Abstract:
A micro-pulsation fuel injection system with underpressure stabilizer, comprising a fuel supply system, a fuel tank, a micropump, and a compression pump. The micropump ejects fuel into an intake pipe. The compression pump is connected with a fuel supply pipe of the micropump, for keeping underpressure of the inlet of the micropump against the intake pipe stable. Incoming fuel passes through a fuel chamber, separated by a membrane from a pressure chamber, which in turn is connected to the intake pipe. The membrane deforms according to pressure in the intake pipe, changing volume of the fuel chamber and generating underpressure of fuel therein. Additionally, a regulating valve is installable between the compression pump and the micropump for stabilizing the difference of pressures at the inlet of the micropump and in the intake pipe. Thus the quantity of fuel ejected by the micropump is precisely controlled.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a micro-pulsation fuel injection system with underpressure stabilizer, particularly to a micro-pulsation fuel injection system with underpressure stabilizer to be used in an internal combustion engine.  
           [0003]    2. Description of Related Art  
           [0004]    Conventional fuel supply systems of internal combustion engines include carburetors and fuel injection systems. A mechanical carburetor, using underpressure generated by flow in a tube, sucks in and vaporizes fuel. Vaporized fuel, having mixed with air, enters a cylinder of the internal combustion engine. However, being regulated by an inclination of an adjustment needle and flow control by the throttle valve, the quantity of fuel taken in is hard to control precisely. At full throttle, vaporization is imperfect, so that fuel wetting becomes worse.  
           [0005]    A fuel injection system, on the other hand, has an electric fuel pump which pressurizes and pushes out fuel through a nozzle into an inlet manifold, where fuel is sprayed apart into fuel droplets. The fuel droplets subsequently mix with inlet air and enter a cylinder of the internal combustion engine. However, since fuel is ejected at high speed without being uniformly distributed, no uniform mixture of fuel and air is attained, so that fuel is wetted at walls of the intake port. Imperfect combustion of fuel results then.  
           [0006]    Furthermore, with increasing demand for better characteristics, conventional carburetors developed to the present day have become complicated precision devices, which makes manufacturing thereof difficult and expensive. On the other hand, fuel injection systems, each requiring a fuel pump, a high-pressure pipe, a regulator, and a nozzle are complex and costly. Since operating pressure is high, sealing of pipes and of the pump requires special attention to prevent leakage. A collision or burst of the pipes will causes fuel spurt out, forming fuel vapor which is readily ignited by a spark or heat. This is a severe safety drawback.  
           [0007]    For the reasons just given, conventional fuel supply systems have considerable shortcomings. This has brought up micro-pulsation pumps as means for supplying fuel. Therein, micropumps are placed at the intake pipe of an internal combustion engine, vaporizing and ejecting fuel into the inlet. Thus fuel which is completely mixed with air enters the cylinder. Being products of mature technology, micropumps are inexpensive. Furthermore, micropumps operate at low pressure, thus there is no need to add a pressurizing system. This keeps down costs, and there is no risk of explosion due to broken pipes. Moreover, micropumps are capable precisely to dose fuel, ejecting fuel droplets ejected at medium speed, so completely mix with air. Therefore, no wetting of walls of intake pip will occur, and combustion in the engine will be more effective.  
           [0008]    However, since a micropump operates without valves, underpressure of incoming fuel needs to be maintained to prevent fuel from leaking from the micropump due to gravitation. Furthermore, being placed in the inlet of the engine, inlet pressure varies with operational states of the engine, with underpressure of incoming fuel varying along. This causes the quantity of fuel furthered by the micropump to vary, as well. It is therefore desirable for achieving well-defined operation of the micropump to keep the underpressure of incoming fuel stable against the pressure of air in the inlet.  
         SUMMARY OF THE INVENTION  
         [0009]    The main object of the present invention is to provide a micro-pulsation fuel injection system with underpressure stabilizer which maintains a stable underpressure of an inlet of the micropump against the exterior thereof in an intake pipe of an internal combustion engine, so that fuel is precisely delivered for effective combustion thereof.  
           [0010]    The present invention has a compression pump at a fuel supply pipe of the micropump, for keeping underpressure of the inlet of the micropump against the intake pipe stable. Incoming fuel passes through a fuel chamber, separated by a membrane from a pressure chamber, which in turn is connected to the intake pipe. The membrane deforms according to pressure in the intake pipe, changing volume of the fuel chamber and generating underpressure of fuel therein.  
           [0011]    The present invention can be more fully understood by reference to the following description and accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    [0012]FIG. 1 is a schematic illustration of the micro-pulsation fuel injection system with underpressure stabilizer of the present invention in the first embodiment.  
         [0013]    [0013]FIG. 2 is a schematic illustration of the movement of the compression pump of the present invention in the first embodiment.  
         [0014]    [0014]FIG. 3 is a schematic illustration of the micro-pulsation fuel injection system with underpressure stabilizer of the present invention in the second embodiment.  
         [0015]    [0015]FIG. 4 is a schematic illustration of the regulating valve of the present invention in the second embodiment in a balanced state exposed to forces.  
