JPS634010B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an internal combustion engine in which a rotation speed adjustment element such as a throttle valve of the internal combustion engine is controlled by an electric control device and an operating means such as a servo motor to control the engine rotation speed to a set rotation speed. This invention relates to a rotation speed control device.

Conventionally, when the purpose of this type of device was to control the rotation speed of an internal combustion engine that drives the generator of a power generator for an electric welding machine, for example, after the engine was started, the activation switch or the set rotation speed setting switch, etc. were manually operated. The engine rotation speed is controlled to a predetermined set rotation speed to obtain the power output necessary for electric welding work, and when the work is finished, the engine rotation speed is controlled by manually operating the operating switch or the set rotation speed setting switch, etc. Since it is necessary to take steps such as returning the engine to the idling speed at startup, it is troublesome to repeat the above steps when electric welding involves temporary interruptions or is performed intermittently. After completion of the engine rotation, it is common to carry out the manual operation such as returning the engine speed to the idling speed. As a result, the engine is controlled at a predetermined rotational speed even when electric welding is not being performed, resulting in unnecessary engine fuel consumption and noise generation.

The present invention was made in order to solve the above problem, and it electrically detects the error between the rotation speed of the internal combustion engine and the set rotation speed set by the rotation speed setting device, and adjusts the engine rotation speed according to this error. In an apparatus equipped with an operation means for operating an element, a plurality of the rotation speed setters for setting a rotation value according to the load are provided, and an error between the operation amount of the engine rotation speed adjustment element and the set value of this operation amount is corrected. By determining the error and selecting one of the plurality of rotation speed setters to control the rotation speed according to this error, the engine rotation speed can be adjusted to a set value according to the load without repeated manual operations. The object of the present invention is to provide a rotational speed control device for an internal combustion engine, which can automatically switch and control the engine speed and reduce engine fuel consumption and noise generation during no-load conditions.

The present invention will be described in detail below with reference to the drawings. FIG. 1 is a block diagram showing one embodiment of the apparatus of the present invention. 1 is an electric control circuit that generates a command signal by comparing the engine rotation speed and a set rotation speed; 2 is a solenoid valve-controlled fluid servo motor that serves as an operating means that operates in response to the command signal; 3 is a fluid A throttle valve which is a rotational speed regulating element of an internal combustion engine operated by a servo motor 2, a magneto-ignition type gasoline engine which forms the internal combustion engine, and a rotation valve 5 which generates an alternating current signal with a frequency corresponding to the rotational speed of the internal combustion engine. 6 is a control amount detector consisting of a potentiometer that detects the control amount of the throttle valve 3 by the fluid servo motor 2, which corresponds to the operating end position P of the fluid servometer 2. to generate the manipulated variable voltage Vp. Reference numeral 7 denotes a set rotation speed selection circuit which selects one of the plurality of rotation speed setters in response to the manipulated variable voltage Vp from the manipulated variable detector 6 and generates the rotation speed set voltage V _S ;
is a fail-safe circuit that performs safe control when the engine speed enters an abnormal range.

Further, the electrical control circuit 1 detects the rotational speed N by an AC signal generated from the rotational speed detector 5.
A first rotation speed voltage generation circuit _{14 that generates a DC voltage V N1 proportional to} Comparison calculation circuit 15
and a solenoid valve drive circuit 16 that drives the solenoid valve 17 of the liquid servo motor 2 according to the comparison signal.

Further, the set rotation speed selection circuit 7 includes the operation amount detector 6, a first rotation speed setter 9 that generates a rotation speed setting voltage V _SH corresponding to the set rotation speed for work,
A second rotation speed setter 10 generates a rotation speed setting voltage V _SL corresponding to a low set rotation speed, and a rotation speed setting device 10 that generates a rotation speed setting voltage V SL corresponding to a low set rotation speed, and a rotation speed setting device 10 that generates a rotation speed setting voltage V SL corresponding to a low rotation speed setting, and A manipulated variable setter 11 generates a manipulated variable setting voltage V _Q corresponding to the manipulated variable set value that serves as a reference for determination, and compares and discriminates the manipulated variable voltage Vp with the manipulated variable set voltage V _Q and generates an error signal. The error discriminator 12 selects either the first rotation speed setter 9 or the second rotation speed setter 10 based on the error signal from the error discriminator 12 and sets the rotation speed setting voltage V _S to V _SH Alternatively, it is constituted by a setter selection circuit 13 that generates one of _VSL .

