JPH059636B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an internal combustion engine protection device that protects an internal combustion engine that drives a vehicle such as a vehicle or a ship when an abnormality occurs in the engine.

[Prior Art] When the oil pressure of an internal combustion engine drops abnormally or the coolant temperature rises abnormally, if the engine is continued to operate, there is a risk that the engine will be damaged. Therefore,
An internal combustion engine protection device has been proposed that limits the rotational speed of the engine by causing the engine to misfire when an abnormality occurs in the engine.

[Problem to be solved by the invention] Conventional internal combustion engine protection devices that limit the rotational speed of the engine when an abnormality occurs cause the engine to completely misfire when an abnormality occurs. , When an abnormality occurs, the vehicle suddenly decelerates, which not only gives the driver an unpleasant feeling, but also
In some cases, this may upset the driver and cause an accident.

SUMMARY OF THE INVENTION An object of the present invention is to provide an internal combustion engine protection device with a simple structure that can limit the rotational speed without causing discomfort to the driver when an abnormality occurs in the engine.

[Means for Solving the Problems] The present invention provides a sensor that detects an abnormality in an internal combustion engine, an abnormality detection circuit that outputs an abnormality detection signal when a signal indicating an abnormality in the internal combustion engine is given from the sensor, and a sensor that detects an abnormality in an internal combustion engine. An internal combustion engine protection device comprising: an ignition control circuit that receives the output of the abnormality detection circuit as an input and controls an ignition device for the internal combustion engine to limit the rotational speed of the internal combustion engine to a limit value or less when an abnormality detection signal is generated. It is related.

In the present invention, the ignition control circuit includes an integral capacitor that is charged at a constant time constant by a DC power source, and a primary coil of an ignition coil of an ignition device for an internal combustion engine that is connected through a resistor to the primary coil of the ignition coil. A diode through which a limited forward current flows when a voltage is induced in the coil, a reset transistor switch provided to conduct when a base current is applied by a DC power supply to discharge the integrating capacitor, and a DC power supply. The diode is provided with a base current so that it conducts and bypasses the base current of the reset transistor switch from the transistor switch, and when a forward voltage drop occurs across the diode, the forward voltage drop causes A cutoff control transistor switch is controlled by the voltage across the diode so that the base and emitter are reverse biased and cut off, and when an abnormality detection signal is generated, conduction occurs to control the ignition of the internal combustion engine ignition system. A misfire control switch provided to stop the misfire, and a terminal voltage of an integrating capacitor are compared with a reference voltage, and when the terminal voltage of the integrating capacitor exceeds the reference voltage, the misfire control switch is prevented from conducting. The comparator controls the misfire control switch to allow the misfire control switch to conduct when the terminal voltage of the integrating capacitor is below the reference voltage.

In addition, in the present invention, when the engine rotational speed is below the limit value, the terminal voltage of the integrating capacitor exceeds the reference voltage at a position where the phase is ahead of the engine ignition position, and the engine rotational speed exceeds the limit value. Sometimes, the charging time constant of the integrating capacitor is set so that the terminal voltage of the integrating capacitor exceeds the reference voltage at a position later than the ignition position.

[Function] In the above protection device, the integral capacitor is reset every time a voltage is induced in the primary coil of the ignition coil at the ignition position of the engine. , resulting in a triangular waveform voltage that returns to zero at each ignition position. The magnitude of the terminal voltage of the integrating capacitor changes depending on the length of time for charging the integrating capacitor. When the rotational speed of the engine is low, the time to charge the integrating capacitor is long enough, so the voltage at the terminals of the integrating capacitor becomes high. The voltage is getting lower. In the present invention, when the engine rotational speed is below the limit value, the terminal voltage of the integrating capacitor exceeds the reference voltage at a position where the phase is more advanced than the engine ignition position, and when the engine rotational speed exceeds the limit value, the terminal voltage of the integral capacitor exceeds the reference voltage. The charging time constant of the integrating capacitor is set so that the terminal voltage of the integrating capacitor exceeds the reference voltage at a position later than the ignition position.

