Abstract:
An engine generator has an opening and closing mechanism including: a control shaft provided to a valve shaft of a choke valve to be rotatable relative thereto within a predetermined angular range; an urging member urging the valve shaft relative to the control shaft in a direction in which an opening degree of the choke valve decreases; a restriction mechanism that sets a minimum opening degree of the choke valve by restricting a range of rotation of the control shaft; a choke operating portion which, upon operation, drives the restriction mechanism in a direction in which the minimum opening degree of the choke valve decreases; and a negative pressure mechanism driven by a negative pressure generated during an operation of the engine to cause the control shaft to rotate to increase the minimum opening degree of the choke valve within the range of rotation restricted by the restriction mechanism.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to an engine generator. 
       BACKGROUND OF THE INVENTION 
       [0002]    Portable engine generators having an engine, a generator and a fuel tank arranged in a housing are widely used. To improve operability when starting the engine, some of such engine generators are configured such that a starter handle which is an operating portion of the recoil starter of the engine, a choke operating portion which is an operating portion of the choke valve, and a cock operating portion which is an operating portion of the fuel cock provided to the fuel pipe connecting the fuel tank and the engine with each other are positioned close to each other and arranged in a prescribed region of a side face of the housing (for example, JP2006-161692A). In these engine generators, the choke valve and the choke operating portion are connected by a push-pull cable to provide the choke operating portion on the side face of the housing. Further, to provide the cock operating portion on the side face of the housing, a part of the fuel pipe is disposed in the vicinity of the side face of the housing and the fuel cock is provided to this part. 
         [0003]    In an engine that requires manual operation of the choke operating portion when starting the engine, it is necessary to return the choke operating portion to the initial position by manual operation after the engine is warmed up. If this operation is forgotten, the engine may be operated at an air-fuel ratio that results in excessive fuel, leading to deterioration in fuel efficiency and/or engine stall. To enable such a choke operation to be omitted, various automatic choke systems have been conceived (for example, JP2007-162576A). 
         [0004]    However, the automatic choke systems as disclosed in JP2007-162576A are complex in structure and have many component parts, which results in a higher cost and lower serviceablity. Further, users cannot engage in the choke operation in the automatic choke systems, and this may be frustrating to users who want to operate the choke themselves. For this reason, it would be preferred that the users are allowed to manually operate the choke while the system automatically adjust the air-fuel ratio to compensate for any deficiencies caused by the manual operation, to thereby suppress occurrence of engine stall or the like. Also, if a half choke (half open) and a full choke (fully closed) can be selected depending on situations, such as when the engine is cold or after a long period of storage, the startability of the engine is improved. 
       SUMMARY OF THE INVENTION 
       [0005]    In view of the above background, an object of the present invention is to make it possible, in an engine generator having a manually operable choke valve, to allow the opening degree of the choke valve to be varied in accordance with a variation of the load during chocking. 
         [0006]    To achieve the above object, one aspect of the present invention provides an engine generator ( 1 ) comprising: a housing ( 2 ); an engine ( 3 ) and a generator ( 4 ) driven by the engine, the engine and the generator being disposed in the housing; a choke valve ( 23 ) provided in an intake system ( 13 ) of the engine; and an opening and closing mechanism ( 30 ) for driving the choke valve, wherein the opening and closing mechanism comprises: a control shaft ( 31 ) provided to a valve shaft of the choke valve to be rotatable relative to the valve shaft within a predetermined angular range; a first urging member ( 35 ) that is provided between the valve shaft and the control shaft and urges the valve shaft relative to the control shaft in a direction in which an opening degree of the choke valve decreases; a restriction mechanism ( 32 ) that sets a minimum opening degree of the choke valve by restricting a range of rotation of the control shaft; a choke operating portion ( 72 ) that is disposed on an outer surface ( 2 A) of the housing and is connected with the restriction mechanism via a connection member ( 71 ), such that, upon operation, the choke operating portion drives the restriction mechanism in a direction in which the minimum opening degree of the choke valve decreases; and a negative pressure mechanism ( 33 ) that is driven by a negative pressure generated in the intake system or a crankcase of the engine during an operation of the engine to cause the control shaft to rotate in a direction in which the minimum opening degree increases within the range of rotation restricted by the restriction mechanism. 
         [0007]    According to this structure, the restriction mechanism restricts the range of rotation of the control shaft to set the minimum opening degree of the choke valve, and the choke valve is urged relative to the control shaft in the closing direction by the first urging member. Therefore, the user can move the choke valve in the closing direction by operating the choke operating portion. Further, as the choke valve is provided to be rotatable relative to the control shaft, the choke valve can open in accordance with the negative pressure generated downstream of the choke valve, irrespective of the position of the control shaft. Thereby, regardless of the operation of the choke operating portion by the user, the choke valve can open depending on the load of the engine, whereby an engine stall or deterioration of fuel efficiency becomes less likely to occur. Further, after the engine is started (warmed up), the negative pressure mechanism, utilizing the negative pressure generated in the intake system and the crankcase due to an operation of the engine, causes the control shaft to rotate in the direction in which the minimum opening degree of the choke valve increases within the range of rotation restricted by the restriction mechanism, whereby the choke valve is opened regardless of the negative pressure generated downstream thereof. This reduces the pumping loss and improves the fuel efficiency. The choke operating portion is connected with the restriction mechanism via the connection member, whereby the choke valve disposed inside the housing can be operated from outside the housing. 