         [0016]    [0016]FIGS. 5 and 6 are schematic illustrations of the movement of the regulating valve of the present invention in the second embodiment.  
         [0017]    [0017]FIG. 7 is a schematic illustration of the micro-pulsation fuel injection system with underpressure stabilizer of the present invention in the third embodiment. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0018]    As shown in FIG. 1, the present invention in a first embodiment comprises: a compression pump  10 ; a fuel tank  20 ; and a micropump  30 . A bypass  11  leads into the compression pump  10 , and a backflow pipe  12  leads out of there. The bypass  11  and the backflow pipe  12  together with a fuel supply pipe  13  form a circuit. The fuel supply pipe  13  is connected with the fuel tank  20 , with an underpressure safety valve  19  placed in between. The bypass  11  leads from the fuel supply pipe  13  to the compression pump  10 . The backflow pipe  12  leads back into the fuel tank  20 . With the compression pump  10  sucking in fuel from the bypass  11  and delivering fuel via the backflow pipe  12  into the tank  20 , a closed loop of fuel flow is formed. The fuel supply pipe  13 , being connected with the bypass  11 , ends at the micropump  30 . The micropump  30  is mounted at an intake pipe  40  of an internal combustion engine, ejecting tiny droplets of fuel into the intake pipe  40 . The intake pipe  40  has an air canal  41 , in which a throttle valve  42  is placed. The air canal  41  leads to a cylinder of the internal combustion engine, with the throttle valve  42  regulating the quantity of air passing through.  
         [0019]    The compression pump  10  of the present invention sucks in fuel from the fuel tank  20  through the bypass  11 , returning fuel through the backflow pipe  12  to the fuel tank  20 , so that a closed loop is formed.  
         [0020]    Sucking of fuel from the fuel tank  20  through the bypass  11  into the compression pump  10  generates underpressure in the fuel supply pipe  13 . The supply pipe  13  is connected with an inlet  31  of the micropump  30 . Therefore, underpressure is maintained at the inlet  31  of the micropump  30 .  
         [0021]    Referring again to FIG. 1, the compression pump  10  has a case  14  having an inside which is divided by a membrane  15  into a lower half and an upper half, constituting a pressure chamber  16  and a fuel chamber  17 , respectively. A transmission tube  18  transmits pressure from the intake pipe  40  to the pressure chamber  16 . An inlet valve  171  is mounted at an entrance of the fuel chamber  17 , to which the bypass  11  is connected. An outlet valve  172  is mounted at an exit of the fuel chamber  17 , to which the backflow pipe  12  is connected. The inlet valve  171  and the outlet valve  172  are one-way valves, only allowing fluid to enter the fuel chamber  17  from the bypass  11  and to leave the fuel chamber  17  through the backflow pipe  12 .  
         [0022]    Referring to FIG. 2, movement of the compression pump  10  comes about by pressure changes in the pressure chamber  16 , which follow pressure changes in the intake pipe  40 . Due to pressure changes in the pressure chamber  16  the membrane  15  deforms slightly and elastically, changing the volume of the fuel chamber  17 . When the volume of the fuel chamber  17  increases, fuel is sucked in through the bypass  11 . On the other hand, when the volume of the fuel chamber  17  decreases, fuel is pressed out through the backflow pipe  12  and flows back into the fuel tank  20 .  
         [0023]    The movement of the compression pump  10  lies in deforming of the membrane  15  caused by pressure changes in the air canal  41  of the intake pipe  40 , which take away or apply pressure. When pressure is taken away and the membrane  15  consequently bends downward, the fuel chamber  17  expands, so that underpressure in the bypass  11  and in the fuel supply pipe  13  results. This causes underpressure in the inlet  31  of the micropump  30 , as well. When the membrane  15  is pushed on by pressure transmitted through the transmission tube  18 , the fuel chamber  17  shrinks, pressing fuel out through the backflow pipe  12 .  
         [0024]    Thus the compression pump  10  effects stable underpressure at the inlet  31  of the micropump  30 . A fixed negative difference of pressures at the inlet  31  of the micropump  30  and in the intake pipe  40  is maintained, so that no fuel will leak out of the micropump  30  and no improper quantities of fuel will be ejected. Therefore, the quantity of ejected fuel is better controlled, and combustion thereof is more effective.  
         [0025]    Referring now to FIG. 3, the present invention in a second embodiment comprises: a compression pump  10 ; a fuel tank  20 ; a micropump  30 ; and an intake pipe  40 . The structural parts and the assembly of the present invention are the same in the first and second embodiments, except for an additional regulating valve  50  in the second embodiment. The regulating valve  50  is installed between the bypass  11  and the intake pipe  40 , attenuating changes in underpressure of the bypass  11  against the intake pipe  40 , so that a fixed difference is maintained between pressures at the inlet  31  of the micropump  30  and in the intake pipe  40  for better precision of ejected fuel quantity.  
