Abstract:
A throttle body is provided with an internal fuel reservoir for relieving pressure waves and for assisting hot start conditions of an associated small internal combustion engine employing a low pressure fuel injection system.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This Non-Provisional application claims priority to U.S. Provisional Application Ser. No. 61/554,262 filed Nov. 1, 2011, and which is incorporated herein by reference. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH 
       [0002]    Not Applicable. 
       BACKGROUND 
       [0003]    This invention relates generally to a fuel regulation system, and more particularly, to an electronic fuel injection system for small internal combustion engines, and to improvements in a throttle body construction for improved performance of the system. 
         [0004]    A number of problems are encountered when adopting a low pressure electronic fuel injection system to small internal combustion engines. For instance, when attempting to restart an engine that was recently in use, sometimes referred to as a hot start, a condition known as vapor lock can stall, or prevent starting of the engine. Vapor lock occurs when the liquid fuel changes state from liquid to gas while still in the fuel delivery system. This disrupts the operation of the fuel pump, causing loss of feed pressure to the carburetor or fuel injection system, resulting in transient loss of power or complete stalling. When restarting an engine in this state, the fuel can vaporize due to being heated by the engine, by the local climate or due to a lower boiling point at high altitude. In regions where higher volatility fuels are used during the winter to improve the starting of the engine, the use of “winter” fuels during the summer can also cause vapor lock. 
         [0005]    Another typical problem with fuel injection systems is the occurrence of pressure waves, fluctuations, or hammer effect through the system during operation. This can be caused by opening and closing of the fuel injection valve. Any of these occurrences can impair the operation of the system, cause emissions instability, and place undesirable stresses on the mechanical components of the system. 
         [0006]    Therefore, a fuel regulation system capable of performing a hot start and avoids pressure waves, pressure fluctuations, and hammer effects during operation is needed. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0007]    In the accompanying drawings which form part of the specification: 
           [0008]      FIG. 1  is a perspective view of a throttle assembly for an internal combustion engine; 
           [0009]      FIG. 2  is a second perspective view of the throttle assembly for an internal combustion engine; and 
           [0010]      FIG. 3  is an exploded perspective view of the throttle assembly for an internal combustion engine; 
           [0011]      FIG. 4  is a perspective view of a throttle body; 
           [0012]      FIG. 5  is a second perspective view of the throttle body; 
           [0013]      FIG. 6  is a side view of the throttle body; and 
           [0014]      FIG. 7  is a block diagram of a fuel regulation system. 
       
    
    
       [0015]    Corresponding reference numerals indicate corresponding parts throughout the several figures of the drawings. 
       DETAILED DESCRIPTION 
       [0016]    The following detailed description illustrates the claimed invention by way of example and not by way of limitation. The description clearly enables one skilled in the art to make and use the claimed invention, describes several embodiments, adaptations, variations, alternatives, and uses of the claimed invention, including what is presently believed to be the best mode of carrying out the claimed invention. Additionally, it is to be understood that the claimed invention is not limited in its application to the details of construction and the arrangements of components set forth in the following description or illustrated in the drawings. The claimed invention is capable of other embodiments and of being practiced or being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. 
         [0017]    As shown in  FIGS. 1-7 , a, fuel regulation system  10  includes a throttle body injection assembly  12  operatively attached between a fuel supply  14  and an intake of an engine  16  for metering air and fuel to the engine  16  in a predetermined ratio controlled by an electronic control unit (ECU)  18 . The throttle body injection assembly  12  includes a throttle body  15  that defines a fuel reservoir  20  configured for dampening or relief of pressure fluctuations in the system  10  and removal of vapor entrained in the fuel. 
         [0018]    The engine  16  is preferably a four-stroke internal combustion engine, such as those used in residential and commercial power equipment, including but not limited to mowers, snow blowers, pressure washers, tractors, and generators. However, any suitable type of engine can be used. 
         [0019]    The ECU  18  controls the operation of the system  10  using a circuit board with a microprocessor. The ECU  18  communicates with one or more sensors (not shown) positioned throughout the system  10  to receive data for determination of various elements, such as, the position of a throttle valve, the pump speed, pulse width of a fuel injector, spark ignition timing, and engine speed. 