The fail-safe circuit 8 includes a second rotation speed voltage generating circuit 19 that generates a DC voltage V _{N2 proportional to the rotation speed N based on the AC signal from the lighting/charging power supply coil 5, and a second rotation speed voltage generating circuit 19 that generates a DC voltage V N2} proportional to the rotation speed N, and a circuit that generates a DC voltage V N2 proportional to the rotation speed N, and a circuit that generates a DC voltage V Rotation speed abnormality detection that sets the corresponding minimum voltage Vmin and maximum voltage Vmax and generates a rotation speed abnormality signal when the rotation speed voltage V _N2 deviates from the range of Vmin < V _N2 < Vmax, that is, enters the abnormal region. When an abnormal rotational speed signal is generated in the circuit 20, the electromagnetic valve 17 of the fluid servo motor 2 is de-energized to release the operating function of the hydraulic actuator 18, and the ignition system of the internal combustion engine 4 is shut off to stop rotation. It consists of a cutoff circuit 21.

Fig. 2 is a diagram showing the structure of each part element, 30
2 is a carburetor, 22 is an intake pipe having a throttle valve 3, 23 is a throttle operating lever, 24 is a return spring for the throttle valve 3, 25 is an operating rod, 26 is a housing of the hydraulic actuator 18, 27 is an action chamber, 28
is a movable wall. The solenoid valve 17 has a high hydraulic pressure flow path 2 generated from the hydraulic pump 38 of the engine 4 through the action chamber 27.
A three-way switching solenoid valve is used to open and close the low oil pressure flow path 33 returning to the engine 4. 31 is a movable wall 28
The return spring 32 is an operating end that obtains operating force for operating the controlled object as the position of the movable wall 28 changes. Further, the manipulated variable detector 6 is interlocked with the operating end 32 so as to generate a manipulated variable voltage Vp corresponding to the position of the movable wall 28. Reference numeral 34 denotes a magneto, which is equipped with an ignition coil 35, a breaker contact 36, and a lighting/charging power source coil 5 that serves as a rotational speed detector. A lighting/charging power supply coil 5 is used. The hydraulic actuator 18 communicates with the high hydraulic pressure passage 29 when the working chamber 27 energizes the coil 17a of the solenoid valve 17, and when the high hydraulic pressure enters the working chamber 27, the movable wall 28 moves in the direction of arrow a. Then, the throttle valve 3 is opened via the operating rod 25 and the throttle operating lever 23. Also,
When the coil 17a of the solenoid valve 17 is not energized, the action chamber 27 communicates with the low oil pressure flow path 33 side, and the self-returning function of the return springs 24 and 31 causes the movable wall 28 to move in the direction opposite to arrow a, and the throttle valve 3 to be operated to the deceleration side. On the other hand, an AC signal with a frequency corresponding to the engine speed is detected from the lighting/charging power source coil 5 and applied to the electrical control circuit 1 and the failsafe circuit 8, and also corresponds to the position of the operating end 32 of the hydraulic actuator 18. The manipulated variable voltage
Vp is applied from the manipulated variable detector 6 to the control circuit 1 and the set rotation speed selection circuit 7. Furthermore, when the engine speed enters an abnormal range due to the fail-safe circuit 8, power is cut off to the coil 17a of the solenoid valve 17 in order to operate the throttle valve 3 to the deceleration side, and at the same time, the breaker contact 36 of the magneto 34 is grounded. The engine is designed to shut off the ignition and immediately stop engine rotation.

Next, the control circuit 1, set rotation speed selection circuit 7, and fail-safe circuit 8 will be explained using the electrical circuit diagram shown in FIG. An alternating current signal having a frequency corresponding to the rotational speed N of the engine 4 is detected by the lighting/charging power source coil 5 of the magneto 34, and is applied to the input terminal 1a. In the first rotational speed voltage generation circuit 14, a diode 50, a constant voltage diode 52, a capacitor 53, and resistors 51, 54, 5
5, 57, after waveform shaping through transistor 56, capacitors 58, 65, diode 60,
62, 63, 64, 68, resistors 61, 67, and a transistor 66 for DC conversion, and further resistors 69, 70, 71, 72, a differential operational amplifier 75, and a resistor that determines the gain. 7
The voltage is inverted and amplified by an inverting amplifier circuit consisting of 3 and 74, and as its output, a rotational speed voltage V _N1 whose relationship with the engine rotational speed N is shown in the characteristic diagram of FIG. 4 is generated at point A. Note that 158D is a 4-pole contact type relay 1.
When the contact 158D is located on the a side, a low gain is obtained, and when the contact 158D is located on the b side, a high gain is obtained by the two resistors 73 and 74 that determine the gain of the inverting amplifier circuit. . Further, the operation amount detector 6 is connected to the operation end 32 of the hydraulic actuator 18.
The position P of the operating end 32 is detected in conjunction with the
Corresponding to the position P, the manipulated variable voltage Vp is generated at six points. The rotation speed setting voltage V _S from the rotation speed selection circuit 7 is generated at the S point.

