Abstract:
The present invention relates to a resonator for attenuating pressure pulsations received through an air passage. A piston-type member is located within a resonator chamber to define first and second volumes. A first port connects the air passage with the first volume, while a second port connects the air passage with the second volume. An actuator is configured to move the piston-type member thereby changing the first and second volumes. By changing the first and second volumes and selectively connecting them to the air passage, the frequency range attenuated by the resonator can be adjusted.

Description:
BACKGROUND  
       [0001]     1. Field of the Invention  
         [0002]     The present invention generally relates to a resonator for dampening pressure pulsations from an engine.  
         [0003]     2. Description of Related Art  
         [0004]     Resonators for attenuating pressure pulsation in automotive applications are well known. Internal combustion engines produce undesirable induction noise in the form of pressure pulsations that adversely affect output torque and volumetric efficiency of the engine. The induction noise produced by the engine depends on the engine configuration and engine speed and is caused by a pressure wave that travels from the combustion chamber towards the inlet of the air induction system. This noise may be reduced by producing an attenuation wave traveling in the direction of the combustion chamber 180° out of phase with the noise wave. As such, Helmholtz type resonators have been used to attenuate the noise wave generated from combustion vehicles. In addition, more recently, resonators have been developed that change the volume of the resonator to adjust for varying frequencies of the noise wave as engine speed changes. Previous designs of resonators, however, have not provided a wide enough accommodation to attenuate for various noise frequencies of the engine.  
         [0005]     In view of the above, it is apparent that there exists a need for an improved resonator having broader flexibility to attenuate the various noise frequencies of the engine.  
       SUMMARY  
       [0006]     In satisfying the above need, as well as overcoming the enumerated drawbacks and other limitations of the related art, the present invention provides a resonator for attenuating pressure pulsations received through an air passage. The resonator includes a resonator chamber, first and second openings, first and second valves, a piston-type member, and an actuator or motion control device. The piston-type member is located within the resonator chamber and defines first and second volumes on opposing sides thereof. The first opening connects the air passage with the first volume, while the second opening connects the air passage with the second volume. Located in the first opening is the first valve, which selectively connects the first volume with the air passage. Similarly, the second valve is located in the second opening and selectively connects the second volume with the air passage. The motion control device is configured to move the piston-type member thereby changing the first and second volumes. By changing the first and second volumes and selectively connecting them to the air passage, the frequency range attenuated by the resonator can be adjusted.  
         [0007]     While the first valve is open, the motion control device moves the piston-type member to decrease the first volume as the rpm of the engine increases. As the vehicle transmission shifts, the rpm of the engine quickly changes. To accommodate the quick change in rpm, the first valve is closed and the second valve is opened. While the second valve is open, the motion control device is configured to decrease the second volume corresponding to an increase in the rpm of the engine. This process is continued as the car continues to shift during normal operation.  
         [0008]     Further objects, features and advantages of this invention will become readily apparent to persons skilled in the art after a review of the following description, with reference to the drawings and claims that are appended to and form a part of this specification. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]      FIG. 1  is an embodiment of a variable geometry dual volume Helmholtz resonator according to the present invention; and  
         [0010]      FIG. 2  is a plot of the active volume of the resonator with respect to the rpm of the engine. 
     
    
     DETAILED DESCRIPTION  
       [0011]     Now referring to  FIG. 1 , a resonator embodying the principles of the present invention is illustrated therein and designated at  10 . The resonator  10  generally includes a first port  12 , a first valve  14 , a second port  16 , a second valve  18 , a piston  22 , a first resonator volume  26 , a second resonator volume  28 , and an actuator or motion control device  24 .  
         [0012]     The intake manifold of an internal combustion engine is coupled to the inlet duct  15  such that air flows, as designated by arrows  17 , to the engine for use in the combustion process. As a result of the air induction process, pressure waves are generated that flow back up through the inlet duct  15 , producing unwanted noise.  
         [0013]     To attenuate this induction noise, the resonator  10  is located so as to be able to generate a wave that is 180° out of phase with the noise wave, and which can be varied in frequency so as to respond to frequency changes in the noise wave and thereby attenuate a greater variety of noise frequencies. To do this, the resonator  10  is in fluid communication with the inlet duct  15 . The inlet duct  15  is in fluid communication with the first resonator volume  26  through the first port  12 . The first valve  14  is located in the first port  12  and selectively connects the first volume  26  to the inlet duct  15 . Similarly, the inlet duct  15  is in fluid communication with the second resonator volume  28  through the second port  16 , and the second valve  18  is located in the second port  16  to selectively connect the second resonator volume  28  to the inlet duct  15 . The first and second valves  14 ,  18  are manipulated by a controller  29  and are preferably solenoid valves, although other common valves are contemplated and could readily be used.  
