Patent Publication Number: US-2003230272-A1

Title: Valve actuation inlet noise control system

Description:
REFERENCE TO RELATED APPLICATIONS  
     [0001] The present invention claims priority to U.S. Provisional Patent Application No. 60/389,585, filed Jun. 18, 2002. 
    
    
     
       TECHNICAL FIELD  
       [0002] The present invention relates to noise control systems, and more particularly to a system that controls noise in a valve actuation inlet for an engine.  
       BACKGROUND OF THE INVENTION  
       [0003] There are currently engines designed to operate in two or more modes where different numbers of cylinders are fired during each mode. For purposes of illustration only, the example shown in the figures and described below addresses an engine having eight cylinders and that operates in two modes, one using all eight cylinders and one using only four out of the eight cylinders. However, the description below is applicable to any engine having any number of cylinders and any number of operating modes with any number of cylinders switched on and off.  
       [0004] During a low power mode, four out of the eight cylinders may be operated, creating an engine sound having predominantly low frequency components. In one embodiment, the signature of the engine noise is predominated by the firing frequency of the engine, which is around twice the engine rotational speed. Typically, the frequency range during this mode is around 33 to 170 Hz as the engine runs from idle to 5000 rpm.  
       [0005] When the engine mode is operated in a high power mode, where all eight cylinders are operating, the additional cylinders change the engine noise characteristic by increasing the frequency to, typically, four times the engine speed (e.g., around 100 to 400 Hz in the primary engine firing range).  
       [0006] However, currently known noise control systems are not able to adapt their noise control properties to handle the noise characteristic of different engine operating modes. This causes significant noise character changes as the engine mode switches while the noise control system does not follow suit.  
       [0007] There is a desire for a noise reduction system that can reliably control noise in an engine having more than one operating mode generating different noise characteristics.  
       SUMMARY OF THE INVENTION  
       [0008] The present invention is directed to an engine noise control system that controls engine noise in multiple engine operating modes by controlling a size of an air inlet with a movable valve. An actuator moves the valve between an open position and a closed position depending on the engine operating mode.  
       [0009] In one embodiment, the actuator is coupled to an engine cylinder de-activation unit to link the valve operation to the engine operating mode. When the engine is operating in a low-power mode, which requires less air, the actuator moves a cable drive, which rotates an actuation lever that turns the valve into a closed position. When the engine is operating in a high-power mode, the actuator moves the cable drive to move the valve to an open position. Because the valve actuator is coupled to the engine cylinder de-activation unit, valve operation is directly linked to the engine operating mode instead of secondary characteristics (e.g., air flow characteristics).  
       [0010] By restricting air flow when the engine is in the low-power mode and choking off excess air that could carry engine noise, the invention attenuates low frequency noise generated by engine during the low-power mode. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0011]FIG. 1 is a representative diagram of a noise control system according to one embodiment of the invention;  
     [0012]FIG. 2 illustrates the inventive system reducing noise during a first engine operating mode;  
     [0013]FIG. 3 illustrates the inventive system reducing noise during a second engine operating mode; and  
     [0014]FIG. 4 illustrates the system of FIG. 1 according to one embodiment of the invention in greater detail.  
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS  
     [0015]FIG. 1 is a representative diagram of a noise control system  100  according to one embodiment of the invention. In this example, the system  100  is used with an engine that can operate in a low power mode where four cylinders are operated and a high power mode where all eight cylinders are operated. The inventive noise control system  100  can be used in other modes and engine configurations without departing from the scope of the invention.  
     [0016] The system  100  in this embodiment is designed to cooperate with an air cleaner  102  having an air inlet  104  divided into two sections  106 ,  108 . Note that in this embodiment, there is no physical barrier between the two sections  106 ,  108 . An air outlet  110  connected to the air cleaner  102  allows air to flow from the air cleaner  102  to the engine (not shown).  