Here, the comparison calculation circuit 15 calculates the manipulated variable voltage Vp
and rotation speed setting voltage V _S , input resistance 76, 77
Calculation is performed by an operational amplifier circuit consisting of a differential operational amplifier 80, a resistor 79 for determining gain, and a capacitor 78 for differentiating the manipulated variable voltage Vp,
The rotation speed setting voltage V _S is calculated by calculating the setting voltage V _F corresponding to the position P of the operating end 32 of the hydraulic actuator 18.
occurs at point F. Further, the comparison calculation circuit 15 converts the calculation setting voltage V _F and the rotation speed voltage V _N1 generated at the point A of the first rotation speed voltage generation circuit 14 into input resistors 81, 82, a capacitor 83, and a differential type calculation. A comparator circuit compares the signals from the amplifier 84 and generates a comparison operation signal. The relationship between the operation end position P of the hydraulic actuator 18 and the operation amount voltage Vp is shown in _FIG .
The minimum opening degree of the throttle valve 3) is the maximum (the maximum opening degree of the throttle valve 3) when P=P _M. The electromagnetic valve drive circuit 16 is an amplifier for amplifying the comparison signal from the comparison operation circuit 15 to drive the electromagnetic valve 17, and includes a transistor 87, resistors 85, 86, 88, 91, a capacitor 89, and a diode 90. When the transistor 86 is turned on, the coil 17a of the solenoid valve 17 is energized. The resistor 91 improves the opening speed of the solenoid valve 17, and the resistor 88, capacitor 89, and diode 90 protect the transistor 87 from reverse activation that occurs when the current in the coil 17a of the solenoid valve 17 is cut off. ing.

Note that 140 is a general power supply circuit composed of a diode, a resistor, a capacitor, and a voltage regulator 141, which generates a stabilized power supply voltage Vcc at point M.

Next, the set rotation speed selection circuit 7 generates a rotation speed setting pressure V _SH corresponding to the set rotation speed for work at a point 9a by a variable resistor 9 forming a first rotation speed setting device,
The rotation speed setting voltage V _SL corresponding to the low setting rotation speed is set to 1 by the variable resistor 10 forming the second rotation speed setting device.
This occurs at point 0a. In addition, a manipulated variable setter 11 consisting of a variable resistor generates a manipulated variable setting voltage V _Q at a point 11a, and an error discriminator 12 generates a manipulated variable voltage Vp from the manipulated variable detector 6 and a manipulated variable voltage Vp generated at a point 11a. The manipulated variable setting voltage V _Q is resistor 150,
151, capacitor 152, differential operational amplifier 1
A comparator circuit consisting of 53 performs comparison and discrimination and generates an error signal at point 153a. When Vp>V _Q , this error signal becomes a voltage of 0V, and when Vp< _VQ , it becomes a voltage of the power supply voltage Vcc. .

The setting device selection circuit 13 operates the four-pole contact type relay 158 based on the error signal from the error discriminator 12 to switch the contacts 158A, 158B, 158C, and 158D from a to b, and from b to a, thereby determining the rotation speed. One of the variable resistors 9 and 10 forming the setter is selected, and either V _SH or V _SL is applied to the S point of the control circuit 1 as the rotation speed setting voltage V _S . When the error signal generated at point 153a is 0V (Vp>V _Q ), transistor 157 is "OFF", the coil of relay 158 is not energized, and each contact of relay 158 is located on the a side. Therefore, the rotation speed setting voltage V _S applied to the point S through the contact 158C is V _S =V _SL . At this time, the power supply voltage Vcc is applied to the point 163a of the capacitor 163 through the contact 158B and the diode 162.
is added, charging the capacitor 163 and turning on the transistor 165 through the resistor 164, and turning off the transistor 168. Therefore, the power supply voltage is connected to the base terminal of the transistor 171 through the resistors 169 and 170.
Vcc is applied, and the transistor 171 maintains the "ON" state. Here, from Vp>V _Q to Vp<
V _Q and the power supply voltage Vcc is generated at point 153a, the diode 154, resistors 155, 156
Transistor 157 is turned "ON" through , and by energizing the coil of relay 158, each contact of relay 158 is switched from side A to side B, and the rotation speed setting voltage is applied to point S through contact 158C.
V _S becomes V _S =V _SH . At this time, the diode 162
Although the power supply voltage Vcc is no longer applied to the point 163a through the resistor 160 and the diode 161, the transistor 171 maintains the "ON" state as described above.

