely impact speech intelligibility in the vehicle. This is a band where vehicle soundproofing materials are less effective and so additional quantities have to be used to achieve the desired result. Using the present invention can reduce the amount of sound-deadening material required, thereby giving a cost saving.

Further cost savings are given by reducing the number of quarter wave or Helmholtz resonators required as there is less frequency content to tune out.

The invention has been shown to reduce overall vehicle noise levels, due to the elimination of harsh sounds.

Some embodiments of the invention will now be described, by way of example only, with reference to the drawings of which; Fig. l is a perspective view of a first insert for an intake manifold in accordance with a first embodiment of the invention, Fig. 2 is a cutaway plan view showing the intake manifold in accordance with the first embodiment fitted to a V8 engine, Figs. 3 and 4 are cutaway side views of the intake manifold of Fig. 2, Fig. 5 is an end view of the intake manifold of Figs. 3 and 4, Fig. 6 is a perspective view of the intake manifold of Figs. 3 and 4, Fig. 7 is a perspective view of a second, alternative insert for an intake manifold in accordance with a second embodiment of the invention, Fig. 8 is a cutaway side view showing the intake manifold in accordance with the second embodiment fitted to a V8 engine, Figs. 9 and 10 are opposite end views of the intake manifold of Fig. 8, and Fig. 11 is a perspective view of the intake manifold of Fig. 8.

Referring to Fig. 1, an insert 1 is hollow and made from plastics. One end incorporates a flange 2 for connection to a throttle body of an internal combustion engine and the other end incorporates a chamfer 3. The insert has a cylindrical cross-section.

With reference to Fig's 2-6, the insert 1 is located within an intake manifold enclosure 4 of an engine having a V8 configuration. Fig. 2 shows a throttle body elbow 5 to which the intake manifold enclosure 4 and the insert's flange 2 is attached. The insert 1 extends from the throttle body elbow 5 into the intake manifold enclosure and its furthest extremity 6 is at a point half-way along the enclosure 4.

The manifold enclosure 4 incorporates runners 7 for guiding air flow into the inlet ports 8 for each of its eight cylinders (not shown) In this configuration with the effective length of the insert 1 being half that of the manifold enclosure 4, the path lengths from the throttle body 5 to the inlets ports 8 of each - 6 cylinder are almost equal, (for smooth sound quality). The chamfer 3 on the insert 1 ensures that the cylinders closest to the throttle body 5 are not deprived of air.

By choosing this particular length of insert, the induction noise produced in the intake manifold is tuned to have particular characteristics.

The induction sound characteristics of the same V8 engine can be changed by removing the insert of Fig. 1 and replacing it with the insert illustrated in Fig. 7. This alternative insert 10 has a cylindrical crosssection and incorporates a central, plane, axial baffle 11 which divides the insert into two, channels 12, 13.

One end of the insert 10 incorporates a flange for attachment to the throttle body elbow 5. A first channel 12 extends from the flange 14, has a length equal to three quarters of the length of the intake manifold and terminates in a chamfer 15. A second channel 13 also extends from the flange 14 and terminates in a chamfer 16 but has a length equal to one quarter of the length of the intake manifold.

The presence of the chamfers 15, 16 ensures that the cylinders close to the throttle body 5 are not deprived of air.

Figs. 8-11 show the dual channel insert 10 located within the intake manifold of a V8 engine.

Components common to Figs. 8-11 and 24 bear the same reference numerals.

The dual channel insert 10 provides two tunable lengths and so gives a greater choice of path lengths from the throttle body elbow 5 to each inlet port 8 of each cylinder 9. The insert 10 of Fig. 7 will tend to give a more raucous sound compared with the arrangement of Figs. 1-6. - 7

It will be appreciated that the inserts!, 10 do not need to have a cylindrical cross- section. Also further baffles may be added to provide multiple channels. Further, the length of the insert 1 and channels 12, 13 may be altered in order to achieve a desired sound characteristic.

The inserts are not limited to use with the V8 configuration shown in the drawings. - 8

Claims (6)

1. An intake manifold for an internal combustion engine for connection between a throttle body and a cylinder head of the engine, the intake manifold comprising a hollow enclosure and a hollow, elongate insert, which insert has a flange at one of its ends for connection to the throttle body and which extends part-way into the enclosure and whose distal end terminates in a chamfer.

2. An intake manifold as claimed in claim 1 in which the insert is provided with one or more axial baffles, dividing the insert into two or more portions.

3. An intake manifold as claimed in claim 2 in which the portions have unequal lengths.

4. An intake manifold as claimed in any preceding claim and having a cylindrical cross- section.

5. An intake manifold as claimed in any preceding claim in which the insert is made from plastics.

6. An insert for an intake manifold substantially as hereinbefore described with reference to the drawings.