Therefore, when an abnormality occurs in the engine oil pressure, cooling water temperature, etc. and the abnormality detection circuit outputs an abnormality detection signal, if the rotational speed of the internal combustion engine is below a predetermined limit value, the ignition position of the internal combustion engine Since the terminal voltage of the integrating capacitor exceeds the reference voltage at a position where the phase is advanced, the comparator prevents the misfire control switch from conducting. At this time, the engine is ignited normally.

If the engine rotational speed exceeds the limit value when the abnormality detection signal is generated, the terminal voltage of the integral capacitor is still below the reference voltage at the engine ignition position, so the comparator activates the misfire control switch. Allows conduction and prevents ignition sparks from occurring.

When the engine misfires (no induced voltage is generated in the primary coil of the ignition coil), the integrating capacitor is no longer discharged, so the terminal voltage of the integrating capacitor continues to rise. When the terminal voltage of the integrating capacitor exceeds the reference voltage, the ignition operation is performed again.

Since the charging time constant of the integrating capacitor is constant, the time required for the terminal voltage of the integrating capacitor to exceed the reference voltage increases as the engine rotation speed increases, and the time required for the terminal voltage of the integrating capacitor to exceed the reference voltage The number of ignition sparks that are blocked during this period increases as the engine rotational speed increases when the abnormality occurs.

In this way, in the present invention, many sparks are thinned out when the rotational speed when an abnormality occurs greatly exceeds the limit value, and the number of sparks to be thinned out is reduced when the rotational speed does not significantly exceed the limit value. Therefore, it is possible to prevent the engine from suddenly decelerating due to excessive control of the rotational speed when the engine is abnormal, and it is possible to prevent the driver from feeling uncomfortable.

Further, in the above configuration, since information regarding the rotational speed of the engine and information regarding the misfire state of the engine are obtained from the voltage induced in the primary coil of the ignition coil, the circuit configuration can be simplified.

Furthermore, with the above configuration, one of the ignition coils
Since it is sufficient to control the cut-off control transistor switch by passing a minute current through the diode using the induced voltage of the secondary coil, the current supplied from the primary coil of the ignition coil to the ignition control circuit only needs to be very small. Therefore, the ignition energy lost by operating the ignition control circuit is extremely small, and the engine can be protected without deteriorating ignition performance.

[Examples] Examples of the present invention will be described below with reference to the accompanying drawings.

(A) Overall configuration of the embodiment Fig. 1 shows the overall configuration of the embodiment of the present invention. In the figure, 1 detects that the internal combustion engine has started and outputs a start detection signal Vst. A start detection circuit 2 receives the output of the start detection circuit 1 and outputs a start display signal Vsd for a certain period of time after the start detection signal Vst is generated.
3 is a delay circuit that outputs a sensor output acceptance permission signal Vrp when a certain period of time has elapsed since the start detection signal Vst is generated, and 3 is a sensor 4 that detects the sensor output acceptance permission signal Vrp and an abnormality in the internal combustion engine. 5 is an abnormality detection circuit which receives the output of the abnormality detection circuit 3 and outputs an abnormality detection signal Va when the sensor output acceptance permission signal Vrp and the sensor output Vas indicating an engine abnormality are generated simultaneously; Abnormality detection signal Va as input
This is an ignition control circuit that thins out the ignition sparks of the internal combustion engine by controlling the internal combustion engine ignition device 6 to limit the rotational speed of the internal combustion engine to a limit value or less when the internal combustion engine is output. In addition, 7 is an abnormality display circuit, which includes a start display signal Vsd and an abnormality detection signal Va.
When the start display signal Vsd is generated, it is displayed that the start of the engine is not completed, and when the abnormality detection signal Va is generated, the occurrence of an abnormal state is displayed.

(B) Specific configuration of the embodiment Referring to FIG. 2, a specific configuration example of each part of FIG. 1 is shown. The configuration of each part will be explained in sections below.

(a) Configuration of the ignition device 6 for an internal combustion engine The ignition device 6 for an internal combustion engine has a primary coil W1.
and an ignition coil IG with one end of the secondary coil W2 grounded, a capacitor C1 with one end connected to the non-ground terminal of the primary coil W1, and a cathode directed toward the ground between the other end of the capacitor C1 and the ground. thyristor S1 connected to
an exciter coil Le whose one end is grounded;
The other end of the exciter coil Le and the capacitor C
a diode D1 connected between the other end of the diode D1 and the other end of the diode D1 with the anode facing the exciter coil side;
A diode D2 connected to both ends of the primary coil W1 with its cathode facing the ground side, a signal coil Ls with one end grounded, and a signal coil Ls.
It consists of a diode D3 connected between the other end and the gate of the thyristor S1 with its anode facing the signal coil Ls side, and a spark plug P connected to the secondary coil W2 of the ignition coil.