Furthermore, when Vp<V _Q becomes Vp>V _Q ,
Since the voltage at 153a becomes 0V, the transistor 157 is turned off, and the power supply voltage Vcc is no longer applied to point 163a through the resistor 160 and diode 161, but the base current flows to the transistor 165 through the resistor 164 due to the charging voltage of the capacitor 163. Continuing, the transistor 165 remains "ON" for a period of time until the charging voltage of the capacitor 163 decreases and the transistor 165 is turned "OFF", that is, a time constant time T determined by the capacitor 163 and the resistor 164. There is. Therefore, the transistor 171 also maintains the "ON" state, and the coil of the relay 158 is connected to the terminal b of the contact 158A.
Since the transistor 171 continues to supply current through the side and each contact of the relay 158 is on the b side, V _S =V _SH is maintained at the S point.

Furthermore, if Vp<V _Q again occurs during the time T determined by the capacitor 163 and the resistor 164, and the power supply voltage Vcc is generated at the point 153a, the transistor 157 also becomes "ON" and the resistor 16
0, capacitor 163 through diode 161
is charged to the power supply voltage Vcc again, but if Vp<V _Q does not again occur during time T and the state of Vp>V _Q continues, transistor 165 turns "OFF" after time T and transistor 171 Also “OFF”,
In addition, since the transistor 157 is also "OFF", the coil of the relay 158 is no longer energized, and each contact of the relay 158 is switched from the b side to the a side, and the rotation speed setting voltage V _S generated at the S point is V It becomes _SL . Note that when the contact 158D of the relay 158 is located on the a side, it has a low gain determined by the resistors 73 and 74 that determine the gain of the first rotational speed voltage generation circuit 14, and when it is located on the b side, it is determined by the resistor 73. The gain is high.

Furthermore, the second rotational speed voltage generation circuit 19 in the fail-safe circuit 8 functions in the same manner as the first rotational speed voltage generation circuit 14, so its explanation will be omitted.

Note that the output voltage V _N2 is generated at point B. In addition, the rotation speed abnormality detection circuit 20 connects a resistor 114 and a voltage Vmax corresponding to the maximum rotation speed for abnormality detection of the engine.
15, and set the voltage Vmin corresponding to the minimum rotation speed for abnormality detection with the base-emitter saturation voltage V _BE (sat) specific to the transistor 123,
The rotation speed voltage V _N2 is compared and determined with Vmax and Vmin, and when V _N2 deviates from the range of Vmin<V _N2 <Vmax, a rotation speed abnormal signal is generated. That is, the rotation speed voltage V _N2 is determined by the differential operational amplifier 119, resistors 116 and 117, and capacitor 11.
8 is compared with the Vmax, and the transistor 123 and the resistor 122 are used to determine the Vmin.
It is compared and determined. Furthermore, when comparing and determining V _N2 and Vmin, resistors 124 and 125 and capacitor 1
The time for comparison and determination is delayed by a time constant determined by 26, and the resistor 120 and diodes 121 and 127 constitute an OR circuit to generate a rotational speed abnormal signal at point C. When an abnormal rotational speed signal occurs at point C, the capacitor 12
8, resistor 129, thyristor 130, relay 13
1. A cutoff circuit 20 made of a diode 132 switches from the contact 131a side of the relay 123 to the 131b side to cut off the current flow to the coil 17a of the solenoid valve 17 and short-circuit the breaker contact 36 in the magneto 34 to ground.

In addition, 40 is a rectifier, 41 is a battery power supply,
42 is a key switch for the engine 4, and 43 is a power switch for the control device.

