Abstract:
An engine working machine that has an electronically controlled fuel injection system and a fuel tank disposed in an upper portion. The capacity of the fuel tank is effectively used and a complex structure is prevented while reducing the length of the fuel piping. An engine is disposed in a lower portion, and a fuel tank is disposed above the engine. A fuel pump is mounted on a bottom outside surface of the fuel tank, and disposed projecting on a side portion of the crankcase. An extended box is provided on a bottom surface of the fuel tank, and the fuel pump is mounted with a filter and a fuel intake port located inside the extended box. The fuel pump is housed in a pump case that is fixed to a bottom surface of the extended box.

Description:
TECHNICAL FIELD 
     The present invention relates to an engine working machine which is driven by an engine as a power source, and particularly, to an engine working machine which is characterized by an arrangement of a pump that supplies an engine with fuel under pressure. 
     BACKGROUND ART 
     Engine working machine such as a generator or a water pump powered by engine, in which a fuel tank is mounted on a frame made of a pipe in a manner to cover an upper surface of the engine and working machine is known (Refer to Patent Document 1). Generator in which a fuel tank is disposed in an upper portion of a frame, and an engine cylinder is disposed oriented in an oblique direction within the frame is also known (Refer to Patent Document 2). 
     CITATION LIST 
     Patent Literature 
     
         
         Patent Literature 1 Japanese Unexamined Patent Application Publication No. 10-196391 
         Patent Literature 2 Japanese Unexamined Patent Application Publication No. 11-343860 
       
    
     SUMMARY OF INVENTION 
     Technical Problem 
     As described in Patent Documents 1 and 2, the fuel tank disposed in an upper portion of the frame serves as an upper cover that covers an upper portion of an engine and working machine body (e.g. generator, water pump), and can protect the engine working machine against water drops, dust, etc., that fall on the engine and working machine body from above. The fuel tank performs such a function and is thus desirably disposed in an upper portion of the engine working machine. 
     When using an electronically controlled fuel injection system for an engine, it is necessary to determine the position of a fuel pump that supplies fuel under pressure to a fuel injection valve. Typically, the fuel pump is mounted on an upper surface inside the fuel tank, in such positioning, however, the length of the fuel piping is lengthened, and there arises a problem of insulation from operating noise of the fuel pump, waterproofing of the piping, and protection from external force. On the other hand, when the fuel pump is disposed on a lower surface inside the fuel tank, there has been a problem such that fuel in the fuel tank cannot be used up unless a fuel intake port and a filter are transversely positioned and the fuel pump is disposed on a lowermost surface inside the fuel tank, and the fuel pump has a complex mounting structure in a case where the fuel intake port and filter are located downward. 
     It is an object of the present invention to provide, in response to the problems described above, an engine powered working machine which enables a fuel pump arrangement that allows effective use of the capacity of the fuel pump and prevents a complex structure. 
     Solution to Problem 
     A first feature of the present invention is that an engine working machine including an electronically controlled fuel injection system for which an engine and a working machine are disposed in a lower portion, and a fuel tank is disposed above the engine and the working machine, the engine working machine comprising a fuel pump mounted on a bottom surface of the fuel tank from outside. 
     A second feature of the present invention is that the engine is formed of a crankcase and a cylinder head that extends obliquely upward from the crankcase toward a bottom surface of the fuel tank, and the fuel pump is disposed to overhang a side portion of the crankcase located lower than the cylinder head. 
     A third feature of the present invention is the engine working machine comprising an extended portion formed on a bottom surface of the fuel tank, wherein the fuel pump is mounted on the extended portion with a filter and a fuel intake port located inside the extended portion. 
     A fourth feature of the present invention is that the fuel pump is housed in a pump case, and the pump case is fixed to a bottom surface of the fuel tank or the extended portion. 
     A fifth feature of the present invention is that the pump case has an external form of a cylinder body on which a flange is provided, an inner cylinder body is further provided at an inside of the cylinder body, the inner cylinder body holds the fuel pump, and the flange is bolted to a bottom surface of the fuel tank or the extended portion with sealing means interposed. 
     A sixth feature of the present invention is that the inner cylinder body is communicated at its upside with a fuel tank and is sealed by a cap at its downside, and a discharge port of the fuel pump held by the inner cylinder body projects into a buffer space formed between the inner cylinder body and the cap. 