     [0017] The system  100  includes a valve  112  movably disposed in one of the sections (the second section  108  in this example). An actuator  114  connected to the valve  112  opens and closes the second section  108 , causing the air inlet  104  to be made larger or smaller depending on the operating mode of the engine. In one embodiment, the actuator  114  also is coupled to a cylinder de-activation unit in the engine, causing the valve  112  operation to coincide with the change in engine mode.  
     [0018]FIGS. 2 and 3 are representative diagrams of the inventive system  100  during two different operational modes. If the engine is operating at a low power mode (FIG. 2), with fewer than all of the engine cylinders firing, then the actuator  114  moves the valve  112  to a closed position  112   a,  effectively making the air inlet  104  smaller. Note that the actual size of the air inlet  104  stays the same, but the effective cross-sectional area of the air inlet  104  is smaller when the valve  112  is closed  112   a.  The smaller cross-section increases air flow restriction; however, the engine only requires approximately half of the air flow at a given engine speed in this case because it is operating in four cylinder mode instead of eight cylinder mode, thus reducing the amount of air flowing into the air cleaner  102 . This reduced air inlet  104  cross-section increases the ratio between the duct area  120  and the air cleaner area  122 , causing the overall noise level to drop since the expansion ratio between the duct area  120  and the air cleaner area  122  increases noise attenuation.  
     [0019] If the engine is running in a high power mode (e.g., with all eight cylinders), the engine will generate higher frequency noise. The actuator  114  will move the valve  112  to its open position  112   b,  allowing air to flow through substantially the entire cross-sectional area of the air inlet  104 . Because higher frequency noise has shorter wavelengths than lower frequency noise, it is easier to attenuate. In the illustrated example, the shorter wavelength of the higher frequency noise is shorter than the length of the air cleaner  102 , allowing better attenuation to be achieved. Further, the engine draws more air during the high-power mode than during the low-power mode; therefore, fully opening the valve  112  allows the maximum amount of power to be generated by the engine. By recognizing that the engine does not require as much air in the low-power mode as in the high-power mode, the valve  112  can adjust air flow to provide the maximum amount of air to the engine at each mode while maximizing noise attenuation to reduce low-frequency noise generated during the low-power mode.  
     [0020]FIG. 4 illustrates one embodiment of the inventive system in more detail. In this embodiment, the actuator  114  is connected to a cylinder deactivation unit  200 , which controls the engine operating mode by activating and deactivating cylinders in the engine (not shown). Translation of the actuator  114  moves a first end housing  202  of a cable drive  204 . The cable  204  can be any cable that can transmit either tensile or compressive loads, such as a Bowden cable or a sleeved flexible cable. In one embodiment, the first end  202  is disposed near the cylinder deactivation unit  200  and attached to the engine (not shown) or an inlet manifold (not shown). When the cylinder deactivation unit  200  deactivates selected cylinders in the engine to change the operating mode, the unit  200  also causes the actuator  114  to move in the direction of arrow A to push against the first end  202 .  
     [0021] When the actuator  114  pushes against the first end  202 , the compressive force in the cable  204  is translated to a second, movable end housing  206  attached to the other end of the cable  204 . Movement of the second end  206  is translated by an actuation lever  208  to rotate a valve actuation shaft  210 , which in turns rotates the valve  112 . A return spring  212  has a biasing force to maintain the valve  112  in the closed position or open position, depending on the operational direction of the actuator  114 . For example, if the actuator  112  operates to open the valve  112 , then the return spring  212  is biased to pull the valve  112  shut. In other words, the return spring  212  is biased in a direction opposite the operational direction of the actuator  114 . Because the valve actuator  114  operation is linked directly to the cylinder deactivation unit  200  operation, the inventive system integrates the mode switching with the noise control mechanism instead of responding to secondary criteria, such as air flow characteristics.  
     [0022] As a result, the invention provides a simple, inexpensive system that can reduce engine noise even if the engine runs at different modes. By adjusting the air flow according to the engine&#39;s air consumption needs during a given mode, the invention maximizes the air flow to the engine while maximizing noise attenuation, thus producing minimum noise at the air inlet orifice.  
     [0023] It should be understood that various alternatives to the embodiments of the invention described herein may be employed in practicing the invention. It is intended that the following claims define the scope of the invention and that the method and apparatus within the scope of these claims and their equivalents be covered thereby.