Patent Publication Number: US-6698390-B1

Title: Variable tuned telescoping resonator

Description:
FIELD OF THE INVENTION 
     The invention relates to a resonator and more particularly to a variable tuned telescoping resonator for control of engine induction noise in a vehicle wherein the connector length and volume of the resonator are varied simultaneously. 
     BACKGROUND OF THE INVENTION 
     In an internal combustion engine for a vehicle, it is desirable to design an air induction system in which sound energy generation is minimized. Sound energy is generated as fresh air is drawn into the engine. Vibration is caused by the intake air in the air feed line which creates undesirable intake noise. Resonators of various types such as a Helmholtz type, for example, have been employed to reduce engine intake noise. Such resonators typically include a single, fixed volume chamber for dissipating the intake noise. Additionally, multiple resonators are frequently required to attenuate several noise peaks of different frequencies. 
     Desired noise level targets have been developed for a vehicle engine induction system. When engine order related inlet orifice noise targets are specified to be within narrow limits as a function of engine speed, the target line often cannot be met with a conventional multi-resonator system. The typical reason is that conventional resonator systems provide an attenuation profile that does not match the profile of the noise and yields unwanted accompanying side band amplification. This is particularly true for a wide band noise peak. The result is that when a peak value is reduced to the noise level target line at a given engine speed, the amplitudes of adjacent speeds are higher than the target line. Thus, the resonators are effective at attenuating noise at certain engine speeds, but ineffective at attenuating the noise at other engine speeds. 
     It would be desirable to produce a resonator which is variable tuned to militate against the emission of sound energy caused by the intake air at a wide range of engine speeds. 
     SUMMARY OF THE INVENTION 
     Consistent and consonant with the present invention, a variable tuned telescoping resonator which militates against the emission of sound energy caused by the intake air at a wide range of engine speeds, has surprisingly been discovered. 
     The variable tuned resonator system comprises: 
     an inner telescoping section adapted to provide fluid communication with a duct, the inner telescoping section defining a resonator connector length; and 
     an outer telescoping section surrounding the inner telescoping section to define a chamber therebetween, the inner telescoping section and the outer telescoping section being selectively extensible and collapsible to thereby change at least one of a volume of the chamber and the resonator connector length; 
     wherein changing the at least one of the volume of the chamber and the resonator connector length facilitates attenuation of a desired frequency of sound entering the resonator. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above, as well as other objects, features, and advantages of the present invention will be understood from the detailed description of the preferred embodiments of the present invention with reference to the accompanying drawings, in which: 
     FIG. 1 is a perspective view of a variable tuned telescoping resonator shown in the extended position, with the resonator mounted on a duct and the resonator shown in section, incorporating the features of the present invention; 
     FIG. 2 is a perspective view of the variable tuned telescoping resonator illustrated in FIG. 1 shown in the collapsed position, with the resonator shown in section; 
     FIG. 3 is a partial sectional view of the variable tuned telescoping resonator illustrated in FIG. 1 with helical springs for sequencing of the telescoping segments; 
     FIG. 4 is a partial sectional view of the variable tuned telescoping resonator illustrated in FIG. 1 showing an alternate embodiment for sequencing the telescoping segments using leaf type springs; 
     FIG. 5 is a schematic diagram of the variable tuned telescoping resonator illustrated in FIG. 1 with a control system for controlling the volume and connector length of the resonator at different engine speeds; 
     FIG. 6 is a graph showing a plot of the sound pressure level (SPL) in decibels vs. engine speed in RPM for noise emission without a resonator, noise emission with a one liter volume resonator, noise emission with a two liter volume resonator, and a target level for noise emission; and 
     FIG. 7 is a schematic diagram of an alternate embodiment of the invention showing a resonator including an inner telescoping member operably coupled with a piston. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings, and particularly FIG. 1, there is shown generally at  10  a variable tuned telescoping resonator shown in the expanded position for use in a vehicle air intake system (not shown). The resonator  10  is mounted on and in fluid communication with a duct  12  which is in communication with the vehicle air intake system. A connector  14  attaches the resonator  10  with the duct  12 . The connector  14  has a neck length  16  and a neck diameter  18 . 
     The resonator  10  includes a hollow main housing  20 . Disposed within the housing  20  are an inner telescoping section  22  and an outer telescoping section  24 . In the embodiment shown, five distinct inner telescoping segments  25   a  are included in the inner telescoping section  22  and five distinct outer telescoping segments  25   b  are included in the outer telescoping section  24 . It is understood that additional or fewer telescoping segments  25   a ,  25   b  could be used to arrive at a desired connector length and volume without departing from the scope and spirit of the invention. Additionally, one of the functions of the housing  20  is to provide stops to limit the movement of the telescoping segments  25   a ,  25   b . It is understood that other internal or external stops could be used to replace the housing  20  without departing from the scope and spirit of the invention. 
