Abstract:
A damping structure reduces chatter caused by shaft vibrations within a bearing bore in a manifold. The damping structure is incorporated into the shaft and has a resilient member and a contact member inside a shaft bore machined into the shaft. The contact member presses against the inside surface of the bearing bore, placing a load on the shaft that dampens chatter-inducing vibrations.

Description:
REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application claims priority to U.S. Provisional Appln. No. 60/297,399, filed Jun. 11, 2001, the disclosure of which is incorporated by reference in its entirety. 
     
    
     
       TECHNICAL FIELD  
         [0002]    The present invention relates to active manifolds, and more particularly to structures that minimize or prevent noise in a manifold.  
         BACKGROUND OF THE INVENTION  
         [0003]    Some automobile intake manifold designs use one or more shafts having butterfly valves attached to the shaft to control air flow within the manifold. Each shaft is usually installed into a bearing bore within the manifold body or through bushings disposed in the bearing bore. Clearances between the shaft and the bearing bore, however, create undesirable chatter due to air flow and air pressure fluctuations within the manifold.  
           [0004]    Although there have been proposed designs for reducing this chatter, current designs rely on incorporating damping structures into the manifold body. One proposed configuration places a spring-biased damping structure inside the manifold body so that it contacts the shaft and dampens shaft vibrations. Inserting a damping structure in the manifold body is often difficult, though, due in part to the configuration of the manifold body as well as the materials used to construct the manifold body.  
           [0005]    There is a desire for an improved structure that can dampen vibrations causing system chatter within the manifold.  
         SUMMARY OF THE INVENTION  
         [0006]    Accordingly, the invention is directed to a damping structure that reduces chatter caused by shaft vibrations within a bearing bore in a manifold. A damping structure having a resilient member and a contact member is placed inside a shaft bore machined into the shaft. The contact member is disposed between the resilient member and an inside surface of the bearing bore. The resilient member places a load on the shaft to minimize chatter.  
           [0007]    In one embodiment, the damping structure is held inside the shaft bore by a retainer. The retainer prevents the contact member and resilient member from falling out of the shaft bore. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    [0008]FIG. 1 is a cross-sectional diagram of a shaft disposed in a bearing bore according to one embodiment of the invention;  
         [0009]    [0009]FIG. 2 is a cross-sectional exploded diagram of a shaft structure according to one embodiment of the invention;  
         [0010]    [0010]FIG. 3 is a cross-sectional exploded diagram of a shaft structure according to another embodiment of the invention;  
         [0011]    [0011]FIG. 4 is a cross-sectional exploded diagram of a shaft structure according to a further embodiment of the invention. 
     
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS  
       [0012]    [0012]FIG. 1 generally illustrates one embodiment of the inventive damping structure. As noted above, an active manifold structure includes a shaft  10  disposed in a bearing bore  12  formed in a manifold body  14 . Optional bushings (not shown) may also be disposed inside the bearing bore  12 . The shaft  10  has one or more shaft bores  16  machined through the shaft&#39;s outer surface to a selected depth. In one embodiment, the shaft bore  16  extends only partially through the shaft  10  to ensure that any damping structure inserted into the shaft bore  16  will apply sufficient force to the shaft  10  to dampen vibrations. The shaft bore  16  can be formed anywhere on the shaft  10  as long as the shaft bore  16  opens to an inner surface of the bearing bore  12 .  
         [0013]    A resilient member  18  and a contact member  20  are disposed inside the shaft bore  16 . The contact member  20  is preferably positioned to contact both the manifold body  14  and the resilient member  18 , acting as an interface between the two. The resilient member  18  can be any resilient structure that can dampen shaft vibrations, such as a spring, a coil, a resilient plug, or any other similar structure. In one embodiment, the spring or coil is made from a metallic material. A polymer material may also be used to construct the resilient member  18 , such as glass fiber-reinforced nylon or other similar material.  
         [0014]    The contact member  20  may be made of any wear-resistant and/or self-lubricating properties, such as Teflon®, Delron®, Peek® or other similar materials. In one embodiment, the contact member  20  has a domed shape where the flat portion of the dome is attached to the resilient member  18  and the curved portion of the dome contacts the inner surface of the bearing bore  12 . Other contact member  20  configurations (e.g., cylindrical) may also be selected.  
         [0015]    Before the shaft  10  is placed inside the bearing bore  12 , the resilient member  18  and contact member  20  are placed inside the shaft bore  16 . The resilient member  18  may be compressed via retention pressure onto the contact member  20  so that the top of the contact member  20  does not interfere with the shaft&#39;s insertion into the bearing bore  12 . When the shaft  10  is placed into the bearing bore  12  and any retention pressure on the contact member  20  is released, the resilient member  18  decompresses slightly so that the contact member  20  contacts the inside surface of the bearing bore  12  and exerts a load on the shaft  10 . This load will dampen, and therefore minimize, any chatter caused by shaft movement within the bearing bore  12 .  
         [0016]    [0016]FIG. 3 illustrates an alternative embodiment of the inventive structure. This embodiment is designed to retain the resilient member  18  and contact member  20  within the shaft bore  16  during regular handling. In this embodiment, the contact member  20  has a retaining ledge  22  around its periphery, creating a nub  24 . A retainer  26  fits over the nub  26  and holds the contact member  20  and the resilient member  18  inside the shaft bore  16  via an interference fit between the retainer  26  and the shaft bore  16 . In one embodiment, the nub  24  portion of the contact member  20  moves freely inside the retainer  20  to absorb and dampen any shaft vibrations within the bearing bore  12 . This embodiment simplifies assembly of the shaft  10  into the manifold body  14  because the retainer  26  prevents the contact member  20  and resilient member  18  from falling out of the shaft bore  16  during manufacturing.  
         [0017]    [0017]FIG. 4 illustrates yet another embodiment of the inventive structure. In this embodiment, the resilient member  18  and contact member  20  are integrated together to form a unitary damping structure  28 . In one possible structure, the resilient member  18  and contact member  20  are manufactured as one piece to form the damping structure  28 . The damping structure  28  may be manufactured from any material that has resilient properties for dampening chatter and wear properties for withstanding prolonged contact with the inside surface of the bearing bore  12 , including but not limited to Teflon®, Delron®, and Peek®. The damping structure shown in FIG. 4 may also be designed to accommodate the retainer  20  shown in FIG. 3.  
         [0018]    As a result, the invention incorporates a damping structure into the shaft rather than into the manifold body, making it easier to manufacture a manifold with minimal chatter. The outside surface of the shaft is more easily accessible than the inside surface of the bearing bore, making the inventive structure amenable to variations in the damping structure.  
         [0019]    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.