Patent Publication Number: US-6220220-B1

Title: Fuel supplying device for engine

Description:
BACKGROUND OF THE INVENTION 
     1. Technical Field of the Invention 
     The present invention relates to a fuel supplying device for an engine. 
     2. Description of Earlier Technology 
     There is known a conventional technique as the fuel supplying device for an engine, which is provided with an electronic governor and a mechanical governor and conducts an electronic control by the electronic governor and a mechanical control by the mechanical governor. The conventional technique is used by switching it over to an electro-solo control mode or to a mecha-solo control mode. 
     The conventional technique makes a control of speed and a limitation of a maximum fuel injection amount by the electronic control alone in the electro-solo control mode and does them by the mechanical control alone in the mecha-solo control mode. 
     The above-mentioned conventional technique has the following problems. 
     The electro-solo control mode has to limit the maximum fuel injection amount of the electronic control by the electronic governor. Therefore, it is necessary to employ an electronic governor having such a limitation function, which results in increasing the cost of the electronic governor. Further, the electronic governor must be adjusted so that it can make such limitation and therefore such an adjustment takes much labor. 
     SUMMARY OF THE INVENTION 
     The present invention has an object to provide a fuel supplying device for an engine, which can solve the foregoing problems. 
     An invention as defined in claim  1  is constructed as follows. 
     A fuel supplying device for an engine is provided with an electronic governor  1  and a mechanical governor  2 . The mechanical governor  2  is arranged to limit a maximum fuel injection amount of an electronic control by the electronic governor  1 . 
     An invention of claim  2  is constructed as follows. 
     A maximum fuel injection position  4  of a fuel metering portion  3  in the electronic control comes to a halfway position of a speed control area  5  of the fuel metering portion  3 . This fuel supplying device automatically switches over the electronic control by the electronic governor  1  to a mechanical control by the mechanical governor  2  and vice versa at the maximum fuel injection position  4 . It performs the electronic control in a fuel decrease side area  5   a  of the speed control area  5  with respect to the maximum fuel injection position  4  and does the mechanical control in a fuel increase side area  5   b  with respect to the maximum fuel injection position  4 . 
     In the present invention, the electronic control means a speed control conducted based on an electronic speed control line  60  designating an electronic control property. A mechanical control means a speed control conducted based on a mechanical speed control line  51  indicating a mechanical control property. The speed control area  5  means an area of a metering area of the fuel metering portion  3 , in which fuel metering is effected based on at least one of the electronic speed control line  60  and the mechanical speed control line  51 . In the case where the maximum fuel injection position  4  of the fuel metering portion  3  of the electronic control comes to a halfway of the speed control area  5 , the maximum fuel injection position  4 , as a matter of course, is a position where the electronic control switches over to the mechanical control and vice versa. 
     The invention of claim  1  produces the following function and effect. 
     The mechanical governor  2  limits the maximum fuel injection amount of the electronic control. This can remove the limitation function from the electronic governor  1  and eventually reduce the cost of the electronic governor  1 . Besides, it is possible to omit or simplify the adjustment of the electronic governor that considers such limitation function and to thereby reduce the labor for its adjustment. 
     The mechanical governor  2  limits the maximum fuel injection amount of the electronic control. Therefore, in the event that the electronic governor  1  is added to an existing engine with a mechanical governor, which is satisfactory in exhaust gas property, the engine can succeed the satisfactory metering property of the mechanical governor as it is as regards the maximum fuel injection amount of the electronic control. Accordingly, even if the electronic governor  1  is added later to an engine with a mechanical governor, which has cleared the exhaust gas restriction, the engine does not change its exhaust gas property. 
     Inventions as set forth in claim  2  and subsequent claims produce the following effects and functions in addition to those of the invention as defined in claim  1 . 
     According to the invention of claim  2 , in a low load area the electronic control decreases an engine rotation speed to reduce the noise of engine and in a high load area the mechanical control can operate the engine with the same feeling as in the case of operating an existing engine with only the mechanical governor. 
     The invention of claim  3  can select either a composite control mode or an electro-solo control mode whichever is properly adapted to the operation condition and the operation feeling. 
     The invention of claim  4  can select either the composite control mode or a mecha-solo control mode whichever is properly adapted to the operation condition and the operation feeling. When switching it over to the mecha-solo control mode, it is possible to operate the engine with the same feeling as in the case of operating an existing engine with only the mechanical governor. Further, even if the electronic governor  1  is in disorder, the mechanical governor  2  can operate the engine without causing any problem. 
     According to the invention of claim  5 , the mechanical governor does not function as a disturbance element in the area  5   a  where the electronic control is performed and the electronic governor  1  does not function as a disturbance element, either in the area  5   b  where the mechanical control is conducted. This produces the following advantage. 
     It is possible to perform the electronic control and the mechanical control precisely and besides employ low output ones for the electronic governor  1  and the mechanical governor  2 , respectively. 
     The invention of claim  6  performs the fuel metering by the electronic governor  1  in an engine starting area  7  and therefore can make a delicate control in correspondence to the starting condition. 
     According to the invention of claim  7 , when the engine starts at a warm time or restarts while it is still warm just after it has stopped, in correspondence to these starting conditions, fuel supply is reduced to result in the possibility of inhibiting the fuel consumption and the discharge of unburnt poisonous gas. 
     According to the invention of claim  8 , the electronic governor  1  can also serve as an engine stopping device. This dispenses with a circuit and an actuator dedicated for the engine stopping device, which can reduce the cost of engine and make it compact. 
     According to the invention of claim  9 , when operation failure of the electronic governor  1  has cancelled energizing an actuator  17 , an urging force of a spring  33  forces an electronic output portion  9  to move the fuel metering portion  3  up to a fuel supply stop position  8  and stays it there. Thus restarting the engine is tried in vain, which can confirm the operation failure of the electronic governor  1 . 
     According to the invention of claim  10 , while the engine is in operation, at loads (L 4 ) to (L 1 ) below a reference load (L 5 ) the electronic governor  1  settles an engine rotation speed lower than the mechanical governor  2  does. This can decrease the noise of engine at partial loads (L 4 ) to (L 2 ) and no load (L 1 ). 
     Further, the invention of claim  10  can set a steady state rotation speed (NX) of the electronic control at loads (L 4 ) to (L 1 ) below the reference load (L 5 ) to a value identical or close to that of a steady state rotation speed (NX) of the electronic control at the reference load (L 5 ). Accordingly, it is possible to keep the working efficiency at the rated load (L 5 ) high while inhibiting the noise of engine at the partial loads (L 4 ) to (L 2 ) and the no load (L 1 ). 