     A seventh feature of the present invention is that a pressure regulator is mounted in the buffer space, and the pressure regulator is provided with a tube to return a back pressure to a gaseous phase. 
     An eighth feature of the present invention is that the working machine is a generator or a water pump that is driven by an engine. 
     Advantageous Effects of Invention 
     According to the present invention having the first to eighth features described above, the fuel pump can be disposed effectively using a space formed between a complex external outline of the engine, working machine, etc., and the bottom surface of the fuel tank having a simple external outline. 
     According to the present invention having the second feature, the fuel pump can be disposed in a larger space formed between the bottom surface of the fuel tank and the engine. 
     According to the present invention having the third feature, since the filter etc., of the fuel pump can be housed in the expansion chamber, the capacity of the fuel tank can fully be used. 
     According to the present invention having the fourth feature, since the fuel pump can be held by use of the pump case, the mounting structure to the fuel tank can be arbitrarily selected. 
     According to the present invention having the fifth feature, since the fuel pump is freely mountable and dismountable with respect to the fuel pump, maintenance work is easy. 
     According to the present invention having the sixth feature, since fuel discharged from the fuel pump can be supplied to the exterior via the buffer space, the supply pressure can be stabilized. 
     According to the present invention having the seventh feature, the discharge pressure can be further stabilized by returning the back pressure of the pressure regulator to a gaseous phase. 
     According to the present invention having the eighth feature, the fuel pump can be disposed effectively using a space formed between the working machine, such as an engine-driven generator or water pump, whose external form or outline is complex and highly irregular and the fuel tank generally having a flat bottom surface. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view of an engine generator according to an embodiment of the present invention. 
         FIG. 2  is a front view of the engine generator. 
         FIG. 3  is a front view of an engine generator according to a second embodiment. 
         FIG. 4  is a sectional view of a fuel pump of an engine generator according to a third embodiment. 
         FIG. 5  is a perspective view showing an interior of a pump case. 
         FIG. 6  is a perspective view showing an external appearance of an upper portion of the pump case. 
         FIG. 7  is a perspective view showing an external appearance of a lower portion of the pump case. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, an embodiment of the present invention will be described with reference to the drawings.  FIG. 1  is a perspective view of an engine generator which is an engine powered working machine according to an embodiment of the present invention. The engine generator  1  includes wheels WF so as to be movable. In the present specification, the side on which the wheels WF are provided is referred to as a “front” of the engine generator  1 , and the direction in which the wheels WF have axles extended is referred to as a “width direction.” 
     The engine generator  1  includes a generator frame  7  formed of a main frame  2  made of a pipe, a pair of upper sub-frames  3 ,  3  extending to the front and rear in an upper portion of the main frame  2 , a front sub-frame  4  extending in the width direction in a lower portion of the main frame  2 , a pair of bottom sub-frames  5 ,  5  extending in the width direction in the lower portion of the main frame  2 , and a tank support frame  6  both ends of which are connected to four corners of the main frame  2  at locations closer to the upside of the main frame  2 , respectively. 
     One of the bottom sub-frames  5 ,  5  that is closer to the front supports an axle  8  of the wheel WF, and the other of the bottom sub-frames  5 ,  5  that is closer to the rear supports a pair of stands  9  (only one of them is shown) disposed separated in the width direction. 
     The bottom sub-frames  5 ,  5  further carry an engine  10  and a generator  11  placed thereon. An air cleaner  13  is disposed in the rear of a cylinder head  12  of the engine  10 , and a muffler  14  is disposed at one side of the generator  11  (left side when viewed from the rear of the engine generator  1 ). At the other side (right side when viewed from the rear of the engine generator  1 ) of the generator  11 , an operation panel  15  (a back side of which is shown) including a control unit and a display unit is disposed. 
     The tank support frame  6  is provided with brackets (not shown) at four corners, and by fixing four sites of a top-bottom mating portion that overhangs circumferentially from the middle in an upper and lower direction of a fuel tank  16  to the brackets by use of bolt-and-nut  17  sets, the fuel tank  16  is carried on the generator frame  7 . 
     The pair of upper sub-frames  3 ,  3  have handles  19 ,  19  that are attached by use of clamps  18 ,  18 , respectively. End portions of the handles  19 ,  19  are covered with rubber grips  20 ,  20  that can be gripped by an operator. 