         [0008]    In the engine generator described above, preferably, the opening and closing mechanism includes a framework member ( 40 ) attached to the engine, and the restriction mechanism includes: a restriction mechanism lever ( 62 ) rotatably supported by the framework member and having one end connected with the connection member; a restriction member ( 67 ) provided to the restriction mechanism lever and restricting the range of rotation of the control shaft; a second urging member ( 63 ) that urges the restriction mechanism lever relative to the framework member and generates a rotational resistance between the restriction mechanism lever and the framework member, the rotational resistance being derived from a frictional force; and an adjustment member ( 65 ) that adjusts a preload applied to the second urging member. 
         [0009]    According to this structure, the frictional force generated between the restriction mechanism lever and the framework member retains the position of the restriction member. This makes it possible to prevent the restriction member from moving due to operation of the negative pressure mechanism and to allow the restriction mechanism lever and the restriction member to move only when the choke operating portion is operated by the user. Accordingly, the minimum opening degree of the choke valve is maintained until the user operates the choke operating portion. Further, the frictional force generated at the restriction mechanism lever can be varied by operating the adjustment member, and therefore, this opening and closing mechanism can be applied to a variety of engines having different displacements. 
         [0010]    Further, in the engine generator described above, preferably, the negative pressure mechanism includes: a diaphragm actuator including a main body whose interior is divided into chambers by a diaphragm such that a negative pressure is supplied to one of the chambers, and a rod connected with the diaphragm; and a negative pressure mechanism lever rotatably supported by the framework member and connected with one end of the rod and with the control shaft. Thereby, the negative pressure mechanism can be realized by a simple structure. 
         [0011]    Further, in the engine generator described above, preferably, the restriction mechanism restricts the range of rotation of the control shaft such that the minimum opening degree of the choke valve is set to half open when the choke operating portion is at an initial position. 
         [0012]    According to this structure, when the choke operating portion is not operated, the choke valve is half-opened (half choke), and when the user operates the choke operating portion, the opening degree of the choke valve is reduced and the choke valve becomes fully closed (full choke), for example. Thereby, the user is enabled to select the opening degree of the choke valve depending on situations, such as when the engine is cold or after a long period of storage. Further, since the choke valve is set to half open in the initial state of the choke operating portion, an opening degree suitable for the start up of the engine can be preset without requiring an operation by the user. 
         [0013]    Further, in the engine generator described above, preferably, the engine includes a recoil starter ( 80 ); and the recoil starter has a handle ( 80 B) provided on the outer surface ( 2 A) of the housing in a vicinity of the choke operating portion. 
         [0014]    According to this structure, the choke operating portion and the handle of the recoil starter, which need to be operated when starting the engine, are positioned close to each other, and thus, the operation is easy. 
         [0015]    Further, in the engine generator described above, preferably, the engine generator further comprises: a fuel tank ( 5 ); and a fuel cock ( 76 ) provided to a fuel pipe ( 75 ) connecting the fuel tank and the engine, wherein an operating portion ( 76 A) of the fuel cock is provided on the outer surface ( 2 A) of the housing in a vicinity of the choke operating portion. 
         [0016]    According to this structure, the choke operating portion and the cock operating portion, which need to be operated when starting the engine, are positioned close to each other, and thus, the operation is easy. 
         [0017]    According to the foregoing structure, it is possible, in an engine generator having a manually operable choke valve, to allow the opening degree of the choke valve to be varied in accordance with a variation of the load during choking. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]      FIG. 1  is a perspective view of an engine generator of an embodiment; 
           [0019]      FIG. 2  is a perspective view showing an essential part of the engine generator of the embodiment; 
           [0020]      FIG. 3  is a perspective view of a vaporizer of the embodiment; 
           [0021]      FIG. 4A  is a plan view of the vaporizer of the embodiment and  FIG. 4B  is a cross-sectional view showing an opening degree of the choke valve corresponding to  FIG. 4A ; 
           [0022]      FIG. 5  is a side view of the vaporizer of the embodiment; 
           [0023]      FIG. 6  is a cross-sectional view taken along line VI-VI in  FIG. 5 ; 
           [0024]      FIG. 7A  is a vertical cross-sectional view of a control shaft of the embodiment and  FIG. 7B  is a cross-sectional view taken along line B-B of  FIG. 7A ; 
           [0025]      FIG. 8A  is a plan view of the vaporizer of the embodiment, showing a state in which a choke operating portion is at an initial position and a negative pressure is supplied to an actuator and  FIG. 8B  is a cross-sectional view showing an opening degree of the choke valve corresponding to  FIG. 8A ; and 
           [0026]      FIG. 9A  is a plan view of the vaporizer of the embodiment, showing a state in which the choke operating portion is at an operating position and  FIG. 9B  is a cross-sectional view showing an opening degree of the choke valve corresponding to  FIG. 9A . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0027]    In the following, an embodiment of an engine generator  1  according to the present invention will be described with reference to the drawings. As shown in  FIG. 1 , the engine generator  1  of the present embodiment includes a substantially rectangular parallelepiped housing  2 , in which are provided an engine  3  (internal combustion engine), a generator  4  and a fuel tank  5 . The housing  2  is configured to have a larger dimension in a width direction than in a front-back direction. In  FIG. 1 , the front wall  2 A of the housing  2  faces the viewer of the drawing. Casters  6  are provided at appropriate positions of a lower part of the housing  2 . 
