Abstract:
The present invention relates to a component for an internal combustion engine of an automobile having reduced NVH properties. The component has a shell formed with a plastic composite material. The shell defines an inlet port, an outlet port, an outer surface and an inner surface. The inner surface defines an inner cavity to allow air passage to the internal combustion engine. A damping layer is disposed on the outer surface such that damping layer substantially dampens the noise emitted from the component.

Description:
TECHNICAL FIELD OF THE INVENTION  
         [0001]    This invention generally relates to an intake manifold of an internal combustion engine of a motor vehicle. More specifically, this invention relates to reducing noise in an intake manifold of an internal combustion engine.  
         BACKGROUND OF THE INVENTION  
         [0002]    Noise is generated by the internal combustion engines due to engine vibration, internal pressure pulsations, and combustion. Intake manifolds have a distinct and profound affect on the Noise Vibration and Harshness (NVH) quality of the vehicle. This is because the intake manifolds are excited not only by the vibrational input of the structure of the engine but they are also excited by internal pressure pulsations due to intake events. Therefore, there is a need to design a manifold that is structurally sound to resist an extremely wide frequency range of forcing inputs.  
           [0003]    In order to suppress undesirable noise from the intake manifold, prior art techniques have taught the use of an intake manifold cover. The cover is mechanically attached, sometimes with isolating features, to the intake manifold or engine. However, it has been found that the use of the NVH cover does not always result in effective reduction of noise from the manifold. Also, it has been found that due to packaging requirements the cover may not completely cover the intake manifold thereby allowing noise to escape.  
           [0004]    Additionally, it has been found that aluminum intake manifolds have superior NVH qualities to that of plastic intake manifolds. This is due to their greater mass, which increases transmission loss through the part, and due to the increased stiffness of the part, which allows the manifold to resist deflection. Therefore, it is found that composite intake manifolds do not prevent noise transmission from their surfaces to maintain levels of radiated noise as low as possible.  
           [0005]    Therefore, there is a need in the industry to manufacture intake manifolds that maintain low levels of NVH, are lightweight, easy to manufacture and cost effective.  
         SUMMARY OF THE INVENTION  
         [0006]    The present invention generally relates to a component for an internal combustion engine of an automobile having reduced NVH properties. The component has a shell formed of a plastic composite material. The shell defines an inlet port, an outlet port, an outer surface and an inner surface. The inner surface defines an inner cavity to allow air passage to the internal combustion engine. In addition the component includes a damping layer disposed on the outer surface, where the damping layer substantially dampens the noise emitted from the component. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]    Further features and advantages of the invention will become apparent from the following discussion and the accompanying drawings in which:  
         [0008]    [0008]FIG. 1 is a perspective view of an internal combustion engine;  
         [0009]    [0009]FIG. 2 is a perspective view of the throttle adapter of an intake manifold for an internal combustion engine;  
         [0010]    [0010]FIG. 3 is a perspective view of the throttle adapter with the damping layer of a metallic matrix for an internal combustion engine;  
         [0011]    [0011]FIG. 4 is a cross sectional view of the component;  
         [0012]    [0012]FIG. 5 is a graphical representation of the transmission loss through the exterior surface of the component;  
         [0013]    [0013]FIG. 6 is a graphical representation of frequency versus sound pressure level for a aluminum component and a composite component; and  
         [0014]    [0014]FIG. 7 is a graphical representation of frequency versus sound pressure level for a composite component and the composite component with a damping layer. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0015]    The following description of the preferred embodiment is merely exemplary in nature and is in no way intended to limit the invention or its application or uses.  
         [0016]    Referring in particular to FIG. 1, an internal combustion engine installed in a motor vehicle is generally shown and illustrated by reference numeral  10 . As shown in FIG. 1, the engine  10  comprises a cylinder head  12 , a combustion chamber  14  for burning the fuel, a piston  16  moving up and down inside the cylinder, a crankshaft  17  for moving the piston  16  in a circular motion, a connecting rod  19  connecting the piston  16  to the crankshaft  17 , an intake port  18  for conduct air-fuel mixture to the crankshaft  17  and an valve  15  for selectively allowing air-fuel mixture to enter the combustion chamber  14 . The engine  10  may have additional components such as oil pan, bearings, sparkplug, exhaust port, exhaust valve etc. The working of the engine  10  is well known and is not explained in details.  
         [0017]    The intake port  18  is connected to a conduit (not shown) that transports the air to the combustion chamber  14 . The conduit at the other end is connected to an intake manifold (not shown). As shown in FIG. 2, a component of the intake manifold is shown and represented by reference numeral  20 . The component  20  may be referred to as a throttle body adapter. The component  20  as shown is juxtaposed between the intake manifold and the throttle chamber (not shown). The component  20  includes an input port  21  connected to the throttle chamber and an output port  22  connected to the intake manifold. The component  20  has an inner surface (not shown) defining an interior cavity to allow air to pass to the combustion chamber  14  of the engine  10 . The component  20  also defines an exterior surface  24 . The component  20  further includes a flange  26  about the perimeter of the component  20 . The flange  26  includes apertures  28  for receiving fasteners that secure the component  20  to the intake manifold or alternatively to the cylinder head  12 .  
         [0018]    Although in the drawings a component  20  of an intake manifold is generally shown and described, it must be understood that this invention is not limited to this component. The present invention may alternatively be used on other engine components such as an exhaust manifold or to non-engine mounted components.  
