Method of reducing suction noise of an engine and air intake system with noise reducing diffuser

Abstract: An air diffuser (20) for an air intake system of an internal combustion engine. The air intake system includes a throttle body (22) up stream from an intake manifold (24), with the air diffuser (20) mounted between them. The air diffuser (20) includes vanes (62,64) extending into its main bore (52) in order to diffuse and redirect the air flowing from the throttle body (22) into the intake manifold (24). The diffusion and redirection of the air reduces the noise emanating from the intake manifold (24) for particular engine operating conditions.

Description: The present invention relates to an air intake system for an internal combustion engine and more particularly to noise suppression within the air intake system for an engine in a vehicle. Current internal combustion engines employed to power vehicles generally operate with air intake systems that include a throttle body and intake manifold assembly to control and direct the air flow into the engine. This portion of the air intake system has generally been made of metal. However, in today's vehicles, an emphasis is placed on fuel economy and exhaust emissions reductions. This has lead to the desire to form the intake manifold and possibly even the throttle body out of plastic types of materials. Plastic parts can be formed which are lighter in weight and can be formed into more complex shapes than equivalent metal parts, allowing for improved air flow and thus improving both fuel economy and engine performance. Although these improvements are welcome, nonetheless, there are other characteristics of plastics that are less desirable than equivalent metal components. For example, plastic is less dense than metal, which allows for more transmission of sound through it. Consequently, sound generated within the intake manifold, for instance, will more readily pass through into the engine compartment. This sound, then, can radiate to a driver of a vehicle, who may object to it. This is particularly true since, in general, engines are being designed overall to operate more quietly, making any stray noise more noticeable. One noise generated within the intake manifold of an engine is a whooshing noise generated by the air flow pattern created as the air flows past a butterfly or other throttle valve in the throttle body. This is particularly true for engine conditions such as tip-in or fast opening of the throttle valve. With previous engines, either due to the other background noises produced which drowned out this whooshing noise or because the intake manifold was metal which substantially dampened the noise, vehicle drivers would not hear it. Now with quieter engines and plastic manifolds, it is noticeable and objectionable to some drivers. The invention seeks to provide an air intake system for a vehicle engine in which the noise generated by air flow through the throttle body and intake manifold is reduced, thus reducing the noise that a vehicle operator will hear. According to a first aspect of the invention, there is provided a method of reducing noise emanating from the intake system of a fuel injected internal combustion engine having an intake throttle, an intake manifold, and fuel injectors for injecting fuel into the intake air downstream of the intake throttle, which method comprises placing in the intake system downstream of the intake throttle and upstream of the fuel injectors a diffuser comprising a set of vanes which are spaced from one another in a plane transverse to the direction of the intake air flowing through the diffuser and which protrude into the path of the intake air, the vanes being operative to reduce noise by introducing into the intake air stream counter-rotating vortices of turbulence. According to a second aspect of the invention, there is provided an air intake system for a fuel injected internal combustion engine including a throttle body, an air intake manifold, and an air diffuser comprising a flat plate portion and arranged in the intake manifold downstream of the throttle body and upstream of the fuel injectors for reducing noise emanating from the intake system by introducing turbulence into the air stream passing through the throttle body, the air diffuser having a main bore defined by a bore wall and a set of vanes spaced from one another across the bore and extending from a portion of the bore wall into the main bore. According to a further aspect of the invention, there is provided an air intake system for a fuel injected internal combustion engine including a throttle body, an air intake manifold, and an air diffuser, arranged in the intake manifold downstream of the throttle body and upstream of the fuel injectors for reducing noise emanating from the intake system by introducing turbulence into the air stream passing through the throttle body, the air diffuser having a main bore defined by a bore wall; and a plurality of vanes forming a first set, spaced from one another and extending parallel to one another from a portion of the bore wall into the main bore. It is an advantage of the preferred embodiments of the invention, that they may be implemented in a cost effective manner and without requiring a change or restriction in the air flow that would adversely effect engine operation. The problem of noise generated within the intake manifold has not been addressed in the prior art. However, it has been proposed in US-A-4,672,940 and FR-A-2,602 277 to position a diffuser immediately downstream of the carburettor in improve fuel preparation