     The inventions of claim  11  and subsequent claims produce the following effects and functions in addition to those of the invention as defined in claim  10 . 
     The invention of claim  11  can be usefully employed for an engine generator or the like usage that requires to maintain the engine rotation speed constant. 
     The invention of claim  12  can change a composite control property obtained by combining an electronic control property with a mechanical control property, through a single operation with ease. 
     The invention of claim  13  can set composite control properties different in reference load and select a proper one in accordance with the usage of engine. 
     The invention of claim  14  can freely set composite control properties different in reference load and adapt them to a wide range of use of engine. 
     The invention of claim  15  limits an engine rotation speed (N) to not higher than a rated rotation speed (NT) and therefore can reduce the noise of engine. 
     The invention of claim  16  can increase the engine rotation speed (N) to a working start speed (ST) soon by the mechanical governor  2  even if the electronic governor  1  slow in steady state speed is employed. 
     The invention of claim  17  produces the following advantage. 
     In the case where the steady state speed of the electronic governor  1  is slow, the electronic control is unlikely to increase fuel promptly even if the engine rotation speed (N) is reduced due to the increase of load. However, in the event the engine rotation speed (N) goes down to less than a lower limit value (ZL) of a controlled speed zone (Z), the mechanical governor  2  increases the fuel promptly. Therefore, the engine stop hardly occurs even if the electronic governor  1  slow in steady state speed is utilized. 
     According to the invention of claim  18 , if excessive rotation increase occurs, urgent fuel decrease working moves the fuel metering portion  3  to a fuel decrease side immediately, thereby being able to decrease fuel supply. Thus it is possible to quickly solve the excessive rotation increase. 
     The invention of claim  19  produces the following advantage. 
     A position detecting means costs so high that nonuse of this means can reduce the cost of the electronic governor  1 . 
     Further, according to the invention of claim  19 , in the case where the utilized electronic governor  1  does not include a metering position detecting means of the fuel metering portion  3 , it is impossible to take a metering position of the fuel metering portion  3  for a control target. Consequently, when compared with an electronic governor that includes the metering position detecting means, the steady state speed of the electronic governor  1  is reduced. However, if the inventions of claim  16  and  17  are added, the engine can improve the disadvantage caused by the reduced steady state speed since it can promptly increase the engine rotation speed (N) and inhibit the engine stop as mentioned above. 
     According to the invention of claim  20 , the electronic governor  1  conducts a control working through PID or PI control and does its arithmetic processing without totalizing the data obtained before it starts working. Thus it is possible to prohibit the delay of the electronic control caused through the data accumulation. 
     According to the invention of claim  21 , in the case where a speed setting means  18  carries out a quick acceleration, even if the electronic governor  1  excessively responds to the quick acceleration, thereby advancing the output portion  9  of the electronic governor  1  too much in a direction for fuel increase and causing the fuel metering portion  3  to try to overshoot in the direction for fuel increase, the output portion  10  of the mechanical governor  2  can receive the fuel metering portion  3 . This results in the possibility of inhibiting the fuel increase caused by the excessive response of the electronic governor  1 . 
     The invention of claim  22  can approach an engine torque to a maximum one even in a low rotation area. This can enhance the function of inhibiting the engine stop. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a flow chart outlining the processing of a controller in a first embodiment; 
     FIG. 2 schematically shows an electronic governor and a mechanical governor of the first embodiment; 
     FIG. 3 graphically shows control properties of the first embodiment set at a high speed and in a mode (M 1 ); 
     FIG. 4 graphically shows control properties of the first embodiment set at a high speed and in a mode (M 2 ); 
     FIG. 5 graphically shows control properties of the first embodiment set at a low speed and in a mode (M 1 ); 
     FIG. 6 graphically shows control properties of the first embodiment set at a low speed and in a mode (M 2 ); 
     FIG. 7 graphically shows control properties of the first embodiment when limiting speed; 
     FIG. 8 graphically shows a control property at the time of a mecha-solo control of the first embodiment; 
     FIG. 9 is a front half portion of a flow chart showing in detail the processing of a controller of the first embodiment; 
     FIG. 10 is a rear half portion of the flow chart showing in detail the processing of the controller of the first embodiment; 
     FIG. 11 graphically shows control properties of a first modification of the first embodiment set at a high speed and in the mode (M 1 ); 
     FIG. 12 graphically shows control properties of a second modification of the first embodiment set at a low speed and in the mode (M 1 ); 
     FIG. 13 is a schematic view illustrating an electronic governor and a mechanical governor of a second embodiment; 
     FIG. 14 graphically shows control properties at the time of a mecha-solo control of the second embodiment; 
     FIG. 15 graphically shows control properties at the time of a droop control of the second embodiment; 
     FIG. 16 schematically shows an electronic governor and a mechanical governor of a third embodiment; and 
     FIG. 17 schematically shows an electronic governor and a mechanical governor of a fourth embodiment. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Embodiments of the present invention are explained with reference to the drawings. FIGS. 1 to  12  explain a fuel supplying device for a diesel engine according to a first embodiment of the present invention. 
     The fuel supplying device will be outlined as follows. 
     As shown in FIG. 2, this fuel supplying device comprises an electronic governor  1  and a mechanical governor  2 . It conducts an electronic control by the electronic governor  1  and does a mechanical control by the mechanical governor  2 . And the mechanical governor  2  limits a maximum fuel injection amount of the electronic control by the electronic governor  1 . The electronic governor  1  includes an electronic output portion  9  and the mechanical governor  2  includes a mechanical output portion  10 , respectively. The fuel metering portion  3  comprises an electronic input portion  11  and a mechanical input portion  12 . 
     The electronic output portion  9  faces the electronic input portion  11  from a fuel increase side and the mechanical output portion  10  opposes the mechanical input portion  12  from the fuel increase side. An urging means  13  urges the fuel metering portion  3  toward the fuel increase side. In an area  5   a  where the electronic control is performed, the electronic input portion  11  is brought into contact with the electronic output portion  9 , thereby connecting the former to the latter and retaining the mechanical input portion  12  separated from the mechanical output portion  10 . In an area  5   b  where the mechanical control is performed, the mechanical input portion  12  is brought into contact with the mechanical output portion  10 , thereby connecting the former to the latter and retaining the electronic input portion  11  separated from the electronic output portion  9 . 