         [0028]    The engine  3  includes an engine main body  11  in which a cylinder, a combustion chamber and a crankcase are defined. A piston is reciprocally received in the cylinder, and a crankshaft is rotatably received in the crankcase. The piston and the crankshaft are connected with each other by a con rod. The engine  3  is disposed in the housing  2  such that the axis of the cylinder extends in the front-back direction of the housing  2  and the axis of the crankshaft extends in the width direction of the housing  2 . 
         [0029]    The generator  4  may consist of an electromagnet synchronous generator or a permanent magnet synchronous generator that is known in the art. The generator  4  is disposed next to the engine  3  in the width direction of the housing  2 , and the rotor shaft of the generator  4  is coaxially connected to the crankshaft. The fuel tank  5  is located at a position higher than the position of the engine  3 . 
         [0030]    As shown in  FIG. 2 , the engine  3  has an intake system  13  that is in communication with the combustion chamber. The intake system  13  includes an air inlet, an air cleaner  14  and a vaporizer  15  in this order from the upstream end. The intake system  13  is disposed on a side of the engine  3  away from the generator  4  in the width direction of the housing  2 . 
         [0031]    As shown in  FIGS. 3 to 5 , the vaporizer  15  includes a vaporizer main body  18  having an intake passage  17  defined therein. The intake passage  17  has a linearly extending axis and passes through the vaporizer main body  18 . As shown in  FIG. 6 , the intake passage  17  includes a venturi  19  at an intermediate part thereof in the longitudinal direction, whereby the cross-sectional area of the flow path is reduced. The venturi  19  is provided with a fuel nozzle  21 . The fuel nozzle  21  is in communication with a fuel chamber (not shown in the drawings) defined in a lower part of the vaporizer main body  18  and, according to a negative pressure on the intake passage  17  side, ejects fuel in the fuel chamber into the intake passage  17 . 
         [0032]    A choke valve  23  is provided on an upstream side of the venturi  19  of the intake passage  17 , while a throttle valve  24  is provided on a downstream side of the venturi  19 . The choke valve  23  and the throttle valve  24  each consist of a butterfly valve. A choke valve shaft  23 A, which is the valve shaft of the choke valve  23 , and the valve shaft of the throttle valve  24  are supported to be parallel to each other and rotatable relative to the vaporizer main body  18 . In the present embodiment, the vaporizer  15  is mounted to the engine  3  (housing  2 ) such that the intake passage  17  extends in a horizontal direction, while the choke valve shaft  23 A and the valve shaft of the throttle valve  24  extend in a vertical direction. 
         [0033]    The choke valve shaft  23 A is offset from the center of the intake passage  17 . The valve body  23 B of the choke valve  23  includes a first part  23 C and a second part  23 D separated by the choke valve shaft  23 A. Because the choke valve shaft  23 A is offset, the first part  23 C has a larger rotational radius and a larger area than those of the second part  23 D. 
         [0034]    The choke valve  23  is rotatable between a fully closed position and a fully open position. The rotatable range of the choke valve  23  is defined by stoppers not shown in the drawings. At the fully closed position, the valve body  23 B of the choke valve  23  inclines slightly relative to the cross section of the intake passage  17 , such that the first part  23 C is positioned downstream of the choke valve shaft  23 A while the second part  23 D is positioned upstream of the choke valve shaft  23 A. When the choke valve  23  rotates from the fully closed position such that the first part  23 C moves toward the downstream side and the valve body  23 B becomes in parallel to the axis of the intake passage  17 , the fully open position is reached. As the first part  23 C has a larger area than that of the second part  23 D, when an intake negative pressure acts on the downstream side of the choke valve  23 , the choke valve  23  receives a force urging it in the valve opening direction. 
