Variable resonator

Abstract: A resonator provided for air system that includes a body defining a passageway. A wall is disposed within the chamber and the wall and the chamber are movable relative to one another to define a length and a volume of the cavity. The length and the volume of the cavity define a noise attenuating frequency. By moving the wall and chamber relative to one another the noise attenuating frequency may be changed as the frequency changes during the engine operation. The drive mechanism moves the wall in the chamber relative to one another to change the noise attenuating frequency. The chamber may be a branched type resonator or an inline type resonator. Accordingly, the above described invention provides a resonator that may be adjusted during engine operation to attenuate noise over a variety frequencies.

Description: BACKGROUND OF THE INVENTION This invention relates to a resonator for air induction system, and more particularly, the invention relates to a quarter wave tube having a variable length and volume. Internal combustion engines produce undesirable induction noise which adversely affects the output torque and volumetric efficiency of the engine. The induction noise produced by the engine depends on the particular engine configuration and is affected by such factors as the number of cylinders, the volume and shape of the intake manifold plenum and intake runners, and other induction system parameters. The induction noise is caused by a pressure wave that travels from the combustion chamber towards the inlet of the air induction system. The induction noise may be reduced and the engine performance improved by producing a wave traveling in the direction of the combustion chamber 180 degrees out of phase of the noise wave. To this end, noise attenuation devices such as quarter wave tubes have been developed. A prior art quarter wave tube is shown in Figure 1. The induction system includes a body 10 such as a zip tube which defines a passageway 12. The quarter wave tube 14 is in fluid communication with the passageway 12. A quarter wave tube produces a noise canceling wave of a frequency that is one quarter the length of the quarter wave tube 14. Typically, quarter wave tubes are of a fixed length and therefore are designed for a particular frequency. Air induction noise is typically concentrated about several different engine orders or operating conditions of the engine. Additionally, the noise frequency changes as the engine speed changes. Since space is limited under the hood of the vehicle, quarter wave tubes are only provided for the most undesirable noise frequencies and the other noise frequencies are not attenuated. Therefore, what is needed is a quarter wave tube or a group of quarter wave tubes that can change to accommodate the changing noise frequencies during engine operation so that a greater amount of air induction noise may be attenuated. DE-4305333 describes a silencing arrangement for reducing port noise in systems with pulsating gas flows. A Helmholtz resonator is connnected to a gas flow passage and the resonator volume can be continuously varied so as to be inversely proportional to the gas flow pulsation frequency over the operating range of the system. SUMMARY OF THE INVENTION AND ADVANTAGES The present invention provides a resonator for air system that includes a body defining a passageway. A wall is disposed within the chamber and the wall and the chamber are movable relative to one another to define a length and a volume of the cavity. The length and the volume of the cavity define a noise attenuating frequency. By moving the wall and chamber relative to one another the noise attenuating frequency may be changed as the noise frequency changes during the engine operation. The drive mechanism moves the wall and the chamber relative to one another to change the noise attenuating frequency. The chamber may be a branched-type resonator or an inline-type resonator. Accordingly, the above described invention provides a resonator that may be adjusted during engine operation to attenuate noise over a variety frequencies. BRIEF DESCRIPTION OF THE DRAWINGS Other advantages of the present invention can be understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein: Figure 1 is a cross-sectional view of a quarter wave of the prior art; Figure 3A is a cross-sectional view of another embodiment of the present invention; Figure 3B is a cross-sectional view of the resonator shown in Figure 3A taken along line 3B-3B; Figure 3C is a cross-sectional view of the resonator shown in Figure 3A taken along line 3C-3C; Figure 4A is a cross-sectional view of another embodiment of the present invention; Figure 4B is an end view of the body shown in Figure 4A; Figure 5 is a cross-sectional view of another resonator of the present invention for use in attenuating multiple engine order noise frequencies; Figure 6 is an alternative embodiment of the present invention; and Figure 7 is a cross-sectional view of the preferred embodiment of the present invention used in attenuating noise for multiple engine orders. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An inline-type resonator is shown in Figures 3A-3C. The chamber 18 is in the shape of a barrel 28 and includes circular turns 30. The turns 30 are separated by walls 32 and are fluidly connected by an opening 34. In this manner, the tuner 16 may be wrapped around the body 10 to provide a long tuner in a relatively small space. The barrels 28 may be injection molded in two halves and then welded about the body 10, or they may be formed in another suitable manner. Referring to Figure 3B, the air travels from the passageway 12 of the body 10 through an outlet 21 and into the cavity portion 18a of a first turn 30a. The air flow is directed through the portion 18a by a wall 22. The air flow travels through the portion 18a and is directed through an opening 34 by a divider 35. The air flow then enters a second turn 30b and into a portion 18b where the air flow reflects back a noise attenuating wave into the body 10. The length of this barrel shaped tuner may be adjusted by rotating the barrel 28 about the body 10 with the drive mechanism 24. As a result, the divider 35 moves away from the wall 22 thereby shortening the length of the portion 18a and the overall length in the tuner 16. The tuner 16 may also include a spacer 36 to space the turns of the barrel 28 away from the body 10 to lengthen the tuner and reduced the number of turns 30 required about the body 10. The body 10 may include any number of outlets 21 that are directed to separate chambers 18 for attenuating multiple noise frequencies simultaneously. The body 10 may include outlets 21a, 21b, 21c, as shown in Figure 4B, to attenuate the three noise frequencies at the same time. The spacing of the turns 30 of the barrels 28 from the body 10 may be staggered for each noise frequency to be attenuated as shown in Figure 5. It is to be understood that the body 10 may instead be rotated relative to the barrels 28 by the drive mechanism 24, as shown in Figure 6. Rotating body 42 is disposed within the barrels 28 and is connected to stationary bodies 40 at joints 43. The drive mechanism 24 is connected to the rotating body 42 to drive the rotating body 42 within the barrels 28. The most preferred embodiment is shown in Figure 7. The tuner 16 is designed to attenuate noise for a four cylinder, four stroke engine. Primary orders of noise for a four stroke engine occur at a second, fourth, sixth, and eighth order frequencies. The noise frequencies over those orders vary with engine speed and is shown in the following table. frequency of order (Hz) Engine Speed 2 nd 4 th 6 th 8 th 1000 33 66 100 133 6000 200 400 600 800 Each engine order produces a higher frequency noise. As the engine speed increases the noise frequency increases. Accordingly, it is desirable to have a tuner for each engine order. It is also desirable to have the tuner for each engine order to be of a variable length so that as the engine speed increases the tuner length may be adjusted to attenuate the noise. Through experimentation or calculation the following tuner dimensions may be determined. Length of tuner to reduce the frequency (mm) Engine Speed 2 nd 4 th 6 th 8 th 1000 2575 1289 850 639 6000 425 212 141 106 To achieve the maximum length, the tuner 16 may be wrapped around the body 10 as needed. As the engine speed increases the tuner length must be decreased so that higher frequency noise may be attenuated. A nominal barrel diameter for each of the tuners may also be determined. Nominal barrel diameter for each order (mm) 2 nd 4 th 6 th 8 th 204 204 135 204 Barrel 28a is the tuner for the 8 th engine order, barrel 28b is the tuner for the 4th engine order, barrel 28c is the tuner for the 2 nd engine order, and barrel 28d is the tuner for the 6 th engine order. The barrels 28 are connected to one another so that as the drive mechanism 24 rotates all the barrels 28 relative to the body 10. However, it is to be understood that each barrel 28 may have a separate drive mechanism 24 so that they may be rotated independently of one another. The invention has been described in an illustrative manner, and it is to be understood that the terminology that has been used is intended to be in the nature of words of description rather than of limitation. Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

