Abstract:
An air filter for a combustion engine for off-load motorcycles is made from a porous foam material. The air filter has contiguous side surface forming a cavity with at least two openings where the side surface contains at least one filter layer, a bottom surface closing at least one of the two openings where the bottom surface contains at least one filter layer, where the side surface has more air resistant than the bottom surface. The side surface has more air resistant than said bottom surface by arranging any combination of thickness of the surfaces, number of layers, and porosity ratio of the layers.

Description:
CROSS-REFERENCE TO APPLICATION AND CLAIM OF PRIORITY 
       [0001]    This is a continuation in part application of U.S. patent application Ser. No. 11/096,815 filed on Mar. 31, 2005, the disclosures of which are incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention provides an improved air filter, or filter, for internal combustion engines and particularly adapted for use with motorcycles, the filter having different airflow resistance at different portions thereof. 
         [0004]    2. Description of the Prior Art 
         [0005]    Air filters designed for use with internal combustion engines have been available for many years. The air filter is typically installed in an air-filter case mounted beneath the seat and is connected to carburetor through the intake pipe. 
         [0006]    Conventional air filters for off-road motorcycles are typically shaped as a conical frustum having a cavity opening at its inner section. The conventional air filter is typically made in a wet sponge format, i.e. foam sponge is immersed in viscous oil and then used with the air filter. In order to prevent reduced airflow due to dust deposits, the wet sponge filters utilize a double-layered structure wherein a coarse sponge is placed on the air filter outer layer and a covering a fine sponge placed as the inner layer. The sponges typically are the same thickness. 
         [0007]    It is known that air filters are essential to protect the engine from dirt and sand in order to ensure its durability; engines having low ventilation resistance are considered desirable because airflow injected into the engine creates resistance. Current air filters seek the ability to block dirt and sand and injected air resistance, airflowing evenly from many directions at the same time. In this regard, and referring to  FIGS. 7-9 , conventional air filter  50  utilizes different sponges  51  and  52  for its outer and inner layers, each sponge being made of the same material and of the same thickness for the entire surface area. This allows the same amount of air to flow into the air filter  50  from all surface areas. That in turn causes the air  51  flowing from the side-surface section to collide with the air  52  flowing from the bottom surface section on the inside of the air filter  50  causing air turbulence. As a result the air intake to the engine decreases, decreasing engine efficiency. 
         [0008]    U.S. Pat. No. 4,039,308 to Schiff (Schiff) discloses a device formed of rigid foam material which functions both to filter and straighten air introduced thereto prior to being directed to the vehicle air intake. Specifically, the device comprises an integral air filter and air straightening means made of the same porous material. The air straightening means performs two functions, i.e. that of cleaning air introduced thereto in a manner similar to that accomplished by an air filter while also reducing the turbulence of the cleaned air before being introduced to an air intake device, such as a carburetor. 
         [0009]    Although the air fitters disclosed in the conventional arts, such as illustrated in Schiff, provide an increased flow of cleaned air at the air intake of the internal combustion engine, the airflow comprises two components having two different velocity vectors; the resultant mixed airflow reducing the total amount of useful airflow to the air intake, thus reducing engine efficiency. What is desired is to provide a simple, yet cost efficient, light weight air filter that creates increased airflow into the engine, thus increasing engine efficiency. 
       SUMMARY OF THE INVENTION 
       [0010]    The present invention provides an air filter having different airflow resistance at different portions thereof. The airflow resistance through the side section of the filter is different from the airflow resistance through the bottom-surface section of the air filter. 
         [0011]    The present invention controls the desired airflow resistance by selecting the appropriate number of layers, the appropriate thickness, and the appropriate porous ratio of the filter materials that comprise the side-surface section and bottom surface section of the air filter. 
         [0012]    The air filter of the present invention protects the engine from dirt and sand so as to ensure its durability and, at the same time, offers a measure of resistance to the flow of intake air to the engine. Traditionally, it has been regarded that an air filter with less resistance is preferable, so that the air filter has been the product of a compromise between the ability to prevent dirt and sand from entering the engine and the resistance to the intake airflow. 