by creating turbulence. An air and fuel mixture subjected to such turbulence is improved because fuel particle size can be reduced by the turbulence and pockets of reduced pressure promote fuel evaporation. There is no teaching in the prior art that this results in reduced intake system noise and no suggestion that a diffuser should be used to create turbulence before fuel has been introduced into the intake air. The invention will now be described further, by way of example, with reference to the accompanying drawings, in which: Fig. 1 is a partially exploded, perspective view of a portion of an air intake system for an internal combustion engine, in accordance with the present invention; Fig. 2 is a side view of an air diffuser, taken in the direction of arrow 2 in Fig. 1; Fig. 3 is a sectional view taken from line 3-3 in Fig. 2; Fig. 4 is an end view taken along line 4-4 in Fig. 2; Fig. 5 is a side view of an air diffuser, similar to Fig. 2, illustrating a second embodiment of the present invention; Fig. 6 is a side view of an air diffuser, similar to Fig. 2, illustrating a third embodiment of the present invention; Fig. 7 is a sectional view taken along line 7-7 in Fig. 6; Fig 8 is a partial, side view of an intake manifold illustrating a fourth embodiment of the present invention; Fig. 9 is a side view of a throttle body, illustrating a fifth embodiment of the present invention; Fig. 10 is a side view of an air diffuser, similar to Fig. 2, illustrating a sixth embodiment of the present invention; Fig. 11 is a sideview of an air diffuser, similar to Fig. 2, illustrating a seventh embodiment of the present invention; and Fig. 12 is a side view of an air diffuser, similar to Fig. 2, illustrating an eighth embodiment of the present invention. Figs. 1-4 illustrate an embodiment of the present invention in which an air diffuser 20 is mounted between a throttle body 22 and an intake manifold 24, preferably fabricated of a plastic type of material. The throttle body 22 illustrated is conventional with a generally cylindrical wall defining a main bore 26 within which a butterfly valve 28 is mounted to a throttle shaft and lever assembly 30, which controls the angle of rotation of the valve 28. A mounting base 32 portion of the throttle body 22 includes four bolt holes 34 for mounting the throttle body 22 to the intake manifold 24. The throttle body 22 can be made of metal or plastic, as desired. The intake manifold 24 is illustrated here for a V-type of engine configuration, but the invention applies as well to in-line engine configurations. The intake manifold 24 includes a generally cylindrical wall defining a main bore 36 of substantially the same diameter as the main bore 26 of the throttle body 22. This bore 36 splits into two smaller bores 38, one each for a respective one of the banks of cylinders in the engine, not shown. The smaller bores 38 lead to a corresponding one of two plenums 40 in the intake manifold 24, which in turn, direct the air through individual ports 42 to the engine. Fuel injectors, not shown, are located downstream of the throttle body 22, mounted to the intake manifold or the cylinder head of the engine, as the case may be, in a conventional manner. A mounting base 44 surrounds the entrance to the main bore 36 of the manifold 24, and includes four threaded bolt holes 46, for receiving bolts 48, which secures the throttle body 22 to the intake manifold 24. Up to this point in the description, the components are generally assumed to be conventional, although various design modifications known within the art can be made to these components without departing from scope of the present invention. Mounted between the base 32 of the throttle body 22 and the base 44 of the manifold 24 is the air diffuser 20. The air diffuser 20 is basically a flat plate with a short, generally cylindrical wall defining a main bore 52 therethrough. The main bore 52 is sized to be essentially the same diameter as the main bore 26 in the throttle body 22. Four bolt holes 54 align with the bolt holes 34 in the throttle body 22, so that the main bores for the air diffuser 20, throttle body 22 and intake manifold 24 align. A recess 50 encircles the main bore 52, as well as a recess 50 around the main bore 36 of the intake manifold 24. These recesses are filled with conventional silicon sealer for sealing between the various parts. In order to assure proper alignment and orientation of the air diffuser 20 relative to the throttle body 22, a pair of bosses extend from the upstream side 56 of the air diffuser 20. The first boss 58 has a cylindrical wall, which is sized to fit within a similarly shaped and sized recess, not shown, in the base 32 of the throttle body 22 about a corresponding bolt hole 34. The second boss 60 has a generally cylindrical wall with a pair of flats opposite one another on it. This second boss 60 is sized to fit within a similarly shaped and sized recess, not shown, in the base 32 of the throttle body 22 about a corresponding bolt hole 34. The bosses 58, 60 then, assure that the air diffuser 20 can only be installed in the proper orientation. Extending from the wall of the main bore 52 of the air diffuser 20 are two sets of vanes, a lower set of vanes 62 and an upper set of vanes 64. The lower set of vanes 62 extend upward from the main bore 52 parallel to each other. The lower vanes 62 are as deep as the width of the diffuser 20 itself. The spacing between the lower vanes 62 is also approximately equal. The upper set of vanes 64 extend downward from the main bore 52 parallel to each other and are shorter than the lower