     The fuel metering portion  3  is a fuel metering rack of a fuel injection pump. The electronic input portion  11  is an end surface on the fuel increase side of the fuel metering rack, and the mechanical input portion  12  is a rack pin. The fuel metering portion  3  is urged in a direction for fuel increase with a force  13   a  of the urging spring  13 . 
     The mechanical governor  2  is constructed as follows. 
     As shown in FIG. 2, the mechanical governor  2  comprises a governor lever  21 , a governor spring  19 , a governor weight  20  and a fuel limiter  25 . The governor lever  21  comprises a first lever  21   a  and a second lever  21   b . The first lever  21   a  is interlockingly connected to a speed setting means  18  through the governor spring  19 , an interlocking lever  23  and a connecting rod  22 . The speed setting means  18  sets a speed to adjust a force  19   a  of the governor spring  19 . The second lever  21   b  comprises the output portion  10  and a torque-up device  26 . The output portion  10  receives the mechanical input portion  12  of the fuel metering portion  3  urged with the urging spring force  13   a.    
     The torque-up device  26  comprises a torque case  26   a , a torque pin  26   b  and a torque spring  26   c . The torque case  26   a  is attached to the second lever  21   b  so as to be able to advance and retreat. The torque pin  26   b  is urged with a force  26   d  of the torque spring  26   c  in a direction for pushing it out of the torque case  26   a  and has a leading end which opposes the first lever  21   a . The governor weight  20  faces the second lever  21   b  and produces a governing force  20   a  in response to an engine rotation speed (N). The fuel limiter  25  is attached to a gear case wall so as to be able to advance and retreat and has a leading end which opposes the second lever  21   b . The fuel limiter  25  can adjust an output at a rated load by advancing and retreating and the torque case  26   a  can also adjust an upper limit of the fuel increase at an over-rated load by advancing and retreating. 
     The mechanical governor  2  works as follows. 
     While the engine is in operation, the first lever  21   a  and the second lever  21   b  integrally swing due to unbalance between the governor spring force  19   a  and the governing force  20   a  and the urging spring force  13   a  until the first lever  21   a  is received by the leading end of the fuel limiter  25 . As the load increases, the engine rotation speed decreases. When the first lever  21   a  is received by the leading end of the fuel limiter  25 , only the second lever  21   b  swings due to unbalance between the torque spring force  26   d  and the governing force  20   a  and the urging spring force  13   a . When the engine starts, the governing force  20   a  is small until the engine rotation speed (N) reaches a rotation speed (n 8 ) at the end of starting fuel increase shown in FIG.  3 . Therefore, the urging spring force  13   a  holds the fuel metering portion  3  in a starting fuel increase area  7  to make the starting fuel increase possible. In this case, the second lever  21   b  is pushed by the fuel metering portion  3  to largely incline so as not to interfere with the starting fuel increase. In FIG. 3, numeral (n 7 ) indicates an idling rotation speed to ascertain the start. 
     The electronic governor  1  is constructed as follows. 
     As shown in FIG. 2, the electronic governor  1  comprises a controller  16 , an actuator  17 , a set speed detecting means  18   c , a rotation speed detecting means  15  and a reference load changing means (M). The actuator  17  is a linear solenoid, and it comprises an output rod  34 , a spring  33  and a magnetic coil  35 . The output rod  34  has at its leading end the output portion  9 , which receives the electronic input portion  11  of the fuel metering portion  3 . The spring  33  urges the output rod  34  in a direction for pushing it out. The magnetic coil  35  pulls the output rod  34  in a direction for withdrawing it. 
     The set speed detecting means  18   c  is a potentiometer which detects a speed setting position of the speed setting means  18  and send to the controller  16  a speed setting voltage corresponding to the speed setting position as a speed setting signal. The speed setting means  18  is of single type that serves to set the speeds of both the electronic governor  1  and the mechanical governor  2 . The speed setting of the speed setting means  18  of this single type can set an electronic control property and a mechanical control property in series. Further, the set speed detecting means  18   c  can detect the set speeds of both the electronic governor  1  and the mechanical governor  2 . The rotation speed detecting means  15  detects the engine rotation speed (N) and sends a detected speed signal to the controller  16 . The reference load changing means (M) comprises a switch-over lever which selects the alternative of a mode (M 1 ) and a mode (M 2 ) to change a reference load to be mentioned later. Although the electronic governor  1  does not include a metering position detecting means that directly detects a metering position of the fuel metering portion  3 , it may be provided with such means. 
     The controller  16  conducts the following processing. 
     It sets an electronic control property based on the detected set speed signal sent from the set speed detecting means  18   c  and the mode set by the reference load changing means (M). Then it calculates a deviation between the engine rotation speed (N) and a steady state rotation speed (NX) of the electronic control determined on the base of the set electronic control property and sets a duty ratio of PWM wave based on the calculated deviation value. Thereafter, it sends the PWM wave to a switching element of an energizing circuit which energizes the magnetic coil  35  of the actuator  17  so as to adjust output of the actuator  17  and approaches the engine rotation speed (N) to the steady state rotation speed (NX) of the electronic control. 
     Explanation is given below regarding the manner and behavior in which the electronic control property and the mechanical control property are set. 
     If the speed setting means  18  shown in FIG. 2 sets a high speed and the reference load changing means (M) selects the mode (M 1 ), it will provide such a control property as schematically depicted in FIG.  3 . This schematic view illustrates the respective steady state rotation speeds and the like of the mechanical control and the electronic control with respective loads imposed. In FIG. 3 a full line schematically shows a mechanical control property line  50 . The mechanical control property line  50  has one inclined line which is close to a vertical line and designates a speed control line  51  and the other inclined line which is close to a horizontal line and indicates a torque-up line  52 . The horizontal line shows a full load line  53 . A one-dot chain line shows an electronic speed control line  60 . From rated load (L 5 ) to no load (L 1 ), the mechanical control property comes to a droop control property in which as the load decreases, the respective steady state rotation speeds (n 5 ) to (n 1 ) gradually increase. In an over-rated load area, it comes to a torque-up property in which as the load increases, a steady state rotation speed (n 6 ) becomes lower than the steady state rotation speed (n 5 ) at the rated load (L 5 ). The electronic control property comes to an isochronous control property in which the respective steady state rotation speeds (NXs) take the same value from over-rated load (L 6 ) to no load (L 1 ). Please note the electronic speed control line  60  may be set so that it comes to the droop control property as well as the mechanical speed control line. 
     The relationship between the electronic control property and the mechanical control property is as follows. 