Claims: A resonator for an air induction system comprising: a body (10) defining a passageway (12); a chamber (18) having a cavity (20) in fluid communication with said passageway; a wall (22) disposed within said chamber with said wall and said chamber movable relative to one another to define a length and a volume of said cavity, said length and said volume of said cavity defining a noise attenuating frequency; and a drive mechanism (24) for moving said wall and said chamber relative to one another to change said noise attenuating frequency; wherein said chamber (18) wraps about said body (10) to form a plurality of turns (30) and wherein said chamber and said body rotate relative to one another. The resonator according to claim 1, wherein said chamber (18) extends transversely from said body (10). The resonator according to claim 2, wherein said wall (22) is an end wall of said chamber that moves along said length relative to said chamber (18). The resonator according to claim 1, wherein said turns (30) are connected by an opening (34). The resonator according to claim 1, wherein said wall (22) extends from said body (10) and a divider (35) extends from said chamber with said divider moving relative to said wall (22) to derive said length and said volume of said cavity. The resonator according to claim 1, further including a plurality of separate chambers (18) for attenuating noise at a plurality of engine orders. A method for attenuating noise at various frequencies in an air induction system of an engine, the method comprising the steps of: sensing an engine speed; and determining a desired resonator cavity length and volume for the engine speed; wherein said chamber (18) wraps about said body (10) to form a plurality of turns (30); and wherein an air tube (12) and a resonator chamber (18) are rotated relative to one another to change the length and the volume of the resonator cavity.

Inventors: STUART PHILIP EDWARD ARTHUR, STUART, PHILIP EDWARD ARTHUR
Applicants: SIEMENS VDO AUTOMOTIVE INC, SIEMENS VDO AUTOMOTIVE INC.
Application year: 2000
Main classification: F02M35
IPC codes: F02M35