         [0013]    The present invention increases the amount of intake airflow volume and increases the engine&#39;s output power by controlling the smoothing airflow within the air filter as the result of a relative difference in the airflow resistances provided through the side-surface section and the bottom surface section of the air filter and maximizing engine output power. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0014]    For a better understanding of the present invention as well as other objects and further features thereof reference is made to the following description which is to be read in conjunction with the accompanying drawing therein: 
           [0015]      FIG. 1  is a perspective view of a motorcycle incorporating the teachings of the present invention; 
           [0016]      FIG. 2  is a view showing the motorcycle seat section and the location of the air filter of the present invention; 
           [0017]      FIG. 3  is a cross-sectional view of a first embodiment of the air filter of the present invention; 
           [0018]      FIG. 4  illustrates airflow through the air filter of the present invention; 
           [0019]      FIG. 5  is a cross-sectional view of a second embodiment of the air filter of the present invention; 
           [0020]      FIG. 6  is a cross-sectional view of a third embodiment of the air filter of the present invention; 
           [0021]      FIG. 7  is a perspective view of a prior art; 
           [0022]      FIG. 8  is a cross-sectional view of  FIG. 7 ; 
           [0023]      FIG. 9  is a cross-sectional view of  FIG. 7  showing the airflow and collision of the airflow; 
           [0024]      FIG. 10  is a fourth embodiment of the air filter of the present invention. 
           [0025]      FIG. 11  is a cross-sectional view of fifth embodiment of the present invention; and 
           [0026]      FIG. 12  is a cross-sectional view of sixth embodiment of the present invention. 
       
    
    
     DESCRIPTION OF THE INVENTION 
       [0027]      FIG. 1  is a left-side view of a motorcycle  1  illustrating a seat section  2  and an intake pipe  4 , and  FIG. 2  is a perspective view of the seat section  2  removed from the motorcycle  1  showing an air filter case  3  mounted underneath the seat section  2  of the motorcycle  1 . In the front section of the air filter case  3 , a conical frustum shaped air filter  10 , which is described hereinafter, is installed with its upper flat surface facing frontward. It should be noted that other shapes for the air filter can be used. In addition, the air filter may be located in positions other than below the seat. The intake pipe  4  is connected to the flat surface section. The rear-end section of the air filter case  3  has an opening (not shown). The airflows through this opening, and the air filter  10  removes dirt and sand from the air. The air is then sent to the carburetor (not shown) via the intake pipe  4 . 
         [0028]      FIG. 3  is a cross-sectional view of the first embodiment of this invention pertaining to the air filter of the present invention. The air filter  10  is illustrated as shaped as a conical frustum. The interior section has a cavity opening  14 , which faces an upper flat surface  11 . The air filter  10  is made of a foam material such as foam urethane. In this embodiment, the air filter  10  is structured as two layers such that a foam material layer  16  covers a side surface section  13  and a bottom surface section  12  of a foam material  15  that has the center cavity section  14 . Additionally, the side surface section  13  is structured as three layers, where a foam material layer  17  covers the outer surface of the foam material layer  16 . Additionally, the foam material layer  15 , the foam material  16  and the foam material layer  17  are made of the same basic material and of the same thickness. However, as compared to the foam material layer  15 , the foam material  16  and the foam material  17  have a coarse foaming ratio. Foaming ratio as herein defined relates to the size, or diameter, of the openings in each foam layer. 
         [0029]      FIG. 4  shows the airflow within the air filter  10 . In this embodiment of the invention, the air filter  10  is structured in three layers at the side surface  13  and has a larger airflow resistance as compared to the bottom surface  12  section, where it is structured as two layers. As a result, the airflow “S” into the air filter  10  is only from the bottom surface  12 , not from the side surface  13 , thereby resulting in smooth, straight airflow and an increased volume of intake airflow. When the volume of intake airflow increases, the volume of fuel injection is also increased at the same ratio in order to maintain combustion efficiency. This combined increase in air intake volume and fuel injection volume produces a relative increase in engine output power. 
         [0030]      FIG. 5  is a cross-sectional view of a second embodiment of the air filter of the present invention. In this embodiment, an air filter  20  has a side surface  23  in combination of a first layer  25  and a second layer  26  that covers the outer surface of the first side layer  25 , a bottom surface  22  in combination of the first layer  25  and the second layer  26 , and a center cavity opening  24 . The air filter  20  is illustrated as shaped as a conical frustum. The air filter  20 , in this embodiment, is shaped in conical frustum that is thicker at the side surface section  23  as compared to the thickness at the bottom surface  22  section. Therefore, the airflow resistance at the side surface  23  is greater than it is at the bottom surface  22 . The result is a smooth, straight flow of air and a relative increase in the volume of intake airflow. Additionally, the foam material layer  25  and the foam material layer  26  are made of the same basic material. However, as compared to the foam material  25 , the foam material layer  26  has a coarse foaming ratio. 