     Defined as the reference load is a load at a point where the mechanical control property line  50  crosses the electronic speed control line  60 . In the case where the reference load changing means (M) selects the mode (M 1 ), as shown in FIG. 3, the rated load (L 5 ) comes to the reference load. The steady state rotation speed (NX) of the electronic control at the rated load (L 5 ) of the reference load is coincident with the steady state rotation speed (n 5 ) of the mechanical control at the same load (L 5 ). The steady state rotation speed (NX) of the electronic control at the loads (L 4 ) to (L 1 ) below the rated load (L 5 ) is lower than the steady state rotation speeds (n 4 ) to (n 1 ) of the mechanical control at the same loads (L 4 ) to (L 1 ). The torque-up steady sate rotation speed (n 6 ) at the over-rated load (L 6 ) becomes lower than the steady state rotation speed (NX) of the electronic control at the same load (L 6 ). 
     The engine rotation speed (N) is settled in the following behavior. 
     While the engine is in operation, at the rated load (L 5 ) of the reference load, the electronic governor  1  and the mechanical governor  2  settle the engine rotation speed (N) on the steady state rotation speed (NX) of the electronic control and the steady state rotation speed (n 5 ) of the mechanical control, respectively. The steady state rotation speed (NX) has the same value as that of the steady state rotation speed (n 5 ). At the loads (L 4 ) to (L 1 ) below the rated load (L 5 ), the electronic governor  1  settles the engine rotation speed (N) on the steady state rotation speed (NX) of the electronic control. At the over-rated load (L 6 ), the mechanical governor  2  reduces the engine rotation speed (N) to the torque-up steady state rotation speed (n 6 ) close to a maximum torque rotation speed (NM). 
     How to settle the engine rotation speed (N) is as follows. 
     While the engine is in operation, at the rated load (L 5 ) of the reference load, based on the electronic speed control line  60  and the mechanical speed control line  51 , a settling position of the fuel metering portion  3  by the electronic control is coincident with a settling position of the fuel metering portion  3  by the mechanical control, which composes a maximum fuel injection position  4  of the fuel metering portion  3  in the electronic control. In this case, the output portion  9  of the electronic governor  1  receives the electronic input portion  11  of the fuel metering portion  3  and the output portion  10  of the mechanical governor  2  receives the mechanical input portion  12  of the fuel metering portion  3 , respectively. Both of the electronic governor  1  and the mechanical governor  2  set the fuel metering portion  3  to the maximum fuel injection position  4  and settle the engine rotation speed (N) on the steady state rotation speed (NX) of the electronic control and the steady state rotation speed (n 5 ) of the mechanical control, respectively. 
     At the loads (L 4 ) to (L 1 ) below the rated load (L 5 ) of the reference load, the device takes an electro-solo control mode where only the electronic control is performed over the whole area  5   a  of a speed control area  5  based on the electronic speed control line  60 . The output portion  9  of the electronic governor  1  receives the electronic input portion  11  of the fuel metering portion  3  and the output portion  10  of the mechanical governor  2  separates from the mechanical input portion  12  of the fuel metering portion  3  toward the fuel increase side. And the electronic governor  1  settles the fuel metering portion  3  in the fuel decrease side area  5   a  with respect to the maximum fuel injection position  4  and settles the engine rotation speed (N) on the steady state rotation speed (NX) of the electronic control. 
     At the over-rated load (L 6 ) above the reference load (L 5 ), based on the torque-up line  52  the output portion  10  of the mechanical governor  2  receives the mechanical input portion  12  of the fuel metering portion  3  in a torque-up area  6  and the output portion  9  of the electronic governor  1  separates from the electronic input portion  11  of the fuel metering portion  3  toward the fuel increase side. And the mechanical governor  2  settles the fuel metering portion  3  in the torque-up area  6  of the fuel increase side with respect to the maximum fuel injection position  4  and reduces the engine rotation speed (N) to the torque-up steady state rotation speed (n 6 ). 
     Load fluctuation entails the following transition property. 
     When the load decreases from the rated load (L 5 ) of the reference load to the loads (L 4 ) to (L 1 ), the output portion  10  of the mechanical governor  2  separates from the mechanical input portion  12  of the fuel metering portion  3  toward the fuel increase side and the electronic control is performed prior to the mechanical control. Conversely, when the load increases from the rated load (L 5 ) to the over-rated load (L 6 ), the output portion  9  of the actuator  17  separates from the electronic input portion  11  of the fuel metering portion  3  toward the fuel increase side, and the mechanical control is performed prior to the electronic control. The working of the mechanical governor  2  is not inputted as a disturbance element at the time of the electronic control and the working of the electronic governor  1  is not inputted as a disturbance element at the torque-up time, either. This improves the electronic control and the torque-up in accuracy. Additionally, the electronic governor  1  can use an actuator  17  small in size and output. 
     However, in the case where while the electronic control is performed, the output portion  9  of the electronic governor  1  advances too much toward the fuel increase side or the output portion  10  of the mechanical governor  2  does not move to the fuel increase side promptly due to the difference of the steady state speed between the electronic control and the mechanical control or the like, the mechanical input portion  12  of the fuel metering portion  3  may be temporarily received by the output portion  10  of the mechanical governor  2  and the output portion  9  of the electronic governor  1  may separate from the electronic input portion  11  of the fuel metering portion  3 . Conversely, in the event while the torque up is performed, the output portion  10  of the mechanical governor  2  advances too much to the fuel increase side or the output portion  9  of the electronic governor  1  does not move to the fuel increase side immediately, the electronic input portion  11  of the fuel metering portion  3  may be received by the output portion  9  of the electronic governor  1  and the output portion  10  of the mechanical governor  2  may temporarily separate from the mechanical input portion  12  of the fuel metering portion  3 . 
     The reference load is changed in the following manner and behavior. 
     When the reference load changing means (M) is switched over to the mode (M 2 ) with the speed setting means  18  shown in FIG. 2 set at a high speed position, as shown in FIG. 4, only the electronic speed control line  60  indicated by a one-dot chain line shifts to a high speed side and the reference load changes from the rated load (L 5 ) to the partial load (L 3 ). In this case, the steady state rotation speed (NX) of the electronic control at the partial load (L 3 ) of a new reference load is coincident with a steady state rotation speed (n 3 ) of the mechanical control at the same load (L 3 ). The steady state rotation speed (NX) of the electronic control at the loads (L 2 ) and (L 1 ) below the partial load (L 3 ) becomes lower than steady state rotation speeds (n 2 ) and (n 1 ) of the mechanical control at the same loads (L 2 ) and (L 1 ), respectively. The steady state rotation speeds (n 4 ) to (n 6 ) of the mechanical control at the loads (L 4 ) to (L 6 ) above the partial load (L 3 ) become lower than the steady state rotation speed (NX) of the electronic control at the same loads (L 4 ) to (L 6 ). As such the maximum fuel injection position  4  of the electronic control can be changed. 
