JP2699635B2 - Ignition control device for vehicle driving internal combustion engine - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ignition control device for controlling an ignition device for an internal combustion engine so as to limit the speed of a vehicle driven by the internal combustion engine.

[Prior Art] In order to ensure the safety of a vehicle, an ignition control device is used which suppresses an increase in the rotational speed of the engine by causing the internal combustion engine to misfire when the speed of the vehicle exceeds a set value. I have.

As an ignition control device of this type, a circuit that periodically generates a misfire command signal having a predetermined pulse width during a period in which the vehicle speed exceeds a limit value, and a component of the ignition device for an internal combustion engine that is short-circuited when the circuit is turned on. And a switch for preventing ignition, which is provided so as to prevent the ignition operation and becomes conductive when triggered by a misfire command signal.

In this ignition control device, when the vehicle speed exceeds the limit value, a misfire command signal is periodically generated and the ignition prevention switch is turned on, so that the ignition operation is periodically prevented and the ignition spark of the engine is thinned out. As a result, the rotation speed of the engine decreases, and the vehicle speed decreases. When the vehicle speed falls below the limit value, the misfire command signal disappears, so that the ignition prevention switch does not conduct, and the engine is normally ignited.

[Problems to be Solved by the Invention] In the conventional ignition control device, the timing of detecting the vehicle speed and generating the misfire command signal is not synchronized with the operation of the ignition device. However, it has not been possible to maintain a constant relationship between the timing at which the ignition of the ignition device and the timing of the start of the operation of the ignition device. Therefore, the speed control operation is started before ignition is performed, or the speed control operation is started after ignition is already performed, and the number of times the ignition operation is blocked when each misfire command signal is generated is constant. Otherwise, there was a problem that the control became unstable. For example, in the proposed ignition control device, even if the pulse width of each misfire command signal is set such that the ignition operation is blocked three times each time the misfire command signal is generated, the ignition operation is blocked only twice. In some cases, the vehicle speed control operation could not be performed stably because the vehicle speed was not controlled or was blocked four times.

An object of the present invention is to provide an ignition control device for a vehicle driving internal combustion engine that solves the above-mentioned problem by synchronizing a vehicle speed limiting operation with an ignition operation.

[Means for Solving the Problems] The present invention provides an ignition system for controlling an ignition device for an internal combustion engine that ignites the internal combustion engine using an AC generator driven by the internal combustion engine for driving the vehicle in accordance with the speed of the vehicle. The present invention relates to a control device, and in the present invention, a vehicle speed detection signal generating circuit for outputting a vehicle speed detection signal proportional to the speed of a vehicle driven by an internal combustion engine, and a vehicle speed detection signal by comparing the vehicle speed detection signal with a reference signal. A misfire command signal generation circuit for periodically generating a misfire command signal having a predetermined pulse width when the magnitude of the ignition signal exceeds the magnitude of the reference signal; A switch for preventing ignition that is activated by a misfire command signal and that is turned on when the vehicle speed exceeds a limit value. A synchronization circuit for synchronizing the operation of the misfire command signal generation circuit with the rotation of the internal combustion engine so that the generation of the misfire command signal is started at a specific rotation angle position, and the rotation speed of the internal combustion engine exceeds a set value. And a misfire command signal width adjustment circuit for narrowing the signal width of the misfire command signal when the signal is received.

[Operation] With the above-described configuration, the misfire command signal is generated at a predetermined rotational angle position of the engine each time, so that the position at which the generation of the misfire command signal is started (timing of the start of the speed control operation) is determined. The relationship with the ignition position can always be kept constant, and stable control can be performed.

Further, if the misfire command signal width adjustment circuit for narrowing the signal width of the misfire command signal is provided when the rotation speed of the internal combustion engine exceeds the set value as described above, the thinning is performed when the vehicle speed exceeds the limit value. Because the number of sparks can be prevented from greatly fluctuating depending on the position of the transmission, the number of sparks that are decimated when the vehicle speed exceeds the limit value in a state where the gear ratio is large increases, and the number of sparks increases in the exhaust gas. An increase in the amount of unburned gas contained can be prevented.

Embodiment An embodiment of the present invention will be described below in detail with reference to the accompanying drawings.