This ignition device is a known capacitor discharge type device, and the exciter coil Le is placed in a magnet generator (not shown) driven by the engine, and induces an alternating current voltage in synchronization with the rotation of the engine. Further, the signal coil Ls is arranged in a signal generator (not shown) and outputs a signal voltage V1 as shown in FIG. 3A, and at the engine ignition position, an ignition signal V2 is sent to the thyristor S1 through a diode D3 (see FIG. 3E). ).

When the exciter coil Le generates an output voltage of one half cycle in the direction of the arrow shown in the figure (hereinafter referred to as positive direction output voltage), the diode D
1 and the primary coil W1 of the ignition coil, the capacitor C1 is charged to the polarity shown, and the terminal voltage V3 of the capacitor C1 rises as shown in FIG. 3F. When the signal coil Ls supplies an ignition signal to the thyristor S1 at the ignition position of the engine, the thyristor S1 becomes conductive and the charge of the capacitor C1 is discharged through the thyristor S1 to the primary coil of the ignition coil IG. This discharge causes a large magnetic flux change in the iron core of the ignition coil, and a high voltage is induced in the secondary coil W2 of the ignition coil. This high voltage is the spark plug P
A spark is generated at the spark plug, and the engine is ignited. The waveform of the voltage V4 induced in the primary coil W1 during the ignition operation is shown in FIG. 3G.

(b) Configuration of start detection circuit 1 The start detection circuit 1 includes a diode D4 whose anode is connected to the non-grounded terminal of the exciter coil Le, one end of which is connected to the cathode of the diode D4 through a resistor R1, and the other end of which is grounded. It consists of a capacitor C2 and a Zener diode Z1 connected to both ends of the capacitor C2 with anodes facing the ground side. In this start detection circuit, when the internal combustion engine starts, the capacitor C2 is charged to the Zener voltage of the Zener diode Z1 with the polarity shown through the diode D4 and the resistor R1 by the positive output voltage of the exciter coil Le, and the capacitor C2 is charged to the Zener voltage of the Zener diode Z1. voltage is the start detection signal
Output as Vst.

(c) Configuration of delay circuit 2 The delay circuit 2 consists of comparator CM1 and comparator CM.
A resistor R2 is connected between the positive phase input terminal of the comparator CM1 and the non-ground terminal of the capacitor C1, a capacitor C3 is connected between the positive phase input terminal of the comparator CM1 and the ground, and an anode is connected between both ends of the resistor R2. a diode D5 connected to face the comparator side, a resistor R3 having one end connected to the negative phase input terminal of the comparator CM1, and a resistor R4 connected between the negative phase input terminal of the comparator and ground; It consists of a transistor TR1 whose base is connected to the output terminal of the comparator CM1 via a resistor R5, and a resistor R6 connected between the base and emitter of the transistor TR1, and a resistor R3.
The other end is connected to a non-grounded output terminal E of a constant voltage and current power supply (not shown).

When the engine starts and capacitor C2 is charged to the polarity shown, the voltage across capacitor C2 is transferred to capacitor C3 via resistor R2.
, the capacitor C3 is charged with a constant time constant. first capacitor C3
Since the terminal voltage of is less than the reference voltage obtained across the resistor R4, the potential of the output terminal of the comparator CM1 is at a low level (ground level), and at this time, the transistor TR1 is in a conductive state. When the terminal voltage of the capacitor C3 exceeds the reference voltage across the resistor R4 after a certain period of time has passed after the engine is started, the potential of the output terminal of the comparator CM1 becomes a high level (non-grounded level). When the potential at the output terminal of the comparator CM1 becomes high level, the transistor TR1 is cut off, and the emitter-collector voltage of the transistor TR1 increases. In this example,
The start display signal Vsd is output while the potential of the output terminal of the comparator CM1 is at a low level, and the sensor output acceptance permission signal Vrp is output when the transistor TR1 is cut off.