     The engine rotation speed (N) is settled in the following behavior. 
     While the engine is in operation, at the partial load (L 3 ) of the reference load, based on the electronic speed control line  60  and the mechanical speed control line  51  both of the electronic governor  1  and the mechanical governor  2  set the fuel metering portion  3  to the maximum fuel injection position  4  and settle the engine rotation speed (N) on the respective steady state rotation speeds (NX) and (n 3 ) of the electronic control and the mechanical control. At the loads (L 2 ) and (L 1 ) below the partial load (L 3 ), based on the electronic speed control line  60  the electronic governor  1  settles the fuel metering portion  3  in the fuel decrease side area  5   a  of the speed control area  5  with respect to the maximum fuel injection position  4  and settles the engine rotation speed (N) on the steady state rotation speed (NX) of the electronic control. From the partial load (L 4 ) to the rated load (L 5 ) above the partial load (L 3 ), based on the mechanical speed control line  51  the mechanical governor  2  settles the fuel metering portion  3  in the fuel increase side area  5   b  with respect to the maximum fuel injection position  4  and settles the engine rotation speed (N) on the steady state rotation speeds (n 4 ) to (n 5 ) of the mechanical control. More specifically, the maximum fuel injection position  4  of the fuel metering portion  3  in the electronic control is adjusted to come to a halfway of the speed control area  5  of the fuel metering portion  3 . This device takes the composite control mode in which the electronic control automatically switches over to the mechanical control and vice versa at the maximum fuel injection position  4 . At the over-rated load (L 6 ), based on the torque-up line  52  the mechanical governor  2  conducts the torque-up. In this case, from the light load (L 2 ) to the no load (L 1 ), the settling is performed by the electronic control, so that even if the urging spring force  13   a  becomes smaller, hunting more hardly occurs than by the mechanical control. Thus the engine can employ an actuator  17  small in size and output. 
     The load fluctuation entails the following transition property. 
     When the load decreases from the partial load (L 3 ) of the reference load to the loads (L 2 ) and (L 1 ), the electronic control operates prior to the mechanical control. Conversely, when the load increases from the partial load (L 3 ) of the reference load to the loads (L 4 ) and (L 5 ), the mechanical control operates prior to the electronic control. However, in the event the load increases from the partial load (L 3 ) of the reference load to the over-rated load (L 6 ), although initially the mechanical control operates prior to the electronic control, the mechanical governor conducts the torque-up prior to the electronic control from a half way. For the same reason as in the case where the reference load is the rated load (L 5 ), while the electronic control is in operation, the mechanical input portion  12  of the fuel metering portion  3  may probably be received by the output portion  10  of the mechanical governor  2 . And while the mechanical control is in operation, the electronic input portion  11  of the fuel metering portion  3  may probably be received by the output portion  9  of the electronic governor  1 . 
     The speed setting is changed in the following manner and behavior. 
     When the speed setting means  18  changes the speed setting from a high speed to a low speed with the reference load changing means (M) shown in FIG. 2 set to the mode (M 1 ), as shown in FIG. 5, both the electronic speed control one dot chain line  60  and the mechanical speed control full line  51  make parallel movements toward the low speed side. Besides, when the speed setting means  18  changes speed setting from a high speed to a low speed with the reference load changing means (M) set to the mode (M 2 ), as shown in FIG. 6, both the electronic speed control one dot chain line  60  and the mechanical speed control full line  51  make parallel movements toward the low speed side. It is to be noted if the speed setting means  18  shifts the speed setting from the high speed side to the low speed side, the torque-up property disappears in an over-rated load area. 
     The engine rotation speed (N) is limited in the following manner and behavior. 
     In the event the speed setting means  18  sets a high speed while the reference load changing means (M) shown in FIG. 2 is set to the mode (M 2 ), as shown in FIG. 4, the steady state rotation speed (NX) of the electronic control at the partial load (L 3 ) of the reference load exceeds the engine rated rotation speed (NT). In this case, with a speed limiting switch  29  shown in FIG. 2 put on, as shown in FIG. 7 the controller  16  varies the reference load from the partial load (L 3 ) to the rated load (L 5 ). In this event, while the engine is in operation, from the loads (L 5 ) to (L 1 ) equal to and below the rated load (L 5 ) of a new reference load, the electronic governor  1  settles the engine rotation speed (N) on the same steady state rotation speed (NX′) of the electronic control as the rated rotation speed (NT). At the over-rated load (L 6 ) exceeding the rated load (L 5 ) of the new reference load, the mechanical governor  2  reduces the engine rotation speed (N) to the torque-up steady state rotation speed (n 6 ) lower than the rated rotation speed (NT). 
     The mecha-solo control is set in the following manner and behavior. 
     With an electronic working stop switch  31  as shown in FIG. 2 put on, the output portion  9  of the actuator  17  stands still at a working stop position  17   a  removed from a working range of the electronic input portion  11  of the fuel metering portion  3  toward the fuel increase side. In this case, the composite control of the electronic control and the mechanical control or the electro-solo control switches over to the mecha-solo control based on the mechanical speed control line  51  as shown in FIG.  8 . 
     The engine stops by the following construction. 
     This fuel supplying device is provided with a manual engine stop means  27  as shown in FIG.  2 . The engine stop means  27  comprises an stop actuation lever  27   a  and a stop output portion  27   b . The stop output portion  27   b  is cylindrical and is inserted into a guide bore  28   a  of an engine machine wall  28  so as to be able to advance and retreat. And it has a leading end which faces the electronic input portion  11  of the fuel metering portion  3 . When the stop actuation lever  27   a  pushes the stop output portion  27   b  toward the fuel decrease side, its leading end is brought into contact with the electronic input portion  11 , thereby pushing the fuel metering portion  3  against the urging spring force  13   a  to a fuel supply stop position  8 . Further, the actuator  17  can also push the fuel metering portion  3  to the fuel supply stop position  8 . This can dispense with a circuit and an actuator dedicated for an engine stop device. The actuator  17  has the output portion  9  urged by the spring  33 . Therefore, when disorder of the electronic governor  1  cancels energizing the actuator  17 , the output portion  9  pushes the fuel metering portion  3  through the urging force of the spring  33  to the fuel supply stop position  8  and stays it there. In this case, the engine cannot restart and therefore the disorder of the electronic governor  1  can be confirmed. 
