Patent Publication Number: US-2007101955-A1

Title: Air intake lengthening structure for model engines

Description:
FIELD OF THE INVENTION  
      The present invention relates to the structure of model engines and particularly to an air intake structure to increase air intake time to thoroughly mix fuel gas and enhance engine performance.  
     BACKGROUND OF THE INVENTION  
      Referring to  FIGS. 1A and 1B , a conventional two-stroke model engine  1  has four processes during operation that include air intake, compression, combustion and gas exhaustion. Fuel and air are mixed in a carburetor  2  to become fuel gas. The fuel gas passes through an inclined air inlet  4  of the engine  1  and a passage  5  in the middle of a crankshaft  3  to enter a crankshaft chamber  6 . A piston  7  driven by the crankshaft  3  through a linkage bar  8  is moved upwards (as shown in  FIG. 1A ). Then the mixed fuel gas in a combustion chamber of a cylinder  9  is ignited by a spark plug (a) to burn and generate a combustion stroke. A pressure is generated to push the piston  7  downwards as shown in  FIG. 1B . When the piston  7  is moved downwards at a selected distance, a gas outlet b on one side of the cylinder  9  is opened, and the mixed fuel gas trapped in the crankshaft chamber  6  is sucked by the piston  7  through the gas outlet (b) into the combustion chamber of the cylinder  9 ; the exhaust gas generated by the previous combustion is discharged through an exhaust vent (c) on another side of the cylinder  9 . One operation cycle of the model engine is therefore completed.  
      Referring to  FIGS. 1A and 2  again, when the crankshaft  3  rotates and an opening of the passage  5  in the middle portion is aligned with a fuel gas injection port d on a lower side of the carburetor  2 , a great amount of fuel gas rapidly enters the crankshaft chamber  6  through the passage  5  of the crankshaft  3 . The time for mixing the fuel and air is not adequate. And the fuel and air cannot be mixed thoroughly. This results in waste of fuel and not smooth operation of the engine. The torque of the engine at low speed also is lower. The engine rotation speed cannot be increased as desired. Hence engine performance is not desirable.  
      There is an improvement being developed in the industry that has ditches (not shown in the drawings) formed on the periphery of the crankshaft  3  and extended to the opening of the passage  5  so that the fuel gas ejected from the carburetor flows through a gradually larger channel into the passage  5  of the crankshaft  3  with the rotation angle of the crankshaft  3 . The intake time of the fuel gas is lengthened. But such a structure results in a decreasing strength of the crankshaft  3  due to formation of the ditches on the periphery thereof. As a result, the crankshaft fractures easily.  
     SUMMARY OF THE INVENTION  
      In view of the aforesaid disadvantages, the primary object of the invention is to provide an air intake lengthening structure for model engines that mainly has at least one channel on the bottom wall of an air inlet of a model engine. The channel is formed in an inclined manner and directs inwards from an outer side of the air inlet to mate an opening of an air intake passage in the middle portion of a crankshaft so that the amount of fuel gas gradually increases to enter the passage of the crankshaft. As a result, the time of fuel gas intake is lengthened to allow the air and fuel to mix up thoroughly. This can save fuel consumption and make rotation speed more stable. Engine performance improves, and the strength of the crankshaft may be maintained intact.  
      The foregoing, as well as additional objects, features and advantages of the invention will be more readily apparent from the following detailed description, which proceeds with reference to the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1A  is a schematic view of a conventional model engine showing air intake and ignition operations.  
       FIG. 1B  is a schematic view of a conventional model engine showing compression and gas exhausting operations.  
       FIG. 2  is a perspective view of a crankshaft of a conventional model engine.  
       FIG. 3  is an exploded view of an embodiment of the invention.  
       FIG. 4  is a sectional view of an engine block of an embodiment of the invention.  
       FIG. 5  is a sectional view of an embodiment of the invention.  
       FIG. 6A  is a schematic view of an embodiment of the present invention in an operating condition.  
       FIG. 6B  is a schematic view of an embodiment of the present invention in another operating condition.  
       FIG. 6C  is a schematic view of an embodiment of the present invention in yet another operating condition. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
      Please referring to  FIGS. 3, 4  and  5 , the air intake lengthening structure for model engines according to the invention includes a model engine  1  which mainly has a rotary crankshaft  10  and an air inlet  11  leading to an opening of a passage  110  formed in a middle portion of the crankshaft  10  to allow fuel gas ejected from a carburetor  20  to enter a crankshaft chamber  17  formed in the model engine  1 . The crankshaft  10  has an axle  12  extended from one end of an inner side thereof. The axle  12  is coupled with a first end  131  of a linkage bar  13 . The linkage bar  13  has a second end  132  coupling with a piston  14 . The piston  14  has a gas outlet  141  on a side wall and an exhaust vent  142  on another side wall. The piston  14  is located in a cylinder  15  of the model engine  1 . The cylinder  15  is coupled with a spark plug  16  on a upper side, and has a combustion chamber  151  on the top portion.  
      The carburetor  20  is coupled on the air inlet  11  which has a fuel gas injection port  111  on the bottom. The improvement of the invention includes two channels  112   a  and  112   b  formed on two opposite inner walls of the fuel gas injection port  111 . The channels  112   a  and  112   b  are inclined and directed inwards from an outer side of the air inlet  11  so that the bottom has a greater diameter. The fuel gas injection port  111  corresponds to the opening of the passage  110  of the crankshaft  10 . The two channels  112   a  and  112   b  are parallel with the axis of the air inlet  11 .  
      By means of the structure set forth above, referring to  FIG. 6A , when the crankshaft  10  rotates counterclockwise, a first edge  113  of the opening of the passage  110  faces the channel  112   a , and the bottom of the channel  112   a  forms a gap with the first edge  113 , hence the fuel gas ejected from the carburetor  20  can enter the passage  110  in a small amount, then enters the crankshaft chamber  17 . As the crankshaft  10  rotates continuously, the gap between the first edge  113  and the fuel gas injection port  111  becomes bigger until the opening of the passage  110  fully faces the fuel gas injection port  111  to allow maximum amount of fuel gas to enter the passage  110  (referring to  FIG. 6B ). Then a second edge  114  of the passage  110  is moved close to the other channel  112   b  so that the amount of the fuel gas entering the passage  110  gradually reduces until another peripheral side of the crankshaft  10  fully covers the fuel gas injection port  111  to form a closed condition as shown in  FIG. 6C . Thus the fuel gas ejected from the carburetor  20  has sufficient time to mix up. With the rotation of the crankshaft  10 , and through the gradually increasing of the gap between the channel  112   a  and the opening of the passage  110 , and until fully alignment of the passage  110  and the fuel gas injection port  111 , injection of the fuel gas into the passage  110  alters gradually from a smaller amount to a greater amount. It is equivalent of lengthening fuel gas intake time into the crankshaft chamber  17 . Moreover, as the fuel gas enters the crankshaft chamber  17  gradually from the smaller amount to the greater amount, the fuel ejected from the carburetor  20  can be mixed up with the air thoroughly. This can facilitate complete combustion. As a result, sufficient torque can be generated during low rotation speed of the model engine, and a higher rotation speed also can be achieved. Fuel consumption also can be reduced. And engine performance can be improved.  
      Prototypes of the invention have been made and tested successfully. The test results have met the expected objects and functions. It provides a significant improvement over the conventional techniques.  
      While the preferred embodiment of the invention has been set forth for the purpose of disclosure, modifications of the disclosed embodiment of the invention as well as other embodiments thereof may occur to those skilled in the art. Accordingly, the appended claims are intended to cover all embodiments which do not depart from the spirit and scope of the invention.