(d) Configuration of abnormality detection circuit 3 The abnormality detection circuit 3 includes a programmable unidirectional transistor P1 (hereinafter referred to as PUT) whose anode is connected to the non-grounded output terminal of a DC power supply (not shown), and a gate anode of this PUT. A resistor R7 connected between
Resistor R8 whose one end is connected to the gate of PUT
A sensor 4 for detecting an abnormality in the internal combustion engine is connected between the other end of the resistor R8 and ground. Further, the emitter and collector of the transistor TR1 of the delay circuit 2 are connected to both ends of the resistor R7, respectively, so that PUT can be triggered when the transistor TR1 is in a cut-off state. The sensor 4 of this embodiment consists of a switch that closes when an abnormality in the engine is detected.
This sensor becomes conductive when, for example, the oil pressure of the engine drops abnormally. If it is necessary to detect a plurality of abnormalities, such as when detecting an abnormality in the cooling water temperature in addition to an abnormality in the oil pressure, the switches of the plurality of sensors may be connected in parallel.

In the abnormality detection circuit 3, when the switch of the sensor 4 is open, no trigger signal is applied to the PUT, so the PUT is in a cutoff state. When an abnormality occurs in the engine and the switch of sensor 4 is closed, the power supply voltage is applied to the series circuit of resistors R7 and R8. When the switch of the sensor 4 is not completed), the transistor TR1 becomes conductive at the same time as the switch of the sensor 4 is closed (the sensor output acceptance permission signal is not given), so both ends of the resistor R7 of the abnormality detection circuit 3 are
TR1 effectively creates a short circuit and PUT is not triggered. When the transistor TR1 is cut off after a predetermined period of time has passed after the engine has started (starting of the engine has been completed), a trigger signal can be given to PUT, and at this time the switch of sensor 4 is closed. , PUT is triggered into conduction. An abnormality detection signal is output due to the conduction of this PUT. Since PUT has a self-holding function, once it becomes conductive, it will remain conductive as long as a predetermined holding current is supplied even if the switch of sensor 4 is opened.

Among the sensors that detect an abnormality in an engine, some, such as a sensor that detects oil pressure, temporarily perform an abnormality detection operation when the engine is started even if the engine is normal. If such a sensor is provided and an abnormality detection signal is output immediately when the sensor performs an abnormality detection operation, the protection device will malfunction. In order to prevent such malfunctions, in this embodiment, a start detection circuit 1 and a delay circuit 2 are provided before the abnormality detection circuit 3, so that the sensor 4 is activated for a certain period of time after the engine starts. Even if an abnormality in the engine is detected, no abnormality detection signal is output.

(E) Configuration of the ignition control circuit 5 The ignition control circuit 5 includes a comparator CM2,
A positive phase input terminal of the comparator CM2 is connected to a non-grounded output terminal of a DC constant voltage power supply (not shown) via a resistor R9. A resistor R10 is connected between the positive phase input terminal of the comparator CM2 and ground, and the reference voltage obtained across the resistor R10 is input to the positive phase input terminal of the comparator CM2. The collector of an NPN transistor TR2 whose emitter is grounded is connected to the negative phase input terminal of the comparator CM2, and an integrating capacitor C4 is connected between the collector and emitter of the transistor TR2.

The collector of an NPN transistor TR3 whose emitter is grounded is connected to the base of the transistor TR2, and the collector of the transistor TR2 and the collector of the transistor TR3 are connected to the non-grounded output terminal of a DC power supply (not shown) via resistors R10 and R11, respectively. There is. The base of transistor TR3 is resistor R1
A diode D6 with its anode facing the ground side is connected in parallel between the base and ground of the transistor TR3. The base of the transistor TR3 is also connected via a resistor R13 to the cathode of the Zener diode Z2.
The anode of No. 2 is connected to the anode of a diode D7 whose cathode is connected to the non-grounded terminal of the primary coil of the ignition coil. comparator
The output terminal of CM1 is connected to PUT via resistor R14.
A resistor R15 is connected between the base and emitter of the transistor TR4. The collector of the transistor TR4 is connected to the gate of the thyristor S1 of the ignition device and the comparator
CM2, transistors TR2 to TR4, resistors R9 to R15, integrating capacitor C4,
The ignition control circuit 5 is constituted by the diodes D6, D7 and the Zener diode Z2.