     The inner telescoping section  22  defines an inner chamber  26  and the outer telescoping section  24  cooperates with an outer wall of the inner telescoping section  22  to define an outer;chamber  28 . Together, the inner chamber  26  and the outer chamber  28  define the hollow interior of the resonator  10  volume. A first end  30  of the inner telescoping section  22  communicates with the connector  14  of the resonator  10 . A second end  32  of the inner telescoping section  22  is open to the outer chamber  28 . A first end  34  of the outer telescoping section  24  is spaced radially from the first end  30  of the inner telescoping section  22  and adjacent an inner wall of the housing  20 . A second end  36  of the outer telescoping section  24  is spaced radially and longitudinally from the second end  32  of the inner telescoping section  22  and adjacent the inner wall of the housing  20 . The second end  36  of the outer telescoping section  24  is closed to form the outer chamber  28  within the outer telescoping section  24 . 
     A plurality of radial struts  38  are disposed between and connect each adjacent inner telescoping segment  25   a  and outer telescoping segment  25   b . A plurality of helical springs  40  is disposed between each adjacent outer telescoping segment  25   b , as illustrated in FIG.  3 . Alternatively, a plurality of leaf type springs  42  is disposed to abut the inner telescoping segments  25   a  and the radial strut  38  of the adjacent inner telescoping segment  25 a, as illustrated in FIG.  4 . It is understood that other spring types, configurations, and locations could be used without departing from the scope and spirit of the invention. A stop tab  44  extends radially outwardly from an outer surface of each of the outer telescoping segments  25   b . Three tabs  44  are spaced circumferentially at 120 degrees apart in the embodiment shown. The tab  44  is disposed in a slot  45  as clearly shown in FIGS. 1 and 2. Inner o-rings  46  are disposed between adjacent inner telescoping segments  25   a  and outer o-rings  48  are disposed between adjacent outer telescoping segments  25   b . FIG. 2 shows the telescoping sections  22 ,  24  in the collapsed position, which can be attained using a motive driver connected to a linkage, an example of which is shown schematically in FIG.  5 . It is also understood that the linkage can be received in and guided by an aperture in a wall of the housing  20 , for example. 
     Referring now to FIG. 5, there is shown a schematic diagram of the resonator  10  including a control system  52  for controlling the extending and collapsing of the telescoping sections  22 ,  24 . By controlling the telescoping sections  22 ,  24 , the resonator volume  54  (volume of the outer chamber  28 ) and resonator connector length  56  (the neck length  16  of the connector  14  plus the length of the inner telescoping section  22 ) are controlled at different vehicle engine speeds. A programmable control module or PCM  60  is electrically connected to a motor  62 . The motor  62  is drivingly engaged with a rack and pinion type actuator  64 . It is understood that other actuator types may be used without departing from the scope and spirit of the invention. The rack portion of the rack and pinion actuator  64  is connected to the resonator  10  such that the resonator volume  54  and the resonator connector length  56  can be selectively varied as desired. A position sensor and transmitter  66  provides positional feedback to the PCM  60  from the resonator  10 . An engine speed sensor and transmitter  68  senses and transmits engine speed to the PCM  60 . The PCM  60  accesses a PCM table  70  to find a required position for the resonator  10  based upon engine speed. The required position of the resonator  10  is then compared with the positional feedback from the position sensor and transmitter  66 . If the positional feedback differs from the required position, a position adjustment is made by the PCM  60  by operating the motor  62  to adjust the rack and pinion actuator  64  as needed. It is understood that other structures could be used to vary the resonator volume  54  and the resonator connector length  56  such as a stepper motor, for example. 
     In operation, air travels through the duct  12 . Sound generated by the vehicle engine travels through the duct  12  and enters the resonator  10  through the connector  14 . A sound frequency generated by the engine differs at different engine speeds. Therefore, in order to meet target sound pressure levels, the resonator  10  is required to attenuate a wide range of frequencies. This is accomplished by varying the resonator connector length  56  and the resonator volume  54 . The inner telescoping section  22  acts as an adjustable extension to the connector  14  and thereby permits adjustment of the resonator connector length  56 . Adjustment of the length of the outer telescoping section  24  permits adjustment of the resonator volume  54 . Simultaneous adjustment of the inner telescoping section  22  and the outer telescoping section  24  facilitates fine tuning of the resonator  10  over a wide range of frequencies. Thus, the desired attenuation of sound emitted from the vehicle engine over a wide range of frequencies is accomplished. It is understood that the inner telescoping section  22  and the outer telescoping section  24  can be independently adjusted without departing from the scope and spirit of the invention. 