     The electronic governor  1  has the following function. 
     The electronic governor  1  corrects the fuel supply so as to decrease it in the case of non-cold starting rather than in the case of cold starting. For this purpose, as shown in FIG. 1, the electronic governor  1  is provided with a temperature sensor  37 . The electronic governor  1  decreases the fuel supply in the engine starting area  7  in the case where the detected engine temperature exceeds a predetermined value when compared with the case where it is below the predetermined value. In other words, the electronic governor  1  holds the fuel metering portion  3  at a starting fuel increase limit position  7   a . The engine temperature can be sensed through detecting the engine machine wall temperature, engine cooling water temperature and engine oil temperature. Besides, it can be judged also by sensing the temperature of the air around the engine whether or not the engine makes the cold starting. This can inhibit the production of black smoke and the wasteful consumption of fuel. 
     The electronic governor  1  is also provided with a means  38  for detecting boost of intake air and has such a boost compensating function that it can correct the fuel supply for limitation until the pressure of the oversupplied intake air sufficiently increases. Additionally, the electronic governor  1  is provided with an atmospheric pressure detecting means  39  and has such a highland compensating function that it can correct the fuel supply for decrease when the atmosphere has a low pressure. Besides, the electronic governor  1  has an operation speed detecting means  40  so that it can suppress the working speed of the output portion  9  to prohibit the overshooting of the fuel metering portion  3  if the speed setting means  18  operates too fast. The fuel supply can be corrected for limitation or decrease by reducing the steady state rotation speed (NX) of the electronic control. It is to be noted such a function can be also effected by a fuel limiter which receives the fuel metering portion to restrict the fuel increase. 
     The actuator is controlled for starting and stopping in the following manner. 
     While the engine is in operation, the controller  16  stops the actuator  17  from working until the engine rotation speed (N) increases to a working start speed (ST) and starts the actuator  17  working when the engine rotation speed (N) increases to the working start speed (ST). Further, it makes the actuator  17  continue to perform the control working while the engine rotation speed (N) is in a predetermined controlled speed zone (Z) and stops the actuator from working when the engine rotation speed (N) is reduced to a lower limit value (ZL) of the controlled speed zone (Z). 
     The actuator  17  is set for starting control and stopping control in the following manner. 
     Upon determination of the steady state rotation speed (NX) of the electronic control at the reference load, the controller  16  sets the working start speed (ST) and the controlled speed zone (Z). The working start speed (ST) is set to the same value as the steady state rotation speed (NX) of the electronic control at the reference load. The controlled speed zone (Z) is set over a range of ±100 rpm from the steady state rotation speed (NX) of the electronic control at the reference load. This controlled speed zone (Z) includes the working start speed (ST) and the steady state rotation speed (NX) of the electronic control at the loads equal to and below the reference load. 
     The speed setting means  18  changes the speed setting and the reference load changing means (M) varies the reference load to move the electronic control property line toward the high speed side or the low speed side in parallel. On shifting of the steady state rotation speed (NX) of the electronic control at the reference load, the controller  16  shifts the working start speed (ST) and the controlled speed zone (Z) by the same value. For instance, when the reference load changing means (M) is switched over from the mode (Ml) to the mode (M 2 ), as shown in FIG. 4 the steady state rotation speed (NX) of the electronic control at the reference load shifts toward the high speed side by  5  rpm, but the controller  16  shifts the working start speed (ST) and the controlled speed zone (Z) toward the high speed side by the same value as that one. 
     Processing function of the controller  16  is outlined as follows. 
     As shown in FIG. 1, after the engine has started, the controller  16  stops the actuator  17  from working at Step S 1 . It judges at Step S 2  whether or not the engine rotation speed (N) has increased to the working start speed (ST). If the judgement is ‘NO’, the controller  16  returns to Step S. When the judgement at Step S 2  is ‘YES’, it starts the actuator  17  working at Step S 3 . 
     Further, it judges at Step S 4  whether or not the engine rotation speed (N) is within the controlled speed zone (Z). If the judgement is ‘YES’, it makes the actuator  17  continue the control working at Step S 5  and returns to Step S 4 . In the event the judgement at Step S 4  is ‘NO’, it judges at Step S 6  whether or not the engine rotation speed (N) has reduced to less than the lower limit value (ZL) of the controlled speed zone (Z). If the judgement is ‘YES’, the controller  16  returns to Step  1 . Negative judgement at Step S 6  means that the engine rotation speed (N) has increased to an upper limit value (ZH) of the controlled speed zone (Z). In this case, the controller  16  causes the actuator  17  to do an urgent fuel decrease working at Step S 7  and returns to Step S 4 . 
     While the engine is in operation, the controller  16  processes as outlined below. 
     While the engine is in operation, the controller  16  continues to deny the judgement made at Step S 2  and repeats the processing of Step S 1  until the engine rotation speed (N) increases to the working start speed (ST) before the actuator  17  starts working at Step S 3 . Thus, during this term, the actuator  17  continues its working stop state and the mechanical control is performed. In the working stop state at Step S, the output portion  9  of the actuator  17  stands still at the working stop position  17   a  removed from the working range of the electronic input portion  11  of the fuel metering portion  3  toward the fuel increase side. 
     The controller  16  affirms the judgement made at Step S 2  when the engine rotation speed (N) increases to the working start speed (ST), and it starts the actuator  17  working at Step S 3 . After the actuator  17  has started working, while the engine rotation speed (N) is in the controlled speed zone (Z), the controller  16  continues to affirm the judgement made at Step S 4  and repeats the processing of Step  5 , thereby causing the actuator  17  to continue its control working. When the engine rotation speed (N) has decreased to less than the lower limit value (ZL) of the controlled speed zone (Z), the controller  16  denies the judgement made at Step S 4  and affirms the judgement made at Step S 6  to return the actuator  17  to the working stop state of Step S 1  prior to the commencement of the electronic control working. In this case, the fuel metering by the mechanical governor  2  is performed and thereafter the foregoing control is repeated. 