The drawings show the overall configuration of an embodiment of the present invention. In the control device of this embodiment, an ignition main circuit 1
An exciter coil 2 provided in a magnet generator driven by an internal combustion engine, an engine rotation speed limiting circuit 3, a vehicle speed detector 4, a vehicle speed detection signal generating circuit 5, a vehicle speed limiting circuit 6, a synchronization circuit 7, And an ignition command signal width adjustment circuit 8. Further, in this embodiment, a battery charging coil 9 provided in the magnet generator, a battery 12 charged by the output of the battery charging coil through the rectifier circuit 10 and the switch 11, and both ends of the battery 12 through the switch 11 And a power supply circuit 13 connected thereto.

In this embodiment, the exciter coil 2 and the power generation coil 9 output an AC voltage in synchronization with the rotation of the engine.

The ignition main circuit 1 is a known capacitor discharge type circuit. In this ignition main circuit, when the exciter coil 2 induces a positive half-cycle voltage in the direction of the solid arrow shown in the drawing, the exciter coil 2 → Primary coil of diode D1 and ignition coil Ig → capacitor C1 → diode
The capacitor C1 is charged to the polarity shown in the path from D2 to the exciter coil 2.

When the exciter coil 2 induces a voltage of a negative half cycle in the direction of the dashed arrow shown in the drawing, the exciter coil 2 →
The capacitors C2 and C3 are charged to the polarity shown in the path of the capacitor C2 and the resistor R1 → the capacitor C3 → the resistor R2 → the diode D3.

When the voltage across the capacitors C2 and C3 exceeds the Zener level of the Zener diode Z1, the capacitors C2 and C3 discharge between the Zener diode Z1 and the gate cathode of the thyristor Th1, and through the resistors R3 and R2, so that the thyristor Th1 conducts. . As a result, the electric charge of the capacitor C3 is discharged between the gate and the cathode of the thyristor Th2, through the thyristor Th1 and the resistor R2, and the thyristor Th2 is triggered. Therefore, the thyristor Th2 conducts, and the electric charge of the capacitor C1 is discharged through the thyristor Th2 and the primary coil of the ignition coil Ig. This discharge causes a large change in magnetic flux in the core of the ignition coil, and a high voltage is induced in the secondary coil of the ignition coil. Since this high voltage is applied to a spark plug P attached to a cylinder of the engine, a spark is generated in the spark plug and the engine is ignited.

In this embodiment, the thyristor Th2 controls the ignition coil 1
A semiconductor switch for controlling the secondary current is formed, and the capacitors C2 and C3, the resistors R2 and R3, the Zener diode Z1, the thyristor Th1 and the diode D3 are used to trigger the primary current control semiconductor switch at the ignition position of the engine. A timing determination circuit is configured.

The engine speed limiting circuit 3 is a first ignition blocking switch 301 using a thyristor Th3 as a switching element.
And a trigger circuit 302 for this switch.

When the exciter coil 2 induces a voltage of a negative half cycle in the direction of the dashed arrow shown in the figure, the exciter coil 2 → the capacitor C4 → the resistor R8 → the diode D4 → the exciter coil 2
The current flows in the path of the capacitor C4, and the capacitor C4 is charged.
A reverse voltage is applied between the gate and the source of the IGBT. Capacitor C4
Discharges through the resistor R9 and the variable resistor VR1.
The peak value of the terminal voltage Vc4 of the capacitor C4 increases as the engine speed increases. When the rotation speed of the engine is lower than the set value, the terminal voltage Vc4 of the capacitor C4 does not reach the cutoff level of the field effect transistor F1, so that
When the exciter coil 2 generates a voltage of a positive half cycle in the direction of the solid arrow shown in the figure, the field effect transistor F1 conducts, and the transistor TR1 passes through the diode D5 and the resistor R10.
And the transistor TR1 is turned on.
Therefore, the voltage between both ends of the resistor R11 is kept below the Zener level of the Zener diode Z2, and no trigger signal is given to the thyristor Th3. Therefore, when the rotation speed of the engine is lower than the set value, the thyristor Th3 does not conduct, and the first ignition blocking switch has no effect on the operation of the ignition main circuit 1.

As the rotation speed of the engine increases, the voltage across the capacitor C4 exceeds the cutoff level of the field effect transistor F1, but the electric charge of the capacitor C4 is reduced by the resistor R9.
When the rotational speed of the engine is equal to or lower than the set value, the output voltage of the positive half cycle of the exciter coil 2 becomes a predetermined level (the voltage across the resistor R11 is changed to the Zener diode Z2). Before reaching the Zener voltage), the voltage across the capacitor C4 drops to a value lower than the cutoff level of the field effect transistor F1.

