Patent Document

BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a starting device for delivering starting fuel using a manually operated primary pump to start an engine, and a carburetor using same. 
         [0003]    2. Description of the Related Art 
         [0004]    Known starting devices for carburetors include those that use a choke value, or those in which the engine is started by feeding a rich mixture into the engine using the bystart method or a pump that utilizes the pulse pressure of the engine. In starting devices of such description, the fuel is drawn out from the carburetor after a starting operation is performed by the operator using a recoil rope or another method and negative pressure is generated in the engine. Since it is necessary to perform the starting operation repeatedly until the fuel reaches the intake manifold, the crankcase, the scavenging passage, and the fuel chamber, the operator is subjected to a laborious workload. 
         [0005]    Meanwhile, carburetors for supplying fuel to general-purpose engines provided to lawnmowers, small watercraft, and similar applications are conventionally equipped with a carburetor starting device having a manually operated primary pump in which a suction valve/discharge valve and a cup-shaped container made from an elastic resin are combined, as described in, e.g., JP-A 2003-254164. 
         [0006]    In a carburetor provided with a starting device of such description, the operator can use the primary pump to deliver fuel to the intake manifold or the crank case before performing the starting operation, and the engine can be started by a relatively concise starting operation. However, this method presents a problem in that if the primary pump is actuated excessively, the engine becomes flooded by fuel, making it difficult to start the engine. 
       SUMMARY OF THE INVENTION 
       [0007]    The preset invention is intended to resolve the types of problems described above, and is aimed at making it possible to deliver an appropriate quantity of starting fuel through a simple operation and obtaining a satisfactory engine starting performance in relation to an engine starting device comprising a manually operated primary pump. 
         [0008]    In order to solve the above problem, the present invention is a starting device comprising: a manually operated primary pump for suctioning/pumping fuel, the primary pump being arranged on a fuel introduction path connected partway along a path for feeding fuel to an engine; and a fixed-quantity fuel chamber for temporarily storing fuel that has been delivered from the primary pump; the starting device feeding a fixed quantity of starting fuel from the fixed-quantity fuel chamber to an intake passage of the engine during engine start-up; wherein at least a part of an internal wall of the fixed-quantity fuel chamber undergoes elastic displacement, allowing the internal capacity of the fixed-quantity fuel chamber to expand/shrink within a predetermined range; the fixed-quantity fuel chamber is connected to a fuel delivery path that communicates with the intake passage side, the fuel delivery path having a manually operated open/close valve provided partway therealong; the open/close valve of the fuel delivery path is manually opened in a state in which, due to the primary pump being operated, the fixed-quantity fuel chamber is filled with a predetermined quantity of starting fuel while the internal capacity of the fixed-quantity fuel chamber is enlarged, whereby the fixed-quantity fuel chamber shrinks due to an elastic contraction force and discharges a given quantity of starting fuel to a side towards the intake passage via the fuel delivery path. 
         [0009]    Thus, the starting device has a configuration in which a fixed-quantity fuel chamber, which has a function of discharging stored fuel using an elastic contraction force and of feeding a given quantity of starting fuel to the engine, is arranged downstream in relation to the primary pump; and manually opening an open/close valve, which blocks the fuel delivery path downstream of the fixed-quantity fuel chamber, feeds a given quantity of starting fuel. An appropriate quantity of starting fuel is thereby fed to the engine through a simple operation. 
         [0010]    Also, in the starting device described above, if a fuel-ejecting path for ejecting excess fuel extends from the fixed-quantity fuel chamber and has a constricted section, which is narrower than a narrowest portion of the fuel delivery path; wherein excess fuel charged into the fixed-quantity fuel chamber by excessive operation of the primary pump is ejected, then an appropriate quantity of starting fuel can be readily fed while facilitating the task of filling the fixed-quantity fuel chamber using the primary pump. 
         [0011]    Also, the fixed-quantity fuel chamber may be equipped with a locking means, which serves as a stopper for locking the internal wall that has undergone displacement to an extent at which the internal capacity has expanded to a predetermined level, the internal wall being locked at the associated position, and for automatically stopping operation of the interior wall in the direction of contraction; wherein, in association with the open/close valve being opened, a state of locking applied by the locking means is cancelled, the fixed-quantity fuel chamber is caused to contract, and the starting fuel is discharged. The operation of discharging the starting fuel can thereby be satisfactorily performed. 
         [0012]    Also, a carburetor may be integrally equipped with the starting device described above, whereby merely providing the carburetor to a fuel-feeding system for an engine will make it possible for the functions described above to be realized. 