         [0035]    As shown in  FIGS. 3 to 5 , an opening and closing mechanism  30  for opening and closing the choke valve  23  is provided on top of the vaporizer main body  18 . The opening and closing mechanism  30  includes a control shaft  31  provided to the choke valve shaft  23 A so as to be rotatable relative thereto, a restriction mechanism  32  that restricts the rotational position of the control shaft  31 , and a negative pressure mechanism  33 . As will be described in detail later, the restriction mechanism  32  includes a restriction mechanism lever  62  and a restriction member  67  as main structural elements thereof, while the negative pressure mechanism  33  includes a negative pressure mechanism lever  51  and an actuator  53  as main structural elements thereof. 
         [0036]    The choke valve shaft  23 A extends through the vaporizer main body  18  and projects out upward. The control shaft  31  is provided to an upper end of the choke valve shaft  23 A. As shown in  FIGS. 5 and 7 , the control shaft  31  is formed in a tubular shape and has an interior into which the upper end of the choke valve shaft  23 A is inserted. The choke valve shaft  23 A has a convex part  23 E that protrudes radially outward. On the other hand, the control shaft  31  includes a first stopper  31 A and a second stopper  31 B each protruding radially inward. The choke valve shaft  23 A and the control shaft  31  can rotate relative to each other between a position where the convex part  23 E abuts on the first stopper  31 A and a position where the convex part  23 E abuts on the second stopper  31 B. Namely, the choke valve shaft  23 A can rotate relative to the control shaft  31  within a predetermined range. For a given position of the control shaft  31 , the closer the convex part  23 E is positioned to the first stopper  31 A, the smaller the opening degree of the choke valve  23  becomes. 
         [0037]    In the interior of the control shaft  31 , a first urging member  35  is provided between the control shaft  31  and the choke valve shaft  23 A to urge the choke valve shaft  23 A relative to the control shaft  31  in a direction in which the convex part  23 E abuts on the first stopper  31 A. Namely, the first urging member  35  urges the choke valve shaft  23 A relative to the control shaft  31  in a closing direction of the choke valve  23 . The first urging member  35  may be a torsion coil spring, for example. 
         [0038]    The minimum opening degree of the choke valve  23  is determined by the control shaft  31  and the first urging member  35 . Specifically, a change in the rotational position of the control shaft  31  causes the position of the first stopper  31 A to change, which in turn changes the position at which the movement of the choke valve  23  in the closing direction is restricted. It is to be noted here that the minimum opening degree is a smallest opening degree that the choke valve  23  can have for a given rotational position of the control shaft  31 . Depending on the rotational position of the control shaft  31 , the minimum opening degree of the choke valve  23  varies from fully closed to fully open. It is to be noted that the choke valve  23  can reach the fully open position irrespective of the position of the control shaft  31  by being rotated against the urging force of the first urging member  35 . The position of the control shaft  31  at which the minimum opening degree is fully closed will be referred to as a first position (control shaft most closed position), while the position of the control shaft  31  at which the minimum opening degree is fully open will be referred to as a second position (control shaft most open position). 
         [0039]    Provided on an outer surface of the control shaft  31  is a control shaft arm  31 C which protrudes radially outward. A connection rod  37  is supported at a tip end portion of the control shaft arm  31 C. The connection rod  37  is formed in a crank shape, and includes a first end portion  37 A and a second end portion  37 B, which are formed to be in parallel to each other, and a middle portion  37 C extending in a direction normal to the first end portion  37 A and the second end portion  37 B. The tip end portion of the control shaft arm  31 C is provided with an engagement hole, which is a through-hole extending in parallel to the control shaft  31 . The first end portion  37 A of the connection rod  37  is inserted into the engagement hole of the control shaft arm  31 C, such that the first end portion  37 A and the second end portion  37 B are each in parallel to the control shaft  31 . The connection rod  37  is supported by the control shaft arm  31 C so as to be rotatable about the first end portion  37 A. 
         [0040]    As shown in  FIGS. 3 to 5 , the opening and closing mechanism  30  includes a framework member  40  joined to the vaporizer main body  18 . The framework member  40  is formed of a plurality of press formed steel plates joined to each other. The joining of the steel plates constituting the framework member  40  and the joining between the framework member  40  and the vaporizer main body  18  are realized by welding, bolting, etc. 
         [0041]    The framework member  40  includes a side wall portion  41  joined to the vaporizer main body  18 , and a first support portion  42  and a second support portion  43  which are joined to the side wall portion  41 . The first support portion  42  and the second support portion  43  are each formed in a plate-like shape, and are disposed to be normal to the choke valve shaft  23 A. The first support portion  42  is disposed above the vaporizer main body  18 , while the second support portion  43  is disposed above the first support portion  42 . 
         [0042]    The negative pressure mechanism lever  51  is rotatably supported on the underside of the first support portion  42 . The negative pressure mechanism lever  51  consists of a plate piece formed in an L-shape, has plate surfaces facing upward and downward, and is rotatable about an axis extending vertically. Namely, the negative pressure mechanism lever  51  is rotatable about an axis parallel to the choke valve shaft  23 A. 