When the rotation speed of the engine exceeds the set value, the voltage across the capacitor C4 exceeds the cutoff level of the field effect transistor, and the field effect transistor F1 and the transistor TR1
Is interrupted until the output of the positive half cycle of the exciter coil 2 reaches a predetermined level (the time when the voltage across the resistor R11 reaches the Zener level of the Zener diode Z2). , The Zener diode Z2 is turned on to supply a trigger signal to the thyristor Th3 to turn on the thyristor.

When the thyristor Th3 conducts, the thyristor Th3 and the resistance
Since the exciter coil is substantially short-circuited through R12, power (ignition energy) is not supplied to the ignition main circuit 1, and the ignition operation is not performed. Therefore, the engine is misfired and the rotation speed is reduced.

The set value of the rotation speed of the engine is set equal to the allowable rotation speed of the internal combustion engine.

The power supply circuit 13 includes a diode D6, a resistor R14, a power supply capacitor C5 having a sufficiently large capacity, and a zener diode Z3. In this power supply circuit, the capacitor C5 is connected to the output of the battery 12 and the battery charging coil 9
And the voltage across the capacitor is limited to the Zener voltage of the Zener diode Z3.

The vehicle speed detector 4 is composed of a reed switch M arranged close to a magnet mounted on an output shaft of the transmission. This reed switch repeatedly turns on and off at a repetition frequency proportional to the rotation speed of the engine.

The vehicle speed detection signal generation circuit 5 is a frequency voltage conversion circuit including a switch circuit 501 that repeats on / off in response to the on / off of the vehicle speed detector 4, and a pump circuit 502 controlled by the switch circuit.

In this vehicle speed detection signal generation circuit 5, a transistor
TR2 is supplied with a base current from the power supply circuit 13 through the resistors R15 and R15 and becomes conductive. When the reed switch M is turned on, the base current of the transistor TR2 is bypassed from the transistor, so that the transistor TR2 is turned off. When the reed switch M is turned off, the transistor TR2 is turned on. Power supply circuit 13 → resistor R18 → capacitor C when transistor TR2 is off
7 → diode D7 → capacitor C8 and resistor R19 → power supply circuit
A current flows through the path 13 and the capacitor C8 is charged by an amount corresponding to the capacity of the capacitor 7. When the transistor TR2 is turned on, the charge of the capacitor C7 is discharged through the path of the capacitor C7 → the transistor TR2 → the diode D8 → the capacitor C7. The electric charge of the capacitor C8 is discharged through the resistor R19 with a constant time constant. By repeating this operation,
The terminal voltage of the capacitor C8 increases in proportion to the on / off repetition frequency of the speed detector M (in proportion to the vehicle speed). The voltage across capacitor C8 is used as vehicle speed detection signal Vs. This vehicle speed detection signal Vs changes linearly in proportion to the rotation speed of the engine.

The vehicle speed limiting circuit 6 includes a reference signal generating circuit 601 including resistors R20 and R21 and a capacitor C9, a comparator CP1 for comparing the vehicle speed detection signal Vs with a reference signal Vr1 obtained at both ends of the capacitor C9, and a comparison including a resistor R22. A circuit 602, a pulse generation circuit 603, and a second ignition blocking switch 604 are provided.

The pulse generation circuit 603 is a semiconductor integrated circuit IC1 for a timer.
And external resistors R23 and R24 for setting a pulse width and a duty ratio, and a capacitor C10.
When the potential of the first output terminal is at a high level, a misfire command signal Vg composed of a square wave pulse is generated at a predetermined cycle. In this example, the comparison circuit 602 and the pulse generation circuit 603 compare the vehicle speed detection signal Vs with the reference signal Vr1, and when the magnitude of the vehicle speed detection signal exceeds the magnitude of the reference signal, a predetermined pulse width is obtained. A misfire command signal generation circuit for periodically generating a misfire command signal having the same is provided.

The second ignition blocking switch 604 is an exciter coil 2
And a resistor R25 and a capacitor C11 connected in parallel between the gate and cathode of the thyristor, and the output pulse Vg of the pulse generation circuit 603 is passed through the resistor R26 and the diode D8. It is supplied to the Th4 gate.