         [0019]    The component  20  is formed of two separate sections, a first section or an upper part  30  and a second section or a lower part  32  (shown in FIG. 4). Preferably, the first section  30  and the second section  32  are injection molded plastic shells. The first section  30  and the second section  32  are preferably welded together using vibration welding technique. Other joining techniques may also be used to join the first section  30  and the second section  32 . Alternatively, the component  20  may be formed as a single integral piece. Preferably, the component  20  is formed of a plastic composite material. Preferably, the plastic composite material is selected from Nylon 6, 30% glass filled, Nylon 6, 33% glass filled, Nylon 6,6, 30% glass filled, Nylon 6,6, 33% glass filled or Nylon 6, 6, 35% glass filled. Alternatively, other composite material may be used.  
         [0020]    As shown in FIG. 3, in order to damp the noise emitted from the component  20 , the exterior surface  24  is coated with a damping layer  34 . The damping layer  34  is applied uniformly on to the exterior surface  24  of the component. Preferably, the both the exterior surface  24  of the first section  30  and the second section  32  is coated with the damping layer  34 . As the name suggests the damping layer  34  will substantially dampen noise emitted from the component  20 .  
         [0021]    Referring to FIG. 4, the damping layer  34  is selectively applied to the exterior surface  24  such that certain surfaces of the exterior surface  24  are free of the damping layer  34 . In order to selectively apply the damping layer  34  to the exterior surface  24 , portions of the exterior surface  24  are covered with a mask  27 . The mask  27  is a reusable shielding material that prevents the damping layer  34  from being applied in the desired area. It is preferred that the flange  26  and the apertures  28  are covered by the mask  27  before the damping layer  34  is applied on the exterior surface  24  of the component  20 .  
         [0022]    The damping layer  34  is preferably applied using the thermal spray casting process. Briefly described, this process, is simply a manufacturing process of applying a coat or coatings of material to a substrate to impart properties unobtainable by base material selections alone. The process includes heating the desired coating material used to form the damping layer  34  until it becomes molten. The atomized molten metal particles, preferably having a diameter of 0.1 mm to 0.4 mm are then carried through the air by air pressure or other means. The airborne particles hit the exterior surface  24  of the component  20  and rigorously bond the material to the exterior surface  24 . Bonding of the thermally sprayed coatings is principally through mechanical interlocking between the atomized particles and the exterior surface  24 . Generally, when applying metals to engineering thermoplastics, the plastic, in this case the exterior surface  24  is melted and re-crystallizes with an aggressive mechanical bond.  
         [0023]    The damping layer  34  is preferably a metallic coating where the metal is selected from a group consisting of zinc or aluminum. Preferably, the exterior surface  24  of the first section  30  and the second section  32  is covered with the damping layer  34  formed of the same metal. Alternatively, damping layer formed of different metal may be applied to the exterior surface  24  of the first section  30  and the second section  32 . Preferably, the metal used does not have a high molten temperature such that excessive deformation occurs to the exterior surface  24  of the component  20 . For example, if the component is made of Nylon 6, 33% glass filled, the component  20  typically has a melt temperature of 215° C. In such cases the damping layer  34  is formed of zinc as opposed to aluminum since zinc has a melting temperature of 420° C. Alternatively, other type of metals that can be thermally sprayed to form the damping layer  34 . Further, more than one metal can be simultaneously sprayed to form the damping layer  34 . Preferably, the thickness of the damping layer  34  is in the range of about 0.5 mm to 4.0 mm.  
         [0024]    As shown in FIG. 5, the transmission loss of the component  20  was measured using the basic rule of acoustics, called the mass law. This law states that most panels, when properly designed, will transmit noise nearly equivalent to the inverse of their material thickness. The rule essentially states, the thicker the part, the less noise transmission. As shown in the graph, a component  20  with a 1 mm coating of damping layer  34  made of zinc (represented by reference numeral  40 ) had greater transmission loss than the component  20  with a 4 mm damping layer  34  made of aluminum (represented by reference numeral  42 ).  
         [0025]    In order to test the NVH properties of the component  20 , the testing was conducted to measure the noise emitted from the component  20 . Testing was conducted in a hemi-anechoic chamber to eliminate background noise. Flow noise was ducted through each set of components  20  to set up high frequency oscillations within the interior of each part. A microphone was placed at a distance of 100 mm from the surface of the part and recordings were taken for the following components: Aluminum component, Nylon 6, 33% glass filled component with no coating, Nylon 6, 33% glass filled component with a 4 mm coating of aluminum damping layer  34 .  
         [0026]    The test results are indicated in FIGS. 6 and 7. As shown in FIG. 6, the Nylon 6, 33% glass filled component has a higher level of radiated noise (represented by reference numeral  44 ) than the aluminum component (represented by reference numeral  46 ) across the frequency spectrum. However, in FIG. 5 the radiated noise is substantially reduced when the Nylon 6, 33% glass filled component is compared with the Nylon 6, 33% glass filled component with a damping layer  34  (represented by reference numeral  48 ). As seen above, the present invention provides for selectively applying the damping layer  34  to an exterior surface of a component  20  such that the component has improved NVH properties.  
         [0027]    As any person skilled in the art will recognize from the previous description and from the figures and claims, modifications and changes can be made to the preferred embodiment of the invention without departing from the scope of the invention as defined in the following claims.