     The engine generator  1  having this configuration includes a known recoil starter (not shown) of the engine  10  that is adjacent to the right side of the air cleaner  13 , and the engine  10  is rotated by pulling a rope of the recoil starter. The generator  11  rotates to generate power when the engine  10  is rotated by the recoil starter, a fuel pump (described later in detail) is driven by the control unit that is being started by the generated power, and fuel is supplied under pressure from the fuel tank  16  to a fuel injection valve (not shown) of the engine  10  responsive to an ignition signal of the engine  10  being output. The engine  10  is started when the fuel is fed together with air to a combustion chamber according to the fuel injection valve opening at a predetermined timing and the mixture is ignited by an ignition device (not shown). When the engine  10  starts, the generator  11  starts power generation, conventionally known control is performed to continue the power generating operation, and an output voltage of the generator  11  is connected to a predetermined output end (outlet or socket). The outlet may be provided on an operation panel  15 . 
     Next, a fuel pump to be mounted on the fuel tank  16  will be described.  FIG. 2  is a front view of the engine generator  1 . In  FIG. 2 , the engine  10  is formed of a crankcase  21  and a cylinder head  12  that sticks out obliquely upward from the crankcase  21  toward a bottom surface of the fuel tank  16 . The fuel tank  16  is located above the engine  10  and generator  11 . Because the bottom surface of the fuel tank  16  is flat, it looks as if there were no large space between the engine  10  and generator  11  and the fuel tank  16 , but a relatively large space exists between the fuel tank  16  having a flat bottom surface and the engine  10  and generator  11  whose external form or outline is irregular. Particularly, the cylinder head  12  sticks out obliquely upward and thus has a small gap with the fuel tank  16 , but the outer peripheral shape of the crankcase  21  is an arc, the crankcase  21  is located lower than the cylinder head  12 , and there is thus a relatively large space produced between the crankcase  21  and the fuel tank  16 . Therefore, a fuel pump  22  is disposed in the space produced between the crankcase  21  and the fuel tank  16 . 
     To the bottom surface of the fuel tank  16 , an extended portion (expansion box)  23  of the fuel tank  16  is joined, and the fuel pump  22  whose external form is generally cylindrical is mounted from below on the extended box  23 . The fuel pump  22  has a fuel intake port  24  facing the interior of the expansion box  23 , and a filter  25  attached to the fuel intake port  24  is housed inside the expansion box  23 . Since the fuel intake port  24  and the filter  25  are located inside the expansion box  23  extended downward from the fuel tank  16 , the capacity of the fuel tank  16  can be effectively used. The fuel pump  22  is connected at a discharge port with a fuel pipe  26 , and an end portion of the fuel pipe  26  is connected to a fuel injection valve (injector)  27  provided in the engine  10 . 
       FIG. 3  is a view showing a modification (second embodiment) of a mounting mode of a fuel pump, and the same reference signs as those in  FIG. 2  denote the same or equivalent parts. In the example of  FIG. 3 , the expansion box  23  is extended further downward to expand the capacity of the expansion box  23 . The capacity of the fuel tank  16  is substantially expanded by using the space produced between the crankcase  21  and the fuel tank  16  as large as possible. Unlike the case of supplying fuel by a carburetor system, since the fuel pump  22  can be at any height position in the engine  10  including a fuel injection system, the expansion box  23  can be extended downward so far as the space permits to secure a larger fuel retention capacity. 
       FIG. 4  is a sectional view of a fuel pump according to a third embodiment of the present invention.  FIG. 5  is a perspective view showing an interior of a pump case, FIG.  6  is a perspective view of a case body of the pump case viewed from above,  FIG. 7  is a perspective view of the case body  31  viewed from below, and the same reference signs as those in  FIG. 4  denote the same or equivalent parts. 
     In  FIG. 4  to  FIG. 7 , the fuel pump  22  is housed in a pump case  30  and mounted on the fuel tank  16 . The pump case  30  consists of a case body  31  and a cap  32  that covers a bottom portion of the case body  31 , and a flange  33  for mounting is provided at an upper portion of the case body  31 . On the other hand, a mounting seat (annular plate)  34  that receives the flange  33  of the case body  31  is joined by a method such as welding to the bottom surface of the fuel tank  16 . 