     The method of controlling the resonator  10  by the PCM  60  is accomplished by first mapping the characteristics of the resonator  10  at various telescoping positions at each engine speed. The resonator position versus engine speed is organized into the PCM table  70 . The resonator positions are determined by comparing the difference between base and target characteristics at each engine speed to a map of resonator performance. The resonator position which best meets the target at each engine speed is organized into the PCM table  70 . It should be noted that to achieve the best efficiency, the resonator  10  should be placed in the air induction system of the vehicle where it will most efficiently attenuate the frequencies of interest. For example, the chosen location should not be near a pressure nodal point of the frequencies of interest, but at a location where the standing wave pressures for the frequencies of interest are values which would provide reasonable attenuation. 
     The resonator  10  can be precisely controlled by controlling the repeatability of the telescoping motion of the inner telescoping section  22  and the outer telescoping section  24 . To be repeatable, the telescoping motion of the inner telescoping section  22  and the outer telescoping section  24  in each section must occur in the same sequence when extending or contracting. The position of each of the telescoping segments  25   a ,  25   b  must be the same when in the extending or the contracting mode. The repeatability is accomplished using two distinct methods. First, the axial position of the telescoping segments  25   a ,  25   b  is maintained by the radial struts  38 . Second, in the embodiments using the springs  40  and the springs  42 , the spring constant of the springs  40  and the springs  42  are designed so that the compression force required to move each of the telescoping segments  25   a ,  25   b  adjacent the first ends  30 ,  34  of the telescoping sections  22 ,  24 , respectively, is an order of magnitude higher than the frictional forces generated by the o-rings  46 ,  48  of the telescoping segments  25   a ,  25   b  adjacent the second ends  32 ,  36  of the telescoping sections  22 ,  24 , respectively. Additionally, the tab  44  militates against the telescoping segments  25   a ,  25   b  from extending beyond a desired telescoping position. 
     FIG. 6 illustrates the attenuation characteristics of fixed volume resonators. Curve A shows the sound pressure level or SPL in decibels without a resonator. Curve B shows the SPL with a 1.0 liter volume resonator. Curve C shows the SPL with a 2.0 liter volume resonator. Line D shows a target SPL. Fixed volume resonators provide a notch type attenuation with side band amplification that does not match the attenuation required to reduce a noise peak to a specific target line. As illustrated by curve B in FIG. 6, a low volume 1.0 liter resonator attenuates the SPL at 4500 rpm to near the target line D, but the remainder of curve B remains above the target line D. As the resonator gets larger, providing more attenuation, the attenuation bandwidth and notch depth increases. For the 2.0 liter resonator, the curve C is equal or below the target line D from 4000 to 5000 rpm. However, the side band amplification  80  of the 2.0 liter resonator is increased compared to the side band amplification  82  of the 1.0 liter resonator. As FIG. 6 illustrates, notch type attenuation does not provide the degree of control required to meet a specific target line. 
     The resonator  10  minimizes the problems associated with the fixed volume or notch type attenuation resonator, since at each engine speed the resonator  10  can be set to a desired telescoping position to provide the required attenuation. Additionally, where part of the noise curve lies below the target line D, amplification can be provided in the side band amplification region of the SPL curve to reach the target line D as desired. 
     An alternate embodiment of the invention is illustrated in FIG. 7. A resonator  90  includes a main housing  91  is connected to a duct  92  by a connector  94 . A first end  96  of an inner telescoping section  98  communicates with the connector  94 . A second end  100  of the inner telescoping section  98  is coupled to a piston  102  which cooperates with the inner walls of the housing  91  to form a resonator chamber  104 . The inner telescoping section  98  cooperates with the connector  94  to define a resonator connector length. A seal  106  is disposed between an outer wall of the piston  102  and the inner wall of the housing  91 . An actuator assembly  108  operatively connects the piston  102  with a motor  110 . 
     In operation, the position of the piston  102  is varied to vary a volume of the resonator chamber  104 . As the piston  102  is caused to move towards the connector  94 , the volume of the resonator chamber  104  is decreased. As the piston  102  is caused to move away from the connector  94 , the volume of the resonator chamber  104  is caused to increase. The inner telescoping section  96  is likewise caused to move with the piston  102 . As the piston  102  is caused to move towards the connector  94 , the inner telescoping section  98  is caused to collapse, thereby decreasing the resonator connector length. As the piston  102  is caused to move away from the connector  94 , the inner telescoping section  98  is caused to extend, thereby increasing the resonator connector length. Thus, by controlling the piston  102  and the inner telescoping section  98  to vary the volume of the resonator chamber  104  and the resonator connector length as described for the other embodiments of the invention, the resonator  90  is effective to control a wide range of sound frequencies. It should be noted that the piston  102  can be used with a resonator having a fixed resonator connector length without departing from the scope and spirit of the invention. 
     From the foregoing description, one ordinarily skilled in the art can easily ascertain the essential characteristics of this invention and, without departing from the spirit and scope thereof, can make various changes and modifications to the invention to adapt it to various usages and conditions.