     If the engine rotation speed (N) exceeds the upper limit value (ZL) of the controlled speed zone (Z), the controller  16  denies the judgement made at Step S 4  and subsequent judgement made at Step S 6  to make the actuator  17  perform the urgent fuel decrease working at Step S 7 . The performed urgent fuel decrease working moves the output portion  9  of the actuator  17  in a direction for fuel decrease and the fuel metering portion  3  toward the fuel decrease side. During the urgent fuel decrease working, the controller  16  repeats the judgements made at Step S 4  and Step S 6  and temporarily interrupts the control working of the actuator  17  at Step S 5  until the engine rotation speed (N) enters the controlled speed zone (Z). When the engine rotation speed (N) returns to the controlled speed zone (Z), the controller  16  affirms the judgement made at Step S 4  and causes the actuator  17  to continue the control working at Step S 5  interrupted before. 
     The detailed processing of the controller  16  is as follows. 
     Processing at the time of engine start. 
     As shown in FIG. 9, at the time of engine start, the controller  16  judges at Step S 11  whether or not an accessory switch is ‘ON’. If the judgement is ‘YES’, it sets the duty ratio of the PWM wave to maximum so as to energize the actuator  17  of the electronic governor  1  in a maximum amount. In this case, the actuator  17  has the output portion  9  greatly pulled toward the fuel increase side to stand still at the working stop position  17   a  removed from the working range of the electronic input portion  11  of the fuel metering portion  3  toward the fuel increase side and comes to the working stop state. 
     Processing to confirm the engine start. 
     The controller  16  judges at Step S 13  whether or not a starter switch is ‘ON’. If the judgement is ‘YES’, it waits for 0.5 seconds at Step S 14 . Then it judges at Step S 15  whether or not the engine rotation speed (N) has reached an idling rotation speed (n 7 ) to ascertain the engine start. Conversely, when the judgement is ‘NO’, it sets an error flag at Step S 16  and then returns to Step S 13 . The controller  16  interrupts sequential control processing at a predetermined cycle to detect whether or not the error flag is set. Provided that the error flag is set continuously a plurality of times, it performs an error processing. This error processing is conducted by setting the duty ratio of the PWM wave to maximum and maintaining the actuator  17  in the working stop state. In addition, it simultaneously alarms abnormality. 
     The error processing is conducted similarly not only in the case of erroneous engine start but also in such cases as, for example, detection of abnormal control by a watch dog timer to be mentioned later; breakage of the speed detecting means  15  and the set speed detecting means  18   c ; short; appearance of the voltage detected outside the optimum range; and so on. 
     Even in the event other various abnormalities are detected, the same error processing as mentioned above is effected. 
     Processing to set the electronic control property 
     If the controller  16  judges ‘YES’ at Step S 15 , it sets the watch dog timer at Step S 17  and judges at Step S 18  which of the modes (Ml) and (M 2 ) the reference load changing means (M) has selected. At Step S 19  or Step S 20 , it reads the speed setting voltage sent from the set speed detecting means  18   c . Then the controller  16  sets the electronic control property at Step S 21  based on the speed setting voltage and the mode selected by the reference load changing means (M). 
     The controller  16  processes at Step S 22  and subsequent Steps as follows. 
     As shown in FIG. 10, the controller  16  judges at Step S 22  whether or not the engine rotation speed (N) is not less than the lower limit value (ZL) of the controlled speed zone (Z). And it sets a ZL flag at Step S 23  and resets the ZL flag at Step S 24 . Then it judges at Step S 25  whether or not the engine rotation speed (N) is not less than the working start speed (ST) and judges at Step S 26  whether or not the engine rotation speed (N) is not less than the upper limit value (ZH) of the controlled speed zone (Z). 
     The controller  16  sets a PID flag at Step S 27  and carries out a PID calculation at Step S 28 . It sets the duty ratio of the PWM wave in correspondence to a value resulting from the PID calculation at Step  29 , adjusts the output of the actuator  17  at Step S 30  and resets the watch dog timer at Step S 31 . After Step S 31 , it returns to Step S 17 . Further, the controller  16  judges at Step S 32  whether or not the PID flag is set. It resets the PID flag at Step S 33  and sets the duty ratio of the PWM wave to maximum at Step S 34 . At Step S 35  it judges whether or not the ZL flag is set. Additionally, it sets the duty ratio of the PWM wave to minimum at Step S 36 . At Step S 28  the PID calculation is carried out without totalizing the data gained before the actuator  17  starts working. The PID control may be replaced by PI control. 
     While the engine is in operation, the detailed processing of the controller  16  is as follows. 
     The following processing continues the working stop state of Step S 1 . 
     Before the actuator  17  starts working at Step S 3 , the controller  16  repeats the processing of Step S 1  until the engine rotation speed (N) increases up to the working start speed (ST), thereby continuing the working stop state of the actuator  17  at Step S 1 . In this case, the controller  16  repeats sequential processing of: denying the judgement made at Step S 22 ; conducting the processing of Step S 24 ; denying the judgement made at Step S 25 ; denying the judgement made at Step S 32 ; conducting the processing of Step S 33 ; keeping the duty ratio of the PWM wave maximum at Step S 34 ; and maintaining the output of the actuator  17  maximum at Step S 30 . 
     Working starts at Step S 3  by the following processing. 
     At Step S 3  the actuator  17  starts working in the case where the engine rotation speed (N) has increased to the working start speed (ST). In this case, the controller  16  conducts sequential processing of: affirming the judgement made at Step S 22 , conducting the processing of Step S 23 ; affirming the judgement made at Step S 25 ; denying the judgement made at Step S 26 ; conducting the processing of Step S 27 ; calculating a deviation between the steady state rotation speed (NX) and the engine rotation speed (N) at Step S 28 ; setting the duty ratio of the PWM wave in correspondence to the calculated deviation value at Step S 29 ; and adjusting the output of the actuator  17  at Step S 30 . 
     The control working of Step S 5  continues by the following processing. 
     While the engine rotation speed (N) is within the controlled speed zone (Z), the controller  16  repeats the processing of Step S 5 , thereby continuing the control working of the actuator  17  at Step S 5 . In the event the engine rotation speed (N) is not less than the working start speed (ST), the controller  16  repeats the same sequential processing as in the case of working start. If the engine rotation speed (N) is less than the working start speed (ST), the controller  16  repeats sequential processing of: affirming the judgement made at Step S 22 ; conducting the processing of Step S 23 ; denying the judgement made at Step S 25 ; affirming the judgement made at Step S 32 ; affirming the judgement made at Step S 35 ; and conducting the sequential processing of Step  28 , Step  29  and Step S 30 . 
     The controller  16  returns to Step S 1  by the following processing. 