         [0026]    As shown in FIG. 3, the regulating valve  50  has a case  51  having an inside which is divided by a membrane  52  into an upper half and a lower half, constituting a pressure chamber  53  and a working liquid chamber  54 , respectively. The working liquid chamber  54  has an inlet opening  55  which is connected with the fuel supply pipe  13 , allowing fuel from the fuel tank  20  to enter the working liquid chamber  54 . The working liquid chamber  54  further has an outlet opening  56  from which a secondary fuel supply pipe  131  leads to the inlet  31  of the micropump  30 . The pressure chamber  53  is via a second transmission tube  57  connected with the intake pipe  40 . A control valve  58  is placed at inlet opening  55  of the working liquid chamber  54 , where the fuel supply pipe  13  ends. A connecting device  59  connects the control valve  58  with the membrane  52 , so that the membrane  52  drives opening and closing of the control valve  58 . A spring  60  acts on the control valve  58 , pressing the control valve  58  tight on the inlet opening  55 . As shown in FIGS. 5 and 6, the connecting device  59  comprises a first connecting rod  591 , a second connecting rod  592 , and a shaft  593 , located between the first connecting rod  591  and the second connecting rod  592 . The first connecting rod  591  contacts the membrane  52  from below and has a lower side that is pushed against by the spring  60 . The second connecting rod  592  contacts the control valve  58 . When the membrane  52  is deformed, the first connecting rod  591  is taken along, driving the control valve  58 .  
         [0027]    Referring to FIG. 4, being connected with the intake pipe  40  by the second transmission tube  57 , underpressure in the intake pipe  40  is followed by pressure in the pressure chamber  53 , generating underpressure in the pressure chamber  53 , as well, which results in a force F 1 , as indicated by arrow F 1  in the Figs. On the other hand, pressure in the working liquid chamber  54  originates at the fuel supply pipe  13 . The membrane  52  in the regulating valve  50  is on both sides exposed to forces caused by underpressure: F 1  from the intake pipe  40  and, acting opposite thereto, F 2  in the working liquid chamber  54 . In addition, a force F 3  from the spring  60  acts on the membrane  52 , being equally oriented as the force F 1 . All forces cancel each other out, creating an equilibrium state of the membrane  52 , with the force F 2  that is due to underpressure in the working liquid chamber  54  minus the force F 3  caused by the spring  60  being oppositely equal to the force F 1  that is due to underpressure in the intake pipe  40 .  
         [0028]    As shown in FIGS. 5 and 6, when the forces F 1  and F 3  combined exceed the force F 2  due to underpressure in the intake pipe  40  and the membrane  52  consequently bends upward, following F 1 , the membrane  52  drives the control valve  58  to close the inlet opening  55 . Then the working liquid chamber  54 , having received working liquid delivered by the compression pump  10 , has a pressure that is smaller than pressure at the micropump  30  by a fixed amount.  
         [0029]    On the other hand, as shown in FIG. 6, when there is a loss of fuel due to ejection by the micropump  30 , underpressure in the working liquid chamber  54  has a gradually rising value, so that the forces F 1  and F 3  combined become smaller than the force F 2 . Then the membrane  52  bends downward, opposite to the force F 1 , opening the control valve  58 , so that working liquid from the compression pump  10  enters the working liquid chamber  54 . Inflow of working liquid into the working liquid chamber  54  avoids large pressure changes when operation is started.  
         [0030]    Thus the regulating valve  50  keeps the difference of pressures at the inlet  31  of the micropump  30  and in the intake pipe  40  at a fixed negative value, which in theory is compensated by the force F 2  of the spring  60 . Changes in the difference of pressures at the inlet  31  of the micropump  30  and in the intake pipe  40  are spread out over time. Therefore the quantity of fuel ejected by the micropump  30  will not become unstable due to large pressure variation differences between inlet and outlet. Ejected fuel is effectively and precisely controlled.  
         [0031]    Comparing the first and second embodiments of the present invention, the additional regulating valve  50  of the second embodiment regulates exactly the difference of pressures at the inlet  31  of the micropump  30  and in the intake pipe  40 . Any change of the pressure difference immediately drives the membrane  52  and the control valve  58  to perform compensating movements. Therefore the difference of pressures at the inlet  31  of the micropump  30  and in the intake pipe  40  is controlled within a precise range.  
         [0032]    The regulating valve  50  of the second embodiment is usable in conjunction with all types of pumps, not necessarily having to be combined with the compression pump  10 . As shown in FIG. 7, in a third embodiment of the present invention, the regulating valve  50  is used in conjunction with a sucking pump  70 . The sucking pump  70  is via a connecting pipe  71  connected with the tank  20 . Fuel from the tank  20  is sucked through the connecting pipe  71 , so that underpressure develops therein. A fuel supply pipe  72  branches off the connecting pipe  71 , leading to the inlet opening  55  of the regulating valve  50 . Thus underpressure in the working liquid chamber  54  of the regulating valve  50  is generated by the sucking pump  70 . The sucking pump  70  used in this embodiment is not necessarily a micropump. Blade pumps, drum pumps or other types of pumps are usable therefor, as well.  
         [0033]    While the invention has been described with reference to preferred embodiments thereof, it is to be understood that modifications or variations may be easily made without departing from the spirit of this invention which is defined by the appended claims.