set of vanes 62. The upper vanes 64 are generally equally spaced apart. The upper vanes 64 are also as deep as the width of the diffuser 20 itself at their bases, but the upstream edges taper as they extend downward from the bore wall. Also, the upper vanes 64 in the middle of the set are shorter than the others. The reason for the size and shape variations between the upper and lower sets of vanes 62, 64 is not for air flow reasons, but because of possible interference with the butterfly valve 28 when it rotates toward its full open position. For the particular throttle body 22 illustrated herein, the butterfly valve rotates clockwise as viewed in Fig. 1, thus causing the upper edge of the valve 28 to tip downstream toward the air diffuser 20 while the lower edge tips upstream away from the air diffuser 20. The butterfly valve 28 is located downstream in the main bore 26 such that, for some open positions, the upper edge extends downstream beyond the bore 26, through the main bore 52 of the air diffuser 20 and into the main bore 36 of the intake manifold 24. The reason for the downstream location of the butterfly valve 28 is that the throttle body 22 is supported by the intake manifold 24 in a cantilever fashion, so the farther the throttle body 22 extends from the manifold 24, the more bending moment the mounting base 44 of the manifold 24 has to support. Consequently, the upper set of vanes 64 are limited in length for particular throttle body configurations in order to avoid interfering with the movement of the butterfly valve 28, while the lower set of vanes 62 do not have this interference concern. An example of typical dimensions for the air diffuser 20 for a common V-6 engine having a nominal main bore diameter of about 66 millimetres (mm) would be generally equal centre-to-centre spacing of about 5 to 6 mm with the vanes 62,64 being about 1.5 mm thick and having an average height for all of the vanes of about 10 mm. The spacing between the vanes can be narrower. However, narrower spacing, in general, does not improve the noise attenuation sufficiently to justify the increased flow restrictions. Also, some minimum spacing limit is desirable to avoid the potential for sludge and ice build-up between the vanes, which can interfere with air flow. Additionally, the vanes 62,64 can be configured with a greater thickness, however, the trade-off between the amount of obstruction caused by the vanes (reducing horsepower of the engine) and the noise attenuation improvement by lengthening the vanes must be considered. The thickness of the plate portion of the air diffuser 20 can also be varied depending upon space constraints and the desired air flow effect. There is an increase with attenuation with increased plate thickness, however, throttle plate clearance is needed and increased length will also increases flow losses. The operation of the air intake system will now be described. When the engine, not illustrated, is operating in an idle mode, the butterfly valve 28 is closed, and only a small amount of air passes through the throttle body 22 and into the manifold 24. As the butterfly valve 28 begins to open, the air now flows through the main bore 26 around the top and bottom edges of the butterfly valve 28. Generally, then, the air flow is along the top and bottom of the main bore 26, flowing generally between the vanes 62,64, which are located along the upper and lower surfaces of the air diffuser bore 52. When the air flows past the partially open throttle plate, a high velocity turbulent air flow is created by the pressure drop across the throttle plate 28. As the air flows between the vanes 62,64, the vanes 62,64 will diffuse and redirect the air flow pattern such that the air creates small vortices of turbulence around each vane, but with each adjacent vorticy rotating in the opposite direction, thus cancelling each other out. This reduces the noise created, which reduces the noise radiated from the intake manifold 24. So, proper spacing depends upon getting effective cancelling out of vortices as opposed to random spacing which may just cause turbulence in the air flow. Generally the whoosh noise generated is the greatest at tip-in or fast opening of the throttle plate and also at part throttle cruising/tip-in conditions, which can be mistaken by a driver for a vacuum leak on the engine. Thus, with this new air flow pattern, the whoosh noise generated from the air flow will be attenuated, consequently reducing the overall noise passing through the intake manifold 24 and into the engine compartment. Again, the amount of noise attenuation improvement due to an increase in the size of the vanes must be balanced against the amount of flow loss (and hence horsepower loss) due to the vanes being in the air stream. A second embodiment of the present invention is illustrated in Fig. 5. This air diffuser 220 is used in place of the air diffuser 20, illustrated in Fig. 1, for this embodiment. In this second embodiment, similar elements are similarly designated, but with 200 series numbers. The vanes 262,264 in the air diffuser 220 are the same length for both the upper set 264 and the lower set 262. Both taper downstream as they extend inward into the bore 252, in order to avoid potential interference with the throttle valve 28 on the upper vanes 264. Further, the first boss 258 and second boss 260 are sized and shaped the same. The advantage of tapering both sets of vanes 262,264 and providing equal lengths is that the air diffuser 220 is now symmetrical between its top and bottom and can thus be installed with either set of vanes acting