Here, the operation of this embodiment will be explained. After starting the engine, by turning on the power switch 43 of the control device, the rotation speed voltage V _N1 generated at point A corresponding to the engine rotation speed, the rotation speed setting voltage V _S applied to point S, and the hydraulic actuator 18 are set. The operation amount voltage Vp corresponding to the operation end position P is compared with the calculated set voltage V _F (Fig. 5) generated at point F, and when V _F < V _N1 , the solenoid valve 17 is energized. , high hydraulic pressure flows into the working chamber 27 of the hydraulic actuator 18, the movable wall 28 and the operating end 33 move in the direction of arrow a, and the throttle valve 3 is opened. As a result, when the engine speed increases, the rotation speed voltage increases.
As V _N1 decreases, the calculation setting voltage V _F increases. In addition, in the state of V _F > V _N1 , the electromagnetic valve 17 is de-energized, and the working chamber 2 of the hydraulic actuator 18 is closed.
7 and the low oil pressure flow path 30 communicate with each other, and the return spring 24,
31, the movable wall 28 moves in the direction opposite to the arrow a, closing the throttle valve 3 and reducing the engine speed. As a result, the engine speed becomes the set speed N _S
In this process, the operating end position P of the actuator 18 is shifted from _Po to P ₁ in the characteristic diagram shown in Fig. 5.
Since it moves back and forth and is in an equilibrium state, and Vp > V _Q is established, each contact of the relay 158 of the set rotation speed selection circuit 7 is located on the a side, and the rotation speed generated at the S point is set. The voltage V _S is V _SL , and the engine speed is operated at a low set speed N _SL . Here, when a predetermined load is instantaneously applied to the engine, the engine speed drops instantaneously, V _F < V _N1 , and the solenoid valve 17 is energized to open the throttle valve 3, and the operating end of the actuator 18 is The position P also instantaneously becomes P>P _S , and once the relationship Vp<V _Q is established. Then, each contact of the relay 158 changes from a to b, and the rotation speed setting voltage V _S applied to the S point becomes V _SH , and the engine rotation speed is operated at the work setting rotation speed V _SH , and the predetermined load by the engine is It becomes possible to perform driving work. At this time, the operating end position P of the actuator 18 is in an equilibrium state around _P2 , and Vp
＞V _Q is established, but if a predetermined load driving work is performed within the time constant time T, the engine speed is controlled to be close to the work setting speed N _SH and the operating end position P is in an equilibrium state before and after P _L , and the relationship Vp<V _Q holds, so the rotation speed setting voltage V _SH is continuously applied to the S point. After that, the predetermined load driving work is no longer performed, and the operating end position P is balanced around _P2 , and P<P _S , Vp
> V _Q and the predetermined load driving work is not repeated. After the time constant time T, each contact of the relay 158 of the set rotation speed selection circuit 7 changes from b to a, and the rotation speed setting voltage V _S becomes V _SH changes to V _SL , and the engine speed is operated at the low set speed N _SL .

In other words, by instantaneously applying a predetermined load to the engine, the engine rotation speed changes from the low set rotation speed N _SL to the work set rotation speed N _SH , and the predetermined load driving work is intermittently repeated. At this time, if the non-working time is within the time constant time T, the engine speed is controlled to approach the set working speed _N It is restored to numbers. Note that the manipulated variable setting value P _S , which is the standard for determining the predetermined load drive work start time and non-work time, is P ₁ , P ₂ <P _S <
A manipulated variable setting voltage V _Q that is set within the range of P _L and corresponds to the manipulated variable set value P _S is set by the variable resistor 11 .

In addition, the set rotation speed selection circuit 7 selects the rotation speed setting voltage V _SL by switching the contact 158D of the relay 158.
By setting the gain of the first rotational speed voltage generating circuit 14 to a low gain when applying V _SH to the S point to stabilize the low rotational speed control of the engine, and setting it to a high gain when applying the rotational speed setting voltage V SH It also has a function to reduce the engine speed fluctuation rate during load driving work.