         [0043]    A vertical wall  51 A extending upward is provided at one end of the negative pressure mechanism lever  51  so as to project therefrom, and an upper wall  51 B extending horizontally is provided at an upper end of the vertical wall  51 A. Each of the upper wall  51 B and an end of the negative pressure mechanism lever  51  opposing the upper wall  51 B in the vertical direction is provided with an insertion hole (not shown in the drawings) passing therethrough in the vertical direction, and the second end portion  37 B of the connection rod  37  is rotatably inserted in each insertion hole. The negative pressure mechanism lever  51  and the control shaft  31  which are connected with each other by the connection rod  37  rotate together. When the control shaft  31  is at the first position, the negative pressure mechanism lever  51  is at a third position (negative pressure mechanism lever most closed position), and when the control shaft  31  is at the second position, the negative pressure mechanism lever  51  is at a fourth position (negative pressure mechanism lever most open position). 
         [0044]    The other end of the negative pressure mechanism lever  51  is connected with the actuator  53  driven by a negative pressure. The actuator  53  is a diaphragm actuator and includes a case  53 A, a diaphragm (not shown in the drawings) disposed in the case  53 A and divides the interior into a first chamber and a second chamber, an urging member (not shown in the drawings) disposed between a face of the case  53 A on the side of the second chamber and a face of the diaphragm on the side of the second chamber to urge the diaphragm toward the first chamber, and a drive shaft  53 B having a base end connected with a face of the diaphragm on the side of the first chamber, and a tip end projecting out from the case  53 A on the side of the first chamber. The urging member may consist of a compression coil spring. The tip end of the drive shaft  53 B is connected with the other end of the negative pressure mechanism lever  51  so as to be rotatable about a vertically extending axis. The drive shaft  53 B moves back and forth in response to displacements of the diaphragm to cause the negative pressure mechanism lever  51  to rotate. 
         [0045]    The second chamber of the case  53 A is connected via a tube with a part of the intake system  13  downstream of a throttle valve or the crankcase of the internal combustion engine. The crankcase of the internal combustion engine is connected with the intake system  13  of the internal combustion engine via a blow-by passage. When the internal combustion engine is in operation, a negative pressure created in the intake system  13  and the crankcase is supplied to the second chamber. In response to the negative pressure supplied to the second chamber, the diaphragm is displaced toward the second chamber against the urging force of the urging member and the drive shaft  53 B is displaced in a direction in which the length of a part thereof projecting out from the case  53 A is reduced, so that the negative pressure mechanism lever  51  rotates. 
         [0046]    In an initial state in which no negative pressure is supplied, the drive shaft  53 B of the actuator  53  projects out (advanced) due to the urging force of the urging member, and in a drive state in which a negative pressure is supplied, the drive shaft  53 B is retracted (retreated) against the urging force of the urging member. Due to the actuator  53 , the negative pressure mechanism lever  51  is urged toward the third position in the initial state of the actuator  53 , and urged toward the fourth position in the drive state of the actuator  53 . 
         [0047]    Between the first support portion  42  and the negative pressure mechanism lever  51  is disposed an urging member (not shown in the drawings) that urges the negative pressure mechanism lever  51  relative to the first support portion  42  toward the fourth position. The urging member is provided for the purpose of removing a play between the negative pressure mechanism lever  51 , the connection rod  37  and the actuator  53 . 
         [0048]    A support shaft  61  projects upward from the upper surface of the second support portion  43 . The support shaft  61  supports, from the one closest to the second support portion  43 , the restriction mechanism lever  62 , a second urging member  63  and a pressing plate  64 , and has a tip end with which an adjustment nut (lock nut)  65  is threadably engaged. The restriction mechanism lever  62  is a plate piece formed in an L-shape, and has a through-hole at a middle portion thereof through which the support shaft  61  is passed such that the restriction mechanism lever  62  is rotatably supported by the support shaft  61 . The second urging member  63  consists of a disc spring having a through-hole at a central portion thereof through which the support shaft  61  is passed. 
         [0049]    The pressing plate  64  is a plate member that has a through-hole at a central portion thereof through which the support shaft  61  is passed and that further has a slit  64 A in an edge thereof. On the upper surface of the second support portion  43  is provided an engagement wall  43 A that projects upward. The engagement wall  43 A passes through the slit  64 A of the pressing plate  64  in the vertical direction, the pressing plate  64  can be displaced relative to the engagement wall  43 A in the vertical direction, namely, in the axial direction of the support shaft  61 . On the other hand, the engagement wall  43 A abuts on the edges of the slit  64 A to prevent the rotation of the pressing plate  64  around the support shaft  61 . 
         [0050]    The restriction mechanism lever  62  is disposed between the second urging member  63  and the upper surface of the second support portion  43 , and receives a pressure from the second urging member  63  and the second support portion  43  in the axial direction of the support shaft  61 . Therefore, when the restriction mechanism lever  62  rotates around the support shaft  61 , a frictional force generated between the restriction mechanism lever  62  and each of the second urging member  63  and the second support portion  43  acts as a rotational resistance against the restriction mechanism lever  62 . By adjusting an amount of tightening of the adjustment nut  65  (serving as an adjustment member) on the support shaft  61  and thereby changing an amount of preload applied by the second urging member  63  and the second support portion  43  on the restriction mechanism lever  62 , the rotational resistance acting on the restriction mechanism lever  62  can be set at any value. 