as the upper vanes, making assembly somewhat easier. The disadvantage is the risk of interference between the upper vanes 262 and the throttle valve 28 since the upper vanes 262 are now longer, depending upon the configuration of the particular throttle body 22 one employs. Figs. 6 and 7 illustrate a third embodiment of the present invention. This air diffuser 320 is used in place of the air diffuser 20, illustrated in Fig. 1, for this embodiment. In this third embodiment, similar elements are similarly designated, but with 300 series numbers. The upper vanes 364 and the lower vanes 362 now not only extend into the bore 352, but also extend aft of the downstream surface 66 of the air diffuser 320. This allows for more influence on the air flow pattern by the vanes 362,362 without having to increase the thickness of the plate itself, assuring that the space taken by the air diffuser 320 is minimised. Fig. 8 illustrates a fourth embodiment of the present invention. This integral air diffuser 420 is used in place of the air diffuser 20, illustrated in Fig. 1, for this embodiment. In this fourth embodiment, similar elements are similarly designated, but with 400 series numbers. The air diffuser 420 is now not formed from a separate plate, but is integral with the intake manifold 424. The lower vanes 462 and the upper vanes 464 are moulded into the main bore 436 of a plastic intake manifold 424. Consequently, the chance for interference between the vanes and the butterfly valve 28, seen in Fig. 1, is lessened, while also minimising the cantilever of the throttle body from the intake manifold 424 and the overall size of this structure. Further, one less part and seal need to be assembled. On the other hand, mouldings for plastic intake manifolds 424 generally are complex and this adds to the complexity of the moulding, which may or may not make this a desirable alternative depending upon ones design constraints. Fig. 9 illustrates a fifth embodiment of the present invention. This integral air diffuser 520 is used in place of the air diffuser 20, illustrated in Fig. 1, for this embodiment. In this fifth embodiment, similar elements are similarly designated, but with 500 series numbers. The air diffuser 520 again is not formed from a separate plate, but now is integral with the throttle body 522, with the lower set of vanes 562 and the upper set of vanes 564 mounted to the wall of the main bore 526 of the throttle body 522. Again, one less part and seal need to be assembled, and the overall size of the structure can be reduced. On the other hand, this complicates the fabrication of the throttle body 522 and makes designing to avoid interference between the upper vanes 564 and the butterfly valve more significant, which may or may not be desirable for a given situation. A sixth embodiment of the present invention is shown in Fig. 10. This air diffuser 620 is used in place of the air diffuser 20, illustrated in Fig. 1, for this embodiment. In this sixth embodiment, similar elements are similarly designated, but with 600 series numbers. The upper set of vanes 664 and the lower set of vanes 662 now extend radially into the main bore 652, with the upper set of vanes 664 shorter than the lower set 662 and tapered as they extend radially inward. The taper is done for the same potential interference reasons as with the first embodiment. The radially oriented vanes 662,664 can work as compared to parallel vanes, but are not generally as effective as with parallel spacing. The reason being that at throttle tip-in conditions, if the vane spacing is set to its maximum effectiveness at the outer radial locations of the vanes 662,664, the proper diffusion and redirection of the air flow may not be as effective at the inner radial locations since the ends of the fins approach one another as they extend radially inward, thus changing the amount of gap between them. Fig. 11 illustrates a seventh embodiment of the present invention. This air diffuser 720 is used in place of the air diffuser 20, illustrated in Fig. 1, for this embodiment. In this seventh embodiment, similar elements are similarly designated, but with 700 series numbers. The upper set of parallel vanes and the lower set of parallel vanes are really now just one continuos set of vertical vanes 762, along with the addition of parallel horizontal vanes 68. This forms a full grid pattern of vanes. The thickness of these vanes is constant along the length of the vanes. While the full grid pattern is most effective for diffusing and redirecting the air flow and thus for attenuation of the noise, there are very substantial flow losses created due to the significant amount of blockage of the main bore 752. This blockage will thus significantly reduce the maximum horsepower of the engine. Fig. 12 illustrates an eighth embodiment of the present invention. This air diffuser 820 is used in place of the air diffuser 20, illustrated in Fig. 1, for this embodiment. In this eighth embodiment, similar elements are similarly designated, but with 800 series numbers. This embodiment employs the same parallel vertical vanes 862 as in the seventh embodiment, but without the addition of horizontal vanes. This is a compromise from the seventh embodiment, in that the noise attenuation will not be as great, but the blockage will also be less. For both the seventh and eighth embodiments, one must keep in mind that the location of the butterfly valve in the throttle body is important because of the potential for interference between the grid or line pattern and an edge of the valve when the valve is certain open positions.