Therefore, by making the rotation speed control device equipped with the set rotation speed selection circuit 7, when used, for example, to control the rotation speed of an internal combustion engine that drives a generator of a power generation device for an electric welding machine, Just turn on the power switch of the control device once after starting the engine,
The engine speed is operated at a low set speed, and when the generator load is instantaneously applied to the engine by instantaneously shooting both pole terminals of the electric welding machine and causing current to flow from the generator, the engine speed decreases. The generator starts operating at the set rotational speed for work, generates a predetermined power supply, and becomes ready for electric welding work. In addition, when work is repeated intermittently with temporary interruptions, there is no need to repeatedly operate the power switch or rotation speed setting switch, etc., and the power is automatically turned off after a certain period of time when the machine is not working. When the set rotation speed is reached and the work is to be started again, the engine speed becomes the set rotation speed for work again by momentarily shorting both pole terminals of the electric welding machine, and the power generation device generates the specified power. be able to. Then, when the engine is not working, the engine is automatically operated at a low set rotation speed that is lower than the set rotation speed for working, thereby reducing engine fuel consumption and noise generation.

Here, if a failure of the rotation speed detector, a failure of the electrical control mechanism, etc. occurs and the engine rotation speed is about to increase abnormally, the fail-safe circuit 8 cuts off the power to the solenoid valve 17 and shuts off the fugnet 34. By short-circuiting the breaker contact 36 to ground and stopping the ignition function of the engine, the rotation of the engine is immediately stopped, and damage accidents caused by over-speeding of the engine and the generator driven by the engine are prevented. can do.

Note that the engine 4 is not limited to a magneto ignition type gasoline engine, but may also be a general gasoline engine, and the engine 4 is not limited to one that uses an alternating current signal from the lighting/charging power supply coil 5 to detect the rotation speed. The ignition pulse of the ignition system may also be used.
Furthermore, the electrical control circuit 1 may be one that performs other analog control or one that performs digital control. In addition to the servo motor 2, the operating means may be one that uses negative pressure, or one that uses an electric motor without using a working fluid. In addition, in the above embodiment, the manipulated variable voltage Vp from the manipulated variable detector (potentiometer) 6 was also used for controlling the rotation speed, but a separate manipulated variable detector was used for controlling the rotation speed. It may be provided.

Furthermore, in the above embodiment, two rotation speed setting devices were provided, and the rotation speed was switched to the respective setting value by distinguishing between load driving (during work) and no load (during non-work). It is also possible to control the rotation speed by providing three or more setting devices and switching these rotation speed setting devices according to the load.

As explained above in detail, the present invention electrically detects the error between the rotation speed of the internal combustion engine and the set rotation speed set by the rotation speed setting device, and adjusts the engine rotation speed according to this error. In an apparatus equipped with an operation means for operating an element, a plurality of the rotation speed setters for setting a rotation value according to the load are provided, and an error between the operation amount of the engine rotation speed adjustment element and the set value of this operation amount is corrected. Since the engine speed is controlled by selecting one of the plurality of rotation speed setting devices according to the error, there is no need to repeatedly manually operate the rotation speed setting device, etc. The engine speed is automatically switched to a set value according to the load, which has the excellent effect of reducing engine fuel consumption and noise generation during no-load conditions.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the overall general configuration of an embodiment of the present invention, FIG. 2 is a partial sectional view showing the configuration of mechanical elements in FIG. 1, and FIG. 3 is the electrical circuit configuration in FIG. 1. 4 and 5 are characteristic diagrams for explaining the operation of the present invention. 1...Control circuit, 2...Fluid servo motor serving as an operating means, 3...Throttle valve serving as a rotational speed adjustment element, 4...Gasoline engine with magneto ignition system forming an internal combustion engine, 5...Ignition/charging serving as a rotational speed detector Power supply coil, 6... manipulated variable detector, 7... set rotation speed selection circuit, 9, 10... first rotation speed setter, second
11...operation amount setting device, 12...error discriminator, 13...setting device selection circuit.

Claims (1)

[Claims] 1. A device that electrically detects an error between the rotational speed of an internal combustion engine and a set rotational speed set by a rotational speed setting device, and includes an operating means for operating a rotational speed adjustment element of the engine according to this error, A plurality of the rotation speed setters are provided to set a rotation value according to the load, and a manipulation amount detector detects the operation amount of the rotation speed adjustment element, and an operation amount setting that determines the set value of the operation amount. an error discriminator that discriminates the error between the detection signal from the manipulated variable detector and the set value from the manipulated variable setter, and the plurality of rotation speed settings according to the error signal from the error discriminator. 1. A rotation speed control device for an internal combustion engine, comprising a set rotation speed selection circuit having a setting device selection circuit for selecting one rotation speed setting device from among the rotation speed setting devices.