         [0051]    The restriction member  67  is provided at one end of the restriction mechanism lever  62 . In the present embodiment, the restriction member  67  is formed by bending a metallic rod. The restriction member  67  includes a first part  67 A extending downward from the one end of the restriction mechanism lever  62 , a second part  67 B extending laterally from a lower end of the first part  67 A, a third part  67 C extending from an end of the second part  67 B in a direction normal to the second part  67 B and the vertical direction, a fourth part  67 D extending from an end of the third part  67 C substantially in parallel to the second part  67 B so as to oppose the second part  67 B, and a fifth part  67 E extending upward from the fourth part  67 D. The second part  67 B, the third part  67 C and the fourth part  67 D form three side of a quadrangle as viewed from above. 
         [0052]    The one end of the restriction mechanism lever  62  is provided with a through-hole that extends vertically therethrough, and the first part  67 A of the restriction member  67  is disposed to pass through the through-hole. Thereby, the first part  67 A of the restriction member  67  is supported by the one end of the restriction mechanism lever  62  so as to be rotatable about an axis extending in the vertical direction. 
         [0053]    The second support portion  43  is provided with a first guide hole  68  which extends vertically therethrough and through which the first part  67 A is passed and a second guide hole  69  which extends vertically therethrough and through which the fifth part  67 E is passed. The first guide hole  68  extends in an arcuate shape with the support shaft  61  at its center. The second guide hole  69  has a straight shape and extends on a straight line obtained by extending a chord connecting the ends of the first guide hole  68  formed in an arcuate shape. When the restriction member  67  moves along with the rotation of the restriction mechanism lever  62 , the restriction member  67  undergoes a parallel shift while substantially maintaining its orientation. 
         [0054]    Because the first part  67 A is passed through the first guide hole  68  and the fifth part  67 E is passed through the second guide hole  69 , the second part  67 B, the third part  67 C and the fourth part  67 D are positioned below the second support portion  43 . A retaining ring is fixed on the fifth part  67 E such that the retaining ring can abut on an edge portion of the second guide hole  69 . The retaining ring determines a position of insertion (vertical position) of the fifth part  67 E relative to the second guide hole  69 . 
         [0055]    In a space surrounded by the second part  67 B, the third part  67 C and the fourth part  67 D of the restriction member  67  are placed the second end portion  37 B of the connection rod  37  and the vertical wall  51 A which are arranged on the side of the one end of the negative pressure mechanism lever  51 . 
         [0056]    The other end of the restriction mechanism lever  62  is connected with a choke operating portion  72  via a push-pull cable  71  serving as a connection member. The push-pull cable  71  includes a guide tube  71 A and a cable  71 B that is passed through the inside of the guide tube  71 A. The cable  71 B is supported by the guide tube  71 A so as to be moveable back and forth, and both ends thereof protrude from the guide tube  71 A. One end of the guide tube  71 A is connected with a tube support portion  43 B projecting upward from the second support portion  43 . The guide tube  71 A extends from the tube support portion  43 B in the forward direction of the housing  2 , and the other end thereof is connected with an operating portion  2 B provided on the front wall  2 A of the housing  2 . An end of the cable  71 B on the side of the tube support portion  43 B is connected with the restriction mechanism lever  62 , while an end of the cable  71 B on the side of the operating portion  2 B protrudes ahead of the operating portion  2 B and is connected with the choke operating portion  72 . Thereby, if the choke operating portion  72  is pulled forward or pushed backward, the restriction mechanism lever  62  connected with the choke operating portion  72  via the cable  71 B rotates around the support shaft  61 . The choke operating portion  72  can be displaced between an initial position at which it is positioned most backward (a position at which it has been pushed fully backward (toward the front wall)) and an operating position at which it is positioned most forward (a position at which it has been pulled fully forward from the front wall  2 A). 
         [0057]    The restriction mechanism lever  62  connected with the choke operating portion  72  via the push-pull cable  71  is at a fifth position (restriction mechanism lever most open position) when the choke operating portion  72  is at the initial position, and is at a sixth position (restriction mechanism lever most closed position) when the choke operating portion  72  is in an operating state. As shown in  FIG. 4A , when the restriction mechanism lever  62  is at the fifth position, the second part  67 B of the restriction member  67  abuts on the second end portion  37 B of the connection rod  37  and presses the same. Thereby, the control shaft  31  is positioned at the middle position between the first position and the second position, and the negative pressure mechanism lever  51  is positioned at the middle position between the third position and the fourth position. When the control shaft  31  is at the middle position, as shown in  FIG. 4B , the minimum opening degree of the choke valve  23  is half open (half choke) between fully open and fully closed. In this state, the choke valve  23  is brought to a half open position due to the urging force of the first urging member  35  when the negative pressure downstream thereof is small, and can move to the fully open position against the urging force of the first urging member  35  when the negative pressure downstream thereof is large. 