In the above ignition control circuit, the transistor TR2 constitutes a reset transistor switch, and the transistor TR3 constitutes a cut-off control transistor switch. Further, the transistor TR4 constitutes a misfire control switch.

In addition, in the above ignition control circuit, when the engine rotation speed is below the limit value, the terminal voltage of the integral capacitor exceeds the reference voltage at a position that is ahead of the engine ignition position in phase, and the engine rotation speed increases to the limit value. When the voltage exceeds the reference voltage, the integrating capacitor C4 is set so that the terminal voltage of the integrating capacitor exceeds the reference voltage at a position delayed from the ignition position.
The charging time constant is set.

In the above ignition control circuit, the ignition coil
When voltage V4 is not induced in the primary coil W1 of IG, transistor TR3 is in a conductive state and transistor TR2 is in a cut-off state. At this time, the integrating capacitor C4 is charged to the polarity shown through the resistor R10 by a DC power supply (not shown). When voltage V4 is induced in the primary coil W1 of the ignition coil, the primary coil W
A pulse-like current flows in the path of 1→diode D6→resistance R13→Zener diode Z2→diode D7→primary coil W1, and the base-emitter of transistor TR3 is reverse biased due to the forward voltage drop across diode D6. This allows the transistor TR
3 is cut off for a short time, and the transistor
TR2 becomes conductive. transistor tr
When transistor TR2 becomes conductive, the charge in the integrating capacitor C4 is discharged through the collector-emitter of the transistor TR2, and the charge in the integrating capacitor C4 becomes zero. Therefore, the waveform of the terminal voltage V6 of the integrating capacitor C4 has a sawtooth shape as shown in FIG. 3B.

In the present invention, the induced voltage from the primary coil of the ignition coil causes a current to flow through the diode D6, and the forward voltage drop of the diode causes the transistor TR3 to be cut off.
Make the resistance value of transistor TR
If the base current of transistor TR3 is limited, the reverse bias voltage applied between the base and emitter of transistor TR3 in order to cut it off can be an extremely low voltage. Therefore, the current flowing from the primary coil of the ignition coil to the diode D6 only needs to be small, and
The energy supplied from the ignition coil to shut off TR3 only needs to be small, so it does not affect ignition performance.

When the rotational speed of the engine is less than the limit value, the time from each ignition position to the next ignition position (ignition interval) is long, and during this ignition interval capacitor C4 is charged to the reference voltage V5 or higher across resistor R10. Therefore, at each ignition position, the terminal voltage V6 of the integrating capacitor C4 is equal to the reference voltage V.
It's over 5. At this time, the output terminal of comparator CM2 is in a grounded state, and transistor TR4
The base of is held at ground potential. Therefore, in this state, regardless of whether PUT of the abnormality detection circuit 3 is conducting or not (regardless of the presence or absence of the abnormality detection signal), the transistor TR
4 is in the cut-off state, and the ignition operation is performed without any problem.

When the rotational speed of the engine exceeds the limit value and the ignition interval falls below the predetermined value, the period during which the integral capacitor C4 is charged becomes shorter, and the terminal voltage V6 of the integral capacitor C4 at the ignition position decreases.
becomes below the reference voltage V5. In this state, the output terminal of comparator CM2 is ungrounded, and the transistor
A base current can be applied to TR4. If PUT of the abnormality detection circuit 3 is conductive in this state (an abnormality detection signal is output), a base current is applied to the transistor TR4, and the transistor TR4 becomes conductive. When the transistor TR4 becomes conductive, the ignition signal voltage V2 supplied from the signal coil Ls of the ignition device to the thyristor S1 is applied to the transistor
Since it is shorted by TR4, thyristor S
The ignition signal is no longer supplied to 1, and the ignition operation is no longer performed. In this way, when the engine speed exceeds the limit value while the abnormality detection signal is being output, the ignition operation is blocked.
The engine misfires. When the engine misfires, the induced voltage V4 in the primary coil W1 of the ignition coil is not generated, so the transistor TR3 remains conductive and the transistor TR2 remains cut off. Therefore, the terminal voltage V6 of the integrating capacitor C4 continues to rise. When the terminal voltage of the integrating capacitor exceeds the reference voltage, the comparator CM
Since the output terminal of PUT 2 becomes the ground potential, conduction of the transistor TR4 is blocked, and even if PUT is conductive and an abnormality detection signal is output, the transistor TR4 is maintained in a cut-off state. Therefore, when an ignition signal is given to the thyristor S1 from the signal coil Ls, an ignition operation is performed.