In the above-described vehicle speed limiting circuit, when the magnitude of the vehicle speed detection signal Vs is equal to or less than the magnitude of the reference signal Vr1, the potential of the output terminal of the comparator CP1 is at a low level. At this time, since the pulse generation circuit 603 does not generate a pulse signal (misfire command signal), the thyristor Th4 constituting the second ignition prevention switch does not conduct. Therefore, the exciter coil 2 is not short-circuited, and the ignition operation is performed without any trouble.

When the magnitude of the vehicle speed detection signal Vs exceeds the magnitude of the reference signal Vr1, the output of the comparator CP1 goes high. Comparator CP1
Becomes high, the pulse generation circuit 603 generates a pulse signal Vg, and the pulse signal is supplied to the gate of the thyristor Th4. As a result, the thyristor Th4 conducts and substantially short-circuits the output of the exciter coil 2 in the positive half cycle. When the output of the positive half cycle of the exciter coil is short-circuited, the capacitor C1 is not charged, so that the ignition operation is not performed and the engine is misfired. The pulse generation circuit 603 generates a pulse signal Vg having a predetermined pulse width at a predetermined cycle while the vehicle speed exceeds the limit value and the magnitude of the vehicle speed detection signal Vs exceeds the magnitude of the reference signal Vr1, and While the pulse signal is being generated, each time the exciter coil 2 generates a positive half-cycle output voltage, the thyristor Th4 is turned on to prevent charging of the capacitor C1 and stop the ignition operation. The number of sparks extinguished when each pulse signal Vg is generated is determined by the pulse width of each pulse signal Vg. During the period from the disappearance of each pulse signal Vg to the generation of the next pulse signal Vg, no trigger signal is given to the thyristor Th4, so that the ignition operation is performed without any trouble.

In this way, when the vehicle speed detection signal Vs exceeds the reference signal Vr1, the ignition spark of the engine is periodically thinned out by a predetermined number, and the rotation speed of the engine is reduced.

The pulse width and the cycle (duty of the pulse signal Vg) of the pulse signal Vg are set to an optimum value for the vehicle speed control by setting the number of the continuously extinguished sparks and the ratio of the number of the extinguished sparks to the number of the generated sparks Is set appropriately.

In this embodiment, an engine speed limit release circuit 15 is provided to inhibit the operation of the engine speed limit circuit 3 when the vehicle speed limit circuit 7 is operating. In this circuit, when the pulse generation circuit 603 generates a pulse signal (misfire command signal) Vg, the capacitor C1 is charged through the resistor R27 and the diode D9. When the terminal voltage of the capacitor C12 reaches the Zener level of the Zener diode Z4, a base current is applied to the transistor TR3, the transistor is turned on, and the resistor R1 of the engine speed control circuit 3 is turned on.
Short both ends of 1. As a result, the voltage across the resistor R11 cannot exceed the Zener level of the Zener diode Z2, and the trigger of the thyristor Th3 is prohibited.

When the vehicle speed detection signal Vs is smaller than the reference signal and the output of the comparator CP1 is in a low level state (ground state), the electric charge of the capacitor C12 is output to the resistor R28, the diode D10, and the output stage of the comparator CP1. Discharge through

In the present invention, the synchronization of synchronizing the operation of the misfire command signal generation circuit with the rotation of the internal combustion engine so that the generation of the misfire command signal is started at a specific rotation angle position of the internal combustion engine when the vehicle speed exceeds the limit value A circuit 7 is provided.

The synchronization circuit 7 of the embodiment includes a transistor TR4, resistors R30 to R33, diodes D11 and D12, and a capacitor C13. In this synchronous circuit, a base current is applied to the transistor TR4 through the diode D11 and the resistor R32 when the exciter coil 2 induces a positive half-cycle voltage, so that the transistor TR4 conducts. As a result, the resistor R30 is connected in parallel to both ends of the resistor R21, and the magnitude of the reference signal Vr1 obtained at both ends of the capacitor C9 decreases. When the output of the positive half cycle of the exciter coil 2 disappears, the transistor TR4 is turned off, the resistor R30 is disconnected, and the magnitude of the reference signal Vr1 obtained at both ends of the capacitor C9 increases.

In this embodiment, the value of the reference signal Vr1 when the transistor TR4 is turned on is set to a value corresponding to the vehicle speed limit value. The value of the reference signal Vr1 when the transistor TR4 is turned off is set to a value sufficiently larger than the value corresponding to the limit value of the vehicle, and when the transistor TR4 is turned off, the vehicle speed detection signal Vs The vehicle speed detection signal Vs is set so as not to exceed the reference signal Vr1 even if it reaches the maximum value that can be considered when there is no vehicle speed limiting circuit.