     It returns to the working stop state of the actuator  17  at Step S 1  when the engine rotation speed (N) has reduced to less than the lower limit value (ZL) of the controlled speed zone (Z). In this case, the controller  16  does the processing of: denying the judgement made at Step S 22 ; conducting the processing of Step S 24 ; denying the judgement made at Step S 25 ; denying the judgement made at Step S 32 ; conducting the processing of Step S 33 ; setting the duty ratio of the PWM wave to maximum at Step S 34 ; and adjusting the output of the actuator  17  to maximum at Step S 30 . 
     The following processing carries out the urgent fuel decrease working at Step S 7 . 
     The urgent fuel decrease working of the actuator  17  at Step S 7  is effected in the case where the engine rotation speed (N) has exceeded the upper limit value (ZH) of the controlled speed zone (Z). In this case, the controller  16  repeats the processing of: affirming the judgement made at Step S 22 ; conducting the processing of Step S 23 ; affirming both of the judgements made at Step S 25  and Step S 26 ; setting the duty ratio of the PWM wave to minimum at Step S 36 ; and adjusting the output of the actuator  17  to minimum at Step S 30 . 
     FIG. 11 shows a first modification of the first embodiment. In this first modification, when the speed setting means  18  shown in FIG. 2 sets a high speed and the reference load changing means (M) selects the mode (Ml), the electronic speed control one-dot-chain line  60  in FIG. 11 crosses an upper limit of the torque-up line  52  at a maximum load (L 7 ). In this case, the device takes the electro-solo control mode. FIG. 12 shows a second modification of the first embodiment. In this second modification, when the speed setting means  18  shown in FIG. 2 sets a low speed and the reference load changing means (M) selects the mode (M 1 ), as shown in FIG. 12, on condition that the steady state rotation speed (NX) of the electronic control at the loads (L 1 ) to (L 6 ) is lower than a maximum torque rotation speed (NM), the controller  16  alters the isochronous control property to the droop control property and approaches the steady sate rotation speed (NX) of the electronic control to the maximum torque rotation speed (NM) as the load increases. 
     The droop control property requires to detect the load because the steady state rotation speed (NX) of the electronic control differs in correspondence to the load. None of the above embodiments includes a metering position detecting means which directly detects the metering position of the fuel metering portion  3 . Therefore, the load cannot be detected by such means. However, it is possible to detect the load by other means. For instance, the metering position of the fuel metering portion  3  and eventually the load can be indirectly detected through sensing an electric current value of an actuator driving circuit when the engine rotation speed (N) has been settled on the steady state rotation speed (NX) of the electronic control. Further, the load may be detected through detecting a distortion caused by a twist of the crank shaft with a torque sensor. However, in the event priority is put on cost reduction, the engine does not employ any or a part of the above-mentioned sensor, the temperature sensor  37 , the boost sensor  38 , the atmospheric pressure sensor  39  and the operation speed detecting means  40 . 
     FIGS. 13 to  15  explain a fuel supplying device according to a second embodiment. 
     This second embodiment is distinct from the first embodiment on the following points. 
     The speed setting means  18  shown in FIG. 13 comprises a speed setting means  18   a  for the electronic governor  1  and a speed setting means  18   b  for the mechanical governor  2 . These speed setting means  18   a  and  18   b  set speeds to set the electronic control property and the mechanical control property independently, thereby making it possible to set the level of the reference load freely. 
     Employed for the speed setting means  18   b  of the mechanical governor  2  is a pedal, which is interlockingly connected to the connecting rod  22 . An engaging lever  24  is provided near the connecting rod  22 . After having moved the speed setting means  18   b  to an optional setting position, the lever  24  engages with the connecting rod  22 , thereby preventing the return of the speed setting means  18   b  to the low speed side from the optional setting position. The other construction and function are the same as those of the first embodiment. In FIGS. 13 to  15 , the same elements as those in the first embodiment are designated by the same characters. 
     The electronic control property and the mechanical control property are set in the following manner and behavior. 
     In the event that the respective speed setting means  18   a  and  18   b  set high speeds, the same composite control property as shown in FIG. 3 can be obtained, thereby making it possible to perform a high speed operation in which the rated load (L 5 ) is set as the reference load. If only the speed setting means  18   a  for the electronic governor  1  slightly shifts from this state toward the high speed side, the same composite control property as shown in FIG. 4 can be attained, thereby making it possible to perform a high speed operation in which the partial load (L 3 ) is set as the reference load. 
     In the event the respective speed setting means  18   a  and  18   b  set low speeds, the same composite control property as shown in FIG. 5 can be gained, thereby making it possible to perform a low speed operation in which the rated load (L 5 ) is set as the reference load. If only the speed setting means  18   a  for the electronic governor  1  slightly shifts from this state toward the high speed side, the same control property as shown in FIG. 6 is obtained, thereby making it possible to perform a low speed operation in which the partial load (L 3 ) is set as the reference load. The speed settings of the respective speed setting means  18   a  and  18   b  are combined with each other in various ways to thereby attain various sorts of control properties different in speed setting and reference load. 
     When the speed setting means  18   a  for the electronic governor  1  sets a high speed and the speed setting means  18   b  for the mechanical governor  2  sets a low speed, as shown in FIG. 14, the steady state rotation speeds (n 1 ) to (n 6 ) of the mechanical control at the loads (L 1 ) to (L 6 ) each comes to a value less than the control working start speed (ST) of the electronic governor  1 . Therefore, the electronic control is not performed, thereby enabling the composite control of the electronic control and the mechanical control or the electro-solo control to switch over to the mecha-solo control. 
     When the speed setting means  18   a  for the electronic governor  1  and the speed setting means  18   b  for the mechanical governor  2  set a low speed and a high speed, respectively, and the steady state rotation speed (NX) of the electronic control at the loads (L 1 ) to (L 6 ) becomes lower than the maximum torque rotation speed (NM) as shown in FIG. 15, the controller  16  alters the isochronous control property to the droop control property and approaches the steady state rotation speed (NX) of the electronic control to the maximum torque rotation speed (NM) as the load increases. 
     FIG. 16 explains a third embodiment of the present invention. This third embodiment differs from the first embodiment in that it includes a metering position detecting means  30  for the fuel metering portion  3 . FIG. 17 explains a fourth embodiment of the present invention. This fourth embodiment is distinct from the second embodiment in that it includes a metering position detecting means  30  for the fuel metering portion  3 . Each of these third and fourth embodiments has the metering position detecting means  30  for the fuel metering portion  3 , so that generally the electronic governor  1  produces a faster steady state speed. Therefore, in these embodiments, the electronic governor  1  may be adjusted so as to always work without setting the working start speed (ST) and the controlled speed zone (Z).