Since the charging time constant of the integrating capacitor C4 is constant, the time required for the terminal voltage V6 of the integrating capacitor to exceed the reference voltage V5 increases as the engine rotation speed increases.
The terminal voltage V6 of the integrating capacitor is the reference voltage V
The number of ignition sparks that are blocked until the number of sparks exceeds 5 increases as the rotational speed of the engine increases when the abnormality occurs.

Therefore, in the present invention, it is possible to thin out many sparks when the rotational speed when an abnormality occurs greatly exceeds the limit value, and reduce the number of sparks to be thinned out when the rotational speed does not significantly exceed the limit value. This prevents the control that limits the rotational speed from becoming overcontrolled when an engine abnormality occurs.

When the PUT of the abnormality detection circuit 3 is cut off (when the abnormality detection signal is not output),
Regardless of the state of the output of the comparator CM2, no base current is supplied to the transistor TR4, and the transistor TR4 is in a cut-off state. Therefore, the transistor TR4 is the ignition device 6
The ignition operation is performed normally without any effect on the

(F) Configuration of abnormality display circuit 7 The abnormality display circuit 7 is a PNP transistor TR5.
, diodes D8 and D9, and resistor R16
to R18, and a light emitting diode LED as a light emitting display means. The base of the transistor TR5 is connected to the output terminal of the comparator CM1 of the delay circuit 2 through a resistor R16, and a resistor R17 is connected between the emitter and base of the transistor TR5. The collector of transistor TR5 is connected to the anode of diode D8, and the cathode of diode D8 is a light emitting diode whose cathode is grounded.
It is connected to the anode of the LED through a resistor R18. The cathode of the diode D8 is connected to the cathode of a diode D9 whose anode is connected to the cathode of PUT, and the emitter of the transistor TR5 is connected to the non-grounded output terminal of a DC power supply (not shown).

In this abnormality display circuit, transistor TR5, resistors R16, R17, and diodes D8, D9 constitute an OR circuit, and when the output terminal of comparator CM1 of delay circuit 2 is in the grounded state (display permission command signal is being output) and when PUT of the abnormality detection circuit 3 is conducting (when the abnormality detection signal is being output), the light emitting diode LED emits light. In other words, the light emitting diode LED will emit light for a certain period of time until the engine has finished starting, indicating that the engine has not started, and while the engine is running, PUT will be conductive and an abnormality detection signal will be output. When this occurs, the light emitting diode (IED) will emit light to indicate that an abnormality has occurred.

(g) Operation of the embodiment shown in Figure 2 In the above embodiment, when the engine starts,
A capacitor C2 is charged from the exciter coil Le through a diode D4 and a resistor R1, and a start detection signal is obtained across the capacitor C2. When this start detection signal is generated, the capacitor C3 is charged to the polarity shown in the figure through the resistor R2, and the terminal voltage of the capacitor C2 increases. After the engine has been started, the voltage at the terminals of capacitor C3 remains at resistor R4 until a certain period of time set long enough to complete engine starting has elapsed.
Since the reference voltage across both ends of the voltage is lower than the reference voltage, the output terminal of the comparator CM1 is grounded, and the transistor TR1 of the abnormality detection circuit is conductive. Therefore, the abnormality detection circuit 3
PUT is not triggered and no abnormality detection signal is output. Also, at this time, the transistor TR5 of the display circuit 7 becomes conductive, so that the light emitting diode LED emits light to indicate that the engine starting operation has not been completed.

Engine starting operation is completed and capacitor C3
When the terminal voltage becomes equal to or higher than the reference voltage across the resistor R4, the output terminal of the comparator CM1 becomes ungrounded, the transistor TR5 becomes cut off, and the light emitting diode LED stops emitting light. This indicates that engine starting has been completed. Also at this time, transistor TR
1 is cut off, the abnormality detection circuit
PUT can now be triggered.