Claims: A method of reducing noise emanating from the intake system of a fuel injected internal combustion engine having an intake throttle (28), an intake manifold (24), and fuel injectors for injecting fuel into the intake air downstream of the intake throttle, which method comprises placing in the intake system downstream of the intake throttle and upstream of the fuel injectors a diffuser (20,220,320,420,520,620,720,820) comprising a set of vanes (62,64,262,264,362,364,462,464,562,564,662,664,762,68,862) which are spaced from one another in a plane transverse to the direction of the intake air flowing through the diffuser and which protrude into the path of the intake air, the vanes being operative to reduce noise by introducing into the intake air stream counter-rotating vortices of turbulence. An air intake system for a fuel injected internal combustion engine including a throttle body (22), an air intake manifold (24), and an air diffuser (620) comprising a flat plate portion and arranged in the intake manifold downstream of the throttle body and upstream of the fuel injectors for reducing noise emanating from the intake system by introducing turbulence into the air stream passing through the throttle body, the air diffuser (620) having a main bore (652) defined by a bore wall and a set of vanes (662,664) spaced from one another across the bore (652) and extending from a portion of the bore wall into the main bore (652). An air intake system for a fuel injected internal combustion engine including a throttle body (22), an air intake manifold (24), and an air diffuser arranged in the intake manifold downstream of the throttle body and upstream of the fuel injectors for reducing noise emanating from the intake system by introducing turbulence into the air stream passing through the throttle body, the air diffuser (20,220, 320,420,520,720,820) having a main bore (52,252,352,526,752) defined by a bore wall; and a plurality of vanes (264,364,464,564,68, 86) forming a first set, spaced from one another and extending parallel to one another from a portion of the bore wall into the main bore (52,252,352,526,752). An air intake system as claimed in claim 3, further including a plurality of vanes (62,262,362,462,562, 762) forming a second set of vanes, spaced from one another and extending parallel to one another from a different portion of the bore wall than the first set into the main bore. An air intake system as claimed in claim 4, wherein the average length of the first set of vanes (64, 264,364,464,564,68, 862) is shorter than the second set of vanes (62,262,362,462,562, 762). An air intake system as claimed in any of claims 3 to 5, wherein the vanes (464) of the first set taper as they extend away from the bore wall. An air intake system as claimed in any of claims 3 to 6, wherein the vanes (64) in the first set and the vanes (62) in the second set are parallel to one another on opposite sides of the bore wall. An air intake system as claimed in claim 4, wherein the air diffuser comprises a flat plate portion mounted between the throttle body (22) and the intake manifold (24) forming said main bore (52,252,652,752). An air intake system as claimed in claim 3, wherein the first set of vanes (862) extend all of the way across the main bore, each vane connecting to two locations of the bore wall. An air intake system as claimed in claim 8, wherein the flat plate portion has an upstream face and a downstream face and the vanes (64) in the first set of vanes extend beyond the face of one of the upstream face and the downstream face. An air intake system for a fuel injected internal combustion engine including a throttle body (22), an air intake manifold (24), and an air diffuser arranged in the intake manifold downstream of the throttle body and upstream of the fuel injectors for reducing noise emanating from the intake system, the air diffuser (720) having a main bore (752) defined by a bore wall, a plurality of vanes (762) forming a first set, spaced from one another and extending parallel to one another from a portion of the bore wall into the main bore (752) and a second set of vanes (68) that extend transversely to the vanes (762) of the first set to define a full grid pattern of vanes.

Inventors: CHOI MICHAEL, CHOI, MICHAEL
Applicants: FORD GLOBAL TECH INC, FORD GLOBAL TECHNOLOGIES, INC.
Application year: 1998
Main classification: F02M29
IPC codes: F02D9, F02M35, F02M33