         [0058]    The frictional force in the rotational direction acting on the restriction mechanism lever  62  (rotational resistance) is adjusted such that it is always larger than the force with which the negative pressure mechanism lever  51  pushes the restriction member  67  irrespective of the operation of the actuator  53 . Namely, a configuration is made such that the negative pressure mechanism lever  51  is prevented from displacing the restriction member  67  and the restriction mechanism lever  62 . Therefore, when the restriction mechanism lever  62  is at the fifth position, the rotational positions of the restriction mechanism lever  62 , the negative pressure mechanism lever  51  and the control shaft  31  are maintained. As described above, the frictional force (rotational resistance) in the rotational direction acting on the restriction mechanism lever  62  is set by adjusting an amount of tightening (preload) of the adjustment nut  65 . 
         [0059]    When the restriction mechanism lever  62  is positioned at the fifth position, the third part  67 C and the fourth part  67 D of the restriction member  67  are not on the line of movement of the second end portion  37 B of the connection rod  37  and the vertical wall  51 A when the negative pressure mechanism lever  51  rotates toward the fourth position. Therefore, the restriction member  67  does not restrict the rotation of the negative pressure mechanism lever  51  toward the fourth position. Accordingly, if a negative pressure is supplied to the actuator  53  when the restriction mechanism lever  62  is at the fifth position, as shown in  FIG. 8A , the negative pressure mechanism lever  51  moves to the fourth position and the control shaft  31  moves to the second position. As shown in  FIG. 8B , when the control shaft  31  is at the second position, the minimum opening degree of the choke valve  23  becomes fully open, and the choke valve  23  is kept fully open. 
         [0060]    In the state shown in  FIG. 4A , if the restriction mechanism lever  62  is moved from the fifth position toward the sixth position, the second part  67 B of the restriction member  67  moves in a direction away from the second end portion  37 B of the connection rod  37  in the direction of rotation of the negative pressure mechanism lever  51 . At this time, in response to the movement of the second part  67 B, the negative pressure mechanism lever  51  moves from the middle position toward the third position due to the urging force of the actuator  53 . Even after the negative pressure mechanism lever  51  has reached the third position, the restriction mechanism lever  62  continues to rotate toward the sixth position, and the second part  67 B of the restriction member  67  leaves away from the second end portion  37 B of the connection rod  37 . As shown in  FIG. 9A , when the restriction mechanism lever  62  is at the sixth position, the fourth part  67 D of the restriction member  67  is located at a position where it abuts on the vertical wall  51 A of the negative pressure mechanism lever  51  at the third position or at a position close to the vertical wall  51 A. At this time, as shown in  FIG. 9B , the minimum opening degree of the choke valve  23  becomes fully closed (namely, the control shaft  31  is moved to the first position). In this state, the choke valve  23  is brought to the fully closed position by the urging force of the first urging member  35  when the negative pressure downstream thereof is small, and can move to the fully open position against the urging force of the first urging member  35  when the negative pressure downstream thereof is large. 
         [0061]    If a negative pressure is supplied to the actuator  53  when the restriction mechanism lever  62  is at the sixth position, the frictional force in the rotational direction (rotational resistance) acting on the restriction mechanism lever  62  is larger than the drive force of the actuator  53  transmitted to the restriction member  67  via the negative pressure mechanism lever  51 , and therefore, the negative pressure mechanism lever  51  is restrained by the fourth part  67 D and is retained at the third position as shown in  FIG. 9 . 
         [0062]    The fuel tank  5  and the vaporizer  15  are connected with a fuel pipe  75 , and fuel is supplied from the fuel tank  5  to the vaporizer  15  due to the gravity. The fuel pipe  75  extends forward from the fuel tank  5 , passes the inner side of the operating portion  2 B mounted on the front wall  2 A of the housing  2 , and extends rearward to be connected with the vaporizer  15 . At a part of the fuel pipe  75  positioned on the inner side of the operating portion  2 B is provided a fuel cock  76  for switching the state of communication of the fuel pipe  75 . The fuel cock  76  includes a cock operating portion  76 A to be held and operated by a user. The cock operating portion  76 A extends through the operating portion  2 B, and is placed on the front face side of the operating portion  2 B. 
         [0063]    A part of the engine main body  11  of the engine  3  on the side away the generator  4  is provided with a recoil starter  80 . The recoil starter  80  may be any known recoil starter, and includes a pulley connected with the crankshaft, a cable  80 A wound around the pulley, and a handle  80 B provided at a tip end of the cable  80 A. The tip end of the cable  80 A is drawn out forward from the engine main body  11 , and the handle  80 B is supported on the front face of the operating portion  2 B. By holding the handle  80 B supported by the operating portion  2 B and pulling out the cable  80 A forward, the user can impart a rotational force to the crankshaft and thereby start the engine  3 . 