When there is no abnormality in the engine, the switch of sensor 4 is open, so PUT is not triggered.
No abnormality detection signal is output. In this state, regardless of the state of the output of comparator CM2 of the ignition control circuit, transistor TR4
No base current is supplied to the transistor.
TR4 is kept in a blocked state. At this point, in the ignition device, the signal coil Ls is connected to the diode D.
3, the ignition signal V1 is applied to the thyristor S1 without any problem, and the ignition operation is performed without any problem.

On the other hand, if an abnormality occurs in the engine oil pressure or cooling water temperature and the switch of sensor 4 closes, PUT is triggered and conducts, so the corresponding
An abnormality detection signal is output through PUT.
When the engine speed exceeds the limit value while the abnormality detection signal is being output, the output terminal of comparator CM2 becomes ungrounded due to the above operation, transistor TR4 becomes conductive, and thyristor S1 is turned on. Short-circuit between gate and cathode. Therefore, the ignition signal is no longer supplied to the thyristor S1 at the ignition position, the ignition operation is blocked, and the ignition spark is thinned out. The number of sparks thinned out increases as the rotation speed increases when the abnormality occurs. This reduces the rotational speed of the engine. When the rotational speed of the engine becomes less than the limit value, the output terminal of the comparator CM2 of the ignition control circuit is held in a grounded state, and the ignition operation is performed normally. By repeating these operations, the rotational speed of the engine is kept below the limit value. Further, when PUT is conductive and an abnormality detection signal is generated, the light emitting diode LED of the abnormality display circuit 7 emits light to indicate the occurrence of an abnormality.

Note that the limit value of the rotational speed of the engine is set to a sufficiently low value that there is no danger even if the engine continues to rotate to some extent in a state where an abnormality has occurred.

(C) Other embodiments In the above embodiment, the ignition control circuit is provided with an integral capacitor C4 that is charged at a constant time constant, and the sawtooth voltage V6 is obtained by discharging this integral capacitor C4 at the ignition position. However, when an electronic advance type ignition system is used that determines the ignition position by comparing the terminal voltage of the integrating capacitor with a reference voltage, the terminal voltage of the integrating capacitor in the ignition system is set to the voltage of the above embodiment. It can also be used as a V6.

Referring to FIG. 4, a modified example of the abnormality display circuit 7 is shown, and in this example, a light emitting diode is used.
The collector and emitter of a transistor TR5 are connected to both ends of the LED. transistor
A resistor R25 is connected between the base and emitter of the transistor TR5, and a resistor R2 is connected between the base of the transistor TR5 and the cathode of PUT of the abnormality detection circuit 3.
6.

In the display circuit shown in FIG. 4, when no abnormality occurs, the transistor TR5 is in a cut-off state and the light emitting diode LED is lit.
When an abnormality occurs in the engine and PUT becomes conductive, transistor TR5 becomes conductive and the light emitting diode LED
stops emitting light.

Referring to FIG. 5, still another modification of the abnormality display circuit is shown. In the example shown in FIG. 5, a diode D10 with its cathode facing the comparator CM1 is inserted between the resistor R16 connected to the base of the transistor TR5 and the output terminal of the comparator CM1. NPN with emitter grounded to the anode
The collector of transistor TR6 is connected. The base of transistor TR6 is resistor R30
connected to the cathode of PUT through.

In the example shown in Figure 5, when an abnormality occurs in the engine and PUT becomes conductive, the transistor TR
A base current flows through 6, making this transistor conductive. Due to the conduction of the transistor TR6, a base current flows to the transistor TR5, and the transistor TR5 becomes conductive.
The light emitting diode LED emits light due to the conduction of 5.

As shown in Figure 2, when the light emitting diode LED is directly driven by the PUT, depending on the wiring route of the light emitting diode LED, the PUT may malfunction due to noise induced in the wiring to the light emitting diode. There is a risk.
On the other hand, as shown in FIG. 5, transistor TR6 is connected between PUT and transistor TR5.
By separating the PUT and the light-emitting diode LED, it is possible to prevent the PUT from malfunctioning due to noise.