         [0013]    According to the present invention, in which a fixed-quantity fuel chamber for discharging fuel using an elastic contraction force is arranged downstream in relation to the primary pump, and manually opening the open/close valve in the fuel delivery path causes a given quantity of starting fuel to be fed, it is possible to deliver an appropriate quantity of starting fuel through a simple operation and to obtain a satisfactory engine starting performance. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  is a partial vertical cross-section view of a carburetor equipped with a starting device according to the present embodiment; 
           [0015]      FIGS. 2(A) ,  2 (B), and  2 (C) are expanded vertical cross-section views used to illustrate the operation of the starting device shown in  FIG. 1 ; 
           [0016]      FIG. 3  is a partial vertical cross-section view of a carburetor equipped with a variation of the starting device shown in  FIG. 1 ; and 
           [0017]      FIGS. 4(A) ,  4 (B), and  4 (C) are expanded vertical cross-section views used to illustrate the operation of the starting device shown in  FIG. 3 . 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0018]    Embodiments of the present invention are described below with reference to the accompanying drawings. 
         [0019]      FIG. 1  shows a partial vertical cross-section view of a carburetor  1 A, integrally equipped with a starting device according to the present embodiment. The configuration of the carburetor portion, which is penetrated by an intake passage  2  and which feeds vaporized fuel using a fuel nozzle, is the same as conventional examples. Therefore, a detailed description of the carburetor portion will not be provided, and a detailed description will be provided for the configuration of the accompanying starting device portion. 
         [0020]    A primary pump  8 , which has an introduction valve and a discharge valve on the inside and a cup-shaped member formed from an elastic resin and exposed outwards, is provided partway along a fuel introduction path  10   a  extending from a metering chamber  3  of the carburetor portion. The fuel introduction path  10   a  extending from the primary pump  8  is connected to a fixed-quantity fuel chamber  5 A of the starting device portion provided below the metering chamber  3 . By manually operating the primary pump  8 , it is possible to suction/pump fuel from the metering chamber  3 , and introduce/charge the fuel into the fixed-quantity fuel chamber  5 A as starter fuel. 
         [0021]    One of the surfaces that form the internal wall of the fixed-quantity fuel chamber  5 A is formed from a diaphragm  52 . A chamber on the opposite side of the diaphragm  52  has a guide rod  6  formed of, e.g., a metal, protruding from the center of the diaphragm  52 . A coil-shaped diaphragm spring  51  is disposed in a compressed state between the diaphragm  52  and the top wall, in a state of being penetrated by the guide rod  6 ; and the diaphragm  52  is urged by the diaphragm spring  51  in the direction of contraction of the fixed-quantity fuel chamber  5 A. Therefore, the fixed-quantity fuel chamber  5 A is capable of deforming in an elastic manner accompanied by a displacement, in the vertical direction shown in the drawing, of the internal wall formed by the diaphragm  52 ; and of expanding/shrinking within a predetermined range in terms of internal capacity. 
         [0022]    A fuel delivery path  11   a , which communicates with the side towards the intake passage  2 , extends from the fixed-quantity fuel chamber  5 A. An open/close valve  4   a , which is opened by pressing a manually operated starting bar  7 A and automatically closed by a valve spring  41 , is provided partway along the fuel delivery path  11   a . Manually opening the open/close valve  4   a  in a state in which the fixed-quantity fuel chamber  5 A is expanded in terms of internal capacity and filled with a predetermined quantity of starting fuel causes a given quantity of starting fuel to be discharged towards the side towards the intake passage and fed to the engine. 
         [0023]    The distal-end side of the guide rod  6 , which protrudes from the center of the aforedescribed diaphragm  52 , has a notch  61  formed along the circumferential direction. The distal end of the guide rod  6  penetrates through to a space partitioned off by the top wall against which the diaphragm spring  51  is in contact. In the side towards the space partitioned off as described above, a plate-shaped stopper  71 , which has an elliptical insertion hole  71   a  formed at the center in the direction perpendicular to the central axis of the guide rod  6 , is provided so that the distal-end side of the guide rod  6  penetrates the insertion hole  71   a  and the stopper  71  is capable of sliding in the direction perpendicular to the direction of penetration. 
         [0024]    A distal-end side of the starting bar  7 A, which has been inserted from the side surface of the starting device portion, connects to the base-end side of the stopper  71 . The distal-end side of the starting bar  7 A is exposed to the outside, forming a grip for manual operation. The starting bar  7 A is urged by a coil spring  75  in an outward direction along the central axis. 
         [0025]    The edge of the insertion hole  71   a  of the stopper  71  and the notch  61  of the guide rod  6  form locking means, which is a stopper for locking the position of the diaphragm  52  so as to maintain the state in which the fixed-quantity fuel chamber is filled with the starting fuel. When the internal capacity of the fixed-quantity fuel chamber  5 A has expanded to a predetermined level, i.e., when the guide rod  6  has moved upwards to a point at which the notch  61  reaches the height of the stopper  71 , the urging force applied by the coil spring  75  causes the starting bar  7 A and the stopper  71  to be operated in the withdrawing direction and the edge of the insertion hole  71   a  to enter and engage with the notch  61 . The movement of the guide rod  6  along the direction of the central axis is thereby locked at this position, and the operation of the fixed-quantity fuel chamber  5 A in the direction of contraction is automatically stopped. 