         [0031]      FIG. 6  is a cross-sectional view of a third embodiment of the air filter of the present invention. In this embodiment, an air filter  30  has a side surface  33  in combination of a first layer  35  and a second layer  36  that covers the outer surface of the first side layer  35 , a bottom surface  32  in combination of the first layer  35  and a bottom second layer  37 , and a center cavity opening  34 . The air filter  30  is illustrated as shaped as a conical frustum. The air filter  30  has the second layer  36 , which covers the first side layer  35 , which in turn shapes the center cavity opening  34  of the conical frustum, has a finer foaming ratio than the bottom second layer  37  that covers the bottom surface  32  section of the first side layer  35 . Therefore, the airflow resistance at the side surface  33  is greater than the airflow resistance at the bottom surface  32 . The result is a smooth, straight flow of air and a relative increase in the volume of intake airflow. Additionally, foam material layer  35 , foam material layer  36  and foam material  37  have the same thickness. 
         [0032]      FIG. 10  is a cross-sectional view of a fourth embodiment of the present invention. In particular, an air filter  70  has an outer layer  74  covering an inner layer  72  and a bottom flat surface  76 . The air filter  70  is illustrated as shaped as a conical frustum. A circumferential plate  78 , preferably made of a plastic material, is positioned at the outer perimeter external wall of outer layer  74  and functions to minimize the airflow entering into the air filter through outer layer  74  while maximizing the airflow through the bottom surface section  80 . 
         [0033]      FIG. 11  is a cross-sectional view of a fifth embodiment of the present invention. In this embodiment, an air filter  40  has a side surface  41 , a bottom surface  42  including a first bottom layer  43  and a second bottom layer  44 , and a center cavity opening  45 . The air filter  40  is illustrated as shaped as a conical frustum. The side surface  41  and the bottom layer  42  are made of porous material, where the side surface  41  has a finer porous ratio than the bottom surface  42 . The second bottom layer  44  has a finer porous ratio than the first bottom layer  43 . Therefore, the airflow resistance at the side surface  41  is greater than the airflow resistance at the bottom surface  42 . The result is a smooth, straight flow of air and a relative increase in the volume of intake airflow. Thickness of the side surface  41  and the bottom surface  42  may be modified as necessary as long as the airflow resistance at the side surface  41  is greater than the airflow resistance at the bottom surface  42 . 
         [0034]      FIG. 12  is a cross-sectional view of a sixth embodiment of the present invention. An air filter  60  has a side surface  61  including a first side layer  62  and a second side layer  63 , an bottom surface  64  including a first bottom layer  65  and a second bottom layer  66 , and a center cavity opening  67 . In this embodiment, the shape of the air filter  60  is reverse-conical frustum relative to the previous embodiments. The side surface  61  and the bottom layer  64  are made of porous material, where the first side layer  62  and the first bottom layer  65  have a finer porous ratio than the second side layer  63  and the second bottom layer  66 . The side surface  61  is thicker than the bottom surface  64 , and each layer can be designed so that the airflow resistance at the side surface  61  is greater than the airflow resistance at the bottom surface  64 . The result is a smooth, straight flow of air and a relative increase in the volume of intake airflow. Thickness of the side surface  61  and the bottom surface  64  may be modified as necessary as long as the airflow resistance at the side surface  61  is greater than the airflow resistance at the bottom surface  64 . 
         [0035]    Even though the number of layers, the thickness and the foaming ratio of the foam materials are varied independently in order to modify the airflow resistance in the embodiments noted hereinabove, in actual implementation any combination of these factors can be utilized. In the embodiments described above, the airflow resistance through the side surface is increased relative to the bottom surface. However, it is also acceptable to increase the airflow resistance through the bottom surface as compared to the side surface. The point to note is that to create a smooth, straight flow of air within the air filter, different thicknesses at the bottom and side surfaces are provided. 
         [0036]    While the invention has been described with reference to its preferred embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the true spirit and scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from its essential teachings.