In each of the above embodiments, a light emitting diode
The LED both indicates that engine starting has not been completed and indicates that an abnormal condition has occurred, but it is also possible to configure the system so that both indications are displayed by separate display means.

Note that the display means is not limited to the light emitting display means, and a sounding body such as a buzzer can also be used as the display means.

In each of the embodiments described above, a start detection circuit and a delay circuit are provided, but if the oil pressure of the engine is not detected, these start detection circuit and delay circuit can be omitted.

[Effects of the Invention] As described above, according to the present invention, when the rotational speed significantly exceeds the limit value when an abnormality occurs, many sparks are thinned out, and the rotational speed does not exceed the limit value by much. By reducing the number of sparks that are sometimes thinned out, it is possible to prevent the control that limits the rotational speed from becoming overcontrolled when an engine abnormality occurs and causing the engine to suddenly decelerate, thereby preventing unpleasant sensations from being given to the driver. There is an advantage that it can be done.

Further, according to the present invention, information regarding the rotational speed of the engine and information regarding the misfire state of the engine are obtained from the voltage induced in the primary coil of the ignition coil, so the circuit configuration can be simplified.

Further, in the present invention, since the cutoff control transistor switch can be controlled by the induced voltage of the primary coil of the ignition coil, only a small amount of current is required to be supplied from the primary coil of the ignition coil to the ignition control circuit. Therefore, the ignition energy lost by operating the ignition control circuit using the induced voltage of the primary coil of the ignition coil is extremely small, and the engine can be protected without deteriorating the ignition performance.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the overall configuration of an embodiment of the present invention, Fig. 2 is a circuit diagram showing an embodiment in which each part of Fig. 1 is concretely shown, and Fig. 3 is a block diagram showing each part of Fig. 1. 4 and 5 are circuit diagrams showing different modifications of the display circuit used in the present invention, respectively. 1...Start detection circuit, 2...Delay circuit, 3...
Abnormality detection circuit, 4...Sensor, 5...Ignition control circuit, 6...Ignition device, IG...Ignition coil, D6
...Diode, TR2...Transistor (transistor switch for reset), TR3...Transistor (transistor switch for cut-off control),
TR4...transistor (misfire control switch),
CM2... Comparator.

Claims (1)

[Scope of Claims] 1. A sensor that detects an abnormality in an internal combustion engine, and an abnormality detection circuit that outputs an abnormality detection signal when a signal indicating an abnormality in the internal combustion engine is given from the sensor;
an ignition control circuit that receives the output of the abnormality detection circuit as an input and controls an ignition device for the internal combustion engine to limit the rotational speed of the internal combustion engine to a predetermined limit value or less when the abnormality detection signal is generated. In the engine protection device, the ignition control circuit includes: an integral capacitor that is charged at a constant time constant by a DC power supply; and a primary coil of the ignition coil of the ignition system for an internal combustion engine connected through a resistor to a primary coil of the ignition coil.
a diode through which a limited forward current flows when a voltage is induced in the next coil; and a reset transistor switch provided to conduct when a base current is applied by the DC power supply to discharge the integrating capacitor. A base current is applied by the DC power supply to conduct the reset transistor switch so that the base current of the reset transistor switch is bypassed from the transistor switch, and when a forward voltage drop occurs across the diode, the a cut-off control transistor switch controlled by the voltage across the diode so that the base-emitter is reverse-biased due to a directional voltage drop, resulting in a cut-off state; a misfire control switch provided to stop the ignition operation of the ignition device; and a misfire control switch that compares the terminal voltage of the integrating capacitor with a reference voltage and performs the misfire control when the terminal voltage of the integrating capacitor exceeds the reference voltage. a comparator for controlling the misfire control switch so as to prevent the misfire control switch from conducting, and to allow the misfire control switch to conduct when the terminal voltage of the integrating capacitor is below a reference voltage; When the rotation speed is below the limit value, the terminal voltage of the integrating capacitor exceeds the reference voltage at a position where the phase is ahead of the engine's ignition position, and when the engine rotation speed exceeds the limit value, it is at a position where the phase is behind the ignition position. An internal combustion engine protection device characterized in that a charging time constant of the integrating capacitor is set such that a terminal voltage of the integrating capacitor exceeds a reference voltage.