If the above-described synchronous circuit 7 is provided, the reference signal Vr1 becomes a value corresponding to the vehicle speed limit value when the exciter coil 2 generates a positive half cycle output. At this time, if the speed of the vehicle exceeds the limit value and the vehicle speed detection signal Vs exceeds the reference signal Vr1, the output of the comparator CP1 becomes high level, and the pulse generation circuit 703 generates a pulse signal. At this time, the diode D12 and the resistor R33 are output from the output side of the comparator CP1.
, The base current is supplied to the transistor TR4, so that the transistor TR4 keeps the conductive state, and the transistor TR4 keeps the conductive state even when the exciter coil 2 generates the output of the negative half cycle. Therefore, the reference signal Vr1 is held at a value corresponding to the vehicle speed limit value,
As long as the vehicle speed exceeds the limit value, the output of the comparator CP1 is kept at a high level. At this time, the pulse generation circuit 603
Continuously generates a pulse signal (misfire command signal) Vg.

In the present embodiment, the operation of the vehicle speed limiting circuit 6 is enabled by setting the reference signal Vr1 to a magnitude corresponding to the vehicle speed limiting value when the exciter coil 2 generates a positive half cycle output. However, in the present invention, when the vehicle speed exceeds the limit value, it is sufficient that the generation of the misfire command signal is started at a predetermined rotation angle position of the engine every time, and the positive half cycle of the exciter coil is not necessarily required. It is not necessary to make it possible to generate the misfire command signal from the rising position.

For example, in the above embodiment, a base current is supplied from the battery charging coil 9 to the transistor TR4.
The reference signal Vr may be switched to a value corresponding to the vehicle speed limit value from the rising position of the battery charging coil 9 in the positive half cycle.

As in the above-described embodiment, a pulse generation circuit 703 is provided in the vehicle speed limiting circuit 7 to generate a pulse signal when the vehicle speed exceeds the limit value, thereby periodically turning on the ignition blocking switch, thereby If the rotational speed of the engine is reduced by periodically thinning out the ignition sparks, the amount of unburned gas discharged during the vehicle speed limiting operation can be reduced.

The relationship between the vehicle speed and the rotation speed of the engine differs depending on the position of the transmission. In this case, if the pulse width of the misfire command signal is fixed, the number of sparks to be extinguished differs depending on the position of the transmission, even if the vehicle speed is the same. Therefore, for example, the pulse width of the misfire command signal is set so that the number of sparks to be thinned out when the vehicle speed exceeds the limit value while the transmission is being switched to the fourth speed position is an optimum value. If the vehicle speed exceeds the limit value while the transmission is switched to the third speed position, the number of sparks to be thinned out increases because the engine speed is high even at the same vehicle speed. The amount of combustion gas increases.

In the present embodiment, in order to prevent such inconvenience, a misfire command signal width adjusting circuit 8 that changes the pulse width of the misfire command signal according to the rotation speed of the engine is provided.

In this circuit, a current flows through the diode D15, the resistor R40, and the diode D16 while the exciter coil 2 is generating a negative half-cycle output, and a forward voltage drop of the diode D15 occurs between the base and the emitter of the transistor TR5. Reverse bias. Therefore the transistor
TR5 is kept in the cut-off state, current flows from the power supply circuit 13 through the resistor R41, the capacitor C15, the diode D17, and the capacitor C16, and the capacitor C16 is charged by the capacity of the capacitor C15. The charge of the capacitor C16 is discharged with a constant time constant through the resistor R42. When the exciter coil 2 generates a positive half-cycle voltage, the voltage drop across the diode D15 disappears, so that the transistor TR5 is turned on by the base current supplied from the power supply circuit 13 through the resistor R43. Therefore, the charge of the capacitor C15 is
Discharge through R5 and diode D18. In this way, the capacitor C16 is charged by a predetermined amount each time the exciter coil generates a negative half cycle output, and the resistance R42
Through a constant time constant through the capacitor C16
Voltage rises in proportion to the rotation speed of the engine. Therefore, a speed detection signal Vn proportional to the rotation speed of the engine is obtained at both ends of the capacitor C15. This speed detection signal Vn is a reference signal V obtained at both ends of a capacitor C17 of a reference signal generation circuit including resistors R44 and R45 and a capacitor C17.
The signal is input to the comparator CP2 together with r2 and compared. Here, the reference signal Vr2 is adjusted so as to correspond to a preset rotation speed of the engine. When the engine speed exceeds the set value and the speed detection signal Vn exceeds the reference signal Vr2, the comparator C
Since the potential of the output terminal of P2 becomes the ground potential, a diode
A base current flows through the transistors TR6 and TR7 through D19 and D20, so that both transistors conduct, and the resistors R46 and R47 are connected in parallel to the external resistors R23 and R24 of the timer IC, respectively. Therefore, when the rotation speed of the engine exceeds the set value, the pulse width of the misfire command signal (pulse signal output from the semiconductor integrated circuit IC1 for timer) Vg becomes narrower, and the vehicle speed limiting circuit 6 operates in a state where the rotation speed of the engine is high. The number of sparks decimated when working is limited.