         [0026]    Next, the operation of the starting device according to the present embodiment will be described with reference to  FIG. 2 . Looking at  FIG. 2(A) , fuel that has been suctioned from the metering chamber  3  by manual operation of the primary pump  8  is introduced through the fuel introduction path  10   a  into the fixed-quantity fuel chamber  5 A and stored as starting fuel. 
         [0027]    Then, operating the primary pump  8  increases the internal capacity of the fixed-quantity fuel chamber  5 A, causing the diaphragm  52  to displace upwards while the diaphragm spring  51  is compressed. When the diaphragm  52  approaches the upper limit position, the distal-end-side edge of the insertion hole  71   a  of the stopper  71  engages with the notch  61  of the guide rod  6  as shown in  FIG. 2(B) , immobilizing the guide rod  6  in this state, and maintaining a state in which a given amount of fuel is stored. 
         [0028]    Subsequently operating the primary pump  8  causes the pressure within the fixed-quantity fuel chamber  5 A to exceed a predetermined level, and the excess starting fuel to be ejected towards a fuel tank (not shown) through a fuel ejection path  12   a , in which a constricted section is formed. In this instance, an increase in resistance against the primary pump  8  being pressed allows the operator to detect the fixed-quantity fuel chamber  5 A reaching a state of being filled with the starting fuel to a sufficient level and the position of the diaphragm  52  being immobilized by the stopper  71 . 
         [0029]    Then, as shown in  FIG. 2(C) , the operator presses the portion of the starting bar  7 A that is exposed to the outside (i.e., the starting button), whereby the stopper  71  disengages from the guide rod  6  and the resistance force from the diaphragm spring  51  compresses the starting fuel stored in the fixed-quantity fuel chamber  5 A. At the same time, the distal-end-side of the stopper  71  comes into contact with the distal-end-side of the open/close valve  4   a  arranged in the fuel delivery path  11   a , acts against the urging force from the valve spring  41 , and opens the open/close valve  4   a . The starting fuel stored in the fixed-quantity fuel chamber  5 A is forced out towards the side towards the intake passage through the fuel delivery path  11   a.    
         [0030]    Due to the procedure described above, a given quantity of the starting fuel is fed to the engine during engine start-up, and even if the operator operates the primary pump  8  excessively, the excess fuel merely returns to the fuel tank, and there is no risk of the engine being fouled. It is thereby possible to obtain a satisfactory engine starting performance at all times through a simple operation. 
         [0031]      FIG. 3  shows an example of a variation of the embodiment described above, and shows a configuration of a starting device that is not provided with means for locking the diaphragm  53 . In this example, as shown in  FIG. 4(A) , the open/close valve  73  is directly provided on the distal-end-side of the starting bar  7 B, the stopper  71  and the guide rod  6  are not provided, and the configuration is simpler than that according to the previous example. 
         [0032]    As with the previous example, the operator presses the primary pump  8 , causing a predetermined quantity of starting fuel to be stored in the fixed-quantity fuel chamber  5 B as shown in  FIG. 4(B) ; and continues to press the primary pump  8 , causing excess fuel to be ejected from the fuel ejection path  12   b  provided with a constricted section. However, in this example, the starting fuel compressed by the diaphragm spring  54  is, over time, caused to pass through the constricted section and be gradually ejected through the fuel ejection path  12   b . Therefore, when the operator detects, from the resistance on the primary pump  8  or another indicator, the fixed-quantity fuel chamber  5 B reaching a state of being filled with the starting fuel to a sufficient degree, the operator is required to press the starting bar  7 B within a predetermined time. 
         [0033]    The operator pressing the starting bar  7 B in a state in which a predetermined quantity of starting fuel is stored in the fixed-quantity fuel chamber  5 B causes the fuel delivery path  11   b  to open and the starting fuel to be fed to the engine as shown in  FIG. 4(C) . With regards to this example of variation and the embodiment described above, a description has been given for a starting device that is integrated with a carburetor; however, this arrangement is not provided by way of limitation. The starting device portion may be provided, separately from the carburetor, to the fuel-feeding system of the engine. 
         [0034]    As described above, the present invention makes it possible to deliver an appropriate quantity of starting fuel through a simple operation and to obtain a satisfactory engine starting performance in relation to an engine starting device comprising a manually operated primary pump. 
       KEY 
       [0000]    
       
           1 A Carburetor 
           2  Intake passage 
           4 A,  72  Open/close valve 
           5 A,  5 B Fixed-quantity fuel chamber 
           6  Guide rod 
           7 A,  7 B Starting bar 
           8  Primary pump 
           10   a  Fuel introduction path 
           11   a  Fuel delivery path 
           12   a  Fuel ejection path 
           52 ,  53  Diaphragm 
           61  Notch 
           71  Stopper 
           71   a  Insertion hole

Technology Category: 2