         [0064]    In the following, a description will be made of ways of starting the above-described engine generator  1  and an operation of the engine generator  1  therein. In an initial state before the engine is started, the fuel cock  76  is closed, the choke operating portion  72  is at the initial position, and no negative pressure is supplied to the actuator  53 . In this state, as shown in  FIG. 4 , the restriction mechanism lever  62  is at the fifth position, the negative pressure mechanism lever  51  is at the middle position, the control shaft  31  is at the middle position, and the choke valve  23  is half open. 
         [0065]    As the way of starting the engine  3 , there are a first way of starting, in which the engine  3  is started from a state where the minimum opening degree of the choke valve  23  is set to fully closed by operating the choke operating portion  72 , and a second way of starting, in which the engine  3  is started from a state where the minimum opening degree of the choke valve  23  is set to half open (half choke) without the choke operating portion  72  being operated. 
         [0066]    In the first way of starting, as a preparation for starting the engine  3 , the user opens the fuel cock  76  to start fuel supply to the vaporizer  15 . Further, the user pulls out the choke operating portion  72  forward to the operating position. Thereby, as shown in  FIG. 9A , the restriction mechanism lever  62  is moved to the sixth position, the negative pressure mechanism lever  51  is moved to the third position, and the control shaft  31  is moved to the first position, and, as shown in  FIG. 9B , the choke valve  23  is fully closed. 
         [0067]    Thereafter, when the user pulls the handle  80 B forward, the recoil starter  80  causes the crankshaft to rotate to start the engine  3 . The activation of the engine  3  generates a negative pressure in the intake system  13  and the crankcase, and the negative pressure is supplied to the actuator  53 . However, because the frictional force applied to the restriction mechanism lever  62  is greater than the drive force of the actuator  53 , the negative pressure mechanism lever  51 , the restriction mechanism lever  62  and the control shaft  31  are prevented from being displaced. In this state, depending on the negative pressure generated downstream of the choke valve  23 , the choke valve  23  may rotate in the opening direction against the urging force of the first urging member  35 . Thus, the choke valve  23  may be opened and closed depending on the load of the engine  3 , making it possible to suppress occurrence of engine stall or deterioration of fuel efficiency. 
         [0068]    When the user pushes the choke operating portion  72  rearward to return it back to the initial position, the restriction mechanism lever  62  is moved to the fifth position, the negative pressure mechanism lever  51  driven by the actuator  53  is moved to the fourth position, and the control shaft  31  is moved to the second position as shown in  FIG. 8A . Thereby, as shown in  FIG. 8B , the choke valve  23  is fully opened. In this state, the choke valve  23  is kept fully open irrespective of the negative pressure downstream thereof, and thus, the pumping loss is reduced. 
         [0069]    Thereafter, when the engine  3  is stopped and the negative pressure vanishes, the negative pressure mechanism lever  51  is caused to rotate due to the urging force of the actuator  53  until the second end portion  37 B of the connection rod  37  abuts on the second part  67 B of the restriction member  67  so that the negative pressure mechanism lever  51  is brought to the middle position, and accordingly, the control shaft  31  is brought to the middle position, as shown in  FIG. 4A . As a result, as shown in  FIG. 4B , the choke valve  23  returns to the initial, half open position. 
         [0070]    In the second way of starting, in the initial state before engine start up, the user opens the fuel cock  76  and pulls the handle  80 B to start the engine  3 . At this time, the choke operating portion  72  is not operated and the choke valve  23  is kept half open. Once the engine  3  is started, depending on the negative pressure generated downstream of the choke valve  23 , the choke valve  23  rotates in the opening direction against the urging force of the first urging member  35 . Therefore, the choke valve  23  may be opened and closed depending on the load of the engine  3 , making it possible to suppress occurrence of engine stall or deterioration of fuel efficiency. Further, once a negative pressure is supplied to the actuator  53 , the negative pressure mechanism lever  51  is moved to the fourth position and the control shaft  31  is moved to the second position, as shown in  FIG. 8A . As described above, the engine generator  1  of the present embodiment can be started in the half choke state without operating the choke operating portion  72 . 
         [0071]    In the engine generator  1  of the present embodiment, by adjusting an amount of tightening of the adjustment nut  65 , it is possible to vary the amount of frictional force generated at the restriction mechanism lever  62 . Therefore, the opening and closing mechanism  30  can be applied to a variety of engines having different displacements. 
         [0072]    In the engine generator  1  of the present embodiment, the choke operating portion  72 , the cock operating portion  76 A, and the handle  80 B of the recoil starter  80 , which are to be operated when starting the engine, are gathered together in the operating portion  2 B, and therefore, good operability is achieved. 
         [0073]    A description of the concreate embodiments has been provided in the foregoing, but the present invention is not limited to the above embodiments and various alterations and modifications are possible. For example, the shape and arrangement of each component of the opening and closing mechanism  30  may be changed as appropriate.