     The mounting seat  34  includes female screws  35  at a plurality of sites (for example, four sites), and bolts  36  inserted through bolt through-holes  29  provided in the flange  33  of the case body  31  so as to be aligned with the female screws  35  are screwed in the female screws  35 , respectively. The flange  33  includes a seal groove formed on a surface opposed to the mounting seat  34 , and seal between the flange  33  and the mounting seat  34  is secured by an O-ring  37  that fits in the seal groove. 
     The case body  31  is a cylinder body, and further includes in its interior an inner cylinder body  38  that holds the fuel pump  22 . The inner cylinder body  38  is provided eccentrically with respect to an axis of the cylindrical case body  31 , and has an inner diameter “d” that is adapted to the external size of the fuel pump  22 . The inner cylinder body  38  is open at the top and bottom, and the fuel intake port  24  passes through the open part of the upper portion and the filter  25  is attached to the end of the fuel intake port  24 , that is, the side of the fuel tank  16 . 
     The surroundings of the inner cylinder body  38  are open at an upper portion to communicate with the fuel tank  16 , and a lower portion thereof excluding a regulator housing portion  39  is closed. The regulator housing portion  39  is a cylinder body extending parallel to the inner cylinder body  38 , and houses a pressure regulator  40 . The pressure regulator  40  can have a well-known structure formed of a valve and a spring. The regulator housing portion  39  is covered with a pressure stabilizing tube  41 . The pressure stabilizing tube  41  is extended to the inside of the fuel tank  16 , and performs a function of returning the back pressure of the pressure regulator  40  to a gaseous phase. Returning the back pressure of the pressure regulator  40  to a gaseous phase allows stabilization of the discharge pressure of the fuel pump  22 . It is preferable to provide the pressure stabilizing tube  41  in the sense of better stabilization of the discharge pressure, but the pressure stabilizing tube  41  is not essential. 
     The cap  32  includes a connector portion  42  to which the fuel pipe  26  is joined. The cap  32  also includes an electrode  45  for connecting a lead wire  43  that supplies a drive motor (not shown) of the fuel pump  22  with electricity to an external harness  44 . It is preferable to mold the electrode  45  integrally with the cap  32 . 
     In the third embodiment, an example of the pump case  30  mounted on the bottom surface  16  has been shown, but this structure may be applied to the first and second embodiments so as to mount the pump case  30  housing the fuel pump  22  on a bottom surface of the expansion box  23 . 
     During operation of the fuel pump  22 , the fuel inside the fuel tank  16  passes through the filter  25  located at a lowermost portion of the fuel tank  16 , and is introduced into the fuel pump  22  from the fuel intake port  24 . Then, the fuel discharged from the discharge port  46  is retained in a space (buffer)  47  between the case body  31  and the cap  32 . The pressure of the fuel retained in the buffer  47  is regulated to a constant pressure by the pressure regulator  40 . Further, the fuel is discharged from the connector portion  42  of the cap  32 , and fed to the injector  27  through the fuel pipe  26  described above. 
     Although the present invention has been described in accordance with the embodiments, the present invention is not limited to these embodiments, and modifications can be made based on the matters described in the claims and the known art. For example, it suffices that the fuel pump  22  is disposed in a manner projecting in the space between the fuel tank  16  and the engine  10  and generator  11 , without limitation to providing at a position close to a bottom portion of the crankcase  21 . Moreover, the engine working machine is not limited to a generator that is driven by an engine, and may be a water pump that is driven by an engine. 
     REFERENCE SIGNS LIST 
     
         
         
           
               1  . . . engine generator 
               2  . . . main frame 
               7  . . . generator frame 
               12  . . . cylinder head 
               16  . . . fuel tank 
               21  . . . crankcase 
               22  . . . fuel pump 
               23  . . . extended box 
               24  . . . fuel intake port 
               25  . . . filter 
               26  . . . fuel pipe 
               27  . . . fuel injection valve (injector) 
               30  . . . pump case 
               31  . . . case body 
               32  . . . cap 
               34  . . . mounting seat (annular plate) 
               38  . . . inner cylinder body 
               40  . . . pressure regulator 
               45  . . . electrode 
               46  . . . discharge port 
               47  . . . buffer