In the above-described embodiment, the ignition operation is performed by connecting the first and second ignition blocking switches 301 and 704 in parallel with the exciter coil and substantially short-circuiting the exciter coil by conducting these switches. However, these switches are connected in parallel with the components of the igniter arrangement so as to substantially prevent short-circuiting of the igniter components when conducting, thereby preventing ignition. It suffices if not limited to the above example. For example, in the above embodiment, the first and second ignition blocking switches may be connected in parallel between the gate and cathode of the thyristor Th2. Further, the first and second ignition blocking switches may be connected in parallel to different components.

In the above embodiment, the reed switch is used as the vehicle speed detector. However, the vehicle speed detector may be any device that generates an electric signal having a frequency proportional to the vehicle speed.

[Effects of the Invention] As described above, according to the present invention, the misfire command signal generation circuit is configured to start generating the misfire command signal at a specific rotational angle position of the internal combustion engine when the vehicle speed exceeds the limit value. Provided a synchronization circuit for synchronizing the operation of the internal combustion engine with the rotation of the internal combustion engine.
The misfire command signal can be generated each time at a fixed rotational angle position of the engine. Therefore, there is an advantage that the relationship between the position where the generation of the misfire command signal starts (timing of the start of the speed control operation) and the ignition position can always be kept constant, and stable control can be performed.

Further, according to the present invention, since the misfire command signal width adjustment circuit for narrowing the signal width of the misfire command signal when the rotation speed of the internal combustion engine exceeds the set value is provided, the time when the vehicle speed exceeds the limit value is provided. It is possible to prevent the number of sparks to be largely fluctuated depending on the position of the transmission, and to increase the number of sparks to be reduced when the vehicle speed exceeds the limit value in a state where the gear ratio is large, so that the number of sparks to be discharged increases. Can be prevented from increasing the amount of unburned gas contained in the gas.

[Brief description of the drawings]

The drawing is a circuit diagram showing an embodiment of the present invention. REFERENCE SIGNS LIST 1 ignition main circuit 2 exciter coil 3 engine speed limiting circuit 4 vehicle speed detector 5 vehicle speed detection signal generating circuit 6 vehicle speed limiting circuit 601 reference signal Generating circuit, 602 ... Comparing circuit, 603 ... Pulse (misfire command signal) generating circuit, 604 ... Switch for preventing ignition, 7 ...
... synchronous circuit, 9 ... battery charging coil, 12 ... battery.

Claims (1)

(57) [Claims] 1. An ignition control device for controlling an ignition device for an internal combustion engine, which ignites the internal combustion engine by using an AC generator driven by an internal combustion engine for driving the vehicle, as a power supply in accordance with the speed of the vehicle. A vehicle speed detection signal generation circuit that outputs a vehicle speed detection signal proportional to the speed of the driven vehicle; and a reference signal whose magnitude corresponds to a vehicle speed limit value by comparing the vehicle speed detection signal with a reference signal. A misfire command signal generation circuit for periodically generating a misfire command signal having a predetermined pulse width when the magnitude of the ignition signal exceeds the magnitude, and when conducting, substantially short-circuits the components of the internal combustion engine ignition device. An ignition prevention switch which is provided so as to stop the operation of the ignition device, and which is turned on by being triggered by the misfire command signal; and a feature of the internal combustion engine when a vehicle speed exceeds a limit value. A synchronizing circuit for synchronizing the operation of the misfire command signal generation circuit with the rotation of the internal combustion engine so that the generation of the misfire command signal is started at a constant rotation angle position, and the rotation speed of the internal combustion engine exceeds a set value. And a misfire command signal width adjustment circuit for narrowing the signal width of the misfire command signal.