         [0014]     As mentioned above, the engine creates a pressure pulsation which flows back through the inlet duct  15  into the first or second resonator volumes  26 ,  28  of the resonator  10 . The resonator attenuates the pressure pulsation by reintroducing the pressure pulsation to the inlet duct  15  with a 180° phase shift, thereby producing a canceling effect.  
         [0015]     The resonator  10  includes a housing  20  that cooperate with a first surface  23  of the piston  22  to form the first resonator volume  26 . Similarly, a second surface  25  of the piston  22  cooperates with the housing  20  to form a second resonator volume  28  within the housing  20  on an opposing side of piston  22 . To allow adjustment of the first and second resonator volumes  26  and  28 , the piston  22  can be reciprocated and moved within the resonator  10 . The position of the piston  22  is adjusted by the motion control device  24 . The controller  29  manipulates the motion control device  24  to drive the piston  22  based on the speed of the engine, thereby adjusting the resonator volume being used to attenuate the pressure pulsation. In one embodiment, the motion control device  24  includes an electric motor  36  that drives a crank shaft  34 . The crank shaft  34  is connected to a rod  32  that protrudes into the resonator  10  through an end wall  33  thereof. The rod  32  is attached to the piston  22  at coupling  30  thereby allowing the motor  36  to manipulate the position of the piston  22 .  
         [0016]     During operation, if the first valve  14  is open thereby connecting the first volume  26  with the inlet duct  15 , the piston  22  is translated according to the engine speed to decrease the first volume  26  as the engine speed increases. Alternatively, as the engine speed decreases, the piston  22  is translated to increase the first volume  26 . Likewise, if the first valve  14  is closed and the second valve  18  is open connecting the second volume  28  with the inlet duct  15 , the piston  22  is moved to decrease the second volume  28  as the engine speed increases and to increase the second volume  28  as the engine speed decreases. The system switches between the first and second volumes to accommodate rapid or dramatic changes in the speed of the engine, such as when the transmission up-shifts or down-shifts.  
         [0017]     Now referring to  FIG. 2 , line  38  shows the speed (rpm) of the engine as the speed of the vehicle increases. The frequency of the pressure pulsation increases in relation to the rpm of the engine. During the period indicated by reference numeral  40 , the rpm increases along with the frequency of the pressure pulsation. At the time indicated by reference numeral  42 , the transmission of the vehicle up-shifts, thereby rapidly decreasing the rpm of the engine. Similarly, the frequency of the pressure pulsation quickly decreases with the rpm of the engine. To accommodate the sudden change in rpm, the resonator  10  is configured to selectively switch from one resonator volume to the other by opening or closing the first and second valves  14 ,  18 .  
         [0018]     For example, if at a low engine speed the first valve  14  is open. As the rpm increases during period  40 , the motion control device  24  moves piston  22  to decrease the first resonator volume  26  in conjunction with minor changes in the engine rpm. If the engine speed were to undergo a minor slow down, the piston  22  would be moved accordingly to increase the first resonator volume  26  correspondingly. When the engine shifts, indicated by reference numeral  42 , a dramatic engine speed change occurs. To accommodate this rapid change, the first valve  14  is closed and the second valve  18  is opened, thereby quickly coupling the inlet duct  15  a larger volume and thereby accommodating the lower engine rpm. During period  44 , the motion control device  24  again moves the piston  22  to reduce the second resonator volume  28  in accordance with the engine rpm until the next transmission shift occurs, as indicated by reference numeral  46 . At the next transmission shift, the second valve  18  may be closed and the first valve  14  opened, again quickly switching to the first resonator volume  26  that is appropriately sized for the lower engine rpm. The process may be continued as the transmission upshifts and downshifts during the normal operation of the vehicle.  
         [0019]     Although the system here is shown with two ports  12 ,  16  and one movable piston  22 , it is also envisioned that multiple openings and multiple members may be used in conjunction with each other to simultaneously address multiple frequency ranges. Further, the valves may be independently controllable to attenuate multiple frequency pressure pulsations in certain ranges.  
         [0020]     As a person skilled in the art will readily appreciate, the above description is meant as an illustration of implementation of the principles this invention. This description is not intended to limit the scope or application of this invention in that the invention is susceptible to modification, variation and change, without departing from spirit of this invention, as defined in the following claims.