         [0020]    The throttle body  15  is generally rectangular prism shaped and defines a throttle bore  22  that extends from an air inlet  24  generally straight through the throttle body  15  to an outlet  26  coupled with the engine  16 . Airflow through the throttle bore  22  is controlled or metered by a throttle valve  28  which is moveably attached within the throttle bore  22  and operatively connected to the ECU  18 . The throttle valve  28 , is preferably a butterfly valve that is pivotally attached within the throttle bore  22 , however, any suitable type of valve can be used. The ECU  18  can move the throttle valve  28  variably between an open position, a closed position, and anywhere in between, to respectively increase or decrease the flow of air through the throttle bore  22  for mixing with the fuel, and flowing into the engine  16  for combustion. The throttle body  15  of  FIGS. 1-7  has a lower number passages of less complexity than previously known configurations. 
         [0021]    A fuel pump  30  mounts to a bottom surface of the throttle body  15  and operatively connects to the fuel reservoir through an opening  32  for communication of the fuel supply  14  to the fuel reservoir  20 . The fuel pump  30  communicates fuel to the fuel reservoir  20  in sufficient volume to meet the engine&#39;s fuel requirement through all load conditions. The fuel pump  30  is preferably a vacuum type pump, however, any type of pump can be used. The throttle body  15  defines a relief orifice  34  configured for communicating vapor from the fuel reservoir  20  back to fuel supply  14 , where the vapor can condense back into fuel. 
         [0022]    A pressure regulator  36  mounts to the throttle body  15  and is in communication with the fuel reservoir  20  through a regulator feed channel  38  to maintain a predetermined pressure within the fuel reservoir  20  and maintain a fuel supply to a fuel injector  40  at a generally constant pressure, such as about 5-6 psi. The pressure regulator  36  is preferably a vacuum-operated diaphragm, but other types of regulators can also be used. 
         [0023]    The fuel injector  40  mounts to an injector inlet  42  of the throttle body  15  for single point injection of the fuel into the throttle bore  22 . The injector inlet  42  is positioned for injection of the fuel into the throttle bore  22  after the throttle valve  28 . A fuel line  44  communicates fuel from an injector feed outlet  46  to the fuel injector  40 . 
         [0024]    When assembled, the throttle body injection assembly  12  should be positioned with the throttle bore  22  being generally vertical with the inlet  24  generally upward. The pressure regulator  36  and fuel injector  40  are positioned on a side surface of the throttle body  15 , and the fuel pump  30  is positioned on an opposite side surface of the throttle body  15 . In this position, the fuel reservoir  20  is positioned generally vertically so that the injector feed outlet  46  is in communication with a lower portion  50  of the fuel reservoir  20 , which is generally filled with fuel, and the regulator feed channel  36  is in communication with an upper portion  52  of the fuel reservoir  20 , which is generally filled with gas or vapor. 
         [0025]    The position of the injector feed outlet  46  should be positioned at an elevation above the bottom surface of the throttle body  15  sufficient to reduce, if not eliminate, the entry of debris, water, and other undesirable materials into the injector feed outlet  46 . 
         [0026]    In operation, the fuel pump  30  communicates fuel from the fuel supply  14  to the fuel reservoir  20  of the throttle body  15  through the opening  32 . A volume of fuel collects within the lower portion  50  of the fuel reservoir  20 . The volume of fuel should have sufficient resident time within the fuel reservoir  20  to allow the vapors to separate from the liquid fuel and collect within the upper portion  52  of the fuel reservoir  20 . The vapors are bled from the fuel reservoir  20  through the relief orifice  34  to the fuel supply  14 . This reduces the amount of vapors within the fuel before the fuel enters the fuel injector  40 . Thus, a generally vapor free fuel can be fed to the fuel injector  40  and allow the system to operate during a hot start. The fuel reservoir  20  also relieves pressure waves that cause water hammer type pressure spikes and contribute to engine emissions and instability. 
         [0027]    The pressure regulator  36  exerts positive pressure on the volume of fuel to communicate fuel through the fuel line  44  and to the fuel injector  40  for injection into the throttle bore  22  for mixing with air into a predetermined ratio. The ECU  18  pivots the throttle valve  28  to allow a predetermined flow of air into the inlet  24  of the throttle bore  22  for mixing with the fuel into the predetermined ratio. The resulting air-fuel mixture flows into the engine  16  for combustion. 
         [0028]    Changes can be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense. For example, an alternate embodiment can include a plurality of return lines installed on left, right or both sides of the throttle body depending on fuel tank location in the particular small internal combustion engine application.